2nd Japan-China Joint Symposium on Fatigue of Engineering Materials and Structures, October. 17, 2011, Chengdu, China

DEVELOPMENT AND FUNDAMENTAL PERFORMANCE OF
DUAL-SPINDLE ROTATING BENDING FATIGUE TESTING
MACHINEWITH SPECIAL DEVICE PROVIDING CORROSIVEENVIRONMENTS
Taizo Yamamoto1*, Akio Kokubu 1, Tatsuo Sakai 2, Ippei Kiyama3 and Yuki Nakamura412Yamamoto Metal Technos Co., Ltd. 4-7 Setoguchi 2-chome, Hirano-ku, Osaka 547-0034, Japan

Research Organization of Science and Engineering, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga525-8577, Japan
3

Graduate Student, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga 525-8577, Japan4

Toyota National College of Technology, Eiseicho 2-1, Toyota-shi, Aichi, 472-8525, Japan

ABSTRACT: Recently, particular attention has been paying to the fatigue property of metallic materials in the very
high cycle regime and in corrosive environments from viewpoints to ensure the long term durability of mechanicalstructures and to realize the low-carbon sustainable society. Various kinds of mechanical structures have to be used incorrosive environments. In the mechanical design of such products, fatigue test data in the corresponding environment
should be obtained as the fundamental design data. Conventional fatigue tests are conducted by setting the run-out
number of loading cycles to N=107, but the fatigue property in gigacycle regime is also focused as an important subject
in recent years. In such a long life region, a tremendous long period is required to perform fatigue tests. In this study, a
new type of dual-spindle rotating bending fatigue testing machine was developed in order to overcome these difficulties.
By using this machine, one can perform the fatigue tests for four specimens simultaneously in rotating bending in thecorrosive environment of 3% salt water. In this new type of machine, dual spindles are driven by an electric motor via
V-belt and special technique was introduced in this additional facility in order to avoid the corrosive damage of thefatigue testing machine itself.
Keywords: gigacycle regime, corrosive environment, fatigue test, rotating bending, GIGA QUAD

1. INTRODUCTION
One of difficulties in fatigue tests for structural materials isto take a long time to perform the fatigue test. Fatigue
tests are usually conducted toward the loading cycles of
N=107, but the fatigue property in gigacycle regime is also
focused as an important subject in recent years[1]-[3]. Insuch a long life region, a tremendous long period isrequired to perform fatigue tests. If the fatigue test isperformed at the loading frequency of 50Hz, it takes 200
days to reach 109 cycles of the load application. It meansthat it takes very long term for us to obtain one S-N curve.
If the high loading frequency such as ultrasonic
fatigue test was accepted, temperature raising of thespecimen due to the internal friction would take place andsome cooling system should be furnished to examine theoriginal fatigue property[4,5]. Thus, the acceleration
fatigue test by ultrasonic technology would cause new
difficult subjects as the fatigue testing method to obtainthe fatigue property at the usual frequency.
In order to overcome these difficulties, authors havedeveloped special types of fatigue testing machines inrotating bending, in which four specimens can be tested

simultaneously. Thus a series of fatigue tests even ingigacycle regime can be carried out within a reasonable
period. Based on this advantageous performance, thename of “GIGA QUAD” was accepted for this newmachine. By using GIGA QUAD, fatigue tests can beperformed much quickly comparing with the conventional
testing machines even if it is used with the corrosive
environment option. Accordingly, this machine is useful
to file up a number of fatigue test data in gigacycle regime
for various kinds of metallic materials, and such databases
can provide the fundamental design data for mechanicalstructures in the wide variety of the engineering
application.
2.
DUAL-SPINDLEROTATING
FATIGUE TESTING MACHINE

BENDING

This machine has two spindles and two specimens
can be mounted at both ends of each spindle as indicatedin Fig.1. Each spindle is driven by an electric motor via
a V belt and the number of revolution is counted bymeans of photo-sensor. Thus, this machine can perform
fatigue tests for 4 specimens simultaneously. In order to2nd Japan-China Joint Symposium on Fatigue of Engineering Materials and Structures, October. 17, 2011, Chengdu, Chinaapply the testing load, the corresponding weight issuspended through a helical spring attached to the outerblock. The rotating speed of the spindle, that is, thetesting speed is 3150rpm (52.5Hz)
GIGA QUAD has two types of ‘YRB200’ and‘YRB200L’ according to the loading capacity (Maximumload). The maximum load of YRB200 is 20kg, whereas
the load of YRB200L is 80kg.

Table 1: Specification of the Device
ModelMotor
CapacitanceCollet ChuckMax LoadSpindle Speed
WeightSizeBeltSpindle Number
Bearing (Spindle)

SpecimenCollet nut
Outerblock
Counter

SpringWeightYRB200 / YRB200L
0.2kw-4P / 0.4kw-4p
380V
φ2.5～13 / φ2.5～2020kg x 4 / 80kg x 43150rpm
140kg / 170kg
470x400x1050 / 800x660x1100
V Belt M
2Angular Contact Ball Bearing

Collet nut

Fig. 2: GIGA QUAD

Specimen

YRB200L

Outer
block
Hourglass type of specimen as shown in Fig.2 isaccepted as a formal test piece. Diameter of the criticalsection ‘φβ’ is designed as to give the reasonable stresslevel for the each material, while the diameter of thespecimen grip ‘ φ γ’ may be decided by user freely.
Collet chucks with different diameters such as 6mm,
8mm and 10mm are prepared in advance. Among them,
the user can choose the most preferable collet chuckdepending on the individual circumstance for the testingmaterial.

Counter
SpringWeightFig. 1: GIGA QUADYRB200Fig. 3: The shape and dimensions of the specimen
22nd Japan-China Joint Symposium on Fatigue of Engineering Materials and Structures, October. 17, 2011, Chengdu, China

3. FOUR MAIN ADVANTAGES

3.4. Support for environmental testing

3.1. High efficiency

Various kinds of mechanical structures have to beused in corrosive environments. In the mechanical designof such products, fatigue test data in the corresponding
environment should be obtained as the fundamental
design data. GIGA QUAD can be applied to perform
fatigue tests in such cases. As indicated in Fig.5 and 6, a
special chamber can be attached around the individualspecimen.
Corrosive solution is pooled in a tank inside the top
space of the stand as indicated in Fig.5, and the tank isconnected to the chamber by a polymer tube as indicatedin Fig.6. Of course, the solution feeding rate can be given
at any level by using the adjuster mounted on the front
surface of the stand. In this manner, the corrosive solution
is dropped onto the critical portion of the specimen at thedefinite rate. Special technique was introduced in thisadditional facility in order to avoid the corrosive damageof the fatigue testing machine itself. From this point ofview, a little negative pressure was always given inside
the corrosive chamber so that the corrosive solution andits fine splashes do not leek out from the chamber. This
corrosive chamber can be installed depending on therequirement by the customer. Fig.6 indicates an example
of such testing machine with a couple of corrosive
chambers. Same kind of corrosive environment can begiven in both chambers, and different corrosive
environments can be also given in the respective
chambers.

This machine is convenient to get a number offatigue test data very quickly, because four specimens canbe tested simultaneously. In order to obtain one S-N
curve, four specimens can be tested at different stresslevels by giving different weights for the respective
specimens. Thus, S-N property of a definite material
can be obtained within the reasonable short period.
From this point of view, the present machine of GIGA
QUAD has a significant performance of the highefficiency.
3.2. Easy operation
In this testing machine, the specimen can be easily
fixed and removed as indicated in Fig.4. 1 and 2 in Fig.4
show how to fix the specimen, and 3 and 4 show how toremove the specimen. As mentioned above, different
diameters of 6mm, 8mm and 10mm are prepared as theinner diameter of the collet chucks. Thus, the user canchoose the most convenient size of the collet chuck.

1. Insert the specimen

2. Tighten the collet nut

Stand
3. Loosen the collet nut

Fig. 6

4. Pull out the specimen

Fig. 4: Simple procedure to fix and remove the specimen

3.3. Precise eccentricity
Eccentricity at the outer end of the specimen afterchucking was kept within ±20μm. Such a small
eccentricity is fundamentally very important to performthe fatigue tests in rotating bending. If the eccentricity
becomes large, problems of vibration and noise take placein the fatigue tests and, therefore, some extent of error isincluded in the applied stress. According to preliminary
experiments, no effect of the eccentricity was found for
fatigue test data to obtain the S-N property, if theeccentricity is kept within ±30μm. This is the reason why
the eccentricity of this testing machine was restrictedwithin the small value of expecting some extent ofmargin.

Fig. 5: Photograph of fatigue testing machine combinedwith the corrosive chamber32nd Japan-China Joint Symposium on Fatigue of Engineering Materials and Structures, October. 17, 2011, Chengdu, China

Flowing pass-tube

Tubepump

Resinchamber

Outer
block

Corrosivesolution

SpindleCompressed
airCorrosive chamber

Specimen

Fig. 6: Corrosive chamberAircompressor

Corrosive solution is pooled in a tank inside the top
space of the stand as indicated in Fig.5, and the tank isconnected to the chamber by a polymer tube as indicatedin Fig.6. Of course, the solution feeding rate can be given
at any level by using the adjuster mounted on the front
surface of the stand. In this manner, the corrosive solution
is dropped onto the critical portion of the specimen at thedefinite rate. Special technique was introduced in thisadditional facility in order to avoid the corrosive damageof the fatigue testing machine itself. From this point ofview, a little negative pressure was always given inside
the corrosive chamber so that the corrosive solution andits fine splashes do not leek out from the chamber. This
corrosive chamber can be installed depending on therequirement by the customer. Fig.6 indicates an example
of such testing machine with a couple of corrosive
chambers. Same kind of corrosive environment can begiven in both chambers, and different corrosive
environments can be also given in the respectivechambers.
Fig.7 indicates the schematics of the corrosion
fatigue testing machine. Corrosive solution is stored in
the tank inside the stand, and the solution is pumped upby the tube pump. Thus, the corrosive solution can be
dropped down onto the specimen. Dropping rate of thecorrosive solution can be adjusted by an electric
controller attached on the front surface of the stand. The
dropped solution is sucked in the drainage tank provideda little negative pressure (weak vacuum) which isoperated by using compressed air.

WeightDrainagetankStandto give corrosive environment

Fig. 7: Schematics of corrosion fatigue testing machine
CONCLUDING REMARKS
Conventional fatigue tests take a long time such as
200days to reach N=109, and a number of fatigue test data
are required as the fundamental data in the mechanicaldesign. In order to solve such difficulties, the highperformance fatigue testing machine in rotating bending“GIGA QUAD” has been developed in this work.
Based on a lot of experimental results, thefundamental performance of this testing machine wasconfirmed. Actually these machines are already being
used at many laboratories in universities and industries.
Thus, every customer informed that this testing machine
is successfully used to obtain a number of fatigue data
within a reasonable short period.
REFERENCES[1] Sakai T. Review and Prospects for Current Studies on VeryHigh Cycle Fatigue of Metallic Materials for Machine
Structural Use. Proc. of VHCF-4, Ann Arbor, MI, USA,(2007), 3-12.
[2] Bathias, C., P. C. Paris. Gigacycle Fatigue in Mechanical
Practice, Marcel Dekker, 2005.
[3] Sakai T., Ochi Y., Jones J. W. Special Issue on the Third
International Conference on Very High Cycle Fatigue heldin Kyoto/Kusatsu, Japan on 16-19 September, 2004,
International Journal of Fatigue, 2006; 28: 1437.
[4] Ebara R. The Present Situation and Future Problems in
Ultrasonic Fatigue Testing – Mainly reviewed on
Environmental Effects and Materials’ Screening.
International Journal of Fatigue, 2006; 28: 1465-1470.
[5] Kirchner H. O. K., Kromp W., Prinz F. B., Trimmel P.
Plastic Deformation under Simultaneous Cyclic andUnidirectional Loading at Low and Ultrasonic Frequencies.
Mat. Sci. Eng., 1985; 68: 197-206.

4