Tensile-strength testing apparatus employs a capillary bundle through which a noncompressible fluid is extruded and a quick-release valve system. This apparatus applies the test loads at relatively constant very high strain rates with minimal shock and vibration to the tensile specimen and apparatus

Cotrill, H. E., Jr.

Mac Glashan, W. F., Jr.

English

NASA Technical Reports Server

February 1966	 Brief 66-10063 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U. S. space 
program and to encourage their commercial application. Copies are available to the public from 
the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Tensile-Strength Apparatus Applies High Strain-Rate

Loading with Minimum Shock 
Quick-Dump 
Capillary 
Overtravel Sprinç 
Strain-Generating 
Assembly	 I-
Spring C 
Loading C 
Strain Wall 
Potentiometer
 
Piston Rod 
ter llhi 
Arm 
Thermal Pane 
Window 
Potentiometer 
The problem: 
To design an apparatus for tensile-strength testing 
of materials that will apply the test loads at relatively 
constant very high strain rates (up to 20,000 inches 
per minute) with minimal shock and vibration to the 
tensile specimen and apparatus. 
The solution: 
An apparatus that incorporates a capillary bundle 
through which a noncompressible fluid (e.g., oil) is 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
extruded and a quick-release valve system. 
How it's done: 
The apparatus consists of two primary assemblies 
(separated by a strain wall), the strain generator, and 
the specimen container which is enclosed in a tem-
perature-control box. The specimen is connected 
directly to the strain generator through the piston 
rod. 
To ready the system for a test, oil is pumped under 
(continued overleaf) 
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
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the quick-dump valve to drive the piston to its lower 
position. One of the nitrogen lines is opened to pres-
surize the underside of this piston, and a second 
nitrogen line leading to the underside of the diaphragm 
in the oil sump is opened. The specimen is attached 
to the holding devices in the strain box by opening 
the door in the temperature-control box and reaching 
in through the window in the side wall of the strain 
box. When the specimen is in place, the door and 
window are closed and the temperature is regulated 
to the desired degree. The preparations are completed 
by adjusting an orifice selector (not illustrated) as-
sociated with the valve assembly to provide the de-
sired strain rate. 
The test is begun by opening the release valve 
between the pressurized oil sump and the quick-dump 
valve. This action opens a passage for the oil trapped 
below the quick-dump valve. The nitrogen pressure, 
acting on the underside of the piston, forces the 
oil through the capillary bundle and constrains the 
piston to move upward at a constant rate, thus apply-
ing a constant tensile strain rate to the specimen. An 
overtravel spring in the spring chamber stops the 
piston at the top of its travel.
Notes: 
1. The apparatus eliminates shock and vibration in 
high strain-rate tensile testing. It is capable of 
generating a constant strain rate between 20 and 
20,000 inches per second: 
. Inquiries concerning this innovation may be di-
rected to: 
Technology Utilization Officer 
Jet Propulsion Laboratory 
4800 Oak Grove Drive 
Pasadena, California, 91103 
Reference: B66-10063 
Patent status: 
No patent action is contemplated by NASA. 
Source: Harry E. Cotrill, Jr. and 
W. F. MacGlashan, Jr. 
under a Department of the Army contract to 
Jet Propulsion Laboratory 
DA-04-495-Ord 18 
(JPL-28 & 29)
. 
. 
Brief 66-10063	 Category 05


Tensile-strength apparatus applies high strain-rate loading with minimum shock

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