外文翻譯--復雜的級進模沖壓件采用多步展開法的毛坯設計和成形性預測（英文）

1、journal of materials processing technology 2 0 5 ( 2 0 0 8 ) 425–431journal homepage: www.elsevier.com/locate/jmatprotecBlank design and formability prediction of complicatedprogressive die stamping part using a multi-st

2、epunfolding methodZhang Zhibing ?, Liu Yuqi, Du Ting, Li ZhigangState Key Lab of Material Processing and Die fax: +86 27 87554405.E-mail address: allen@fastamp.com (Z. Zhibing).rience and simple theoretical formula. Sec

3、ondly, the shape ateach step is designed with the process sequence and all shapesare assembled into a strip. After finishing the die structuredesign with strip layout, it is very important to validate thedesign of strip

4、layout and the die structure in a real produc-tion condition to find out potential defects. It is necessary tomodify the design of strip layout and the die structure untilthe defects is removed. So it is a rather difficu

5、lt task to obtainan optimum strip layout. If the optimal blank shape and sizeat each step and the formability are predicted at the designstage, which will greatly reduce the trial and error time of thewhole progressive d

6、ie design.However, at the design stage of strip layout, intermediateshape and boundary conditions of process are unknown. It isimpossible to use finite element incremental approach to sim-0924-0136/$ – see front matter &

7、#169; 2007 Elsevier B.V. All rights reserved.doi:10.1016/j.jmatprotec.2007.11.236journal of materials processing technology 2 0 5 ( 2 0 0 8 ) 425–431 4273.1. Intermediate reference surfaceIn the calculation model, most o

8、f the intermediate referencesurface can be calculated automatically according to shapefeatures at local forming area. For example, the reference sur-face can be generated at the tangent direction along the borderof formi

9、ng area. If the forming process is more complicated,the surface can also be generated manually with experience.However, it is difficult to design the intermediate shape of eachstep in the opposite sequence of processing

10、step from finalshape to initial blank shape, especially for complex shape andforming process. When design the shape at current step, thereference surface should be generated from the shape of pre-vious step and the forma

11、bility should be validated to avoiddefects. Sometimes not only the shape and forming processof current step but also the shapes of previous steps must bemodified.At the design stage of progressive die stamping part, thed

12、esign engineers can generate relatively easily the intermedi-ate reference surface with the CAD software, such as UGNXand CATIA. It is difficult to predict precisely the interme-diate shape on the reference surface. Up t

13、o now, althoughthere are many authors try to optimize the shape of theintermediate reference surface with many optimization algo-rithms, the algorithms are only suit to the specific shape partand the optimization time is

14、 too long, which is unable tomeet the application requirements. Currently the intermedi-ate reference surface is generated by the designers and theintermediate shape is calculated using IA.3.2. Process conditionsIn the f

15、inite element model, many process conditions can beconsidered. For example, the fixed constrains will be addedat the nodes to assume that the relative displacement is verylittle at the connection area. At bending or flan

16、ging area, theinfluences of blank-holder force and friction are consideredto simulate the deformation of sheet metal. For large defor-mation at local area, the conditions treatment is differentbetween deep drawing and bu

17、lging. If the forming processis bulging, the restraint force or blank-holder force at flang-ing area is very big, the material of sheet metal is almoststiff, even fixed. If the forming process is deep drawing, therestrai

18、nt force or blank-holder force at flanging area is rela-tively slightly, the material can flow at flanging area. In MUSM,the constraint or big blank-holder force should be added on thenodes at flanging area for bulging d

19、eformation. And the properblank-holder force will be added to corresponding nodes.3.3. Strain neutral layer offsettingAs shown in Fig. 3, the strain neutral layer (SNL) (Yingping andJun, 2002) will offset from the geomet

20、ry neutral layer (GNL)to an inner layer along radial direction. Neutral layer offset-ting has a great influence on the blank shape size especiallywhen the rate between the thickness and radius of curvatureis bigger. When

21、 considering the SNL offsetting in MSUM, theshape size calculated and the experimental result will be moreclosely.Fig. 3 – Strain neutral layer offsetting.3.4. Procedure of MUSMAs we know, material of sheet metal will fl

22、ow in a different wayfor different stamping process, and the formability of the finalpart will be also different. The sequence of MUSM must meetwith the requirement of actual stamping process in strip lay-out. Therefore,

23、 the stamping process must be designed firstlyaccording to the geometry feature and process requirementof the final part. Secondly, the intermediate shape will be cal-culated using MUSM. And the formability will be evalu

24、ated toavoid the defects such as crack and wrinkling. The referencesurface and boundary conditions should be modified until theformability is perfect.Sometimes the surface should be modified again if theshapes calculated

25、 at previous steps are not good from thefull view of the strip layout. Finally, the optimum strip lay-out will be obtained after modify the stamping process manytimes.3.5. Formability analysisThe distribution of various

26、physical quantities and the defor-mation of the inner holes can be calculated with the results.And the formability can be predicted to assist the design ofthe stamping process.3.6. LimitationsThe influence of restriking

27、and springback are ignored duringunfolding process, and there are errors of the simulation resultfor the choice of shell element, which cannot simulate thedeformation of restriking and springback precisely.4. Examples4.1

28、. Example 1: Aided design of strip layoutAs shown in Fig. 4(a), the dominating forming process of a pro-gressive die forming part involves bulging, bending, flangingand restriking. The strip layout is assembled with six