High-speed Friction and Wear Behaviour of Ultra-fine Grain Cemented Carbide Cutting Tool
Y.Z. Pan, X. Ai, J. Zhao, Y. Wan
School of mechanical engineering, Shandong University, 250061, Jinan, China
Abstract
Sliding friction and wear tests were carried out in a special tribometer assembled on a CA6140 turning lathe, and high-speed milling experiments were performed on a DMU-70V CNC machining centre, to investigate the friction and wear properties of two different cemented carbides (WC-10Co and WC-12Co) against aluminum alloy . The surface morphologies of the worn surfaces were observed by a S-570 scanning electron microscope. The diffusion behaviors of Co and Al elements were analyzed by a JXA-8800 electron microprobe. The results show that the friction coefficients of both cemented carbides decrease with the increase of normal load and sliding speed under the same friction condition. The friction coeffcient of WC-12Co is larger than that of WC-10Co, but the wear volume loss of WC-12Co is lower than that of WC-10Co. Under the same milling condition, the wear rate and work-piece surface roughness of WC-12Co tool are better than that of WC-10Co tool. The main wear mechanisms of ultra-fine grain cemented carbide are abrasive wear, adhesive wear and diffusion wear.
Keywords: Aluminium alloy, cemented carbide, friction and wear, high-speed milling
1. Introduction
High-speed machining tribology is one of the most key questions in high-speed machining field, which focuses on the friction-wear behaviors and wear mechanisms caused by the thermo-mechanical coupled non-uniform stress field in high-speed machining process[1]. Aircraft aluminum alloy is commonly used in aircraft and die/mold industries due to some advantages such as high tensile strength, high fracture toughness and good corrosion resistance. In high-speed milling process, there are two friction pairs formed by rake face – chip and flank face – workpiece, individually. Due to the high pressure and high temperature, abrasion, adhesion and diffusion phenomena often occur between the fresh contact interfaces of workpiece, chip and cutting tool[2, 3]. Furthermore, Hastings and Oxley pointed out that the most important wear mechanisms and the corresponding cutting speeds/temperatures are: abrasion at low speeds/temperatures, followed by adhesion at moderate speeds/temperatures and then diffusion at high speeds/temperatures[4]. Norari et al. studied the tool wear behavior in dry
180 Y.Z. Pan, X. Ai, J. Zhao and Y. Wan
machining of aluminum alloy. They found that the aluminum diffusion from the chip towards the tool takes place under the combined action of the temperature and the force along the tool-chip interface, and concluded that the deterioration of the tool mainly results in a material transfer from the workpiece to the tool surface[5]. It is a time-consuming and expansive task to perform high-speed milling experiments to explore the wear behaviors and wear mechanisms of cemented carbide tools, because the tool life is very long in high-speed milling of aluminum alloy. In addition, it is very hard to acquire normal load and friction force accurately owing to the complexities of tool geometry and milling process. Therefore, many investigations on the tribological properties of cemented carbides sliding against different reference materials, such as 42CrMo steel, 2045 steel and Si3N4 cermet, have been carried out by means of traditional tribometers. It was found that the Co content, WC grain size and hardness of cemented carbide have important effects on the friction coefficients and the wear rates of cemented carbides[6~8]. W. Zhao et al.[9] and L. Zhu et al.[10] studied the tribological behaviors of WC-Co cemented carbide sliding against Ti6Al4V and PCD. They found that the main wear mechanisms of cemented carbide are abrasive wear, adhesive wear and the plastic deformations of Co binder phase and the removals of WC grains. The disadvantages of above research works are that the friction and wear behaviors were studied using traditional sliding wear methods, such as pin-on-disk and block-on-ring wear tests. The sliding speed, normal load and friction temperature of traditional methods can not meet the requirements of high-speed machining tribology. In this work, some high-speed friction and wear tests were carried out in a special tribometer assembled on a CA6140 turning lathe, and high-speed milling experiments were performed on a DMU-70V CNC machining centre, to investigate the friction and wear properties of two different cemented carbides (WC-10Co and WC-12Co) against aluminum alloy.
2. Experiments
2.1 Cutting Tool and Workpiece Materials
Two different cemented carbides, namely WC-10Co and WC-12Co, were used in high-speed friction tests and high-speed milling experiments. The physical and mechanical properties of WC-10Co and WC-12Co are shown in Table 1. The hardness, the bending strength and the fracture toughness were measured by using MH-6 Vickers hardness tester, three-point bending tests (C sample) and direct indentation method, respectively. The average values were obtained by at least five measurements. Before sliding friction and wear tests, the samples of cemented carbide were made into 16mm×16mm×6mm blocks on a linear cutting machine and then were processed by grinding, lapping and polishing to obtain the surface roughness of Ra 0.1P m.
High-speed Friction and Wear Behavior of Ultra-fine Cemented Carbide Cutting Tool 181
Table 1. The physical and mechanical properties of two cemented carbides Cutting
tool
Co wt % WC grain P m Density g / cm 3 Hardness kgf /mm 2 Bending strength MPa Fracture toughness MPa m 1//2 WC-
10Co
10 0.6 - 0.8 14.5 1550 4200 7.6 WC-
12Co 12 0.3 - 0.5 14.1 1610 4300 9.7
The work-piece material is aircraft aluminium alloy, its chemical compositions as shown in Table 2. The sample of aluminium alloy is a )160mm×300mm bar, on the tip of which there is a ring-step (inner diameter )150mm, external diameter )150mm and height 3mm). The end face of the ring-step was polished by oil stone to obtain the surface roughness of Ra0.1P m. Table 2. The chemical compositions of 7050-T7451 aluminum alloy Zn Cu Mg Zr Mn Si
Fe Ti Al
6.7 2.5 2.3 0.12 0.1 0.12 0.13 0.06 Balance
2.2 High-Speed Friction and Wear Tests
The high-speed friction and wear tests were carried out in a special tribometer in a CA6140 turning lathe. The sketch of the tribometer is shown in Figure 1. The cemented carbide sample is fixed in a cutter arbour. The cutter arbour is installed on a tool holder of dynamometer. The aluminum alloy sample is clamped in the lathe spindle. When a normal load is applied along the spindle direction, the friction pair will be formed by the 16mm×6mm face of cemented carbide sample and the end face of ring-step acted as face-to-face contact. The normal load and friction force were measured continuously by a SDC-C3M19 three-dimensional dynamometer. The contact interface temperatures were measured by using a NEC-TH5104R thermal infrared imager. This high-speed tribometer can supply higher sliding speed (700m/min) and normal load (500N) than traditional tribometer does, so the friction and wear conditions are more similar to the practical cutting conditions.
Figure 1. The sketch of tribometer assembled on CA6140 turning lathe
182 Y.Z. Pan, X. Ai, J. Zhao and Y. Wan
The sliding speeds (450 m/min and 700 m/min) and the normal loads (100 - 400 N) were used in the friction tests. It took 5 - 10 min to achieve stable friction curve. The friction coefficients were calculated according to Coulomb friction formula. The friction tests were repeated for three times in the same normal load and sliding speed combination to obtain the average friction coefficients.
The sliding speed 700 m/min and the normal load 300 N were used in wear tests. The wear mass losses of cemented carbide samples were weighed using an electronic balance (resolution: 1mg), the weighing measurements were repeated for five times to obtain the average wear mass loss. The wear volume losses V=W/U, where W is the wear mass loss, U is the density of the cemented carbide.
2.3 High-Speed Milling Experiments
The high-speed milling experiments were performed under dry condition on a DMU-70V CNC machining centre with a 20KW electric motor, as shown in Figure 2. Two solid carbide end mills with three cutting flutes were used, namely WC-10Co and WC-12Co. The helix angle is 30q and tool diameter is 20mm. The rotational speed is 16000 r/min, the feed rate is 7200 mm/min, the axial and radial depth-of-cut are 2 mm and 7.5 mm. The flank wear length of tool was measured by a QHS-2005C stereomicroscope. The work-piece surface roughness was measured by MC020-2205 surface profilometer. Each flank wear value and roughness value is an average value depending on five measurements.
Figure 2. The experimental instrument
Analysis
3. Surface
The worn surface morphologies of cemented carbide samples were observed by means of a S-570 scanning electron microscope. The elemental diffusion behaviors of Co and Al were analyzed by means of EDS (energy dispersive spectroscopy) linear scanning analysis with a JXA-8800 electron microprobe.
High-speed Friction and Wear Behavior of Ultra-fine Cemented Carbide Cutting Tool 183 4. Results and Discussions
4.1 Friction and Wear Behavior
Coefficient
4.1.1 Friction
Both for friction tests performed in 450 m/min and 700 m/min, WC-10Co and WC-12Co have similar friction and wear properties, as shown in Figure 3 a and b. Both cemented carbides gave a lower friction coefficient at high sliding speed compared to low speed. For WC-10Co, at the low speed the friction coefficient fell from about 0.8 to 0.4 when the load increased from 100 to 400 N and at the high speed the friction coefficient fell from 0.6 to 0.3. The corresponding friction decrease was from 1 to 0.4 at low speed and from 0.8 to 0.35 at high speed. The higher the normal load and the sliding speed, the more energy input at the contact interface, the higher the friction temperature. Due to high friction temperature, the softening and plastic deformation of aluminum alloy took place at the friction interface, decreasing yield strength and friction coefficient.
a b
Figure 3. Friction coefficient vs. normal load: a. WC-10Co; b. WC-12Co
Temperature
4.1.2
Friction
When two surfaces become into sliding contact, the frictional heat produced at the interface can cause temperature rises rapidly. Surface and sub-surface temperatures generated by friction in tribological processes are important. As seen in Figure 4, the temperature arises abruptly during the first 1-5 min of sliding and reaches a constant value after about 10 min. The steady-state values of the temperature are 310 - 350 q C at 100 N and 430 - 500 q C at 300 N. Increasing the normal load leads to more energy input per unit time at the point of contact and increase of the surface temperature. WC-10Co has lower coefficient of thermal conductivity than WC-12Co owing to lower cobalt content, and as a result contact temperature is higher.
184 Y.Z. Pan, X. Ai, J. Zhao and Y. Wan
Figure 4. Variation of temperature during sliding process below contacting surface at the
normal load 100 N and 300 N
4.1.3 Wear
The wear volume losses of WC-10Co and WC-12Co increase with the increase of sliding time, as seen in Figure 5. There is an approximately linear relationship between the wear volume loss and the sliding time, which is in accordance with Archard wear equation[11]. The wear rate of WC-12Co is lower than WC-10Co, because WC-12Co with ultra-fine grain size of 0.3 - 0.5 P m has better mechanical properties than WC-10Co with micron-fine grain size of 0.6 - 0.8 P m and 10 wt% Co, as seen in Table 1.1. The mechanical properties of cemented carbide were found to be greatly dependent on the microstructures, such as WC grain size, contiguity of WC, Co content and the mean free path of Co binder phase. Minimizing the mean free path in the binder phase by decreasing the carbide grain size leads to an increase in hardness and resistance to plastic deformation in the binder phase[12]. The enhancement of bending strength and fracture toughness of WC-Co composite materials can be ascribed to deformation buffering effects of ductile cobalt binder. According to Evens wear equation[13], the higher the hardness and fracture toughness of brittle material, the lower the wear rate.
Figure 5. Wear volume loss vs. sliding time for WC-10Co and WC-12Co
High-speed Friction and Wear Behavior of Ultra-fine Cemented Carbide Cutting Tool 185 4.2 Wear Resistance of Cutting Tool
The relationships between the flank wear VB max and the cutting time, the work-piece surface roughness and the cutting time have been established, as shown in Figure 6 and Figure 7. In initial cutting time of 60 - 70min, the wear rate of cutting tool is high. From 70 min to 240 min, the cutting tools become into stable wear stage, where the wear rate is very low. The flank wear of cutting tool has become serious after 240 min. Moreover, the work-piece surface roughness increased with the cutting time and the flank wear. But in initial 20 min, the surface roughness fell with the increase of cutting time because the partial flank wear of cutting flute acted as amelioration blade. In high-speed milling of 7050-T7451 aluminum alloy, the chipping, the breakage and the fatigue wear become the main failure modes of the tool caused by the thermo-mechanical coupled non-uniform stress field. The excellent mechanical properties of WC-12Co tool, especially the higher bending strength and fracture toughness, improve effectively the wear resistance of WC-12Co tool to chipping, breakage and fatigue wear. It is the main reason why the wear rate and work-piece surface roughness machined by WC-12Co tool is lower than WC-10Co tool.
Figure 6. Flank wear vs. cutting time for WC-10Co and WC-12Co
Figure 7. Workpiece surface roughness vs. cutting time for WC-10Co and WC-12Co
186 Y.Z. Pan, X. Ai, J. Zhao and Y. Wan
4.3 Wear Mechanisms
When high-speed milling aluminium alloy with solid carbide end mills, the combined action of high temperature and high pressure along the rake face and the flank face can influence the physical properties of the cemented carbide and thus affect mechanisms of contact, deformation, friction and wear. The Co binder phase is partially removed from the WC grains by plastic deformation[14]. Some Co binder phases are extruded and adhered with Al in the sliding direction because Co and Al are soft and can form a thin layer on the sliding interface, as shown in Figure 8 a. The removals of Co binder phases destroy the steady WC sketch and some WC particles are pulled out from the cemented carbide body[15]. These WC fragments and hard inclusions in aluminium alloy are crushed between the contact faces between cemented carbide and aluminium alloy, and the abrasive wear traces occur on the worn surface of cemented carbide as shown in Figure 8 b.
a b
Figure 8. The wear patterns of cutting tool: a. Abrasive wear on the rake face; b. Adhesive
wear on the flank face
The elemental diffusion behaviours of Al and Co were analyzed by means of EDS linear scanning analysis along the direction perpendicular to WC-12Co worn surface. The concentration variations of Co and Al vary in different locations are presented. Co concentration in the region near the worn surface is obviously lower than that in the bulk material, as shown in Figure 9 a. Al has been found in the region near the worn surface, while no Al element was found in the chemical compositions of WC-Co cemented carbide, as seen in Figure 9 b. Not any diffusion of W element towards aluminium alloy is observed, because WC has better chemical durability than Co and Al. In the sliding wear tests and high-speed milling experiments, high pressure and high temperature promote the diffusion of Co element from cemented carbide to aluminium alloy, Al vice versa. The elemental diffusion behaviours of Co and Al change the chemical compositions and impair the hardness and strength of solid carbide end mills, that will lead to crater wear, chipping, notch wear and even breakage[16].
High-speed Friction and Wear Behavior of Ultra-fine Cemented Carbide Cutting Tool 187
a b
Figure 9. EDS linear scanning image of Co and Al along the perpendicular direction to the worn surface for WC-12Co: a. Co diffusion; b. Al diffusion
5. Conclusions
The high-speed friction and wear behaviors of ultra-fine grain cemented carbide against aluminum alloy have been investigated through high-speed friction and wear tests and high-speed milling experiments. The following conclusions can be drawn:
1. A special high-speed tribometer is assembled on a CA6140 turning lathe,
which can supply higher sliding speed (700 m/min) and normal load (500 N) than traditional tribometer does, so the friction and wear conditions are more similar to the practical cutting conditions.
2.The effects of sliding speed, the normal load and friction temperature on
the friction properties of cemented carbides were studied through high-
speed friction tests. The friction coefficient decreases with the increase of the normal load from 100 to 400 N and the sliding speed from 450 to 700 m/min.
3.The wear behaviors of cemented carbides were analysed by means of high-
speed wear tests and milling experiments. The results show that the wear rate and work-piece surface roughness machined by WC-12Co tool is lower than WC-10Co tool, because the former has a superior mechanical properties than the latter.
4.The main wear mechanisms of ultra-fine grain cemented carbide are
abrasive wear, adhesive wear caused by Co binder phase extrusion and plastic deformation of WC, accompanied with diffusion wear due to elemental diffusion behaviors of Co and Al.
188 Y.Z. Pan, X. Ai, J. Zhao and Y. Wan
6. Acknowledgements
This research was sponsored by the National Natural Science Foundation of China (50575126) and the Foundation for the Author of National Excellent Doctoral Dissertation of P. R. China (200231).
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宾语从句用法详解(例句丰富) 一、宾语从句的引导词 宾语从句通常由连词that和whether (if)、连接代词或连接副词以及关系代词型what引导：1. that引导 We believe that he is honest. 我们相信他是诚实的。 The doctor insists that I give up smoking医生坚持要我戒烟。 I suggest that we should go tomorrow. 我建议我们明天走。 I suggested that we should go the next day. 我建议我们第二天走。 We learnt from his letter that he was in Spain. 从他的信里我们了解到他在西班牙。 The seller demanded that payment should be made within five days. 卖方要求5日内付款。 2. whether / if引导 I don’t know whether he’ll arrive in time. 我不知道他是否能及时到。 I didn’t kn ow whether they liked the place. 我不知道他们是否喜欢这个地方。 I’ll see whether I can induce him to accept it. 我要看看我是否能劝他接受。 I asked her whether she agreed. 我问她是否同意。 He enquired if her parents spoke Spanish. 他问她父母是否讲西班牙语。 I wonder if it’s large enough. 我不知道它是否够大。 She di dn’t say if he was still alive. 她没说他是否还活着。 3. 连接代词引导 I don’t know who [whom] you mean. 我不知道你指谁。 Please tell me which you like. 告诉我你喜欢哪一个。 I’Il do whatever I can do. 我将做我所能做的事。 You can take whichever you like. 你爱拿哪个就拿哪个吧。 We’ll do whatever we can to save h im. 我们将尽我们所能来挽救他。 Take whichever seat you like. 你要坐哪个座就坐哪个座位。 Give it to whoever you like. 你把它爱给谁就给谁。 You don’t know what you are talking about. 你在说什么，你自己也不知道。 Tomorrow at this time we’ll know who is elected. 明天这时候我们就会知道谁当选了。
宾语从句 在句子中起宾语作用的从句叫做宾语从句.宾语从句分为三类:动词的宾语从句,介词的宾语从句和形容词的宾语从句. 时态：1·主句用一般现在时，从句可用任意时。 2·主句用过去时，从句用过去某个时态。 3·主句用过去时，从句是真理时，只用一般现在时。 1.宾语从句的连接词 从属连词 连接宾语从句的从属连词主要有that,if,whether. that引导表示陈述句的宾语从句,而if和whether引导表示“是否”的宾语从句. He told that he would go to the college the next year 他告诉我他下一年上大学. I don’t know if there will be a bus any more. 我不知道是否还会有公交车. Nobody knew whether he could pass the exam. 没人知道他是否会通过考试. 连接代词 连接代词主要有who, whom ,whose ,what ,whoever ,whomever ,whosever, whatever, whichever等. 连接代词一般指疑问,但what, whatever除了指疑问外,也可以指陈述. Do you know who has won Red Alert game? 你知道谁赢了这一局红警游戏吗? I don’t know whom you should depend on. 我不知道你该依靠谁. The book will show you what the best CEOs know. 这本书会告诉你最好的执行总裁该了解些什么. Have you determined whichever you should buy,a Motorola or Nokia cell phone? 你决定好是买诺基亚还是摩托罗拉的电话了吗? 连接副词 连接副词主要有when,where,why,how,whenever,wherever,however等. He didn’t tell me when we should meet again. 他没有告诉我什么时候我们能再见面. Could you please tell me how you read the new panel? 你能展示给我怎么用这个新的操作盘吗? N one of us knows where these new parts can be bought. 没有人知道这些的新的零件能在哪里买到. 2.动词的宾语从句
wear/dress/put on/in/with的区别 put on，动词短语着重于“穿”这一动作，即由没穿到穿这一动作的完成，意为“穿上、戴上””后接衣服、鞋帽等。例如： I want you to put on this coat and this hat. 我要你穿这件外套，戴这顶帽子。 Put on your heavy winter coat if you are going out. 如果你要出去，穿上你的厚冬衣。 wear 动词，“穿着；戴着”，表示状态，宾语可以是衣帽，也可以是饰物、奖章等。而dress, put on 一般不这样用。如： He seldom wears a watch. 他很少戴表。 He wears red T-shirt today. You’d better wear blue or bla ck pants with blown shoes. 穿棕色鞋子的时候, 最好要穿蓝色或黑色裤子。 Why does he often wear dark sunglasses? 他为什么经常戴着深色的太阳镜？ He was wearing a new jacket. 他当时穿着一件新夹克。
Such clothes are not often worn nowadays. 现在那样的衣服很少有人穿了。 dress 动词，常用人作宾语，不接“衣”作宾语，意为“给……穿衣服”。在表示“自己穿衣”时可说get dressed （= dress oneself）。当dress表示状态时，一般要用be dressed in形式。dress up强调着意打扮，意为“穿上盛装、乔装打扮”。例如： My son is now able to dress himself. 我儿子现在自己会穿衣服了。 It’s time to wake up and get dressed! 该起床穿衣服了。 She is dressed in a fur coat. 她穿着毛皮大衣。 She always dresses well. 她总是打扮得很漂亮 注：dress 还通常用于被动语态。如： The girl was poorly dressed. 这女孩衣着寒酸。 in是介词，表示“穿着、戴着”之意，后接表示衣服或颜色的词，着重于服装的款式或颜色。 它所构成的短语只能作表语或定语。 He was in a new black coat. 他穿着黑色的新外套。 The girl in red is my sister. 那个穿红衣服的女孩是我妹妹。 练习： It’s very cold outside. You’d bett er____________ your coat. He ____________ his coat and went out. Mr Black often ____________ white trousers. Lucy’s mother often ____________ a pair of glasses. Could you please help me ____________ the children? She was ____________ in a red coat. Do we have to ____________ up to visit her birthday party? Please ____________ your new coat.。 He’s ____________ a white shirt.。 He is ____________ on his blue hat. Could you ____________ the child for me? He cannot get ____________ (=dress himself). She was ____________ in a red coat. She ____________ the baby.
龙源期刊网 https://www.doczj.com/doc/1c8823336.html, 论情景模拟在培训中的运用 作者：赵今巾 来源：《高教学刊》2016年第14期 摘要：面对“新常态”下培训的新特点、新要求，如何在培训中创新培训方法，弥补传统的灌输式教学手段产生的“学”与“用”的断层缺陷，进化成启发式，体验式，实操式的培训方式是一个值得研究的课题。作者从起源、意义、应用和建议等几个方面探讨如何把握关键环节，更好的应用情景模拟教学。 关键词：情景模拟；员工培训；运用 中图分类号：G642 文献标志码：A 文章编号：2096-000X（2016）14-0097-02 Abstract： China's has entered a period of "new normal". It's means there are lots of more new characteristics and new requirements for the training program of leaders. How to innovate the training method？ How to make up for the defects of traditional training methods？ This deserves keen investigation and study. This paper discusses how to grasp the key links to apply the scene simulation teaching from the aspects of origin、 significance、application and suggestion. Keywords： scene simulation； staff training； application 公务员、国企事业单位的员工培训一直以培养具有公共精神的高效领导者为目标，其培养的核心是公共精神意识、高效领导能力、自我管理能力和创新能力，这也是当代“新常态”下领导干部必备的素质和能力。 培训的教学方式经过多年的发展和演变，也由传统的灌输式，进化成启发式，体验式，实操式，激发培训学员在培训中的主动性、实践性和创新性。区别于传统的讲座式教学，情景模拟法在近几年被广泛的应用，其生动性、实操性、趣味性深受培训学员的认可和喜爱。情景模拟已经成为培训中的“标配”培训手段，尤其是对于领导能力提升类课程，包括沟通能力、思维能力、写作能力、应变能力、公关能力、领袖能力、谈判能力等专题以及红色廉政教育类专题相比于传统的灌输式教学来讲，互动性更强的情景模拟更能彰显其衔接理论与实践的优越性，通过身临其境的新模式搭建课堂与社会的分隔的阶梯，缝补学与用空隙，对于增强培训效果作用重大。 一、情景模拟教学的起源 情景模拟教学起源于20世纪80年代在西方发展起来的情景认知理论（SituatedCognition），其早期研究来自杜威、维果斯基、列昂杰夫等学者，即“不是把知识作
宾语从句用法讲解 TYYGROUP system office room 【TYYUA16H-TYY-TYYYUA8Q8-
在句子中起宾语作用的从句叫做.分为三类:动词的宾语从句,介词的宾语从句和形容词的宾语从句. 时态：1·主句用，从句可用任意时。 2·主句用过去时，从句用过去某个时态。 3·主句用过去时，从句是真理时，只用。 1.宾语从句的 连接宾语从句的主要有that,if,whether. that引导表示的宾语从句,而if和whether引导表示“是否”的宾语从句. He told that he would go to the college the next year 他告诉我他下一年上大学. I don’t know if there will be a bus any more. 我不知道是否还会有公交车. Nobody knew whether he could pass the exam. 没人知道他是否会通过考试.
主要有who, whom ,whose ,what ,whoever ,whomever ,whosever, whatever, whichever等. 一般指疑问,但what, whatever除了指疑问外,也可以指陈述. Do you know who has won Red Alert game? 你知道谁赢了这一局游戏吗? I don’t know whom you should depend on. 我不知道你该依靠谁. The book will show you what the best CEOs know. 这本书会告诉你最好的该了解些什么. Have you determined whichever you should buy,a Motorola or Nokia cell phone? 你决定好是买诺基亚还是的电话了吗? 主要有when,where,why,how,whenever,wherever,however等. He didn’t tell me when we should meet again. 他没有告诉我什么时候我们能再见面. Could you please tell me how you read the new panel 你能展示给我怎么用这个新的操作盘吗
dress, wear, put on, have on, in的用法小结 都含有“穿、戴”之意，但用法不同。 in是介词，后接表示衣服或颜色的词，着重于服装的款式或颜色。它所构成的短语只能作表语或定语。例如： This is a picture of a young man in a black coat. 这是一张穿着黑色外套的年轻人的照片。这里in a black coat是young man的定语。 He is in a black nylon jacket today. 今天他穿着黑色尼龙夹克。 In a black nylon jacket在这个句子里作表语。 put on “穿上、戴上”，强调“穿”“戴”的动作，后接衣服、鞋帽等。例如： I want you to put on this coat and this hat. 我要你穿这件外套，戴这顶帽子。 Put on your heavy winter coat if you are going out. 如果你要出去，穿上你的厚冬衣。 pull on的意思也是“穿上”，带有“匆忙”的意思： It’s the weekend. I know you’re free. So pull on your jeans and come out with me. 现在是周末，我知道你有空。所以穿上你的牛仔裤，和我一起出去吧。 You’re late! Quickly pull on your clothes and leave! 你迟到了！快穿上衣服走吧！
wear “穿着；戴着”，表示状态，宾语可以是衣帽，也可以是饰物、奖章等。例如： You’d better wear blue or black pants with blown shoes. 穿棕色鞋子的时候, 最好要穿蓝色或黑色裤子。 Why does he often wear dark sunglasses? 他为什么经常戴着深色的太阳镜？ dress的宾语通常是人，意思是“给……穿衣服”。dress oneself 或get dressed表示给自己穿衣服。例如： My son is now able to dress himself. 我儿子现在自己会穿衣服了。 It’s time to wake up and get dressed! 该起床穿衣服了。 be dressed in 的意思是“穿着”，表示状态。 She is dressed in a fur coat. 她穿着毛皮大衣。 dress up的意思是“盛装打扮、乔装打扮”。 I’d like you to dress up for my birthday party tonight. 今晚我希望你为我的生日派对打扮打扮。 Young kids often dress up and have fun at Halloween. 万圣节前夜，小孩子通常都乔装打扮，玩得很开心。have on的意思是“穿着，戴着”，例如： If you're wearing black pants you should have on black shoes and a black belt. 如果你穿着黑色长裤的话，你应该要穿黑色的鞋子，配
一.宾语从句的定义 置于动词、介词等词性后面起宾语作用的从句叫宾语从句。宾语从句的语序必须是陈述语序。谓语动词、介词、动词不定式，v.-ing形式后面都能带宾语从句。有些形容词（afraid,sure,glad等）之后也可以带宾语从句。 二.宾语从句中引导词的用法 在复合句中作主句的宾语，引导词有： 连词：that (that 常可省略),whether, if 代词：who, whose, what ,which 副词：when ,where, how, why 等。 （一）that引导的宾语从句（在非正式场合that可以省略） 可跟that从句做宾语的动词有： say, think, insist, wish, hope, demand, imagine, wonder, know, suppose, see, believe, agree, admit, deny, expect, explain, order, command, feel, dream, suggest, hear, mean, notice, prefer, request, require, propose, declare, report 等。 例句：The boy believes that he will travel through space to other planets. 注意事项：当主句谓语动词是 think, believe, suppose, expect 等词，而宾语从句的意思是否定时，常把否定转移至主句表示。 例句：I don’t think it is right for him to treat you like that. 在以下情况中that不能省略 1.当句中的动词后接多于两个由that引导的宾语从句时，第一个that可省，但后 面的that不可省。 例句：He said (that) you were too young to understand the matter and that he was asked not to tell you. 2.当主句的谓语动词与that宾语从句之间有插入语时，that一般不可省。 例句：Just then I noticed, for the first time, that our master was wearing his fine green coat and his black silk cap. 3.当that从句是双宾语中的直接宾语时，that不可省。 例句：I can’t tell him that his mother died. 注意事项：许多带复合宾语的句子，that引导的宾语从句经常移到句子后部，而用it作形式宾语。
一、clothes 的用法 1. 是衣服的统称，不仅包括coat, shirt, dress 等这样的“衣服”，而且还包括trousers, socks 等穿在身上的所有东西。 2. 表示“衣服”，是一个没有单数形式的复数名词，其前不可加不定冠词，也不可加数词，但可用some, these, those, many, (a) few 等词修饰。如： I need to buy some clothes. 我需要买些衣服。 These clothes wash well. 这些衣服经洗。 You look rather shabby in those clothes. 你穿着那种衣服显得很寒酸。 I don’t have many clothes for summer. 我夏天穿的衣服不多。 As a student she lived very economically, rarely going out and buying very few clothes. 作为学生，她过得很节约，很少外出，也难得买衣服。 3. 虽然不受数词的修饰，但使用代词时可用ones。如： When he got a job in a bank, he had to wear formal clothes instead of informal ones. 他在银行谋了份工作后不得不把非正式衣服换成正式衣服。 4. 可受某些名词修饰，表示不同用途的衣服，如school clothes（校服），sports clothes（运动服），work clothes（工作服），play clothes（休闲服）等。 它还可以受季节名词修饰，表示不同季节穿的服装，如spring clothes（春装）、summer clothes（夏装）、autumn clothes（秋装）、winter clothes（冬装）。 另外还有men’s clothes（男装），women’s clothes（女装），children’s clothes （童装）等，但是“婴儿服装”却是baby clothes，通常不说babies’ clothes。 5. 表示一套衣服，可以借助suit或set。如： George is wearing a new suit of clothes. 乔治穿着一套新衣服。 I’m going to take a set of clean clothes with me. 我要带一套干净的衣服。 二、clothing的用法 1. 表示“衣服”的总称，是一个不可数的集合名词。如： We need warm clothing for the winter. 我们需要暖和的衣服过冬。
军事模拟训练的方法、特点及其不足 模拟训练又称模拟仿真，就是在军事方面进行建模，然后利用仿真的技术进行模拟战局、战略、战术的方法。这种方法应用系统论的观点，并且利用数学建模等多种 建模方法。在实践中，模拟训练对于军事作战的指挥有着很大的指导作用。利用模拟技术特别是计算机技术，以作战原则、作战结构为基础，模拟逼真的战场环境和敌军行动，把行之有效的战法融人模拟系统，用模拟训练的方法改变训练的过程和方式，能极大提高训练质量和训练效益。 一、模拟训练的方法 1、作战模拟 早期的作战模拟定义如下：“在以沙盘和地图表示地形地貌、以标示器表示军队和武器配置的战场模型上，利用反映实战条件约束的若干行动规则，扮演交战双方的指挥官和参谋人员以下棋方式进行策略运筹的对抗”。这种模拟至今仍在各国军队中大量使用，也就是现在军事演习中沙盘的作业演习。 随着计算机技术的发展，作战模拟也达到新的阶段，计算机仿真、交互式对抗模拟相继出现，作战模拟的应用范围也从对作战结果的预测与判定，作战过程的推演与 评价扩展到了从一个军事行为的策划到它的实施终了的全过程，作战模拟的定义也跟着发生了变化。目前对作战模拟的定义五花八门，还没有形成一个权威的定义，这里 只说一下我自己对作战模拟的认识，可能并不充分，所谓的作战模拟就是运用各种手段，借助于模型和和仿真器对包括两支或多支对抗力量的军事冲突，按事先给定的规 则进行的演练。 在进行的模拟斗中，指挥官完全置身于一个由多军兵种部队协同作的空间内，从而使指挥官摆脱二维空间的思维枷锁，使指挥官挑选最佳方案提供依据，指挥艺术得到更充分的发挥。 2、虚拟现实 虚拟现实是近年来出现的高新技术，也称人工环境。虚拟现实是利用电脑模拟产生一个三维空间的虚拟世界，提供使用者关于视觉、听觉、触觉等感官的模拟，让使用者如同身历其境一般，可以及时、没有限制地观察三度空间内的事物。90年代初，一些发达国家开始将其应用于军事训练模拟。利用虚拟现实技术进行训练，训练者不是被动的支观察计算机图表或与实际景物有一定差距的图象，而是在一个虚拟的十分逼真的三维世界中，在视觉、听觉、触觉等人类全部感觉的作用下，犹如身临其境股的全身心地投入到真实的训练中。目前虚拟现实技术已受到许多发达国家的重视，美军认为虚拟现实技术将成为21世纪的主要训练方式。 二、模拟训练的特点 1、真实性 模拟训练能够构造真实环境。用计算机生成的一种特殊环境，作战人员可以通过使用各种特殊装置将自己“投射”到这个环境中，并操作、控制环境，实现军事对抗的目的。 2、经济性 模拟训练能够减少训练费用。如果进行实战训练，需耗费大量经费来部署人员和相关装备，在模拟训练中可以完全省去。同时，模拟训练中还可以省去在野战训练中所需的油料、弹药、生活用品等供给品的费用，也可以省去大量的交通运输等相关费用。 3、高效性 模拟训练能够缩短训练时间。如使用射击训练装置进行模拟训练减少了进出靶场的时间，使用近距离战斗战术训练装置展开各类作战行动，比进行野战训练可大大缩短训练时间。一项军事演习要有足够的时间准备，而模拟训练能够保证时间的大幅度的减少。 4、环保性 模拟训练能够避免环境破坏。模拟训练不会造成任何环境污染，既不会产生诸如车辆碾压、油料废气、炸弹爆炸碎片、空气水源污染等破坏性后果，也不会因为火炮或其它武器射击引发事故，或因为高性能武器装备的运行而产生噪音污染。 5、安全性 训练安全是全军训练关注的重要因素。实兵训练中，不管是战场机动，还是对抗演习，潜在的安全威胁不可避免，甚至会出现人员伤亡的现象。然而，在模拟训练中，演习双方即使进行几百或上千回合的对抗也不会发生任何伤亡。 三、模拟训练的不足 1、模拟训练效果不完全真实 模拟终究还是模仿，虽然现在的科学技术使得模拟训练越来越逼真，越来越接近真实的战场，但有很多东西是模拟不出来的，就像指挥官和作战人员的思想，这种随机的人类灵感体验是计算机无法计算出的。同时，模拟系统产生的视觉运动信号和人的感觉之间存在差异，
fun 用法详解 1. It’s fun后接不定式或动名词均可,意思基本相同. Eg;：It’s great fun sailing a boat.= It’s great fun to sail a boat. 扬帆驾舟十分有趣. 2. 表示做某事很开心,可用have (there is) fun (in) doing sth. Eg：We had fun riding our bicycles to the beach today. 我们今天骑自行车去海滨玩得很开心. There’s no fun in spending the evening doing nothing. 晚上无事可干,很无聊. 3. 以下各例中的fun虽用作表语,但仍为名词,而非形容词,故可用great, much, a lot of等形容词修饰,而不用very等副词修饰. 如：She’s great fun to be with. 同她在一起很有意思. Why don’t you come with us? It’ll be great fun. 干吗不同我们一起去呢?很有趣的. 下面一例中fun前的more为much的比较级.如：It is more fun to go with someone than to go alone. 偕伴同去比自己独自去好玩. 4. 注意for fun（为了高兴,为了好玩）与in fun（不是当真的,闹着玩的,开玩笑地）意不同.比较： I am not saying it for fun. 我说这话并不是在开玩笑. He said so only in fun. 他这样说只是开开玩笑. 实用词汇： dress,?wear,?put?on,?have?on,?in的用法小结 dress,?wear,?put?on,?have?on,?in?都含有“穿、戴”之意，但用法不同。? 1.in是介词，后接表示衣服或颜色的词，着重于服装的款式或颜色。它所构成的短语只能作表语或定语。例如：? This?is?a?picture?of?a?young?man?in?a?black?coat.? 这是一张穿着黑色外套的年轻人的照片。这里in?a?black?coat是young?man的定语。He?is?in?a?black?nylon?jacket?today.? 今天他穿着黑色尼龙夹克。? In?a?black?nylon?jacket在这个句子里作表语。? 2.put?on??“穿上、戴上”，强调“穿”“戴”的动作，后接衣服、鞋帽等。例如： I?want?you?to?put?on?this?coat?and?this?hat.? 我要你穿这件外套，戴这顶帽子。 Put?on?your?heavy?winter?coat?if?you?are?going?out.? 如果你要出去，穿上你的厚冬衣。 3.wear?“穿着；戴着”，表示状态，宾语可以是衣帽，也可以是饰物、奖章等。例如：You’d?better?wear?blue?or?black?pants?with?blown?shoes.?穿棕色鞋子的时候,?最好要穿蓝色或黑色裤子。? Why?does?he?often?wear?dark?sunglasses?? 他为什么经常戴着深色的太阳镜？ 4.dress的宾语通常是人，意思是“给……穿衣服”。 dress?oneself?或?get?dressed表示给自己穿衣服。例如：? My?son?is?now?able?to?dress?himself.? 我儿子现在自己会穿衣服了。 ?It’s?time?to?wake?up?and?get?dressed!?
宾语从句用法讲解 在句子中起宾语作用的从句叫做.分为三类:动词的宾语从句,介词的宾语从句和形容词的宾语从句. 时态：1·主句用，从句可用任意时。 2·主句用过去时，从句用过去某个时态。 3·主句用过去时，从句是真理时，只用。 1.宾语从句的 连接宾语从句的主要有that,if,whether. that引导表示的宾语从句,而if和whether引导表示“是否”的宾语从句. He told that he would go to the college the next year 他告诉我他下一年上大学. I don’t know if there will be a bus any more. 我不知道是否还会有公交车. Nobody knew whether he could pass the exam. 没人知道他是否会通过考试. 主要有who, whom ,whose ,what ,whoever ,whomever ,whosever, whatever, whichever等. Document number：NOCG-YUNOO-BUYTT-UU986-1986UT
一般指疑问,但what, whatever除了指疑问外,也可以指陈述. Do you know who has won Red Alert game 你知道谁赢了这一局游戏吗 I don’t know whom you should depend on. 我不知道你该依靠谁. The book will show you what the best CEOs know. 这本书会告诉你最好的该了解些什么. Have you determined whichever you should buy,a Motorola or Nokia cell phone 你决定好是买诺基亚还是的电话了吗 主要有when,where,why,how,whenever,wherever,however等. He didn’t tell me when we should meet again. 他没有告诉我什么时候我们能再见面. Could you please tell me how you read the new panel 你能展示给我怎么用这个新的操作盘吗 N knows where these new parts can be bought. 没有人知道这些的新的零件能在哪里买到. 2.动词的宾语从句 大多数动词都可以带宾语从句 We all expect that they will win , for members of their team are stronger. 我们都预料他们会赢,因为他们的队员更强壮. He told us that they would help us though the whole work. 他告诉我们在整个工作中,他都会帮忙的. 部分“动词+副词”结构也可以带宾语从句 I have found out that all the tickets for the concert have been sold out. 我发现这场音乐会的所有票都卖光了. Can you work out how much we will spend during the trip
宾语从句的讲解 一．宾语从句的定义 在句中充当宾语的句子是宾语从句。例如： I hope that I can see you again one day. 我希望有一天我能再见到你。 例句中，动词hope后跟宾语从句，充当hope的宾语，引导词是that。 二．不同引导词引导的宾语从句 （一）由that引导的宾语从句 that引导的宾语从句为陈述句。that只起连接作用，在从句中不做句子的成分， 无实意，所以在口语中常被省略。 例：I told him (that）he was wrong.我告诉他他错了。 试一试： 我希望你明天可以来。______________________________________________ 我敢肯定你会通过这个考试。________________________________________ 注意：在think, believe, suppose, 等动词引起的宾语从句中，当宾语从句表示否定时，本身不用否定形式，否定需要前置。 例如：我认为你做的不对I don’t think that you are right. 试一试： They believe. They won’t lose the game. (合成一句) ____________________________________________________________ I think that we will be late. (改为否定句) _____________________________________________________________ (二) 由if/whether引导的宾语从句 由whether(if)引导的宾语从句，实际上是一般疑问句演变而来的。if/whether在句中的意思是“是否”。而且从句原来的疑问语序要成陈述语序。 例如: I don’t know if/whether he lives here. 例句中，if/whether 引导从句he lives here。（从句原来的疑问式是Does he live here? 变成陈述式，将助动词does去掉，动词保持原有的单三形式lives） 试一试： Are you a student? (变为陈述式)_________________________________ Does your mother get to work by bus? （变为陈述式）_________________________ Has he finished his homework? （变为陈述式）_________________________________ Did they go to the park yesterday?（变为陈述式）______________________________ I wonder. Will they come to my party? (合成一句：我想知道他们是否会来。) __________________________________________________ I don’t know. Has he learned English? (合成一句：我不知道他是否学过英语。) _____________________________________________________ The teacher asks us. Did we finish our homework?( 合成一句：老师问我们是否完成了作业。) ________________________________________________________ 注意： 1.只能用whether，不能用if的情况 ①在介词的后面 例句：I’m thinking about whether we should go to see the film. 我正在考虑我们是否该去看电影。
实战与模拟训练的区别理论来源于实践。研究作战问题需要实战化训练作为重要的实践平台，以检验作战设计和新质战斗力，探索打赢未来战争的观念模式与思维框架。军事训练越实战化，越逼近未来战争，越能为作战问题研究提供更好的实践基础。未来战争仍处于想象和设计中，充满虚拟与不确定性，作战问题研究因而更加需要实战化训练的“体验厅”，增强对未来作战的感性认识。训练越强调实战化，越逼近未来战争，越能把未来战争由虚变实，为作战问题研究提供强有力的实践基础。 世界军事强国研究作战问题，尽管有一些战争实践作支撑，仍不断强化实战化训练在探求未来战争中的链条作用。只有通过实战化训练，才能弥补作战问题研究中的实战缺项。研究作战问题，实践性既是价值体现，也是重要基石。现在作战问题研究某种程度上存在的低层次徘徊等现象，也使许多一般性的描述很难下沉，落实到部队的每一个战斗细胞，只有将实战化训练作为重要的实践方式，成为深化作战问题研究的切入点和重要抓手，才能使一些重要的具体作战问题。 同样当我们在现在的条件下我们需要进行实战的演练以应对火场可能发生的各种意想不到的情况，如发生爆炸、空气呼吸器压力不足、建筑倒塌和战士体力不足等。而且这
也是模拟训练不容易考虑到的情况。但是，模拟训练同样也有不可或缺的作用。 新的训练应瞄准未来作战保障需求，注重实时感知训练、资源可视训练、精确配送训练和全程调控等训练，创新发展新的保障方式，强化提高信息化条件下的保障能力。美军1996年发布《2010年联合构想》、《2020年联合构想》，解决的是未来作战怎么打的问题，然后才有了武备的发展、军队组织结构的调整和训练转型等问题。作为追求超越的后发者，我军一方面必须加强研究未来战争的本质属性、外军对未来战争的认识、近期发生的高技术局部战争等，形成未来仗怎么打的共识，并对机械化战争的战术战法进行具体筛选；另一方面更应根据信息化战争的基本特点和规律，区分战略战役战斗不同层次，解放思想、大胆创新，从源头上把握未来作战的主动权。同样我们火场作战更需要模拟训练，通过模拟训练我们能对火场进行更好地指挥、全局的把握、火势的发展方向和力量的调度指挥。 我认为作为消防的一员我们要尽可能的做好每一点，既要做好实战演练了解辖区内的重点单位的建筑特点和可能发生的意外，又要进行模拟演练已对事故发生后的有效、快速、准确的进行行动。 我认为随着经济建设的不断发展，火灾危险因素也不断增加，在消防部队与火灾斗争中，总是希望用最短的时间，
put on, pull on, wear, have on , dress的用法区别(1)put on 和pull on 穿上；戴上。相当于及物动词，以衣物作宾语，着重于穿、戴的动作。put on 为普通用语；pull on多用于穿袜子、戴手套或比较随便地穿上。 ①It’s cold outside.You’d better put on your hat.外面很冷，你最好戴上帽子。 ②She put /pulled on her coat and went out of the room hurri edly.她穿上大衣，匆忙地走了。 (2)wear 和have on 穿着；戴着。相当于及物动词，有衣物作宾语，着重于穿、戴的状态。have on不用于进行时态。 ①He always wears/has on black shoes.她一直穿着黑鞋。 ②She is wearing/has on a red coat她穿着红大衣。 (3)dress 穿；戴。可用作及物动词，以人作宾语，即dress sb.（给某人穿衣）；也可用作不及物动词。既可强调动作，又可表示状态，表示状态时常用be dressed in 结构。此外dress还可用作名词。 ①Mary is dressing her daughter.玛丽正给她女儿穿衣服。 ②She usually dresses well.她总是穿得很好。 ③He is dressed in a black jacket.他穿着黑上衣。
(4)in 穿着；戴着。是介词，以衣物或表示颜色的名词作宾语，表示状态。构成的介词短词可作表语或定语。 ①My brother is in a blue jacket.我弟弟穿着蓝上衣。 ②The boy in a blue jacket is my brother.穿蓝上衣的孩子是我弟弟。 ③My brother is in blue.我弟弟穿着蓝衣服。