In this paper,the indirect thermal tensile experiments of 7075 aluminum alloy including the pre-deformation process at room temperature and the final heat tensile process were carried out,the plastic deformation behav...In this paper,the indirect thermal tensile experiments of 7075 aluminum alloy including the pre-deformation process at room temperature and the final heat tensile process were carried out,the plastic deformation behavior and forming limit of the material in the compound forming process were investigated considering three pre-deformation amounts 4%,9%,14%,two strain rates 0.001 s^(-1),0.01 s^(-1) and four forming temperatures 300℃,350℃,400℃,450℃.In the indirect hot forming process,the material is sensitive to the pre-deformation,strain rate,and forming temperature,when the strain rate is 0.01 s^(-1),the pre-deformation amount is 4%,and the forming temperature is 400℃,respectively,the maximum tensile deformation is 50 mm.Finally,taking the process in which the forming temperature is 450℃ as an example,according to the observation of the microstructure appearance of fracture,the fracture type in the hot forming process was judged as the ductile fracture.By analyzing the microstructure of the specimen treated with the quenching and artificial aging process,the eutectic T(AlZnMgCu)phase and α(Al)matrix formed a network of non-equilibrium alpha binary eutectic.展开更多
Compressive properties of AZ31 alloy were investigated at temperatures from room temperature to 543 K and at strain rates from 10-3to 2×10 4s-1.The results show that the compressive behavior and deformation mecha...Compressive properties of AZ31 alloy were investigated at temperatures from room temperature to 543 K and at strain rates from 10-3to 2×10 4s-1.The results show that the compressive behavior and deformation mechanism of AZ31 depend largely on the temperature and strain rate.The flow stress increases with the increase of strain rate at fixed temperature,while decreases with the increase of deformation temperature at fixed strain rate.At low temperature and quasi-static condition,the true stress-true strain curve of AZ31 alloy can be divided into three stages(strain hardening,softening and stabilization) after yielding.However,at high temperature and high strain rate,the AZ31 alloy shows ideal elastic-plastic properties.It is therefore suggested that the change in loading conditions(temperature and strain rate) plays an important role in deformation mechanisms of AZ31 alloy.展开更多
A high accuracy experimental system has been established for unsteady open-channel flow.Then 40 experiments were conducted to study the propagating characteristics of unsteady open-channel flow.From the experimental d...A high accuracy experimental system has been established for unsteady open-channel flow.Then 40 experiments were conducted to study the propagating characteristics of unsteady open-channel flow.From the experimental data,the variation law of propagating velocity,wave deformation rate,flow depth of wave peak and bottom,and other parameters were obtained.The experimental results show the followings.1) The propagating velocity of unsteady open-channel flows can be expressed by the sum of flow velocity and micro-amplitude wave velocity at wave peak.2) The waveform of an unsteady flow would deform when it propagates,with the rising stage becoming longer and the falling stage shorter;the deformation rate is a function of distance,period and relative amplitude of discharge.3) The flow depths of wave peak and bottom have a close relationship with the period of the unsteady flow.When the period is short,water depths of wave peak and bottom are both close to those of the average discharge in the condition of uniform flow.For a long period unsteady flow,the water depth of wave peak is close to that of the maximal discharge in the condition of uniform flow,while at the flow wave bottom,it is close to the depth of the minimum discharge in an uniform flow.4) Propagating characteristic of discharge is analogous to that of flow depth for unsteady flow.展开更多
基金Project(SKL2020005)supported by the Open Fund of State Key Laboratory of Advanced Forming Technology and Equipment,ChinaProject(206Z1803G)supported by Local Science and Technology Development Fund Guided by the Central Government of China。
文摘In this paper,the indirect thermal tensile experiments of 7075 aluminum alloy including the pre-deformation process at room temperature and the final heat tensile process were carried out,the plastic deformation behavior and forming limit of the material in the compound forming process were investigated considering three pre-deformation amounts 4%,9%,14%,two strain rates 0.001 s^(-1),0.01 s^(-1) and four forming temperatures 300℃,350℃,400℃,450℃.In the indirect hot forming process,the material is sensitive to the pre-deformation,strain rate,and forming temperature,when the strain rate is 0.01 s^(-1),the pre-deformation amount is 4%,and the forming temperature is 400℃,respectively,the maximum tensile deformation is 50 mm.Finally,taking the process in which the forming temperature is 450℃ as an example,according to the observation of the microstructure appearance of fracture,the fracture type in the hot forming process was judged as the ductile fracture.By analyzing the microstructure of the specimen treated with the quenching and artificial aging process,the eutectic T(AlZnMgCu)phase and α(Al)matrix formed a network of non-equilibrium alpha binary eutectic.
基金Project(10932008)supported by the National Natural Science Foundation of ChinaProject(2008ZF53050)supported by Aviation Science Foundation of China Aviation Industry Corporation I
文摘Compressive properties of AZ31 alloy were investigated at temperatures from room temperature to 543 K and at strain rates from 10-3to 2×10 4s-1.The results show that the compressive behavior and deformation mechanism of AZ31 depend largely on the temperature and strain rate.The flow stress increases with the increase of strain rate at fixed temperature,while decreases with the increase of deformation temperature at fixed strain rate.At low temperature and quasi-static condition,the true stress-true strain curve of AZ31 alloy can be divided into three stages(strain hardening,softening and stabilization) after yielding.However,at high temperature and high strain rate,the AZ31 alloy shows ideal elastic-plastic properties.It is therefore suggested that the change in loading conditions(temperature and strain rate) plays an important role in deformation mechanisms of AZ31 alloy.
基金supported by the National Key Technology R & D Programof China (Grant No. 2011BAB09B01)the Chongqing Natural Science Foundation of China (Grant No. cstc2011jjA1167)
文摘A high accuracy experimental system has been established for unsteady open-channel flow.Then 40 experiments were conducted to study the propagating characteristics of unsteady open-channel flow.From the experimental data,the variation law of propagating velocity,wave deformation rate,flow depth of wave peak and bottom,and other parameters were obtained.The experimental results show the followings.1) The propagating velocity of unsteady open-channel flows can be expressed by the sum of flow velocity and micro-amplitude wave velocity at wave peak.2) The waveform of an unsteady flow would deform when it propagates,with the rising stage becoming longer and the falling stage shorter;the deformation rate is a function of distance,period and relative amplitude of discharge.3) The flow depths of wave peak and bottom have a close relationship with the period of the unsteady flow.When the period is short,water depths of wave peak and bottom are both close to those of the average discharge in the condition of uniform flow.For a long period unsteady flow,the water depth of wave peak is close to that of the maximal discharge in the condition of uniform flow,while at the flow wave bottom,it is close to the depth of the minimum discharge in an uniform flow.4) Propagating characteristic of discharge is analogous to that of flow depth for unsteady flow.
