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1、毕业设计外文翻译原文. Optimum blank design of an automobile sub-frame Jong-Yop Kim a ,Naksoo Kim a,*,Man-Sung Huh b a Department of Mechanical Engineering,Sogang University,Shinsu-dong 1,Mapo-ku,Seoul 121-742,South Korea b Hwa-shin Corporation,Young-chun,Kyung-buk,770-140,South Korea Received 17July 1998 Abst
2、ract A roll-back method is proposed to predict the optimum initial blank shape in the sheet metal forming process.The method takes the difference between the ?nal deformed shape and the target contour shape into account.Based on the method,a computer program composed of a blank design module,an FE-a
3、nalysis program and a mesh generation module is developed.The roll-back method is applied to the drawing of a square cup with the ange of uniform size around its periphery,to con?rm its validity.Good agreement is recognized between the numerical results and the published results for initial blank sh
4、ape and thickness strain distribution.The optimum blank shapes for two parts of an automobile sub-frame are designed.Both the thickness distribution and the level of punch load are improved with the designed blank.Also,the method is applied to design the weld line in a tailor-welded blank.It is conc
5、luded that the roll-back method is an effective and convenient method for an optimum blank shape design.#2000Elsevier Science S.A.All rights reserved. Keywords:Blank design;Sheet metal forming;Finite element method;Roll-back method 1.Introduction It is important to determine the optimum blank shape
6、of a sheet metal part.However,because its deformation during the forming process is very complicated,it is not easy to design the optimum blank shape even by the skilled labor based on the experience of many years.Recently,computa-tional analysis for a complex automobile part has been able to be car
7、ried out easily due to improved computer perfor-mance and the numerical analysis technique.In the analysis process,all kinds of variables that affect the deformation should be considered.The optimum blank shape leads to the prevention of tearing,uniform thickness distribution and to the reduction of
8、 the press load during drawing.If the blank shape is designed optimally,the formability will be increased and the ?nal product will require the least amount of trimming at the end of the process.Therefore,it is desirable to design the blank shape with a uniform ange of its periphery after deep drawi
9、ng. Several numerical solutions for the deep drawing process of non-circular components have been reported.Hasek and Lange 1gave an analytical solution to this problem using the slip-line ?eld-method with the assumption of plane-strain ange deformation.Also,Jimma 2and Karima 3used the same method.V
10、ogel and Lee 4and Chen and Sowerby 5developed ideal blank shapes by the method of plane-stress characteristics.Sowerby et al.6developed a geometric mapping method providing a trans-formation between a at sheet and the ?nal surface. Majlessi and Lee 7,8developed a multi-stage sheet metal forming anal
11、ysis method.Chung and Richmond 912determined ideal con?gurations for both the initial and the intermediate stages that are required to form a speci?ed ?nal shape using the ideal forming theory.Lee and Huh 13introduced a three-dimensional multi-step inverse method for the optimum design of blank shap
12、es.Toh and Kobayashi 14developed a rigidplastic ?nite-element method for the drawing of general shapes based on membrane theory and ?nite-strain formulations.Zhaotao 15used the boundary element method for a 2D potential problem to design optimum blank shapes. This paper presents an optimum design me
13、thod of blank shapes for the square cup drawing process considering process variables.An optimum blank shape of square cup drawing was obtained using the proposed method.Also,it was applied to the deep drawing of an automobile sub-frame,and an optimum blank shape with a uniform ange at its periphery
14、 were determined. Journal of Materials Processing Technology 101(20003143 * Corresponding author.Tel.: 82-2-705-8635;fax: 82-2-712-0799.E-mail address :nskimccs.sogang.ac.kr (Naksoo Kim 0924-0136/00/$see front matter #2000Elsevier Science S.A.All rights reserved.PII:S 0924-0136(9900436-7 2.Design of
15、 optimum blank shape The de?nition of the optimum blank shape is the mini-mization of the difference between the outer contour of the deformed blank and the target contour that indicates the residual ange of uniform size around the periphery of the product.The target contour is generated from the ou
16、ter contour of the product and determines an optimum blank shape using the results of ?nite-element simulation with the roll-back method.In the process of blank design the simula-tion is performed using an explicit ?nite-element software PAM-STAMP and the interface program is developed for con-necti
17、ng the blank design module,the remeshing module,the post-processor module and the FE-analysis package.2.1.Roll-back method The roll-back method starts by de?ning the target con-tour.After determining the length of the ange that remains around the periphery of the product,the pro?le of the target con
18、tour is created by offsetting an equal distance from the outer contour of the product and its mesh system is gener-ated by beam elements.The process of blank design is illustrated in Fig.1.The mesh system of the prepared square blank for initial analysis is shown in Fig.1(a.After an analysis,the mes
19、h system of the deformed blank and the target contour are shown in Fig.1(b.At the ange of the deformed blank,a distinction is made between the interior ange within the target contour and the exterior ange out of the target contour.The ange out of the target contour is the part that will be trimmed a
20、nd the ange within the target contour is the part which does not keep shape is due to the incompletion of the blank shape.Thus the modi?ed blank shape should be designed to take the shape of the outer contour of the product completely.The contour of the modi?ed blank shape using the roll-back method
21、 and the initial blank shape is shown in Fig.1(c.The mesh system of the modi?ed blank shape for FE-analysis is shown in Fig.1(d. The blank design method will be introduced in detail.The quarter of the deformed blank and the target contour are shown in Fig.2(a.According to the previous explanation,th
22、e remained ange can be divided into the interior and the exterior ange. The design process of region A is shown in Fig.2(b.In the mesh of the deformed blank a square grid IJKL on the target contour will be considered,and then the internal dividing point Q in will be calculated at the ratio of m to n
23、 Fig.1.Illustrating the process of ?nding the optimum blank:(ainitial blank shape;(bdeformed blank and target contour;(croll-back blank and contour;(dmodi?ed blank shape. Fig.2.The roll-back process of a mesh located on the surface of the ange:(aa mesh located on the surface of the ange;(bregion A:r
24、esidual drawing part out of target contour;(cregion B:residual drawing part inside the target contour. 32J.-Y.Kim et al./Journal of Materials Processing Technology 101(20003143 between the node J and K.This point is mapped back into the mesh system of the initial blank.The internal dividing point Q
25、H in is calculated at the ratio of m to n between the same node J H and K H.The following process is performed on the element of the deformed blank on the target contour.The describing point of the outer contour of the modi?ed blank shape can be calculated.If the coordinates of the nodes J and K are
26、 J(x1,y1,K(x2,y2and the coordinates of the nodes J H and K H are J H x H1Y y H1 Y K H x H2Y y H2 ,the ratio of m to n is m X n JQ JK X QK JK (1 The coordinate of the internal dividing point Q H in can be expressed as Q H in mx H2 nx H1 m n Y my H2 ny H1 m n (2 The design process of region B is shown
27、 in Fig.2(c.In the mesh of the deformed blank a square grid MNOP of which the outward edge crosses the target contour should be considered,and then the external dividing point Q out can be calculated at the ratio of m to n between nodes O and P.This point is mapped back into the mesh system of the i
28、nitial blank.The external dividing point Q H out can be calculated at the ratio of m to n between the same nodes Q H and P H.If the coordinates of the nodes O and P are O(x1,y1,P(x2,y2and the coordinates of the O H and P H are O H x H1Y y H1 Y P H x H2Y y H2 ,the ratio of m to n is m X n OQ OP X QP
29、OP (3 The coordinate of the external dividing point Q H out can be expressed as Q H out mx H2nx H1 Y my H2ny H1 (4 The following process is performed on all the element of the deformed blank related on the target contour.The points describing the outer contour of modi?ed blank shape can be calculate
30、d.When all points of two cases are connected by the spline,the outer contour of modi?ed blank can be described.This process is shown in Fig.3. 2.2.The development of the optimum blank design program To optimize the initial blank shape,a design program was developed following the prescribing method a
31、nd procedures. This program consists of the blank shaper design module, the mesh generation module and the post-processor module. The whole procedure is illustrated in Fig.4.To perform the design process of a blank shape,an interface module is needed.This module is developed to read the output?le of
32、 ?nite-element analysis and design the optimum blank shape and generate the input?le.3.Designs of blank shape and application 3.1.Blank design of a square cup To verify the validity of the roll-back method,it is applied to the process of square cup deep drawing.Several numerical solutions of the dee
33、p drawing process for non-circular components have been reported recently.The pub-lished blank shapes by Lee and coworkers1618are compared with the result using the roll-back method.The Fig.3.Flow chart of the blank design module. Fig.4.Flow chart of the main program. J.-Y.Kim et al./Journal of Mate
34、rials Processing Technology101(2000314333 dimensions of the die and punch set for an analysis are shown in Fig.5. The material of the sheet metal is cold-rolled steel for an automobile part.The following are the material properties and process variables.Stressstrain relation:s 58X 78? 0X 00003 e 0X 274 kgf a mm 2 ;Lankford value:R 1X 679;initial blank size:160mm ?160mm square blank;initial thickness:t 0.69mm;friction coef?cient:m 0.123;and blank-holding force:4000kgf (1kgf 9.81N.