UIC 518
Scope • Rules for conducting dynamic behaviour tests for • Safety • Track fatigue • Ride quality • Test on tracks matching actual service conditions • If actual conditions are better, use enhanced operating condition and vice versa
Field of Application • Tests to be carried out when • New vehicle /suspension • Redesigned suspension • Revised operating conditions • Additional requirements on specific cases like tilting (cant deficiency compensation) device on suspensions
Parameters Recorded • Wheel -rail level • Lateral Force • Vertical Force • Lateral acceleration • Lateral force at Axle box level • Bogie level lateral & vertical acceleration • Body level lateral & vertical acceleration • Equivalent conicity of wheel set
General Principles of Testing • Acceptance based on dynamic behaviour of line-test • On well-defined parameters related to • Track quality • Vehicle characteristics, incl max operating speed • Track Test zones • Tangent (straight) • Large-radius curve • Small curve
General Principles of Testing (contd.) • Measuring method • Normal-> rail-wheel interaction forces are recorded • Simplified-> rail-wheel forces and some other parameters are not recorded • Normal method for new vehicle • Detailed procedure for selection of parameters for simplified method depending on • Type of design/operational change • Type of vehicle
General Principles of Testing (contd) • Location/type of measurement on body and bogie depends on • For locomotive-> no of axles per bogie, type of service and speed • For coaches-> speed and bogie/non-bogie • For wagons-> no of axles per bogie • For dept vehicles-> special features
Running Test Conditions • All combinations of • Speed • Cant deficiency • Curve radius • Test zone • Number of sections • No overlap between sections • May or may not be juxtaposed sections
Test Zones • Min 25 sections of straight total length > 10 kms • Each section of 250m (±10%) for speed < 220 km/h • Large radius curve • Min 25 sections with cant <= 1.1* (max permissible cant) • Include min 10 sections of cant =1.1* (max permissible) • Total length >10kms • Each section of 100-500m depending on max speed • 10% higher than planned service speed
Test Zones (contd) • Small radius curve of radius between 400-600m, mean 500±50m, speed of 120- 80km/h • Min 50 sections of cant <= 1.1*(max permissible cant) • Include min 10 sections of cant = 1.1*(max permissible) • Each section of 100 m ±10% • Small radius curve of radius between 250-400m, mean 300m, speed of 120- 80km/h • Min 25 sections of cant <= 1.1*(max permissible) • Include min 5 sections of cant = 1.1*(max permissible) • Each section of 70 m ±10%
Test Zones (contd) • Transitions for all types of curves to be treated as separate section • Only one section per transition • Include all transitions of selected curves • Minimum total test zone length about 27 kms • Straight +large curve =10+10 = 20kms • Curve of 400-600 m radius =50*.9*100m = 4.5km • Curve of 250-400 m radius =25 *.9*70m = 1.575km • 4 transitions = 4*200m =.8 kms
Track Geometric Quality • Track geometry parameters • Unevenness • Alignment • Twist • Gauge • Track maintenance criteria limit for each of above • QN1, if exceeded-> monitoring/ regular maintenance • QN2, if exceeded-> short term maintenance • QN3, if exceeded-> undesirable/ unsafe
Track Geometric Quality (contd) • For track measuring (recording) cars • Speeds of 200km/h • Min wavelength 3m • Max wavelength 25 m • Track Quality based on • Standard deviation of both unevenness & alignment • Peak values for maintenance guidance and exclusion when QN3 limits are exceeded
Track Quality for Test Zone • Based on standard deviations of alignment and unevenness calculated for either • Entire length of each section • 10 m sliding interval • Test zones should be • 50% better than QN1,40% between QN1 and QN2, 10% between QN2 and QN3 • QN1, QN2, QN3 limits vary with test speed • Exclude section where isolated peaks cross QN3 • Twist & gauge should match railway's limits
Geometry of Rail-wheel contact • If unstable dynamic behaviour of test vehicle on straight/large radius curve • Calculate effective conicity based on • Actual rail profile • Actual wheel profile • Amplitude of lateral wheel movement =3mm • Compare with maximum permitted value, which is inversely related to speed
Test Vehicle Condition • For air suspension, also test on deflated condition • Test under unloaded and normal service load • Extraordinary loading also for sub-urban stock • Naturally worn wheel profile • New wheel profile if effective conicity change in service less than 50% or .05 • Effective conicity based on • 1435 mm track gauge, 3mm amplitude of lateral wheel movement
Test Vehicle Condition (contd.) • For hauled test vehicle, it should be rearmost with loose coupling • For loco, test under hauling condition • Test in both directions • Or instrument the bogie which is in unfavorable position • Dry rail condition • Record atmospheric condition and time
Data Analysis • For each section, calculate following parameters, • abs(0.15th ) & 99.85th percentile of all dynamic parameters. • Both values to be treated as readings of same parameter • Median for quasi-static parameters on curves • Weighted rms of vehicle accelerations for ride quality assessment • Moving rms value over 100m after every 10m
Data Analysis (contd.) • Sampling frequency >=200 Hz • For each parameter, group values of all sections to calculate • Mean, Xmean • Standard deviation, sd • Estimate maximum value, Xmax of each parameter
Data Analysis (contd.) • Xmax= Xmean+k*sd , k varies from 0 to 3 depending on confidence level and parameter type • Use two dimensional regression to estimate effect of speed/cant for quasi-static parameters • Modify estimation process for any parameter which is known to have other than normal distribution
Efficient Estimate? • Number of sections, N = 30, • No of data samples/section, B= 1286 • At 140 km/h, DAQ sampling rate 200 samples/sec • u is sample mean, s = sample standard deviation • Under UIC system, if no of data points n = 30 • Estimate of Xmean= u ±2.04 sdest/√n (student's t-distribution) • Estimate of sd, sdest = s – s*√(n-1)/Chi0.975 (= 0.8822*s) = s + s*√(n-1)/Chi0.025 ( = 1.3366*s) • Estimated Error in Xmax = 3*2.04*.3366*sd/√30 = 0.3761*s
Efficient Estimate? (contd) • If all data points are considered, • Taken either as single/multiple samples • Since N*B = 38580 >>100, • Estimate of Xmean= u ±1.96 sdest/√(N*B) = u ±.01*sdest (student's t-distribution same as normal distribution for large sample size ) • Estimate of sd, sdest = s ±s/√(2N*B) = s ±.0036s • Estimated Error in Xmax = 3*.01*.0036*s = 0.00011*s • If sd = .15g, UIC has .056g error margin against 0.00002g of above method
Acceptance limits • Lateral force2m = A*(10+axle load/3), A depends on vehicle and track structure • Hy/Q =0.8 for radius of curve ≥ 250m • Vertical and lateral body accelerations • Peaks 2.5 to 5 m/s2 , depending on vehicle type • 0.5 to 2m/s2 rms values, depending on vehicle type • 1.3 to 1.5 m/s2 quasi-static lateral acceleration
Acceptance limits (contd.) • Track fatigue limit (in kN) • Vertical force, minimum of • 90 +static axle load , for axle load up to 225 kN • 160 to 200 kN, depending on limiting speed • 145 kN for quasi-static force • Quasi static lateral force 145 kN on curves • 20Hz cut off frequency of filter
Desired Statistical Testing • Get % of track in QN1,QN2,QN3 of Indian Railways • Get dominant wave-length for each type of track • Get corresponding resonance speeds for the bogie under consideration • Check vehicle behaviour on resonant inputs in VCF lab • Check if recorded values are within limits
Desired Statistical Testing (contd) • Conduct oscillation trials on service track • Ensure proportion of QN1,QN2,QN3 is same as Indian Railway track • Cover 30*10(max. Wavelength) • Resonant speeds of all dominant wavelengths • Max speed • Run at max speed on track having at-least 10 peaks in D category
Thank You!!!
