Towards Standardising SHPB Testing - A Round Robin Exercise

Reuben Govender,Muhammad Kariem,Guoxing Lu,Rafael Santiago,Gerald Nurick,Dong Ruan,Marcilio Alves,Genevieve Langdon,Dong Wei Shu,E Buzaud,H Couque,E Cadoni,A Cosculluela

doi:10.1051/epjconf/201818302027

Abstract

The Split Hopkinson Pressure Bar (SHPB) test, while widely utilised for high strain rate tests, has yet to be standardised. As an exploratory step towards developing a standard test method or protocol, a Round Robin test series has been conducted between four institutions: (i) Swinburne University of Technology, Australia (ii) University of São Paulo, Brazil, (iii) University of Cape Town, South African and (iv) Nanyang Technological University, Singapore. Each institution prepared specimens from a metallic material, and provided batches of specimens from their chosen material to the other institutions. The materials utilised in this round of testing were commercially pure copper and aluminium, magnesium alloy and stainless steel (316 grade). The intent of the first exercise is to establish the consistency of SHPB test results on nominally identical specimens at comparable elevated strain rates, conducted by different laboratories following notionally similar test procedures with some freedom in data processing. This paper presents and compares the results of the first batch of tests for copper, identifying variations between results from different laboratories. The variation between different laboratories’ results for copper is suffciently small that there is confidence in the potential to develop a draft standard in future.

Highlights

The Split Hopkinson Pressure Bar (SHPB) [1] or Kolsky Bar [2] test is a well established means of investigating mechanical response of a material to high strain rate (≈ 102 to 104 s−1) loading
To the best of the authors’ knowledge, no data has been published showing that SHPB testing conducted at different laboratories, on specimens of the same provenance, produce consistent stress-strain results to within an acceptable tolerance
Obtaining specimen stressstrain from an SHPB experiment requires several decisions about how to process the captured incident εI, reflected εR and transmitted εT strain waves

Summary

Introduction

The Split Hopkinson Pressure Bar (SHPB) [1] or Kolsky Bar [2] test is a well established means of investigating mechanical response of a material to high strain rate (≈ 102 to 104 s−1) loading. The fundamental principles and guidelines for setting up, conducting and analysing a SHPB experiment are well described by Gray III [3], and Chen and Song [4]. Conducting a successful SHPB experiment requires decisions on a large range of parameters (e.g. bar materials, length, diameter, specimen dimensions etc) and post-processing methods (1,2 or 3 wave analysis, dispersive or non-dispersive wave propagation etc). To the best of the authors’ knowledge, no data has been published showing that SHPB testing conducted at different laboratories, on specimens of the same provenance, produce consistent stress-strain results to within an acceptable tolerance. This article documents a Round Robin test series, which sought to establish whether specimens of the same material, tested in compression at SHPB facilities at different institutions, would produce similar stress-strain results. The intent is to ascertain how much the raw experimental data varies, given different physical SHPB set

Specimen Details

Physical SHPB Details

Instrumentation details

Data Processing

Concluding Remarks