BASED ON MATERIAL PROPERTIES TRANSFORMATION WITH LOAD STEPS

SHEN Xianfeng^1,2  YAO Jin²  WANG Yang¹  YANG Jialin¹

(1. Institute of Machinery Manufacturing Technology, China Academy of Engineering Physics, Mianyang 621900;
2. School of Manufacture Science and Engineering, Sichuan University, Chengdu 610065)

Abstract: Taking account of temperature-dependent thermal conduction and heat capacity, a three-dimensional finite element model of temperature field in DMLS has been established with the employment of the non-linear Finite Element Analysis (FEA)software MSC.Marc. As to the effect of extremely high thermal gradient caused by laser processing, the surface boundary conditions of surface convection and radiation is revised by using a coefficient. A method to transform element material properties between load steps is also taken for consideration of the regional-input high-power laser beam. Comparisons of simulation results between with the method and without it are conducted, and some conclusions are reached: Temperature gra- dient of the former one in the first steps is very great, which is consistent in the trend with the experimental phenomena; Heat affected zone of the former one is mainly confined in sintered region, while that of the latter one can reach the whole powder bed; The temperature of powder bed under the laser spot with increasing load steps of the former one remains constantly, while that of the latter one increases continuously. These are primarily caused by the hundred times rising of the thermal conductivity after laser sintering.

Key words: Rapid prototyping and manufacturing  Direct metal laser sintering  Numerical simulation  Finite element method  Temperature distribution

CLC No: TG665

中国工程物理研究院基金重大项目资助(2002Z0303).Received 20050624,received in revised form 20060215