2017 年 66 巻 7 号 p. 528-533
Composite materials made from two or more different components are widely used in fields ranging from semiconductor devices to mechanical structural materials. Depending on the environment, this construction material may be subjected to mechanical loads and thermal stress, and this may lead to problems such as delamination. The occurrence of such delamination is expected to be strongly dependent on the residual stress subjected to loading processes. In the present study, the influence of a repeated tensile bending load on the residual stress in the Cu film and the carbon steel in Cu-coated steel was investigated. In the absence of a Cu coating, it was shown that the residual stress in the steel changed to the compression side due to the application of a repeated tensile bending load. Furthermore, the magnitude of the compressive stress increased as the surface roughness of the substrate decreased. In the case of the Cu-coated steel under the same load, the residual stress was slightly tensile stress decreased, but its magnitude did not depend on the surface roughness. In the Cu coating itself, the residual stress was originally tensile, but its magnitude decreased under repeated loading. This decrease was much more significant when the surface roughness of the substrate was low.