The dynamic recrystallization behavior of 35CrMo steel was studied with compression test in the temperature range of 1 223 1 423 K and the strain rate range of 0.01 10.00 s -1 . The initiation and evolution of dynamic...The dynamic recrystallization behavior of 35CrMo steel was studied with compression test in the temperature range of 1 223 1 423 K and the strain rate range of 0.01 10.00 s -1 . The initiation and evolution of dynamic recrystallization were investigated with microstructure analysis and then the critical strain ε c for dynamic recrystallization initiation, the strain for maximum softening rate ε * and the steady strain ε s were obtained to be 2.92×10 -3 Z 0.1381 , 1.60×10 -3 Z 0.178 0 and 3.26×10 -2 × Z 0.097 2 respectively by analysis of work hardening rate strain θ ε curves, where Z is the Zener Hollomon parameter. The dynamic recrystallization fraction was determined using recrystallization theory, and the effects of initial grain size, strain rate and deformated temperature on the dynamic recrystallization kinetics were investigated. The results show: X DRX =1- exp(-3.23( ε-ε cε s-ε c ) 2.28 ), the dynamic recrystallization fraction is slightly delayed due to the somewhat larger initial grain size and markedly delayed with the decrease of temperature. On the other hand, it is significantly accelerated with the increase of the strain rate. Finally, the relationships between the initiation time, ending time of dynamic recrystallization and the deformed temperature were analyzed in detail.展开更多
Based on dynamic triaxial test results of saturated soft clay, similarities of variations between accumulated pore water pressure and accumulated deformation were analyzed. The Parr＇s equation on accumulated deformat...Based on dynamic triaxial test results of saturated soft clay, similarities of variations between accumulated pore water pressure and accumulated deformation were analyzed. The Parr＇s equation on accumulated deformation was modified to create an attenuation-type curve model on accumulated pore water pressure in saturated normal consolidation clay. In this model, dynamic strength was introduced and a new parameter called equivalent dynamic stress level was added. Besides, based on comparative analysis on variations between failure-type and attenuatiun-type curves, a failure-type curve model was created on accumulated pore water pressure in saturated normal consolidation clay. Two models can take cycle number, coupling of static and dynamic deviator stress, and consolidation way into consideration. The models are verified by test results. The correlation coefficients are more than 0.98 for optimization of test results based on the two models, and there is good agreement between the optimized and test curves, which shows that the two models are suitable to predict variations of accumulated pore water pressure under different loading cases and consolidation ways. In order to improve prediction accuracy, it is suggested that loading cases and consolidation ways should be consistent with in-situ conditions when dynamic triaxial tests are used to determine the constants in the models.展开更多
文摘The dynamic recrystallization behavior of 35CrMo steel was studied with compression test in the temperature range of 1 223 1 423 K and the strain rate range of 0.01 10.00 s -1 . The initiation and evolution of dynamic recrystallization were investigated with microstructure analysis and then the critical strain ε c for dynamic recrystallization initiation, the strain for maximum softening rate ε * and the steady strain ε s were obtained to be 2.92×10 -3 Z 0.1381 , 1.60×10 -3 Z 0.178 0 and 3.26×10 -2 × Z 0.097 2 respectively by analysis of work hardening rate strain θ ε curves, where Z is the Zener Hollomon parameter. The dynamic recrystallization fraction was determined using recrystallization theory, and the effects of initial grain size, strain rate and deformated temperature on the dynamic recrystallization kinetics were investigated. The results show: X DRX =1- exp(-3.23( ε-ε cε s-ε c ) 2.28 ), the dynamic recrystallization fraction is slightly delayed due to the somewhat larger initial grain size and markedly delayed with the decrease of temperature. On the other hand, it is significantly accelerated with the increase of the strain rate. Finally, the relationships between the initiation time, ending time of dynamic recrystallization and the deformed temperature were analyzed in detail.
基金Project(2009AA11Z101) supported by National High Technology Research and Development Program of ChinaProject supported by Postdoctoral Science Foundation of Central South University,China+1 种基金Project(2012QNZT045) supported by Fundamental Research Funds for Central Universities of ChinaProject(2011CB710601) supported by the National Basic Research Program of China
文摘Based on dynamic triaxial test results of saturated soft clay, similarities of variations between accumulated pore water pressure and accumulated deformation were analyzed. The Parr＇s equation on accumulated deformation was modified to create an attenuation-type curve model on accumulated pore water pressure in saturated normal consolidation clay. In this model, dynamic strength was introduced and a new parameter called equivalent dynamic stress level was added. Besides, based on comparative analysis on variations between failure-type and attenuatiun-type curves, a failure-type curve model was created on accumulated pore water pressure in saturated normal consolidation clay. Two models can take cycle number, coupling of static and dynamic deviator stress, and consolidation way into consideration. The models are verified by test results. The correlation coefficients are more than 0.98 for optimization of test results based on the two models, and there is good agreement between the optimized and test curves, which shows that the two models are suitable to predict variations of accumulated pore water pressure under different loading cases and consolidation ways. In order to improve prediction accuracy, it is suggested that loading cases and consolidation ways should be consistent with in-situ conditions when dynamic triaxial tests are used to determine the constants in the models.
