METHOD FOR INCREASING THE ENDURANCE LIMIT, IN PARTICULAR THE BENDING STRENGTH AND TORSIONAL STRENGTH OF CRANKSHAFTS

摘要

At the time of introducing stress under pressure, the tool (14) of the impact machine (1) only executes a single movement relative to the crank shaft. This movement lies in the plane at right angles to the surface of the crank shaft segment which is being treated. - The crank shaft (4) is continuously rotated during processing. Rotary motion is arrested by the impact, during its momentary effect. The impact time and pressure are controlled to force the crankshaft to stop rotating momentarily. The impact frequency is 0.1-20 Hz, preferably 3-6 Hz. The impact pressure is preferably 50-110 bar. The temperature at the point of working, is 12-25 deg. C. The treatment follows processing to elevate the long term strength, e.g. induction hardening. Surface stressing due to impact treatment is subsequently reduced. A thickness of preferably 0.3-2mm is removed, by grinding, turning or milling. Procedures for elliptically-formed shaft sections is detailed. Further details of impact direction control are also included. An INDEPENDENT CLAIM is included for corresponding equipment.