複合板材壓縮成形之研究

本研究提出三種分析方法，已結合雙層複合板材與已結合三層複合板材壓縮成形之塑性變形行為與特性，一為切片法，二為上界限法，三為有限元素法。假設上下模具之摩擦為定剪摩擦及庫倫摩擦，上下模具可假設不同。利用上界限法(限定剪摩擦下)可求出板材外表面之形狀及壓縮負荷。然而應力分佈無法由上界限法求出，可由切片法求得。本研究以切片法及上界限法分別建立數學模式，探討各種壓縮條件，例如複合板厚比、剪降伏應力比、摩擦因子比或摩擦係數比、板寬板厚比及壓下率，對於各種應力分佈及壓縮負荷之影響。使用有限元素模擬及田口方法來探討複合板材壓縮成形，以田口法L9(34)直交表進行實驗規劃，包含有4種不同的控制因子，如複合板厚比、剪降伏應力比、摩擦因子比或摩擦係數比及板寬板厚比，加以探討複合板材壓縮特性之影響，並求得複合板材自由端表面均勻變形之最佳化的實驗參數。對於複合板材壓縮成形最佳化，本研究以SUPERFORM商用軟體進行有限元素模擬，模具與複合板材之間的摩擦假設為定剪摩擦及庫倫摩擦。複合板材成形後外表面形狀，等效應力、等效應變、速度場、壓力分佈及壓縮負荷可由有限元素法加以模擬。為了驗證有限元素模擬結果，可與切片法及上界限法相互比較。相互比較壓縮負荷以驗證有限元素模擬之可行性。有效的調整各種壓縮條件以控制複合板材側表面之均勻變形以易於複合板材之二次加工，分析結果可提供鍛造工業之參考。

關鍵字

已結合複合板材；切片法；上界限法；有限元素模擬；剪降伏應力比；複合板厚比

並列摘要

The study proposes three analysis methods to explore the plastic deformation behaviour and characteristics of two-layer and three-layer bounded clad sheet ; one is Slab Method ,the second one is Upper Bound Method , and the third is Finite Element Method. The frictions of top and bottom dies are assumed as constant sheet friction. And coulomb friction , and those can be different. The shape of outer surface and the compression force can be obtained by the upper bound method , however the stress distributions can not be found , those are able to get by the slab method. The mathematical models based on the slab method and upper bound method are established to investigate the effects of various compression conditions such as clad thickness ratio, shear yield stress ratio, and reduction on various stress distributions and compression forces. Using the FEM simulation and Taguchi method to explore the compression forming of clad sheet ; and to carry out the experimental plan by L9(34) orthogonal array which includes four various. Control factors the clad thickness ratio, the shear yield stress ratio, the frictional factor ratio or frictional coefficient ratio and the width thickness ratio to explore the effects of the compression characteristics of clad sheet. For the optimization of compression forming of clad sheet, the SUPERFORM commercial software is used to perform the FEM simulation with constant shear friction and Coulomb friction. The shape of outer surface of clad sheet, the equivalent stress, the equivalent strain, the velocity field, the pressure distribution and the compression force can be simulated by the FEM. With a view to verifying the results of FEM simulation, the results can be compared to those based on the slab method and the upper bound method. The acceptance of FEM simulation can be verified by the comparisons of compression forces. Adjusting effectively various compression conditions to control the shape of outer surface to be uniform, the clad sheet is apt to perform the second forming. The analysis results can be offered to the forging industries at the reference.

並列關鍵字

bounded clad sheet ； slab method ； upper bound method ； finite element simulation ； shear stress ratio ； clad thickness ratio

參考文獻

[3] Wagomer, R. H., 1996, “Fundamentals of Metal Forming”, Wiley, New York.

[4] Shabaik, A. H., 1971, “Prediction of the Geometry Changes of Free Boundary During Upsetting by the Slip-Line Theory,” J. Eng. Ind. Vol. 93, p. 586.

[5] Wang, J. P., 1997, “The Slip-Line Function Model Approach to Plane Dynamic Analysis of Visioplasticity,” J. Mater. Process. Technol. Vol. 74, p. 1.

[6] Wang, J. P., Tsia, Y. H., Wang, J. J., 1997, “The Dynamic Analysis of Visioplasticity for the Plane Upsetting Process by the Flow Function Element Technique,” J. Mater. Process. Technol. Vol. 63 p. 738.

[7] Wang, J. P., 2000, “A New Approach to Visioplasticity in Dynamic Plane Upsetting,” Comput. Meth. Appl. Mech. Eng. Vol. 190 p. 1689.

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複合板材壓縮成形之研究

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