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Fatigue strength enhancement of welded joints in existing steel bridges using high-frequency mechanical impact treatment
Published in Joan-Ramon Casas, Dan M. Frangopol, Jose Turmo, Bridge Safety, Maintenance, Management, Life-Cycle, Resilience and Sustainability, 2022
T. Hanji, K. Tateishi, S. Kano, M. Shimizu
Past studies have investigated the fatigue strength of longitudinal attachment joints treated by ultrasonic impact treatment (UIT) under different stress levels (Mori et al. 2011). The fatigue test results have shown the possibility that the fatigue strength of welded joints is enhanced more than twice compared to as-welded joints, although the stress ratio is 0.5, when UIT is performed under a condition in which the maximum fatigue loading is statically applied (Mori et al. 2011). This means that it may not be necessary to consider the negative effect of the stress ratio on fatigue strength enhancement by HFMI treatment if it is performed when the structure is already in service, namely when a dead load is applied prior to treatment. Although this concept has been described in the IIW recommendation (Marquis & Barsoum 2016) and the AASHTO LRFD Bridge Construction Specifications (AASHTO 2010), this point needs to be well verified from the viewpoint of local residual stress field as well as fatigue strength in HFMI-treated joints.
Fatigue strength improvement of welded joints using SBHS700 by applying ICR treatment.
Published in Nigel Powers, Dan M. Frangopol, Riadh Al-Mahaidi, Colin Caprani, Maintenance, Safety, Risk, Management and Life-Cycle Performance of Bridges, 2018
Figure 1 shows the SBHS700 I girder specimen. The I girder was 6400 mm long and had a web that was 600 mm wide by 12 mm thick, and flanges that were 300 mm wide by 12 mm thick. A set of six 160 mm*70 mm*12 mm plates were welded 80 mm from the top and the bottom of the web, evenly spaced at 360 mm apart on both sides of the webs as well. According to the previous study, preheating of 50 °C was applied to the base metal, and the YM-80C (JIS Z 3312) electrode was used in a CO2 type of welding. A full penetration welding process was carried out. The weld toe profiles were used by three types of fatigue strength improvement methods, which are BG (Burr Grinding), UIT (Ultrasonic Impact Treatment) and ICR. In the girder specimen, the nominal stress was constant of 100 N/mm2 on each gusset and the stress ratio was 0.1. The fatigue test was finished at approximately 1.5 million cycles because both of as welded gussets failed. Table 1-2 show the mechanical properties and the chemical compositions of SBHS700, respectively.
Giving new life to fatigue life-expired critical details
Published in Hiroshi Yokota, Dan M. Frangopol, Bridge Maintenance, Safety, Management, Life-Cycle Sustainability and Innovations, 2021
J.M. Bonnett, R.A. Percy, P.J. Robinson, K. Antoniou
Ultrasonic impact treatment (UIT) was also considered but not trialled because it could not be assured in this situation that the treatment was able to eliminate existing damage (micro-cracking) or provide codified improvements in fatigue life. The high stresses experienced by the bottom flange plates of the structure in service were also a key factor in discounting this technique because they can remove the surface compression benefit of the UIT treatment, which forms an important component of the fatigue improvement.
An investigation on microstructure and mechanical properties of 316 stainless steel: a comparison between ultrasonic treatment and thermal annealing
Published in Philosophical Magazine, 2022
Milad Zohrevand, Mehrdad Aghaie-Khafri, Farnoosh Forouzan, Esa Vuorinen
Ultrasound has also been employed to modify the microstructure and properties of different alloys. The grain refinement and stress relieving of welded metals through ultrasonic peening is a well-known industrial process [19]. Imposing the ultrasonic vibration during the molten metal solidification can lead to a finer grain structure in metal casting and additive manufacturing processes [20, 21]. Ultrasonic impact treatment is another application technique that can introduce nano-structured layers in the surface and significantly improve the material fatigue properties [22].
FE analysis of shot-peening-induced residual stresses of AISI 304 stainless steel by considering mesh density and friction coefficient
Published in Surface Engineering, 2019
Gang Wu, Zhou Wang, Jin Gan, Ying Yang, Qingshuai Meng, Shun Wei, Haiming Huang
In this work, AISI 304, which is a typical austenitic stainless steel widely used in industry applications due to its excellent corrosion and oxidation resistance, good strength and high toughness properties, was chosen as the SP material. Some experimental and simulated SP research was carried out on austenitic stainless steel in the last 10 years. In terms of experimental work, Zhan et al. [21] investigated the effect of different prestress states on residual stress of S30432 austenitic stainless steel after SP and concluded that the CRS was improved significantly after stress SP, and the increment of CRS was proportional to the prestress state. The following year Zhan et al. [22] focused on the uniformity of CRS distributions on the surface of S30432 austenitic stainless steel after different SP treatments by X-ray diffraction (XRD) methods and the results revealed that multi-step SP (dual SP, triple SP) methods can make the residual stress distribution more uniform. Fargas et al. [23] evaluated the effect of SP on austenite to martensite phase transformation of austenitic stainless steels. In terms of simulated work, Yang et al. [24] investigated the influence of ultrasonic impact treatment (UIT) on surface integrity and mechanical properties of AISI 304 stainless steel via experimental and simulated methods. The SP simulation characterising the dynamic response of AISI 304 during UIT process based on Johnson–Cook model was built with the aim of understanding fundamental mechanisms about UIT process. Li et al. [25] built a single and multiple impingement SP model by considering the influence of coverage ratio on the residual stress and equivalent plastic strain. However, the deformation-induced martensitic transformation in AISI 304 was not considered in this model. Zhan [26] proposed a 3D SP model based on the Johnson–Cook constitutive equation of S30432 austenitic stainless steel, and the simulated residual stresses distribution was in good accordance with the experimental results. Interestingly, XRD results showed that stress-induced martensite did not appear on specimen surface after the SP treatment.