The residual stress distributions of bonded dissimilar materials were determined by the two- and three-dimensional (2-D and 3-D) thermoelastoplastic stress analyses using FEM. A silicon nitride plate was brazed to a carbon steel plate, a thin copper plate being sandwiched between them to eliminate the high residual stress generation by brazing. Two kinds of specimens of different sizes, 30×110×14mm and 30×44×5mm, were prepared. The residual stress on the surface of the silicon nitride was also measured by X-ray diffraction.
In the 2-D FEM, the stress was calculated by assuming the plane stress state. In the interfacial region, the stress distributions of the two specimens were similar independently of the size of the specimen. In the central region on the surface of the specimen, the stress σ
x, in the direction perpendicular to the interface, calculated by the 2-D FEM changed slowly, taking tensile and compressive values in the steel and silicon nitride, respectively. On the other hand, the 3-D FEM gave sharp compressive and tensile stress peaks in the steel and silicon nitride, respectively. As the distance from the interface increased, the stresses calculated by the 2-D and 3-D FEM agreed each other and vanished at a longer distance from the interface. The maximum tensile stress σ
x appeared at the upper and lower corners near the interface in the silicon nitride. In the interfacial region, the stress σ
x calculated by the 3-D FEM changed rapidly in the cross section of the specimen, although in the 2-D FEM the stress was assumed to be unchanged through the thickness of the specimen. These results suggest the need for the 3-D stress analysis for calculating the residual stress of the bonded dissimilar materials.
抄録全体を表示