Defect sensitivity in additively manufactured aluminium alloys: contribution of CAD artificial defects

Matthieu Bonneric,Charles Brugger,Nicolas Saintier,T Palin-Luc,A Carpinteri,F Morel

doi:10.1051/matecconf/201930003006

Abstract

The prediction of the fatigue resistance of additively manufactured parts is a current issue for the materials and process qualification in aerospace industry. Despite a continuous improvement of AM process, the presence of defects cannot yet be completely avoided, and the latter are still one of the main causes of fatigue damage in AM materials. In this framework, the present work focused on the influence of defects on the uniaxial fatigue behavior of AlSi7Mg0.6 alloy produced by Selective Laser Melting (SLM). Uniaxial fatigue tests have been performed. Fatigue specimens were subjected to a T6 treatment, and then machined in order to avoid the influence of surface roughness. Besides, for some specimens, artificial defects were directly introduced through CAD. The introduction of artificial defects, whose sizes and positions are precisely controlled, aims to provide a proper assessment of defect sensitivity. X-ray tomography was used to characterize both natural and artificial defects. Finite-element calculations of the local stress fields in the vicinity of defects were conducted, accounting for the real defect geometries obtained with CT scans. The application of a non-local multiaxial fatigue criterion then allowed to analyze defect criticity.

Highlights

Over the past years, the production of Al-Si alloys by Selective Laser Melting (SLM) has been broadly studied, attempting to understand the relations between process parameters, microstructure, and mechanical properties [1]
The present work focused on the influence of defects on the uniaxial fatigue behavior of AlSi7Mg0.6 alloy produced by Selective Laser Melting (SLM)
The aim of this study is to investigate the defect sensitivity of an AlSi7Mg0.6 alloy obtained by SLM

Summary

Introduction

The production of Al-Si alloys by Selective Laser Melting (SLM) has been broadly studied, attempting to understand the relations between process parameters, microstructure, and mechanical properties [1]. This method was already employed to model the fatigue strength of cast aluminium alloys [8] and of an AlSi10Mg alloy obtained by SLM [4]. This kind of approach presents some limitations, especially because of the so-called short crack problem for which Linear Elastic Fracture Mechanics (LEFM) is not applicable [9], and is not convenient for multiaxial conditions. The fatigue criterion can be modified to account for it, either by averaging the stress over a physical dimension (point, length or volume) [10, 11], or by the explicit introduction of the stress field gradient in the criterion [12]

Objectives

Methods

Results

Conclusion