PLA材料熔融沉积成型过程数值仿真分析

Numerical Simulation of PLA Material Melt Deposition Molding Process

为解决PLA材料在熔融沉积3D打印过程中,热力场和应力场变化导致成型精度较差的问题,基于热传导及弹塑性力学理论,采用有限元分析方法,利用液固耦合传热原理对成型过程进行空间、时间的离散分析,得到FDM成型过程材料温度传递规律;采用热-力结构间接耦合方法,建立了成型过程应力应变三维瞬态数学模型,在ANSYS软件中进行FDM成型过程的可视化仿真模拟。实验结果表明,在制件成型过程中,PLA材料挤出过程的初始热应力较小,然后,应力值迅速达到最大值,同时在成型件的边角处出现应力集中现象,产生应力集中区域的应力值范围为1.096 3~1.643 1 MPa,成型件单层形变值范围为0.000 3~0.001 9 mm/mm,主要形变发生在模型边缘部分,在材料堆叠成型过程中,该层的瞬态温度、应力及应变能直接影响相邻已成型的2层。

Aiming at the problem of poor forming accuracy caused by the change of thermal field and stress field of PLA material in the process of melt deposition 3D printing,based on the theory of heat conduction and elastic-plastic mechanics,the forming process was discretized in space and time by using the finite element analysis method and the principle of liquidsolid coupling heat transfer,and the material temperature transfer law in FDM forming process was obtained,the threedimensional transient mathematical model of stress and strain in the forming process was established by using the thermal mechanical structure indirect coupling method,and the visual simulation of FDM forming process was realized on the ANSYS platform.The experimental results showed that in the forming process,the initial thermal stress of PLA material extrusion process was very small,and then the stress value quickly reaches the maximum value,and the stress concentration phenomenon occurs at the edges and corners of the formed part,the stress value of the stress concentration area was 1.0963~1.6431 MPa,and the deformation value of the single layer of the formed part was 0.00095~0.00159 mm/mm.The main deformation occurs at the edge of the model.In the process of material stacking and forming,the transient temperature,stress and strain of the current layer directly affect the two adjacent formed layers.