焊接变形预测中基于假定热应变法的弹性有限元建模

Development of Elastic Finite Element Model for Predicting Welding Deformation Based on Artificial Thermal Strain Method

传统的固有应变法在固有应变载荷的施加中,因难以准确反映实际固有应变分布规律而影响焊接变形预测精度。通过传统等效载荷法与应变直接边界法的融合优化,所提出假定热应变法能够有效弥补传统载荷法逐层输入固有应变载荷的失真,以及应变直接边界法无法预测凸型角变形及纵向弯曲的不足。同时,该方法通过等效力学模型综合考虑多样的固有应变分布,使由凸型角变形和凹型纵向弯曲组成的马鞍形屈曲变形实现准确的分析计算。通过试验、热-弹塑性有限元模型,应变直接边界法弹性模型和假定热应变弹性模型综合比较,研究5052铝合金平板堆焊下所形成的屈曲变形。结果表明,假定热应变弹性模型对屈曲变形实现准确和快速的预测,可以应用于大型焊接结构及激光增材制造中的变形预测,并能够为固有应变理论中实现实际固有应变分布的转换提供新的思路。

The traditional inherent strain method is difficult to accurately apply the inherent stain loads which reflect the actual inherent strain distribution. Hence, it affects the accuracy of predicting welding distortion. With merging the advantages of the equivalent load method and the strain as direct boundary method, the proposed artificial thermal strain method can effectively solve the problem of lack fidelity in the traditional load method with considering the inherent strain layer by layer, and predict the convex angular deformation and longitudinal bending which the strain as direct boundary method was not able to. Simultaneously, this method comprehensively considers the various inherent strain distribution through the equivalent mechanical model which makes the saddle-shaped buckling deformation composed of convex angular deformation and concave longitudinal bending can be accurately analysed and calculated. Through the experiments, thermo-elastic-plastic finite element model, strain as direct boundary method and artificial thermal strain elastic method, the buckling deformation of 5052 aluminium alloy bead on plate was studied. The results show that the elastic model based on artificial thermal strain method can predict the buckling deformation accurately and quickly, which could be applied to predict the deformation of large-scale welded structures and laser additive manufacturing. And it also provides a new method to realize the conversion of the actual inherent strain distribution in the inherent strain theory.