韧性金属细观损伤参量的数值模拟研究

发布时间：2018-03-14 12:26

本文选题：细观损伤力学　切入点：Gurson-Tvergaard-Needleman模型　出处：《东北石油大学》2015年硕士论文　论文类型：学位论文

【摘要】：韧性金属是压力容器和承压设备的常用材料,细观损伤机理认为微观孔洞的形核、长大和聚合是金属承载能力下降的主要原因。深入认识韧性金属的细观损伤机理对压力容器和承压设备的安全使用和事故的预防具有重要的现实意义。本文基于细观损伤力学理论,依托黑龙江省自然科学基金《金属构件低周疲劳细观损伤机理及声发射评价方法研究》,以Q245和Q345为例,研究金属在拉伸和低周疲劳条件下的微孔洞细观损伤变量的变化规律,主要内容如下:第一章介绍了课题研究背景、目的及意义,论述了国内外研究和发展现状,介绍了本文的研究路线和研究内容;第二章介绍了几种韧性金属微孔洞损伤模型,并对GTN模型的理论方法、模型参数、细观损伤变量进行了详细的论述;第三章首先应用有限元反向标定法,结合Q245和Q345的拉伸实验和数值模拟,以临界孔洞扩张比VGC为评价标准,选择最适合GTN模型的损伤参数,还分析了微孔洞形核的二相粒子的体积百分数fN、孔洞形核的平均应变εN和标准方差SN对VGC的影响情况。其次模拟了不同材料、不同初始孔洞体积百分数、不同横截面直径缺口试件在拉伸条件下的孔洞体积百分数f、孔洞形核体积百分数fnucleation、孔洞长大体积百分数fgrowth的变化规律,获得了拉伸不同阶段微孔洞的损伤情况,探讨了韧性金属的细观损伤机理;第四章对低周疲劳条件下的不同材料、不同应变幅缺口试件进行微孔洞细观损伤变量模拟,分析微孔洞细观损伤参量演化规律的变化。模拟结果表明,材料特性、初始孔洞体积百分数、横截面直径和应变幅都会对微孔洞细观损伤变量产生影响,故细观损伤变量不是常数。当材料内部存在初始孔洞时,材料内部的微观损伤是由初始孔洞、孔洞形核、孔洞长大共同引起的。
[Abstract]:Ductile metals are common materials used in pressure vessels and pressure equipment. Growth and polymerization are the main reasons for the decrease of metal bearing capacity. It is of great practical significance to understand the meso-damage mechanism of ductile metals for the safe use of pressure vessels and pressure equipment and the prevention of accidents. Meso-damage mechanics theory, Based on the Natural Science Foundation of Heilongjiang Province, "study on the mechanism of microdamage and acoustic emission evaluation of metal components under low cycle fatigue", taking Q245 and Q345 as examples, the variation law of microvoid damage variables of metal under tensile and low cycle fatigue conditions is studied. The main contents are as follows: in the first chapter, the background, purpose and significance of the research are introduced, the research and development situation at home and abroad are discussed, the research route and research contents are introduced, the second chapter introduces several damage models of ductile metal microvoids. The theoretical method, model parameters and mesoscopic damage variables of GTN model are discussed in detail. Chapter three applies the reverse calibration method of finite element method, combined with the tensile experiments and numerical simulation of Q245 and Q345. According to the critical void expansion ratio (VGC) as the evaluation criterion, the damage parameters that are most suitable for the GTN model are selected. The effects of the volume percent of the two-phase particles, the average strain 蔚 N and the standard variance SN of the two-phase particles on the VGC are also analyzed. Secondly, the effects of different materials and different initial pore volume percentages on the VGC are simulated. The variation of void volume percentage f, void nucleation percentage and pore growth volume percentage fgrowth of notched specimens with different cross section diameters under tensile conditions were obtained. The damage of microvoids in different stretching stages was obtained. The meso-damage mechanism of ductile metals is discussed. In Chapter 4th, the microvoid damage variables of different materials and different strain amplitude notched specimens under low cycle fatigue condition are simulated. The results of simulation show that the material characteristics, initial pore volume percentage, cross-section diameter and strain amplitude all have effects on the meso-damage variables of microvoids, and the results of the simulation show that the variation of micropore damage parameters is affected by the variation of micropore damage parameters, such as material characteristics, initial pore volume percentage, cross-section diameter and strain amplitude. The microscopic damage of the material is caused by the initial hole, the nucleation of the pore, and the growth of the pore when there is an initial hole in the material.
【学位授予单位】：东北石油大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG115.5;TG113

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