TECHNICAL REPORT

Development of Technologies Contributing to the Stable Operationof Steelmaking Steel Production Equipment
A. NAGAYAMA T. MIYACHIK. OTSUKA

A high percentage of steel production equipment mainly consists of rotating bodies, such as rolling mills andcontinuous casting machines. The performance of mechanical parts that support such rotating bodies is extremely
important in steel production equipment.
For many years, JTEKT has contributed to the stable operation of steel production equipment through theprovision of bearings, oil seals, universal joints and other products. In recent years, we are making efforts not onlyin the area of product technology, but also development of lubrication technologies such as oil seals and lubricationequipment, optimum design of bearings by bearing diagnosis using actual equipment, and appropriate repair
methods for long-term use of products. JTEKT aims not only to offer customers our products, but also to provide
comprehensive technology including how to use such products. This report introduces some concrete examples ofour efforts.
Key Words: rolling mill, continuous casting, long life, maintenance free, technical trend

1. Introduction
For many years, JTEKT has exerted efforts to offer
products such as bearings, oil seals and universal joints(UJ) for steel production equipment, as well as engage
in technological developments for each product. This is
why we have been able to maintain a significant share of
the market in the steelmaking domain. However, there
are many cases where it is impossible to sufficiently
address customers’ various concerns through providing
products alone. JTEKT aims to contribute to customers
through comprehensive technological proposals suited toa product’s application and usage environment.
In regards to bearings, for example, we have extended
bearing life by improving lubrication through efforts suchas enhancing oil seal functionality and developing an
oil/air lubrication system. Moreover, in relation to steel
production equipment, there is the potential for bearings
to be subjected to loads unforeseen at the design stage,
therefore an effective way of identifying the cause of
failure is load measurement on the actual equipment. Byleveraging our proprietary load measurement and analysis
technologies, JTEKT has elucidated the relationshipbetween the load status of the bearing interior andthe operating conditions of the bearing in equipment
to achieve optimum bearing design. Moreover, as an
initiative to maximize the life of bearings, UJs, andother products, we are proposing appropriate repair
methods. Against such a backdrop, this report introduces

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activities aimed at the stable operation of steel production
equipment.

2. Initiatives for Longer Bearing Life
The rolling process of steel production equipment is a
crucial process determining the quality of steel products,
therefore high reliability is required. Bearings used in
the roll necks of rolling mills, in addition to the common
failure type relating to rolling fatigue life, also entail
the issue of early-stage failure caused by foreign matter
penetrating from outside, and rust occurring in the bearing
interior due to the rolling water used in the rolling process
and scale generated from the slab. Figure 1 shows bearing
failure types. JTEKT is exerting effort to elucidate thecauses of failure and establish countermeasures from bothmaterial and lubrication perspectives.
High-speed rotation, heavy load

Penetration of rolling mill coolant and scale

Rolling fatigue of material Decrease in strength of lubricant film
Raceway wear
Internal-originating flaking

Rust

Surface-originating flaking

CracksFig. 1 Bearing failure types

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−Development of Technologies Contributing to the Stable Operation of Steelmaking Steel Production Equipment−

2. 1 Material Development
There are two types of bearings for use in the rollnecks of rolling mills; the backup roll bearing and workroll bearing. JTEKT developed JHS520* a long-lifehigh corrosion resistant bearing using high-performancematerial with the aim of making the abovementioned
bearings more robust against failures. The roll neckbearing (Fig. 2) and bearing features (Table 1) are shown
below. For details on material development, please referto page 22 of this report.
Backup roll bearing

Table 2 Features of material development for bearings for
multi-roll mills backup rollFeatures
Secured shock resistance on the outer ring byforming suﬃcient internal-softening layer.
①

In addition to securing rigidity on the deep
surface-hardening layer, increased re-grinding
allowance of the outer diameter surface.
Adopted case hardened steel for inner ring to②

improve rolling life in conditions where lubricant
oil ﬁlm formation is insuﬃcient.

In addition to the above material developments, thefollowing sections will introduce our latest initiatives
for lubrication improvement by enhancing oil seal
functionality and developing an oil/air lubrication system.

Work roll bearing

2. 2 Development of a High-sealability Oil-seal
Fig. 2 Rolling mill structure and roll neck bearing

Table 1 Features of roll neck bearing material development
Features①

Adopts long-life, high-corrosion resistant steel
with an optimized amount of Cr and Mo
JTEKTʼs original carbonitriding heat treatment②

improving corrosion resistance and wear
resistanceMoreover, multi-roll mills are used to produce theelectromagnetic steel sheets essential as material for theiron cores of hybrid car motors, and the generators andtransformers used in wind power generation. The backup
roll bearings used in these multi-roll mills should have
durability to operate in environments with insufficientlubricant oil film formation due to heavy loads. JTEKT
has developed JHS210 as a backup roll bearing for use inmulti-roll mills aimed at improving robustness in such an
operating environment. This bearing (Fig. 3) along with
its features (Table 2) are shown below.

A

H

B

G

⑴Development concept

Work roll bearings are supposed to operate in extremely
harsh environments exposed to high temperatures, rolling
water and scale. The four-row tapered roller bearing usedas the work roll bearing should be capable of heavyload and high-speed rotation. Moreover, the oil seals
used in this bearing should have excellent sealability inharsh environments (Fig. 4). The development concept
for this was to fully revise the cross-section profile ofthe lip portion and maximize the pump capacity to pushback influx of water, foreign matter, etc. from lubrication
retention and outside of the bearing. Moreover, lips wereplaced intermittently on the inter-inner ring seal, making
it possible to control the negative pressure inside thebearing.

C
D

F

Fig. 4 Sealed-type four-row tapered roller bearing forroll neck

E

Multi-roll mill

Back-up roll bearing (A - H)

Fig. 3 Structure of bearings for multi-roll mills backup roll

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Rolling water

Rolling water⑴Inter-inner ring seal

⑵Oil seal[Development concept]
・Control of negative pressure inside bearing
・Intermittent placement of lips
[Eﬀects]
・Release negative pressure up to −6 kPa
・Improved installation(No reverse lip)

[Development concept]
・Fully revise the cross-section profile of the lip portion
・Maximize the seal pump volume*[Effects]
・Reduced water influx by over 70% of the conventional product・Reduced lip temperature rise by 30% at aperipheral speed of 25 m/sec
・Reduced lip wear width by over 30%

Pump volume

・Fluctuation in bearing temperature
Fluctuation in bearing
temperature

Negative pressure occurrence

Bearing interior

OutsideNo negative pressure occurrence
Pump volume

Water* Pump volume: Ability to push backinflux of water, foreign matter, etc.
from outside of the bearing

Fig. 5 Sealed bearing for work roll neck and seal development concept and effects

Water influx amount ratio

Figure 5 shows a sealed-type bearing for work rolls aswell as the concept and effects of oil seal development.
We succeeded at developing a high-performancesealed-type bearing for work rolls by leveraging thesynergistic effects of the developed oil seal and interinner ring seal.
①Improved robustness through enhanced sealability
Succeeded in reducing water influx into the bearingby over 70% compared to the conventional product,thus minimizing sudden bearing failure caused bydeteriorated lubrication (Fig. 6).
1.0
0.8
0.6
0.4

Reduced water
influx by over 70%

0.2
0Conventional
product

Developed
product

Fig. 6 Water influx test result② Extended the applicable scope of conventional

material (NBR: nitrile rubber)Through reducing lip temperature rise by around
30% of the conventional product, we have extended
the applicable scope of NBR as material for the oil
seals of rolling mill bearings within the operating
temperature range of common NBR (Fig. 7).

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Lip temperature, ℃⑵Features

160
140
120
100
80
60
40
20
0

Reduced lip temperatureby around 30%

Conventional
product

Developed
product

Fig. 7 Temperature increase test result

2. 3 Development of the Oil/air Lubrication System
In recent years, there has been growing demands forsteel production equipment to offer stable operation andenvironmental-friendliness. As such, there is a constant
expectation to improve the lubrication of steel production
equipment. One countermeasure is oil/air lubrication.
JTEKT began mass production of the oil/air lubrication
system in 1994 and, since then, has accumulated a strong
track record of applications in bearings for various
steel production equipment, such as continuous castingmachines, hot and cold rolling mills. As a result, JTEKT
is contributing to our customers’ stable operations as asystem supplier of oil/air lubrication systems, bearings,
oil seals and bearing housings.
⑴Principle and features of oil/air lubrication
Figure 8 shows the transport principle of oil/air
lubrication while Fig. 9 shows the basic layout. Oilinside the pipe is transported to the final lubrication pointby the friction force of compressed air. Also, there isminimal discharge of oil mist that does not contributeto lubrication, therefore oil consumption is minimized.
Moreover, because compressed air, which is the force thattransports the oil, is supplied to the bearing, the interiorof the bearing has positive pressure, preventing influx of

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−Development of Technologies Contributing to the Stable Operation of Steelmaking Steel Production Equipment−

foreign matter from outside of the bearing.

used to replace grease lubrication on continuous castingmachines.
■Application to steel rolling equipment①Easy to design piping through adopting small-Compressed air(continuous supply)

Continuous flow of oil istransferred as waves

Fig. 8 Transport principle of oil/air lubrication

JTEKT’s oil/air lubrication system offers our customers
the below benefits.
①Significant improvement of wear and failure in harshenvironments
・High sealability through positive pressurization of
the bearing housings
・High lubrication performance through theapplication of high-viscosity oil and extremepressure oil②Improvements in equipment maintenance・Improved operating costs through lubrication withminimal oil
・Improved environment surrounding equipment
due to oil recovery③Easy application
・Easy to design piping through adopting smalldiameter pipes
・System design with a high-degree-of-freedom
from minimal to numerous oil supply points⑵Applications
The below section introduces cases where thelubrication method was changed from oil mist to oil/air
for steel rolling equipment, and oil/air lubrication wasdiameter pipes②Reduction of running costs (one-third of oil mist

lubrication)③High lubrication performance through the applicationof high-viscosity oil and extreme-pressure oil
Figure 10 shows the consumption ratio of oil mist
lubrication and oil/air lubrication.

Oil consumption ratio

Oil (intermittent supply)

4
one-third
consumption ratio

3
2
1
0

Oil mist lubrication

Oil/air lubrication

Fig. 10 Lubricant consumption amount■Application for continuous casting machines①Significant reduction of wear specific to self-aligningroller bearings (one-tenth of grease lubrication)②Reduction of bearing replacement frequency caused

by wear, flaking and rust
③Reduction of sudden incidents through longer life

bearings④Reduction of man-hours required for bearing
washing during maintenance work
Figure 11 shows the race wear ratios of greaselubrication and oil/air lubrication.

Oil/air distributor
Mixing device

Oil/air

Bearing
housing
Dry air

Air unit
Air
Oil
Recovery tank unit

Example of oil/air lubrication device structure

Pump unit
Control unit
Main unit

Fig. 9 Basic layout for oil/air lubrication

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−Development of Technologies Contributing to the Stable Operation of Steelmaking Steel Production Equipment−

Race wear ratio

12
10

Wear ratio of one-tenth or less86

3. 1 Introduction of an Actual Size Testing Machine420bearing interior and operating conditions, then propose
optimum bearing design to our customers.

GreaseOil/air

Fig. 11 Comparison of bearing wear amounts⑶Development of a multi-point oil supply distributor

Furthermore, amongst the various types of steel
production equipment, equipment with a high number ofoil supply points such as continuous casting machinesentails issues such as the number of pipes and securing
space for various devices. In order to solve this issue,
JTEKT has developed a block-type distributor able
to distribute oil/air to multiple points (Fig. 12), thus
simplifying equipment. The developed product has nomoving parts, therefore can distribute oil in an oil/air state
in many directions, enabling installation in environments
subjected to heat and water.

Previously, it was extremely difficult to reproduce
the severe conditions of actual equipment in a bench
testing machine. As such, it was difficult to evaluate large
bearings at actual size therefore the common practice wasto make evaluations using scaled-down bearings. In recent
years, there have been growing requests to evaluate thevarious actual size bearings, therefore, JTEKT introduced
the bearing testing machine for steelmaking equipment
as shown in Fig. 13. This testing machine is capable ofreproducing the various environmental conditions ofan actual machine, such as rolling water scatter, hightemperature, high speed and high load.
This testing machine can accommodate an actual
size bearing used on a rolling mill, the main piece ofequipment used in steel mill, making it the world’s
first testing machine to enable evaluation under actual
equipment operating conditions. This section introducescases of using this testing machine to measure load
applied to actual size bearings.

Fig. 12 Block-type oil/air distributor

Furthermore, we also support constant management
systems in regards to oil/air lubrication through the useof a monitoring panel which enables the visualization ofoperational status. JTEKT is further advancing the oil/air
lubrication as a means of lubricating the bearings usedin steel production equipment with the aim of offeringengineering solutions including peripheral devices suchas bearings, oil seals and bearing housings.

3. Initiatives for Longer Life Bearings
through Bearing Diagnosis
In steel mill equipment, bearings can be subjected toload unforeseen at the design stage. Some feasible causesof load are factors relating to operational status andfactors relating to equipment aging, however measuringload on the actual equipment is effective in identifying
the true cause of load. JTEKT wishes to leverage its
independent load measurement and analysis technologies
to ascertain the relationship between the load status of the32

Fig. 13 Bearing test rig for steelmaking equipment

3. 2 Measurement of Rolling Element Load for a
Radial Bearing
Generally, four-row tapered roller bearings are used asradial bearings for work rolls. Focusing on the fact that
this bearing uses a hollow rolling element, we attacheda strain gauge to the inner face of this hollow rolling
element and measured the load that occurred. However,
initial calibration between rolling element load andstrain value was performed on a single row tapered roller
bearing under axial load condition.
Figure 14 gives an overview of the method used tomeasure rolling element load. The output of the strain
gauge attached to the interior of the hollow rolling
element is recorded in an ultra-small data logger
integrated with the rolling element through a fixture,then, after measurement, data is removed with the bearing

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−Development of Technologies Contributing to the Stable Operation of Steelmaking Steel Production Equipment−

in a static state, and analyzed. Examination of load is
performed by applying only pure axial load in a vertical
test rig and correlating the rolling element load and strain.

Gauge lead wire

Rolling element (hollow)
Strain gauge

Cage
View A

Strain gauge
Logger holder

Ultra-small
data logger

Fig. 16 Measurement method of axial load
View A: Logger photoFig. 14 Summary of measurement method of rolling element
load

Regarding rolling element load, Fig. 15 shows acomparison of results measured on the testing machineand results calculated from FEM analysis. We confirmedthat rolling element load distribution is bimodal due tothe effect of housing rigidity and that the measured load
distribution and load distribution value obtained throughFEM analysis has good consistency. JTEKT utilizes thismethod to measure the radial load of work roll bearings
on actual equipment.

strain in advance.
Figure 17 shows the measured waveform for fixedring strain. From the measurement result, we were able
to measure the axial load from the P-P waveform of therolling element passing frequency of each row. This result
was consistent with the result of the testing machine
input load, thus we were able to confirm the reliabilityof the measurement method, and that actual equipment
measurement is an extremely effective measurement
method.

Simple analysis(bearing only)

Measured value

Roller load, kN

300

Strain, le

P1−P1
FEM analysis value (bearing + bearing housing)

P2−P2

200
600 602 604 606 608 610 612 614 616 618 620
100
0Time, sec

Fig. 17 Measurement results of strain amount
0

90
180
270
Circumferential position, °360

Fig. 15 Comparison between measured and analysis value ofrolling element load

3. 3 Measurement of Axial Load for a Thrust
Bearing
Thrust bearings have a large contact angle which makes
mounting of the abovementioned small logger difficult.
As such, we machined a notched groove on the outer ring,which is the fixed ring, mounted a strain gauge to thisgroove, then performed measurement by detecting thestrain on the fixed ring when the rolling element passed
the notched groove on the outer ring.
Figure 16 shows the method used to measure axial
load. Examination of load is performed in the same way
as with the abovementioned radial bearing, by applying
only pure axial load in a vertical test rig and preparinga relationship diagram for the rolling element load and

JTEKT ENGINEERING JOURNAL English Edition No. 1016E (2019)

This time, in a testing machine for steel mill equipment,
we were able to confirm the effectiveness of the radial
and axial load measurement method used on actual size
bearings. In addition to these measurement technologies,
by combining temperature and vibration measurement,
we can achieve visualization of the bearing operating
status under actual equipment conditions.
Leveraging our proven track record of performing
multiple measurements using this technology, JTEKT
wishes to continue load measurement on our customers’
actual equipment and offer a technical service to solve
customer concerns. Moreover, in addition to achieving
optimum design of bearings for steel production
equipment based on the data obtained here, we would
also like to offer a service for monitoring the operational
status of steel mill equipment.

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−Development of Technologies Contributing to the Stable Operation of Steelmaking Steel Production Equipment−●Crowning of outer ring O.D.

Without crowningWith crowning↓Distribution of outer ring O.D. contact
stress not damaging the intermediate rollIntermediate roll
Bearing O.D.

●1 High-accuracy thickness of the multiple bearings used on the shaft
Mutual error of assembled thickness of all bearings used on 1 axis≦0.006mm
Mutual error of assembled thickness ofbearings used on adjacent bearing≦0.002 mm

Shaft

Backup roll bearing

Fig. 18 The backup rolls bearings of multi-roll millsi) Re-grinding

4. Initiatives for Long-term Stable Usethrough Appropriate Repairs
For many years, JTEKT has been offering customers
bearings and UJs for steel production equipment. Amidst
this, as initiatives to use our products for even longer, weoffer proposals for the establishment of a maintenancesupport system for rolling mill bearings and repair method
for the UJ main unit. The details of these initiatives are
introduced in the following sections.

ii) Crowning

Fig. 19 Re-grinding support
Bearing

4. 1 Establishment of a Maintenance Support
System for Multistage-type Rolling Mill
Bearings⑴Required bearing performance

As seen in Fig. 18, several of the backup roll bearings
used in multi-roll mills are mounted on one shaft, thebearing outer diameter makes direct contact with theintermediate roll, and the outer ring rotates while being
subjected to rolling force load. As such, the outer ringshould have sufficient rigidity and be strong against
rolling fatigue, in addition to offering a high-accuracy
finish.
This bearing is required to exhibit the below
performances.
①Crowning of outer ring outer diameter
Crowning considering contact stress distribution is
performed on the outer diameter of the bearing outerring in order to prevent damage to the intermediateroll caused by concentrated load on the edges(Fig. 18).

[Measurement device in isolation]・High-accuracy measurement of bearing thickness

Fig. 20 Device for measuring thickness
Bearing[Fixture in isolation]・High-accuracy grinding of the outer diameter of the bearing outer ring

Fig. 21 Polishing jig

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JTEKT ENGINEERING JOURNAL English Edition No. 1016E (2019)

−Development of Technologies Contributing to the Stable Operation of Steelmaking Steel Production Equipment−②High-accuracy thickness and rotational accuracy ofthe numerous bearings used on one shaft
In regards to the high-accuracy thickness androtational accuracy of bearings, optimum contact
stress distribution is achieved in order to prevent
damage to the intermediate roll (Fig. 18).
⑵Establishment of a maintenance support system
When our customers re-grind the outer diameter of the
bearing outer ring as part of maintenance work, JTEKT
first measures the half-value width using X-ray diffraction
then proposes optimum grinding amount (Fig. 19). We
also provide maintenance tools for our customers to use(Fig. 20). This contributes to stable operation and reduced
maintenance man-hours of our customers.
Moreover, we have established a system whereby
JTEKT collects the bearings with outer diameters regrinded by customers, confirms quality, then re-delivers(Fig. 21).

4. 2 Initiatives for Rolling Mill Universal Joints
The universal joints (UJ) that drive rolling mill rolls
have an extremely high torque load and are limited insize due to equipment space limitations. As such UJs areoften used in operating regions with high loads relative
to their load capacity. JTEKT has proactively engagedin efforts to increase UJ capacity, and by implementing
the countermeasure shown in Fig. 22, achieved the
major accomplishment of improving fatigue limit torque.
Moreover, regarding response to excessive torque,
we developed the Hyper Coupling as a product that
instantly releases the torque transfer working on UJs
and are building up our track record with this (Fig. 23).
The preceding sections of this paper have introduced
initiatives to improve UJ strength and life, however
maintenance for environmental and aging-related changes
is also an important issue.
In the past, we performed inspections and repairs uponreceiving requests from customers, however we believe
we can contribute to stable operations by establishingregular maintenance through sharing of customer
maintenance plans and UJ repair history. As such, JTEKT
engages in the following activities.
⑴Strengthening of UJ inspection/repairs acceptancesystemFigure 24 shows the UJ repair system chart. It
proposes strengthening of inspection/repair acceptanceand an efficiency maintenance cycle.
⑵Formation of a repair performance database
JTEKT has conducted a high number of repairs so
we are able to utilize such performance data to proposea suitable time for consumable part replacement, andmaintenance work content. We will propose maintenancemanagement by individual parts based on a database of
repairs performed at our customer’s site.

JTEKT ENGINEERING JOURNAL English Edition No. 1016E (2019)⑶Development of a history management method

To date, the following issues have prevailed.
①It was difficult to confirm product history after actual
equipment usage.
Conventionally, product history was confirmed
by scanning the product number or serial number
stamped into the product surface however scanningwas difficult due to the build-up of dust after usage
and dust removal required a high number of manhours.
②Repair history management was not being achieved.
The history of products themselves, such as periodic
repairs, etc. was not being maintained.
To solve these issues, we introduced a producthistory management system adopting RFID tag* andthis is introduced in Fig. 25.
This system enables product history to be confirmed
easily and swiftly. Moreover, it is easy to register repair
history and usage history, therefore history management
is also easy, which can help predict product life andreplacement timing.
*RFID tag: A system for the non-contact reading andwriting of data saved on an RF tag using
electromagnetic waves.
Bearingcup ⑵Cross ⑷Bearing fixation
bolt ⑴
Yoke

Bolt strength Flaking life
improvement improvement

Roller ⑶Description
Rolling of the fixation bolt thread

⑴

○

−

⑵

○

○

Spraying of the bearing cup key

⑶

−

○

Adoption of bearing portion with varying-diameter rollers

⑷

−

○

Varnishing of the cross race

Fig. 22 Proposal for improving fatigue strength

Fig. 23 Device for releasing excess load: Hyper Coupling35

Customer−Development of Technologies Contributing to the Stable Operation of Steelmaking Steel Production Equipment−

Maintenance activity

Inspection/repair

Sudden failure response

Productivity improvement
activities

Increased rolling load

Operability improvement

Stable operation, reduced maintenance cost, efficient maintenance work
Inspection
Operation

Equipment
introduction

Inspection

Operation

Operation

Technological support for stable operation
Proposal of an efficient maintenance cycle

Provision of maintenance technologies

JTEKT◎Proposal of daily inspection items and inspection repair cycle◎Technical proposals for sharing drive shaft usage status◎Minimization of sudden costs through proposing periodic repairs
Proposal of high-functionality items◎Presentation of drive shaft technologies◎Trouble shooting◎Maintenance attendance
Added-value products◎Proposal for longer life and increased strength・Varnishing
・Varying-diameter rollers
・Bolt rolling, etc.
◎Improved corrosion resistance・Tungsten carbide spraying ・SUS build-up welding, etc.

◎Hyper coupling◎History maintenance by RFID tag

Fig. 24 UJ repair system chart

Bearing cups

JTEKT drive shaft

Roller guideOil seal

Thrust washer
Rollers

Cross
Slinger

ReaderUHF band RFID metal support tag[Dimensions: 10 × 39 × 2.9mm][Current]

Bearing fixation
bolt
Yoke

[Improved]

Stamp

RFID tag

Serial number was engraved (stamped) on outer periphery→After use, scanning was difficult due to dust, etc.

Product history can be confirmed
by scanning with the reader

Fig. 25 Product history management system

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−Development of Technologies Contributing to the Stable Operation of Steelmaking Steel Production Equipment−

5. Conclusion
JTEKT has contributed to the stable operations ofsteel production equipment for many years by providing
products such as bearings, oil seals and universal joints.
Moreover, as indicated in this report, in recent years there
has been a focus not only on product technology, but also
the shift from “mono” to “koto”, with some examples
being ①development of lubrication technologies suchas lubrication devices ② optimized bearing design
through bearing diagnosis using actual equipment, and ③
appropriate repair methods to ensure long-term productuse. JTEKT wishes to continue exerting efforts towards
the development and provision of new products to suitmarket trends aimed at the stable operations of steel
production equipment, and the relevant services thereof.
*1 JHS is a registered trademark of JTEKT Corporation.

References
1)
2)
3)
4)
5)

K. SAMESHIMA: Koyo Engineering Journal, No. 163E
(2003) 17.
A. NAGAYAMA: Koyo Engineering Journal, No. 166E
(2005) 7.
R. HOSAKA, N. YASUDA: JTEKT ENGINEERINGJOURNAL, No. 1004E (2008) 42.
A. NAGAYAMA, T. MIYACHI: JTEKT ENGINEERINGJOURNAL, No. 1004E (2008) 77.
J. KUBO, M. KAWATA: JTEKT ENGINEERINGJOURNAL, No. 1012E (2015) 43.

A. NAGAYAMA****JTEKT ENGINEERING JOURNAL English Edition No. 1016E (2019)

T. MIYACHI*

K. OTSUKA**

Industrial Machinery Application Engineering Dept.,
Bearing Operations Headquarters
Experiment & Analysis Dept., Bearing Operations
Headquarters

37