To study the damage and fracture mechanism of 6063 aluminum alloy under different stress states,three kinds of representative triaxial stress states have been adopted,namely smooth tensile,notch tensile,and pure shear...To study the damage and fracture mechanism of 6063 aluminum alloy under different stress states,three kinds of representative triaxial stress states have been adopted,namely smooth tensile,notch tensile,and pure shear.The results of the study indicate the following.During the notch tensile test,a relatively higher stress triaxiality appears in the root of the notch.With the applied loading increasing,the volume fraction of microvoids in the root of the notch increases continuously.When it reaches the critical volume fraction of microvoids,the specimen fractures.During the pure shear test,the stress triaxiality almost equals to zero,and there is almost no microvoids but a shear band at the center of the butterfly specimen.The shear band results from nonuniform deformation constantly under the shear stress.With stress concentration,cracks are produced within the shear band and are later coalesced.When the equivalent plastic strain reaches the critical value（equivalent plastic fracture strain）,the butterfly specimen fractures.During the smooth tensile test,the stress triaxiality in the gauge of the specimen remains constant at 0.33.Thus,the volume of microvoids of the smooth tensile test is less than that of the notch tensile test and the smooth specimen fractures due to shearing between microvoids.The G-T-N damage model and Johnson-Cook model are used to simulate the notch tensile and shear test,respectively.The simulated engineering stress-strain curves fit the measured engineering stress-strain curves very well.In addition,the empirical damage evolution equation for the notch specimen is obtained from the experimental data and FEM simulations.展开更多
The deformation and damage mechanism of aluminum alloy (6063) were investigated by 0°, 30°, 45°, 60°and 90°tensile tests and tensile-unload tests with the modified Arcan fixture on the butterf...The deformation and damage mechanism of aluminum alloy (6063) were investigated by 0°, 30°, 45°, 60°and 90°tensile tests and tensile-unload tests with the modified Arcan fixture on the butterfly specimens. The results show: the curves of engineering stress-engineering strain under different stress states are obviously different. There were microvoids in the specimen when 0°direction loading was preformed. The microcracks were produced in the root of notch as the result of the microvoids shearing fracture and then they led to specimen fracture with microcracks being coalesced. With tensile angle increasing, the shear stress in the center of butterfly specimen increases gradually, while the deformation bands become more and more concentrative. In these concentrative deformation bands, the microcracks are produced and then microcracks propagation and coalescence result in specimen fracture. When 90°direction loading is preformed, the shear bands are obviously formed. The G-T-N damage model and the Johnson-cook model were used to simulate 0°tensile test and 90°tensile test respectively. The simulated engineering stress-engineering strain curves fit the measured ones very well.展开更多
From RTT relations the integrable Hamiltonian of the trigonometric Goryachev\|Chaplygin gyrostat is established, which can be reduced to the Hamiltonian of t\|j model by using multi\|fermion realization of \%SU\-q(2)\...From RTT relations the integrable Hamiltonian of the trigonometric Goryachev\|Chaplygin gyrostat is established, which can be reduced to the Hamiltonian of t\|j model by using multi\|fermion realization of \%SU\-q(2)\% algebra and average\|field approximation.展开更多
文摘To study the damage and fracture mechanism of 6063 aluminum alloy under different stress states,three kinds of representative triaxial stress states have been adopted,namely smooth tensile,notch tensile,and pure shear.The results of the study indicate the following.During the notch tensile test,a relatively higher stress triaxiality appears in the root of the notch.With the applied loading increasing,the volume fraction of microvoids in the root of the notch increases continuously.When it reaches the critical volume fraction of microvoids,the specimen fractures.During the pure shear test,the stress triaxiality almost equals to zero,and there is almost no microvoids but a shear band at the center of the butterfly specimen.The shear band results from nonuniform deformation constantly under the shear stress.With stress concentration,cracks are produced within the shear band and are later coalesced.When the equivalent plastic strain reaches the critical value（equivalent plastic fracture strain）,the butterfly specimen fractures.During the smooth tensile test,the stress triaxiality in the gauge of the specimen remains constant at 0.33.Thus,the volume of microvoids of the smooth tensile test is less than that of the notch tensile test and the smooth specimen fractures due to shearing between microvoids.The G-T-N damage model and Johnson-Cook model are used to simulate the notch tensile and shear test,respectively.The simulated engineering stress-strain curves fit the measured engineering stress-strain curves very well.In addition,the empirical damage evolution equation for the notch specimen is obtained from the experimental data and FEM simulations.
基金Project (2004CCA04900) supported by Ministry of Science and Technology of China
文摘The deformation and damage mechanism of aluminum alloy (6063) were investigated by 0°, 30°, 45°, 60°and 90°tensile tests and tensile-unload tests with the modified Arcan fixture on the butterfly specimens. The results show: the curves of engineering stress-engineering strain under different stress states are obviously different. There were microvoids in the specimen when 0°direction loading was preformed. The microcracks were produced in the root of notch as the result of the microvoids shearing fracture and then they led to specimen fracture with microcracks being coalesced. With tensile angle increasing, the shear stress in the center of butterfly specimen increases gradually, while the deformation bands become more and more concentrative. In these concentrative deformation bands, the microcracks are produced and then microcracks propagation and coalescence result in specimen fracture. When 90°direction loading is preformed, the shear bands are obviously formed. The G-T-N damage model and the Johnson-cook model were used to simulate 0°tensile test and 90°tensile test respectively. The simulated engineering stress-engineering strain curves fit the measured ones very well.
文摘From RTT relations the integrable Hamiltonian of the trigonometric Goryachev\|Chaplygin gyrostat is established, which can be reduced to the Hamiltonian of t\|j model by using multi\|fermion realization of \%SU\-q(2)\% algebra and average\|field approximation.
