The strength fluctuation of adhesively bonded joints subjected to a high temperature condition has experimentally been investigated. The specimens of a single-lap joint bonded with an epoxy adhesivewere kept in Argon gas environment at 150℃ for up to 100 h and tested in terms of lap-shear strength.In addition, the other type of specimens, which have cured adhesive layers on the same substrate as the single-lap joint specimens, were prepared and kept in the same environment and temperature in order to investigate the color change of the adhesive layers due to oxidation at a high temperature.The joint strengths did not decrease but slightly increase after the exposure in Argon environment of a high temperature as the same as in air. The color of an adhesive layer confined in the joints didnot change, the marginal area of the adhesive layer, however, exhibited color change from white to yellow. The cured adhesive specimens on the substrates also exhibited the same color change.

In this study, the shear deformation behavior of adhesive layer in stretch-bending/unbending foradhesively bonded dissimilar sheet metals was investigated by two types of experiments and finiteelement analysis. Major results obtained are summarized as follows:（1）The shear deformation behaviorof adhesive layer was observed in bending/unbending tests with two experimental apparatus.（2）The shear deformation of adhesive layer was influenced by the die corner radius and the tensilespeed.（3）The tensile strength of adherend has a large influence on the shear deformation behavior ofadhesive layer. It is possible to suppress the shear deformation of adhesive layer by using a materialwith small tensile strength as one of the two adherends.（4）The delamination of adhesive layer wasoccurred when the shear strain of adhesive layer in stretch-bending/unbending exceeded a certainvalue（approximately 1.7）.（5）FEM analysis was carried out with using constitutive equations possibleto express the visco-plastic behavior obtained in previous research. However the new yield functionwas proposed in this study for improving the precision of FEM analysis, an expected result was notobtained.