机械毕业设计英文外文翻译30薄板冲压件焊装夹具设计方法副本.docx

1、机械毕业设计英文外文翻译30薄板冲压件焊装夹具设计方法 副本附 录附录A 英文文献On Welding-Installation Fixtures Design of Sheet StampingAbstract: Due to forming error and compliance of stamp-ing, the fixture design of sheet stamping assembly is different from the fixture design of common machining component. In recent years, the new pri

2、nciples and algorithms of fixture design of sheet stamping have been developed. In the paper, the concept of shape closure and force closure, screw theory were firstly introduced. Secondly, the deterministic locating and total fixturing conditions were derived. Thirdly, an “N-2-1”locating principle

3、and optimal design method for sheet stamping were described. Finally, the varia-tional method of robust fixture configuration design for 3-D workpieces was discussed. It can be predicated that the locating error can be reduced by this method.Key Words: Fixture; Sheet Stamping; Optimal Design; Ro-Bus

4、t DesignDue to its high productivity and material utilization, stamping is widely used in automobiles, aircraft, and various household appliances manufacturing industry. The welding assembly of stamping becomes the key process of those products manufacturing, because welding fixture not only affects

5、 the performance of productivity, but also is directly related to the quality of the product. Statistics from the U.S. auto industry show that 72% of the body manufacturing errors are from the position error of welding fixture, so how to effectively reduce and control the positioning error is essent

6、ial to improve the welding quality. Sheet stamping assembly is significantly different from general machining, which not only meets the common requirements of precise positioning, but also gives full consideration to the easy deformation of sheet metal parts and stamping manufacturing characteristic

7、s of large deviations to adapt the products quality requirements. Over the last decade, many scholars working in the design of sheet stamping assembly have proposed design theories and methods of some new sheet stamping assembly, and achieved remarkable results. At first, this paper introduces the r

8、esearch progress of fixture design, and then systematically elaborates the N-2-1 locating principle of fixture and the methods of optimal design and robust design, finally makes the conclusion.Manufacturing process (such as machining, welding, assembly and testing, etc.), the fixture is used in thre

9、e-dimensional positioning and clamping device. The central problem of fixture design is to choose the optimal positioning points and determine their best position to achieve the determine constraints positioning of work piece. If the work piece can be full restriction depending on the geometry of co

10、ntact area will, we called it shape closed; If it also have to be fully bound with friction, we called it force closure. Generally, shape closure stresses dynamic analysis, but force closure focuses on the work piece of static stability. In 1885, Reuleaux first studied the mechanism of two-dimension

11、al objects shape closure, and proved that the formation of two-dimensional objects shape closure need four anchor points 2. After that Somoff proved the formation of three-dimensional objects shape closure need seven anchor points. In 1978, Lakshminarayana 3 further proved the formation of three-dim

12、ensional objects shape closure need at least seven anchor points in the perspective of static equilibrium using algebraic theory In 1988, Nguyen researched the mechanism of the machine hands force closure 4, and in 1989 Asada and Kitagawa 5 researched the machine hands shape closure which used for c

13、onvex and concave parts Generally six positioning principles requires clamping force to make work piece fully constrained, so usually it is force closure.Over the last decade, the spiral theory” widely used in fixture design, which describes the three-dimensional motion as translating along one dire

14、ction and rotating around this axis. Originally spiral theory proposed by Ball 6, and developed by literature 7 and 8. According to spiral theory, literature 9 studied seven different types of finger contact, and suggested using finger-like shape to completely fix objects. Literature 10 using the ex

15、tended spiral theory analyzed that rigid bodys full or part restriction exist frictional clamp. Literature 11 proposed mathematical theory of fixtures automatic layout for prismatic work pieces. Literature 12 discussed the ability of different fixtures position contact preventing work pieces from sp

16、iral movement, and proposed a restrict method of work piece movement for the fixture design. Using small spiral model literature 13 discussed the positioning errors of fixture impact work pieces geometry accuracy. Literature 14 researched surface contact and friction problems in the analysis of fixt

17、ure restriction. Considering dynamic constraints, completely clamping, and tool path errors, literature 15 developed fixture design and analysis software. It can be said that spiral theory of fixture design has been used for determining position, full clamping, contact type, and friction problems an

18、d achieved remarkable results.Lots of literatures focus on the fixture design of rigid pieces, but the fixture design of flexible sheet pieces is rarely involved, especially considering the deformation of the work piece under processing loads is almost none. In fact, as in the aviation industry and

19、the automotive industry, the deformation of sheet may result in serious bias. For easily deformed sheet, positioning fixture not only has basic functions that limiting rigid body motion, but also must be able to limit excessive deformation of the work piece. The research that earlier considering the

20、 rigidity of work pieces or fixture positing cell will be found in the literature 16 based on the experimental results they studied fixture stiffness and wears effects on the size accuracy. Literature 17 proposed a finite element model of the fixture system for flexible positioning fixture, and the

21、power in process of processing can be seen as the force acting on the node. Based on this model, you can calculate the deformation of the work piece, the clamping force, stress distribution and friction between the work piece and fixture positioning units contact points can be calculated by Coulombs

22、 law. Although by considering the deformation of the work piece and the finite element analysis this area have been promoted, but it has neither proposed any specific positing principle, nor proposed positioning scheme for flexible sheet. In addition, this model does not combine the finite element a

23、nalysis results of the work piece with the fixture design; it is more than the analysis of the work piece other than fixture design. Literature 18 proposed a analysis method of sheet fixture positing, they studied the fixture positioning system using the case and flat three-point and four-point to p

24、osit, so the fixture layout must make the stress in the work pieces below the yield stress. However, this method does not solve the essential problem of sheet fixture, because reducing deformation is the key to the positioning of sheet. Based on literature 17, literature 19 continued further study,

25、that using the finite element modeling to choose fixture layout makes the deformation minimum in the first base-level. To determine the optimal fixture layout, using quasi-Newton optimization algorithm makes the deformation squares on the finite element mesh of the key nodes minimum. Design variable

26、s are the three anchor points on the first base required by 3-2-1 principle.Sheet stamping assembly fixtures are widely used in automobiles, aircraft and household appliances industries, whose design quality directly affects the entire product manufacturing deviations. Due to sheet metal stampings c

27、haracteristic of flexibility and manufacturing variations, the principle of traditional fixture design can not meet the design requirements, although the research of fixture design is already quite mature and the positioning principle of rigid part and the spiral theory has been in-depth study. N-2-

28、1 Location principle, for the characteristic of easy deformation on the horizontal of Sheet Metal Stamping, presents that when the number of anchor points is more than 3 in the first base surface, position effect depends not only on the number of anchor points, but also on the arrangement of the anc

29、hor points. Apart from that, it proposes the finite element analysis and the design of nonlinear programming method of the anchor, which provides theoretical basis and design methods for the design of sheet welding fixture. Because of the larger manufacture size deviation of sheet metal parts and th

30、e remarkable effect of the choice of anchor position for position deviation, robust fixture design can significantly improve the positioning error. Therefore, during the design of sheet welding fixture, implementing the N-2-1 location principle and robust design method is extremely important. It has

31、 been proved to have a multiplier effect.References1Li B, Tang H, Yang X,et al.Quality Design of Fixture Planning for Sheet Metal Assembly J .International Journal of Advanced Manufacturing Technology,2007,32 (7-8):690-697.2Ceglarek D, Shi J. Dimensional Variation Reduction for Automotive Body Assem

32、bly J.Manufacturing Review, 1995,8(2):139-154.3Ceglarek D, Shi J. Fixture Failure Diagnosis for Autobody Assembly Using Pattern RecognitionJ.ASME Journal of Engineering Industry,1996,118(1):55-66.4Apley D, Shi J. Diagnosis of Multiple Fixture Faults in Panel AssemblyJ.ASME Journal of Manufacturing Science and Engineering,1998,120(4):793-801.5Chang M, Gossard D C. Computational Method forDiagnosis of Variation-related Assembly Problems J . International Journal of Production Research,1998,36 (11):2985-2995.6Liu Y, Hu S. Assembly Fixture Fault Diagnosis Using Desig