WE43合金在不同应力状态下的本构关系及断裂行为表征

研究WE43合金在不同应力状态下的塑性和断裂行为。设计拉伸、压缩及剪切试样,并进行力学实验。采用数字图像相关技术对测试过程进行记录和处理。实验结果表明:WE43合金具有低的拉压非对称性,其断裂机制属于韧性断裂。基于Drucker屈服函数,采用不同的硬化规律模拟单轴拉伸和压缩下的塑性变形行为。通过数值模拟得到应力状态和断裂应变。采用Brozzo、Oh、Ko-Huh和DF2016准则对韧性断裂行为进行数值预测,并与实验结果进行对比。结果表明:采用Swift-Voce硬化定律和Drucker屈服函数能合理模拟塑性变形。DF2016断裂准则能准确预测合金在各种应力状态下的断裂行为。

先进高强钢DP780板料的温成形极限预测研究

为准确预测DP780钢板料在温成形条件下的成形极限曲线,将韧性断裂预测模型引入到数值模拟。基于DP780钢板料在温度范围573 K~873 K、应变率范围6.67×10^(-4)s^(-1)~6.67×10^(-3)s^(-1)的单向拉伸试验结果分析,利用强塑积指标确定了温度为673 K、应变率为3.33×10^(-3)s^(-1)条件下材料的温冲压成形性能较好。通过该变形条件下的简单拉伸试验和数值模拟,确定了影响DP780钢板料韧性断裂的主要因素。建立了可以预测DP780钢板料在不同应变路径下发生拉伸型断裂和剪切型断裂两种断裂机制的韧性断裂预测模型,并与温成形本构模型、Hill’48屈服准则相结合实现了刚模胀形试验的数值模拟,预测了DP780钢板料在温度为673 K下的成形极限曲线,并建立了成形极限数学模型。结果表明,利用该方法预测的成形极限结果拥有较好的精度。

Fracture prediction in non-isothermal viscous pressure bulging of aluminum alloy sheet using ductile fracture criterion

The failure of AA3003 aluminum alloy sheet metal was predicted for non-isothermal viscous pressure bulging (VPB). Utilizing the coupled thermo-mechanical finite element method combined with ductile fracture criterion, the calculations were carried out for non-isotherm VPB at various temperatures and the influences of the initial temperature of viscous medium on failure mode of bulge specimens were investigated. The results show that the failure modes are different for the non-isothermal VPB with different initial temperatures of viscous medium. For the non-isothermal VPB of AA3003 aluminum alloy sheet with initial temperature of 250 ℃, when the initial temperature of viscous medium ranges from 150 to 180 ℃, the formability of sheet metal can be improved to a full extent. The validity of the predictions is examined by comparing with experimental results.