机械设计及其自动化（模具）英文文献及翻译

1、the effect of v-ring indenter on the sheared surface in thefine-blanking process of pawlt.s. kwak , y.j. kim , m.k. seo , w.b. baegraduate school, pusan national university, busan, south koreaabstractfinite element analysis has been performed to investigate the effect of v-ring indenter on the shear

2、ed surface in the fine blanking of pawl, which is a part of the automotive safety belt and is made of aisi1045 sheet. the cockcroft and lathams fracture criterion and the element kill method are used in order to simulate the blanking operation successfully. simulation results are obtained for variou

3、s positions and heights of the v-ring indenter, and the experimental results are compared with theoretical results. it is shown that the fem simulation results can be useful for predicting the optimal condition for fine blanking products. 2003 elsevier science b.v. all rights reserved. keywords: fin

4、e blanking; pawl; v-ring indenter; sheared surface 1. introduction fine blanking is generally used in the process for manufacturing parts of precision machines, air crafts and automobiles which require highly reliable precision products. the sheared surface of fine blanking products plays an importa

5、nt role in the dimensional precision and their function. the v-ring indenter in the fine blanking tools creates hydrostatic stress that improves the material ductility, as a result it slows down fracture. many studies on fine-blanking have been performed. lange 1 studied the effect of v-ring indente

6、r on the hydraulic stress for reducing the fracture zone. rotter and coworkers 2 performed the finite element analysis to calculate the stress distribution for the shear plane of material. guanggi et al. 3 applied a fine blanking technique to conventional blanking press by supplying v-ring indenter

7、and counter forces with additional hydraulic device. as a result, they were able to substitute 25% of conventional parts for fine-blanking parts. lazarev and kocov 4 suggested the optimum position of v-ring indenter in fine-blanking tools by using lusas fea s/w. kim et al. 5 have shown, through the

8、simple test of fine-blanking, the relationship between the v-ring position and the camber amount. lee et al. 6 developed a rigid plastic finite element code for fine blanking , and they applied it to the analysis of very thin sheet, the thickness of which is 0.18 mm. jeong et al. 7 analytically pred

9、icted the sheared surface of aisi 4340 during cutting process by deform and compared the simulation results with the experimental results. however their results were only useful for the punch clearance ratios higher than 10%. as well, their results to the material thickness, showed disagreement, bel

10、ow 2% ratio, which is generally used in fine blanking tools. this study investigates the effect of v-ring indenter to the sheared surface of the pawl, a component part of automobile safety belt. the finite element method is used to design the optimum v-ring indenter in the design process of fine bla

11、nking tools. the fem results are compared to the those of experiment for the variation of v-ring design parameters, such as the width and depth of the die-roll, the burnish zone and the fracture zone. 2. finite element analysis2.1. analysis modelfig.1 shows the analysis model used for the part of sa

12、fety belt in passenger cars.main function of the part is to tighten and loosen the belt.the material is aisi45 and the mechanical properties are shown in table 1.2.2. finite element modellingaisi 1045 with the thickness of 4.5mm is selected as the material and axisymmetic analysis is performed in th

13、e circle area in fig. 1 by deform-2d fem code. the material is assumed to be rigid plastic and isotropic because the punch clearance is very narrow and the elastic deformation can be ignored. the mechanical properties and parameters for manufacturing process are shown intable 2. table 3 represents t

14、he dominant parameters affecting the function of product, and fig.2 shows the height and position of v-ring selected as process variables. 2.3. ductile fracture criterion ductile fracture criteria have been used in many experimental studies to calculate the deformation limit for various materials. a

15、mong these criteria, cockcroft and lathams ductile fracture criterion is selected for this study. the criterion can be easily applied to various loading conditions and experimental approaches. the criterion 10 is as follows: where s is the maximum tensile stress, e the ductile-fracture strain, c the

16、 material constant, s the effective stress, e the * effective strain, s /s the stress concentration factor. eq. (1) assumes that the shearing begins when the tensile strain energy approaches its limit value. when the maxi- mum principal tensile stress remains constant, eq. (1) can be represented as

17、follows: and also eq. (2) can be approximated to eq. (3) as an in- crement in finite element analysis 11: where n is the step number and ffee represents effective strain increment of elements. therefore the boundary of cockcroft and latham can be approximated to ef = c 1_, ductile-fracture strain an

18、d it means that shearing begins when the effective strain arrives at ductile-fracture. the ductile-fracture strain is chosen 3.2 by comparing computational calculation with the experiment, for the punch clearance of 0.4% t, the v-ring indenter position of 1.27 mm, and the v-ring indenter height of 0

19、.8 mm. in order for the finite element analysis of the formation process of sheared zone during fine blanking process, the element kill method is applied. in the element kill method, an element is eliminated when its effective strain reaches the strain limit. fig.3 shows the sheared edge predicted b

20、y element kill method. the left side represents some of the killed elements when they reach limit strain, or 3.2, while the right side shows that most of the elements are killed. from figures, it can be seen that the element kill occurred first in the punch corner, then the effective strain of the d

21、ie corner reached the strain limit, and which finally make the material fracture. fig. 4 represents the sheared surface of fine-blanking product. the experiment with the punch clearance of 0.4% t, and the position and height of the v-ring indenter 1.27 and 0.8 mm, respectively. the sheared surface i

22、s divided into three categories (the width and depth of die-roll, burnish zone and the fracture zone) by magnifying it by 100 with profile projector. the categories are measured more than three times and the averages of measured values are selected. 3. results and discussion 3.1. effect of v-ring in

23、denter height fig.5 shows the relationship between the width of the die-roll and height of the v-ring indenter. the relationship between the depth of the die-roll and the height of the v-ring indenter is illustrated in fig. 6. it can be seen, from fig.6, that the width and the depth of the die-roll

24、is inversely proportional to the height of v-ring indenter. it can be said that the greater the v-ring indenter, becomes the less the gradient of rigid body rotation in the shear band occurs 12. the variation of die-roll width and depth with respect to the v-ring indenter height is shown maximum 15

25、and 22.8%, respectively.the effects of v-ring height on the fracture zone and the burnish zone are shown in figs. 7 and 8. it is found that the increase in the height of the v-ring indenter improved the condition of the shear plane. this illustrates that the higher the height of v-ring indenter is,

26、the more hydraulic pressure increases around shear band, leading to the high ductility of the shear band, which consequently improves the burnish zone 13. there was a difference between the fracture zone up to a maximum of 47.9% (fig. 6) and the burnish zone up to maximum of 5.1% (fig. 7), with resp

27、ect to the height of v-ring indenter. 3.2. effect of v-ring indenter position figs. 9 and 10 illustrate that the width and the depth of the die-roll decrease as the v-ring indenter position becomes close to the punch. however, the width of the die-roll hardly varies with the v-ring indenter position

28、, while there is a difference in the die-roll depth to a maximum of 16.4%. these phenomena can be explained by the fact that the material inux to the shear plane becomes smaller as the v-ring indenter becomes closer to the punch. it can be seen from figs. 11 and 12 that the fracture plane decreases

29、and the effective shear plane increases when the v-ring indenter approaches the punch. there are differences in the fracture plane up to maximum of 52.4% (fig. 11) and the burnish zone up to maximum of 3.4% (fig. 12), with respect to the v-ring indenter position, respectively. as the v-ring indenter

30、 approaches the shear plane, the hydraulic pressure occurring around the shear band increases, while causing high ductility of the shear band and improving the burnish zone. 4. conclusion a finite element analysis and experiment have been per- formed to investigate the effect of v-ring indenter on s

31、hear planes in the fine blanking of a part of automobile safety belt. based on the result of the study, the following major conclusions can be drawn. first, the higher the height of the v-ring indenter becomes, the finer shear plane is obtained. the higher the height of the v-ring indenter is, the m

32、ore the hydraulic stress of the shear band increases. second, the higher the height of the v-ring indenter, the smaller the width and the depth of the die-roll. therefore fine-sheared surface products are possible. third, when the v-ring indenter gets close to the punch, the burnish zone increases a

33、nd the width and the depth of the die-roll decreases. finally, the results of the fe analysis agree well with the specific experimental results in case of the punch clearance of 0.4% t, the v-ring indenter position of 1.27 mm and the v-ring indenter height of 0.8 mm.references 1 k. lange, the potent

34、ial of the fine blanking technique, feintool ag, lyss, switzerland, 1978. 2 w. konig, f. rotter, a. krapoth, feinschneiden dicker blecheexperiment und theorie, industrie-anazeiger 106 (1981) 14. 3 t. guanggi, z. pengfei, l. ronghong, jinwang, z. xiaoguang, recent development of fine blanking technol

35、ogy in china, in: proceedings of the fourth international conference on technology of plasticity, beijing, china, 1993. 4 j. lazarev, a. kocov, finite element analysis of the stress-strain condition in the process of fine blanking, in: proceedings of the inter- national manufacturing engineering conference, freund publishing co. 199960807, uk, 1996. 5 j.h. kim, j.g. ryu, j.s. choi, w.j. jung, development of fine blanking die with uid chamber and its application to produc