CHARMEC project SP13 Alarm limits for wheel damage / Larmgränser för hjulskador Jens Nielsen, Anders Ekberg & Elena Kabo Chalmers University of Technology, Department of Applied Mechanics/CHARMEC SE-412 96 Göteborg, Sweden Presentation of SP13 at CHARMEC seminar 7917 1
Current wheel damage criterion 29 kn ~ flat length 4 6 mm Action: stop at nearest station to repair/replace damaged wheel temperature < -1 C : train speed < 1 km/h temperature > -1 C : avoid 15 km/h < train speed < 45 km/h 3 kn ~ flat length > 6 mm Action: stop at nearest station to repair/replace damaged wheel train speed < 1 km/h From: www.sweller.dynalias.org/estar/ Presentation of SP13 at CHARMEC seminar 7917 2
heel impact load detector on Malmbanan Monthly statistics (June 2 May 3) of number of trains with at least one wheel exceeding a certain load magnitude ILD in Harrträsk on the southern route of Malmbanan (axle load 3 tonnes) Presentation of SP13 at CHARMEC seminar 7917 3
Field test on Svealandsbanan Spring on Svealandsbanan Presentation of SP13 at CHARMEC seminar 7917 4
Field test on Svealandsbanan Spring on Svealandsbanan Measurement of frequency response functions in track heel impact load detector based on strain gauges Measurement of strains in rails and sleepers Presentation of SP13 at CHARMEC seminar 7917 5
Field test on Svealandsbanan Spring on Svealandsbanan Measurement of frequency response functions in track heel impact load detector based on strain gauges Measurement of strains in rails and sleepers Train speeds 3 1 km/h Loaded and unloaded wagons Presentation of SP13 at CHARMEC seminar 7917 6
Field test on Svealandsbanan Spring on Svealandsbanan Measurement of frequency response functions in track heel impact load detector based on strain gauges Measurement of strains in rails and sleepers Train speeds 3 1 km/h Loaded and unloaded wagons heel defects - natural and manufactured flats 4 and 1 mm - 4 and 1 waves around circumference - long local defects Presentation of SP13 at CHARMEC seminar 7917 7
Field test on Svealandsbanan Measured bending moments in the rail Axle loads 24 3 tonnes, train speed 1 km/h heel flat hits above channel 19 (at approximately t = 3 s) CS643 1 km/h - över sliper CS643 1 km/h - mellan sliper Kanal 18 [knm] - 2 3 4 5 6 Kanal 19 [knm] - 2 3 4 5 6 Kanal [knm] - 2 3 4 5 6 Kanal 23 [knm] - 2 3 4 5 6 Kanal 22 [knm] - 2 3 4 5 6 Kanal 25 [knm] - 2 3 4 5 6 Presentation of SP13 at CHARMEC seminar 7917 8
Kanal 2 [kn] Field test on Svealandsbanan Kanal 19 [knm] Kanal 23 [knm] Measured contact force and bending moments in the rail Axle loads 24 3 tonnes, train speed 1 km/h heel flat hits above channel 19 (at approximately t = 3 s) Distance between channels 19 and 23 1.3 m CS643-1 km/h 25 15 1 5 2.75 2.8 2.85 2.9 2.95 3 3.5 3.1 3 1-1 2.75 2.8 2.85 2.9 2.95 3 3.5 3.1 1-1 - 2.75 2.8 2.85 2.9 2.95 3 3.5 3.1 Maximum rail bending moment : Tension in rail foot Presentation of SP13 at CHARMEC seminar 7917 9
Kanal 2 [kn] Field test on Svealandsbanan Kanal 19 [knm] Kanal 23 [knm] Measured contact force and bending moments in the rail Axle loads 24 3 tonnes, train speed 1 km/h heel flat hits above channel 19 (at approximately t = 3 s) Distance between channels 19 and 23 1.3 m CS643-1 km/h 25 15 1 5 2.75 2.8 2.85 2.9 2.95 3 3.5 3.1 3 1-1 2.75 2.8 2.85 2.9 2.95 3 3.5 3.1 1-1 - 2.75 2.8 2.85 2.9 2.95 3 3.5 3.1 Minimum rail bending moment : Tension in rail head Presentation of SP13 at CHARMEC seminar 7917 1
Validation of train track interaction model L a L b L a M w k w c w m w F z L s v l d k b c b Vehicle model with four wheelsets heel flat with length 1 mm and depth.9 mm (axle load 24 tonnes) Compare measured data with simulated results k p c p 25 Maximum contact force Svealandsbanan - HAB638 4 Maximum rail bending moment Svealandsbanan - HAB638 Minimum rail bending moment Svealandsbanan - HAB638 35 18 Kontaktkraft mellan hjul och räl [kn] 15 1 5 1 3 4 5 6 7 8 9 1 Hastighet [km/h] Största böjmoment i räl [knm] 3 25 15 1 Mätdata 5 DIFF: 4 hjulpar DIFF: 4 punktlaster 1 3 4 5 6 7 8 9 1 Hastighet [km/h] Minsta böjmoment i räl [knm] 16 14 12 1 8 6 4 Mätdata 2 DIFF: 4 hjulpar DIFF: 4 punktlaster 1 3 4 5 6 7 8 9 1 Hastighet [km/h] Presentation of SP13 at CHARMEC seminar 7917 11
orst load case - strategy Rail bending moment is influenced by the impact load magnitude but also by train speed, frequency content of load, track properties, axle load, axle distance Given the magnitude of the impact load, search for worst load cases with respect to the impact load time history Focus on Malmbanan: 3 tonnes and 6 km/h F max F z,1 F max F z,2 F min T 1 T 2 T 3 T 1 T T 2 T 3 L a L b L a F z,i (t ) k b c b L s k p c p Presentation of SP13 at CHARMEC seminar 7917 12
orst load case: influence of time history 1(2) Minimum bending moment (-.1 knm) for F min = kn (low level), T 1 = 2 ms (low), T 2 = 1 ms (low) och T 3 = 4 ms (high) The influence of T 2 is high Minimum moment for fast impulse and slow unloading F max F z,1 F max F z,2 22 F min T 1 T 2 T 3 L a L b F z,i ( L a t) L s k b c b T 1 T T 2 T 3 Minsta böjmoment i räl [knm] 21 19 18 17 4 3.5 3 T 1 [ms] 2.5 2 3 2.5 2 1.5 T 2 [ms] 1.5 k p c p Input: F max = 29 kn, 3 tonnes, 6 km/h, axle distance 1.78 m Presentation of SP13 at CHARMEC seminar 7917 13
orst load case: influence of time history 2(2) Maximum bending moment (53. knm) for T = 6 ms (high level), T 1 = 2 ms (low), T 2 = 2 ms (medium) och T 3 = 4 ms (high) Maximum moment for slow impulse and slow unloading F max F z,1 F max F z,2 54 F min T 1 T 2 T 3 L a L b F z,i ( L a t) L s k b c b T 1 T T 2 T 3 k p c p Största böjmoment i räl [knm] 52 5 48 46 5 4 T 3 [ms] 3 2 1 1.5 2 T 2 [ms] 2.5 3 Input: F max = 29 kn, 3 tonnes, 6 km/h, axle distance 1.78 m Presentation of SP13 at CHARMEC seminar 7917 14
orst load case: influence of load position For an initial rail foot crack, the worst load position is directly above the crack The worst position for an initial rail head crack is above a sleeper, and when the load position is 1.5 sleeper distances away (half axle distance) F max F z,1 F max F z,2-8 6km/h, Fmax 29kN, Fmin kn, T1 2ms, T2 1ms, T3 4ms F min T 1 T 2 T 3 L a L b F z,i ( L a t) L s k b c b T 1 T T 2 T 3 k p c p Min böjmoment i räl vid sprickposition [knm] -1-12 -14-16 -18-8/8-22 -5-4 -3-2 -1 1 2 3 4 5 6 7 8 Antal sliperavstånd mellan position för hjulplatta och sprickposition [-] Input: F max = 29 kn, 3 tonnes, 6 km/h, axle distance 1.78 m /8 2/8 4/8 6/8 Presentation of SP13 at CHARMEC seminar 7917 15
Böjmoment i räl över sliper [knm] Böjmoment i räl över sliper [knm] 24 22 18 Influence of support stiffness Rail bending moments increase with decreasing rail pad stiffness The influence of ballast stiffness is not so high unless sleepers are hanging from the rail (not supported by ballast) Input: UIC6 rails and worst load case with respect to time history and striking position kp 8 MN/m kb 1 MN/m kb 5 MN/m kb 15 MN/m kb MN/m 16 25 26 27 28 29 3 31 3 33 34 35 Max kontaktkraft [kn] kb 1 MN/m 25 15 kp 8 MN/m kp 16 MN/m kp 24 MN/m kp 3 MN/m 1 25 26 27 28 29 3 31 3 33 34 35 Max kontaktkraft [kn] Böjmoment i räl över sliper [knm] Böjmoment i räl mellan sliprar [knm] 26 24 22 kb 1 MN/m, kp 8 MN/m Ingen hängande sliper En hängande sliper 18 25 26 27 28 29 3 31 3 33 34 35 Max kontaktkraft [kn] kb 1 MN/m, kp 8 MN/m 1 1 8 6 Ingen hängande sliper Två hängande sliprar 4 25 26 27 28 29 3 31 3 33 34 35 Max kontaktkraft [kn] Presentation of SP13 at CHARMEC seminar 7917 16
Stress intensity factors Bending of the rail gives a stress history in the top of the rail head and the bottom of the rail foot In the presence of a crack, this stress can be translated to a stress intensity factor In addition a temperature below the stress free temperature will cause additional tensile loading K I = f(a) σ πa a f σ where is the crack size is a geometry/loading factor is the stress magnitude Crack growth occurs if K I = K Ith and fracture if K I = K Ic
Geometry / loading Two types of cracks head crack edge foot crack factor Two load types bending (impact load) tensile (temperature) (a-d) symmetry (e) clamped (a) (d,e) contact load crack Two rail types UIC6 BV5 a (c) (b) residualstresses bendingmoment temperatureload
Fracture criterion Super-position of bending and tension (in the same mode) gives a fracture criterion as K Ib + K It K Ic Re-arrange: K Ib K Ic K It Note K I σ K I [MPa m] fotspricka a =.1 m 55 5 45 4 35 3 25 K I (F z ) K Ic ( grader) K Ic ( grader) K Ic ( 4 grader) 15 25 3 35 Max kontaktkraft [kn] UIC 6
Results Stress intensities for head cracks from FEsimulations BV5 probably less reliable than UIC6 Stress intensities for foot cracks from standard cases Bending less reliable than tension K I [MPa m] UIC6 BV5 Head 25 mm 12 1 Head 4 mm 21 16 Foot 5 mm 22 Foot mm 45 48 Stress intensities for a vertical impact load of 3 kn
Results Method to evaluate influence of vertical impact load and temperature loading for given crack size Inspection tolerances? Crack growth rates? Fairly low influence of vertical load as compared to temperature load in the studied interval Regional restrictions? Seasonal restrictions?
Goal Determine a i, f 1 a c a c /f 2 Determine operational loads and material parameters for crack growth Determine critical loads and C, m da/dn f 2 a c, Set inspection intervals crack size a i /f 1 a i t i time t i +2 t Idealised sketch on how to define inspection intervals
Future studies Different kinds of traffic Crack growth rates Further studies of track geometry influence and hanging sleepers Improved analysis of stress intensities (rail profiles, lateral bending, different locations, residual stresses, etc)