METHOD OF IMPROVING RESIDUAL STRESS IN TUBE BODY AND DEVICE FOR IMPROVING RESIDUAL STRESS

摘要

An obj ect is to provide a method and a system for improving a residual stress in a tube body, with which the residual stress can reliably be improved without heating excessively. From an irradiation start angle ¸s to a first predetermined angle ¸1 on the tube body, an intensity of a laser beam is gradually increased from 0.5 to the steady output of 1.0 output ratio; from the first predetermined angle ¸1 to a second predetermined angle ¸2, the intensity of the laser beam is set at 1.0 output ratio; from the second predetermined angle ¸2 to an irradiation end angle ¸e, the intensity of the laser beam is gradually decreased from the 1.0 output ratio to 0.5; and at the irradiation end angle ¸e, the intensity of the laser beam is set to 0. All these steps are performed at one turn of rotation in the method and the system for improving residual stress in the tube body.