高應(yīng)變率下TC4-DT鈦合金的動(dòng)態(tài)力學(xué)性能及塑性本構(gòu)關(guān)系Dynamic mechanical property and plastic constitutive relation of TC4-DT Ti alloy under high strain rate

為研究TC4-DT鈦合金的動(dòng)態(tài)力學(xué)性能及其本構(gòu)關(guān)系，在1000~8000 s^-1應(yīng)變率范圍內(nèi)，利用分離式Hopkinson壓桿試驗(yàn)裝置對(duì)該材料進(jìn)行動(dòng)態(tài)壓縮試驗(yàn)，得到高應(yīng)變率下的真實(shí)應(yīng)力-應(yīng)變曲線。結(jié)果表明：高應(yīng)變率時(shí)TC4-DT鈦合金材料存在應(yīng)變率增強(qiáng)、增塑以及應(yīng)變強(qiáng)化效應(yīng)，其流變應(yīng)力表現(xiàn)出較強(qiáng)的應(yīng)變率敏感性。通過(guò)微觀組織觀察，發(fā)現(xiàn)高應(yīng)變率變形時(shí)出現(xiàn)絕熱剪切帶是材料流變應(yīng)力急劇減小的主要原因。改進(jìn)Johnson-Cook本構(gòu)模型中的溫度項(xiàng)，利用試驗(yàn)數(shù)據(jù)對(duì)TC4-DT鈦合金在高應(yīng)變率下的動(dòng)態(tài)塑性本構(gòu)關(guān)系進(jìn)行擬合，得到室溫下該材料的動(dòng)態(tài)塑性本構(gòu)方程，模型計(jì)算結(jié)果和試驗(yàn)結(jié)果證明該模型可以更好地預(yù)測(cè)TC4-DT鈦合金高應(yīng)變率下的塑性流變應(yīng)力。

The dynamic compression experiments of TC4-DT Ti alloy were performed at a range of strain rate from 1000 s^-1 to 8000 s^-1 by high split Hopkinson pressure bar for investigating its dynamic mechanical property and constitutive relation, and the true stress-strain curves under high strain rates were obtained. The results show that the true flow stress of TC4-DT is sensitive to the strain rates and TC4-DT has strain rate strengthening, plasticity-increasing and strain work-hardening. The observation of cross-section microstructure of deformed sample reveals that the adiabatic shear band is responsible for the rapid reduction of flow stress when TC4-DT was deformed at high strain rate. Based on the Johnson-Cook constitutive model, with new temperature item, the dynamic constitutive model of TC4-DT was obtained by fitting the experimental results. The comparison between the calculated curves and experimental results shows that the present dynamic constitutive model can make a better prediction of the plastic flow stress.

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