2021 年 6 巻 p. 39-46
Round bars of SUS304 stainless steel were friction welded under five different conditions. The torsion tests were conducted on the friction-welded joints to obtain the torsional characteristics. The digital image correlation (DIC) was simultaneously applied to measure the full-field shear strain distributions in the inhomogeneous joint interface during torsional loading. Sufficient heat input per unit length in the upset stage was essential to obtain the joint with no defects and enough torsional strength. EBSD analysis also revealed that the recrystallized microstructure around the joint interface consists of very fine, equiaxed grains. For joints with no defects at the joint interface, local shear strains at the joint interface during torsional loading were smaller than those of a base material. This should be the result of increased interfacial hardness due to the reintroduction of dislocations into the recrystallized grains during the torsional load.
