Manufacturers have been promoting multi-material designs. So, the
dissimilar material welding methods are being developed. We focused on
heat welding technologies for friction stir spot welding of aluminum
alloy and carbon fiber-reinforced plastic. This study investigated the
effect of changes to jig constraint of joined members on the fatigue
properties of joints. Also the fatigue life estimation was carried out
by considering the singular stress at the welding joint interface. As a
result, the fatigue strength of joint in a less constrained state is
higher than that in a more constrained state. The singular stress
intensity at the slit tip was uniformly predicted by the differences in
welding parameters of joints.