The development of a novel small ring specimen tensile testing technique

J Kazakeviciute,C.J Hyde,J.P Rouse

doi:10.5334/uproc.29

Abstract

The use of small specimens in routine testing would reduce resource requirements, however, limitations exist due to concerns over size effects, manufacturing difficulties, uncertainties related to the application of representative loading conditions, and complex interpretation procedures of non-standard data. Due to these limitations, small specimen testing techniques have been mostly applied for ranking exercises and to determine approximate or simple material parameters such as Young’s modulus, creep minimum strain rate and fracture toughness. The small ring method is a novel, high sensitivity small specimen technique for creep testing and has been extended in the present work for the determination of tensile material properties. Wrought aluminium alloy 7175-T7153 was tested at room temperature at 5 different loading rates. Finite element analysis was completed to evaluate the equivalent gauge section and equivalent gauge length in order to compare uniaxial tensile testing results and small ring specimen tensile testing results. An analytical solution has also been derived in order to validate the finite element analysis. It was discovered that the finite element analysis model was suitable, validated by both experimental results and analytical solution as well as that small ring specimens can be used to acquire same stress/strain data as uniaxial specimens.

Highlights

Small specimen testing is a developing field as small specimens are used in situations where not enough material is available for repeat testing, such as when developing a new material, or if testing facilities are too small for full size specimens, such as when effects of irradiation are being investigated
The main conclusion was that for this aluminium alloy at room temperature and a wide range of loading rates, small ring specimens are suitable for tensile testing
The higher strain was selected for the material model because the small ring experiences large strains during tensile testing, so representing large strains is important

Summary

Introduction

Small specimen testing is a developing field as small specimens are used in situations where not enough material is available for repeat testing, such as when developing a new material, or if testing facilities are too small for full size specimens, such as when effects of irradiation are being investigated. In general there are two main types of small specimens used for tensile testing – small punch specimen and miniaturized standard specimen. Miniaturized standard specimens vary in size from 0.5mm x 0.3mm x 0.3mm gauge section [8] to rather large but still smaller than standard. Their data is easier to understand, but they are small and difficult to handle when inserting into a testing machine and ensuring suitable alignment. It was developed to obtain creep strain data and had several advantages over alternative methods, such as having a long equivalent gauge length, being self-aligning and being simple to manufacture. The main conclusion was that for this aluminium alloy at room temperature and a wide range of loading rates, small ring specimens are suitable for tensile testing

Materials and Methods

Discussion and Conclusions