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.
The Ultrasonic Peening (UP) is the most efficient technique for increasing the fatigue life of welded elements as compared to such existing improvement treatments as grinding, TIGdressing, shot peening, hammer peening, etc. The results of experimental investigation of the efficiency of UP for rehabilitation and repair of welded elements and structures with the goal of preventing the origination and propagation of fatigue cracks are considered in this document. UP treatment was applied to large-scale welded specimens in as-welded condition, after 50% of expected fatigue life and after repair of fatigue cracks. Also, different techniques for restraining and repair of fatigue cracks were analyzed and compared: overloading; drilling of the crack tips; drilling of the crack tips with installation of high strength bolts; local explosive treatment; local heat treatment; welding with and without UP of weld toe zones. As an example, the practical application of UP for rehabilitation and repair of welded elements of highway and railway bridges are also discussed.
The application of an ultrasonic non-destructive method for residual stress (RS) measurements has shown that, in many cases, this technique is very efficient and allows measuring the RS both in laboratory conditions and in real structures in field for a wide range of materials. Using this technique, one can measure the RS at the same points many times, studying for instance, the changes of RS under the action of service loading or effectiveness of stress-relieving techniques. An ultrasonic computerized complex (UCC) for non-destructive measurement of residual and applied stresses was developed recently. The complex includes a measurement unit with transducers, basic supporting software, an advanced database and an Expert System, housed in a laptop, for analysis of the influence of RS on the fatigue life of welded elements. In general, the ultrasonic method allows one to measure the RS in both cases: averaged through thickness or in surface layers. The present version of UCC allows measuring the averaged through thickness biaxial RS in plates 2–150 mm thick. The results of ultrasonic RS measurement in large scale welded specimens and structures are also discussed in this paper.
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 UIT/UP is achieved mainly by relieving of harmful tensile residual stresses and introducing of compressive residual stresses into surface layers of a material, decreasing of stress concentration in weld toe zones and enhancement of mechanical properties of the surface layers of the material. The UP technique is based on the combined effect of high frequency impacts of special strikers and ultrasonic oscillations in treated 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.
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