一种韧性断裂模型的理论研究和实验验证

发布时间：2018-10-30 17:06

【摘要】：为研究高强钢板成形过程中的损伤破裂机理,更准确地预测高强钢的断裂失效行为,基于细观损伤力学的空穴理论,并在屈服函数就是塑性势函数的通用性假设基础上推导了各向同性的韧性断裂模型;同时引入Lode参数以反映不同应变状态下空穴形核、长大以及聚合的差异,提出了一种包含应力三轴度和Lode参数的新模型.在Hill正交各向异性屈服假设下,描述了平面应力状态下应力比值、r值与应力三轴度、等效塑性应变的关系.最后,针对DP590进行了参数确定和实验验证.结果表明:应力三轴度在高强钢韧性断裂中仍然起主导因素,在低应力三轴下,材料主要是剪切型破坏,空穴的长大及聚合方式主要受剪应力影响,高应力三轴下,空穴损伤主要受拉应力影响,断裂是韧窝形的;Lode参数决定了应力组成形式,也间接地反映了应变状态,它与应力三轴度共同决定了空穴损伤的发展.新的模型能较准确地预测DP590的成形极限.
[Abstract]:In order to study the damage and fracture mechanism of high strength steel sheet during forming and predict the fracture failure behavior of high strength steel more accurately, the hole theory of mesoscopic damage mechanics is used to predict the failure behavior of high strength steel. An isotropic ductile fracture model is derived on the basis of the assumption that the yield function is the plastic potential function. At the same time, Lode parameters are introduced to reflect the difference of cavity nucleation, growth and polymerization under different strain states. A new model including stress triaxiality and Lode parameters is proposed. Under the Hill orthotropic yield hypothesis, the relationship between stress ratio, r value and stress triaxiality, equivalent plastic strain under plane stress state is described. Finally, the parameters of DP590 are determined and verified by experiments. The results show that the stress triaxiality still plays a leading role in the ductile fracture of high strength steel. Under the low stress triaxial, the material is mainly shear failure, the hole growth and polymerization mode are mainly affected by the shear stress, and the high stress triaxial is the main factor. The hole damage is mainly affected by tensile stress and the fracture is dimple. The Lode parameter determines the form of stress composition and indirectly reflects the strain state, which, together with the stress triaxiality, determines the development of hole damage. The new model can accurately predict the forming limit of DP590.
【作者单位】：北京航空航天大学机械工程及自动化学院;汽车用钢开发与应用技术国家重点实验室(宝钢集团);
【基金】：国家自然科学基金资助项目(51275026) 宝钢重点实验室开放基金(Y12ECEQ07Y)
【分类号】：TG142.1

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