Simplified method determines yield strength due to heat treat, irradiation or mechanical treatment. Each specimen in a group of specimens is tested for yield stress point, subjected to heat treat or irradiation, and retested for new yield stress point which is a measure of change in material

Dixon, C. E.

English

NASA Technical Reports Server

August 1967	 Brief 67-10266 
AEC-NASA TECH BRIEF 
X TES
AEC-NASA Tech Briefs describe innovations resulting from the research and development program 
of the U.S. AEC or from AEC-NASA interagency efforts. They are issued to encourage commercial 
application. Tech Briefs are published by NASA and may be purchased, at 15 cents each, from 
the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Simplified Method Measures Changes in Tensile Yield Strength Using 
Least Number of Specimens
D	 — — — 
Change Due To ue 
Heat Treat Or 
ation 
Stress	 Yield Stress	
Irradi
- -
 ___0 C 
B	 _.-- 
(LB/n 2) -
Unload	 Reload 
/	 (0.2% 
Offset) 
/
Heat Treat or Irradiate 
Strain (In/In) 
The problem: 
In determining the change in yield strength due to 
heat treat, irradiation or mechanical treatment, it is 
common practice to use separate groups of specimens 
of each material for each test. For example, several 
specimens of each material are selected for testing 
before any treatment is made and separate specimens 
of each material are selected for testing after each 
treatment or combination of treatments is made. This
method requires many specimens and is costly. In a 
recent testing situation, because only a few samples 
were available, another method had to be imple-
mented. 
The solution: 
Within a group of specimens start the stress—strain 
test of each specimen. After the yield stress point has 
been established, unload the specimen and apply the 
heat treat or irradiation. Reload the specimen and 
-	 (continued overleaf) 
-S
This document was prepared under the sponsorship of the Atomic 
Energy Commission and/or the National Aeronautics and Space 
Administration. Neither the United States Government nor any per-
son acting on behalf of the United States Government assumes any
liability resulting from the use of the information contained in this 
document, or warrants that the use of any information, apparatus, 
method, or process disclosed in this document may not infringe pri-
vately owned rights.
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establish the new yield stress point which is a measure 
of the change in material due to heat treat or irradia-
tion. 
How it's done: 
A group of specimens is tested in the following 
manner (the larger the group, the greater the confi-
dence in the results): With a specimen, start the 
stress-strain test and establish each point on the curve 
up to its yield stress point (point A on the curve). At 
some point beyond the yield stress point (point B) but 
much less than the predicted ultimate stress point 
(point C) unload the specimen and expose it to the 
desired heat treat or irradiation. Reload the sjecimen 
and establish the new yield stress point in the same 
manner as before (point D). 
It has been found that the change in tensile yield 
stress, as shown, can be measured accurately. Other 
tensile properties' can still be obtained with the same 
specimen. Recovery studies of induced changes in 
yield strength can be made by unloading just after 
point D, annealing, and repeating the measurements 
at the regular testing temperatur ç . For a highly ductile 
material, possibly 4 or 5 annealing temperatures could 
be investigated with the same specimen.
Notes: 
I. Formerly it was required to have several groups of 
specimens for each material being tested. With this 
method of testing, it is normally required to have 
only one group of specimens. This provided for a 
marked decrease in cost of specimens from 50% 
upward, depending upon the number of different 
conditions under which the material is to be tested. 
2. Inquiries concerning this innovation may be di-
rected to:
AEC-NASA Space Nuclear Propulsion 
Office 
U.S. Atomic Energy Commission 
Washington, D.C. 20545 
Reference: B67-10266 
Patent status: 
No patent action is contemplated by AEC or 
NASA.
Source: C. E. Dixon
of the Aerojet-General Corp.

under contract to

Space Nuclear Propulsion Office
(NUC- 10075) 
Brief 67-10266	 Category 03


Simplified method measures changes in tensile yield strength using least number of specimens

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