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Title: | 高厚徑比多道次沖孔成形之研究 Piercing of High Thickness to Diameter Ratio Holes with Multiple Operations |
Authors: | Yu-Ming Chang 張育銘 |
Advisor: | 陳復國 |
Keyword: | 沖孔,厚徑比,延性破壞準則,臨界破壞值,沖頭造型設計,多道次,CAE分析, hole-piercing,high thickness to diameter (t/D) ratio,ductile fracture criterion,critical fracture value,punch shape design,multiple operations,finite element analysis,experimental validation, |
Publication Year : | 2011 |
Degree: | 碩士 |
Abstract: | 隨著各種高科技產品的微小化與精密化,市場產品對細長孔之需求與日俱增,因此相關細長沖孔成形技術亟需提升。目前針對一般沖孔厚徑比(Aspect ratio)即t/D(t:板厚、D:沖頭直徑)較小之沖孔成形研究已趨完整,但對於厚徑比較大之沖孔技術則尚未成熟,因此高厚徑比沖孔成形之研究值得進一步的探討。
本研究首先以SPCC板材三道次高厚徑比沖孔進行臨界破壞值之驗證,除選擇較佳之延性破壞準則Normalized Cockcroft & Latham外,並獲得正確之臨界破壞值。其次探討高厚徑比沖孔與一般沖孔不同厚徑比之差異性,探討高厚徑比沖孔與一般沖孔機制之差異性,並由此差異性針對間隙、壓料力、潤滑性及不同材料進行分析探討。 由上述分析之結果,針對板材S45C高厚徑比沖孔沖頭造型及多道次進行設計,使得沖頭承受較低之沖頭力,並由沖頭受力分析可得沖頭減少承受25%之應力值。此外,本研究針對不同之製程參數,包括:間隙、壓料力及潤滑性,對高厚徑比沖孔成形之影響進行探討,並確認了較佳之製程參數。最後進行相關之實驗驗證,其結果顯示本研究之分析具有相當之準確度,可提供未來從事類似研究之參考。 With the ongoing market trend, there is a growing demand on micro products. In the manufacturing process of a micro part, the hole-piercing is commonly involved. Though the hole-piercing process with low thickness to diameter (t/D) ratio has been well-developed, the process for piercing a hole with a high t/D ratio is not yet matured. In addtion, due to the high t/D ratio, the hole usually can not be pierced in one single operation and a multi-operation process is required. In the present study, piercing of high t/D ratio holes with multiple operations was examined by both the finite element analysis and the experimental approaches. In order to facilitate the finite element analysis in determination of element elimination, the fracture criterion and the critical value for separating the materials were studied first by comparing the experimental phenomenon and the finite element simulation results. Various fracture criteria adopted by the DEFORM software were examined. The tension tests were conducted and the stretches of the specimens to fracture were recorded, comparing with those obtained from the finite element simulations. The comparison indicates that the simulation results with the Normalized Cockcroft & Latham ductile fracture criterion agree well with the experimental data. With the proper ductile fracture criterion used, the piercing mechanism for different t/D ratios was investigated. The effects of process parameters, such as the die clearance, holder force, and lubrication condition on the piercing force and cutting edge quality were determined. The multiple operations for piercing a high t/D ratio hole on a S45C sheet were then designed based on the optimum process parameters obtained from the previous study. In order to obtain a smaller punch force and acceptable cutting edge, the number of operations, die clearance and punch shape were optimized according to the finite element analysis. The actual multi-operation hole piercing process was also implemented and the experimental data are compared with those obtained from the finite element results. The efficiency and the accuracy of the analysis model developed in the present study were then validated. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/27219 |
Fulltext Rights: | 有償授權 |
Appears in Collections: | 機械工程學系 |
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ntu-100-1.pdf Restricted Access | 8.76 MB | Adobe PDF |
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