The uniaxial tensile tests were carried out at temperature ranging from room temperature(RT)to 523 K under strain rates of 0.001,0.010 and 0.100 s^(-1) to obtain the flow stress of AZ31 B magnesium alloy.The tensile t...The uniaxial tensile tests were carried out at temperature ranging from room temperature(RT)to 523 K under strain rates of 0.001,0.010 and 0.100 s^(-1) to obtain the flow stress of AZ31 B magnesium alloy.The tensile tests were simulated by the finite element method(FEM)to calculate the critical damage values(Dc)of the CockcroftLatham criterion to predict the occurrence of fracture defects.Finally,the effects of temperature and strain rate on Dc were analyzed to predict the critical damage value’s evolution.The results demonstrate that the critical damage value changes in the range of 0.188-0.718.It increases as strain rate decreases at constant temperature,and increases with the increase of temperature under certain strain rate,but is more sensitive to the temperature.展开更多
Based on a damage evolution equation and a critical damage function model, this paper has completed the numerical simulation of ductile spall fracture. The free-surface velocity and damage distribution have been used ...Based on a damage evolution equation and a critical damage function model, this paper has completed the numerical simulation of ductile spall fracture. The free-surface velocity and damage distribution have been used to determine jointly the physical parameters D1 (the critical linking damage), Df (the critical fracturing damage) and k (the softening rate of critical damage function model) of the critical damage function model, which are 0.11, 0.51 and 0.57 respectively. Results indicate that the parameters determined by any of shots could be applicable to the rest of other shots, which is convincing proof for the universal property of critical damage function. In our experiments, the shock pressure is about 1 GPa to 2.5 CPa. For the reason of limited pressure range, there are still some limitations in the methods of present analysis. Moreover, according to the damage evolution characteristic of pure aluminum obtained by experiments, two critical damages are obtained, which are 0.11 and 0.51 respectively. The results are coincident with the experimental ones, which indicate that the critical growth behaviour of damage occurs in the plastic metal under dynamic loading.展开更多
According to the principle of damage mechanics,the damage characteristics of ferrite nodular cast iron under uniaxial stress were studied by measuring electric resistance. The results show that the damage in nodular c...According to the principle of damage mechanics,the damage characteristics of ferrite nodular cast iron under uniaxial stress were studied by measuring electric resistance. The results show that the damage in nodular cast iron occurs when the applied stress is more than a certain extent,and the damage variable increases with stress. The evolutional law of damage variable as a function of stress was obtained.The damage threshold of nodular cast iron increases with nodularity,but it is below the yield strength,which provides reference significance to the design of machinery structure and the choice of materials.The critical damage variable is not related to the nodularity,which is about 0. 060-0. 068.展开更多
According to the principle of damage mechanics, the damage characteristics of ferrite nodular cast iron under uniaxial stress were studied by measuring electric resistance. The results show that the damage in nodular ...According to the principle of damage mechanics, the damage characteristics of ferrite nodular cast iron under uniaxial stress were studied by measuring electric resistance. The results show that the damage in nodular cast iron occurs when the applied stress is more than a certain extent, and the damage variable increases with stress. The evolutional law of damage variable as a function of stress was obtained. The damage threshold of nodular cast iron increases with nodularity, but it is below the yield strength, which provides reference significance to the design of machinery structure and the choice of materials. The critical damage variable is not related to the nodularity, which is about 0 060-0 068.展开更多
基金financially supported by the National Great Theoretic Research Project(No.2013CB632200)the National Science&Technology Support Project(No.2011BAE 22B01-3)+1 种基金the International Cooperation Project(No.2010DFR 50010)the Sharing Fund of Chongqing University’s Large-Scale Equipment。
文摘The uniaxial tensile tests were carried out at temperature ranging from room temperature(RT)to 523 K under strain rates of 0.001,0.010 and 0.100 s^(-1) to obtain the flow stress of AZ31 B magnesium alloy.The tensile tests were simulated by the finite element method(FEM)to calculate the critical damage values(Dc)of the CockcroftLatham criterion to predict the occurrence of fracture defects.Finally,the effects of temperature and strain rate on Dc were analyzed to predict the critical damage value’s evolution.The results demonstrate that the critical damage value changes in the range of 0.188-0.718.It increases as strain rate decreases at constant temperature,and increases with the increase of temperature under certain strain rate,but is more sensitive to the temperature.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10876014)the Science and Technology Foundation of State Key Laboratory of Shock Wave and Detonation Physics (Grant No. 9140C6701010701)
文摘Based on a damage evolution equation and a critical damage function model, this paper has completed the numerical simulation of ductile spall fracture. The free-surface velocity and damage distribution have been used to determine jointly the physical parameters D1 (the critical linking damage), Df (the critical fracturing damage) and k (the softening rate of critical damage function model) of the critical damage function model, which are 0.11, 0.51 and 0.57 respectively. Results indicate that the parameters determined by any of shots could be applicable to the rest of other shots, which is convincing proof for the universal property of critical damage function. In our experiments, the shock pressure is about 1 GPa to 2.5 CPa. For the reason of limited pressure range, there are still some limitations in the methods of present analysis. Moreover, according to the damage evolution characteristic of pure aluminum obtained by experiments, two critical damages are obtained, which are 0.11 and 0.51 respectively. The results are coincident with the experimental ones, which indicate that the critical growth behaviour of damage occurs in the plastic metal under dynamic loading.
基金the Education Committee of Hebei for the financial support ( B2003102 )
文摘According to the principle of damage mechanics,the damage characteristics of ferrite nodular cast iron under uniaxial stress were studied by measuring electric resistance. The results show that the damage in nodular cast iron occurs when the applied stress is more than a certain extent,and the damage variable increases with stress. The evolutional law of damage variable as a function of stress was obtained.The damage threshold of nodular cast iron increases with nodularity,but it is below the yield strength,which provides reference significance to the design of machinery structure and the choice of materials.The critical damage variable is not related to the nodularity,which is about 0. 060-0. 068.
基金Item Sponsored by Scientific and Technological Brainstorm Project for Ninth Five-Year Plan of China(97-225-02-02-11)
文摘According to the principle of damage mechanics, the damage characteristics of ferrite nodular cast iron under uniaxial stress were studied by measuring electric resistance. The results show that the damage in nodular cast iron occurs when the applied stress is more than a certain extent, and the damage variable increases with stress. The evolutional law of damage variable as a function of stress was obtained. The damage threshold of nodular cast iron increases with nodularity, but it is below the yield strength, which provides reference significance to the design of machinery structure and the choice of materials. The critical damage variable is not related to the nodularity, which is about 0 060-0 068.