Discovery of unlocked contacts in Deutsch Block terminal junctions in Solid Rocket Booster flight hardware prompted an investigation into pull test techniques to help insure against possible failures. Internal frictional forces between socket and pin and between wire and grommet were examined. Pull test force must be greater than internal friction yet less than the crimp strength of the pin or socket. For this reason, a 100 percent accurate test is impossible. Test tools were evaluated. Available tools are adequate for pull testing

Smith, J. L.

English

NASA Technical Reports Server

General Disclaimer 
One or more of the Following Statements may affect this Document 
 
 This document has been reproduced from the best copy furnished by the 
organizational source. It is being released in the interest of making available as 
much information as possible. 
 
 This document may contain data, which exceeds the sheet parameters. It was 
furnished in this condition by the organizational source and is the best copy 
available. 
 
 This document may contain tone-on-tone or color graphs, charts and/or pictures, 
which have been reproduced in black and white. 
 
 This document is paginated as submitted by the original source. 
 
 Portions of this document are not fully legible due to the historical nature of some 
of the material. However, it is the best reproduction available from the original 
submission. 
 
 
 
 
 
 
 
Produced by the NASA Center for Aerospace Information (CASI) 
https://ntrs.nasa.gov/search.jsp?R=19830016282 2020-03-21T04:15:53+00:00Z
(DASI-TH-82520) ANALYSIS CF FV I - 41 ST 1CCLS
AND THEIR LIMITATIONS AS AFFIIFL IC TEINTIAh
JONCTICN HLCCKS (NASA) 15 F PC A02/MF A01
CSCL 21H
G3/20
!Fe? -24553
Oaclas
03772
NASA TECHNICAL
MEMORANDUM
NASA TM 82520
ANALYSIS OF "PULL-TEST" TOOLS AND THEIR
LIMITATIONS AS APPLIED TO TERMINAL JUNCTION BLOCKS
By James L. Smith
Information and Electronics System Laboratory
^i
G
	
_
	 C - 1 1
April 1983 C, 
PIECE IV
;Tt FAtka€ E
NASA
	
^d
George C. Marshall Space Flight Center
7 w	 Marshall Space Flight Center, Alabama
NOFC - Fore '+ 190 (Rev June 1971)
-rz?^UU6d`A1 ntibAYT alrAWMABn TITI E O1199
1.	 REPORT N0. Z, GOVERNMENT ACCESSION N0. 3.	 RECIPIENT •$ CATALOG N0.IF
NASA TM -82520
+. TITLE AND SUBTITLE 6, REPORT DATE
Analysis of "Pull-Test" Tools and Their Limitations as April 1983
Applie,! to Terminal Junction Blocks 6. PERFORMING ORGANIZATION CODE
7,	 AUTHOR(S) & PERFORMING ORGANIZATION REPORT v
James Lee Smith
9.	 PERFORMING ORGANIZATION NAME AND ADDRESS 10.	 WORK UNIT NO.
George C. Marshall Space Flight Center
11,	 CONTRACT OR GRANT N0.Marshall Space Flight Center, Alabama 35812
1 , TYPE OF REPORT Q PERIOD COVERED
12.	 SPONSORING AGENCY NAME AND ADDRESS
National Aeronautics and Space Administration Technical Memorandum
Washington, D.C.  20546 14.	 SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
Prepared by Information and Electronics System Laboratory
16.	 ABSTRACT
Discovery of unlocked contacts in Deutsch Block terminal junctions in Solid Rocket
Booster flight hardware prompted an investigation into "pull-test" techniques to
help insure against possible failures. In this paper, internal frictional forces between
socket and pin and between wire and grommet were examined. Pull-test force must
be greater than internal friction yet less than the crimp strength of the pin or
socket. For this reason, a 100 percent accurate test is impossible. Test tools were
evaluated. Currently available tools are adequate for "pull-testing."
	 I
I
C
`i
i
i
17,	 KEY WORDS 16.	 DISTRIBUTION STATEMENT
Contact Retention Test
Terminal Junction Blocks Unclassified - Unlimited
"Pull-Test"
19,	 SECURI TY CLASSIF. (ot this report) 20,	 SECURITY CLASSIF. (e( this Oags ) 21,	 NO. OF PAGES 22.	 PRICE
Unclassified Unclassified 15 NTIS
11ellr C - worm 7T97 (w•ar 1969)
For sale by National Technical In(oeeation Service, Springfield. Virginia 22161
Y
TABLE OF CONTENTS
Page
INTRODUCTION ............................................................. 1
DEUTSCH BLOCK FRICTIONAL ANALYSIS ................................... 1
Procedure .............................................................. 1
Results ................................................................. 1
TOOL	 EVALUATION	 ......................................................... 6
Descriptionof	 Tools .................................................... 6
AngleVariation	 Test	 ................................................... 6
WireSlippage	 Test
	
..................................................... 8
CONCLUSIONS	 .............................................................. 10
ii
LIST OF ILLUSTRATIONS
Figure
	 Title	 Page
	
1	 Test Apparatus ....................................................
	
2
	
2	 Frictional Force in Unlocked Deutsch Blocks .......................
	
2
	
3	 Frontal View of McDonnell-Douglas Tool with Gripper Jaw Open ....
	 3
	
4	 Frontal View Gripper Jaw Closed ..................................
	 3
	
5	 Lateral View of the McDonnell-Douglas Tool ........................
	 4
,
	
6	 Lateral View of the Russtech Tool .................................
	 4
	
7	 Lateral View of the Gripper Jaw of the Russtech Tool .............. 	 5
	
8	 Frontal View of the Gripper Jaw of the Russtech Tool ............. 	 5
	
9	 Coordinate System ................................................. 	 7
	
10	 Vise Arrangement ................................................. 	 7
iii
TECHNICAL MEMORANDUM
ANALYSIS OF "PULL-TEST" TOOLS AND THEIR LIMITATIONS AS
APPLIED TO TERMINAL JUNCTION BLOCKS
INTRODUCTION
Discovery of unlocked contacts in Deutsch Block terminal junction in Solid
Rocket Booster flight hardware prompted an investigation of testing procedures
and tools. Since Deutsch Blocks have rear-access contacts, a "pull-test must be
utilized. The "pull-test" force is bounded by a minimum force (equivalent to the
friction within the pin-socket system) and a maximum force (the crimp strength of
the pin or socket upon the wire). Since the "pull-test" forces are bounded, a 100
percent accurate test is impossible. For example, some contacts might require a
"pull-test" at a higher value than crimp strength permits or at a lower value than
frictional forces permit; thus, that test will either be inaccurate or impossible to
perform. Crimp strength values were already available. Frictional forces were
determined by laboratory test. Existing tools were evaluated to determine if they
would meet test criteria. Two tools, Russtech Engineering and McDonnell-Douglas,
were evaluated by laboratory tests. The results are contained herein.
DEUTSCH BLOCK FRICTIONAL ANALYSIS
Procedure
Size 22 Deutsch Blocks were used in testing because most problems have been
encountered with that size. Twenty-two guage teflon wire was used in testing so
that maximum frctional values could be calculated for size 22 blocks. Deutsch Blocks
were modified in two ways: (1) The spring clip locking mechanism was broken to
prevent interlocking of the pin and socket; (data set one) ; and (2) a small drop of
solder was placed in the bottom of the socket to limit insertion depth and thus to
prevent interlocking (data set two). Two Deutsch Blocks, each containing ten
contacts, were used for each data set.
An Instron Stress-Strain Testing machine was used to "pull-test" the Deutsch
Blocks. The blocks were locked into a variable angle vise so that the angle of pull
could be varied between 0 and 90 deg. Thus, frictional force was determined as a
function of pull angle. Data was recorded on the chart recorder. Three pulls were
conducted at each angular setting. If a large variation within a data point occurred,
additional pulls were taken to insure accuracy. After pulling all the wires from each
Deutsch Block, the wires were reinserted at random. Two sets of data were
collected, one from the block with broken locks and one from the set with soldered
sockets (Fig. 1).
Results
The graph in Figure 2 was complied from both data sets. It is clear that from
0 to 40 deg, most of the friction occurs between the socket and pin. This portion of
the function is almost linear. From 40 to 90 deg most of the friction occurs between
FRICTIONAL FORCE IN UNLOCKED DEUTSCH BLOCKS
4OKEN SPRINGS
)LDER IN SOCKET
4
h02
O 3
NW0
cc0 2
LL
J
Q20
v 1
RE
LL
0 0
	 10	 20	 30
Of X
1	 1	 A
4l	 50	 60	 70	 ®0	 80
PULL ANGLE (DEGREES) --^
CHART
RECO-
RDER
TEST
ITEM
i
i
VISE
INS TRON
Vfil I^^ • S ^ i ^ i , ,. ^^^^
OF POOR QUAL111Y
Figure 1. Test Apparatus
Figure 2. Frictional Force in Unlocked Deutsch Blocks
2
i
09
Y
0
O RIGINAL-	 j
CF POOR
Figure 3. Frontal View of McDonnell-Douglas Tool with Gripper Jaw Open.
Figure 4. Frontal View Gipper J.iw Closed
3	 i
i
or..
OF Post
Figure 5. Lateral View of the McDonnell-Douglas Tool.
Figure 6. Lateral View of the Russtech Tool.
ORIGINAL F;.CE (S
OF POOR Q'JALRY
	 f
Figure 7. Lateral View of the Gripper Jaw of the Russtech Tool.
Figure 8. Frontal View of the Gripper Juw of the IZu.^steeh Tool.
5
the rubber grommet and the wire. The X's are the actual data points for the block
with the broken locks. The O's are the actual data points for the block with soldered
sockets. Both data sets are surprisingly close. The solid lines are averages of both
data sets, and the dotted lines approximate the continuance of each function if the
two functions were not added together.
Finally, the maximum friction occurred within a size 22 Deutsch Block with 22
gouge teflon wire was 3 '.b (the minimum "pull-test" boundary) .
TOOL EVALUATION
Description of Tools
Two tools (a prototype from Russtech Engineering and it "shop-made' tool from
McDonnell-Douglas) were considered. Figures 3 through 8 are photographs of the
tool.
The Russtech tool has a factory set release mechanism in the handle. Attached
to the handle is a set of gripper jaws. The release mechanism can be ordered at any
setting (the one evaluated was set at 3.5 io 4.5 lb). Jaw tension may be varied by a
set screw adjustment. The production model of this tool would probably have two
or three sizes of jaws. This tool uses an in-line or parallel pull. This prototype was
designed for smaller wire; but it may be used on wire as large as 12 gauge.
The McDonnell-Douglas tool is a "break-over" torque tool modified with a set
of jaws. The wire is pulled perpendicularly to the tool handle. The tool is preset to
"break" at 5.4 lb. Jaw tension may also be varied. Tension was set for larger wire
in our test.
A pull angle variation effects test and a wire slippage test were conducted. The
Instron Testing machine was used for both tests.
Angle Variation Test
The tool to be tested was locked into a variable angle vise. Twenty-two gauge
teflon wire was used for the Russtech test. Twelve gauge teflon wire was used for
the McDonnell-Douglas test. At each angular setting, the wire specimen wits pulled
until the tool tripped or the wire slipped in the gripper jaws. Three trials were
taken at each setting so that tin average value could be established. The Russtech
tool was tested with the angle varied in the parallel, perpendicular and 45 deg
planes relative to the jaw surfaces (Figs. 9 and 10).
6
XTOOL JAWS
Y
9
Z
7
Figure 9. Coordinate System
JAW
RUSSTECM TOOL IN VISE
FE VISE
JAW MCDONNELL—DOUGLAS
TOOL IN VISE
Figure 10. Vise Arranf,ement
8Testing apparr.tus limited the McDonnell-Douglas tool to parallel plane testing.
Average values are in the tables below:
Russ, ech Tool
Angle (deg) _
	 Parallel Plane	 ^ Perpendicular Plane
	 45 deg Plane
	
0	 3.9 (lbs)	 3.9 (lbs)
	 3.9 (lbs)
	
5	 4.6	 4.5	 4.7
	
10	 5.3	 5.4	 5.7 - slips
	
12	 112	 5.7 - slips	 5.7 - slips	 --
	
15	 -	 -	 -
McDonnell-Douglas Tool
	
An le (de )	 Parallel Plane (lbs)
0 5.4
5 5.4
10 5.4
12	 1/2 5.4
15 5.4
25 5.4
35 5.5
45 6.5
Wire Slippage Test
Wire specimens of different sizes and insulation varieties were pull tested, using
the Instron, to determine at what pull strength wire slippage occurred in the gripper
jaws. Three trials were used to determine an average value. The pull was direct,
parallel to jaws on both tools. On the Russtech tool one set (3 trials) of data wits
taken with minimum jaw tension and one with maximum jaw tension. One set of data
was taken on the McDonnell-Douglas tool.
COGNALPac94
OF POOR QUALI- t
Russtech Toul
Insulation	 Size
Kapton	 20
22
24
Minimum
Retention Obs)
6.93
5.9
6.06
Maximum
Retention Obs)
9.46
9.5
9.0
PVC	 16	 7.0	 9.03
20	 8.0
	 11.0
22	 7.8	 9.73
24	 6.8	 7.83
Teflon	 12	 9.1
	 11.4
14	 7.2
	 8.9
16	 6.1
	
7.63
18	 6.46	 7.46
20	 5.5
	 6.56
22	 5.6
	 5.6
24	 4.03
	 5.23
26	 4.53
	 4.56
McDonnell-Douelas Tool
Insulation	 Size	 Maximum Retention Obs)
Kapton	 20
22
24
6.9
5.4
6.5
PVC
	
16 7.9
20 11.3
2:' 8.65
24 7.65
Teflon	 12 9.15
14 6.6
16 6.4
18 6.25
20 5.8
22 4.9
24 3.8
26 4A
9
CONCLUSIONS
Since "pull-tests" forces are bounded by a minimum (intern&! friction) pull
force and a maximum (crimp strength) pull force, no "pull-test" will be 100 percent
accurate. The McDonnell-Douglas tool is not as dependent upon pull angle as is the
Russtech tool. The Russtech tool is saaaller; therefore it can be easier to use in
small spaces. Beth tools are adequate for "pull-testing" Deutsch Blocks.
10
APPROVAL
ANALYSIS OF "PULL-TEST" TOOLS AND THEIR LIMITATIONS AS
APPLIED TO TERMINAL JUNCTION BLOCKS
By James Lee Smith
The information in this report has been reviewed for technical content. Review
of any information concerning Department of Defense or nuclear energy activities or
programs has been made by the MSFC Security Classification Officer. This report,
in its entirety, has been determined to be unclassified.
Director, information and
Electronic Systems Laboratory
*U.S. GOVERNMENT PRINTING OFFICE 1983-646-068/183
	 11


Analysis of Full-Test tools and their limitations as applied to terminal junction blocks

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server