A fully articulated four-point bend loading fixture for Modulus of Rupture (MOR) and fracture toughness specimens utilizes an upper loading plate in combination with a lower loading plate. The lower plate has a pair of spring loaded ball bearings which seat in V-shaped grooves located in the upper plate. The ball bearings are carried in the arms of the lower plate. A load is applied to the specimen through steel rollers, one large roller and one smaller roller each located on both the upper and lower plates. The large rollers have needle roller bearings which enable a single loading roller to rotate relative to the plate to which it is attached

Calomino, Anthony M.

English

NASA Technical Reports Server

United States Patent [191 
Calomino 
[i l l  Patent Number: 4,986,132 
[451 Date of Patent: Jan. 22, 1991 
[54] FULLY ARTICULATED FOUR-POINT-BEND 
LOADING FIXTURE 
[75] Inventor: Anthony M. Calomino, Cleveland, 
Ohio 
[73] Assignee: Tbe United States of America as 
represented by the Administrator of 
the National Aeronautics aad Space 
Abinisimtion, Washington, D.C. 
[21] Appl. NO.: 458,274 
[22] Filed: Dee. 28,1989 
[51] Int. Cl.5 ............................................... COlN 3/20 
[52] U.S. Cl. ...................................................... 73/852 
[58] Field of Search ........................... 73/812, 849-854 
mi References Cited 
U.S. PATENT DOCUMENTS 
2,243,842 6/1941 Fearn ................................... 265A.6 
2,732,712 1/1956 Reed ..................................... 73/812 
3,170,321 2/1%5 Sullivan et al. ....................... 73/100 
3,332,281 7/1967 Spangler ............................... 73/100 
3,937,072 2/1976 Huydts et al. ........................ 73/100 
4,677,856 7/1987 Fischer .................................. 73/850 
4,730,498 3/1988 Blanch .................................. 73/852 
FOREIGN PATENT DOCUMENTS 
0069140 3/1987 Japan ..................................... 73/849 
1100531 6/1984 U.S.S.R. ................................ 73/849 
OTHER PUBLICATIONS 
Tsvikenvich et ai., “Device for Static Bending Testing 
of Samples at Different Temperature and Media”, Ind. 
Lab (USA.), vol. 43, No. 3 (Mar. 1977). 
Primary Examiner-Robert Raevis 
Attorney, Agent, or Firm-Gene E. Shook; John R. 
Manning; James A. Mackin 
A fully articulated four-point-bend loading fixture for 
MOR and fracture toughness specimens utilizes an 
upper loading plate in combination with a lower loading 
plate. The lower plate has a pair of spring loaded ball 
bearings which seat in V-shaped grooves located in the 
upper plate. The ball bearings are carried in the arms of 
the lower plate. A load is applied to the specimen 
through steel rollers, one large roller and one smaller 
roller each located on both the upper and lower plates. 
The large rollers have needle roller bearings which 
enable a single loading roller to rotate relative to the 
plate to which it is attached. 
[571 ABSTRACT 
11 Claims, 3 Drawing Sheets 
14 
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U.S. Patent ~ m .  22,191 Sheet 1 of 3 4,986,132 
FIG. 1 
US. Patent ~ m .  22,1991 Sheet 2 of 3 4,986,132 
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US. Patent ~ m .  22,1991 Sheet 3 of 3 4,986,132 
14 
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FIG. 3 
4,986,132 
1 
FULLY ARTICULATED FOUR-POINT-BEND 
LOADING FIXTURE 
ORIGIN O F  THE INVENTION 
The invention described herein was made by an em- 
ployee of the United States Government and may be 
manufactured and used by or for the Government for 
governmental purposes without the payment of any 
royalties thereon or therefore. 
TECHNICAL FIELD 
This invention is concerned with an improved fixture 
for modulus of rupture (MOR) and fracture toughness 
specimens. The invention is particularly directed to a 
fully articulated four-point-bend loading fixture. 
Specimens used for modulus of rupture (MOR) and 
chevron-notched four-point bend tests are made of brit- 
tle materials. The size specifications for those specimens 
are established by the Army Materials and Mechanics 
Research Center (AMMRC) now known as the U.S. 
Army Materials Technology Laboratory. 
One prior art fixture has been specifically designed by 
AMMRC to perform brittle-material strength tests. 
However, the prior art fixture does not articulate and 
cannot be used on specimens which are warped, twisted 
or non-parallel. Reference is made to Ad-AI60 873, 
“Commentary on U.S. Army Standard Test Method for 
Flexural Strength of High Performance Ceramics at 
Ambient Temperature.” 
An improved prior art fixture is designed to accept 
beams with twist, warp, or non-parallelism. However, 
the design of this fixture is considerably more complex 
than the ureviouslv mentioned mior art fixture. See 
5 
10 
15 
20 
25 
30 
35 
“Reductidn of Errors in Ceramic bend Test”, Journal of 
American Ceramic Sociew, 59, 5-6, 1976. 
A major problem encountered in the AMMRC fix- 
ture is that the device does not accommodate less than 
perfect beams. Although the improved fixture accom- 
modates imperfect test specimens, the structure is quite 
complicated. 
It is, therefore, an object of the present invention to 
provide loading for modulus of rupture and chevron- 45 
notched four-point bend specimens made of brittle ma- 
terials. 
Another object of the invention is to provide a load- 
ing fixture which will accommodate specimens having 
size specifications established by the U.S. Army Materi- 50 
als Technology Laboratory. 
40 
PRIOR ART 
U.S. Pat. No. 2,243,842 to Fearn discloses a device 
for indicating springiness of strands which includes 55 
idler rollers that support the ends of the strand. A wheel 
applies a force to the strand. 
U.S. Pat. No. 3,170,321 to Sullivan et a1 is concerned 
with a fatigue testing machine. The device utilizes a 
gripping member on the ends of the specimen and rol- 60 
lers mounted in ball bearing races. 
U.S. Pat. No. 3,332,281 to Spangler is directed to a 
device for measuring biaxial stress-strain. The apparatus 
includes a specimen support member having O-rings to 
support the ends of the specimen. 
U.S. Pat. No. 3,937,072 to Huydts et a1 is concerned 
with a system for measuring deformation in a bending 
press. The press has rollers mounted on a pivotable 
65 
2 
yoke. This yoke is utilized in combination with a central 
roller. 
U.S. Pat. No. 4,730,498 to Blanch describes a fixture 
for holding a bending test specimen. This structure 
includes a gripping member mounted on a carnage 
through canted rollers. 
DISCLOSURE OF THE INVENTION 
This invention is directed to a fully articulated four- 
point-bend loading fixture for a modulus of rupture and 
fracture toughness specimen. The fixture includes an 
upper loading plate in combination with a lower loading 
plate. The lower plate includes a pair of spring loaded 
ball bearings which seat in V-shaped grooves located in 
the upper plate. The ball bearings are in the arms of the 
lower plate. 
Load is applied to the specimen through steel rollers, 
one large roller and one smaller roller, each located on 
both the upper and lower plates. The large rollers have 
associated therewith needle roller bearings to enable a 
single loading roller to rotate on an axis at right angles 
to the axis of the roller. 
BRIEF DESCRIPTION OF THE DRAWING 
The advantages and novel features of the invention 
will be more fully apparent from the following detailed 
description when read in connection with the accompa- 
nying drawings wherein; 
FIG. 1 is a perspective view of an upper loading plate 
constructed in accordance with the present invention to 
provide a predetermined fixed loading span; 
FIG. 2 is a perspective view of a lower loading plate 
constructed in accordance with the present invention to 
provide a predetermined outer span; and 
FIG. 3 is a front elevation view with portions broken 
away showing the assembly of the fixture which com- 
prises the upper loading plate operably mounted over 
the lower loading plate. 
BEST MODE FOR CARRYING OUT THE 
INVENTION 
Referring now to the drawing, there is shown a self- 
aligning, fully articulated system for loading brittle 
material beam specimens in a four-point, or pure bend- 
ing configuration. A fixed span X is provided by an 
upper loading plate 10 shown in FIG. 1. Such a fixed 
span of 20 millimeters meets the aforementioned re- 
quirements. 
This upper loading plate 10 is automatically centered 
about a 40 millimeter outer span Y on a lower loading 
plate 12 shown in FIG. 2. A pair of upwardly extending 
alignment arms 14 and 16 are secured to opposite ends 
of the lower loading plate 12 by location bolts 17 as 
shown in FIGS. 2 and 3. 
Each of these arms has a hole 18 which encloses a ball 
bearing 20 shown in FIG. 3. A spring 22 in the bottom 
of the hole 18 urges the respective ball 20 into engage- 
ment with a mating V-shaped groove 24 in the upper 
plate 10. This fitting of the ball bearings 20 carried by 
the alignment arms into the two V-shaped grooves 24 
on either side of the upper loading plate 10 accommo- 
dates rotation of this upper loading plate with respect to 
the lower loading plate 12. Portions of the ends of the 
upper plate on opposite sides of the V-grooves engage 
suiteable bearing plates 25 mounted on the arm 14 and 
16. 
A hardened steel roller 26 is mounted for movement 
in a recess 28 in the upper loading plate 10. Referring to 
4.986,132 z -  
3 
FIG. 3, the roller 26 is positioned by a pair of springs 30, 
one on each side of the upper loading plate 10. One end 
of each spring 30 is secured to each end of an axle 32 
which extends through the roller 26. The opposite end 
of each spring is mounted on a pin 34 on either side of 
the upper loading plate 10. 
A similar hardened steel roller 36 is mounted for 
rolling motion in a recess 38 in the lower loading plate 
12 as shown in FIGS. 2 and 3. A pair of springs 40, one 
on each side of the lower loading plate 12, positions the 
roller 36 in the recess 38 as shown in FIG. 3. One end of 
each spring 40 is secured to an end of an axle 42 which 
extends through the roller 36. The opposite end of each 
spring 40 is mounted on a pin 44 which extends from the 
lower loading plate 12. It will be appreciated that pins 
44 are provided in both faces of the lower loading plate 
12. 
An important feature of the invention is the provision 
of large diameter hardened steel rollers 46 and 48. Re- 
ferring now to FIGS. 1 and 3, the roller 46 is mounted 
for movement in a slot 50 in the upper loading plate 10. 
The roller 46 is positioned by a pair of springs 52, one 
on each side of the upper loading plate 10, as shown in 
FIG. 3. One end of each spring 52 is secured to each end 
of an axle 54 which extends through the roller 46. The 
opposite end of each spring is mounted on a pin 56 on 
either side of the upper loading plate 10. 
Referring to FIGS. 2 and 3, the other large diameter 
hardened steel roller 48 is similarly mounted in a slot 58 
in the lower loading plate 12 by a pair of springs 60, one 
on each side of the lower loading plate 12. One end of 
each spring 60 is secured to an end of an axle 62 which 
extends through the roller 48. The opposite end of each 
spring 60 is mounted on a pin 64 on either side of the 
A unique innovation found in this loading fixture is 
that the large diameter rollers rest on needle roller bear- 
ings. More particularly, the roller 46 is urged into en- 
gagement with a needle roller bearing 66 which extends 
through the slot 50. In a similar fashion the roller 48 is 40 
urged into engagement with a similar needle roller bear- 
ing 68 which extends through the slot 58. 
It is apparent from FIG. 3 that load is applied to a 
beam specimen 70 mounted in the fixture through the 
hardened steel loading rollers 26. 36. 46 and 48 which 45 
lower loading plate 12. 35 
5 
10 
15 
20 
25 
30 
, ,  " 
are free to roll during loading so as to minimize axial 
friction loads. In addition, the rollers 46 and 48 which 
rest on the needle roller bearings 66 and 68, respec- 
tively, enable a single loading roller 46 and 48 to freely 
rotate relative to the plate 10 or 12 to which it is at- 
tached. As shown in FIG. 3, loading is applied to the 
fixture through a loading ball bearing 72 which engages 
the upper loading plate 10 in a recess 74 shown in FIG. 
2. 
While the preferred embodiment of the invention has 
been shown and described, it will be appreciated that 
various modifications may be made to the loading fix- 
ture without departing from the spirit of the invention 
or the scope of the subjoined claims. By way of exam- 
ple, it is contemplated that locating pins could be pro- 
vided to facilitate alignment of the beam specimen cen- 
ter with the center of the loading spans X and Y and 
loading plates 10 and 12. 
I claim: 
1. A self-aligning, fully articulated four-point-bend 
loading fixture for modulus of rupture and fracture 
toughness testing of a brittle material specimen which is 
warped, twisted, or non-parallel comprising 
50 
55 
60 
65 
4 
an inner fixed span provided by a first loading plate 
having a groove on each end thereof, 
a second loading plate spaced from said first loading 
plate for providing an outer span, 
pair of arms secured to opposite ends of said second 
loading plate facing the oppositely disposed 
grooves in said first loading plate, 
means on each of said arms for resiliently mounting a 
ball bearing for engaging said first loading plate in 
said grooves thereby centering said inner fixed 
span about said outer span while accommodating 
rotation of said upper loading plate with respect to 
said lower loading plate, 
a pair of first rollers mounted for rotation about 
spaced first axles carried by said first loading plate, 
the spacing between said first axles establishing 
said inner fixed span, and 
a pair of second rollers mounted for rotation about 
spaced second axles carried by said second loading 
plate, the spacing between said second axles estab- 
lishing said outer span, said first and second pairs of 
rollers engaging said specimen for applying the 
load thereto. 
2. A fully articulated four-point-bend loading fixture 
as claimed in claim 1 wherein the fixed span between 
the axles on the first loading plate is about 20 millime- 
ters. 
3. A fully articulated four-point-bend loading fixture 
as claimed in claim 1 wherein the fixed span between 
the axles on the second loading plate is about 40 milli- 
meters. 
4. A fully articulated four-point-bend loading fixture 
as claimed in claim 1 wherein each pair of first and 
second rollers comprises a hardened steel roller having 
a first diameter and another hardened steel roller having 
a diameter greater than said first diameter. 
5. A fully articulated four-point-bend loading fixture 
as claimed in claim 4 wherein needle bearings are pro- 
vided for engaging said other roller at right angles to its 
axis whereby said large diameter roller is free to rotate 
on an axis at a right angle to its axis of rotation. 
6. In a self-aligning, fully articulated four-point-bend 
loading fixture of the type having a first pair of hard- 
ened steel rollers for engaging one surface of a brittle 
material specimen which is warped, twisted, or non- 
parallel to apply a load thereto at an inner fixed span 
and a second pair of hardened steel rollers for engaging 
an opposite surface of said specimen to apply a load 
thereto at an outer span for modulus of rupture and 
fractured toughness testing, the improvement compris- 
ing 
ball bearing means for accommodating rotation of 
said first pair of hardened steel rollers with respect 
to said second pair of hardened steel rollers, 
mounting means for positioning said first and second 
pairs of said hardened steel rollers at said spans on 
opposite sides of said specimen for free rotation as 
said load is applied, 
first needle bearings mounted at right angles to one of 
said first pair of rollers for engaging the same so 
that said one of said rolIers is free to rotate on an 
axis at right angles to its axis of rotation, and 
second needle bearings mounted at right angles to 
one of said second pair of rollers for engaging the 
same so that said one of said second pair of rollers 
is free to rotate at right angles to its axis of rotation. 
7. A fully articulated four-point-bend loading fixture 
as claimed in claim 6 wherein each pair of hardened 
4,9 86,132 
5 6 
steel rollers comprises one roller and another roller 
having a diameter greater than that of said one roller. 
8. A fully articulated four-point-bend loading fixture 
as claimed in claim 7 wherein said needle bearings en- 
whereby each large diameter roller is free to rotate on 
an axis at a right angle to its axis of rotation. 
9. In a self-aligning, fully articulated four-point-bend- 
for engaging one surface of a brittle material specimen 
load thereto at an inner fixed span and a second pair of 
rollers for engaging an Opposite surface of said SPeci- 
men to apply a load thereto for modulus of rupture and 15 groove. 
fracture toughness testing, the improvement Comprising 
spaced loading plates for mounting said first pair of 
rollers in spaced apart relationship establishing the 
inner fixed span and said second pair of rollers at a 
spacing establishing said outer span, said first and 20 
second pairs of rollers being mounted for rotation 
about their normal axes as said load is applied, 
a Pair of arms s e ~ r e d  to opposite ends ofthe loading 
plate that mounts said second pair of rollers facing 
that mounts said first pair of rollers, and 
a member carried by each of said arms for engaging 
one of said grooves thereby centering the inner 
fixed span about said outer fixed span while accom- 
respect to the other loading plate. 
gage said other rollers at right angles to their axes 5 OPPOsitelY disposed grooves in the loading Plate 
loading fixture Of the having a first pair Of 
10 modating rotation ofone ofsaid loading plates with 
which is twisted, Or non-parallel to a 10. A fully articulated four-point-bend loading fixture 
as claimed in claim 9 wherein the member carried by 
each arm comprises a ball bearing for engaging said one 
11. A fully articulated four-point-bend loading fixture 
as claimed in claim 10 including resilient means for 
urging said ball bearing into engagement with said 
groove. * * * * *  
25 
30 
35 
45 
50 
55 
60 
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Fully articulated four-point-bend loading fixture

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