(1. 中國(guó)工程物理研究院 總體工程研究所，綿陽(yáng) 621999；
2. 中國(guó)科學(xué)院 材料力學(xué)行為和設(shè)計(jì)重點(diǎn)實(shí)驗(yàn)室 中國(guó)科學(xué)技術(shù)大學(xué)近代力學(xué)系，合肥 230027)
摘 要: 利用MTS、中應(yīng)變材料試驗(yàn)機(jī)和分離式霍普金森拉桿獲得TC11鈦合金在應(yīng)變率1×10-3~1×103 s-1范圍內(nèi)的應(yīng)力-應(yīng)變曲線，利用金相顯微鏡和掃描電子顯微鏡觀察材料組織和斷口形貌，基于修正的Johnson-Cook本構(gòu)模型進(jìn)行不同應(yīng)變率下拉伸力學(xué)行為的有限元數(shù)值模擬。結(jié)果表明：TC11的初始屈服行為表現(xiàn)出明顯的應(yīng)變率強(qiáng)化特性，在中應(yīng)變率范圍內(nèi)呈現(xiàn)出應(yīng)變率不太敏感向應(yīng)變率敏感的轉(zhuǎn)折現(xiàn)象，材料的應(yīng)變硬化率隨著應(yīng)變率的提高而逐漸降低。TC11的α晶和片層α+β束被拉長(zhǎng)，呈現(xiàn)韌性斷裂機(jī)制。修正Johnson-Cook模型計(jì)及應(yīng)變率對(duì)初始屈服應(yīng)力和應(yīng)變硬化行為的不同影響，數(shù)值計(jì)算曲線與試驗(yàn)曲線吻合較好，能夠較好地應(yīng)用于TC11應(yīng)變率相關(guān)力學(xué)行為的數(shù)值仿真。
關(guān)鍵字: 鈦合金； 應(yīng)變率； 本構(gòu)模型
（1. Institute of Systems Engineering, China Academy of Engineering Physics, Mianyang 621999, China;
2. CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei 230027, China）
Abstract:The MTS809 machine, moderate strain-rate testing setup and the split hopkinson bar system were adopted to conduct uni-axial tension tests of TC11 at strain rates ranging from 1×10-3 s-1 to 1×103 s-1. The observation of microstructure and the fracture morphology was carried out via the optical microscope and SEM. A modified Johnson-Cook model was proposed to predict the mechanical behavior. Experimental results indicate that there is a positive strain-rate sensitivity with respect to the initial yield behavior. However, the transition of rate dependent sensitivity is presented at the moderate-rate loading conditions. The α grains and α+β colonies are stretched along the tension direction and break in a manner of ductile fracture. The modified Johnson-Cook constitutive model incorporates the different strain rate effects on the yield stress and strain hardening behavior. Excellent agreement between the experimental data and model predication indicates that such model is suitable for the rate-dependent numerical simulation of titanium alloy TC11.
Key words: titanium alloy; strain rate; constitutive model
