——變形行為模擬
(中南大學 粉末冶金國家重點實驗室， 長沙 410083)
摘 要: 通過有限元模擬和坐標網(wǎng)格， 對純鋁等徑角擠過程的變形行為進行了模擬和試驗。 結(jié)果表明, 純鋁在單道次等徑角擠壓過程中所需的載荷隨著樣品位移的增加大致可分為快速增加、 緩慢增加、 快速增加、 載荷值趨于穩(wěn)定、載荷下降5個階段。 由于樣品外部在主要變形區(qū)的流動速率比樣品內(nèi)部的快， 因而樣品在等徑角擠壓過程中會出現(xiàn)不均勻變形， 樣品底部沿寬度方向的塑性變形量明顯少于樣品頂部和中部的，坐標網(wǎng)格法實驗結(jié)果也證明了這一點。 在等徑角擠壓過程中， 樣品不同部位的應力狀態(tài)不一致， 樣品內(nèi)部存在壓應力→拉應力的轉(zhuǎn)變， 樣品外部存在壓應力→拉應力→壓應力的轉(zhuǎn)變。 摩擦消除后， 有效應變有所增加， 但并不能降低樣品變形的不均勻性； 采用尖角模具既能產(chǎn)生更大的剪切應變，又能提高變形的均勻性。
關(guān)鍵字: 等徑角擠； 數(shù)值模擬； 變形行為
——Simulation of deformation behavior
（State Key Laboratory for Powder Metallurgy,
Central South University, Changsha 410083, China）
Abstract:The computer simulation and experiments for the deformation behavior of pure Al in equal channel angular pressing (ECAP) process were conducted by finite element method (FEM) and coordinate network. The results show that the load required to drive the deformation varies with increasing the displacement, according to the following five steps: rapid increase, slowly increase, another rapid increase, stabilizing and decrease. Inhomogeneous deformation exists in the width direction of the sample, and the plastic deformation in the end of the sample is smaller than that in the top and that in the center. The coordinate network experiment verifies this phenomenon. This inhomogeneity is attributed to the fact that the strain rate in the outer side of the sample is faster than that in the inner side. During ECAP process, the stress state in different positions of the sample is different. In the inner side of the sample, there is a stress transition from compressive to tensile state; while in the outer side there is a transition from compressive to tensile and finally to compressive state. The simulation also indicates that elimination of abrasion can not ameliorate the deformation inhomogeneity, but can increase the effective strain; with closed mould, lager and more homogeneous shear deformation can be obtained.
Key words: equal channel angular pressing; computer simulation; deformation behavior
