Rail Profile Grinding on High-Hardness Premium Rail at the Facility for Accelerated Service Testing

U.S. Department
Of Transportation

Federal Railroad
Administration
RR08-19
July 2008

Rail Profile Grinding on High-Hardness Premium Rail at
the Facility for Accelerated Service Testing

SUMMARY
Since 2003, Transportation Technology Center, Inc. (TTCI) has been evaluating the effects of rail grinding
on the performance of high-hardness premium rail at the Facility for Accelerated Service Testing (FAST).
A 6-degree test curve is divided into three test sections, representing two different grinding practices, as
well as unground rail. There are three types of rail in each section—two of approximately 395 Brinell
hardness number (Bhn) and one approximately 370 Bhn. By the spring of 2007, 515 million gross tons
(MGT) of traffic had accumulated on the rails (Figure 1).

The following results, which are typical at FAST (revenue service conditions may differ), provide insights
into the effects of wheel/rail contact conditions and rail mechanical properties on rail performance.

State-of-the-art, high-hardness rail required little or no grinding. Unground rail developed only minor, isolated
rolling contact fatigue (RCF), and had no internal railhead defects. Because wheels on the test train at FAST
tend to wear to a shape conformal with the rail, and the gage face of the high rail and the top of the low rail are
lubricated, contact stresses remained acceptable throughout the test.
Compared to the unground rail, total metal loss in the preventive grinding zone was approximately 77-percent
higher on the high rail and approximately 240-percent higher on the low rail. The metal removed by preventive
grinding was the primary reason for the increase; wear rates were similar.
The 370 Bhn rail wore and deformed more than the 395 Bhn rails. The difference in wear was approximately
15 percent on the high rail.
A profile intended to produce higher contact stresses resulted in more RCF, but the RCF was not severe.
There is much less RCF on the low rail of the lubricated 6-degree curve, than there is on the low rail of the
unlubricated 5-degree curve at FAST.
Unrelated to rail grinding tests, there were six rail breaks originating at base defects in the 395 Bhn test rails.
No breaks were found in the 370 Bhn rail.


Figure 1. Condition of Unground Rails after 515 MGT
Low Rail (left), High Rail (right)

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US Department of transportation
Federal Railroad Administration Research Results RR08-19

BACKGROUND
8-inch crown radius on the low rail. Grinding
also removed surface damage such as RCF
Rail grinding tests at FAST have evaluated
cracks and spalls.
various grinding strategies, with metal removal
•
High-Contact Stress Zone: Intentionally
amounts and grinding intervals recommended by
grinding the rails to create a mismatch
railroad technical advisory groups (TAG).
between the rail profile and the average worn-
Variables that can affect defect occurrence in rail
wheel profile at FAST created a high-contact
can be controlled more easily at FAST than in
stress zone. TTCI’s proprietary WRTOL™
revenue service. These variables include rail
software was used to develop the ground rail
lubrication, wheel profiles, and train handling.
profiles that led to poor wheel/rail interaction.
The objectives of the rail profile grinding test at
WRTOL is a software package that assesses
FAST include evaluating the effect of various
wheel/rail contact conditions to predict RCF,
grinding practices on rail surface condition,
wheel/rail wear, and vehicle performance.
defect occurrence, wear life, and vehicle curving.
Principal outputs are contact stress, wheel

rolling radius difference, and contact angle. A
OBJECTIVES
database of typical wheel profiles at FAST
The rail profile grinding test evaluated the effects
was generated and compared to rail profiles at
of various grinding practices on premium rail.
FAST.
The test curve was divided into three zones,
• No Grind (control) Zone: This zone was not to
(Figure 2). Each zone represented one grinding
be ground unless it would compromise safety,
practice, and within each zone were three types
or necessitate the removal of the rail. The rail
of 141-pound (lb) rail:
was unground in 515 MGT of traffic.
• Nippon Steel Corporation

– High-carbon Hypereutectoid (HE) 400,
RESULTS
approximately 400 Bhn
• Rocky Mountain Steel Mills
The results of this test were consistent with the
– 1 percent Carbon Pearlite,
results of previous grinding tests on premium rail at
approximately 395 Bhn
FAST.1,2 Clean high-hardness premium rail is
• Rocky Mountain Steel Mills
resistant to RCF and to development of transverse
– Deep Head Hardened (DHH) 370,
defects. When adverse wheel profiles are avoided,
approximately 370 Bhn
and conditions that produce high vehicle dynamic
forces are addressed, the need for grinding can be

greatly reduced. Under the conditions at FAST,
METHODS
namely:
TTCI evaluated the following grinding practices:
•
Conformal, uniform wheel/rail contact
• Preventive Grind: The rail was ground at
conditions–no severely hollow wheels,
approximately 30 MGT intervals. An average
• Consistent, overbalance speed with limited
of 0.011 square inch of metal was removed
braking and acceleration,
from the high rail and 0.016 square inch from
• Lubrication on the gage face of the high rail
the low rail with the goal of producing a two-
and on the top of the low rail, and
point conformal profile on the high rail and an
• Dry climate.
Figure 2. Grind Test Layout
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US Department of transportation
Federal Railroad Administration Research Results RR08-19
The premium rails in the unground zone
metal removed by grinding far exceeded metal
developed only light, isolated RCF in 515 MGT of
loss from natural wear.
traffic, and there were no rail breaks initiating in the
head of the rail. Because it is difficult, if not
impossible, to achieve these conditions in revenue
service, rail grinding there can extend the life of
premium and standard rail.
Rail Conditions in the Preventive Grind Zone
The grinding in the preventive grind zone is similar
to what many railroads practice; i.e., light metal
removal at regular intervals, and was
recommended by the rail grinding TAG. This
grinding practice was effective in removing shallow
cracks and checks from the surface of the high rail.
The surface condition of that rail was better than
Figure 3. Total Metal Loss and Natural Wear
the high rails in the other two zones. On the low
in Ground and Unground Rail
rail, the 8-inch crown radius concentrated contact
in the center of the rail and resulted in slightly more

RCF than was observed on the unground low rail.
HE=Hyperevtectoid HCP=High Carbon Pearlitic DHH=Deep Head Hardened
Rail Breaks
There were no rail breaks initiating in the head of
the rail, but six breaks did initiate in the base of the
rail. These breaks are not related to grinding
practices, but noted here as they may be affected
by the mechanical properties of the rails. All six
breaks were in the higher hardness rails, and all
initiated mechanical damage at the base of the rail.
The mechanical damage was caused by
interaction between rails, tie plates, and fasteners
in all cases. Such damage is nearly unavoidable
during high tonnage, heavy axle load (HAL)
Figure 4. Metal Loss by Rail Type
operations. Previous tests have suggested that
Effects of High-Contact Stress Profiles
high hardness in the base of the rail may reduce
the toughness of the base and increase the
High-contact stress profiles were ground on both
likelihood of rail fractures initiating at mechanical
the high and low rails of one zone after 150 MGT.
damage.4,5
The upper gage corner of the high rail and the field
side of the top of the rail were heavily ground. This
Metal Loss
produced an exposed gage corner and a narrow
Total metal loss in the preventive grind zone was
contact band on the top of the rail. The field side of
approximately 77-percent higher than the
the top of low rail was heavily ground to narrow the
unground zone on the high rail, and approximately
contact band, and to move it toward the gage side
240-percent higher on the low rail (the high-contact
of the rail (inhibiting vehicle curving). Figure 5
stress zone is excluded because it is an atypical
shows profiles illustrating these grind patterns.
practice, and heavy metal removal was required to
These profiles were maintained when the rail was
achieve the desired profiles). The metal removed
ground at approximately 30 MGT intervals.
by grinding was the primary reason for the
WRTOL analysis of the modified profiles predicted
increase; natural wear rates were similar in the
an increase in contact stress and a concentration
unground and preventive grind zones (Figure 3).
of the stresses. The high rail of the high-contact
The DHH 370 rail showed slightly more metal loss
stress zone showed more RCF than the high rails
and more wear than the higher hardness rails.
of either of the other two zones, but did not
Figure 4 shows results for the high rail. There was
become problematic. The RCF was not on the
less difference on the low rail where the amount of
gage corner, but on the head of the rail. The low

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US Department of transportation
Federal Railroad Administration Research Results RR08-19
rail of the high-contact stress zone showed RCF
REFERENCES
similar to that in the preventive zone. The
1. Jimenez, Rafael and David Davis. January
presence of lubrication, as was on the gage corner
1999. “FAST Steel-Tie Test Update.”
of the high rail and the top of the low rail at FAST,
Technology Digest TD-99-015. Association of
can have a mitigating effect on RCF. A further
American Railroads, Transportation
illustration of this is a comparison of the condition
Technology Center, Inc., Pueblo, CO.
of the unground low rail in this curve, with that of
2. Kalay, Semih and Joseph LoPresti. December
the unground low rail in an unlubricated (but
2000. “Economics of Heavy Axle Loads:
contaminated) 5-degree reverse curve at FAST.
Predicted and Actual Benefits of HAL
The premium rail in the unlubricated curve
Operations.” AAR Research Report R-943.
developed significant RCF after 265 MGT. The
Association of American Railroads,
unground rail in the lubricated curve was in good
Transportation Technology Center, Inc.,
condition after 515 MGT. Other studies have also
Pueblo, CO.
shown that top of rail lubrication can reduce RCF.3
3. Reiff, Richard. June 2007. “Wayside-Based
Top of Rail Friction Control: 95 MGT Update.”

Technology Digest TD-07-019. Association of

American Railroads, Transportation
Technology Center, Inc., Pueblo, CO.
4. Kristan, Joseph. October 2005. “FAST Rail
Low Rail
Evaluation Test — Fracture Performance and
Discussion.” Technology Digest TD-05-024.
Association of American Railroads,
Transportation Technology Center, Inc.,
Narrow
Pueblo, CO.
contact band,
5. Kristan, Joseph, John Wedeking and Joseph
gage side
LoPresti. December 2005. “Rail Performance
Evaluation at FAST, October 2001 to May
2005.
Technology Digest TD-05-034.
High Rail
Association of American Railroads,
Transportation Technology Center, Inc.,
Pueblo, CO.
ACKNOWLEDGMENTS
Extreme two-point
contact, exposed
Rocky Mountain Steel Mills and Union Pacific for
gage corner
donating rail. And to UP for donating rail train.
CONTACT
Figure 5. High-Contact Stress Profiles
Len Allen

Federal Railroad Administration
Office of Research and Development
CONCLUSIONS
1200 New Jersey Avenue, SE
Clean high-hardness premium rail is resistant to
Washington, DC 20590
fatigue damage. With good wheel/rail contact
Tel: (202) 493-6356
conditions and rail lubrication, premium rail can
Fax: (202) 493-6333
provide hundreds of MGT of HAL service without
Email: Len.Allen@dot.gov
rail grinding. It is difficult, if not impossible, to
achieve this in revenue service, where rail grinding
KEYWORDS:
is successfully used to improve rail surface
Rail profile grinding
conditions and increase rail life.

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