Proper installation techniques are described and reliable torque-tension values are presented on joint preload /or clamp load/ properties of structural threaded fasteners

Brenner, H. S.

English

NASA Technical Reports Server

December 1971	 Brief 71-10531 
NASA TECH BRIEF 
Marshall Space Flight Center
	
_dV 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a &ubscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the. Tech Brief program may 
be directed to the Technology. Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Joint Preload Properties of Structural Threaded Fasteners 
.
Update information is now available on the joint 
preload (or clamp load) properties of structural 
threaded fasteners. Proper installation techniques are 
described and reliable torque-tension values are pre-
sented for nut and bolt combinations made from 
AISI 8740 steel, 6A14V titanium alloy, A286 CRES, 
HI! steel, AMS6304 steel, AMS6487 steel, 5A1-2.5Sn 
(ELI) titanium alloy, and 2024-T4 aluminum alloy. 
In addition, the effects of various parameters on 
torque tension properties are examined in detail, using 
bolts fabricated from the first two alloys in both 
tension- and shear-type wrenching head configura-
tions. 
One important finding is that previously tabulated 
torque values intended to induce desired clamp loads 
are valid only for the initial installation. Repeated 
mating of the same nut and bolt is accompanied by a 
gradual decrease in induced load, with the percentage 
loss reaching as high as 50% after 15 installation cycles. 
Clamp load is also affected by such variables as hole 
size, surface finish, and degree of lubrication, as well 
as nut and washer designs. It is particularly essential 
to use compatible washers with high-strength bolts.
For testing purposes, clamp loads up to 90% of bolt 
yield strength have been employed. However, in prac-
tical structural assemblies, the use of a smaller per-
centage clamp load should be considered. 
Note: 
The following documentation may be obtained 
from:
National Technical Information Service 
Springfield, Virginia 22151 
Single document price $3.00 
(or microfiche $0.95) 
Reference: 
NASA CR- 103179 (N71-26568), Development 
of Technology for Installation of Mechanical 
Fasteners 
Patent status: 
No patent action is contemplated by NASA. 
Source: H. S. Brenner of

Almay Research and Testing Corp.

under contract to

Marshall Space Flight Center

(MFS-2 1453) 
Category 08 
This documeft 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 ownedrights.
https://ntrs.nasa.gov/search.jsp?R=19710000522 2020-03-17T02:26:55+00:00Z


Joint preload properties of structural threaded fasteners

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