A compression test assembly is described which prevents buckling of small diameter rigid specimens undergoing compression testing and permits attachment of extensometers for strain measurements. The test specimen is automatically aligned and laterally supported when compressive force is applied to the end caps and transmitted to the test specimen during testing

Kariotis, A. H.

English

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l/.S.N .„->
REPLY TO
ATTN OF: GP
e»/
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
WASHINGTON, D.C. 20546
OCT 1 5 1973
TO: KSI/Scientific & Technical Information Division
Attention: Miss Winnie M. Morgan
PROM: GP/Office of Assistant General Counsel for
Patent Matters
SUBJECT: Announcement of NASA-Owned U.S. patents in STAR
In accordance with the procedures agreed upon by Code GP
and Code KSI, the attached NASA-owned U.S. Patent is being
forwarded for abstracting and announcement in NASA STAR.
The following information is provided:
U.S. patent No.
Government or
Corporate Employee
Supplementary Corporate
Source (if applicable)
NASA patent case No.
: ACr
, s~
0* . off
J
NOTE - If this patent covers an invention made by a corporate
employee of a NASA Contractor, the following is applicable:
Yes /X / No / /
Pursuant to Section 305(a) of the National Aeronautics and
Space Act, the name of the Administrator of NASA appears on
the first page of the patent; however, the name of the actual
inventor (author) appears at the heading of column No. 1 of
the Specification, following the words "... with respect to
an invention of ..."
Elizabeth A. Carter
Enclosure
Copy of patent cited above
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https://ntrs.nasa.gov/search.jsp?R=19730023591 2020-03-17T09:32:20+00:00Z
United States Patent
Fletcher et ai.
[in 3,757,568
[45] Sept. 11, 1973
154] COMPRESSION TEST ASSEMBLY
[76] Inventors: James C. Fletcher, Administrator of
the National Aeronautics and Space
Administration with respect to an
invention of; Anthony H. Kariotis,
Tallmadge, Ohio
[22] Filed: Feb. 25, 1972
[21] Appl. No.: 229,413
[52] U.S. Cl 73/94, 73/103
[51] Int. Cl GOln 3/04
[58] Field of Search 73/94, 103
156] References Cited
UNITED STATES PATENTS
3,490,273 1/1970 Warfield et al 73/94 X
3,397,572 8/1968 Stolz et al 73/94
Primary Examiner—Jerry W. Myracle
Attorney—John R. Manning et al.
[57] ABSTRACT
A compression test assembly for long, small diameter
test specimens having first and second means which in-
terfit in telescoping manner and respectively define
first and second holes centered around the same longi-
tudinal axis and having the same diameters. First and
second end cap means receive opposite ends of the first
and second means, respectively, and define third and
fourth holes centered around the same longitudinal axis
as the first and second holes. The test specimen when
placed in the first and second holes has first and second
ends which extend into the third and fourth holes when
the first and second means are interfittcd in telescoping
manner, the diameter of the first, second, third and
fourth holes being just sufficiently larger than the diam-
eter of the test specimen to prevent binding. The test
specimen is thereby automatically aligned and laterally
supported when compressive force is applied to the end
caps means and transmitted to the test specimen during
testing.
7 Claims, 2 Drawing Figures
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Patented Sept. 11, 1973 3,757,568
COMPRESSION LOADING
21
19
FIG.l
FIG. 2
COMPRESSION LOADING
3,757,568
1 2
COMPRESSION TEST ASSEMBLY element 11 defines a small diameter hole 13 centered
~ .„, -^^..^ ^,, ,,~,...™~ about the longitudinal axis thereof for receiving the test
ORIGIN OF THE INVENTION .
 spedmen „ *xplained hereafter Cylindrical element
The invention described herein was made in the per- 12 defines bore 14 centered about its longitudinal axis
formance of work under a NASA contract and is sub- 5 for receiving the shaft portion 15 of element 1 1. It fur-
ject to the provisions of Section 305 of the National ther defines hole 16 centered about its longitudinal axis
Aeronautics and Space Act of 1958, Public Law which has the same diameter as hole 13. The longitudi-
85-568(72 Stat. 435; 42 U.S.C. 2457). nal axis of hole 16 is coincident with the longitudinal
BACKGROUND OF THE INVENTION ,0 , ^ metal specimen 25 undergoing
1 . Field of the Invention compression testing is inserted into the telescoping ele-
The invention relates to a compression test assembly ments 11 and 12 of body 10 as shown in FIG. 2,
which prevents buckling of small diameter rigid speci- wherein element 11 is shown as inteifitted with element
mens undergoing compression testing and permits at- 12.
tachment of extensometers for strain measurements. IS Each of elements 11 and 12 is provided with a set of
2. Description of the Prior Art three coplanar drilled and tapped openings disposed
There are apparatuses disclosed in the prior art relat- 1 20° apart about the circumference of the respective
ing to compression testing of metal specimens. For ex- elements and extending to the centers thereof. One
ample, Ely .U.S. Pat. No. 3,421,366 discloses a stress drilled and tapped opening is illustrated in each ele-
testing apparatus in which the compression test speci- 20 ment and designated by reference .numerals 17 and 18,
men is enclosed at its ends by adapters which contain respectively. Another drilled and tapped opening is
the specimen in order that the specimen ends need not shown in phantom in each element and designated, re-
be threaded or otherwise attached to the compression spectively, by reference numerals 17' and 18' with the
test apparatus. However, applicant is not aware of prior third tapped opening in each element not being illus-
art that discloses a compression test assembly similar to 25 trated in the drawings. These tapped openings serve to
applicant's which prevents buckling of the test speci- receive two sets of set screws, one member of each set
men during compression testing. being shown in FIG. 1 and designated by reference nu-
<5I IMM A R Y OF THP OISP I O«JI IBPSU  F THE DISCLOSURE
 not shown ^^ tQ secure ^ specimen 25 within the
This and other disadvantages and defects of the prior 30 interfitting telescoping elements 11 and 12. The longi-
art are solved by applicant's invention which provides tudinal distance between the two sets of set screws de-
a compression testing assembly which is primarily con- fines the gage length of the specimen 25.
cerned with preventing buckling of small diameter As shown in FIG. 2, the test specimen 25 has a diam-
specimens during compression testing, in order to per- eter which is slightly less than the diameter of holes 13
mit use of commercially available extensometers to 35 and 16 to avoid binding that otherwise might occur due
measure strain. The test specimen is inserted into the to Poisson's ratio effect. The tested specimen is there-
holes defined by telescoping portions of the compres- fore supported axially during loading and column buck-
sion testing assembly and is secured therein by set ling is thereby eliminated. End caps 21 and 22 are es-
screws. The holes defined by the telescoping portions sentially cylindrical in form and define a bored portion
have a diameter which is just sufficiently larger than the 40 26 and 27, respectively, which is of sufficient diameter
diameter of the specimen under test to avoid binding to just receive end portions 28 and 29 of elements 1 1
that might otherwise occur. The specimen is therefore and 12. This is shown in FIG. 2. The end caps 21 and
supported axially during loading and column buckling 22 further define small holes 23 and 24, respectively,
is eliminated. The specimen extends beyond the ends which are of equal diameter to the 'diameter of speci-
of the telescoping portions of the assembly, and end men 25. The ends of the specimen 19 and 20 which ex-
caps are provided to enable support of the extended tend beyond the telescoping body 10 are received by
parts of the specimen at the load points and to assure holes 23 and 24 of end caps 21 and 22, respectively, as
axial alignment. The invention therefore enables mea- shown in FIG. 2. The compression loading of the as-
surement of strain over a specific gauge length during sembly is applied to the end caps which provide sup-
compression testing of small diameter specimens, and port for the specimen at the load points and assure axial
particularly provides ( 1 ) lateral support to prevent alignment thereof.
buckling, (2) extensometer attachment capability, and The present invention thereby 'prevents column
(3) automatic specimen alignment.' buckling of long, small diameter metal specimens un-
BRIEF DESCRIPTION OF THE DRAW.NGS: 55
FIG. 1 is a sectional view in exploded form of the ele- We claim:
ments comprising the compression test assembly ac- 1. A compression test assembly for long, small diame-
cording to the invention; ter test specimens, comprising:
FIG. 2 is a sectional view of the elements comprising first and second means for interfitting in telescoping
the compression test assembly with a specimen being manner and respectively defining first and second
shown under test. holes centered around the same 'longitudinal axis
DETAILED DESCRIPTION OF THE INVENTION ^™2£ eTca '^ reaving opposite
The compression test assembly according to the in-
 6J ends of the first and second means, respectively,
vention is illustrated in FIG. 1. The compression test and defining third and fourth holes centered
fixture body 10 comprises two interfitting telescoping around the same longitudinal axis as the first and
elements 11 and 12. T-shaped essentially cylindrical second holes,
3,757,568
the test specimen when placed in the first and second
holes having first and second ends which extend
into the third and fourth holes when the first and
second means are interfitted in telescoping man-
ner, the diameter of the first, second, third and 5
fourth holes being just sufficiently larger than the
diameter of the test specimen to prevent binding,
whereby the test specimen may be automatically
alined and laterally supported to permit compres-
sive force to be applied to the end caps means and to
transmitted to the test specimen during compres-
sion testing of the specimen.
2. A compression test assembly as in claim 1 further
comprising:
locking means defined by the first and second means is
for securely locking the test specimen in the first
and second holes.
3. A compression test assembly as in claim 2 wherein
the first and second ends of the test specimen are cou-
pled to the first and second end cap means respectively 20
for transmission of compressive force from the first and
second means to the test specimen during testing.
4. A compression test assembly as in claim 2 wherein
said locking means comprises a plurality of set screws
for engaging said test specimen.
5. A compression test assembly as in claim 4 wherein
said plurality of set screws consist of two sets of three
set screws with one of said sets being disposed in each
of said first and second means interfitting in telescoping
manner.
6. A compression test assembly as in claim 5 wherein
said first and second means interfitting in telescoping
manner are cylindrical bodies and the three set screws
making up each said set are coplanar and are disposed
120° from each other about the circumference of each
said body.
7. The compression test assembly of claim 6 wherein
the longitudinal distance between the two sets of set
screws defines the gage length of the test specimen.
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Compression test assembly

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