Applying Digital Image Correlation Technique for Studying the Growth of a Fatigue Crack in VT23 Titanium Alloy Welded Joints
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We present results of applying a combined approach to studying fatigue fracture processes in VT23 titanium alloy with a laser-welded joint. The approach involves fractographic examination using scanning electron microscopy and analysis of strain fields at the sample surface (using digital image correlation technique). Samples with permanent connections are presented in two forms: in the initial state and subjected to post-welding treatment by ultrasonic forging and pulsed high-energy impact. It is shown that applying the proposed integrated approach to the analysis of fatigue fracture has allowed identifying features in the development of processes of nucleation and propagation of cracks and locating them in the bulk of the material, as well as determining running times after which transition from one stage to another takes place: crack initiation, stable growth, and rupture. The results have made it possible to explain the mechanisms of how post-welding treatment of permanent joints affects their fatigue properties.
Keywords:fatigue digital image correlation method fractographic examination VT23 titanium alloy welded joints laser welding post-welding treatment
The authors are grateful to A.M. Orishich and A.G. Malikov (ITAM SB RAS) for providing samples of VT23 alloy with welded joints manufactured by laser welding.
The experimental work was carried out within the framework of the program of fundamental research of the state academies of sciences for 2013–2020, direction III.23. The estimation of crack growth parameters by the digital image correlation method was supported by the Fellowship of the President of the Russian Federation for young scientists and graduate students in 2018–2020, project no. SP-198.2018.4, and Russian Foundation for Basic Research, project no. mol_a # 18-38-00659.
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