基于空洞演化理论的挤压焊合描述模型

在铝合金管材分流挤压成形中，金属在焊合室内经历一个固态焊合过程，并在型材的整个长度方向上留下焊合缝。焊合缝通常是材料结构最薄弱的部位，为此焊合质量控制是挤压承压铝合金管材亟待解决的问题。针对挤压焊合过程定量描述的难题，将焊合过程描述为焊合面细观空洞的闭合过程，基于细观塑性力学方法建立焊合过程空洞演化模型。研究根据焊合面应力状态推导焊合面材料本构方程，并据此推导焊合面空洞闭合过程中孔隙度表达式，得到宏观应力场作用下描述挤压焊合的空洞演化模型；利用Gleeble热模拟试验机进行焊合过程的物理模拟试验，验证焊合描述模型的合理性，并基于该模型分析焊合质量的主要影响因素。研究提供一种挤压焊合过程定量描述方法，有助于揭示分流挤压焊合缺陷的形成机制。

Modeling of the Extrusion Seam Welding Based on the Void Evolution

During the divided flow extrusion process of aluminum alloy tube, the metal streams in welding chamber undergoes a solid welding process, which results in the formation of longitudinal weld seams in the whole length of extruded profile. Generally, the weld seams are the weakest part of extruded tubes, so seam welding quality is one of the key problems for aluminum alloy extruded tube working under high pressure conditions. Based on theory of the extrusion forming process and meso-plasticity, evolution mechanism of the voids at the seaming welding plane during the extrusion process is studied. A mathematic model which is able to describing the void closure process under macro stress field is established. Constitutive model of the material at the welding position was established and then an expression of the void closure process is deduced according to the process of the extrusion welding process. Further, physical simulation is done to validate the model and key factors affecting the welding status is examined. This study provides a quantitative means of evaluating the seam welding quality.