Fatigue Improvement of Welded Elements and Structures by Ultrasonic Peening

Abstract

The ultrasonic impact treatment (UIT) is relatively new and promising process for fatigue life improvement of welded elements and structures. In most industrial applications this process is known as ultrasonic peening (UP). The beneficial effect of UP is achieved mainly by relieving of tensile residual stresses and introducing of compressive residual stresses into surface layers of a material. The secondary factors in fatigue improvement by UP are decreasing of stress concentration in weld toe zones and enhancement of mechanical properties of the surface layers of the material. Fatigue testing of welded specimens showed that UP is the most efficient improvement treatment as compared with traditional techniques such as grinding, TIG-dressing, heat treatment, hammer peening and application of LTT electrodes. The developed computerized complex for UP was successfully applied for increasing the fatigue life and corrosion resistance of welded elements, elimination of distortions caused by welding and other technological processes, residual stress relieving, increasing of the hardness of the surface of materials. The UP could be effectively applied for fatigue life improvement during manufacturing, rehabilitation and repair of welded elements and structures. The areas/industries where the UP process was applied successfully include: Shipbuilding, Railway and Highway Bridges, Construction Equipment, Mining, Automotive, Aerospace. The results of fatigue testing of welded elements in as-welded condition and after application of UP are considered in this paper. It is shown that UP is the most effective and economic technique for increasing of fatigue strength of welded elements in materials of different strength. These results also show a strong tendency of increasing of fatigue strength of welded elements after application of UP with the increase in mechanical properties of the material used.

Effects of ultrasonic impact treatment on pre-fatigue loaded high-strength steel welded joints

“…Other factors for the beneficial effect of UIT are decreasing of stress concentration in weld toe zones and enhancement of mechanical properties of the surface layer [4,8,13,14]. Fatigue testing of welded specimens showed that UP is the most efficient improvement treatment as compared with traditional techniques such as grinding, TIG-dressing, and hamming peening [15][16][17][18].…”

Protection of materials from hydrogen accumulation

“…For control and determination of hydrogen concentration we use the hydrogen analyzer AV-1. The precision hydrogen analyzer AV-1 has been designed for hydrogen detection in metals and alloys under the plant laboratory conditions during the outgoing control provided for different alloys [8][9][10][11][12]. The operating principle of the analyzer is mass-spectrometric.…”

“…One of these methods is Ultrasonic Peening treatment. Ultrasonic Peening (UP) is a promising technology in the application of High Power Ultrasound treatment for fatigue life improvement of welded structures [12,13]. The treatment is executed with a pin, from 2 to 5mm in diameter made from high strength steel.…”

Effectiveness of ultrasonic peening in fatigue improvement of welded elements and structures

“…In a study aimed at evaluation of the effectiveness of UP application in welding application, three series of largescale welded samples, designed as shown in Figure 3a, were subjected to fatigue testing in as-welded condition, with UP applied before fatigue testing and with UP applied after fatigue loading with the number of cycles corresponding to 50% of the expected fatigue life of samples in as-welded condition [9].…”

“…In most industrial applications this process is also known as ultrasonic peening (UP) [8][9][10][11][12]. The beneficial effect of UIT/UP is achieved mainly by relieving of harmful tensile residual stresses and introducing of compressive residual stresses into surface layers of materials, decreasing of stress concentration in weld toe zones and enhancement of mechanical properties of surface layers of the material.…”