臺灣大學: 土木工程學研究所洪宏基鄭仲邑Cheng, Chung-YiChung-YiCheng2013-04-012018-07-092013-04-012018-07-092011http://ntur.lib.ntu.edu.tw//handle/246246/255547本文探討在軸扭雙向應變以及環向應力控制下，鋁合金Al6061在三維應力空間上降伏面的演化現象。利用改良自檢驗應變法所制訂出降伏點判定方法以及自動化實驗流程進行一系列的降伏面探尋,並討論在不同預加載路徑下接續降伏面在(σ_θz-σ_θθ)、(σ_zz-σ_θθ)與(σ_zz-σ_θz)應力空間上的演化現象。實驗結果發現在(σ_θz-σ_θθ)應力空間上，扭向預加載路徑會引致降伏面旋轉，但在軸向或環向預加載路徑下降伏面則不會有旋轉現象產生；在(σ_zz-σ_θθ)應力空間上，降伏面的旋轉與軸向預加載路徑有關，而與扭向或環向預加載路徑無關。另外為了瞭解在(σ_θz-σ_θθ)應力空間上軸扭交互作用之預加載路徑下的接續降伏面與扭向預加載路徑下的接續降伏面之相異處，實驗中探討不同比例與非比例預加載路徑下降伏面的演化現象，結果發現軸向預加載路徑不會影響降伏面因扭向預加載路徑所引致的旋轉現象。本文最後將同一預加載路徑下在各應力平面空間上 降伏面資料點做整理，擬合出三維應力空間上的降伏面，並觀察到在扭向預加載路徑下的接續降伏面以軸向應力為軸做旋轉，而在軸向預加載路徑下的接續降伏面則以扭向應力為軸做旋轉。This thesis studies the evolution of yield surfaces for Al6061 under strain control in the axial and torsional directions and stress control in the hoop direction. A new method of automated yield stress probing is based on proof strain and used in the determination of yield surfaces. The experimental determination of the subsequent yield surfaces in (σ_θz-σ_θθ), (σ_zz-σ_θθ) and (σ_zz-σ_θz) spaces after proportional and non-proportional loading paths were conducted to investigate the evolution of the yield surfaces. The experimental result showed that the rotation of the subsequent yield surfaces in the (σ_θz-σ_θθ) space was dependent on torsional pre-loading paths, and in the (σ_zz-σ_θθ) space, the subsequent yield surfaces of axial pre-loading paths showed obvious rotation. Finally, 3D yield surfaces of different pre-loading paths constructed by using the data of the yield points in the (σ_θz-σ_θθ), (σ_zz-σ_θθ) and (σ_zz-σ_θz) spaces were conducted to investigate the evolution of the yield surfaces in the 3D stress space. The result showed that the subsequent yield surfaces of torsional pre-loading paths rotated around the σ_zz axis , and the subsequent yield surfaces of axial pre-loading paths rotated around the σ_θz axis in the 3D stress space.19367592 bytesapplication/pdfen-US降伏面三維應力空間預應變預應力走動硬化等向硬化降伏面旋轉yield surfacesubsequent yield surface3D stress spacekinematic hardeningisotropic hardeningpre-strainpre-stressrotation of yield surfacethesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/255547/1/ntu-100-R98521245-1.pdf