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Abstract

The principle aim of the research reported in this thesis is to develop simple analytical techniques which can be confidently used to predict the amount and type of permanent damage to plates subject to projectile impact. In addition, it is intended to assess the validity of the scale similarity laws which are applicable to impact generated structural response involving large plastic deformations.

Existing literature involving analytical, experimental and numerical treatment of impact phenomena is reviewed. The need for the work conducted herein arises because, in general, simple design formulae for structural damage estimation do not exist. Furthermore, when structural testing is deemed necessary, it is uncertain whether scale models will faithfully represent prototype behaviour in situations involving structural impact.

The analytical procedures proposed are based on a rigid plastic material idealisation and, in addition, rely on many other assumptions. The implications of the assumptions inherent in the techniques are critically examined and discussed in detail. Simple relationships are proposed for both quasi-static and dynamic target response. Furthermore, square target panels are analysed as 'equivalent circular plates' to enable axisymmetric treatment of the problem.

An experimental programme involving fifty-nine tests on isotropic mild steel plates is reported. An experimental rig was designed and built both for the purposes of this research and to provide a general impact test facility for future use. Two test series were conducted: the first provided data to validate analytical methods and the second was specifically designed to validate scale similarity laws. The special instrumentation problems associated with tests involving impact are discussed.

The experimental results are compared with the various analytical techniques proposed. In addition, a small number of case studies are presented to demonstrte the capabilities and versatility of the proposed methods.

It is concluded that approximate rigid plastic methods can provide good estimates of target damage from projectile impact loading. The particular analytical approach necessary for a given problem is dependent on the initial problem parameters. A wide range of problems can be solved, however, with careful use of the proposed methods.

The use of small scale models to predict prototype behaviour is valid for the work reported in this thesis. It is concluded, however, that impact events involving tearing, fracture or buckling in response are less likely to scale successfully and further work is suggested.

The validity of the proposed analytical methods is limited to the range of parameters studied epxerimentally. There is no reason to suppose, however, that use of the techniques outside this range will be unsuccessful and further experimental work is suggested to support this conjecture. The main limitation of the proposed methods is the lack of a criterion defining failure. For example, in one test the target was perforated completely and this was not predicted by the theoretical techniques used.

Although there exist limitations with simple analytical design methods, the various techniques developed herein have predicted good results for a wide range of problem parameters.

Publication Type:	Thesis (Doctoral)
Subjects:	T Technology > T Technology (General) T Technology > TA Engineering (General). Civil engineering (General)
Departments:	School of Science & Technology > Department of Engineering School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses

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