Experimental and numerical study on the residual stress in a lattice truss sandwich structure: Effect of geometrical dimensions of punching die

This paper uses the finite element method (FEM) and nanoindentation experiment to study the residual stress of a stainless steel pyramidal lattice truss sandwich structure, and the effect of geometrical dimensions of punching die including punching angle and punching length have been investigated. The results show that large residual stresses are generated in the brazed joint, and a thickness reduction and longitudinal shrinkage deformation are generated. The thickness reduction is almost entirely due to the reduction in the length of the truss rather than the thinning of the filler metal, and the longitudinal shrinkage deformation is caused by the shrinkage of filler metal. With the punching angle increase, both the residual stress and the thickness reduction deformation are increased; too small punching angle can lead to much larger residual stress. The punching length has little effect on peak residual stress, but the residual stress and thickness reduction deformation are increased with the punching length increase. The punching angle and punching length has little effect on the longitudinal shrinkage deformation.