基于修正Johnson-Cook模型的鈦合金熱黏塑性動(dòng)態(tài)本構(gòu)關(guān)系及有限元模擬

基于修正Johnson-Cook模型的鈦合金熱黏塑性動(dòng)態(tài)本構(gòu)關(guān)系及有限元模擬Thermal-viscoplastic constitutive relation of Ti-6Al-4V alloy and numerical simulation by modified Johnson-Cook modal

為了準(zhǔn)確描述鈦合金在高應(yīng)變率、高溫載荷下的熱粘塑性本構(gòu)行為，以及因材料內(nèi)部出現(xiàn)絕熱剪切帶而導(dǎo)致材料流變應(yīng)力減小的定量關(guān)系，構(gòu)造功熱轉(zhuǎn)換系數(shù)β與應(yīng)變率 之間的函數(shù)關(guān)系，提出一種基于修正Johnson-Cook模型的鈦合金熱粘塑性動(dòng)態(tài)本構(gòu)關(guān)系，并通過以最小二乘法為目標(biāo)函數(shù)的局部搜索優(yōu)化算法，對(duì)基于實(shí)驗(yàn)數(shù)據(jù)的本構(gòu)參數(shù)進(jìn)行快速優(yōu)化識(shí)別。最后利用應(yīng)力補(bǔ)償更新算法，通過顯式用戶子程序VUMAT將熱黏塑性本構(gòu)模型嵌入ABAQUS軟件中，得到Ti-6Al-4V鈦合金在不同應(yīng)變率、溫度條件下的單軸動(dòng)態(tài)應(yīng)力-應(yīng)變曲線。數(shù)值模擬結(jié)果與實(shí)驗(yàn)數(shù)據(jù)吻合良好，表明該修正模型能準(zhǔn)確描述鈦合金高應(yīng)變率下的熱黏塑性變形，可適用于各種應(yīng)變率下鈦合金本構(gòu)行為的描述。

In order to accurately describe the thermo viscoplasticity constitutive behavior of titanium alloy under high strain rate and elevated temperature, a modified Johnson-Cook equation was proposed by constructing function of conversion coefficient about strain rate. And the quantitative relation between decreasing flow stress and adiabatic shear band appeared in the material was analyzed. All the constitutive parameters could be quickly identified by the local search optimization algorithm taking least squares method as the object function. By adopting a stress compensation updating algorithm, a subroutine VUAMT of the proposed constitutive model was programmed on plat of ABAQUS/Explicit. The finite element simulation of dynamic responses of Ti-6Al-4V titanium alloy under different strain rates and temperatures are obtained. The modified Johnson-Cook modal can accurately describe the thermo viscoplasticity dissipation due to good agreement between simulation results and experimental data. The subroutine VUAMT and applicability of constitutive description for titanium alloy under various strain rates were verified.

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