Testing device stretches elastic materials biaxially over large deformation ranges and varies strain ratios in two perpendicular directions. The device is used in conjunction with a tensile testing machine, which holds the specimen and permits control over the direction and magnitude of the stresses applied

Becker, G. W.

English

NASA Technical Reports Server

June 1965	 Brief 65-10189 
NASA TECH BRIEF 
NASA Tech Briefs are issued by the Technology Utilization Division to summarize specific 
technical innovations derived from the space program. Copies are available to the public from 
the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia, 22151. 
Testing Device Subjects Elastic Materials to Biaxial Deformations 
Vertical Load Cell
Fined 
Coupling Blade 
Extension Jaw	 Horizontal 
Load Cell 
0	 V_ ^-Ili 
Limit Switch 
f1 
Angle Plate 
Indexing Screws
Cathetometer Target 
c' Specimen 
0 Is 
52	 Gu ide Beam 
Indexing Holes 
Fixed Jaw 
A-Fixed Joint	
'-... Moveable Crosshead On 
B-Sliding Joint	 Tensile lestiny Mai.Iiine 
The problem: To provide a testing device capable	 apparatus incorporates a moveable guide beam assem-
of stretching elastic materials biaxially over large de-
	
bly supported on two angle plates. The guide beams 
formation ranges and with varying strain ratios in two
	
are rigidly attached at points A and are free to slide at 
perpendicular directions,	 points B. Multiple index holes are provided in the 
angle plates and allow for reorientation of the beam 
The solution: An apparatus, used in conjunction
	
assembly. Thus, by selecting the proper set of index 
with a tensile testing machine, which holds the speci-
	 holes for attachment, a force of predetermined direc- 
men and permits control over the direction and magni-
	 tion and magnitude can be applied to the specimen. 
tude of the stresses applied to it in biaxial directions.
	 Commercial load cells are attached to the extension 
How it's done: The complete apparatus is shown	 jaw to measure the force components in the horizontal 
in the sketch as it is mounted in a test machine. The 	 and vertical directions. The specimen is held within the 
(continued overleaf) 
This document was prepared under the sponsorship of the National
	 this document, or that the use of any information, apparatus, method, 
Aeronautics and Space Administration. Neither the United States Govern-
	 or process disclosed in this document may not infringe privately-owned 
ment, nor NASA, nor any person acting on behalf of NASA: A. Makes
	 rights; or B. Assumes any liabilities with respect to the use of, or for 
any warranty or representation, express or implied, with respect to the
	 damages resulting from the use of, any information, apparatus, method, 
accuracy, completeness, or usefulness of the information contained in
	 or process disclosed in this document.
https://ntrs.nasa.gov/search.jsp?R=19650000187 2020-03-11T17:24:22+00:00Z
guide beam assembly by hooks inserted in reinforced 
eyelets in the specimen body. A double circle target 
with cross lines is printed on the specimen for meas-
urement of the deformations with a cathetometer. 
As the moveable crosshead of the machine moves 
downward the guide bar assembly expands and 
stretches the elastic specimen in the predetermined 
manner. The forces fi and f2 applied to the specimen 
can be calculated from the output of the load cells and 
the system geometry. The stress/strain relationships 
can be quickly determined from these forces and the 
cathetometer readings for any elastomer sample under 
various biaxial loading arrangements. 
Notes: 
1. The testing device provides a maximum deforma-
tion of 270% along both perpendicular axes. For 
convenience and safety, limit switches can be
mounted on the guide bars to stop the machine 
drive motor in the maximum travel position. 
2. The direction and ratio of stresses can be varied 
over a wide range so that biaxial tensions with dif-
ferent strain ratios in the range from 0 to I can be 
obtained. 
3. Inquiries concerning this innovation may be di-
rected to: 
Technology Utilization Officer 
Jet Propulsion Laboratory 
4800 Oak Grove Drive 
Pasadena, California 91103 
Reference: B65-10189 
Patent status: NASA encourages commercial use 
of this innovation. No patent action is contemplated. 
Source: Dr. Gerhard W. Becker 
(JPL-616) 
Brief 65-10189	 Categories No. 03 and 05


Testing device subjects elastic materials to biaxial deformations

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