Efficiency of Ultrasonic Peening in Fatigue Improvement
G.Prokopenko (G.V.Kurdyumov Institute for Metal Physics NAS of Ukraine, Kiev, Ukraine); P.P.Miheev (Paton Welding Institute NAS of Ukraine, Kiev, Ukraine)
The Ultrasonic Peening (UP) produces a number of beneficial effects in metals and alloys. Foremost among these is increasing the resistance of materials to surface-related failures, such as fatigue, wear and other. The results of fatigue testing showed that UP is the most efficient technique for increasing the fatigue life of welded elements as compared to such existing improvement treatments as shot peening, hammer penning, etc. Equipment for UP treatment of parts and welded elements based on piezoelectrtic transducers was developed recently. Equipment consists of a compact ultrasonic transducer, power supply and set of changing instruments with various peens. Application of UP treatment may increase (restore) the designed stress range of welded elements up to the fatigue strength of the base material. This report describes the results of investigation of the mechanism and efficiency of UP for increasing the fatigue life of welded elements (low carbon steel, aluminum alloys). The increase in fatigue life by UP is achieved mainly by relieving of harmful tensile residual stress and introducing compressive residual stress into surface layers of metals and alloys, decrease in stress concentration of weld toe zones and enhancement depends greatly on the level of induced compressive residual stresses, mechanical properties of used material, the type of welded element, parameters of cyclic loading and other factors. The main factors determining the efficiency of UP application and results of fatigue testing of welded elements are considered in details.
Section : 11