Cold expansion process on hard alloy holes-experimental and numerical evaluation

Abstract

This paper presents an evaluation of the influence of the cold expansion process on the fatigue performance of holes in hard alloys, as such materials are involved in an increasing number of aeronautical applications. Fatigue enhancement could bring significant savings for numerous possible industrial applications. However, although the cold expansion of aluminium holes has been studied widely, there have been few publications concerning this process in hard alloys and there is currently very few research activities on technique dedicated to high strength metallic holes. Thus, this work aims to define an approach to understand why processes and methodologies are suitable for obtaining effective expansion of these materials. In this article, the response of expanded holes is studied, considering various experimental parameters and for a wide range of expansion ratios. The influence on the fatigue strength of Ti-6Al-4V tensile specimens is also reported for various expansion ratios, more precisely "standard" expansion ratios and high expansion ratios. Then, a specific numerical modelling of the process is presented, which enables us to understand the impact of high expansion ratios in titanium holes and the influence on fatigue performance. A very good correlation between experimental and numerical results is observed.

Optimization of the Cold Expansion Process for Titanium Holes

“…In the present problem, axisymmetric modeling appeared to be sufficiently representative of the phenomena operating over the vast majority of expanded sections, at least those that would be the most loaded during subsequent use. In previous work using these models, we obtained results that were very reliable compared with experimental results . So, in this study, we decided to develop other axisymmetric models of the process.…”

“…In the aeronautical industry, Ti‐6Al‐4V alloys are found in the great majority of titanium structural applications and are, therefore, considered in this study. As it can be seen in a previous article, few studies describe the implementation of expansion processes for hard alloys in the literature . No precise analysis of the response of hard metals subjected to expansion is reported and only studies of specific cases can be found, although generic processes designed for the expansion of holes in aluminum alloys are considered.…”

Analysis of Effectiveness of Combined Surface Treatment Methods for Structural Parts with Holes to Enhance Their Fatigue Life

“…V. Archard et al [13] assessed the influence of the cold expansion ratios on the fatigue strength of Ti-6Al-4V tensile specimens by conducting an experimental and numerical study. The aim of the study was to understand the impact of the high-expansion ratio in titanium holes and the influence on fatigue performance.…”