焊接热效应对结构动力学性能影响的非线性分析

Non-linear influence of welding thermal effect on dynamic performance of structure

提出焊接热效应影响结构动力学性能,进行了理论推导并数值求解验证.从具有初始应力与应变的本构关系出发,应用虚功原理,理论推导出考虑焊接热效应的焊缝有限元单元刚度矩阵.进一步考虑结构的几何非线性和应力刚化效应影响,构建了模态非线性计算的特征方程.以船体舱段为研究对象,采用有限元模态分析方法,提取其在不同焊接热效应水平作用下的模态,发现焊接残余应力的存在不仅改变结构一阶固有频率,而且极有可能使一阶固有频率接近波浪频率.结果表明,结构潜在的焊接热效应对结构动力学性能影响不容忽视.

The influence of welding thermal effect on the dynamic performance of complex structure was proposed and confirmed by both formula derivation and numerical solution by finite element analysis method. Based on constitutive relation including initial stress and strain,the stiffness matrix considering the welding thermal effect was derived by employing the principal of virtual work. Then modified characteristic equation of modal analysis including geometric non-linear,stress stiffening and welding thermal effect was established. Modal analysis by taking a ship hull block as the example was performed to testify the derived equation and the first natural frequencies were extracted. The comparisons of different first natural frequencies induced by different levels of welding residual stress exhibited that the welding thermal effect obviously influenced the vibration performance of hull block by changing natural vibration frequencies of the structure. Especially,certain value of welding residual stress could even lower the first natural frequency nearly to wave frequency. The results show that the welding thermal effect played an important role in the dynamic performance of structure and could not be neglected in vibration analysis.