洪宏基Hong, Hong-Ki臺灣大學:土木工程學研究所吳國綸Wu, Kuo-LunKuo-LunWu2010-06-302018-07-092010-06-302018-07-092009U0001-1808200913292400http://ntur.lib.ntu.edu.tw//handle/246246/187694本文為探討軸扭雙向加內壓的三維應力控制下，改良以往文獻在降伏實驗的方式，並制訂降伏探尋方法以及降伏探尋的實驗流程。利用改良後的實驗方法及流程，進行一系列的降伏面探尋，討論在不同實驗路徑、實驗控制以及材料在退火態下及施加扭向預應變後降伏面的變化。對於二維降伏面與三維降伏面的實驗結果進行相關驗證與討論，發現退火態下之初始降伏面在三維應力空間中的形狀，與von Mises橢球體降伏面不同。而材料經過預應變後，在三維降伏面的剖面上有旋轉的現象。了更進一步了解材料在大變形後相關力學行為，在扭向大變形實驗中將試桿夾持狀態分為自由端與固定端，對材料在不同的夾持狀態下施加不同大小的軸向預應力進行一系列的實驗。在剪切應力應變圖中，材料在夾持狀態為自由端時隨著預應力的增加而軟化，固定端時則隨著預應力的增加而硬化。在軸向應力與剪切應變中，隨著剪切應變的增加，在前段隨著預應力的大小曲線也由上往下，而在後段，隨著預應力的增加，軸向應力隨著剪切應變下降的速度也增加。This thesis presents a complete experimental procedure to investigate the yield surface. Specimens made of aluminum alloys of Al7075 and Al6061 were tested under three-dimensional stress (strain) condition. A new definition of proof strain was introduced to determine the yield surface. The experiments of yield surface involve the determination of yield surfaces with different loading path, different control, different pre-strain and the comparison of these yield surfaces. Most experimental result found in the literature consider only two-dimensional yield surfaces. It is a challenge to determine the three-dimensional yield surfaces and it is interesting to find that yield surface rotates in three-dimensional stress space when subjected to pre-torsion.xperiments of fixed-end torsion and free-end torsion with different pre- stress were conducted to investigate the mechanical behavior of Al6061 at large deformation level. Under the condition of free-end torsion, the higher the axial pre-stress is the lower is the shear stress-strain curve, while in the case of fixed-end torsion, a higher axial pre-stress leads to a higher shear stress-strain curve. Both tensile and compressive pre-stresses were investigated.誌謝………………………………………………………………………i文摘要……………………………………………………………………ii文摘要……………………………………………………………………iii錄………………………………………………………………………iv目錄…………………………………………………………………vi目錄……………………………………………………………………vii一章 導論……………………………………………………………1-1 前言………………………………………………………………1-2 文獻回顧…………………………………………………………2-3 研究範圍………………………………………………………4二章 　實驗設備………………………………………………………62-1 實驗材料及試棒…………………………………………………62-2 實驗硬體設備…………………………………………………8 2-3 實驗軟體設備…………………………………………………12三章 　三維降伏面實驗…………………………………………………133-1 降伏定義……………………………………………………143-2 軸扭雙向二維降伏面探尋………………………………………16 3-3 實驗路徑與控制方法……………………………………………183-4軸扭雙向與環向三維降伏面探尋…………………………………20 3-5 三維降伏面討論與驗證……………………………………………21 3-6 結語………………………………………………………………25四章 　材料大變形實驗…………………………………………………27-1純扭向大變形實驗…………………………………………………27-2自由端扭向大變形實驗……………………………………………29-3固定端扭向大變形實驗……………………………………………30-5結語………………………………………………………………32五章 　結論與展望………………………………………………………345-1結論………………………………………………………………34-2展望………………………………………………………………35考文獻…………………………………………………………………37錄一 實驗程序…………………………………………………………105錄二 MTS軸扭雙向加內壓實驗程序及紀錄表單……………………108錄三 環向伸長計校正程序及紀錄表單………………………………111錄四 應變計黏貼步驟與注意事項……………………………………11321028528 bytesapplication/pdfen-US降伏面大變形預應變預應力yield surfacelarge deformationpre-strainpre-stressthesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/187694/1/ntu-98-R96521203-1.pdf