基于微观损伤模型的Q460C钢材断裂行为研究

发布时间：2018-09-14 10:25

【摘要】：钢结构在强烈地震作用下将会发生超低周疲劳断裂,这类断裂现象通常伴随明显的塑性变形,具有延性断裂的特征。近年来对于金属材料的延性断裂研究已经由传统断裂力学理论逐渐转变为基于微观断裂机理的局部断裂理论,很多学者提出了适用于不同应力状态的局部断裂预测模型,并验证了预测结果的准确性。但是,这些模型主要针对于高应力三轴度的疲劳断裂以及低应力三轴度的拉伸断裂,在低应力三轴度水平下的超低周疲劳断裂范畴还没有进行充分的研究。因此,本文设计了对应高、中、低三种应力三轴度状态的试件,并进行单向拉伸试验和超低周疲劳试验,在前人研究的基础上,提出了适用于全范围应力状态的局部断裂预测模型。本文内容包含以下四个方面:(1)设计了针对高应力三轴度轴对称应力状态的圆棒试件、高应力三轴度平面应变状态的平板试件、以及低应力三轴度剪切应力状态的剪切试件,并设计了单向拉伸以及增幅、等幅、变幅疲劳加载共四种加载制度。(2)完成了 11个单向拉伸试验和25个超低周疲劳试验。根据光滑圆棒试件的试验数据,分别校准了用于模拟单向拉伸试验的材性数据,以及超低周疲劳试验的混合强化模型参数。(3)依据有限元模拟数据,校准了 VGM模型、SWDM模型以及LOU模型的各项系数,编写了 ABAQUS有限元软件的UVARM用户子程序,计算得到各模型的预测结果并进行对比分析。(4)以LOU模型为理论基础建立用于超低周疲劳试验的CLOU延性断裂预测模型,编写UVARM子程序。利用23个不同试件类型以及不同加载制度的疲劳试件校准CLOU模型、CVGM模型以及SWDM模型的系数,验证三种模型的预测结果准确性,分析疲劳试验的损伤积累过程,得到能够应用于全范围应力状态的断裂预测模型,并提供适用于Q460C钢材的三种断裂模型的材料系数。
[Abstract]:Ultra-low cycle fatigue fracture will occur in steel structure under strong earthquake. This kind of fracture is usually accompanied by obvious plastic deformation and has the characteristics of ductile fracture. In recent years, the research on ductile fracture of metallic materials has gradually changed from traditional fracture mechanics theory to local fracture theory based on micro fracture mechanism. Many scholars have proposed a local fracture prediction model suitable for different stress states. The accuracy of the prediction results is verified. However, these models are mainly aimed at the fatigue fracture of high stress triaxiality and the tensile fracture of low stress triaxiality, and the category of ultra-low cycle fatigue fracture at low stress triaxiality level has not been fully studied. Therefore, in this paper, the specimens corresponding to high, middle and low triaxial stress are designed, and the uniaxial tensile tests and ultra-low cycle fatigue tests are carried out. A local fracture prediction model suitable for full range stress state is proposed. The contents of this paper include the following four aspects: (1) the circular bar specimen with high stress triaxiality axisymmetric stress state, the plate specimen with high stress triaxiality plane strain state and the shear specimen with low stress triaxiality shear stress state are designed. Four loading systems were designed for uniaxial tension and fatigue loading with equal amplitude and variable amplitude. (2) 11 uniaxial tensile tests and 25 ultra-low cycle fatigue tests were completed. According to the test data of smooth round bar, the material property data used to simulate uniaxial tensile test and the mixed strengthening model parameters of ultra-low cycle fatigue test were calibrated respectively. (3) according to the finite element simulation data, The coefficients of VGM model and LOU model are calibrated, and the UVARM user subprogram of ABAQUS finite element software is written. The prediction results of each model are calculated and compared. (4) based on the LOU model, the CLOU ductile fracture prediction model for ultra-low cycle fatigue test is established and the UVARM subroutine is compiled. Using 23 fatigue specimens with different specimen types and different loading systems to calibrate the coefficients of the CLOU model and the SWDM model, the accuracy of the prediction results of the three models is verified, and the damage accumulation process of the fatigue test is analyzed. A fracture prediction model which can be applied to the full range stress state is obtained and the material coefficients of three fracture models suitable for Q460C steel are provided.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG142.1

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