Apparatus for tensile strength testing of specimen by pressurized flui

Wallace, E. D.

English

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https://ntrs.nasa.gov/search.jsp?R=19710006125 2020-03-17T02:40:26+00:00Z
il;"eb. 3, 3970 E. D. WALLACE 3,492,862 
APPARATUS FOR TENSILE TESTING 
F i l e d  June 21, 1967 
INVENTOR. 
ELVIS D. WALLACE 
3,492,862 United States Patent Ofice 
,e, , ,,,, 
3,492,862 
APPARATUS FOR TENSILE TESTING 
EIvls D, Wallace, Huntsville, h4a., assignor to the United 
Sfates of Anledca as represented by the Adminiskator 
of the National AeronauHcs and Space Adntinis&ation 
Filed June 21, 1967, Ser. No. 649,075 
of the specimen to the base plate. (6) an inlet passageway 
extending through the load cell cori~municaliisg with the 
cylinder between the top and bottom portions of the spe- 
cimen adjacent the reduced test portion, (7) a high pres- 
sure fine having one end coupled to the inlet passageway, 
(8 )  a source of preselected pressurized Enid of which de- 
Pnt. Cl. Goln 3/28 vices constructed from materials forming said specimen 
U.S. el. 93-97 1 Clain~ would be subjected to in use coupled to ;he othef end of 
the high pressure line. The pressurized fluid bears against 
10 the reduced portion of the specimen for detelmining the 
ABSmACT OF THE DISCLOSURE effect the fluid has on the specimen during extended 
An apparatus for determining the tensile strength of a periods of time under pressure.-when the ~ressure of the 
specimen which has been machined into the form of a fluid is raised causing the reduced portion of the speci- 
piston. Pressurized fluid of which devices constructed men to fail the top poltion of the specimen is ejected out 
from material forming the specimen would be subjected 15 the top of the cylinder. 
to in use is inserted within a cylinder of a load cell be- Accordingly, it is an important object of the present in- 
tween two enlarged ends of the test specimen. By in- vention to provide an apparatus for determining the ten- 
creasing the pressure until the specimen fails the tensile sile strength of a specimen in a predetermined environment. 
strength of the specimen can be calculated. Another important object of the present invention is 
2" to provide a simple, inexpensive apparatus for testing the 
tensile strength of specimens. 
The invention described herein was made by an em- Still another important object of the present invention 
ployee of the United States Government, and may be is to provide an apparatos for testing the tensile strength 
manufactured and used by or for the Government for of specimens which can be placed in remote areas or test 
governmental purposes without the payment of any royal- 25 chambers away from personnel and equipment. 
ties thereon or therefor. Still another important object of the present invention 
This invention relates to a tensile strength tester, and is to provide an apparatus in which the specimen can be 
more particularly to an apparatus for determining the exposed to predetermined pressures and reactive agents 
tensile strength of a specimen in a predetermined environ- for extended periods of time in order to determine the 
ment. 30 effect such has thereon. 
The need has arisen particularly, in the missile field A further important object of the present invention is 
for testing the tensile strength of materials used in the to provide a tensile strength testing apparatus which re- 
construction of both space vehicles and, ground support ceives a specimen in the form of a piston having a pair 
equipment, and the like, under particular environmental of opposed enlarged ends joined by a reduced  ort ti on 
conditions to which the space vehicle or its ground sup- 35 which does not require complicated holding devices. 
port equipment may be exposed. Certain components of Other objects and advantages of this invention will be- 
the space vehicle are exposed to reactive fluids, such as come more apparent from a reading of the following 
acids and the like, and ale also under pressure and ex- detailed description and appended claims taken in con- 
posed to various temperatures. In testing the material which *" junction with the accompanying drawing wherein: 
is used in constructing such components, it is desired to FIGURE 1 is an elevational view, partially in section, 
know the cumulative effect as well as the singular effects illustrating an apparatus for determining the tensile 
of pressure, temperature and reactive agents on the ma- strength of a specimen, and 
terial. Many tensile devices are on the market; however, FIGURE 2 is a plan view with parts removed, illus- 
they are generally expensive and relatively complicated 45 trating the load cell of FIGURE 1. 
and not suitable for testing the tensile strength of speci- Referring in more detail to the drawing wherein like 
mens while exposed to particular enviro~lmental condi- reference numerals designate identical or corresponding 
tions. Normally, they use an external source of power for parts throughout the views, and with special attention to 
pulling or tearing a test specimen asunder in order to de- FIGURE 1, reference numeral 10 generally designates a 
termine the tensile strength of such, and the exposure 50 load cell which is utilized to test the tensile strength 
of the specimen to environments in these testers is ex- of a specimen. The load cell 10 is cylindrical in shape, 
tremely difficult, expensive and frequently relatively un- and has a wall 11 constructed in any suitable material 
safe. The design of these testers also is such that their such as steel. A vertical cylinder 12 is disposed along 
use is generally confined to fixed laboratory facilities. a vertical axis of the load cell and has an open top and 
It is desired to provide a simple and efficient apparatus 55 a bottom defining a piston chamber. A flat horizontal 
for testing the tensile strength of certain specimens under base plate 13 is rigidly fixed to the load cell 19 by 
particnlar environmental conditions. any suitable means, such as screws 14, closing the bot- 
In accordance with the present invention, it has been tom of the cylinder 12. The base plate 13 may be con- 
found that the foregoing difficulties encountered in ap- structed of any suitable material such as steel. 
paratus for testing the tensile strength of specimens may 60 A specimen of material, which is to be tensile tested, 
be overcome by providing a novel apparatus for detel- is machined into a piston, generally designated at  15. 
mining the tensile strength of the specimen in a predeter- The piston has an enlarged top portion 16 and an 
mined environment. This apparatus includes the following elongated reduced test poitioil 17 of predetermined di- 
basic parts: (1) a load cell including a cylinder having ameter integral therewith. The piston 15 has an enlarged 
a top and a bottom defining a piston chamber, (2) a base (,-, bottom portion 18 integral with the lower end of the 
plate rigidly fixed to the load cell closing the bottom of the reduced portion 17. Vertically spaced circumferential 
cylinder, (3) a test specimen in the form of a piston hay- grooves 19 are carried within the enlargeel top portions 16 
ing an enlarged top poltion and an enlarged bottom por- and the enlarged bottom pori-ion 18 of the piston 15 for 
tion being joined by an elongated reduced test portion of receiving butyt O-rings 2(a and Teflon back-up rings 21. 
predetermined diameter carried in the cylinder, (4) seals 70 Any suitable sealing means could be utilized. A screw 22 
carried between the enlarged top portion of the specimen extends ihiough the base plate 13  and engages the en- 
and the cylinder, (5) means arichoring the bottom portion larged bottom portion 18 of the piston 25 for anchoring 
3,492,862 
3 4 
such within the cylinder. An inlet Faisageway having a 18, and the ends threaded .,o that such can be ~ciewed 
red~tced portion 23 and an enlarged threaded portion 24 into threaded holes p~ovided 111 the eiil.nged ends. In such 
integral therewith, extends through the wall 11 of the a constinction the enlarged enils can be ~euied.  The prston 
load cell 40 and con~municntes wirh the miexior of th- 17 inseried mithin the cylinder 12 and anchored to the 
cylinder 12 The reduced portion 23 of the rnlet n a s , r y -  - bottom by ille sciew 22. Ths jest media oi fluid wniih 
way is positxoned withrn the wall l l  of the lorid cell V J O L : ~ ~  noririaliy be exposrd to coiiipoileilis or p d s  con- 
between the top arid bottom portions 16 ar?d 18, ie- struc'ccl finm the ni~tei1:ii f iom whrch the specimen was 
spectively, of the piston 15. An outlet passageway having selected 1s suppiled to the press~ir~zxi source 32. The 
a reduced portion 25 and a threaded enlarged portlon valves 34 and 29 are open a1loxlng the fluid to flow 
26 extends thlough the wall 11 of the load cc!! com- ,,) thro~~gil the high pressuie 11ne 31 m?o the cylxndei, and 
municating with the cylinder. A pressurized fitting 27 out ths high pressuie fine 28. The output valve 29 1s 
carried on the end of a high pressure line 28 is screwed then closed and the pressure is taised to a p~edetermined 
within the enlarged thieaded portion 27. A suitable valve level and held at that level for a selected period of time. 
29 is interposed in the high pressure line 28 for selectively From such a test the effect of the fluid on the specimen 
permitting passage of fluid therethrough. A high pressure 15 can be determined. During the holding test the strain 
fitting 30 carried on the end of a high pressure line 31 measuring device 36 will monitor the effect of the fluid 
is screwed into the enlarged threaded portion 24 of the and pressuie on the test specimen and any movement of 
inlet passageway. The other end of the high pressure the piston head 16 will be recorded by the strain meas- 
inlet line 31 is connected to a pressurized source of fluid uring device 36. It  is noted that the force being applied 
32. Such pressurized source 32 may be any suitable device 20 by the fluid is exeited on the top and bottom portions 
for supplying fluid through the input line 31 into the 16 and 18, respectively, of the piston 15 tending to sep- 
load cell under a controlled pressure. A pressure meter arate such. This action causes a stlain on the reduced 
33 and a valve 34 are interposed in the input line 31 for poition 17. 
measuring the pressure of the fluid passing therethrough After the holding period the pressure in line 31 is in- 
and for closing the line, respectively, in order to hold the 25 creased until the reduced test portion 17 of the specimen 
pressure in the line at a desired pressure level. Leads 35 fails causing the top poition 16 of the piston to be ejected 
are connected to the pressure meter 33 so that readings out of the cylinder 12 to strike the buffer plate 47. Cal- 
of such can be taken at a remote area. culations can be made by utilizing the piessuie ~ecorded 
Normally, the fluid supplied by the pressutized souice on meter 33 and the exposed area of the piston head 16 
32 is the same fluid (liquids or gases) in which devices 30 and the diameter of the reduced test po~tion 17 to de- 
constructed from material forming the test specimen termine the exact pounds per square inch which was re- 
would be subjected to in use. Such is to determine the quired to sever the test portion 17. 
effect on the material by the fluid when under pressure. The load cell 10 can be constructed to receive heating 
Typical fluid o r  media are liquid fluorine, various cryo- or cooling elements by any suitable means (not shown) 
genic liquids, unsymmetrical dimethyl hydlazine, and 35 so that the test specimen is exposed to pressure, a reac- 
other chemicals, gases or compounds. tive agent, and temperatme to determine the ~eaction on 
A strain measuring device, generally designated at 36, such in any particular environment. 
engages an upper surface of the piston 15 for measuring When the top portion of the piston is ejected fiom the 
the longitudinal strain OF the reduced test portion 17 when cylinder the camming lever 37 pivots out of the path of 
the specimen is under pressure. Any suitable strain 4U such to the dotted line position. During the holding pe- 
measuring device could be utilized in conjunction with riod the strain encountered in the test specimen causes 
the testing apparatus. The strain measuring device in- the piston to move ve~tically. This movement causes the 
corporates a camming lever 37 which is pivotally mounted camming lever 37 to  pivot upwardly and folces the 
on a pin 38 carried between a pair of posts 39. The plunger 42 to the right. The meter 43 records the move- 
camming lever has an outwardly extending arm 40 which " ment of the plunger in inches or the like. 
rests on top of the specimen, and as the specimen is ex- One particular advantage of the testing apparatus il- 
~ a n d e d  due to strain the arm is raised accordingly. An lustrated is that it can be positioned in remote areas and 
eccentric surface 41 is carried adjacent the other end of no complicated holding is ,equired for holding the 
the camming lever so that as the lever is raised during 50 specimen during lest, 
the test the eccentric surface 41 forces a plunger 42 as- while a preferred embodiment of the invention has 
sociated with a meter 43 to the right. A spring 44 is con- been described using specific terms, description is 
neckd betwen the arm 40 of the cammi% lever 37 and for illustrative purposes only, and it is to be understood 
the posts 39 for maintaining the arm in contact with that changes and valiatiolls may be made without depalt- 
the top of the piston 15. jj ing from the spirit or scope of the following claims. The meter 43 may be any suitable meter calibrated to What is claimed is: 
measure the vertical displacement of the piston 15 re- 
sponsive to lateral displacenlent of the plunger 42. Leads 1. An appar-s for determining the tensile strength of 
45 are connected to the meter 43 for providing a reading a specimen in a predetermined enviiontnent comprising: 
on a remotely located meter 46. Any suitable meter could (*) a load a 'ylinder having a top and 
be used for the meter 46. 60 bottom defining a piston chamber; 
When the pressure within the cylinder is built up to (B) a base plate rigidly fixed to said load cell enclosing 
the point where the reduced portion 17 of the specimen the bottom of said cylinder; 
tears apart, the enlarged top portion 16 is ejected from ( C )  a test specimen in the form of a piston having an 
the cylinder 12 and impinges upon a buffer plate or pad enlarged top portion and an elongated reduced test 
47 retained by any suitable holder 48. The purpose of portion of a predetermined diameter integral with 
the buffer pad 47 and the holder 48 is to prevent the said enlarged top portion; 
ejected portion of the specimen from incurring or causing (D) said test specimen being carried within said piston 
damage. chamber; 
In operation a specimen of rnatelial is machined into 70 (E) a seal fitted between said enlarged top portion of 
a piston 15 haying opposed enlarged ends, such as il- said lest specin~en and said cylinde~; 
histrated at 16 ard $8. T i e  ends of the piston are pro- (F) means for anchoring the bottom of said test sjxci- 
vided with sealing means, such as illustrated at 20 and men to said base plate, 
21. It is to be noted however, th,~t the reduced portion (C) an inlet passageway eutenilriig thioiigh haid load 
17 can be made separate from the enlargcd erids 16 and 7; cell communiciiiing \vrth .;act ~iiston c h a n ~ b e ~  below 
3,492,862 
5 6 
said enlarged top portion and adjacent to said elon- arm in contact with said enlarged top portion of 
gated reduced test portion of said test specimen; said test specimen; and 
(8)  a high pressure line having one end coupled to (0 )  said camming lever positioned on said load cell 
said inlet passageway; so that said arm norn~ally contacts said enlarged 
(I) a source of preselected pressurized fluid coupled top portion of said test specimen but pivots clear of 
to the other end of said high pressure line; 5 said cylinder when said pressure is raised by said 
( J )  valve means connected to said high pressure line valve means thereby causing said elongated reduced 
for regulating the pressure of said preselected pres- test portion of said lest specimen to fail and said 
surized fluid in said piston chamber; enlarged top portion of said test specimen to be 
(K)  a camming lever pivotally mounted on the top of ejected out of the top of said cylinder, 
said load cell adjacent to said cylinder; 
(L) one portion of said camming lever hav in~  an arm References Cited 
. . 
extend& into said cylinder and contactingsaid en- FOREIGN PATENTS 
larged top portion of said test specimen; 
(M) another portion of said camming lever having an 15 552~993 Great Britain. 
eccentric surface for operating a strain measuring CHARLES A. RUEEL, Primary Examiner device mounted on said load cell; 
(N) a spring connected between said camming lever J. R. FLANAGAN, Assistant Examiner 
and said load cell for normally maintaining said 


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