基于量纲分析的激光直接成形残余应力控制

CONTROL OF RESIDUAL STRESS FOR LASER AIDED DIRECT METAL DEPOSITION BASED ON DIMENSIONAL ANALYSIS

激光直接成形中,几何参数、材料属性和工艺参数等众多参量均会对残余应力造成影响,需要进行系统分析,采用量纲分析的方法,分别提取表征几何、传热和变形的3类关键无量纲参数,并结合三维瞬态有限元分析模型来研究这些无量纲参数对热致残余应力的影响规律,研究表明,选用热膨胀系数、屈服应力较小的材料,残余应力会较小;工艺控制中,可通过降低热散失、增大激光功率和提升预热温度来减小残余应力,其中预热的效果最好。

In the process of laser aided direct metal deposition （DMD）, the control of thermal-induced residual stress is very difficult, because the stress is affected by many parameters including geometrical dimensions, material properties and process parameters. In this paper, dimensional analysis is employed to extract key dimensionless parameters of geometry, heat transfer and thermal deformation. In addition, a 3D transient FEA model is proposed to study the effects of these key dimensionless parameters on the residual stress. It is shown that the residual stress can be controlled by employing materials with relatively small thermal expansion coefficient or small yield stress. Furthermore, the residual stress can be reduced by decreasing heat loss, increasing laser power, especially, by increasing preheat temperature.