材料重复冲击损伤模型与数值计算方法研究

基于连续介质损伤力学，将有效应力概念和应变等效假设应用于Johnson-Cook本构模型中，建立了重复冲击载荷作用下材料力学性能退化的损伤模型，以及考虑材料性能退化对冲击应力应变响应影响的数值计算方法。首先，推导了基于损伤耦合J-C本构模型的应力应变数值计算关系式，并在ABAQUS中进行二次开发，采用两种方法实现了考虑损伤影响的应力应变数值计算。进一步，建立了试件在重复冲击下损伤累积的计算方法，并采用所建方法对含缺口三点弯试件的重复冲击损伤进行了数值计算，研究了缺口根部应力应变及损伤度，并对试件整体损伤规律进行了分析。进一步开展了缺口三点弯试件的重复冲击试验，通过计算结果与试验结果的对比验证了建立的数值计算方法的可行性和适用性。与无损伤耦合模型计算结果相比，损伤耦合模型更能合理反映出缺口根部材料的力学性能退化过程以及损伤累积与冲击响应之间的相互影响。

Study on Material Damage Accumulation Model and Its Numerical Implementation under Repeated Impact Loading

Based on Continuum damage mechanics, the concept of effective stress and the hypothesis of strain equivalence are introduced into Johnson-Cook constitutive model, and a damage model with considering the degradation of mechanical properties of material and its influence on the stress and strain field under repeated impact loading is built. Stress-strain relationship of material with damage is derived according to the damage-coupled J-C model, and is numerically implemented in commercial FEM software ABAQUS by two approaches. A numerical method for the calculation of repeated impact damage is built, and is then applied to compute the accumulative damage of a notched three-point bending specimen under repeated impact loading. Stress, strain and damage at the notch root are investigated. The damage fields of the specimen are studied as well. The variation of the strain near the notch root along with the number of impact coincides with the experimental result of a reference. A repeated impact test of the notched three-point bending specimen is implemented, and the comparison between the computed result with the experimental data validates the feasibility and applicability of the proposed method. Via the comparison with the results obtained by the model without damage coupling, the damage-coupled model can more reasonably reflect the degradation process of mechanical property of materials at the notch tip and the interaction between damage accumulation and impact response.