Fatigue assessment of Ti-6Al-4V titanium alloy laser welded joints in absence of filler material by means of full-field techniques

Pasqualino Corigliano,Vincenzo Crupi,Emanuele Sgambitterra,Eugenio Guglielmino,Carmine Maletta,Fabrizia Caiazzo,Giuseppe Barbieri

doi:10.3221/igf-esis.43.13

Abstract

The aim of this research activity was to study the fatigue behavior of laser welded joints of titanium alloy, in which the welding was performed using a laser source and in the absence of filler material, by means of unconventional full field techniques: Digital Image Correlation (DIC), and Infrared Thermography (IRT). The DIC technique allowed evaluating the strain gradients around the welded zone. The IRT technique allowed analyzing the thermal evolution of the welded surface during all the fatigue tests. The fatigue limit estimated using the Thermographic Method corresponds with good approximation to the value obtained from the experimental fatigue tests. The obtained results provided useful information for the development of methods and models to predict the fatigue behavior of welded T-joints in titanium alloy.

Highlights

Titanium alloys, in general, are employed in various applications, ranging from aerospace sector, passing from the naval sector, to medical and surgical devices [1]
The goal of this research activity was to study the fatigue behavior of laser welded joints of titanium alloy, in which the welding was performed using a laser source and in the absence of filler material, by means of unconventional full field techniques: the digital image correlation (DIC, Digital Image Correlation) and the Infrared Thermography (IRT, Infrared Thermography), in order to analyze the behavior in the surrounding areas of geometric discontinuities and the different material properties
The fatigue tests were led using loading systems developed ad-hoc and systematic analysis of the results obtained by the DIC and IRT techniques has allowed to better understand the mechanisms of evolution of the local damage within the joints during the application of cyclic loading

Summary

INTRODUCTION

In general, are employed in various applications, ranging from aerospace sector (turbine disks, blades of the compressors, structural elements), passing from the naval sector, to medical and surgical devices [1]. Given the complex workability of the material with the common techniques, as well as the higher specific cost compared to the most common metallic alloys, the development and tuning of joining techniques suitable to this type of alloys it is undoubtedly one of the factors that most influence the possible dissemination to industrial sectors with lower value added. In this context, the laser weld is considered as an alternative to the traditional techniques to operate the joining of plates of titanium alloys. Full-field techniques were already applied by some of the authors have already applied full-field for the assessment of different materials: AA6082 aluminum alloy [12], S355 and high strength steels [13, 14], AISI4140 steel in very high cycle fatigue regime [15], Iroko wood under static loading [16, 17] and shape memory alloys [18]

MATERIALS AND METHODS

RESULTS AND DISCUSSION

CONCLUSION