汽車驅(qū)動橋設(shè)計【輕型貨車驅(qū)動橋設(shè)計】【主減速器采用單級主減速器驅(qū)動橋】,輕型貨車驅(qū)動橋設(shè)計,主減速器采用單級主減速器驅(qū)動橋,汽車驅(qū)動橋設(shè)計【輕型貨車驅(qū)動橋設(shè)計】【主減速器采用單級主減速器驅(qū)動橋】,汽車,驅(qū)動,設(shè)計,輕型,貨車,減速器,采用,采取,采納,單級主 Ping Tong accepted auto-body shallow steel. The crashworthiness simulation of the lightweight part proves the validity of the lightweighting process. C211 2004 Elsevier Ltd. All rights reserved. stated that petrol consumption can decrease by 810% strength steel sheet can be used in auto-body to improve metal Panels, most of which are shallow panels. Dent resistanceisthe abilitytoretainthe shapeagainstsunken deflection and local dent under the external force. Dent * Corresponding author. Tel.: +86 21 62932964; fax: +86 21 62933093. E-mail address: (Y. Zhang). Materials and Design 27 (2006) Materials 0261-3069/$ - see front matter C211 2004 Elsevier Ltd. All rights reserved. with 10% reduction of car weight 2. Thus, automobile lightweight is a basic way to fuel saving. In order to reduce the automobile weight, there are two important methods 3: One, automobile parts are redesigned to optimize the structure. By using thinning, hollowing, minitype, and compound parts, car weight can be reduced. The other, more and more lightweight materials, such as aluminum alloy, high strength steel, composite material, are widely used as lightweight mate- rials to replace the traditional materials like mild steel 4. These materials could reduce the weight remarkably. componentsC213 impact energy absorption capacity and resistance to plastic deformation. The automobile weight can be reduced by use of high strength steel sheet of a thinner thickness to replace the mild steel sheet of body parts 1,3. Comparing with aluminum, magne- sium, and composite materials, high strength steel has better economy in that its raw material and fabrication cost are cheaper. Besides, high strength steel can be di- rectly used in product line including forming, wielding, assembling, and painting. The operating cost can be saved since there is no need adjusting the whole line. Outside of automobile body, there are several sheet Keywords: High strength steel; Lightweight; Dent resistance 1. Introduction In recent years, the retaining number of automobiles has been increasing steadily, which has impacted the society and human life greatly. Such situation leads to many severe problems such as fuel crisis, environment pollution. The international association of aluminum Material replacement is generally more eective in auto- mobile lightweighting than structure modification. With the introduction of automobile safety legislation, crash- worthiness and safety should be considered as precondi- tions in lightweighting design of auto-body. High strength steel is widely used in automobile replacing the traditional material of mild steel. High Short communic Lightweight design of automobile high strength steel based Yan Zhang * , Xinmin Lai, School of Mechanical Engineering, Shanghai Jiao Received 19 May 2004; Abstract Lightweight and crashworthiness are two important aspects of the expression of dent resistance stiness of double curvatured shallow critical loads resulting in the local trivial dent in the center of the of the automobile parts. This rule is applied to the lightweight design doi:10.1016/j.matdes.2004.09.010 ation component using on dent resistance Zhu, Wurong Wang University, Shanghai 200030, PR China 14 September 2004 design. In this paper, based on the shallow shell theory, shell is obtained under the concentrated load condition. The shell is regarded as the important index for the lightweight of bumper system by using high strength steel instead of mild 6468 y: 1 The following equations can be obtained because of the flatness of the shell: oz ox C18C19 2 C28 1; oz oy C18C19 2 C28 1; oz ox C18C19 oz oy C18C19C12 C12 C12 C12 C12 C12 C12 C12 C28 1: 2 The curvature and torsion of mid surface can be approx- imated to: k x C0 o 2 z ox 2 ; k y C0 o 2 z oy 2 ; k xy C0 o 2 z oxoy : 3 The Lae coecients of mid surface along a and b direc- tions are deduced: A ds 1 da dx dx 1; B ds 2 db dy dy 1: 4 Applying concentrated force P along Z-axis and ignor- ing the influence of the transverse shear resultant forces, the balance dierential equations of shallow shell are: oN 1 ox oS oy 0; oN 2 oy oS ox 0; C0k x N 1 k y N 2 oQ 1 ox oQ 2 oy Pd0;00; 5 Q 1 oM 12 oy oM 1 ox ; Q 2 oM 12 ox oM 2 oy ; where d(0,0) is Dirac-d function. The compatibility equation of shallow shell is r 2 N 1 N 2 C0Etr 2 k w 0; 6 where r 2 o 2 ox 2 o 2 oy 2 ; r 2 k k x o 2 ox 2 k y o 2 oy 2 : Expressing the moment resultants M 1 , M 2 and M 12 by the function of transverse displacement w, the basic equations of shallow shell under concentrated transverse forces are: Dr 2 r 2 wk x N 1 k y N 2 Pd0;0; r 2 N 1 N 2 C0Etr 2 k w 0; o 2 N 1 ox 2 o 2 N 2 oy 2 ; 7 where N 1 is the membrane stress resultant in X-direc- tion; N 2 , the membrane resultant in Y-direction; D, the Design 27 (2006) 6468 65 bending stiness of shallow shell. ders of derivatives of w, N 1 , N 2 become to zero at infin- mula that expresses minimum energy W causing visible trivial dent trace by thickness t, yield stress r s and basic dent resistance stiness K W C r 2 s t 4 K ; 13 where C is proportional constant. From Eqs. (12) and (13), the critical load P cr resulting in the local trivial dent in the center of the shallow shell can be achieved, which is defined as the evaluating index P cr Cr s t 2 : 14 the characteristic length of the minimal element is ensured to improve the simulation eciency. and Design 27 (2006) 6468 ity. The following equations can be achieved by Fourier transformation to Eq. (7): Dn 2 g 2 wk x N 1 k y N 2 P; n 2 g 2 N 1 N 2 C0Etk y n 2 k x g 2 w 0; n 2 N 1 g 2 N 2 ; 8 where: Z 1 C01 Z 1 C01 Pd0;0e C0inx e C0igy dx dy P; w 4 Z 1 0 Z 1 0 wcosnxcosgydx dy; N 1 4 Z 1 0 Z 1 0 N 1 cosnxcosgydx dy; N 2 4 Z 1 0 Z 1 0 N 2 cosnxcosgydx dy: 9 From Eq.(8), w can be obtained. Reverse Fourier trans- formation to w and polar coordinates transformation to n, g, w under polar coordinate system can be gained w P p 2 D Z p=2 0 Z 1 0 qcosqxcoshcosqysinh q 4 12 t 2 k x cos 2 hk y sin 2 h 2 dq dh; 10 Put x = 0 and y =0inEq.(8), the relationship between deflection f p and concentrated force P of rectangle shal- low shell can be achieved as follows: P 4Et 2 k x k y p 1C0l 2 3 p f p : 11 Finally, dent resistance stiness of shallow shell K is obtained K P f p 4Et 2 k x k y p 1C0l 2 3 p : 12 This equation explains synthetically the relationship be- tween the dent resistance stiness of double curvature shallow shell and all influencing factors including mate- rial properties, geometry parameters, which can be used to guide design, material select and manufacture. 2.2. Analysis of critical load causing local trivial dent For quantitative evaluation of critical load against lo- cal dent resistance of panels, several experience formulas have been brought forward by researchers. Based on It is very dicult to solve above equation. According to practical situation, sunken deflection will only con- centrate on a small area around external force P, so infi- nite large shallow shell 5 is assumed in this study. Because w, N 1 , N 2 are symmetric about x-, y-axis, all or- 66 Y. Zhang et al. / Materials large numbers of experiments, Dicellello 9 stated a for- 4. Materials constitutive with CowperSymonds strain rate item is used for steel parts. 5. Automatic single surface contact algorithm is adopted in the simulation aiming at complexity of car impact simulation. From Eq. (14), there is a closely correlation between critical loads P cr and thickness t, yield stress r s . The crit- ical load can be a rule to carry out lightweight design of automobile parts by using high strength steel instead of mild steel. 3. Example and crashworthiness analysis 3.1. FE model of full car and its crash simulation A detailed finite element model has been established based on a passenger car refitted from a saloon car, which is showed in Fig. 2. To ensure the correctness and eectiveness of FE model, the following methods are adopted: 1. Since the goal is to simulate the frontal impact of the car, the meshing of front car body is denser than that of the rear car body. 2. Reduced integration method with hourglass control is taken for 4 noded shell element and 8 noded brick solid element to improve the eciency of simulation. 3. By using of the meshing and mass scaling technology, Fig. 2. Finite element model of full car. 6. Spot weld element with failure rule that considering the couple of normal force and shear force is used to simulatethe spot weld connection between auto parts. Explicit dynamic FEM software LS-DYNA Version 950isusedtosimulatethefrontalimpactofthecaragainst dle part of bumper. And the energy absorption history is shown in the following for beam of the bumper. From Fig. 4 the dierence of the energy absorption between Fig. 3. The deformation history of bumper using high strength steel. Y. Zhang et al. / Materials and Design 27 (2006) 6468 67 a rigid wall at the speed of 50 km/s according to the Na- tional Crash Legislation CMVDR294. A real car crash experiment is done at Car Crash Lab settled in TSing HuaUniversity.Bycomparingthetimehistoryofacceler- ation of certain position on the A pillar within 0.1 s, the simulationgivesareasonablefittotheexperimentresults, whichguaranteesthecorrectnessofFEmodelandgivesa nicer base for the next lightweighting optimized design. 3.2. Lightweighting design and crashworthiness analysis The use of high strength steel is one of the eective ways to reduce car weight. However, the performance (such as crashworthiness, stiness, and dent resistance) of part made of new material should be assured. For example, the front parts of a car are major energy absorption parts in the process of car crash, so energy absorption performance without aecting the safety of passengers should be assured in the design of front parts of a car. In this research, the bumper of the passenger car is studied under dierent materials but remaining its dent resistance. The mechanical properties of mild steel and high strength steel are listed below (see Table 1). The evaluation index of dent resistance for bumper using mild steel is P cr1 C 1 r s1 t 2 1 : 15 When high strength steel is used to replace the mild steel remaining its primary shape and dent resistance per- formance, the new thickness t 2 of high strength steel can be achieved t 2 C 1 r s1 C 2 r s2 t 1 r : 16 From (16), the thickness of bumper that uses high strength steel is gained and updated in the full car FE model. The deformation history of bumper using new material is achieved after the car crash is re-simulated with updated part thickness (see Fig. 3). By simulation, the deformations of bumper made of two dierent kinds of material are similar in that plastic hingeandtensionalplasticdeformationappearinthemid- Table 1 Mechanical properties of two materials Material Density (g/cm 3 ) E (GPa) lr s (MPa) Mild steel 7.8 210 0.3 166 High strength steel 7.8 210 0.3 220 Fig. 4. Energy absorption time history of bumper beam. twomaterialsissmall,about4.1%forbeamofthebumper, fromwhichaconclusioncanbedrawnthatitisfeasibleto reducethethicknessofthebumperpanelbasedonthedent resistance evaluation index studied in this research. 4. Conclusion Dent resistance performance of small curvature shal- low shell parts in automobile is studied in this paper, which enables the follows: 1. Dent resistance stiness under concentrated force is given for such parts. 2. The critical load resulting in the local trivial dent in the center of the shallow shell has been deduced, which in turn becomes the index to evaluate the dent resistance of automobile parts. 3. The validity of evaluating index is proven by applying the developed rule to the lightweight design of bum- per system using high strength steel instead of mild steel through crashworthiness simulation. References 1 Yuxan Li, Zhongqin Lin, Aiqin Jiang, Guanlong Chen. Use of high strength steel for lightweight and crashworthy car body. Mater Des 2003;24:17782. 2 Yuxuan Li. Automobile body lightweighting research based on crashworthiness numerical simulation. PhD thesis, Shanghai Jiao Tong University, China; 2003. 3 Zhu Shi-feng, Song Qi-feng. Research of CA1092 automotive body lightening. Automob Technol Mater 2002;89:5862. in Chinese. 4 Jambor A, Beyer M. New carsnew materials. Mater Des 1997;18:2039. 5 Cheon SS, Lee DG, Jeong KS. Composite side door impact beams for passenger cars. Compos Struct 1997;38:22939. 6 Li Dong-sheng, Zhou Xian-bin. The static and dynamic dent resistance of automobile steel sheet. J Plast Eng 2003;10:325. in Chinese. 7 Li Dong-sheng, Zhou Xian-bin. The analysis on sinking stiness of double curvature auto-body panel. Chin J Appl Mech 1998;15: 1158. 8 Nader A. On strength, stiness and dent resistance of car body panels. J Mater Process Technol 1995;49:1331. 9 Dicellello JA et al. Design criteria for the dent resistance of auto- body panels. SAE 1974:38997. 10 Han Qiang, Huang Xiaoqing, Nin Jianguo. Advanced Plate and Shell Theory. New York: Science Press; 2002. 68 Y. Zhang et al. / Materials and Design 27 (2006) 6468