Shock wave effects and metallurgical parameters Page: 3 of 20
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Shock Wave Effects and Metallurgical Parameters
K. P. Staudhaimner, Materials Science and Technology Division, Los Alamos,
New Mexico, USA
Introduction
The metallurgical effects associated with dynamic loading were first de-
scribed by Reinhart and Pearson (1). The first systematic investigation of
the substructural changes induced by the passage of shock waves is described
by C. Smith (2). During the past three decades, the number of publications
has in essence exponentially continued, with now, one, two, or more major
shock conferences per year. The earlier work in shock loading consisted
primarily of studies devoted to the determination of residual structures,
substructures, and mechanical properties on materials having reasonable
ductilities, i.e., metals and alloys. Concommitant to these studies was the
realization that shock wave parameters do effect the substructure and
associated mechanical properties. Largely, this interdependence of shock
wave and metallurgical parameters arose from the obvious and significant
disagreements among investigators, and have been attributed to variations in
experimentation and ill defined pre/post shock conditions of both the shock
physics and metallurgical characterization, some of which confusion still
exists to date. Consequently, a fundamental understanding has been diffi-
cult. Recently, we have found that residual microstructures are not only
significant to the shock physics, but that many metallurgical parameters are
interdependent with one another.
This paper will focus on the metallurgical features produced by the passage
of shock waves in metals. The microstructural changes thus produced ard
their attendant effects on physical properties, primarily the mechanical
properties discussed here, have been more eminently investigated in the past
decades (3-10). It has been shown that dislocations, dislocation cells,
planar dislocation arrays, stacking faults, twins, twin-faults and point
defects, all contribute specifically or in many instances concommitantly in
metal-alloy systems to residual shock strengthening. These shock induced
microstructures are for the most part governed by the stacking fault free
energy. Stacking fault free energies largely control the movement and
subsequent arrangement of dislocations and contribute to the production of
other crystal defects or phase changes (11). High stacking fault free
energy metals and alloys such as nickel are characterized by dislocation
cell structures; while low staking fault free energy metals and alloys such
as 304 stainless steel (in fcc structures) are characterized by planar
dislocation arrays, stacking faults and twins. These parameters have been
identified, and their effects have been documented (7, 9). Consequently,
affecting the residual microstructure, these parameters also affect the
residual mechanical properties. Of significant ;mportance, and becoming
more visible in shock experimentation, particularly in light of the increase
in very high pressure work, is the contribution of strain to the overall
residual properties. While strain (deformation) effects were known for some
time, elimination of this strain was sought via appropriate momentum trap-
ping. However, as no material is a perfect metallurgical system, complete
elimination was not and is not yet possible. At best a minimization of this
strain can be achieved. Fortuitously, at low pressures (i.e., 25 GPa for
most metals) this associated strain was indeed considered to be negligible.
Nonetheless, for higher pressure improperly momentum trapped experiments,AL A VfIET0I0IITM1n Tlh mi nnnuM&. - ...r.......
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Staudhammer, K.P. Shock wave effects and metallurgical parameters, article, May 18, 1987; New Mexico. (https://digital.library.unt.edu/ark:/67531/metadc1212660/m1/3/: accessed June 3, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.