聚晶體模型於金屬薄板表面粗糙化與精微成形之應用

Abstract

本研究利用聚晶體模型導入有限元素分析套裝軟體，撰寫使用者副程式針對金屬材料之行為進行研究。藉由掃描式電子顯微鏡(scanning electron microscope，SEM)搭配背向散射電子繞射(electron backscatter diffraction，EBSD)取得1050-O鋁合金試片之晶粒形貌與組織結構。首先採用平面應變元素模型檢驗厚度方向元素層數與空間中晶粒優選方位(grain orientation)分布對於金屬薄板表面粗糙度之影響，接續採用實體元素模型置入實驗量測取得之晶粒優選方位，展現試片沿橫向方向與縱向方向進行單軸拉伸之表面輪廓，施予不同壓力於承受預應變之金屬薄板表面，檢視薄板表面粗糙度變化情形，模擬結果並與相對應實驗數據進行比較。分析模型進一步依據實際晶粒形貌進行網格分割，觀察其於表面輪廓之影響。 聚晶體模型亦應用於精微成形模擬，分別探討具備不同初始晶粒優選方位之不鏽鋼薄板，其於精微沖壓製程所呈現之厚度分布，模擬結果並與文獻中相對應實驗進行比較。分析結果顯示具備明顯織構(texture)之分析模型，其薄板成形厚度變化情形大致與量測數據相符。亦指定不同晶粒優選方位置入方式於分析模型，檢視其於薄板成形厚度之差異。

A Taylor-type crystalline plasticity model, implemented into the commercial finite element analysis software, is coded as a subroutine to investigate behaviors of an aluminum alloy with a face-centered cubic structure, in the present study. An optical microscope with an electron backscatter diffraction technique is used to evaluate grain morphology and microtexture of a metal sheet. A plane-strain model is adopted to examine the effects of the number of element layers through the thickness and spatial distribution of crystallographic orientations on the roughness of the sheet. Surface profiles of the textured sheet, subjected to the uniaxial tensile in the longitudinal and the transverse direction, are evaluated by using a solid model. Various values of pressure are subsequently prescribed on the pre-strained sheet to explore deviations of the surface roughness. Measured grain morphology and microtexture are further implemented into the simulations here. Numerical results are also compared with the associated experimental measurements reported in the literature. The crystalline plasticity model is also applied to investigate the behavior of a stainless steel sheet here. Thickness variations of the sheet are examined under the micro-groove formation procedures. Effects of the spatial distribution of crystallographic orientations and orientation assignment approach adopted in the simulations on the thickness distribution over the sheet are demonstrated. Numerical results, based on the sheet with textured orientations, are in good agreement with the corresponding experimental measurements reported in the literature.