Rehabilitation and Repair of Welded Elements and Structures by Ultrasonic Peening

Abstract

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.

Crack propagation analysis and rehabilitation by HFMI of pre-fatigued welded structures

“…Not only for un-cracked but also for pre-fatigued joints, recent investigations [10,38,39] show a great beneficial effect for rehabilitation by the HFMI treatment, whereas the fatigue strength of the repaired specimens is equal or even exceeds the HFMI-treated condition without pre-cycling. As described, prefatigued specimens with a crack depth of a ∼ 1 mm are analysed to assess the potential of HFMI as a rehabilitation method without additional re-welding.…”

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

“…In a different study [7,10], UP was applied to a number of large-scale welded specimens containing non-load carrying longitudinal attachments designed for fatigue testing (Fig. 4a) to study the prevention of possible initiation of fatigue cracks in existing welded elements and structures that are in service by applying UP during the weld repair of fatigue cracks.…”

“…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.…”

Accommodation of Plastic Deformation by Ultrasound-Induced Grain Rotation

“…Empirical equations (Eq. [2]) to estimate the average steady-state grain sizes during recrystallization [60][61][62] yielded D ¼ 7 lm.…”

“…Although reported results on fatigue life are very promising, [1,2] the detailed changes induced in the treated material and the mechanisms by which such changes occur are poorly understood. Ultrasonic impact treatment consists of an ultrasonic and a mechanical impact component.…”