沖頭圓角與母模圓角對中碳鋼精密剪斷加工面影響之有限元素分析

Abstract

剪斷加工依設備、技術的不同，可分為傳統剪斷及精密剪斷方法。精密剪斷是一種不須修邊、銑削等二次加工，即可獲得平滑斷面的金屬成形方法，其光滑的剪斷面、良好的製品平坦度等特性，相較於傳統剪斷製品有著許多優點。就經濟效益而言，精密剪斷技術是適合大量生產性質的加工技術，但模具材料選擇、模具的設計及製造較傳統剪斷更為複雜。精密剪斷製程的加工參數有很多，像沖頭與模具間隙、壓板與逆壓板荷重和V-ring的設計等都會影響剪斷後產品的斷面形狀和平坦度之特性。 本研究以有限元素法為基礎，根據Cockroft-Latham’s破壞準則提出一個評估方法以判斷破壞型態的改變，並根據此方法來探討沖頭圓角半徑和模具圓角半徑這兩個加工參數對工件斷面形狀的影響。由本研究結果得知在使用AISI 1045厚3.6mm的材料，欲加工直徑20mm之圓形料片，及使用V型壓環深度為1.2mm、角度60度、距剪切邊1.8mm時，最佳參數為：沖頭圓角半徑為0.05mm、模具圓角半徑為0.55mm、壓料板荷重為500KN、及逆壓料板荷重為70KN。

Blanking can be divided into conventional blanking and fine blanking. Fine blanking is one of the sheet metal forming technique which produces smooth shearing surface without the need of secondary finish. Compared with conventional blanking, fine blanking provides products with better shearing surface and better flatness. Nevertheless, it is more complicate in selection of the die material, to design and manufacture the die. Factors affecting the fine blanking products characteristics include punch-die clearance, blank holder load, counter punch load…and so on. In this thesis, Cockcroft & Latham’s fracture criterion was incorporated in the finite element analysis package for determine the quality of shearing surface. Effects of the punch radius and die radius on the shearing surface quality were discussed. The results show that the best punch radius is 0.05mm and the best die radius is 0.55mm to get maximum burnish zone under specific conditions described in this thesis.