A History of Research and a Review of Recent Developments

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Introduction
The most famous of the early contributors to this field was Jean Victor
Poncelet, an illustrious product of the French Ecole Polytechnique system,
who was born at Metz in 1788. Part of his career was spent as a military
engineer in Napoleon’s Army, and part as an expert in engineering mechanics
in the arsenal in Metz. He made outstanding contributions to the fields of
geometry, structural dynamics, and engineering statics. He is said to have
introduced the effect of shearing force into the calculation of beam deflection.
His influence on the subsequent development of structural analysis was
profound, and among his most far-reaching research was the study of
penetration. He saw that the kinetic energy of penetrators, proportional to
the square of the velocity, was a key ingredient of the equation, and that the
flow of soils or metals around the body of the penetrator could not be ignored.
There are two aspects of penetration mechanics relevant to our subject.
The first of these is the penetration of an explosive-carrying missile into the
target medium before the explosion occurs. The second is the penetration of
structures by high-velocity fragments of the metallic casings of bombs and
shells after the explosion has taken place at a short distance from the target.
The first aspect results in internal shock waves in the material of the target,
the second results in high-velocity impact damage.
High-velocity impact from the steel fragments of shell casings began to be
investigated after the advent of the artillery shell, and much work was in
progress in the nineteenth century. However, the penetration of warheads and
explosive-carrying devices did not become widely researched until the beginnings
of aerial bombing in the twentieth century. The influence of penetrator shape
on the depth of penetration, and the relevance of the strength of the penetrated
material was examined, and at the end of the Second World War there were
several empirical penetration formulae available. Most of these assumed that
the penetrator did not deform on contact with the medium. The problem of a
deforming plastic penetrator seems to have been considered firstly by G.I.Taylor,
but in recent times there has been an increase in research in this area resulting
from the development of three-dimensional finite element programs capable
of dealing with dynamic forces and massive plastic deformation.
Once the fundamentals of deformation, blast loading, structural response
and penetration have been examined the problems facing the structural designer
in many fields can be addressed. The first of these is the effect of local explosions,
where up to one or two tonnes of explosive is detonated on or near structures.
The targets might be aircraft structures, naval structures, underwater structures,
protective structures built on the surface of the ground, or protective structures
built below ground. We owe much to the research and testing aimed at the
evaluation of structural response to ‘conventional’ or ‘non-nuclear’ bombs
carried out in the USA, Great Britain and Germany during the past 30 years.
The leading American establishment in this work has been the US Army
Waterways Experiment Station at Vicksburg, Mississippi. Their test facilities
have been constructed at great expense, and have been used to examine