本课题拟以普遍用于制造飞机机体、汽车车身的Al-Si/Al-Mg系铝合金为研究对象，采用微观与宏观力学模型相结合的建模方法系统研究激光焊接过程中接头的力学行为及热裂纹敏感性，探究激光焊接过程中热裂纹敏感性与过程参数的关系。研究将基于宏观热力学全尺度模型，获取整个激光焊接接头的动态温度场及应力应变场，提取关键部位建立包含晶粒形貌、液膜分布及低熔组分的微观热力学模型，计算晶粒间及液膜的微观应力应变，分析微观损伤的可能性，并将微观模型获取的结果嵌入到全尺度模型，以提高全尺度模型应力应变计算的准确性，从而实现以微观模型与宏观模型多尺度耦合的方式研究异种铝合金激光焊接过程中参数变化与微观动态应力应变的关系及与热裂敏感性的内在联系。多尺度焊接过程力学模型的成功建立，将提高焊接过程材料力学分析的准确性，开辟新的揭示铝合金高效激光焊接热裂纹产生机制的研究途径，指导铝合金焊接热裂纹问题的解决。

The proposed research develops a multiscale mechanics model in studying the hotcracking sensitivity with respect to various process parameters in Al laser welding. The study will start from a macroscale welding mechanics model to obtain dynamic temperature and stress/strain distribution in the field. At the zones of the interest a microscale model which considers grain boundaries,liquid films and composition of eutectics will be constructed to calculate the stress/strain at the micro level and analyze stress and strain between the grain boundaries and at the liquid films. The deformation calculated at the micro scale will be coupled into the macroscale model to reflect effect of the local heterogeneity so as to improve the stress/strain calculation at the macro level. The hotcracking sensitivity will then be discussed with respect to various combinations of process parameters. The success of the proposed multiscale modeling research helps to improve accuracy of material machanics analysis in welding process, provides a foundation in further studying the hotcracking growth in Al laser welding and guides the solution development for the Al hotcracking problem.