On the Development of a Release Mechanism for a Split Hopkinson Tension and Compression Bar.

Georg Baumann,Dominik Niederkofler,Christian Ellersdorfer,Florian Feist

doi:10.3390/ma14247609

Abstract

Split Hopkinson bars are used for the dynamic mechanical characterisation of materials under high strain rates. Many of these test benches are designed in such a way that they can either be used for compressive or tensile loading. The goal of the present work is to develop a release mechanism for an elastically pre-stressed Split Hopkinson bar that can be universally used for tensile or compressive loading. The paper describes the design and dimensioning of the release mechanism, including the brittle failing wear parts from ultra-high strength steel. Additionally, a numerical study on the effect of the time-to-full-release on the pulse-shape and pulse-rising time was conducted. The results of the analytical dimensioning approaches for the release mechanism, including the wear parts, were validated against experimental tests. It can be demonstrated that the designed release concept leads to sufficiently short and reproducible pulse rising times of roughly 0.11 ms to 0.21 ms, depending on the pre-loading level for both the tension and compression wave. According to literature, the usual pulse rising times can range from 0.01 ms to 0.35 ms, which leads to the conclusion that a good average pulse rising time was achieved with the present release system.

Highlights

Engineering disciplines, such as mechanical or civil engineering, strive to design structures or components that are as ductile as possible
There are applications in which an abrupt, brittle failure of a component is tolerated, but it is even desired. One such application is the Split Hopkinson test bench or, more precisely, its release mechanism, which is examined in more detail in the course of this article
A Split Hopkinson test bench is a facility for the dynamic mechanical characterisation of materials at high strain rates ranging from around 100 s−1 up to 10,000 s−1

Summary

Introduction

Engineering disciplines, such as mechanical or civil engineering, strive to design structures or components that are as ductile as possible. The reason for this is to prevent sudden catastrophic, brittle failure. There are applications in which an abrupt, brittle failure of a component is tolerated, but it is even desired One such application is the Split Hopkinson test bench or, more precisely, its release mechanism, which is examined in more detail in the course of this article. The test bench consists of several long bars between which the test specimen is positioned (see Church et al [3]).

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Conclusion