A new model for describing the compaction process of iron powder was proposed based on the continuum hypothesis and elliptical yield criterion.To simulate the densification behaviour,the constitutive model was impleme...A new model for describing the compaction process of iron powder was proposed based on the continuum hypothesis and elliptical yield criterion.To simulate the densification behaviour,the constitutive model was implemented in Marc computer program.For the relationship between load and displacement,different models were compared and the influence of the parameters in the constitutive equations was determined by means of simulation and experiments.The density distribution of a balancer was measured and simulated.The results show that the parameterηadopted plays a modification role for the load-displacement curve,and compared with other models the present model fits better with the experimental data in the later stage of the compaction process mainly due to the different parameters A and B.The friction on the contact surface contributes to the inhomogeneous density distribution under large deformation of the workpiece.The comparison between the simulation and experimental data indicates that this model can be used to predict the powder compact process precisely and effectively.展开更多
The interaction of continuous wave （CW） fiber laser with Ti-6A1-4V alloy is investigated numerically and experi- mentally at different laser fluence values and ambient pressures of N2 atmosphere to determine the mel...The interaction of continuous wave （CW） fiber laser with Ti-6A1-4V alloy is investigated numerically and experi- mentally at different laser fluence values and ambient pressures of N2 atmosphere to determine the melting time threshold of Ti-6A1-4V alloy.＇ A 2D-axisymmetric numerical model considering heat transfer and laminar flow is es- tablished to describe the melting process. The simulation results indicate that material melts earlier at lower pressure （8.0 Pa） than at higher pressure （8.8x 104 Pa） in several milliseconds with the same laser fluence. The experimental results demonstrate that the melting time threshold at high laser fluence （above 1.89x 108 W/m2） is shorter for lower pressure （vacuum）, which is consistent with the simulation. While the melting time threshold at low laser fluence （below 1.89x 108 W/m2） is shorter for higher pressure. The possible aspects which can affect the melting process in- clude the increased heat loss induced by the heat conduction between the metal surface and the ambient gas with the increased pressure, and the absorption variation of the coarse surface resulted from the chemical reaction.展开更多
基金Project(50325516) supported by the National Natural Science Foundation of ChinaProject(CG2003-GA005) supported by China Education and Research Grid(China Grid)+1 种基金Project(003019) supported by the Natural Science Foundation of Guangdong Province,ChinaProject(2009ZM0290) supported by the Fundamental Research Funds for the Central Universities,China
文摘A new model for describing the compaction process of iron powder was proposed based on the continuum hypothesis and elliptical yield criterion.To simulate the densification behaviour,the constitutive model was implemented in Marc computer program.For the relationship between load and displacement,different models were compared and the influence of the parameters in the constitutive equations was determined by means of simulation and experiments.The density distribution of a balancer was measured and simulated.The results show that the parameterηadopted plays a modification role for the load-displacement curve,and compared with other models the present model fits better with the experimental data in the later stage of the compaction process mainly due to the different parameters A and B.The friction on the contact surface contributes to the inhomogeneous density distribution under large deformation of the workpiece.The comparison between the simulation and experimental data indicates that this model can be used to predict the powder compact process precisely and effectively.
基金supported by the National Natural Science Foundation of China for Young Scholars(No.11402120)the Jiangsu Provincial Natural Science Foundation for Young Scholars(No.BK20140796)the Fundamental Research Funds for the Central Universities(No.30915015104)
文摘The interaction of continuous wave （CW） fiber laser with Ti-6A1-4V alloy is investigated numerically and experi- mentally at different laser fluence values and ambient pressures of N2 atmosphere to determine the melting time threshold of Ti-6A1-4V alloy.＇ A 2D-axisymmetric numerical model considering heat transfer and laminar flow is es- tablished to describe the melting process. The simulation results indicate that material melts earlier at lower pressure （8.0 Pa） than at higher pressure （8.8x 104 Pa） in several milliseconds with the same laser fluence. The experimental results demonstrate that the melting time threshold at high laser fluence （above 1.89x 108 W/m2） is shorter for lower pressure （vacuum）, which is consistent with the simulation. While the melting time threshold at low laser fluence （below 1.89x 108 W/m2） is shorter for higher pressure. The possible aspects which can affect the melting process in- clude the increased heat loss induced by the heat conduction between the metal surface and the ambient gas with the increased pressure, and the absorption variation of the coarse surface resulted from the chemical reaction.
