The high strain-rate compressive behaviour of beta-brass single crystals

Abstract

The work described in this thesis represents an investigation undertaken with the two-fold purpose of (a) establishing the apparatus and techniques necessary for carrying out investigations into the response of metals to dynamic loading, and (b) examining the response of beta-brass single crystals to dynamic loading. The first part of the investigation required the development of basic apparatus for investigations of the type planned. This apparatus included a dynamic compression testing machine and apparatus for the production and preparation of metal single crystals. The second part of the investigation required the assessing of the existing knowledge of the static and dynamic properties of beta-brass and the planning of a programme aimed at contributing to this knowledge. A review of the existing literature is presented and a programme of tests is outlined. As a result of the investigation the following conclusions were drawn concerning the static and dynamic properties of beta-brass single crystals. The dynamic upper and lower yield stresses were found to be strain-rate sensitive and the upper yield stress increased by up to 4.5 times the static yield stress. The dynamic upper and lower yield stresses were found to be temperature dependent and to show the same temperature dependence as the static yield stress. Both increasing strain-rate and decreasing temperature raised the yield stress. The dynamically deformed material showed large yield drops whereas the statically deformed material did not. Both the static and dynamic work hardening behaviour were found to be orientation dependent. The rate of work hardening for the static tests increased with decreasing temperature whereas that for the dynamic tests did not. The dynamic work hardening behaviour was insensitive to strain-rate. At strains greater than 4 per cent the dynamically deformed material was found to be softer than that statically deformed the same amount. Both the statically and dynamically tested material deformed by slip and the formation of deformation bands. Twinning was not observed. Jerky flow was found to be composition and temperature sensitive.