(1. 湖南大學(xué) 汽車車身先進(jìn)設(shè)計(jì)制造國(guó)家重點(diǎn)實(shí)驗(yàn)室，長(zhǎng)沙 410082；
2. 湖南大學(xué) 機(jī)械與運(yùn)載工程學(xué)院，長(zhǎng)沙 410082)
摘 要: 采用霍普金森壓桿技術(shù)對(duì)固溶態(tài)AM80鎂合金進(jìn)行大應(yīng)變率范圍下的高速?zèng)_擊實(shí)驗(yàn)，應(yīng)變速率分別為700、1100、2150、2750和3650 s-1。結(jié)果表明：實(shí)驗(yàn)用AM80鎂合金的流變應(yīng)力隨應(yīng)變速率的增加而增加，表現(xiàn)出明顯的正應(yīng)變率敏感性；當(dāng)載荷由準(zhǔn)靜態(tài)轉(zhuǎn)為動(dòng)態(tài)時(shí)，合金的流變應(yīng)力顯著增加。基于不同應(yīng)變率下的應(yīng)力—應(yīng)變曲線確定實(shí)驗(yàn)用鎂合金的Johnson-Cook(J-C)本構(gòu)方程。采用ABAQUS有限元軟件對(duì)合金的SHPB實(shí)驗(yàn)進(jìn)行了數(shù)值模擬，根據(jù)模擬得到的入射波、反射波和透射波形計(jì)算得到各應(yīng)變速率下的應(yīng)力—應(yīng)變曲線，并與實(shí)驗(yàn)及J-C本構(gòu)擬合的應(yīng)力—應(yīng)變響應(yīng)進(jìn)行對(duì)比。結(jié)果表明：即使在本構(gòu)擬合所選應(yīng)變速率范圍外，仿真分析結(jié)果也與實(shí)驗(yàn)及本構(gòu)擬合結(jié)果基本吻合；但在較高應(yīng)變時(shí)，由于本構(gòu)未考慮溫升效應(yīng)，使得擬合結(jié)果與實(shí)驗(yàn)結(jié)果的差異較低應(yīng)變時(shí)明顯要大。
關(guān)鍵字: AM80鎂合金；應(yīng)變率敏感性；Johnson-Cook本構(gòu)方程；數(shù)值模擬
（1. State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body, Hunan University, Changsha 410082, China;
2. College of Mechanical and Vehicle Engineering, Hunan University, Changsha 410082, China）
Abstract:High speed impact experiments of a solution treated AM80 magnesium alloy were carried out with a large strain rate range based on split Hopkinson pressure bar (SHPB) technique, the applied strain rates were 700, 1100, 2150, 2750 and 3650 s-1, respectively. The results show that the flow stress of the studied AM80 magnesium alloy increase with increasing strain rate, demonstrating visible positive strain rate sensitivity. In addition, the flow stress increases significantly when the applied load transfers from quasi-static to dynamic. A Johnson-Cook dynamic constitutive equation is obtained by fitting the experimental stress-strain curves under various strain rates. The SHPB dynamic compressions of the material were simulated by using ABAQUS software with the fitted Johnson-Cook constitutive parameters. Calculated incident, reflected and transmitted waves were correlated with the stress-strain response of the solution treated AM80 samples using two-wave analytical method. The stress-strain curves at different strain rates obtained in the simulations were compared with the experimental and fitting stress-strain responses. The results show that the numerical simulation results and fitting results based on the Johnson-Cook strain-rate dependent constitutive model for the studied Mg alloy are basically in agreement with the experimental results, even the strain rate without in the range for constitutive fitting. Furthermore, an obviously large difference is detected at high strains as compared with that at low strains due to the neglect of local temperature rise under high strain rate loading.
Key words: AM80 magnesium alloy; strain rate sensitivity; Johnson-Cook constitutive equation; numerical simulation
