Yang Gao School of Physics and Engineering, Key Lab of Materials Physics,
Zhengzhou University,
Zhengzhou450052,China
e-mail:641303569@https://www.doczj.com/doc/3513791150.html,
Zhong-Xia Liu1 School of Physics and Engineering, Key Lab of Materials Physics,
Zhengzhou University,
Zhengzhou450052,China e-mail:liuzhongxia@https://www.doczj.com/doc/3513791150.html,
Pei-Chung Wang Manufacturing Systems Research Lab,
General Motors Research
and Development Center,
30500Mound Road,
Warren,MI48090 e-mail:pei-chung.wang@https://www.doczj.com/doc/3513791150.html, Effect of Aging on the Strength
of Clinching Galvanized SAE1004 Steel-to-Aluminum AA6111Joints Mechanical clinching method has been shown to be a feasible alternative to self piercing riveting(SPR)for joining dissimilar materials,particularly for vehicle assemblies made in aluminum-to-steel.While a great deal of effort has been focused on studying the pro-cess development,there is an urgent need to understand the effects of aged aluminum on the strengths of the clinching steel-aluminum joints.To evaluate exactly the in?uence of mechanical properties of aged aluminum alloy on the strength of the clinching joint, 1.0mm thick AA6111-T4aluminum was?rstly solution heat-treated at550 C for30min followed by nature ageing treatment for various times and then clinching to0.7mm thick galvanized SAE1004steel with SKB die.The section parameters and strength of the clinching joints were measured.The effect of mechanical properties of aged AA6111-T4 aluminum was analyzed using an analytical model.The results showed that aged alumi-num affected little the clinchability but in?uenced the section parameters and strength of the clinching workpieces.The strength of the clinching SAE1004-to-AA6111-T4joints increased with increasing the strength of AA6111-T4aluminum.This can be primarily attributed to the fact that the strengthening AA6111-T4aluminum resulted in larger re-sidual press stress developed during the clinching.[DOI:10.1115/1.4027596] Keywords:aged aluminum alloys,clinching aluminum-steel joint,section parameters, joint strength,analytical model
1Introduction
Automotive manufacturers are faced with increasing pressure to reduce vehicle mass and thereby improve the economy,reduce emissions,and to enhance the vehicle safety and performance. Therefore,more and more vehicle structures are built using dis-similar materials such as steel,aluminum and magnesium[1]. Because of the different melting points and thermal conductivity between steel and aluminum alloys,it is dif?cult to join them by the fusion techniques[2]and therefore alternative methods are urgently needed.New generation of mechanical joining techni-ques for thin metal sheets have been developed,such as self-piercing riveting[3–7],friction stir welding[8,9],hybridized fric-tion stirring-riveting[10,11],bonding[12],and clinching.Among the various joining methods,mechanical clinching shown in Fig. 1has the ability to join dissimilar materials[13–16].It has been shown that clinching is environmentally friendly due to low energy requirements,low-noise,no fume emissions and typically involves little heating compared to resistance spot welding[15] and more ef?cient in mass production compared to friction stir weld[17]even though the strength of the clinching joint is lower than those of self-piercing riveted and friction stir joints.In addi-tion,it has the advantage of low running costs without a rivet if tool service life is guaranteed[18].To facilitate the use of me-chanical clinching for lighter,stronger and more cost-effective ve-hicle structures,design guidelines,and predictive capabilities for clinching parts design are required.Successful implementation of mechanical clinching requires the knowledge of issues related not only to processing but also joint performance.
Figure1schematically shows the TOX clinch model[19].As shown,the joining punch moves to the die and exerts a press force on the workpieces to be joined.The material of the workpieces is placed below the punch and penetrated down to the die bottom. Then,the material is upset between the punch and die such that a radial material?ow occurs toward the outside.The die lamellae opening during the upsetting phase controls the radial material ?ow such that an undercut is created between the materials to be joined on the punch and die side.The main geometrical parame-ters describing a clinching joint are shown in Fig.2.As shown, undercut between the upper and lower workpieces,neck thickness of upper workpieces and bottom thickness are three primary sec-tion parameters.The undercut and neck thickness determine the strength of the clinching joint while the bottom thickness can be used to monitor the quality of the joint[20].To improve the strength of mechanical clinching joint,it is important to increase the undercut as well as the neck thickness of the upper sheet[21]. In general,three basic modes of failure have been observed when a joint is loaded[21–23].The Insuf?cient undercut and neck thickness may result in the joints failed in the button pull-out mode(shown in Fig.3(a))and neck cracking mode(shown in Fig. 3(b)).It has been shown that button pull-out failure mode is the separation of the upper and lower workpieces mainly due to minor geometrical interlocking of the mechanical clinching joint caused by insuf?cient deformation,while neck cracking failure mainly resulted from an insuf?cient amount of material in the neck of upper workpieces,which can attribute to the smaller clearance of the tool diameter or deeper die depth of die which leads to exces-sive elongation in the region of the joint neck,causing the forma-tion of a crack[22].Both result in the joints having low joint strengths.
If there is a good balance between the neck thickness and undercut,a mix failure mode(shown in Fig.3(c))with a combina-tion of button pull-out and neck cracking may occur.In this fail-ure mode,one edge of the joint fails,whilst the other is deformed in the?rst stage.Subsequently,the workpieces separate without any further fracture.Because of the joint subsequently opens as a press-stud during the workpieces are deformed,a high shear load can be accommodated with this failure mode.Therefore,the joints
1Corresponding author.
Contributed by the Manufacturing Engineering Division of ASME for publication
in the J OURNAL OF M ANUFACTURING S CIENCE AND E NGINEERING.Manuscript received
December29,2013;?nal manuscript received April29,2014;published online May
21,2014.Assoc.Editor:Donggang Yao.
Journal of Manufacturing Science and Engineering AUGUST2014,Vol.136/041016-1
Copyright V C2014by ASME
failure in a mixed failure mode has been evaluated the best mode and have the desired joint strength [23].
The experimental and various numerical investigations showed that the strength of the clinching joint was closely related to the punch force,section parameters of joints [21,24–28],geometric parameters of punch and die [21,22,29–31],thickness and me-chanical properties of the clinching workpieces [32–35].Though a majority of analytical models were developed to estimate the strength of the clinching joints [36–41],the variation in material properties of the lower sheet on the clinchability was rarely stud-ied.Lee et al.[21]proposed Eqs.(1)and (2),for estimating the strengths of the joints failed by neck cracking and button pull-out,respectively.According to Eqs.(1)and (2),the strength of the clinching joint is determined by the mechanical properties of the upper sheet,punch radius R P ,neck thickness t N ,undercut t U ,and friction coef?cient l (as shown in Fig.2).
F N ?r f áA N ?p 2R P t N tt 2N àá
ár f (1)F B ?p á2R P t N tt 2N à
áár y á1tl =tan a l =tan a 1àt N
t U tt N
!l =tan a (2)
It is obvious that Eqs.(1)and (2)ignore the effect of mechanical properties of the lower sheet.In fact,as a mechanical joining method,both upper and lower sheets involve the severe local plas-tic deformation.The mechanical properties of the lower sheet may change its deformation resistance and formability,which might have an in?uence on the strength of the clinching joint.Therefore,to evaluate the strength of the clinching joints,the in?uence of the mechanical properties of the lower sheets must be considered.As the workpieces to be joined may subject to various manufacturing processes (e.g.,stamping,trimming,etc.)prior to clinching,the workpieces often are held various times at ambient temperature after solution treatment (T4condition).As a result,the material may age,and thus the initial state (such as,strength,ductility)of the clinching workpieces may change,which may result in a variation of the strength of the clinching joint.There-fore,the development of clinching process will require detailed understanding on the effect of aging on the joint strength of the clinching joints.
In this study 0.7mm thick galvanized SAE1004steel and 1.0mm thick aluminum AA 6111-T4were selected as upper workpiece and lower workpiece,respectively,to investigate the effect of mechanical properties of the lower workpiece on the strength of the clinching joints.To change the mechanical proper-ties of the lower sheet,AA6111-T4aluminum was ?rst treated with solution treatment and then aged for various times at ambient temperature.Then,galvanized SAE1004steel and aluminum AA6111-T4aged with various times were clinching.The effect
of
Fig.3Failure modes of the mechanical clinching joint:(a )button pull-out,(b )neck cracking,and (c )mix
failure
Fig.1The principle of clinching with a round tool [19
]
Fig.2Primary section parameters of the clinching joint
Table 1Chemical composition of galvanized SAE1004steel (mass %)
C
Mg P S Fe Galvanized SAE1004steel
0.02–0.06
0.35max
0.03max
0.035max
Bal.
Table 2Chemical composition of AA6111-T4aluminum (mass %)
Si
Mg Cu Mn Fe Zn Ti Cr Al AA6111-T4aluminum
1.15
0.72
0.70
0.27
0.26
0.16
0.15
0.11
Bal.
Table 3Mechanical properties of SAE1004steel and AA6111-T4
Yield strength
(MPa)
Tensile strength
(MPa)
Elongation (%)SAE1004Steel 151.12288.7843.84AA6111-T4Aluminum
151.27
290.79
23.45
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mechanical properties of the lower aluminum workpiece on the section parameters and strength of the joints were measured.Finally,an analytical model was proposed to elaborate the effect of mechanical properties of the aged aluminum on the strength of the clinching steel-aluminum joints.
2Experimental Procedure
2.1Material.0.7mm thick galvanized SAE1004steel and 1.0mm thick aluminum AA6111-T4were used.Per the manufac-turers’data sheet,the chemical compositions and mechanical properties of galvanized SAE 1004steel and aluminum AA6111-T4are given in Tables 1–3,respectively.
2.2Heat Treatment of AA6111-T4Aluminum.Since alu-minum AA6111-T4would be naturally aged in the ambient environment,it was heat-treated ?rst in solution at 550 C for 30min to make that the material properties are consistent.Then,solution heat-treated AA6111-T4was natural aged for various times (i.e.,0,5,10,15,20days)at ambient temperature.
2.3Mechanical Properties Tests.To study the variations of the mechanical properties of AA6111-T4aluminum sheets after solution-natural aging,the mechanical properties were measured by MTS 810materials test system according to ASTM E8-04.Static tests were performed at room temperature at a stroke rate of 2mm/min.Standard tensile specimens shown in Fig.4were used.The engineering strain versus stress curves was automatically recorded.Three replicates were performed,and the average yield strength,tensile strength and elongation were reported.
2.4Joint Fabrication.To investigate the effect of the me-chanical properties of AA6111-T4aluminum on the strength of the clinching joints,lap-shear specimens with an overlap length of 15mm shown in Fig.5were fabricated using TOX CEB15Hy-draulic and Pneumatic Clinch System with TOX@SKB die as shown in Fig.6.As shown,the SKB die has both solid and ?exi-ble segments.The clinching workpieces and the punch are cen-tered by the ?xed segments,and thereby guaranteeing that the joint formation is perfectly concentric.The mobile elements between the solid segments allow an undercut of the materials in the joint.The coupons with a size of 38.1?126mm which simu-lates the joint pitch for automotive components were machined from 1.0mm thick aged AA6111-T4aluminum and 0.7mm thick galvanized SAE1004steel workpieces.The rolling direction is parallel to the longer axis of the coupons.In all cases,galvanized SAE1004steel was placed as the upper workpiece while the aged aluminum AA6111-T4was placed as the lower workpiece.Before fabricating a test sample,a proper set of joining process parame-ters must be determined.This is a trial and error process.Utilizing existing guidelines for joint quality,satisfactory process parame-ters are determined by a combination of visual inspection and static joint performance.Table 4lists the process parameters for the clinching process.The joint strength was evaluated by
the
Fig.4Con?guration of specimen for tensile testing (dimen-sion in
mm)
Fig.5Con?guration of a lap-shear joint (dimension in
mm)
Fig.6Con?guration of TOX@SKB dies
Table 4Process parameters used for clinching of 0.7mm thick galvanized SAE1004and 1.0mm thick AA6111-T4aluminum Punch diameter (mm)Die diameter (mm)
Die depth (mm)Punch force (kN)
5.6
8.2
1.2
48
Fig.7Effect of aging on the mechanical properties of AA6111-T4aluminum
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peak load.Three replicates were performed,and the average peak loads were reported.
2.5Characterization of Clinching Steel-to-Aluminum Joints.To investigate the quality of the clinching steel-to-alumi-num joints,the joints were characterized by three section parame-ters,namely,undercut,neck thickness,and bottom thickness.The joints were sectioned and examined by optical microscope to mea-sure the section parameters.Three specimens were examined for each condition and three replicates for every section parameter were measured and the average values were reported.
2.6Quasi-Static Testing.Quasi-static tests were performed by loading each specimen to failure in a MTS 810tester.To mini-mize the bending stresses inherent in the testing of lap-shear specimens,?ller plates were attached to both ends of the sample using masking tape to accommodate the sample offset as shown in Fig.5.Load versus displacement curves were obtained as the specimens were loaded at a stroke rate of 2mm/min.Three repli-cates were performed,and the average peak loads were reported.Postfailure analysis was performed with optical microscopy to study the failure mechanisms.
3
Results and Discussion
3.1Effect of Aging on Mechanical Properties of AA6111-T4Aluminum.To investigate the effect of aging on the mechani-cal properties of AA6111-T4aluminum,AA6111-T4aluminum was solution-aged for various times at ambient temperature and then tested quasi-statically.Figure 7presents the effect of aging time on the mechanical properties (i.e.,tensile strength,yield strength,ductility,and yield ratio (i.e.,the ratio of yield strength to tensile strength)of AA6111-T4aluminum.As shown,with an increase in natural aging time,the tensile strength,yield strength,and yield ratio increased while the elongation decreased.The changes were particularly pronounced for aging time between 0and 5days.
The strengthening of AA6111-T4aluminum from natural aging primarily resulted from the block of the solute atom clusters to the motion dislocation [41].As the aging time increased,more
solute
Fig.8Effect of aging time on the cross-section of clinching 0.7mm thick SAE1004to AA6111-T4aluminum joints:(a )0,(b )5,(c)10,(d )15,and (e )20
days
Fig.9Effect of yield strength of aged AA6111-T4aluminum on the section parameters of the clinching 0.7mm thick SAE1004to 1.0mm thick AA6111-T4joints
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atoms were aggregated by diffusion to form the cluster and the size of clusters increased in the ambient condition.As a result,the strength of aged aluminum increased with an increase in aging time.As the aging time exceeded 5days,the short range solute atoms had been consumed to form the clusters.The formation and growth of new clusters relied on the aggregation of long range sol-ute atoms.Since low diffusion ability of solute atoms in the ambi-ent condition made it dif?cult for the long range atoms to aggregate and form the clusters continuously,the solute cluster barely grew after aging 5days.Consequently,the strength of aged AA6111-T4aluminum increased slightly.These results suggest that the natural aging increased the strength and decreased the ductility of AA6111-T4aluminum.
3.2Section Parameters of Clinching Galvanized SAE1004Steel-Aged AA6111-T4Aluminum.Since natural aging affected the mechanical properties of aluminum AA6111-T4,one concern is if the variation of the material properties would affect the qual-ity of the clinching joints.To examine the joint quality,clinching 0.7mm thick galvanized SAE1004steel (upper sheet)and 1.0mm thick aged AA6111-T4aluminum joints (lower sheet)were fabri-cated with a 1.2mm depth SKB die under a punch force of 48KN.The clinching joints were cross-sectioned and the results are
shown in Fig.8.It can be seen from Fig.8that steel and aluminum workpieces were interlocked intimately.
Experimental observations indicated that the section parame-ters,such as the undercut,neck thickness,and the residual bottom thickness,shown in Fig.2,play an important role in affecting the joint strength [24–28].To examine if the aging of AA6111-T4aluminum affects the joint strength,the correlation among the yield strength,yield ratio and section parameters (i.e.,undercut,neck thickness,and bottom thickness)were plotted and shown in Figs.9and 10.As shown,with the increase in yield strength (Fig.9)and yield ratio (Fig.10)of aged aluminum AA6111-T4,the undercut of the clinching joint decreased while the bottom thickness increased.But the change in neck thicknesses was little.Apparently,a decrease in undercut and an increase in residual bot-tom thickness were primarily attributed to both low ductility and high yield stress and yield ratio of aged aluminum,restricting the deformation and radial material ?ow during the clinching.3.3Strength of Clinching Galvanized SAE1004Steel-Aged AA6111-T4Aluminum.Clinching 0.7mm thick galvanized SAE1004steel and 1.0mm thick aged AA6111-T4aluminum joints were tested quasi-statically and the failure modes are
shown
Fig.10Effect of yield ratio of aged AA6111-T4aluminum on the section parameters of the clinching 0.7mm thick SAE1004to 1.0mm thick AA6111-T4
joints
Fig.11Effect of aging time on the failure modes of the clinching 0.7mm thick SAE1004to 1.0mm thick AA6111-T4joints.(a )0,(b )5,(c )10,(d )15,and (e )20
days
Fig.12Relationship among yield strength and yield ratio of aged AA6111-T4aluminum and strength of clinching 0.7mm thick SAE1004to 1.0mm thick AA6111-T4joints
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in Fig.11.As sown,though aged AA6111-T4aluminum had a distinctly in?uence on the section parameters,all the clinching joints had the similar failure mode,a mixed button pull-out and neck cracking failure.These results suggested that the strengthen-ing of aged AA6111-T4aluminum likely affected little the joint strength.
However,test results shown in Fig.12indicated that the strength of the clinching joints increased with increasing the yield strength and yield ratio of the aged aluminum.To understand how the yield strength and yield ratio affected the joint strength,the section parameters of the joints were correlated with the yield strength of aged AA6111-T4and the correlations are shown in Fig.13.As shown,the joint strength increased with the increase of bottom sheet thickness and decreased with the increase of undercut.These results suggested that the strengthening of aged aluminum is bene?cial to the strength of the clinching joints.The increase in joint strength caused by the strengthening of aluminum likely offset the decrease in joint strength caused by the low undercut,which will be discussed in Sec.3.4.
3.4Effect of Aged AA6111-T4Aluminum on Joint Strength.As discussed in Secs.3.2and 3.3,though the strength-ening of aged AA6111-T4workpiece had an adverse effect on the undercut,it is bene?cial to the strength of the clinching joints.These results suggested that the aged aluminum likely enhanced the mechanical interlock between the upper steel and lower alumi-num workpieces even though the undercut of the joints decreased.To understand the effect of mechanical properties of aged AA6111-T4on the interlock of the workpieces,an analytical model is put forward as shown in Fig.1
4.In this model,based on the section observations shown in Fig.8,the undercut between the upper and lower workpieces is taken to start from the half of the thickness of the lower workpiece (i.e.,A point in Fig.14)to end at the corner of the upper workpieces button (i.e.,C point in Fig.14).Under this circumstance,the angle of the interlock region shown in Fig.14can be estimated as follows:
tan a ?
t U H m t12d 2à12
t B
(3)
where t U is the undercut,H m is the die depth,and d 2is the thick-ness of the lower workpiece.
Experimental observations revealed that the clinching joints failed by slowly pulling out the button from the lower workpiece while the button rotated,and eventually the joints failed in a mixed button pull-out and neck cracking.To simplify the model,the button is assumed to rotate clockwise around point O in the lower workpiece shown in Fig.14.The stress distribution of the button in the upper workpiece under an applied F shown in Fig.14is analyzed next.
As shown in Fig.14,F stands for the load applied to the clinch-ing joints and N and f ?l N represent the contact pressure and fric-tion between the upper and lower workpieces of the clinching joints,respectively.The frictional force,f ,can be decomposed into a lateral and a vertical components.The vertical component restrains the button from pulling out of the lower workpieces while the lateral component pushes the button rotating around point O in the lower workpiece.Both induce the interlock forces between the upper and lower workpieces,which determines the strength of the clinching joints.Since the contact pressure N and frictional force f develop at the location B under an applied F ,the maximum interlock force occurs at this location.With these sim-pli?cations,the joint strength (applied load F )can be estimated by
F ?
4ásin a tl cos a eTát U tt N tR P eTN
2H m td 1td 2àt B
(4)
It can be seen in Eq.(4)that the joint strength F is proportionate to the contact pressure N .During the clinching,the punch force pushes the materials ?owing into a die and forces the upper work-piece to undercut the lower workpiece to form a local permanent set and a mechanical interlock between the workpieces.It is obvious that the undercut is the results of the plastic deformation of the lower workpiece under the contact pressure N of the upper workpiece.Therefore,the contact pressure N (in Eq.(4))is related to the deformation resistance of the lower workpiece.
Assuming the plastic deformation of AA6111-T4aluminum workpiece is in accordance with the von Mises yield criterion as in the following
equation:
Fig.13Relationship among undercut,bottom thickness and strength of clinching 0.7mm thick SAE1004to 1.0mm thick AA6111-T4
joints
Fig.14Simpli?ed model of a clinching joint under quasi-static
lap-shear
loading
Fig.15Stresses acting on the lower sheet in the interlock region of a clinching joint
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r 2s
?12
r 1àr 2eT2tr 1àr 3eT2tr 2àr 3eT2
h i (5)
where r 1,r 2,and r 3are the principal stresses in the interlock region.The values of r 1,r 2,and r 3can be expressed according to Fig.15as follows:
r x ?r y ?r N cos a tlr N sin a ?r 1?r 2
(6)r z ?r N sin a àlr N cos a ?r 3
(7)
where r N is the press stress,which is the contact pressure per unit of area on the interface applied by the upper workpiece during the https://www.doczj.com/doc/3513791150.html,bining Eqs.(5)–(7),the press stress r N can be obtained
r N ?
r s
cos a e1tl Tàsin a e1àl T
(8)
It is noted that the undercut was formed between the joined materials.The plastic deformation of the lower workpiece is actually restrained by both die and upper workpiece during the clinching.Once the clinching is completed and the clinching workpieces are removed from the die,the restraint from the die is relived while the restraint from the upper workpiece remains after clinching.Therefore,a spring back in the lower workpiece is developed after clinching,which produced by the elastic recovery and may release the contact pressure N between the upper and lower workpieces.Because the spring back is closely related to the material properties [42,43],high yield strength and yield ratio r s /r b may result in low formability and signi?cant spring back af-ter plastic deformation [44].Therefore,to evaluate the effect of spring back on the joint strength,we assumed the spring back is proportional to the yield strength and yield ratio of the material and characterized by an imaginary force P shown in Fig.15,which is expressed by an empirical formula:
P ?b r s =r b eTr s
(9)
where r s /r b is the yield ratio and b is the empirical parameter that is determined by the formability of the materials.It can be season-ably assumed that the higher the formability is,the lower the b value is.The actual value of residual press stress r N after spring back can be estimated according to Eq.(10)as follows:
r AN ?
1
cos a e1tl Tàsin a e1àl Tàb r s =r b eT
r s (10)The actual value of contact pressure N existed on the interface between the upper and lower workpieces can be obtained by the following equation:
N ?r N áS ?p t U tt N eT2
t2R P t U tt N eTh i
r AN (11)where S is the effective action area of r N ,which is the projection
area of the button shown in https://www.doczj.com/doc/3513791150.html,bining Eqs.(4)and (11),the strength of the clinching joints,F ,can be estimated using Eq.(12)
F ?
4p ásin a tl cos a eTát U tt N tR P eTt U tt N eT2
t2R P t U tt N eTh i
m 12B
ár AN (12)According to Eqs.(8)–(12),the strengthening caused by natural aging increases the resistance of plastic deformation of AA6111-T4aluminum.This strengthening may decrease the undercut of the joints,which is unfavorable to the joint strength.To compensate this,the upper galvanized SAE1004steel workpiece must exert a large press force r N on the lower workpiece to ensure the undercut during the clinching.Therefore,there may exist signi?cant contact pressure N on the interface between the upper and lower workpie-ces to interlock them together after clinching.The large contact pressure,N ,increases signi?cantly the friction between the upper and lower workpieces to restrain pulling out and rotating the but-ton,which is favorable to the increase of the joint strength.
To estimate the joint strength,there is a need to set a suitable value of b to characterize the effect of spring back.As the free na-ture aged aluminum had good formability and low spring back while aged aluminum had low formability and high spring back,the value of b in Eq.(12)is assumed as 0.75for free nature aged aluminum while the value of b is 1.23for aged aluminum.The joint strengths were estimated by substituting the thicknesses of the workpieces (i.e.,d 1?0.7mm and d 2?1.0mm),the die and punch diameters in Table 4,the mechanical properties of the aged aluminum in Fig.7and the section parameters of the clinching joints in Figs.9and 10into Eq.(12).Figure 16presents the com-parison of the modeling results with the experimental measure-ments.As shown,the modeling results are consistent with the experimental measurements.
4Conclusion
(1)Natural aging of aluminum AA6111-T4at ambient tempera-ture increased the tensile and yield strengths and decreased the elongation of aluminum,which resulted in a decrease in undercut and an increase in bottom thickness of the clinching galvanized SAE1004and AA6111-T4aluminum.
(2)Aged AA6111-T4aluminum increased the strength of the clinching 0.7mm thick galvanized SAE1004to 1.0mm thick AA6111-T4joints even though it decreased the undercut of the clinching joints.
(3)An analytical model has been developed to estimate the strength of the clinching steel-to-aluminum joints.Based on the model,the in?uence of aged aluminum AA6111-T4on the joint strength was primarily attributed to the strengthening of alumi-num,which required large force to make the undercut in the lower AA6111-T4aluminum workpiece during the clinching.Therefore,large residual press stresses existed on the surface of the lower workpiece to lock the upper workpiece after clinching.
Acknowledgement
The authors gratefully acknowledge the ?nancial and technical support provided by GM-Research and Development to carry out the present work.
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041016-8/Vol.136,AUGUST2014Transactions of the ASME
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一般过去式 时间状语：yesterday just now (刚刚) the day before three days ag0 a week ago in 1880 last month last year 1. I was in the classroom yesterday. I was not in the classroom yesterday. Were you in the classroom yesterday. 2. They went to see the film the day before. Did they go to see the film the day before. They did go to see the film the day before. 3. The man beat his wife yesterday. The man didn’t beat his wife yesterday. 4. I was a high student three years ago. 5. She became a teacher in 2009. 6. They began to study english a week ago 7. My mother brought a book from Canada last year. 8.My parents build a house to me four years ago . 9.He was husband ago. She was a cooker last mouth. My father was in the Xinjiang half a year ago. 10.My grandfather was a famer six years ago. 11.He burned in 1991
●I wonder if it’s because I have been at school for so long that I’ve grown so crazy about going home. ●It is because she wasn’t well that she fell far behind her classmates this semester. ●I can well remember that there was a time when I took it for granted that friends should do everything for me. ●In order to make a difference to society, they spent almost all of their spare time in raising money for the charity. ●It’s no pleasure eating at school any longer because the food is not so tasty as that at home. ●He happened to be hit by a new idea when he was walking along the riverbank. ●I wonder if I can cope with stressful situations in life independently. ●It is because I take things for granted that I make so many mistakes. ●The treasure is so rare that a growing number of people are looking for it. ●He picks on the weak mn in order that we may pay attention to him. ●It’s no pleasure being disturbed whena I settle down to my work. ●I can well remember that when I was a child, I always made mistakes on purpose for fun. ●It’s no pleasure accompany her hanging out on the street on such a rainy day. ●I can well remember that there was a time when I threw my whole self into study in order to live up to my parents’ expectation and enter my dream university. ●I can well remember that she stuck with me all the time and helped me regain my confidence during my tough time five years ago. ●It is because he makes it a priority to study that he always gets good grades. ●I wonder if we should abandon this idea because there is no point in doing so. ●I wonder if it was because I ate ice-cream that I had an upset student this morning. ●It is because she refused to die that she became incredibly successful. ●She is so considerate that many of us turn to her for comfort. ●I can well remember that once I underestimated the power of words and hurt my friend. ●He works extremely hard in order to live up to his expectations. ●I happened to see a butterfly settle on the beautiful flower. ●It’s no pleasure making fun of others. ●It was the first time in the new semester that I had burned the midnight oil to study. ●It’s no pleasure taking everything into account when you long to have the relaxing life. ●I wonder if it was because he abandoned himself to despair that he was killed in a car accident when he was driving. ●Jack is always picking on younger children in order to show off his power. ●It is because he always burns the midnight oil that he oversleeps sometimes. ●I happened to find some pictures to do with my grandfather when I was going through the drawer. ●It was because I didn’t dare look at the failure face to face that I failed again. ●I tell my friend that failure is not scary in order that she can rebound from failure. ●I throw my whole self to study in order to pass the final exam. ●It was the first time that I had made a speech in public and enjoyed the thunder of applause. ●Alice happened to be on the street when a UFO landed right in front of her. ●It was the first time that I had kept myself open and talked sincerely with my parents. ●It was a beautiful sunny day. The weather was so comfortable that I settled myself into the
高中英语~词性~句子成分~语法构成 第一章节：英语句子中的词性 1.名词：n. 名词是指事物的名称，在句子中主要作主语.宾语.表语.同位语。 2.形容词;adj. 形容词是指对名词进行修饰~限定~描述~的成份，主要作定语.表语.。形容词在汉语中是（的）.其标志是: ous. Al .ful .ive。. 3.动词：vt. 动词是指主语发出的一个动作，一般用来作谓语。 4.副词：adv. 副词是指表示动作发生的地点. 时间. 条件. 方式. 原因. 目的. 结果.伴随让步. 一般用来修饰动词. 形容词。副词在汉语中是（地）.其标志是：ly。 5.代词：pron. 代词是指用来代替名词的词，名词所能担任的作用，代词也同样.代词主要用来作主语. 宾语. 表语. 同位语。 6.介词：prep.介词是指表示动词和名次关系的词，例如：in on at of about with for to。其特征：
介词后的动词要用—ing形式。介词加代词时，代词要用宾格。例如：give up her（him）这种形式是正确的，而give up she（he）这种形式是错误的。 7.冠词：冠词是指修饰名词，表名词泛指或特指。冠词有a an the 。 8.叹词：叹词表示一种语气。例如：OH. Ya 等 9.连词：连词是指连接两个并列的成分，这两个并列的成分可以是两个词也可以是两个句子。例如：and but or so 。 10.数词：数词是指表示数量关系词，一般分为基数词和序数词 第二章节：英语句子成分 主语：动作的发出者，一般放在动词前或句首。由名词. 代词. 数词. 不定时. 动名词. 或从句充当。 谓语：指主语发出来的动作，只能由动词充当，一般紧跟在主语后面。 宾语：指动作的承受着，一般由代词. 名词. 数词. 不定时. 动名词. 或从句充当. 介词后面的成分也叫介词宾语。 定语：只对名词起限定修饰的成分，一般由形容
M A: Has the case been closed yet? B: No, the magistrate still needs to decide the outcome. magistrate n.地方行政官，地方法官，治安官 A: I am unable to read the small print in the book. B: It seems you need to magnify it. magnify vt.１．放大，扩大；２．夸大，夸张 A: That was a terrible storm. B: Indeed, but it is too early to determine the magnitude of the damage. magnitude n.１．重要性，重大；２．巨大，广大 A: A young fair maiden like you shouldn’t be single. B: That is because I am a young fair independent maiden. maiden n.少女，年轻姑娘，未婚女子 a.首次的，初次的 A: You look majestic sitting on that high chair. B: Yes, I am pretending to be the king! majestic a.雄伟的，壮丽的，庄严的，高贵的 A: Please cook me dinner now. B: Yes, your majesty, I’m at your service. majesty n.１．［Ｍ－］陛下（对帝王，王后的尊称）；２．雄伟，壮丽，庄严 A: Doctor, I traveled to Africa and I think I caught malaria. B: Did you take any medicine as a precaution? malaria n.疟疾 A: I hate you! B: Why are you so full of malice? malice n.恶意，怨恨 A: I’m afraid that the test results have come back and your lump is malignant. B: That means it’s serious, doesn’t it, doctor? malignant a.１．恶性的，致命的；２．恶意的，恶毒的 A: I’m going shopping in the mall this afternoon, want to join me? B: No, thanks, I have plans already. mall n.（由许多商店组成的）购物中心 A: That child looks very unhealthy. B: Yes, he does not have enough to eat. He is suffering from malnutrition.
意见应以事实为根据. 3 来自辞典例句 192. The bombers swooped ( down ) onthe air base. 轰炸机 突袭 空军基地. 来自辞典例句 193. He mounted their engines on a rubber base. 他把他们的发动机装在一个橡胶垫座上. 14 来自辞典例句 194. The column stands on a narrow base. 柱子竖立在狭窄的地基上. 14 来自辞典例句 195. When one stretched it, it looked like grey flakes on the carvas base. 你要是把它摊直, 看上去就象好一些灰色的粉片落在帆布底子上. 18 来自辞典例句 196. Economic growth and human well - being depend on the natural resource base that supports all living systems. 经济增长和人类的福利依赖于支持所有生命系统的自然资源. 12 1 来自辞典例句 197. The base was just a smudge onthe untouched hundred - mile coast of Manila Bay. 那基地只是马尼拉湾一百英里长安然无恙的海岸线上一个硝烟滚滚的污点. 6 来自辞典例句 198. You can't base an operation on the presumption that miracles are going to happen. 你不能把行动计划建筑在可能出现奇迹的假想基础上.
英语造句大全English sentence 在句子中，更好的记忆单词！ 1、(1)、able adj. 能 句子：We are able to live under the sea in the future. (2)、ability n. 能力 句子：Most school care for children of different abilities. (3)、enable v. 使。。。能句子：This pass enables me to travel half-price on trains. 2、(1)、accurate adj. 精确的句子：We must have the accurate calculation. (2)、accurately adv. 精确地 句子：His calculation is accurately. 3、(1)、act v. 扮演 句子：He act the interesting character. （2）、actor n. 演员 句子：He was a famous actor. (3)、actress n. 女演员 句子：She was a famous actress. (4)、active adj. 积极的 句子：He is an active boy. 4、add v. 加 句子：He adds a little sugar in the milk. 5、advantage n. 优势 句子：His advantage is fight. 6、age 年龄n. 句子：His age is 15. 7、amusing 娱人的adj. 句子：This story is amusing. 8、angry 生气的adj. 句子：He is angry. 9、America 美国n.
主语+谓语 1. 理解主谓结构 1) The students arrived. The students arrived at the park. 2) They are listening. They are listening to the music. 3) The disaster happened. 2．体会状语的位置 1) Tom always works hard. 2) Sometimes I go to the park at weekends.. 3) The girl cries very often. 4) We seldom come here. The disaster happened to the poor family. 3. 多个状语的排列次序 1) He works. 2) He works hard. 3) He always works hard. 4) He always works hard in the company. 5) He always works hard in the company recently. 6) He always works hard in the company recently because he wants to get promoted. 4. 写作常用不及物动词 1. ache My head aches. I’m aching all over. 2. agree agree with sb. about sth. agree to do sth. 3. apologize to sb. for sth. 4. appear (at the meeting, on the screen) 5. arrive at / in 6. belong to 7. chat with sb. about sth. 8. come (to …) 9. cry 10. dance 11. depend on /upon 12. die 13. fall 14. go to … 15. graduate from 16. … happen 17. laugh 18. listen to... 19. live 20. rise 21. sit 22. smile 23. swim 24. stay (at home / in a hotel) 25. work 26. wait for 汉译英： 1.昨天我去了电影院。 2.我能用英语跟外国人自由交谈。 3.晚上7点我们到达了机场。 4.暑假就要到了。 5.现在很多老人独自居住。 6.老师同意了。 7.刚才发生了一场车祸。 8.课上我们应该认真听讲。9. 我们的态度很重要。 10. 能否成功取决于你的态度。 11. 能取得多大进步取决于你付出多少努力。 12. 这个木桶能盛多少水取决于最短的一块板子的长度。
【it's time to和it's time for】 ——————这其实是一个句型,只不过后面要跟不同的东西. ——————It's time to跟的是不定式（to do）.也就是说,要跟一个动词,意思是“到做某事的时候了”.如： It's time to go home. It's time to tell him the truth. ——————It's time for 跟的是名词.也就是说,不能跟动词.如： It's time for lunch.(没必要说It's time to have lunch) It's time for class.(没必要说It's time to begin the class.) They can't wait to see you Please ask liming to study tonight. Please ask liming not to play computer games tonight. Don’t make/let me to smoke I can hear/see you dance at the stage You had better go to bed early. You had better not watch tv It’s better to go to bed early It’s best to run in the morning I am enjoy running with music. With 表伴随听音乐 I already finish studying You should keep working. You should keep on studying English Keep calm and carry on 保持冷静继续前行二战开始前英国皇家政府制造的海报名字 I have to go on studying I feel like I am flying I have to stop playing computer games and stop to go home now I forget/remember to finish my homework. I forget/remember cleaning the classroom We keep/percent/stop him from eating more chips I prefer orange to apple I prefer to walk rather than run I used to sing when I was young What’s wrong with you There have nothing to do with you I am so busy studying You are too young to na?ve I am so tired that I have to go to bed early
《The Kite Runner》追风筝的人--------------------------------美句摘抄 1.I can still see Hassan up on that tree, sunlight flickering through the leaves on his almost perfectly round face, a face like a Chinese doll chiseled from hardwood: his flat, broad nose and slanting, narrow eyes like bamboo leaves, eyes that looked, depending on the light, gold, green even sapphire 翻译：我依然能记得哈桑坐在树上的样子，阳光穿过叶子，照着他那浑圆的脸庞。他的脸很像木头刻成的中国娃娃，鼻子大而扁平，双眼眯斜如同竹叶，在不同光线下会显现出金色、绿色，甚至是宝石蓝。 E.g.: A shadow of disquiet flickering over his face. 2.Never told that the mirror, like shooting walnuts at the neighbor's dog, was always my idea. 翻译：从来不提镜子、用胡桃射狗其实都是我的鬼主意。E.g.:His secret died with him, for he never told anyone. 3.We would sit across from each other on a pair of high
一、翻译 1. The idea of consciously seeking out a special title was new to me., but not without appeal. 让我自己挑选自己最喜欢的书籍这个有意思的想法真的对我具有吸引力。 2.I was plunged into the aching tragedy of the Holocaust, the extraordinary clash of good, represented by the one decent man, and evil. 我陷入到大屠杀悲剧的痛苦之中，一个体面的人所代表的善与恶的猛烈冲击之中。 3.I was astonished by the the great power a novel could contain. I lacked the vocabulary to translate my feelings into words. 我被这部小说所包含的巨大能量感到震惊。我无法用语言来表达我的感情（心情）。 4，make sth. long to short长话短说 5.I learned that summer that reading was not the innocent(简单的) pastime(消遣) I have assumed it to be., not a breezy, instantly forgettable escape in the hammock(吊床)，( though I’ ve enjoyed many of those too ). I discovered that a book, if it arrives at the right moment, in the proper season, will change the course of all that follows. 那年夏天，我懂得了读书不是我认为的简单的娱乐消遣，也不只是躺在吊床上，一阵风吹过就忘记的消遣。我发现如果在适宜的时间、合适的季节读一本书的话，他将能改变一个人以后的人生道路。 二、词组造句 1. on purpose 特意，故意 This is especially true here, and it was ~. (这一点在这里尤其准确，并且他是故意的) 2.think up 虚构，编造，想出 She has thought up a good idea. 她想出了一个好的主意。 His story was thought up. 他的故事是编出来的。 3. in the meantime 与此同时 助记：in advance 事前in the meantime 与此同时in place 适当地... In the meantime, what can you do? 在这期间您能做什么呢？ In the meantime, we may not know how it works, but we know that it works. 在此期间，我们不知道它是如何工作的，但我们知道，它的确在发挥作用。 4.as though 好像，仿佛 It sounds as though you enjoyed Great wall. 这听起来好像你喜欢长城。 5. plunge into 使陷入 He plunged the room into darkness by switching off the light. 他把灯一关，房
The effective sentences:(improve the sentences!) 1.She hopes to spend this holiday either in Shanghai or in Suzhou. 2.Showing/to show sincerity and to keep/keeping promises are the basic requirements of a real friend. 3.I want to know the space of this house and when it was built. I want to know how big this house is and when it was built. I want to know the space of this house and the building time of the house. 4.In the past ten years,Mr.Smith has been a waiter,a tour guide,and taught English. In the past ten years,Mr.Smith has been a waiter,a tour guide,and an English teacher. 5.They are sweeping the floor wearing masks. They are sweeping the floor by wearing masks. wearing masks,They are sweeping the floor. 6.the drivers are told to drive carefully on the radio. the drivers are told on the radio to drive carefully 7.I almost spent two hours on this exercises. I spent almost two hours on this exercises. 8.Checking carefully,a serious mistake was found in the design. Checking carefully,I found a serious mistake in the design.
M1 U1 一. 把下列短语填入每个句子的空白处（注意所填短语的形式变化）： add up (to) be concerned about go through set down a series of on purpose in order to according to get along with fall in love (with) join in have got to hide away face to face 1 We’ve chatted online for some time but we have never met ___________. 2 It is nearly 11 o’clock yet he is not back. His mother ____________ him. 3 The Lius ___________ hard times before liberation. 4 ____________ get a good mark I worked very hard before the exam. 5 I think the window was broken ___________ by someone. 6 You should ___________ the language points on the blackboard. They are useful. 7 They met at Tom’s party and later on ____________ with each other. 8 You can find ____________ English reading materials in the school library. 9 I am easy to be with and _____________my classmates pretty well. 10 They __________ in a small village so that they might not be found. 11 Which of the following statements is not right ____________ the above passage? 12 It’s getting dark. I ___________ be off now. 13 More than 1,000 workers ___________ the general strike last week. 14 All her earnings _____________ about 3,000 yuan per month. 二.用以下短语造句： 1.go through 2. no longer/ not… any longer 3. on purpose 4. calm… down 5. happen to 6. set down 7. wonder if 三. 翻译： 1.曾经有段时间，我对学习丧失了兴趣。（there was a time when…） 2. 这是我第一次和她交流。（It is/was the first time that …注意时态） 3.他昨天公园里遇到的是他的一个老朋友。（强调句） 4. 他是在知道真相之后才意识到错怪女儿了。（强调句） M 1 U 2 一. 把下列短语填入每个句子的空白处（注意所填短语的形式变化）： play a …role (in) because of come up such as even if play a …part (in) 1 Dujiangyan(都江堰) is still ___________in irrigation(灌溉) today. 2 That question ___________ at yesterday’s meeting. 3 Karl Marx could speak a few foreign languages, _________Russian and English. 4 You must ask for leave first __________ you have something very important. 5 The media _________ major ________ in influencing people’s opinion s. 6 _________ years of hard work she looked like a woman in her fifties. 二.用以下短语造句： 1.make (good/full) use of 2. play a(n) important role in 3. even if 4. believe it or not 5. such as 6. because of
English sentence 1、(1)、able adj. 能 句子：We are able to live under the sea in the future. (2)、ability n. 能力 句子：Most school care for children of different abilities. (3)、enable v. 使。。。能 句子：This pass enables me to travel half-price on trains. 2、(1)、accurate adj. 精确的 句子：We must have the accurate calculation. (2)、accurately adv. 精确地 句子：His calculation is accurately. 3、(1)、act v. 扮演 句子：He act the interesting character.（2）、actor n. 演员 句子：He was a famous actor. (3)、actress n. 女演员 句子：She was a famous actress. (4)、active adj. 积极的 句子：He is an active boy. 4、add v. 加 句子：He adds a little sugar in the milk. 5、advantage n. 优势 句子：His advantage is fight. 6、age 年龄n. 句子：His age is 15. 7、amusing 娱人的adj. 句子：This story is amusing. 8、angry 生气的adj. 句子：He is angry. 9、America 美国n. 句子：He is in America. 10、appear 出现v. He appears in this place. 11. artist 艺术家n. He is an artist. 12. attract 吸引 He attracts the dog. 13. Australia 澳大利亚 He is in Australia. 14.base 基地 She is in the base now. 15.basket 篮子 His basket is nice. 16.beautiful 美丽的 She is very beautiful. 17.begin 开始 He begins writing. 18.black 黑色的 He is black. 19.bright 明亮的 His eyes are bright. 20.good 好的 He is good at basketball. 21.British 英国人 He is British. 22.building 建造物 The building is highest in this city 23.busy 忙的 He is busy now. 24.calculate 计算 He calculates this test well. 25.Canada 加拿大 He borns in Canada. 26.care 照顾 He cared she yesterday. 27.certain 无疑的 They are certain to succeed. 28.change 改变 He changes the system. 29.chemical 化学药品