Investigation of the tensile strength dependability on the characteristic time over which a pressure pulse is applied to a metal workpiece shows that the mechanical properties of these materials are functions of the rate at which the material is undergoing strain. These results and techniques are used in magnetomotive metal forming

Furth, H. P.

Holt, D. R.

Jatmuz, P. J.

Mehra, R. C.

Waniek, R. W.

English

NASA Technical Reports Server

June 1968
	 Brief 68-10186 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Magnetic Forming Studies 
The use of transient high magnetic-field devices has 
made possible the generation of very large accurately 
known stresses in metals. A basic problem in calculat-
ing with some precision the deformation resulting in a 
metal workpiece by the application of any given force 
profile is the lack of data on the effective tensile 
strength and its dependence on the pressure pulse 
time. Performance tests conducted on a variety of 
magnetic hammer configurations markedly demon-
strated that the deformation of workpieces increases 
much more rapidly with the duration of the pressure 
pulse than can be explained by a theory based on a 
unique, time-independent tensile strength. The plaus-
ible inference is that the tensile strength depends on 
the characteristic time over which the pressure pulse is 
applied to the metal. A series of basic experiments 
was conducted to investigate in detail this inference. 
These investigations cover two distinct configura-
tions. In the first geometry, the samples are straight 
wires which are stressed uniaxially by magnetically 
accelerated anvils. In the second geometry, the 
samples are wire hoops which are stressed radially out-
ward by a transiently induced Lorentz force. The first 
experiment is aimed at measuring stress—strain rela-
tionship in a way analogous to the classical Hooke 
method. The difference is that the new approach is 
based on elastodynamics rather than elastostatics. In 
the second experiment the objective is to define the 
elastodynamic behavior of materials which are 
stressed by purely electromagnetic forces as contrasted 
to the mechanical forces used in the first geometry.
The materials tested in the experiments include 
copper, aluminum alloys 1199-H 14, EC-0, 5056-H38, 
6061-0,6061-16, 2319, and a carbon steel. The results 
show that the mechanical properties (dynamic yield 
strength and ultimate tensile strength) of these materials 
are functions of the rate at which the material is under-
going strain. These results and analytical techniques 
applied in the investigation are of immediate useful-
ness in magnetomotive metal forming and are also 
generally applicable to a number of pertinent situa- 
tions encountered in other high energy-rate forming 
methods. 
Notes: 
I. A magnetic (magnetomotive) hammer developed 
for removing weld distortions from aluminum 
alloy tanks is described in Tech Brief 65-10342. 
2. Complete details concerning this investigation may 
be directed to: 
Technology Utilization Officer 
Marshall Space Flight Center 
Huntsville, Alabama 35812 
Reference: B68-10186 
Patent status: 
No patent action is contemplated by NASA. 
Source: R. W. Waniek, H. P. Furth, 
P. J. Jatmuz, R. C. Mehra, 
D. R. Holt, E. E. Julian, 
and K. Y. WuofAdvanced Kinetics 
under contract to 
Marshall Space Flight Center 
(M FS- l4217) 
Category 02 
This document was prepared under the sponsorship of the National 	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States	 will be free from privately owned rights.
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Magnetic forming studies

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