零件的三维建模及自动编程(内附中英文翻译)本科论文

目录1 引言 ........................................................................................................ 错误!未定义书签。

2 目前做法 ................................................................................................ 错误!未定义书签。

3 相关工作 ................................................................................................ 错误!未定义书签。

4 游艇的绘制 ............................................................................................ 错误!未定义书签。

5 特点和数据结构 .................................................................................... 错误!未定义书签。

6 成立曲线 ................................................................................................ 错误!未定义书签。

自由曲线 ........................................................................................... 错误!未定义书签。

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外文资料翻译—原文部分Fundamentals of Human Animation(From Peter Ratner.3D Human Modeling and Animation[M].America:Wiley,2003:243~249)If you are reading this part, then you have most likely finished building your human character, created textures for it, set up its skeleton, made morph targets for facial expressions, and arranged lights around the model. You have then arrived at perhaps the most exciting part of 3-D design, which is animating a character. Up to now the work has been somewhat creative, sometimes tedious, and often difficult.It is very gratifying when all your previous efforts start to pay off as you enliven your character. When animating, there is a creative flow that increases gradually over time. You are now at the phase where you become both the actor and the director of a movie or play.Although animation appears to be a more spontaneous act, it is nevertheless just as challenging, if not more so, than all the previous steps that led up to it. Your animations will look pitiful if you do not understand some basic fundamentals and principles. The following pointers are meant to give you some direction. Feel free to experiment with them. Bend and break the rules whenever you think it will improve the animation.SOME ANIMATION POINTERS1. Try isolating parts. Sometimes this is referred to as animating in stages. Rather than trying to move every part of a body at the same time, concentrate on specific areas. Only one section of the body is moved for the duration of the animation. Then returning to the beginning of the timeline, another section is animated. By successively returning to the beginning and animating a different part each time, the entire process is less confusing.2. Put in some lag time. Different parts of the body should not start and stop at the same time. When an arm swings, the lower arm should follow a few frames after that. The hand swings after the lower arm. It is like a chain reaction that works its way through the entire length of the limb.3. Nothing ever comes to a total stop. In life, only machines appear to come to a dead stop. Muscles, tendons, force, and gravity all affect the movement of a human. You can prove this to yourself. Try punching the air with a full extension. Notice that your fist has a bounce at the end. If a part comes to a stop such as a motion hold, keyframe it once and then again after three to eight or more keyframes. Your motion graph will then have a curve between the two identical keyframes. This will make the part appear to bounce rather than come to a dead stop.4. Add facial expressions and finger movements. Your digital human should exhibit signs of life by blinking and breathing. A blink will normally occur every 60 seconds. A typical blink might be as follows:Frame 60: Both eyes are open.Frame 61: The right eye closes halfway.Frame 62: The right eye closes all the way and the left eye closes halfway.Frame 63: The right eye opens halfway and the left eye closes all the way.Frame 64: The right eye opens all the way and left eye opens halfway.Frame 65: The left eye opens all the way.Closing the eyes at slightly different times makes the blink less mechanical.Changing facial expressions could be just using eye movements to indicate thoughts running through your model's head. The hands will appear stiff if you do not add finger movements. Too many students are too lazy to take the time to add facial and hand movements. If you make the extra effort for these details you will find that your animations become much more interesting.5. What is not seen by the camera is unimportant. If an arm goes through a leg but is not seen in the camera view, then do not bother to fix it. If you want a hand to appear close to the body and the camera view makes it seem to be close even though it is not, then why move it any closer? This also applies to sets. There is no need to build an entire house if all the action takes place in the living room. Consider painting backdrops rather than modeling every part of a scene.6. Use a minimum amount of keyframes. Too many keyframes can make the character appear to move in spastic motions. Sharp, cartoonlike movements are created with closely spaced keyframes. Floaty or soft, languid motions are the result of widely spaced keyframes. An animation will often be a mixture of both. Try to look for ways that will abbreviate the motions. You can retain the essential elements of an animation while reducing the amount of keyframes necessary to create a gesture.7.Anchor a part of the body. Unless your character is in the air, it should have some part of itself locked to the ground. This could be a foot, a hand, or both. Whichever portion is on the ground should be held in the same spot for a number of frames. This prevents unwanted sliding motions. When the model shifts its weight, the foot that touches down becomes locked in place. This is especially true with walking motions.There are a number of ways to lock parts of a model to the ground. One method is to use inverse kinematics. The goal object, which could be a null, automatically locks a foot or hand to the bottom surface. Another method is to manually keyframe the part that needs to be motionless in the same spot. The character or its limbs will have to be moved and rotated, so that foot or hand stays in the same place. If you are using forward kinematics, then this could mean keyframing practically every frame until it is time to unlock that foot or hand.8.A character should exhibit weight. One of the most challenging tasks in 3-D animation is to have a digital actor appear to have weight and mass. You can use several techniques to achieve this. Squash and stretch, or weight and recoil, one of the 12 principles of animation discussed in Chapter 12, is an excellent way to give your character weight.By adding a little bounce to your human, he or she will appear to respond to the force of gravity. For example, if your character jumps up and lands, lift the body up a little after it makes contact. For a heavy character, you can do this several times and have it decrease over time. This will make it seem as if the force of the contact causes the body to vibrate a little.Secondary actions, another one of the 12 principles of animation discussed in Chapter 12, are an important way to show the effects of gravity and mass. Using the previous example of a jumping character, when he or she lands, the belly could bounce up and down, the arms could have some spring to them, the head could tilt forward, and so on.Moving or vibrating the object that comes in contact with the traveling entity is another method for showing the force of mass and gravity. A floor could vibrate or a chair that a person sits in respond to the weight by the seat going down and recovering back up a little. Sometimes an animator will shake the camera to indicate the effects of a force.It is important to take into consideration the size and weight of a character. Heavy objects such as an elephant will spend more time on the ground, while a light character like a rabbit will spendmore time in the air. The hopping rabbit hardly shows the effects of gravity and mass.9. Take the time to act out the action. So often, it is too easy to just sit at the computer and try to solve all the problems of animating a human. Put some life into the performance by getting up and acting out the motions. This will make the character's actions more unique and also solve many timing and positioning problems. The best animators are also excellent actors. A mirror is an indispensable tool for the animator. Videotaping yourself can also be a great help.10. Decide whether to use IK, FK, or a blend of both. Forward kinematics and inverse kinematics have their advantages and disadvantages. FK allows full control over the motions of different body parts. A bone can be rotated and moved to the exact degree and location one desires. The disadvantage to using FK is that when your person has to interact within an environment, simple movements become difficult. Anchoring a foot to the ground so it does not move is challenging because whenever you move the body, the feet slide. A hand resting on a desk has the same problem.IK moves the skeleton with goal objects such as a null. Using IK, the task of anchoring feet and hands becomes very simple. The disadvantage to IK is that a great amount of control is packed together into the goal objects. Certain poses become very difficult to achieve.If the upper body does not require any interaction with its environment, then consider a blend of both IK and FK. IK can be set up for the lower half of the body to anchor the feet to the ground, while FK on the upper body allows greater freedom and precision of movements.Every situation involves a different approach. Use your judgment to decide which setup fits the animation most reliably.11. Add dialogue. It has been said that more than 90% of student animations that are submitted to companies lack dialogue. The few that incorporate speech in their animations make their work highly noticeable. If the animation and dialogue are well done, then those few have a greater advantage than their competition. Companies understand that it takes extra effort and skill tocreate animation with dialogue.When you plan your story, think about creating interaction between characters not only on a physical level but through dialogue as well. There are several techniques, discussed in this chapter, that can be used to make dialogue manageable.12. Use the graph editor to clean up your animations. The graph editor is a useful tool that all 3-D animators should become familiar with. It is basically a representation of all the objects, lights, and cameras in your scene. It keeps track of all their activities and properties.A good use of the graph editor is to clean up morph targets after animating facial expressions. If the default incoming curve in your graph editor is set to arcs rather than straight lines, you will most likely find that sometimes splines in the graph editor will curve below a value of zero. This can yield some unpredictable results. The facial morph targets begin to take on negative values that lead to undesirable facial expressions. Whenever you see a curve bend below a value of zero, select the first keyframe point to the right of the arc and set its curve to linear. A more detailed discussion of the graph editor will be found in a later part of this chapter.ANIMATING IN STAGESAll the various components that can be moved on a human model often become confusing if you try to change them at the same time. The performance quickly deteriorates into a mechanical routine if you try to alter all these parts at the same keyframes. Remember, you are trying to create humanqualities, not robotic ones.Isolating areas to be moved means that you can look for the parts of the body that have motion over time and concentrate on just a few of those. For example, the first thing you can move is the body and legs. When you are done moving them around over the entire timeline, then try rotating the spine. You might do this by moving individual spine bones or using an inverse kinematics chain. Now that you have the body moving around and bending, concentrate on the arms. If you are not using an IK chain to move the arms, hands, and fingers, then rotate the bones for the upper and lower arm. Do not forget the wrist. Finger movements can be animated as one of the last parts. Facial expressions can also be animated last.Example movies showing the same character animated in stages can be viewed on the CD-ROM as CD11-1 AnimationStagesMovies. Some sample images from the animations can also be seen in Figure 11-1. The first movie shows movement only in the body and legs. During the second stage, the spine and head were animated. The third time, the arms were moved. Finally, in the fourth and final stage, facial expressions and finger movements were added.Animating in successive passes should simplify the process. Some final stages would be used to clean up or edit the animation.Sometimes the animation switches from one part of the body leading to another. For example, somewhere during the middle of an animation the upper body begins to lead the lower one. In a case like this, you would then switch from animating the lower body first to moving the upper part before the lower one.The order in which one animates can be a matter of personal choice. Some people may prefer to do facial animation first or perhaps they like to move the arms before anything else. Following is a summary of how someone might animate a human.1. First pass: Move the body and legs.2. Second pass: Move or rotate the spinal bones, neck, and head.3. Third pass: Move or rotate the arms and hands.4. Fourth pass: Animate the fingers.5. Fifth pass: Animate the eyes blinking.6. Sixth pass: Animate eye movements.7. Seventh pass: Animate the mouth, eyebrows, nose, jaw, and cheeks (you can break these up into separate passes).Most movement starts at the hips. Athletes often begin with a windup action in the pelvic area that works its way outward to the extreme parts of the body. This whiplike activity can even be observed in just about any mundane act. It is interesting to note that people who study martial arts learn that most of their power comes from the lower torso.Students are often too lazy to make finger movements a part of their animation. There are several methods that can make the process less time consuming.One way is to create morph targets of the finger positions and then use shape shifting to move the various digits. Each finger is positioned in an open and fistlike closed posture. For example, the sections of the index finger are closed, while the others are left in an open, relaxed position for one morph target. The next morph target would have only the ring finger closed while keeping the others open. During the animation, sliders are then used to open and close the fingers and/or thumbs. Another method to create finger movements is to animate them in both closed and open positions and then save the motion files for each digit. Anytime you animate the same character, you can load the motions into your new scene file. It then becomes a simple process of selecting either the closed or the open position for each finger and thumb and keyframing them wherever you desire.DIALOGUEKnowing how to make your humans talk is a crucial part of character animation. Once you add dialogue, you should notice a livelier performance and a greater personality in your character. At first, dialogue may seem too great a challenge to attempt. Actually, if you follow some simple rules, you will find that adding speech to your animations is not as daunting a task as one would think. The following suggestions should help.DIALOGUE ESSENTIALS1. Look in the mirror. Before animating, use a mirror or a reflective surface such as that on a CD to follow lip movements and facial expressions.2. The eyes, mouth, and brows change the most. The parts of the face that contain the greatest amount of muscle groups are the eyes, brows, and mouth. Therefore, these are the areas that change the most when creating expressions.3. The head constantly moves during dialogue. Animate random head movements, no matter how small, during the entire animation. Involuntary motions of the head make a point without having to state it outright. For example, nodding and shaking the head communicate, respectively, positive and negative responses. Leaning the head forward can show anger, while a downward movement communicates sadness. Move the head to accentuate and emphasize certain statements. Listen to thewords that are stressed and add extra head movements to them.4. Communicate emotions. There are six recognizable universal emotions: sadness, anger, joy, fear, disgust, and surprise. Other, more ambiguous states are pain, sleepiness, passion, physical exertion, shyness, embarrassment, worry, disdain, sternness, skepticism, laughter, yelling, vanity, impatience, and awe.5. Use phonemes and visemes. Phonemes are the individual sounds we hear in speech. Rather than trying to spell out a word, recreate the word as a phoneme. For example, the word computer is phonetically spelled "cumpewtrr." Visemes are the mouth shapes and tongue positions employed during speech. It helps tremendously to draw a chart that recreates speech as phonemes combined with mouth shapes (visemes) above or below a timeline with the frames marked and the sound and volume indicated.6. Never animate behind the dialogue. It is better to make the mouth shapes one or two frames before the dialogue.7. Don't overstate. Realistic facial movements are fairly limited. The mouth does not open that much when talking.8. Blinking is always a part of facial animation. It occurs about every two seconds. Different emotional states affect the rate of blinking. Nervousness increases the rate of blinking, while anger decreases it.9. Move the eyes. To make the character appear to be alive, be sure to add eye motions. About 80% of the time is spent watching the eyes and mouth, while about 20% is focused on the hands and body.10. Breathing should be a part of facial animation. Opening the mouth and moving the head back slightly will show an intake of air, while flaring the nostrils and having the head nod forward a little can show exhalation. Breathing movements should be very subtle and hardly noticeable...外文资料翻译—译文部分人体动画基础(引自Peter Ratner.3D Human Modeling and Animation[M].America:Wiley,2003:243~249)如果你读到了这部分，说明你很可能已构建好了人物角色，为它创建了纹理，建立起了人体骨骼，为面部表情制作了morph修改器并在模型周围安排好了灯光。

本科生毕业设计（论文）专业外文翻译原文：Magnesium alloy electric wheel hubmicro-arc oxidation production research译文：镁合金电动车轮毂微弧氧化生产研究指导教师：张清郁职称：讲师学生姓名：陈孟丽学号：1002130301专业：机械设计制造及其自动化院（系）：机电工程学院2015年4月10日Magnesium alloy electric wheel hub micro-arc oxidation production researchMost electric vehicles at home and abr o ad is configured t o aluminum alloy wheel hub,its quality,energy saving,shock absorption,noise reduction and vehicle dynamics characteristics index is much lower than magnesium alloys.Magnesium alloy is30% lighter than aluminum alloy,th e damping effect is30times that of aluminum alloy. Replace the aluminum alloy with magnesium alloy wheel hub,driving the development of magnesium alloy material development and deep processing technology,t o reduce electric vehicle weight and power consumption,energy conservation and environmental protection; T o reduce vibration and noise;Improve ride comfort and electric vehicle dynamic characteristics such as objective(transportation quality each reduce10%,energy consumption will be r educed8%~10%).But its corrosion resistance is poor,seriously limits the monly used chemical oxidation and anode oxidation formation of oxide film on magnesium alloy has certain protective effect,but its corrosion resistance, environmental friendliness,appearance is not satisfactory,be badly in need of the development of new surface treatment.In recent years,people trying to develop a variety of new technologies,such as micro arc oxidation technology,the betterOne Micro-arc oxidation mechanismMicro-arc oxidation technology is a new surface tr eatment technology of gr een environmental protection,can grow in light metal surface in situ ceramic layer directly.Its technological characteristics,surface treatment,as well as the performance of the since the technology was invented by the favour of people,its mechanism is t o light metals such as aluminum,magnesium,titanium and its alloy pu t in electrolyte a q ueous solution as anode, using the method of electrochemical spark discharge spots on the surface of the material, the thermal chemistry,plasma chemistry and electrochemistry,under the joint action of metal oxide ceramic layers of a surface modification technologyTwo research methods and technologyThis topic in the research on magnesium alloy electric wheel hub,higher requirements on the t oughness of the alloy,so choose AM60B,melt and initial temperatur e of468℃,the melting end temperatur e is596℃,the liquidus temperatur e range of 165℃.The chemical composition as shown in table1.T able1AM60B alloy chemical composition(WB/%)Al Zn Mn Si Cu Ni Fe杂质余量5.6～6.4≤0.200.26～0.5≤0.05≤0.008≤0.001≤0.0040.02Mg Because of the magnesium alloy electric wheel hub surface area is larger,generalabove0.4m2,require micro-arc oxidation power supply is bigger,this subject a do pts the lanzhou university of technology institute of materials and development of MAO-300 type nc micro-arc oxidation production device(figure1)micro-arc oxidation on magnesium alloy wheel casting processing,its similar to ordinary anodic oxidation equipment,including special high-voltage power supply,micro-arc oxidation alkaline solution of electrolytic tank,mixing system,cooling system,workpiece with stainless steel plate for peer electrode.With micro-arc oxidation method in sodium silicate and sodium hydroxide electrolyte fluid system in the preparation of magnesium alloy wheel casting oxide ceramic membrane, the concrete technological process first set oxidation process parameters and the alkaline tank sodium silicate solution,the cleaning after micro-arc oxidation of magnesium alloy wheel casting into cell15~20min,clean with clear water tank2~4min,add ho t water in ho t water(80℃,10~15min),closed,then cool in the cold water tank2min,hoisted ou t drainage,drying,examine the hub.After micro-arc oxidation tr eatment must be closed by ho t water,formed by micro-arc oxidation discharge holes so the distribution of the channel and the surrounding a large number of micro cracks will be closed,prevent oxygen t o cause oxidation.After completion of micro-arc oxidation,from after micro-arc oxidation on magnesium alloy wheel casting intercept film sample were analyzed,and to facilitate test analysis,r equest samples made of circular plate,so the sample interception location choice among wheels,mo s t is shown in ing scanning electron microscope analysis of oxide filmFigure1MAO-300type nc micro-arc oxidation power supplyFigure2after micro-arc oxidation magnesium alloy wheel hub casting andinterception of membrane layer analysis sampleThree micro-arc oxidation process parameters on the quality of the film Based on the research of the sample and analysis of micro-arc oxidation technology is, in fact,the substrate magnesium magnesium oxide.Figure3for the dimension of samples before and after oxidation appearance schematic simulation,which is suitable for ceramic oxide film a outward growth,namely the increase of size part,b is the depth of the internal oxidation t o the matrix,a and b interface for initial sample surface position,h for the total thickness of oxide film.Figure3samples dimension changes before and after micro-arc oxidation diagram Larger influence on test has a positive voltage,frequency,duty cycle,current density and oxidation time on the process parameters.Due to the electric casting of magnesium alloy surface area is larger,micro-arc oxidation micro-arc discharge must be formed in the surface can occur after a certain thickness of oxide film,so the formation of the oxide film is needed for the voltage doesn't need much,the current is larger,the oxide film formation and the process of thickening,o ften accompanied by current and voltage mutation.When the oxide film thickness reaches a certain degree,the need t o increase the voltage on both ends of the workpiece,usually at ar ound150V in the micro arc discharge betw een the workpiece and the electrolyte.Increased with the increase of voltage,current,micro-arc density is mo r e and mo r e close,mo r e and mor e bright,and micro-arc constantly beating, basically,the current and voltage,linear increase abo u t180V voltage,the density of micro-arc basically meet the technological requirements,the current growth slowly.When the thickness of oxide film reaches a certain electricityFrom electric casting magnesium alloys is n o t hard t o find in the micro-arc oxidation test result analysis,micro-arc oxidation in the process can be divided into two steps, namely the oxide film formation stage and the stage of micro-arc oxidation film discharge, the formation of oxide film phase as the initial stage,the stage of the supply voltage is small,and after the film to pr oduce micro-arc discharge requires high voltage,for magnesium alloy electric casting the large workpiece with micro-arc oxidation processing surface area is larger,the film for a long time,t o a large extent affected the production efficiency.Experimental results also found that the dc power of oxide film faster than pulse power,in the absence of micro arc discharge,oxide film layer is not dense,it can be seenfrom appearance,need again with pulse power supply for micro-arc oxidation discharge, the oxide film become mo r e dense.In order to improve the production efficiency,to meet the n eed s of industrial production,suggest early low voltage adjustable dc constant voltage power supply are available t o set up the initial oxidation film,forming a complete insulation film in place to ensure that the first phase,and the oxide film in the late discharge can use digital pulse type adjustable power supply,it can shorten the artifacts of micro-arc oxidation time.The size of the current density in a certain extent reflects the intensity of micro-arc oxidation,strongly affect the resulting performance of the micro arc oxidation ceramic layer.The duration of oxidation also seriously affects the coating corrosion resistance: oxidation time is too short,although generat ed mainly the dense layer,bu t the film is too thin,don't have good corrosion resistance;After oxidation time is too long,at some time, with the increase of time,although the overall film thickness increases,bu t the increase is a loose layer,layer density and thinning trend,d o e s n ot favor the coating corrosion resistance,also no t economic.The density of micro arc also related with the pulse frequency,when the pulse frequency increases,the density of micro arc also gradually increased.Will have the electric field set up suddenly,can pr oduce micro arc.In the basic process parameters such as electrolyte concentration,duty ratio and pulse n umbe r of uncertain,the arc voltage is constant commonly,so when the frequency increases,the sustain micro-arc voltage frequency increases,the micro-arc density will increaseFour micro-arc oxide film layer structure characteristicsAfter micro-arc oxidation of magnesium alloy wheel hub interception by Mef3large metallurgical microscope observation of the sample,the micro-arc oxide film surface morphology as shown in figure4.Can be seen from the figure in the wheel hub surface layer is made up of many tiny"small volcanic cone"(figure pr otuberant part ar ound the holes)in dendritic combination,constitute the mesh structure."Small volcanic cone"center has a small hole,this is the electrolyte reaction with matrix micro-arc discharge channel, namely when the micro-arc spew ed molten oxide channel.In addition,because the current micro area local plasma channel is different that differ by the size of the hole,big hole are also distributed ar ound a large n u mbe r of micro cracks,the generation of micro cracks o ften related to the stress that exist in the film.With SSM Analysis Analysis software[6]toanalyze the surface density,including25m film for sample,the hole surface area ratio of 18%,that of micro-arc oxidation film density is better.Figure4magnesium alloy wheel hub micro-arc oxide film layer surface morphologyFigure5AM60B magnesium alloy micro-arc oxidation film section morphology by SEM Figure5is thr ough JMS-6700-f field emission scanning electron microscopy(sem) observed the micro-arc oxide film layer section morphology photos.Figure5shows the average film thickness of a bo u t22(including m,the oxide film and substrate with good, decomposition of a distinct,density on the interface is good,no big holes.By figure5can also see,micro-arc oxide film by the outermost layer of loose layer,the inside of the transition layer and layer in betw een density of three parts,the transitional layer is the interface film layer and substrate,holes and other defects existing in the loose layer,d ens e layer is the key t o improve its corrosion resistance.Figure6is obtained by Phlip X'pert X-ray diffractometer AM60B magnesium alloy wheel hub of micro-arc oxidation film XRD spectrum,according t o the intensity of diffraction peak accumulation analysis shows that the matrix of Mg peak relatively obvious, the main phase of micro-arc oxidation coating is cubic structure of MgO style,surface with Mg2Si2O4and MgAl2O4spinel phase,according t o the test conditions that may also contain SiO2,MgF2and small a mounts of Mg(OH)2,and the oxide of Al,K and Na. Studies have shown that MgAl2O4and Mg2Si2O4can improve the wear resistance of ceramic layer and MgO style the corrosion resistance of ceramic layer play a very important role.This is the micro-arc oxide film performance is higher than the r oot cause of the anode oxidation membrane performance.In addition,micro-arc oxidation ceramic layers of low porosity,and to improve the corrosion resistance of the coatings;Ceramic layer from the substrate on the growth,combined with matrix closely,therefore,is no t easy t o fall off.In addition,the technology can generat e uniform film both inside and outside the material surface layer,expand the scope of application of micro-arc oxidation.Figure6AM60B magnesium alloy micro-arc oxidation film XRD spectrum Five T o detect the corrosion resistance of the micro-arc oxide film layer In order t o meet the requirements of the use of electric cars,micro-arc oxidation on magnesium alloy electric wheel hub on the corrosion resistance test,salt spray testing machine mainly USES the WJ-90after micro-arc oxidation tr eatment of the surface of the wheel hub for salt spray test.After testing found that did not use h ot water seal processing of the surface of the wheel hub48h corrosion rate was0.108%,while only0.073%,afterho t water hole sealing hubs such as chromium than other chemical surface tr eatment processing of low corrosion rate(0.6%).[9],that magnesium alloy after micro-arc oxidation electric wheel hub surface corrosion resistance is superior.T o evaluate a r ough check the appearance of the film,feel is very good,membrane layer uniform light show that membrane surface appearance level is higher.Practice shows that without the micro-arc oxidation of the surface of the magnesium alloy wheel casting coating,its poor corrosion resistance,abrasion resistance,in a very short period of time,began to appear on the surface of parts oxidation falls off ph eno menon,it is difficult t o sell in the market; After micro-arc oxidation treatment,its corrosion resistance,wear-resisting performance is significantSix The conclusion(1)quality of micro-arc oxidation on magnesium alloy electric wheel hub surface influence factor has a positive voltage,frequency,duty cycle,current density and oxidation time on the process parameters.Optimum process parameters for150~180V voltage, current density of1.1A/dm2,oxidation time t o20min,400Hz frequency,duty cycle of 20%.(2)the oxide film is divided into two layers of loose layer and den se layer structure, the dense layer is the main body,the film formed by cubic structure of MgO style,the surface is MgO style and MgA12O4,spinel phase mixture,and combined with matrix and closely for hard ceramic layer and played a key role of the magnesium alloy surface anticorrosion(3)the micro-arc oxidation technology for new surface tr eatment technology of environmental protection,bu t its large area needed for the magnesium alloy casting film for a long time,the production efficiency is low,the mass production t o meet the large area of magnesium alloy castings,micro-arc oxidation power supply can be established by using dc power first initial oxidation film layer,then use pulse power arc discharge strengthening oxide film layer,the ways which are already so den se and har d ceramic oxide film layer can be obtained,also can greatly improve production efficiency.镁合金电动车轮毂微弧氧化生产研究国内外大多数电动车车辆配置为铝合金轮毂，其在质量、节能、减震、降噪和车辆动力学特性等指标大大低于镁合金。

毕业设计（论文）英文资料翻译MECHANISMS AND MACHINETHEORY学院：西北工业大学明德学院专业：飞行器制造工程班级： 164903班姓名：康宇鹏学号： 091773指导老师：侯伟2013年 6 月附录1 外文原文T he different approaches can be classified as the simulation with replaced models and the co-simulation of the dynamic behaviour. The simulation with replaced models uses either analogue models of the control loop for the FEA-Model of the structure or analogue models of the mechanics for the simulation of the control loop [48].In the context of the co-simulation, two independent simulation environments, one for the control loops and one for he machine structure, are coupled via interfaces duringthe simulation [33], [48], [73], [131].Within the research project MECOMAT (FP5 Growth Programme of the European Union) [103] an computer aided engineering tool was developed for the mechatronic design of machine tools, which supports the conceptual design as well as the detailed verification. The different approaches will be explained with some examples within the next sections.2.6.1 Coupled rigid multi-body simulationThe rigid coupled multi-body simulation can be used to simulate the kinematic behaviour of the machine tool while considering the control loops of the drives [20], [76], [125]. The models of the structural components are stiff and cannot deform under load, and are connected by idealised joints. The simulation is valid for any possible position of the machine tool in the workspace. Therefore it is possible to simulate positioning operations in the workspace with this approach.Pritschow et al. [73], [74], [75] developed a simulation environment which is illustrated in Figure 12. The environment was developed for the coupled simulation of a rigid multi-body model and control loop models of a PKM machine tool.Figure 12: Coupled simulation of a rigid multi-body model and control loop models of a PKM machine tool.The multi-body model of the machine tool is imported with the aid of an interface from the CAD-system into the MBS-environment. This approach enables the update of the model during the different design stages; if the layout is detailed during the design process these changes caneasily be included [74].The model is coupled with models of the control loop for each drive. The displacement and velocity of the measuring systems in the model as well as the forces of the drives are exchanged with the aid of interfaces between the MBS-environment and the Computer-Aided-Control- Engineering program. In addition the control loop models are coupled with a PC-based model of the numerical control, which generates the desired feed rate of each individual drive.Especially in the field of machine tools with parallel kinematics the possibility to perform test runs of the numerical control before implementing new functionalities, like algorithms for path preparation, collision checks or coordinate transformations into the real machines is a significant improvement to avoid physical damage [75].Rehsteiner et al. [83] used the multi body simulation to optimise the accuracy of machine tools under acceleration loads for the demands of high-speed-machining.Neugebauer et al. [71] developed models to describe the interaction of machine and hydraulic drive system of forming machines. The methods use numerical simulations for the hydraulic systems.2.6.2 Coupled Finite-Element simulationAnother approach is the coupled Finite-Element simulation with reduced models of the control loops of the drives. Within this procedure the reduced stiffness, damping and mass of the drive system are calculated with the help of a digitalblock-simulation and modelled with special elements in the FEA-model [20], [48], [76], [131].Some FEA-programs provide special linear control elements to represent the analogue model of the control loops. In this case only the settings of the controllers have to be specified as parameters of the elements in the FEAmodel[17]. These kinds of elements are handled in the same way as conventional finite elements.The simulation of the dynamic behaviour of the x-slide of a turning centre with a linear direct drive is depicted in the following Figure 13 [20]. To simulate the error at the toolcentre-point during a positioning, a trajectory profile was generated as an input signal for the controller element. The signal of the measuring system was used as an additional input signal. This signal was measured between two nodes at the two parts to which the measuring system is mounted on the real machine. At each simulationstep of the dynamic analysis the controller element calculated the force of the linear direct drive which was applied as a pair of forces (action=reaction) on the primary and the secondary parts.Figure 13: Coupled FEA-simulation with control loopsThis approach enabled the investigation of the influence of the position of the measuring system as well as different orientations of the linear direct drive. Thus the designer was able to optimise the drive of the x-slide in an early design stage and minimise the occurring errors during machining.Such changes of the principle design would be extremelyexpensive if they had to be realised at a physical prototype,or impossible if the surrounding design space didnot allow such changes.Berkemer [16], [17], [18] demonstrated the industrial use of the methodology for tuning of the SIEMENS controllers in a virtual environment, as well as recommending the modification of the machine tool dimensions to minimize inertial excitation of the machine during high speed contouring where large accelerations occur.Van Brussel et al. [104], [105] proposed to treat the complete machine tool and control as an integrated mechatronics design system. The Finite-Element-Model of the machine tool and control algorithms are integrated in the simulation environment as shown in Figure 14.The aim of the strategy is to optimise the machine tool’s mechanical components as well as the control laws during the design stage of the machine tool simultaneously.Figure 14: Integration of structural and controller modelsZäh et al. [130], [131], [132] developed a Finite-Element- Model of the feed drive and simulated the performance of the axis control law under the influence of structural vibrations received by the position sensor.2.6.3 Coupled flexible multi-body simulationThe coupled flexible multi-body simulation is used to simulate the dynamic behaviour of the machine taking into account the behaviour of the control loops of the drives [48], [80], [115]. The models of the single components of the machine tool can represent the static as well as the dynamic behaviour and are coupled by flexible connectors. In reality, guiding systems and bearings appear as joints between the components. These joints are approximated by spring-damper-elements in the flexible multi-body model. For example, for each guide shoe between two structural components one spring-damper element with stiffness and damping values in the X, Y and Z-direction is defined.To consider the influence of the individual drives of the machine tool on the dynamic behaviour, the flexible multibody model is coupled with a model of the control loops via an interface [14], [115], [126].Different research activities in the field of coupled flexible multi-body simulation have been done by Reinhart et al. [14], [80], Weck et al. [108], [109], [110], [115], [116], [126], Großmann et al. [47], [49], Denkena et al. [33], [34] ,[100] and Turna .The model set-up as well as the different types of simulations are discussed in the next sections.2.6.3.1 Model configurationEach structural component of the machine tool is modeled as a so-called flexible body [31], [115], [116]. The different elements which are used to connect the structural components, such as guiding systems, mounting devices orball-screw-drives, are modelled as a combination of flexible connectors and joints depending on the specific configuration [14].The individual flexible components of the multi-body model are connected by these flexible connectors depending on the direction of the internal force of the component (1D-element or 3D-element). The different model techniques of the different connectors in multi-body models are pictured in Figure 15.Some typical modelling techniques of popular machine components are specified below.Mounting devicesIn most technical applications the machine tool is mounted with special mounting devices onto the foundation. The stiffness and the damping in three directions have a strong influence on the dynamic behaviour of the machine tool. These components are modelled by three dimensional spring-damper-elements [126].Guiding systemsThe guiding systems are used to determine a defined movement of different machine components relative to each other. Guiding systems are also modelled by3Dspring-damper-elements. Parameters of these elements are the stiffness in two directions, perpendicular and transverse to the direction of movement. The stiffness in the direction of movement is nearly zero. The damping of such a guiding system is considered in three directions [126], [14].Figure 15: Model configuration for the flexible MBS.Ball-screw-drivesThese drives are used to realise translational movement of machine axes. Different components are used in such a drive system. The bearings and the ball screw-nut are modelled with 3D-spring-damper-elements with stiffness and damping parameters in all directions. The screw is modelled using flexible beam elements, which are able to rotate about the pitch attitude. The rotation of the screw, which is caused by the model of the servodrive in the control model, is transformed into a translational movement by the use of a nut. Thus it is possible to simulate the dynamic behaviour of such systems [113], [115],[116].2.6.3.2 Generation of flexible multi-bodiesTo consider the flexibility of the machine components during the multi-body simulation, data from natural vibration and deformation calculations of the individual components, the so-called Superelement Creation, are integrated in the multi-body model through an interface of the multi-body simulation program to popularFinite-Element- Programs [14], [76], [115] [116].Superelement Creation uses a Finite-Element-Model to define a component of a complex structure, and a connection degree of freedom set (DOF) to specify the interface nodes, or attachment points, of the component to other components of the structural system and points where forces are applied. The software calculates fixed normal modes and static constraint modes to approximate the general behaviour of the component at those “interface node degrees of freedom”.The fixed normal modes contain the dynamic response of the superelement when all “connection degrees of freedom” are fixed. The static constraint modes contain the static response assumed by the component when one degree of freedom of one interface point is given a unit deflection while fixing all other “interface degrees of freedom”. The solver perf orms Superelement Creation much like normal modes analysis using the Lanczos method, then uses the Craig-Bampton method to generate the superelement [31].The different modes of a super-element creation are illustrated in Figure 16.Figure 16: The Craig-Bampton theorem for the flexiblemulti-body simulation.For the Craig-Bampton (CB) solution option, processing concludes at this point; the reduced mass and stiffness matrices as well as the fixed normal modes and static constraint modes are stored in an output file for the interface to the multi-body simulation program.Tönshoff et al. [100] developed an alternative approach to model the elasto-kinetic behaviour of machine tool structures based on the theory of flexible multi-bodies.2.6.3.3 Coupling of multi-body models with control loopsTo consider the dynamic behaviour of the control loop a coupling to commercial Computer-Aided-Control-Engineering (CACE) programs is possible with common multibody simulation programs [34], [48], [110].Especially for machines with linear direct drives, where no mechanical transfer elements occur, the consideration of the control loops is necessary for the approximation of the drive system stiffness [108], [110], [126]. The drive control loops generated in the CACE environment can communicate with the complete machine model in the multi-body system.Figure 17 depicts the general structure of this coupling for the coupled flexible multi-body simulation of machine tools.Figure 17: Coupling of flexible multi-boidy models and control loops.The entire control system (incl. all non-linearities) delivers the resulting drive power of each axis to the multi-body system. The control loop itself is closed with the help of the velocities and displacements of the axes determined from the multi-body system.2.6.3.4 Results of the coupled flexible multi-body simulationFor the simulation of flexibility frequency response functions of the coupled flexible multi-body model, an excitation signal must additionally be defined. For this purpose, so-called INPUTS and OUTPUTS have to be generated. In the INPUT, a value is controlled from the outside for each time step during the calculation. Through the OUTPUT that can be applied as a force in the X-, Y- and Z-direction at any location of the multi-body model, the outer signal is directed into the structure [14], [47], [108], [110], [115], [126].In case of machine tools an excitation at the machining interface (tool centre point) is useful, because it corresponds to the method for experimental investigations and best depicts the excitation through machining forces in the chip removal process [108], [114], [115]. Basically, sinus wobbles, noise or an impulse are considered as excitation signal types [114].These frequency response functions are useful for the estimation of the interaction between the mechanical structure and the control during the design stage, as well as for the estimation of the influence of the controller parameters on the dynamic behaviour at the tool centre point [126], see Figure 18.\ Figure 18: Simulated frequency response functionEspecially for machine tools with small workspace dimensions, the potential of the installed drive power can only be used efficiently at high jerk settings. To optimise the dynamic behaviour of machine tools the coupled flexible multi-body simulation can be used to analyse the maximum jerk settings of the feed drives. Therefore an inputsignal for the control loops of the drives can be generated by a virtual controller.The simulation of such a positioning operation is illustratedin Figure19.Fig ure 19: Simulation of a positioning operationThe influence of the jerk on the path deviation during a positioning operation was investigated in this case. The desired path of the Z-unit was generated by a model of the controller and used as an input-signal for the control loop of the z-axis with different jerk settings. The z-unit started at standstill and was accelerated to the maximum speed of the z-drive. After a short movement with constant velocity the drive was decelerated to standstill. The results of this simulation are shown in Figure 20.Figure 20: Simulation results of a positioning operation.Such positioning operations always excite natural frequencies of the machine tool, which can lead to deviations of the desired tolerances of the workpiece or even to damaged tools dependent on the amplitude of the vibration [14], [108], [110], [126].The evaluation of the simulated vibration signals enables the allocation of the excited natural frequencies and the derivation of arrangements for improvements during the design process.2.7 Validation and optimisation of the simulation modelsDespite the rapid development of the available software tools in recent years, the correct estimation of the simulation parameters is still a problem, which limits the accuracy of the results [107].The prediction of stiffness and especially of the damping characteristics of machine components is extremely difficult due to their dependence on many different influences, like lubrication, pre-loads or tolerances [53], [68]. Measurements of the dynamic behaviour of similar machine tools or components and the validation of existing simulation models can help to find better initial values for future simulations.The measurement of the dynamic properties of machine tools usually targets two characteristics [111]:• The Frequency Response Function (FRF) of the compliance at the tool centre point (TCP)• The mode shapes of the machine with their associated resonance frequencies and dynamic amplitudes as well as the phase shift.Both characteristics can be measured with special experiments as depicted in Figure 21 for the FRF measurement. For the determination of the FRF, the TCP is excited with a dynamic actuator and the reaction of the TCP is measured. Via Fast Fourier Transformation (FFT), a frequency spectrum or a locus curve can be generated.The results of both examinations can help the design engineer to validate the simulation models in order to find realistic values for the stiffness and damping behaviour of the machine components. Design modifications to improve weak points of the machine can be assessed analytically before they are implemented in the current design or in the next machine generation.Figure 21: Measuring of a frequency response functionThe calibration of simulation models, especially the parameters ofspring-damper-elements (stiffness- and damping-coefficients) is extremely difficult and very timeconsuming. For the described example of the machine tool in Figure 15 the flexible multi-body model contains 48 different parameters to model the mounting devices, the guiding systems, different bearings and the mechanical components of theball screw drive. It is obvious that a manual calibration of such complex simulation models of machine tools is nearly impossible.Witt and Brecher [24] developed an approach for an automated optimisation of simulation models with the help of measured frequency response functions. To match the results of the simulation and the measuring it is possible to model the stiffness and damping parameters as design variables and optimise them by using numerical optimization methods, e.g sequential quadratic programming (SQP). The design goal of this optimisation is the minimization of the deviation of the measured and the simulated frequency response function.The principle approach of this optimisation is illustrated inthe following Figure 22.Figure 22: Automated model update with measured frequency response functions.附录2 中文翻译动态结构和回路控制可按不同的方法可以分为模型替换模拟和动态性能（特性）联合模拟。

本科毕业设计论文题目飞机减速系统壳体类零件三维设计与加工仿真毕业任务书一、题目飞机减速系统壳体类零件三维设计与加工仿真二、指导思想和目的要求毕业设计（论文）是培养学生自学能力、综合应用能力、独立工作能力的重要教学实践环节。

在毕业设计中，学生应独立承担一部分比较完整的工程技术设计任务。

要求学生发挥主观能动性，积极性和创造性，在毕业设计中着重培养独立工作能力和分析解决问题的能力，严谨踏实的工作作风，理论联系实际，以严谨认真的科学态度，进行有创造性的工作，认真、按时完成任务。

三、主要技术指标1、pdf零件图一张；2、三维实体模型一个；3、实体加工仿真NC程序一个；4、加工仿真验证结果；5、设计说明书一份；四、进度和要求1、查阅和翻译相关机械专业英语文献（1周）2、认真分析图纸，把握零件结构。

（2周）3、用UG绘制零件图形，完成三维造型（3-5周）4、查阅有关仿真加工资料，设计出仿真加工的方式方法（6-7周）5、完成仿真加工及验证（8-12周）6、撰写毕业论文（13-14周）7、论文打印及答辩（15-16周）五、主要参考书及参考资料[1]、詹熙达,catiav5r20快速入门教程. 机械工业出版社2011[2]、网络教程（）CATIA编程入门视频教程[3]、马兰，机械制图，机械工业出版社，2008[4]、施平., 机械工程专业英语教程. 第二版. 2008[5]、吴宗泽，罗圣国.机械设计课程设计手册，第3版2006[6]、王素玉, 高速切削加工表面质量的研究.山东大学博士论文，2006[7]、宋爱平，CAD/CAM技术综合实训指导书，机械工业出版社，2012摘要近年来，随着数控技术与仿真技术的发展，在现代制造工业中，性能良好的加工中心设备和数控仿真技术使许多零件的加工更为方便，使得产品质量和加工效率都有所近年来，随着数控技术与仿真技术的发展，在现代制造工业中，性能良好提高。

利用这些设备如何能高效地加工出更为优质的零件，已成为企业关心的问题。

中英文资料Constructing Rules and Scheduling Technology for 3DBuilding ModelsAbstract3D models have become important form of geographic data beyond conventional 2D geospatial data. Buildings are important marks for human to identify their environments, because they are close with human life, particularly in the urban areas. Geographic information can be expressed in a more intuitive and effective manner with architectural models being modeled and visualized in a virtual 3D environment. Architectural model data features with huge data volume, high complexity, non-uniform rules and so on. Hence, the cost of constructing large-scale scenes is high. Meanwhile, computers are lack of processing capacity upon a large number of model data. Therefore, resolving the conflicts between limited processing capacity of computer and massive data of model is valuable. By investigating the characteristics of buildings and the regular changes of viewpoint in virtual 3D environment, this article introduces several constructing rules and scheduling techniques for 3D constructing of buildings, aiming at the reduction of data volume and complexity of model and thus improving computers’ efficiency at scheduling large amount ofarchitectural models. In order to evaluate the efficiency of proposed constructing rules and scheduling technology listed in the above text, the authors carry out a case study by 3D constructing the campus of Peking University using the proposed method and the traditional method. The two results are then examined and compared from aspects of model data volume, model factuality, speed of model loading, average responding time during visualization, compatibility and reusability in 3D geo-visualization platforms: China Star, one China’s own platform for 3D g lobal GIS manufactured by the authors of this paper. The result of comparison reveals that models built by the proposed methods are much better than those built using traditional methods. For the constructing of building objects in large-scale scenes, the proposed methods can not only reduce the complexity and amount of model data remarkably, but can also improving computers’ efficiency.Keywords:Constructing rules, Model scheduling, 3D buildingsI. INTRODUCTIONIn recent years, with the development of 3D GIS (Geographical Information System) software like Google Earth, Skyline, NASA World Wind, large-scale 3D building models with regional characteristics have become important form of geographic data beyond conventional 2D geospatial data, like multi-resolution remote sensing images and vector data [1].Compared to traditional 2D representation, geographic information can be expressed in a more intuitive and effective manner with architectural models being modeled and visualized in a virtual 3D environment. 3D representation and visualization provides better visual effect and vivid urban geographic information, and thus plays an important role in people's perceptions of their environment. Meanwhile, the 3D building data is also of great significance for the construction of digital cities.But how to efficiently visualize thousands of 3D building models in a virtual 3D environment is not a trivial question. The most difficult part of the question is the conflicts between limited processing capacity of computer and massive volume of model data, particularly in the procedure of model rendering. Taking the 3D modeling of a city for the example using traditional 3D modeling method, suppose there are 100 000 buildings to model in the urban area and the average size of model data for each building is roughly 10 M. So the total data volume of building models in the city could reach a TB level. However, the capacity of ordinary computer memory is only in the GB scale. Based on this concern, the authors proposed the scheduling technology for large-scale 3D buildings models in aspects of model loading and rendering. Due to the lack of building constructing rules and standard, models of buildings vary in aspects of constructing methods, textures collection and model data volume, especially in aspects of model reusability and factuality. Such a large amount of data without uniform constructing rules becomes a huge challenge for data storage, processing and visualization in computers. It also brings the problem of incompatibility among different 3D GIS systems.After years of research in GIS (Geographic Information System), people have accumulated a number of ways to solve the above problems [3]. However in virtual 3D environment, because of the difference in data organization and manners of human computer interaction (HCI), we need to apply a new standardized method of modeling and scheduling for 3D models. At present, there is no such a uniform method as the constructing specification or standard for the modeling of 3D buildings. Existing approaches are insufficient and inefficient in the scheduling of large-scale building models, resulting in poor performance or large memory occupancy. In response to such questions, the authors proposed a new method for the construction of 3D building models. Models built using the proposed methods could be much better than those built using traditional methods. For the 3D modeling of building objects in scenes of large scale, the proposed methods can not only remarkably reduce the complexity and amount of model data, but can also improving the reusability and factuality of models. Concerning the scheduling of large-scale building models, the Model Loading Judgment Algorithm (MLJA) proposed in this paper could solve the optimal judgment problem of model loading in 3D vision cone, particularly in circumstance with uncertain user interactions.This paper first examines and analyzes existing problems in constructing and scheduling steps of 3D building models. Then the authors propose a set of constructing rules for 3D building models together with methods of model optimization. Besides, special scheduling technology and optimization method for model rendering is also applied in this paper for large-scale 3D building models. In order to evaluate the efficiency of proposed rules and methods, a case study is undertaken by constructing a 3D model for the main campus of Peking University and Shenzhen using both the proposed method and the traditional method respectively. The two resulting 3D models of Peking University campus and Shenzhen are then examined and compared with one other in aspects of model data volume, model factuality, speed of model loading, average responding time during visualization, compatibility and reusability in various 3D geo-visualization platforms like China Star (one China’s own platform for 3D global GIS manufactured by the authors),Skyline, etc. Result of comparison tells that provided similar factuality of models, using the proposed method of us, the data volume of models was reduced by 86%; the speed of model loading was increased by 70%; the average responding time of model during visualization and interaction speed was reduced by 83%. Meanwhile, the compatibility and reusability of 3D model data are also improved if they are constructed using our approach.II. MODELING RULES OF 3D BUILDINGS 3D scene is the best form of visualization for digital city systems. While constructing 3D models for buildings objects, proper methods and rules should be used, which are made with full concerns of the characteristics of 3D building models [2]. The resulting models should be robust, reusable and suitable enough for transmission over computer network, and should at the same time be automatically adapted to system capability.Generally speaking, methods of constructing 3D building models can be classified into three types: wireframe modeling, surface modeling and solid modeling. In normal circumstances, to model buildings in 3D format, the framework of building should be constructed first according to the contour features, number of floors, floor height, aerial photograph and liveaction photos of buildings. Then, gather the characteristics of scene that the buildings to model are representing. Important characteristics include buildings aerial photograph or liveaction shooting photos. Finally, map the gathered texture to model framework, optimize the model and create database of the 3D building models.Although there have already been many approaches for the construction of 3D building models, a unified modeling method and rules are still needed to improve the efficiency, quality, facilitate checking, reusability and archiving of constructed models. By investigating the characteristics of buildings, we found that buildings have regular geometric solid for modeling, similar texture on the surfaces of different directions, high similarity in small-scale models of buildings, etc. According to these, this article gives a discussion on the modeling rules from three aspects, includingconstructing rules of the 3D building models, texture mapping rules of 3D building models and optimization method for constructed models based on mentioned constructing rules.A. Constructing rules of the 3D building modelsThe 3D building modeling refers to the procedure of representing true buildings from the real world into computer in the form of 3D objects [4]. Human beings, as the creator and at the same time potential users of models, play a key role in this procedure. People are different from each other in the understanding of the building objects, methods of modeling and the software tools they use for modeling. Such differences among people who carry out modeling work at the same time lead to the 3D models of diverse quality and low efficiency. So the 3D building constructing rules proposed in this article become necessary and helpful to solve the above problems.1) Combine similar floors as a whole and keep the roof independent2) Share similar models and process the details especially3) Constructing in the unit of meters4) Define central point of the model5) Unified model codes6) Reduce number of surfaces in a single model7) Reduce combination of the models8) Rational split of modelsB. Texture mapping rules of 3D buildingsBased on the framework of 3D models, we need to attach these models with proper textures to create a better visualization effect for 3D buildings. The quality of texture mapping has a direct impact on the visual effect of the scene whiling being rendered [5]. Since the graphics card of computer will load all the textures together when rendering a model, texture mapping rules and the quality of the texture mapping can directly influence the efficiency of rendering as well.C. Optimization of models based on constructing rulesBased on constructing rules and the characteristics of 3D building models, theauthors develop a software tool to optimize the 3D building models automatically. The optimizations implemented in the software tool contain the deletion of models’ internal textures, merging adjacent vertices/lines/surfaces, removing un-mapped framework and so on. Besides, the software can enhance the shape of the whole model, texture position and model facticity in the procedure of model optimization.III. SCHEDULING TECHNOLOGY OF LARGE-SCALE 3DBUILDING MODELSFor the 3D visualization of large-scale architectural models, a series of measures could be applied to ensure the efficient rendering of models. Important measures includes the scene organization, vision cone cutting, elimination of textures on the backside of models, Shader optimization, LOD Algorithm, math library optimization, memory allocation optimization, etc..How to display thousands of 3D city buildings’ models in a virtual 3D environment is not trivial. The main problem is the scheduling of models [7]. It determines when and which models to be loaded. This problem can be divided into two smaller problems: Find visible spatial region of models in 3D environment, and optimization method of model rendering efficiency.A. Find visible spatial region of models in 3D environmentAccording to operating mechanism of computers during 3D visualization and the characteristics of large-scale 3D scene, we need to determine the position of current viewpoint first before loading signal models or urban-unit models. Then in response to the regular changes of viewpoint in virtual 3D environment, the system will preload the 3D model data into memory automatically. In this way, frequent IO operations can be reduced and thus overall efficiency of system gets improved. A new algorithm named MLJA (Model Loading Judgment Algorithm) is proposed in this paper in order to find out visible region of models in the 3D environment. The algorithm integrates the graticules and elevation information to determine the current viewpoint of users in the 3D space. And with the movement of viewpoint, the algorithm schedules the loading of model correspondingly and efficiently.B. Optimization method of model rendering efficiencyThe scheduling method of large-scale 3D building models proposed above is an effective way to solve the problem caused the contradiction between large model data volume and limited capacity of computers. According to the algorithm, we can avoid loading the whole large-scale 3D building models at one time for the sake of limited computer memory, and then improve system efficiency in the procedure of model loading and abandoning. Due to the limited capacity of GPU and local video memory, we need a further research on how to display the loaded model data in more efficient manner. In the remaining part of this paper, the authors will continue to introduce several methods on the optimization of model rendering in the vision cone.1) Elimination of textures on the backside of modelsThe backside of the 3D model is invisible to the users. If we omit the texture mapping for the 3D model on the backside, the processing load of graphic card will be reduced as much as at least 50%. Besides, according to an investigation on procedure of actual model rendering, the authors found that on the backside of the 3D model, the invisible texture is rendered in a counter-clockwise manner against the direction of eyesight, while the visible texture mapping is rendered in clockwise manner. So we can omit the rendering of models which is intended to be rendered in counterclockwise manner. Therefore, the textures won’t exist on the back of 3D models. The graphic card could then work more rapidly and efficiently.2) Eliminate the shielded modelBy calculating the geometric relationship between 3D models in the scene, the shielded models can be omitted while displaying the scene with appropriate shielding patches. Through this way, we can effectively reduce the usage of graphics card memory, and thus achieve higher rendering efficiency and faster 3D virtual system.In the virtual 3D geographic information system, we often observe 3D models from a high altitude. It is especially true for large-scale outdoor 3D models. The usual arrangement of 3D building models are always sparse, however the real block is very small. Therefore, establishing an index for visual control, which is similar to the BSP tree, doesn’t amount to much. Through carefully studying DirectX, we found that wecan take advantage of the latest Z-buffering technology of DirectX to implement the shielding control of models.3) Optimization method of the Shader instructionsIn shader 3.0 technology, SM (Shader Model) is a model which can optimize the rendering engine. A 3D scene usually contains several shaders. Among these shaders, some deal with the surfaces and skeletons of buildings, and others deal with the texture of 3D building models.Geometry can be handled quickly by shader batch process. The shader can combine similar culmination in 3D building models, deal with the correlation operation of a single vertex, determine the physical shape of the model, link the point, line, triangle and other polygons for a rapid processing while create new polygons, etc. We can assign the computing task to shader and local video memory directly in a very short time without bothering the CPU. In this case, visual effects of smoke, explosions and other special effects and complex graphics are no longer necessary to be processed by the CPU of computer. Such features of shader can speed up both the CPU and graphic card in processing huge amount of 3D models.4) LOD algorithm of large-scale 3D sceneLOD (Level of Detail) is a common and effective solution to resolve the conflicts between real time visualization and the authenticity of models [8]. By investigating the main features and typical algorithms of LOD technology, the authors proposed a new structure for dynamic multi-level display. This structure not only can be applied to the mesh simplification of models with many different but fixed topologies, but also can be applied to the mesh simplification of models with variable topology. Therefore, the LOD technology can be applied to any grid model. Based on the above concerns, the authors also design a mesh simplification algorithm for variable topology through vertices merge. Via the dual operations of vertex merging and splitting, we can achieve smooth transition across different LOD levels of models, and automatically change the model topology.These above techniques plays important role in 3D scene. It can not only enable a rapid visualization of large-scale scene, but also can provide a high-resolutiondisplay of scene at a local scale with plenty of architectural details.IV. CONCLUDING REMARKSConstructing rules and scheduling technology plays an important role in the application of large-scale 3D buildings. Since people’s demand for 3D expression brings a challenge of high-efficiency and high-quality to virtual 3D environment, the methods proposed in this article give a good try in these aspects. According to the authors’ research and case studies in this paper, integration of constructing rules and scheduling technology is promising in providing powerful tools to solve the conflicts between limited processing capacity of computer and massive data of models. The result of our case study on Peking University indicates that the proposed new method on constructing rules and scheduling technology for large-scale 3D scene is highly feasible and efficient in practice. The proposed methods can not only standardize the procedure of model construction, but also can significantly shorten the time taken in scheduling large-scale 3D buildings. It introduces a new effective way to develop applications for large-scale three-dimensional scene.构建三维建筑模型的规则和调度技术摘要三维模型已成为超越了传统的二维地理空间数据的一种重要的地理数据形式。

编号:毕业论文(设计)题目基于Proe简单零件的造型及数控仿真加工专业机械设计制造及其自动化教学单位德州学院机电工程系二O一二年05月03日摘要鼠标上盖是流线形结构,使用二维绘图难以描述，本课题采用Pro/E软件对鼠标上盖制品及模具进行了三维造型，结合生成凸凹模的结构等因素，生成刀具轨迹；在仿真加工结果无误后，使用后置处理程序选取相应的配置文件，将刀具轨迹转化为数控机床可以识别的NC 程序，为更加高速、快捷的造型、生产提供了一种切实可行的办法。

生成的NC程序可以利用DNC方式传输给数控机床进行三维加工。

关键词:鼠标上盖Pro/E 数控加工后处理目录第一章引言 (1)1.1研究意义及内容 (1)1.2概述 (2)3.3总结 (4)第二章鼠标上盖的三维造型 (5)2.1 创建新零件 (5)2.2创建双向拉伸曲面 (5)2.3创建落下曲线的参照草绘曲线 (6)2.4创建落下曲线 (6)2.5创建鼠标顶面的轮廓曲线 (7)2.6创建两条自由曲线 (7)2.7将自由曲线混合成自由曲面 (8)第三章鼠标上盖分模 (9)3.1创建模具 (9)3.2模具布局 (10)3.3设置收缩率和创建工件 (13)3.4创建工件 (14)3.5创建分型面 (15)3.6分割模具体积块 (18)3.7创建体积块零件 (19)第四章鼠标上盖模具的数控加工工艺分析 (20)4.1图形分析 (20)4.2加工工艺分析 (20)4.3加工工艺卡 (21)第五章鼠标上盖的数控模拟加工 (22)5.1创建工艺文件 (22)5.2制造设置 (23)5.3进行退刀设置 (24)5.4创建铣削加工窗口 (24)5.5鼠标上盖凸模数控加工及模拟加工 (24)5.6鼠标上盖凹模数控加工及模拟加工 (35)第六章结论 (41)6.1 工作小结 (41)6.2 工作展望 (41)6.3 谢辞 (41)参考文献: (42)第一章引言1.1研究意义及内容（1）课题的意义制造业是国民经济的命脉，机械制造业又是制造业中的支柱与核心。

1 引言计算机辅助设计和计算机辅助制造(Computer Aided Design and Computer Aided Manufacturing，简称CAD/CAM)技术作为传统技术与计算机技术的结合，以不同方式广泛用于各项工程实践中，例如：绘图和设计、生成着色图和动画显示、应用几何模型完成有限元等工程分析、生成工艺规划及零件数控加工程序等。

随着计算机技术与现代设计制造技术的发展，CAD/CAM技术作为现代产品设计制造方法及手段的综合体现，在产品生产过程中发挥了重要的作用。

Mastercam集二维绘图、三维实体造型、曲面设计、体素拼合、数控编程、刀具路径模拟及真实感模拟等功能于一身，其强大稳定的造型功能可设计出复杂的曲线、曲面零件。

Mastercan可靠刀具路径校验功能模拟零件加工整个过程，模拟中不但能显示刀具和夹具，还能检查出刀具和夹具与被加工零件的干涉、碰撞情况，真是反映加工过程中的实际情况，不愧为一优秀的CAD/CAM软件。

同时Mastercam对系统运行环境要求较低，使用户无论是在造型设计、CNC铣床、CNC 车床或CNC线切割等加工操作中，都能获得最佳效果。

2 零件的造型2．1 CAD/CAM技术经过多年的推广，CAD技术已经广泛地应用在机械、电子、航天、化工、建筑等行业。

应用CAD技术起到了提高企业的设计效率、优化设计方案、减轻技术人员的劳动强度、缩短设计周期、加强设计的标准化等作用。

90年代以后CAD 技术进入开放式、标准化、集成化和智能化的发展时期，这阶段的CAD技术都具有良好的开放性，图形接口、功能日趋标准化。

CAD体系结构大体可分为基础层、支撑层和应用层三个层次。

基础层由计算机及外围设备和系统软件组成。

随着网络的广泛使用，异地协同虚拟CAD环境将是CAD支撑层的主要发展趋势。

应用层针对不同应用领域的需求，有各自的CAD专用软件来支援相应的CAD工作。

CAD /CAM技术随着Internet/Intranet网络和并行高性能计算及事务处理的普及，使奢地、协同、虚拟设计及实时仿真技术在CAD/CAE/CAM中得到了广泛应用。

基于Mastercam X5棘轮零件三维设计及自动编程【摘要】本文主要阐述棘轮零件的三维造型及数控加工，内容包括零件图的工艺分析、工件的装夹方案、零件的加工工艺分析、工艺流程、程序设计等，其中零件图的工艺分析包括零件图的完整性及正确性、材料、技术要求、结构工艺性等方面的分析；装夹方案包括毛坯的选择、机床的选择、夹具的选择；加工工艺分析包括加工顺序的安排、刀具的选择、切削用量的选择等等。

这些都是零件加工的重要组成部分，要使零件的加工精度，效率得到提高，就必须先对零件进行分析，确定好正确的工艺流程，使用Mastercam软件对零件进行三维造型和数控加工，充分发挥数控机床的高精度，高效率的特性。

关键词：工艺分析、装夹方案、工艺流程、三维造型、自动编程Abstract: This paper mainly discusses the 3D modeling and NC machining of ratchet parts, including parts of the process analysis, workpiece clamping scheme, parts of the process analysis, process, program design, the process of parts drawing analysis includes parts of the integrity and correctness, materials, technical requirements, construction technology and so on; the clamping scheme includes the choice of blank, the choice of machine tools, jig choice; analysis of the technological process including the sequencing of machining, tool selection, cutting the amount of choice etc.. These are an important part of machining, the machining accuracy of parts, improve the efficiency, we must first on the parts for analysis, determine the correct process, 3D modeling and NC machining of parts using the Mastercam software, give full play to the high accuracy of numerical control machine, high efficiency characteristics.Key words: Process analysis, clamping scheme, process flow, three-dimensional modeling, automatic programming目录1 绪论 (5)1.1数控加工技术概述 (5)1.2数控铣削加工技术 (6)1.3本课题的主要任务 (6)2 零件的三维造型设计 (7)2.1软件的选择 (7)2.2零件的三维造型设计 (8)2.2.1 绘制顶盖 (8)2.2.2 底座的绘制 (10)2.2.3 实体的结合 (11)2.2.4 圆角的生成 (12)2.2.5 实体抽壳 (12)2.2.6 开口 (13)2.2.7 六边形凸台的生成 (14)2.2.8 孔的生成 (15)2.3本章小结 (15)3 零件的工艺规程设计 (16)3.1零件的工艺分析 (16)3.1.1 零件的结构特点工艺性分析 (16)3.2毛坯的选择 (16)3.3定位基准的选择 (17)3.4装夹方式的选择 (17)3.5工序及工步的划分 (17)3.6刀具的选择 (17)3.7切削用量的选择 (18)3.8工艺卡片的制定 (19)3.8.1 工艺过程卡 (19)3.8.2 数控加工工序卡 (20)3.9本章小结 (21)4 零件的MASTERCAM自动编程及仿真加工 (21)4.1刀路设计前的准备 (21)4.2毛坯的设置 (22)4.3刀具的设置 (22)4.4工序3加工型腔部分的刀路设计 (23)4.4.1 工步1开粗的刀路设计 (23)4.4.2 工步2半精加工壁边及六边形凸台轮廓的刀路设计 (24)4.4.3 工步3精加工腔底及六边形凸台表面的刀路设计 (26)4.4.4 工步4精加工壁边及半精加工型腔喇叭锥面的刀路设计 (28)4.4.5 工步5精修六边形凸台轮廓的刀路设计 (29)4.4.6 工步6精加工喇叭锥面的刀路设计 (29)4.4.7 钻孔的刀路设计 (31)4.5工序4铣凸台及外形的刀路设计 (32)4.5.1 工步1开粗的刀路设计 (32)4.5.2 工步2精加工外轮廓的刀路设计 (33)4.5.3 工步3半精加工凸台轮廓 (34)4.5.4 工步4精加工凸台交接面 (35)4.5.5 工步5精加工凸台及圆角 (35)4.6后处理设置（加工程序的生成） (36)4.7仿真加工 (40)结束语 (42)谢辞 (43)参考文献 (44)1 绪论1.1 数控加工技术概述数字控制简称数控（NC），是近代发展起来的一种自动控制技术，是用数字化信息实现设备控制的一种方法，在数控加工技术方面得到了广泛的应用。

编号：毕业设计(论文)外文翻译（原文）院（系）：机电工程学院专业：机械设计制造及其自动化学生姓名：学号：指导教师单位：姓名：职称：2014年 5 月23 日Design of machine elementsThe principles of design are, of course, universal. The same theory or equations may be applied to a very small part, as in an instrument, or, to a larger but similar part used in a piece of heavy equipment. In no ease, however, should mathematical calculations be looked upon as absolute and final. They are all subject to the accuracy of the various assumptions, which must necessarily be made in engineering work. Sometimes only a portion of the total number of parts in a machine are designed on the basis of analytic calculations. The form and size of the remaining parts are designed on the basis of analytic calculations. On the other hand, if the machine is very expensive, or if weight is a factor, as in airplanes, design computations may then be made for almost all the parts.The purpose of the design calculations is, of course, to attempt to predict the stress or deformation in the part in order that it may sagely carry the loads, which will be imposed on it, and that it may last for the expected life of the machine. All calculations are, of course, dependent on the physical properties of the construction materials as determined by laboratory tests. A rational method of design attempts to take the results of relatively simple and fundamental tests such as tension, compression, torsion, and fatigue and apply them to all the complicated and involved situations encountered in present-day machinery.In addition, it has been amply proved that such details as surface condition, fillets, notches, manufacturing tolerances, and heat treatment have a market effect on the strength and useful life of a machine part. The design and drafting departments must specify completely all such particulars, must specify completely all such particulars, and thus exercise the necessary close control over the finished product.As mentioned above, machine design is a vast field of engineering technology. As such, it begins with the conception of an idea and follows through the various phases of design analysis, manufacturing, marketing and consumerism. The following is a list of the major areas of consideration in the general field of machine design:①Initial design conception;②Strength analysis;③Materials selection;④Appearance;⑤Manufacturing;⑥Safety;⑦Environment effects;⑨Reliability and life;Strength is a measure of the ability to resist, without fails, forces which cause stresses and strains. The forces may be;①Gradually applied;②Suddenly applied;③Applied under impact;④Applied with continuous direction reversals;⑤Applied at low or elevated temperatures.If a critical part of a machine fails, the whole machine must be shut down until a repair is made. Thus, when designing a new machine, it is extremely important that critical parts be made strongenough to prevent failure. The designer should determine as precisely as possible the nature, magnitude, direction and point of application of all forces. Machine design is mot, however, an exact science and it is, therefore, rarely possible to determine exactly all the applied forces. In addition, different samples of a specified material will exhibit somewhat different abilities to resist loads, temperatures and other environment conditions. In spite of this, design calculations based on appropriate assumptions are invaluable in the proper design of machine.Moreover, it is absolutely essential that a design engineer knows how and why parts fail so that reliable machines which require minimum maintenance can be designed. Sometimes, a failure can be serious, such as when a tire blows out on an automobile traveling at high speeds. On the other hand, a failure may be no more than a nuisance. An example is the loosening of the radiator hose in the automobile cooling system. The consequence of this latter failure is usually the loss of some radiator coolant, a condition which is readily detected and corrected.The type of load a part absorbs is just as significant as the magnitude. Generally speaking, dynamic loads with direction reversals cause greater difficulties than static loads and, therefore, fatigue strength must be considered. Another concern is whether the material is ductile or brittle. For example, brittle materials are considered to be unacceptable where fatigue is involved.In general, the design engineer must consider all possible modes of failure, which include the following:①Stress;②Deformation;③Wear;④Corrosion;⑤Vibration;⑥Environmental damage;⑦Loosening of fastening devices.The part sizes and shapes selected must also take into account many dimensional factors which produce external load effects such as geometric discontinuities, residual stresses due to forming of desired contours, and the application of interference fit joint.Mechanical properties of materialsThe material properties can be classified into three major headings: (1) physical, (2) chemical, (3) mechanicalPhysical propertiesDensity or specific gravity, moisture content, etc., can be classified under this category. Chemical propertiesMany chemical properties come under this category. These include acidity or alkalinity, react6ivity and corrosion. The most important of these is corrosion which can be explained in layman’s terms as the resistance of the material to decay while in continuous use in a particular atmosphere.Mechanical propertiesMechanical properties include in the strength properties like tensile, compression, shear, torsion, impact, fatigue and creep. The tensile strength of a material is obtained by dividing the maximum load, which the specimen bears by the area of cross-section of the specimen.This is a curve plotted between the stress along the This is a curve plotted between the stress along the Y-axis(ordinate) and the strain along the X-axis (abscissa) in a tensile test. Amaterial tends to change or changes its dimensions when it is loaded, depending upon the magnitude of the load. When the load is removed it can be seen that the deformation disappears. For many materials this occurs op to a certain value of the stress called the elastic limit Ap. This is depicted by the straight line relationship and a small deviation thereafter, in the stress-strain curve (fig.3.1). Within the elastic range, the limiting value of the stress up to which the stress and strain are proportional, is called the limit of proportionality Ap. In this region, the metal obeys hookes’s law, which states that the stress is proportional to strain in the elastic range of loading, (the material completely regains its original dimensions after the load is removed). In the actual plotting of the curve, the proportionality limit is obtained at a slightly lower value of the load than theelastic limit. This may be attributed to the time-lagin the regaining of the original dimensions of the material. This effect is very frequently noticed in some non-ferrous metals.Which iron and nickel exhibit clear ranges of elasticity, copper, zinc, tin, are found to be imperfectly elastic even at relatively low values low values of stresses. Actually the elastic limit is distinguishable from the proportionality limit more clearly depending upon the sensitivity of the measuring instrument.When the load is increased beyond the elastic limit, plastic deformation starts. Simultaneously the specimen gets work-hardened. A point is reached when the deformation starts to occur more rapidly than the increasing load. This point is called they yield point Q. the metal which was resisting the load till then, starts to deform somewhat rapidly, i. e., yield. The yield stress is called yield limit Ay.The elongation of the specimen continues from Q to S and then to T. The stress-strain relation in this plastic flow period is indicated by the portion QRST of the curve. At the specimen breaks, and this load is called the breaking load. The value of the maximum load S divided by the original cross-sectional area of the specimen is referred to as the ultimate tensile strength of the metal or simply the tensile strength Au.Logically speaking, once the elastic limit is exceeded, the metal should start to yield, and finally break, without any increase in the value of stress. But the curve records an increased stress evenafter the elastic limit is exceeded. Two reasons can be given for this behavior:①The strain hardening of the material;②The diminishing cross-sectional area of the specimen, suffered on account of the plastic deformation.The more plastic deformation the metal undergoes, the harder it becomes, due to work-hardening. The more the metal gets elongated the more its diameter (and hence, cross-sectional area) is decreased. This continues until the point S is reached.After S, the rate at which the reduction in area takes place, exceeds the rate at which the stress increases. Strain becomes so high that the reduction in area begins to produce a localized effect at some point. This is called necking.Reduction in cross-sectional area takes place very rapidly; so rapidly that the load value actually drops. This is indicated by ST. failure occurs at this point T.Then percentage elongation A and reduction in reduction in area W indicate the ductility or plasticity of the material:A=(L-L0)/L0*100%W=(A0-A)/A0*100%Where L0 and L are the original and the final length of the specimen; A0 and A are the original and the final cross-section area.Quality assurance and controlProduct quality is of paramount importance in manufacturing. If quality is allowed deteriorate, then a manufacturer will soon find sales dropping off followed by a possible business failure. Customers expect quality in the products they buy, and if a manufacturer expects to establish and maintain a name in the business, quality control and assurance functions must be established and maintained before, throughout, and after the production process. Generally speaking, quality assurance encompasses all activities aimed at maintaining quality, including quality control. Quality assurance can be divided into three major areas. These include the following:①Source and receiving inspection before manufacturing;②In-process quality control during manufacturing;③Quality assurance after manufacturing.Quality control after manufacture includes warranties and product service extended to the users of the product.Source and receiving inspection before manufacturingQuality assurance often begins ling before any actual manufacturing takes place. This may be done through source inspections conducted at the plants that supply materials, discrete parts, or subassemblies to manufacturer. The manufacturer’s source inspector travels to the supplier factory and inspects raw material or premanufactured parts and assemblies. Source inspections present an opportunity for the manufacturer to sort out and reject raw materials or parts before they are shipped to the manufacturer’s production facility.The responsibility of the source inspector is to check materials and parts against design specifications and to reject the item if specifications are not met. Source inspections may include many of the same inspections that will be used during production. Included in these are:①Visual inspection;②Metallurgical testing;③Dimensional inspection;④Destructive and nondestructive inspection;⑤Performance inspection.Visual inspectionsVisual inspections examine a product or material for such specifications as color, texture, surface finish, or overall appearance of an assembly to determine if there are any obvious deletions of major parts or hardware.Metallurgical testingMetallurgical testing is often an important part of source inspection, especially if the primary raw material for manufacturing is stock metal such as bar stock or structural materials. Metals testing can involve all the major types of inspections including visual, chemical, spectrographic, and mechanical, which include hardness, tensile, shear, compression, and spectr5ographic analysis for alloy content. Metallurgical testing can be either destructive or nondestructive.Dimensional inspectionFew areas of quality control are as important in manufactured products as dimensional requirements. Dimensions are as important in source inspection as they are in the manufacturing process. This is especially critical if the source supplies parts for an assembly. Dimensions are inspected at the source factory using standard measuring tools plus special fit, form, and function gages that may required. Meeting dimensional specifications is critical to interchangeability of manufactured parts and to the successful assembly of many parts into complex assemblies such as autos, ships, aircraft, and other multipart products.Destructive and nondestructive inspectionIn some cases it may be necessary for the source inspections to call for destructive or nondestructive tests on raw materials or p0arts and assemblies. This is particularly true when large amounts of stock raw materials are involved. For example it may be necessary to inspect castings for flaws by radiographic, magnetic particle, or dye penetrant techniques before they are shipped to the manufacturer for final machining. Specifications calling for burn-in time for electronics or endurance run tests for mechanical components are further examples of nondestructive tests.It is sometimes necessary to test material and parts to destruction, but because of the costs and time involved destructive testing is avoided whenever possible. Examples include pressure tests to determine if safety factors are adequate in the design. Destructive tests are probably more frequent in the testing of prototype designs than in routine inspection of raw material or parts. Once design specifications are known to be met in regard to the strength of materials, it is often not necessary to test further parts to destruction unless they are genuinely suspect.Performance inspectionPerformance inspections involve checking the function of assemblies, especially those of complex mechanical systems, prior to installation in other products. Examples include electronic equipment subcomponents, aircraft and auto engines, pumps, valves, and other mechanical systems requiring performance evaluation prior to their shipment and final installation.。