基于三维八节点内聚单元的固体火箭发动机粘接界面结构分析

Structural analysis on bonding interface of solid rocket motor based on 3D 8-node cohesive element

粘接界面应力状态是固体火箭发动机三维结构完整性分析的关键。首先在内聚参数松弛效应的基础上,建立了粘弹性PPR内聚力模型,构建了三维八节点内聚单元,推导了全局坐标系下单元变换矩阵,并进行了单元分离位移场的计算,结合八节点六面体等参单元,形成了单元内力矢量以及单元刚度阵。之后,以固化降温和点火增压两种典型工况为例,对发动机开展上述三维有限元分析。仿真结果表明,固化降温和点火增压两过程结束时,粘接界面上最大的切向内聚力分别为0.03 MPa和0.11 MPa,最大的法向内聚力分别为0.065 MPa和-0.348 MPa,均小于某发动机粘接界面的内聚强度。论文提出的基于三维八节点内聚单元的分析方法和研究结论可以为发动机粘接界面三维结构分析提供有利参考。

Stress state of the bonding interface is the key to 3D structural integrity analysis on solid rocket motor(SRM).Based on relaxation effect of cohesion parameters,a viscoelastic PPR cohesive zone model was established.To meet the requirements of 3D finite element simulation of SRM,a 3D 8-node cohesive element was constructed.The element transformation matrix in the global co-ordinate system was deduced and the element separation displacement field was calculated.The element cohesive force vector and el-ement stiffness matrix were formed by combining 8-node hexahedron isoperimetric element.Taking curing cooling and ignition pres-surization as examples,3D finite element analysis was carried out on the SRM,and the distribution characteristics of the normal and tangential stresses of the bonding interface were studied.The simulation results show that the maximum tangential cohesion force of the bonding interface is 0.03 MPa and 0.11 MPa,respectively,and the maximum normal cohesion force is 0.065 MPa and-0.348 MPa,respectively,which are lower than cohesive strength of the bonding interface,and the structural risk coefficient of the bonding interface is small.The analysis method and research conclusion based on the 3D 8-node cohesive element proposed in the paper can provide a favorable reference for the 3D structural analysis on the bonding interface for SRM.