Flange Climb Derailment Criteria and Wheel/Rail Profile Management and Maintenance Guidelines for Transit Operations (2005) / Chapter Skim
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Appendix B - Investigation of Wheel Flange Climb Derailment Criteria for Transit Vehicles (Phase I Report)
Appendix B - Investigation of Wheel Flange Climb Derailment Criteria for Transit Vehicles (Phase I Report)
Pages 77-115
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From page 77... ...
B-1 APPENDIX B: Investigation of Wheel Flange Climb Derailment Criteria for Transit Vehicles (Phase I Report)
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From page 78... ...
This research has been based on the methods previously used by the research team to develop flange climb derailment criteria for the North American freight railroads. The following conclusions are drawn from single wheelset and vehicle simulations: • New single wheel L/V distance criteria have been proposed for transit vehicles with specified wheel profiles: Wheel 1 profile: Wheel 2 profile: Wheel 3 profile: L/V Distance (feet)
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From page 79... ...
• The distance required for flange climb derailment is determined by the L/V ratio, wheel maximum flange angle, wheel flange length, and wheelset AOA. • The flange climb distance converges to a limiting value at higher AOAs and higher L/V ratios.
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• At high speed, the climb distance increases with increasing wheelset rotating inertia. However, the effect of inertial parameters is not significant at a low nonflanging wheel friction coefficient.
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The proposed L/V and distance-to-climb criteria were developed for freight cars with an AAR1B wheelset with a 75-degree flange angle. These were developed based on fitting L/V and distance-to-climb curves to numerous simulations of flange climb derailment.
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From page 82... ...
The purpose of this project was to use similar analytical methods to develop flange climb derailment safety criteria, specifically for different types of transit systems and transit vehicles. The research team undertook a program of developing wheel/rail profile optimization technology and flange climb criteria at the request of the NCHRP.
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From page 83... ...
1.3 METHODOLOGY 1.3.1 Single Wheelset Flange Climb Derailment Simulations The effects of different parameters on derailment were investigated through single-wheelset simulation. Based on these simulation results, the L/V ratio and climb distance criteria for six different kinds of transit wheelsets were proposed.
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From page 84... ...
1.3.2 Vehicle Derailment Simulations As a preliminary validation of the proposed flange climb derailment criteria, three hypothetical passenger vehicles representing heavy rail and light rail transit vehicles were B-9 modeled. The vehicle models included typical passenger car components, such as air bag suspensions, primary rubber suspensions, and articulation joints.
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to the point of derailment. For the purposes of Parameter Wheel 1 Wheel 2 Wheel 3 Wheel 4 Wheel 5 Wheel 6 Maximum Flange Angle (degree)
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From page 86... ...
As shown in Figure B-5, the flange length is defined as the sum of the maximum flange angle arc length QP and flange tip arc length PO. 2.1.2 Effect of Wheelset AOA Figure B-6 shows the effect of AOA on wheel flange climb for Wheel 1 for a range of wheel L/V ratios.
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From page 87... ...
Low friction on the nonflanging wheel therefore represents the worst-case condition resulting in the shortest distances for flange climb. Thus, to produce conservative results, most of the single wheelset derailment simulations discussed in this report were performed with a very low nonflanging wheel friction coefficient (0.001)
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From page 88... ...
. Compared to the low-flange-angle wheelset, the high-flange-angle wheelset requires greater effort to climb over the maximum flange angle and travels a farther distance at the same base L/V level.
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(B-3) Equations B-1 and B-3 are Nadal's limiting value for Wheel 1, which has a flange angle of 63 degrees.
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0.13 * AOAe 1 < + 5 AOAe if degree and AOAe= < >C C C, 5 B-15 because both wheels have the same 63-degree maximum flange angle.
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2.3 TRANSIT VEHICLE WHEELSET 3 Figure B-20 shows the effect of wheelset AOA on flangeclimb distance for a range of Wheelset 3 flanging wheel L/V ratios. The Nadal L/V flange climb limit is shown as a dashed line.
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The Nadal L/V flange climb limit is shown as a dashed line. Coefficient of friction on the flanging wheel was 0.5.
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Figure B-27 shows the effect of the nonflanging wheel friction coefficient µnf for the independent rotating Wheelset 5, with a flanging wheel friction coefficient of 0.5 and a 5-mrad wheelset AOA. In contrast to the situation of the conventional solid wheelset, when µnf = 0.001, 0.3, 0.5, and 0.8, the longitudinal creep forces on both wheels vanish as expected.
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Figure B-29 shows the effect of wheelset AOA on wheel flange-climb distance for a range of Wheelset 6 flanging wheel L/V ratios. The Nadal L/V B-19 flange climb limit is shown as a dashed line.
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. When the wheel climbs above the maximum flange angle, the wheel contacts the rail at the flange tip and begins the second climbing phase, with the contact angle reducing as the climb continues.
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Based on the above analysis, the wheel-climb distance is controlled by both the wheel/rail contact angle and the flange length, which includes the maximum flange angle length and the flange tip length. At a low AOA (<5 mrad)
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2.8 CONCLUSIONS FOR SINGLE WHEELSET SIMULATIONS Based on the single wheelset simulation results, wheel flange climb derailment criteria for transit vehicles have been proposed that are dependent on the particular wheel profile characteristics. The following conclusions can be drawn from the analyses performed: • New single wheel L/V distance criteria have been proposed for transit vehicles with specified wheel profiles: B-22 (1)
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From page 98... ...
• The distance required for flange climb derailment is determined by the L/V ratio, wheel maximum flange angle, wheel flange length, and wheelset AOA. • The flange-climb distance converges to a limiting value at higher AOAs and higher L/V ratios.
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These are validated in this section of this report. Three types of hypothetical passenger cars representing heavy rail and light rail transit vehicles have been modeled.
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The simulations were conducted for a range of speeds to generate a range of flange climbing conditions: • Contact with maximum flange angle but not flange climbing. • Flange beginning to climb up the rail but not derailing (incipient derailment)
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When the vehicle travels at speeds lower than 50 mph, the climb distance is less than or equal to the limiting value, the wheel climbs to the maximum flange angle, and the contact angle remains at 63 degrees (Figure B-48)
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Therefore, although both wheels have the same maximum flange angle, the safety margin for Wheel 2 is even smaller, and its derailment probability is significantly increased. The simulation results for the heavy rail vehicles assembled with two different types of wheel profiles confirm the methodology and criteria proposed for Wheel 1 and 2 in Chapter 2.
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This combination was applied to the middle truck on the articulation unit of the light rail vehicle. Both of these wheel profiles have identical shapes with a 75-degree flange angle.
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The wheel climbs onto the maximum flange angle and the contact angle stays at 75 degrees, as seen in Figure B-55. However, when the running speed is increased to 37 mph, the climb distance increases to 8.5 ft, which is over the limit value, and the wheel climbs over the maximum flange angle and reaches the flange tip between the distances of 581.7 and 582.3 ft.
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3.2.2.2 Low Floor Light Rail Vehicles Assembled with Solid and IRW Wheelset 3 The second set of simulations of the light rail vehicle Model 1 were conducted with Wheelset 3 on the end trucks and Wheelset 3 modified with independent rotating wheels on the center truck under the articulation unit. Simulation results show the following: • The third axle begins to climb at the location of 580 ft distance (distance referred to the third axle)
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3.3.2.1 High Floor Light Rail Vehicle (Model 2) Assembled with Wheelset 2 Simulation results show the following: • The first axle begins to climb near the location of 555 ft distance (distance referred to the third axle)
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When the vehicle travels at speeds lower than 30 mph, the climb distance is longer than the limiting value. The wheel climbs to the maximum flange angle face, and the contact angle stays at 63 degrees, as seen in Figure B-61.
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From page 108... ...
The simulation results also show that the proposed climb distance criteria for low-maximum-flange-angle wheelsets are conservative at low speeds. For the simulations shown, once the flange climb reached the maximum flange angle the AOA began to reduce for two reasons: • Increased rolling radius causes the wheelset to start steering back (this does not happen for the IRW)
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From page 109... ...
• The distance required for flange climb derailment is determined by the L/V ratio, wheel maximum flange angle, wheel flange length, and wheelset AOA. • The flange-climb distance converges to a limiting value at higher AOAs and higher L/V ratios.
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From page 110... ...
Based on the single wheelset and complete car simulation results, both the L/V ratio and climb distance converge to corresponding limit values when the wheelset AOA is over 10 mrad. Therefore, the 10-mrad AOA situation represents the most conservative case for wheelset climb derailment, which could be used as an alternative criterion for both tangent and curved track line cases together with the proposed criterion in this report.
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From page 111... ...
B-36 • Because the L/V ratios and the climb distance are sensitive to the wheelset AOA, further investigate the effect of variations of AOA during flange climb using simulations of both single wheelsets and full vehicles. • Further develop flange-climb-distance criteria to account for the effects of carrying friction coefficient.
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tan( ) δ µ µ δ1 The expression for the L/V ratio criterion is dependent on the flange angle δ and friction coefficient µ.
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From page 113... ...
The modified formulation is considered less conservative as it accounts for the presence of longitudinal creep forces that tend to provide a stabilizing effect to the wheel climb. Following the extensive tests of Reference 1, TTCI performed theoretical simulations of flange climb using the NUCARS model.
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For the asymmetric vehicle, the flange climbed 22 mm to the flange tip and then derailed.
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From page 115... ...
6. Weinstock, H., "Wheel Climb Derailment Criteria for Evaluation of Rail Vehicle Safety," Proceedings, ASME Winter Annual Meeting, 84-WA/RT-1, New Orleans, Louisiana, 1984.
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