The hot deformation behaviors and microstructures of A1-Zn-Mg-Cu-Cr aluminum alloy have been studied using thermal simulation test, optical microscopy and transmission electron microscopy. As a result, the true stress...The hot deformation behaviors and microstructures of A1-Zn-Mg-Cu-Cr aluminum alloy have been studied using thermal simulation test, optical microscopy and transmission electron microscopy. As a result, the true stress versus true strain curves and the microstructures under various deformation conditions are obtained. The microstructures gradually incline to dynamic-recrystallization with the deformation temperature rising and the recrystallization grains refine with the decrease of deformation temperature or with raising the strain rates. The quantitative relationship between the Zener-Hollomon parameter （Z） and average recrystallization grain size in the subsequent heat treatment is set up.展开更多
以重塑泥炭质土为研究对象,利用全球数字系统(global digital systems,GDS)动三轴仪对土体进行循环加载试验,分析一系列围压、固结比(Kc)、频率下土体滞回曲线演化规律,采用滞回曲线长轴斜率(k)、中心偏移量(d)、动应变幅值(εm)和包围...以重塑泥炭质土为研究对象,利用全球数字系统(global digital systems,GDS)动三轴仪对土体进行循环加载试验,分析一系列围压、固结比(Kc)、频率下土体滞回曲线演化规律,采用滞回曲线长轴斜率(k)、中心偏移量(d)、动应变幅值(εm)和包围的面积(S)对洱海高原湖相泥炭质土滞回曲线形态特征进行定量描述。试验结果表明:泥炭质土滞回曲线较为封闭,整体呈长梭形,在相同动应力幅值下,εm随围压、固结比、频率增大而减小,且减小速度逐渐降低;k随动应力幅值(σm)增大呈对数关系衰减,随围压、固结比、频率增大而增大,加载前期对频率变化表现不敏感;d和S随σm增大呈两阶段增大,加载前期增大平缓,后以指数关系快速增大;d和S随围压和频率增大而减小,且对频率变化表现更敏感;非等压固结(Kc≠1.0)条件下的d比等压固结(Kc=1.0)条件下更大,且S即土体完成一个荷载循环消耗能量更小。展开更多
Using self-researched gas drainage borehole stability dynamic monitoring device, three-dimensional deformation characteristics of borehole under steady vertical load were researched experimentally and systematically. ...Using self-researched gas drainage borehole stability dynamic monitoring device, three-dimensional deformation characteristics of borehole under steady vertical load were researched experimentally and systematically. This research indicated that under the action of steady loading, the mechanical deformation path of the simulated gas drainage borehole is gradually complicated, and the decay of the borehole circumferential strain is an important characterization of the prediction and early warning of borehole instability and collapse. The horizontal position of borehole occurs compressive strain, and the vertical of which occurs tensile strain under the action of vertical stress. At the initial stage of loading, the vertical strain is more sensitive than that in the horizontal direction. After a certain period of time, the horizontal strain is gradually higher than the vertical one, and the intersection of the borehole horizontal diameter and the hole wall is the stress concentration point. With the increase of the depth of hole, the strain shows a gradual decay trend as a whole, and the vertical strain decays more observably, but there is no absolute position correlation between the amount of strain decay and the increase in borehole depth,and the area within 1.5 times the orifice size is the borehole stress concentration zone.展开更多
文摘The hot deformation behaviors and microstructures of A1-Zn-Mg-Cu-Cr aluminum alloy have been studied using thermal simulation test, optical microscopy and transmission electron microscopy. As a result, the true stress versus true strain curves and the microstructures under various deformation conditions are obtained. The microstructures gradually incline to dynamic-recrystallization with the deformation temperature rising and the recrystallization grains refine with the decrease of deformation temperature or with raising the strain rates. The quantitative relationship between the Zener-Hollomon parameter （Z） and average recrystallization grain size in the subsequent heat treatment is set up.
文摘以重塑泥炭质土为研究对象,利用全球数字系统(global digital systems,GDS)动三轴仪对土体进行循环加载试验,分析一系列围压、固结比(Kc)、频率下土体滞回曲线演化规律,采用滞回曲线长轴斜率(k)、中心偏移量(d)、动应变幅值(εm)和包围的面积(S)对洱海高原湖相泥炭质土滞回曲线形态特征进行定量描述。试验结果表明:泥炭质土滞回曲线较为封闭,整体呈长梭形,在相同动应力幅值下,εm随围压、固结比、频率增大而减小,且减小速度逐渐降低;k随动应力幅值(σm)增大呈对数关系衰减,随围压、固结比、频率增大而增大,加载前期对频率变化表现不敏感;d和S随σm增大呈两阶段增大,加载前期增大平缓,后以指数关系快速增大;d和S随围压和频率增大而减小,且对频率变化表现更敏感;非等压固结(Kc≠1.0)条件下的d比等压固结(Kc=1.0)条件下更大,且S即土体完成一个荷载循环消耗能量更小。
基金financial support of Distinguished scholars of yueqi (NO. 800015Z1179)National Science Fund subsidized project (51474220)Basic scientific research project of the CPC Central Committee (NO. 2009QZ03)
文摘Using self-researched gas drainage borehole stability dynamic monitoring device, three-dimensional deformation characteristics of borehole under steady vertical load were researched experimentally and systematically. This research indicated that under the action of steady loading, the mechanical deformation path of the simulated gas drainage borehole is gradually complicated, and the decay of the borehole circumferential strain is an important characterization of the prediction and early warning of borehole instability and collapse. The horizontal position of borehole occurs compressive strain, and the vertical of which occurs tensile strain under the action of vertical stress. At the initial stage of loading, the vertical strain is more sensitive than that in the horizontal direction. After a certain period of time, the horizontal strain is gradually higher than the vertical one, and the intersection of the borehole horizontal diameter and the hole wall is the stress concentration point. With the increase of the depth of hole, the strain shows a gradual decay trend as a whole, and the vertical strain decays more observably, but there is no absolute position correlation between the amount of strain decay and the increase in borehole depth,and the area within 1.5 times the orifice size is the borehole stress concentration zone.
