Derivation of material properties using small punch and shear punch test methods

R.J Lancaster,S.P Jeffs,B.J Haigh,N.C Barnard

doi:10.1016/j.matdes.2022.110473

Abstract

The Small Punch (SP) and Shear Punch (ShP) tests are well established mechanical test approaches that have found application in several industrial sectors for material ranking and mechanical property estimation, particularly where more conventional approaches are inhibited. Despite the advantages that the two test methodologies have to offer, the main drawback is the complex understanding of the mechanical data generated from the experiments and how it can be correlated to more recognised properties. Typically, the most desired properties relate to the uniaxial properties of yield stress, ultimate tensile strength and ductility, but to date, there is no single robust and overarching approach for correlating such properties for a wide array of metallic materials that exhibit varying levels of ductility. This paper will for the first time directly compare properties obtained from a series of uniaxial tensile, SP and ShP tests across several metallic materials, and look to establish and correlate equivalent properties across the different test types. The materials investigated range from commercially pure entities to more advanced alloy systems. The generated results, empirical relationships and numerical simulations will inform which materials can be correlated across the different test regimes, and identify why the relationship in certain materials breaks down.

Highlights

Ical characterisation of any novel material at the development stage can be an expensive activity when accounting for the relatively large volume of material required and likely restricted material availability
In the case of the small punch (SP) simulation the same principles of mesh refinement were carried through, here the regions of fine grid sizes were in proximity to the die radii, in addition to another zone of refinement in the free-moving region of the material disc, centred around a point that was remote from the die and the axisymmetric axis, which is an approach similar to that taken in finite element analysis (FEA) of SP creep elsewhere [33,34]
Given the increased clearance in the SP configuration versus the shear punch (ShP), bending in the subsequent simulations is expected to be more prevalent than pure shear, bending is permitted in the ShP setup

Summary

Introduction

Ical characterisation of any novel material at the development stage can be an expensive activity when accounting for the relatively large volume of material required and likely restricted material availability. Preliminary investigations into replicating fatigue damage on a SP disc has been conducted by the authors [10], where the force (F) is applied in a cyclic manner until the disc is deemed to have failed In each of these test arrangements, the compressive loading occurs as the punch tip impacts on the disc sample, promoting a small stage of elastic deformation before leading to the most dominant stage of damage where the membrane around the punch tip begins to stretch. This behaviour is in contrast to the stress state witnessed in more conventional test arrangements, where the specimen elongates under an applied uniaxial tensile force until failure. The most robust correlation was found when estimating rUTS with

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Conclusion