The characteristics of hot deformation of an α＋β titanium alloy Ti-6.5Al-3.5Mo-1.5Zr-0.3Si with acicular microstructure were studied using isothermal hot compressive tests in a strain rate range of 0.01-10 s^-1 at ...The characteristics of hot deformation of an α＋β titanium alloy Ti-6.5Al-3.5Mo-1.5Zr-0.3Si with acicular microstructure were studied using isothermal hot compressive tests in a strain rate range of 0.01-10 s^-1 at 860-1 100 ℃. The true stress-tree strain curves of alloy hot-compressed in the α＋β region exhibit a peak stress followed by continuous flow softening; whereas in the β region, the flow stress attains a steady-state regime. At a strain rate of 10 s^-1 and in a wide temperature range, the alloy exhibits plastic flow instability. According to the kinetic rate equation, the apparent activation energies are estimated to be about 633 kJ/mol in the α＋β region and 281 kJ/mol in the β region, respectively. The processing maps show a domain of the globularization process of a colony structure and α dynamic recrystallization in the temperature range of 860-960 ℃ with a peak efficiency of about 60%, and a domain of β dynamic recrystallization in the β region with a peak efficiency of 80%.展开更多
A parameter, known as the parameter of humidification vibration deformation, was proposed, describing quantitatively the impact of water content on vibration settlement deformation, and its relationship with humidific...A parameter, known as the parameter of humidification vibration deformation, was proposed, describing quantitatively the impact of water content on vibration settlement deformation, and its relationship with humidification water content, dynamic shear stress peak value, initial consolidation stress and vibration frequency was built. The result shows that 1） the parameter of humidification vibration deformation increases with the vibration shear stress peak value increasing. 2） The humidification water content has significant influence on the curve of the parameter of humidification vibration deformation and the peak vibration shear stress. When the humidification water content is low, the curve increases slowly. However, when the humidification water content is high, the curve increases rapidly. 3） Initial consolidation stress has significant influence on the humidification vibration deformation coefficient. When initial consolidation stress is not large enough to destroy the loess structure, with initial consolidation stress increasing, the humidification vibration deformation coefficient decreases. On the contrary, the humidification vibration deformation coefficient increases with initial consolidation stress increasing. 4） With the increase of vibration time, the parameter of humidification vibration settlement shows an increasing trend overall. The initial dynamic shear stress peak value and humidification water content all have significant effects on the curve of the parameter of humidification vibration settlement and vibration time. However, the humidification water content is even more significant.展开更多
Effects of strain rate and water-to-cement ratio on the dynamic compressive mechanical behavior of cement mortar are investigated by split Hopkinson pressure bar(SHPB) tests. 124 specimens are subjected to dynamic uni...Effects of strain rate and water-to-cement ratio on the dynamic compressive mechanical behavior of cement mortar are investigated by split Hopkinson pressure bar(SHPB) tests. 124 specimens are subjected to dynamic uniaxial compressive loadings.Strain rate sensitivity of the materials is measured in terms of failure modes, stress-strain curves, compressive strength, dynamic increase factor(DIF) and critical strain at peak stress. A significant change in the stress-strain response of the materials with each order of magnitude increase in strain rate is clearly seen from test results. The slope of the stress-strain curve after peak value for low water-to-cement ratio is steeper than that of high water-to-cement ratio mortar. The compressive strength increases with increasing strain rate. With increase in strain rate, the dynamic increase factor(DIF) increases. However, this increase in DIF with increase in strain rate does not appear to be a function of the water-to-cement ratio. The critical compressive strain increases with the strain rate.展开更多
基金Project(50901063) supported by the National Natural Science Foundation of ChinaProject(2007DS0414, 2007BS05006) supported by the Science and Technology Program of Shangdong Province, ChinaProject supported by the Open Research Fund from State Key Laboratory of Rolling and Automation, Northeastern University, China
文摘The characteristics of hot deformation of an α＋β titanium alloy Ti-6.5Al-3.5Mo-1.5Zr-0.3Si with acicular microstructure were studied using isothermal hot compressive tests in a strain rate range of 0.01-10 s^-1 at 860-1 100 ℃. The true stress-tree strain curves of alloy hot-compressed in the α＋β region exhibit a peak stress followed by continuous flow softening; whereas in the β region, the flow stress attains a steady-state regime. At a strain rate of 10 s^-1 and in a wide temperature range, the alloy exhibits plastic flow instability. According to the kinetic rate equation, the apparent activation energies are estimated to be about 633 kJ/mol in the α＋β region and 281 kJ/mol in the β region, respectively. The processing maps show a domain of the globularization process of a colony structure and α dynamic recrystallization in the temperature range of 860-960 ℃ with a peak efficiency of about 60%, and a domain of β dynamic recrystallization in the β region with a peak efficiency of 80%.
基金Foundation item： Project（51178392） supported by the National Natural Science Foundation of China
文摘A parameter, known as the parameter of humidification vibration deformation, was proposed, describing quantitatively the impact of water content on vibration settlement deformation, and its relationship with humidification water content, dynamic shear stress peak value, initial consolidation stress and vibration frequency was built. The result shows that 1） the parameter of humidification vibration deformation increases with the vibration shear stress peak value increasing. 2） The humidification water content has significant influence on the curve of the parameter of humidification vibration deformation and the peak vibration shear stress. When the humidification water content is low, the curve increases slowly. However, when the humidification water content is high, the curve increases rapidly. 3） Initial consolidation stress has significant influence on the humidification vibration deformation coefficient. When initial consolidation stress is not large enough to destroy the loess structure, with initial consolidation stress increasing, the humidification vibration deformation coefficient decreases. On the contrary, the humidification vibration deformation coefficient increases with initial consolidation stress increasing. 4） With the increase of vibration time, the parameter of humidification vibration settlement shows an increasing trend overall. The initial dynamic shear stress peak value and humidification water content all have significant effects on the curve of the parameter of humidification vibration settlement and vibration time. However, the humidification water content is even more significant.
基金Project(51479048) supported by National Natural Science Foundation of China
文摘Effects of strain rate and water-to-cement ratio on the dynamic compressive mechanical behavior of cement mortar are investigated by split Hopkinson pressure bar(SHPB) tests. 124 specimens are subjected to dynamic uniaxial compressive loadings.Strain rate sensitivity of the materials is measured in terms of failure modes, stress-strain curves, compressive strength, dynamic increase factor(DIF) and critical strain at peak stress. A significant change in the stress-strain response of the materials with each order of magnitude increase in strain rate is clearly seen from test results. The slope of the stress-strain curve after peak value for low water-to-cement ratio is steeper than that of high water-to-cement ratio mortar. The compressive strength increases with increasing strain rate. With increase in strain rate, the dynamic increase factor(DIF) increases. However, this increase in DIF with increase in strain rate does not appear to be a function of the water-to-cement ratio. The critical compressive strain increases with the strain rate.
