A flexible fastener permits thermal expansion of model skin sections which are rigidly attached to supporting structures in wind tunnel tests. The device uses a modified ball joint contact between the fastener and a skin section

Crumpler, W. B.

English

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June 1964	 Brief 64-10145 
NASA TECH BRIEF 
This NASA Tech Brief is issued by the Technology Utilization Division to acquaint industry 
with the technical content of an innovation derived from the NASA space program. 
Flexible Fastener Allows Thermal Expansion 
The problem: Provide flexible yet secure attach-
ment of wind-tunnel research model skin sections. 
Thermal expansion of skin sections rigidly fastened 
to supporting structures produces stress concentra-
tions which often cause the skin to rupture or buckle. 
The solution: A flexible fastener that employs a 
modified ball-joint contact between the fastener and a 
skin section. 
How it's done: The contact surfaces between the 
fastener head and skin section are mated to form a 
modified ball-joint. This allows the skin section to
move laterally without creating the large bending 
moments which would occur if the mating surfaces 
were flat. The threaded end of the fastener shank is 
secured to a spring-held nut housed in a rigid mount. 
A rectangular protrusion from the nut into a fixed 
slot prevents rotation during installation; however, it 
does not prevent wobble or vertical movement after 
installation. 
Notes: 
1. Although this fastener was designed to relieve 
thermally induced stresses, it may be used to 
(continued overleal) 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States Govern-
ment, nor NASA, nor any person actin g on behalf of NASA: A. Makes 
any warranty or representation, express or implied, with respect to the 
accuracy, completeness, or usefulness of the information contained in
this document, or that the use of any information, apparatus, method, 
or process disclosed in this document may not infrin g e privately-owned 
rights; or B. Assumes any liabilities with respect to the use of, or for 
damag es resulting from the use of, any information, apparatus, method, 
or process disclosed in this document.
https://ntrs.nasa.gov/search.jsp?R=19640000045 2020-03-11T17:04:55+00:00Z
connect two bodies wherein a provision for slight 
relative motion is necessary. 
For further information about this innovation 
inquiries may be directed to: 
Technology Utilization Officer 
Langley Research Center 
Langley Station 
Hampton, Virginia 23365 
Reference: B64-10145
Patent status: NASA encourages the immediate 
commercial use of this invention. It is owned by 
NASA and inquiries about obtaining royalty-free
	
40 
rights for its commercial use may be made to NASA 
Headquarters, Washington, D.C. 20546. 
Source: Weymouth B. Crumpler 
(Langley-40) 
Brief 64-10145


Flexible fastener allows thermal expansion

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