高速沖擊載荷下AM80鎂合金的力學本構及仿真模擬

高速沖擊載荷下AM80鎂合金的力學本構及仿真模擬Mechanical constitutive equation and simulation of AM80 magnesium alloy under high speed impact load

采用霍普金森壓桿技術對固溶態(tài)AM80鎂合金進行大應變率范圍下的高速沖擊實驗，應變速率分別為700、1100、2150、2750和3650 s-1。結果表明：實驗用AM80鎂合金的流變應力隨應變速率的增加而增加，表現(xiàn)出明顯的正應變率敏感性；當載荷由準靜態(tài)轉(zhuǎn)為動態(tài)時，合金的流變應力顯著增加?；诓煌瑧兟氏碌膽Α獞兦€確定實驗用鎂合金的Johnson-Cook(J-C)本構方程。采用ABAQUS有限元軟件對合金的SHPB實驗進行了數(shù)值模擬，根據(jù)模擬得到的入射波、反射波和透射波形計算得到各應變速率下的應力—應變曲線，并與實驗及J-C本構擬合的應力—應變響應進行對比。結果表明：即使在本構擬合所選應變速率范圍外，仿真分析結果也與實驗及本構擬合結果基本吻合；但在較高應變時，由于本構未考慮溫升效應，使得擬合結果與實驗結果的差異較低應變時明顯要大。

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.

全文下載：http://pan.baidu.com/s/1hskTxJ2