Then the increment stress - strain relation of plasticity on the corner of the yielding surface is presented by the Koiter theory which is connected with the above hardening function.

The surface cracks in welded structures are assessed and investigated directly by the wide plate test according to the general yielding criteria and COD parameter.

The impact fracture surface morphology observed by SEM showed that the toughening mechanism of the blend was in accordance with that of the shear yielding.