【作者】 杨慧；

【导师】 张克实； 梁汉吉；

【作者基本信息】 广西大学 ， 工程硕士（建筑与土木工程领域）（专业学位）， 2016， 硕士

【摘要】 材料的断裂准则是对工程材料和结构构件进行强度设计和分析的理论基础。本文通过对T2纯铜材料不同倾角缺口试样的试验和有限元模型分析,针对应力三轴度、罗德参数、等效断裂应变等应力状态参量,研究其在拉伸应力状态下的失效与破坏,并对相应的断裂准则做了探讨。主要内容：(1)通过实心光滑圆棒的单轴拉伸试验,确定材料的弹塑性参数。(2)对一系列不同倾角缺口的平板试样进行了单轴拉伸下的拉剪破坏试验,并观察分析了这些试样的裂纹萌生、扩展情况以及断口形貌特征。(3)结合试验和数值模拟分析,利用ABAQUS有限元模型计算确定相应试样在试验中的起裂点和破坏路径,并探讨了应力状态与破坏的关系。(4)建立了T2纯铜材料基于裂纹萌生时起裂点的应力状态的(0.33-0.67)三轴应力范围内和基于全过程平均应力状态的(0.00-0.57)三轴应力范围内的两种断裂准则,并进行了分析。主要结论：(1)本文主要研究拉伸作用下的拉伸、剪切及其混合型破坏,其中,剪-拉破坏试样起裂点在缺口韧带边缘,拉伸破坏试样起裂点在缺口韧带中心,纯剪破坏试样的起裂点在缺口韧带边缘。(2)在本文拉-剪破坏试验条件下,按全过程平均应力状态为参量的断裂准则可以考虑应力应变历史累积的影响,按裂纹萌生时起裂点的应力状态为参量的破坏准则更便于运用。更多还原

【Abstract】 Failure criterion of material is the theoretical basis of strength analysis and design of engineering materials and components. The author here through the finite element method analyses experiments by using different plate notched specimens of T2 copper, focusing on the influence of stress triaxiality, Lode parameter, equivalent fracture strain and other stress state parameters, performed the investigation of failure and destruction under tensile load. And corresponding fracture criterion was further discussed in the mixed tension-shear failure mode. The main contents are:(1) Calibrate the elastic-plastic parameters of the pure copper through the uniaxial tensile test associated with FEM similation of cylinder-shaped solid bars.(2) A series shear destruction tests under tensile load were carried out by plate notched specimens, in which the notches were designed in different relative angles with relative angles. The crack initiation and propagation and further the fracture morphology of sample were observed and analyzed.(3) Combined experiment results and with numerical simulation analysis, the corresponding initial cracking point and crack growing path of specimen in test were determined by microscopic observation associated with the FEM calculationusing ABAQUS. Further discussion was further done to explore the relationship between stress state and damage.(4) Two failure criteria were established for T2 pure copper materials based on stress triaxiality of the crack initiation starting point (in the range 0.33-0.67) and stress triaxiality average stress state of whole process (in the range 0.00～0.57).The main conclusions are following:(1) The main research of this paper is to study the failures of notched plate specimen under tensile stress,shear stress and mixed stress loads:the crack initiation point of specimen under the tensile stress begins at the center of the notched ligament; the crack initiation point of specimen under the shear stress begins at the edge of the notched ligament, while also at the edge of the notched ligament under the mixed stress loads.(2) Under the experimental conditions of this research, the influence of stress-strain historical accumulation can take consideration on the fracture criterion of using average stress state of whole process stress as parameter. Whereas the crack initiation starting point as parameter is more convenient in practical applications.更多还原