Profilometry-based Indentation Plastometry (PIP): A Novel Method to Support Failure Analysis in Aerospace

Ascertaining the causes of failure of metallic aerospace components can require the determination or verification of mechanical properties. When small and/or irregularly shaped parts are the only material available, these may not be well-suited for extracting a mechanical test coupon, or such destructive sectioning may limit further investigations. This may cause the investigator to make (micro)hardness tests, but deriving mechanical data from these can introduce significant error. A more robust method is desirable.

This study reports an exploration and evaluation of Profilometry-based Indentation Plastometry (PIP) as a novel, alternative technique to hardness or tensile testing for use in the aerospace industry. PIP combines an indentation-based method with iterative finite element analysis (FEA) to obtain a stress-strain curve of the metallic sample being tested, and while conventional tensile testing requires standard coupon geometries and significant volumes of material, PIP can be performed on a variety of geometries, and on sample volumes as low as 3 x 3 x 1.5 mm; ideal for semi-non-destructive evaluations of stress-strain behaviour from failed parts.

In this study, PIP measurements are performed on aerospace-grade 2XXX and 7XXX aluminium alloy samples and contrasted with results from comparative tensile testing. Distributions of standard mechanical properties (such as yield stress and ultimate tensile strength) are compared and discussed in the context of failure analysis as well as wider applications in other areas where fine-scale mechanical testing proves challenging.