抄録
The strain-concentration factor was calculated using finite element method for plane-strain rectangular bars with a single-edge U-notch under pure bending. The strain-concentration factor employed is newly defined under the triaxial stress state at the net section. This new strain-concentration factor increases from its elastic value to the maximum as plastic deformation develops from the notch root. The maximum strain-concentration factor of a shallow notch is considerably greater than that of a deep notch, although the elastic strain-concentration factor is reversed. Plastic deformation around the notch root has a stronger effect on the strain-concentration factor of shallow notches. This is because plastic deformation develops mainly in the vicinity of the notch root for shallow notches. The strain-concentration factor employed here corresponds well to the distribution of the longitudinal strain at the net section. The variation of the strain-concentration factor with M/MY, the ratio of bending moment to that at yielding at the notch root, is dependent on the stress-strain curve for shallow notches, especially beyond the deformation level at which the maximum strain-concentration factor occurs. The integral of the longitudinal strain at the net section is negative in elastic deformation for single-edge notches. It varies from negative to positive value with plastic deformation around the notch root.
