Finite Element Simulation Study Of Meso Damage Parameter Of Ductile Metal

Ductile metal are commonly used in pressure vessels and pressure equipment, micro-damage mechanism considers that micro-void nucleation, growth and coalescence are the main reason leading to the decline of metal bearing capacity. Understanding the micro-damage mechanism of ductile metal has important significance on the pressure vessels and pressure equipment safety using and accident prevention. This paper based on the theory of damage mechanics, combined with the Natural Science Foundation of Heilongjiang Province "Metal components of micro-damage mechanism of low cycle fatigue and acoustic emission evaluation method research", using Q245 and Q345 as an example, study the change of micro-damage variables in tension and low-fatigue, the main contents are as follows:The first chapter introduces the research background, propose and significance, discusses the current situation of research and development in China and abroad, introduces the research route and research content. The second chapter introduces several ductile metal void damage models, and discusses the theory and method, parameters and micro-damage variables of GTN model in detail. The third chapter first applies finite element inverse calibration method, and contrasts the critical void expansion ratio VGC of simulation and experience results to choose the most suitable damage parameters of GTN model. This paper also study the effect of the volume fraction of second phase particle of micro-void nucleation fN, the void nucleation average strain εN and standard deviation SN on the VGC. Then simulate different materials, different initial void volume fraction and different diameter of notched specimens under tensile conditions. The change of void volume fraction f, void nucleation volume fraction fnucleation and void growth volume fraction fgrowth are used to obtain the different stages of micro-voids under tensile conditions. The forth chapter simulate different materials and different strain amplitude notched specimens of void damage under low cycle fatigue condition and analysis the change of micro-damage parameters. The micro-damage mechanism of ductile metal is discussed.The simulation results show that the material properties, initial void volume fraction, cross-sectional diameter and strain amplitude all have impact on micro-damage variables of micro-void, so the micro-damage variables are not constant. When the initial void exists inside the material, the micro-damage inside the material is caused by the initial void, void nucleation and void grow up.