考虑微观GTN损伤模型的建筑钢材力学性能研究

发布时间：2018-12-10 17:40

【摘要】：钢结构构件的韧性破坏是其主要破坏形式,而考虑微观损伤的本构模型能够从微观层面形象的解释延性金属材料的韧性破坏,科学、合理地揭示钢材非线性性能的真实发展过程。目前应用最为广泛的微观损伤模型是GTN(Gurson-Tvergaard-Needleman)模型,然而,该模型尚未推广于建筑领域中。因此,本文将微观GTN损伤模型引入建筑钢材力学性能研究中。基于微观GTN损伤本构理论,调制了有限元软件ABAQUS中的用户材料子程序UMAT,通过单元算例,验证了程序有效性和正确性,并系统分析了损伤参数对预测结果的影响。取材自Q345低合金钢和奥氏体304不锈钢热轧无缝钢管,加工光滑和缺口试件,进行了标准和缺口试件单向拉伸破坏试验,分别识别了两种钢材的材料参数和损伤参数,并与数值模拟结果进行对比,发现GTN损伤模型能够准确预测Q345低合金钢试件的断裂点,而采用Ramberg-Osgood曲线模拟钢材应力应变关系构筑GTN损伤模型,无法准确模拟奥氏体304不锈钢的力学行为。对Q345低合金钢和奥氏体304不锈钢光滑和缺口试件进行低周往复加载试验,得到其滞回和骨架曲线,结果表明钢材在单调与循环荷载下的力学性能有很大的区别。此外,通过电镜扫描试验,观察两种钢材试件在单调和循环荷载下的断口微观形态,探讨Q345低合金钢和奥氏体304不锈钢断口微观形态的区别,以及同一钢材在不同加载方式下的破坏特征,论证其是否与GTN本构模型的微观表述符合,为后续研究奠定基础。
[Abstract]:The ductile failure of steel structural members is the main failure form, and the constitutive model considering microscopic damage can explain the ductile damage of ductile metal materials vividly from the microscopic level. It is reasonable to reveal the true development process of the nonlinear properties of steel. The most widely used microscopic damage model is GTN (Gurson-Tvergaard-Needleman) model. However, the model has not been extended to the field of architecture. Therefore, the microscopic GTN damage model is introduced into the study of mechanical properties of building steel. Based on the microscopic GTN damage constitutive theory, the user material subroutine UMAT, in the finite element software ABAQUS is modulated. The validity and correctness of the program are verified by a numerical example, and the influence of damage parameters on the prediction results is systematically analyzed. After hot rolled seamless steel tubes made from Q345 low alloy steel and austenitic 304 stainless steel, smooth and notched specimens were processed. Uniaxial tensile failure tests of standard and notched specimens were carried out. The material parameters and damage parameters of two kinds of steels were identified, respectively. Compared with the numerical simulation results, it is found that the GTN damage model can accurately predict the fracture point of Q345 low alloy steel specimen, while the Ramberg-Osgood curve is used to simulate the stress-strain relationship of steel to construct the GTN damage model. The mechanical behavior of austenitic 304 stainless steel cannot be accurately simulated. The hysteresis and skeleton curves of Q345 low alloy steel and austenitic 304 stainless steel smooth and notched specimens under low cycle reciprocating loading are obtained. The results show that the mechanical properties of steel under monotonic and cyclic loads are quite different. In addition, the fracture morphology of two kinds of steel specimens under monotonic and cyclic loading was observed by scanning electron microscope test, and the difference between the fracture morphology of Q345 low alloy steel and austenitic 304 stainless steel was discussed. The failure characteristics of the same steel under different loading modes are proved to be consistent with the microscopic expression of the GTN constitutive model, which lays a foundation for further research.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU511.3

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