VTAC calculator: Guidance note for determining T values

Transcription

1 VTAC calculator: Guidance note for determining T values The surface damage component of the VTAC calculator allows users to either select the vehicle characteristics (primary yaw stiffness and vehicle weight) from a pre-determined list or to enter values of T which have been derived for that particular vehicle. Recently, some users have raised questions regarding the methodology, so this guidance note presents an update to the original instruction sheet which accompanied the VTAC calculator spreadsheet. T definition The contact patch frictional energy, T (or T-gamma), is calculated from lateral and longitudinal creep forces, T x and T y, and creepages, x and y, using the formula: TT x x T y y and can usually be output direct from most vehicle dynamics software modelling packages. Parameters for calculating T-gamma Calculation of T generally requires use of a multi-body vehicle dynamics simulator that is capable of calculating creepage and creep forces at the wheel rail interface. A series of standardised parameters for these simulations is presented in UK R Report o "Methodology to Calculate Variable Usage Charges for Control Period 4" published in March Since the publication of that report an updated version of the Vampire vehicle dynamics software has been issued which changes the way that T is calculated: the calculation now includes the effect of spin creep in the calculation, which can have some effect on the calculated magnitude of T compared with earlier methodologies. Since Vampire was used to calculate the reference values of T used as input to the VTAC calculator, and has been used by many users to determine inputs to the VTAC calculator, this guidance note has been updated to reflect these changes and the recommended methodology for determining T. Simulation condition parameters It is recommended that Vampire 5.0 be used for the simulations. Later versions of Vampire (or other simulation packages) include the contribution of spin creep in the T calculation, which can give higher predicted values of T which are out of line with the reference values in the calculator If later versions of Vampire than 5.0 are used then it is recommended that the form of the *output section of the.run file given in the Tgamma calculation guidance note- issue 1.doc Page 1/7

2 sample run file in Appendix 2 should be used: this will determine T without the contribution of spin creep. If simulation packages other than Vampire are used then it is suggested that contact with a member of V/T SIC PPG is made to discuss any differences between the results from the two simulation packages: contact details for PPG are supplied at the end of this document. Calculations are to be made on right-hand curves Track irregularity files are not used: the analysis should be for the vehicle under steady-state conditions. The track file should consist of an entry transition followed by a section of constant radius and constant cant of at least 350 m length. The T values should be determined as the average of the vehicle running over at least 250m of track on the constant radius curve. The start of the track section over which the average is taken should be at least 100m after the end of the entry transition into the curve to allow any transient effects to be sufficiently damped. Cant deficiency o For all passenger vehicles (except tilting trains) simulations should be run at a cant deficiency of 40 mm o For freight vehicles not limited to 45 mph simulations should be run at balance speed o For freight vehicles limited to 45 mph simulations should be run at 20 mm cant excess Coefficient of friction o All contact points on the left (high) rail except the gauge face use a coefficient of friction of 0.4 o For the gauge face of the left (high) rail use a coefficient of friction of 0.2 o All contact points on the right (low) rail use a coefficient of friction of 0.45 Curve radii Calculations should be carried out for the vehicle running over each of the 15 curve radii shown in Table 1. Table 1: Curve radii to include in simulations Curve radii (m) ,000 Wheel and rail profiles For the analysis of passenger vehicles with P8 wheels a standard Vampire contact file ( F_mod_L_on_0-750-H_type2.con ) is available, and is recommended for T studies. A listing of the.con file is given in Appendix 1. Tgamma calculation guidance note- issue 1.doc Page 2/7

3 All wheel/rail contact data should be generated assuming a track gauge of 1435mm and a wheelset back-to-back spacing of 1360mm. It is important that the flange contact L and R markers in the contact data files are not edited or moved within the contact file. For the analysis of freight vehicles measured part-worn wheel and rail profiles should be used in the calculations. The wheel profiles which should be used are shown in Table 2. Separate rail profiles are used for left and right rails as follows: Left (high) rail: H.ban Right (low) rail: L.ban Table 2: Wheel profile names Profile type Left (high rail) wheel profile Right (low rail) wheel profile Worn P5 P5_ whl P5_ whl Worn P10 P10_ whl P10_ whl Outputs The output should be the average value of T, determined as described in the previous sections, from the high rail for each wheelset of a bogie for the vehicle running on each curve. If there are different results from the leading and trailing bogies, the values should be chosen from the bogie which gives the highest T values. If there are two points of contact on the high rail (tread and flange) choose the one with the highest T. Vampire input files All the required input files are available from etwork Rail PPG. These include sample track geometry files,.run files containing the appropriate speed and coefficients of friction and output channels, and wheel/rail contact data files. Listings of a typical Vampire.run file is given in Appendix 2, and Appendix 3 details curvature, cant and speed combinations which have been used to obtain the appropriate cant deficiencies on each curve. PPG contact For copies of the track or run files previously used in these analyses, or queries regarding the procedure for T calculation please contact: Mark Burstow Principal Vehicle Track Dynamics Engineer etwork Rail 40 Melton Street London, W1 2EE or mark.burstow@networkrail.co.uk Tgamma calculation guidance note- issue 1.doc Page 3/7

4 Appendix 1 Listing of Vampire contact file, F_mod_L_on_0-750-H_type2.con, for use with passenger vehicles with P8 wheels VAMPIRE Version (July 2006) COTACT DATA GEERATIO PROGRAM VAMPIRE WHEEL/RAIL COTACT DATA *WHEEL F_mod_L.whl and F_mod_R.whl FLAGEBACK mm DIAMETER mm YAW AGLE 0.00 mrad *RAIL H.ban and L.ban TRACK GAUGE mm *AXLELOAD K *LATERAL OFFSET YREL DRL DRR DELTL DELTR COYL COYR COXL COXR COZL COZR AREAL AREAR AOBL AOBR RHOL RHOR ROLL L Tgamma calculation guidance note- issue 1.doc Page 4/7

5 R Tgamma calculation guidance note- issue 1.doc Page 5/7

6 Appendix 2 Listing of Vampire run file for use with T simulations This listing does not use the T output channel available in Vampire, but calculates T from the creep forces and creepages directly. This is to ensure that the influence of spin creep is not included in the evaluation of T. %insert run title here% UITS VAMPIRE %insert vehicle file name here% *TRASIET SPEED %speed% TRACKDESIG %curve% *CREEP O-LIEAR PROFILE %contact% *OUTPUT Longitudinal creep force- wset1- L CL01X Longitudinal creep force- wset1- R CR01X Longitudinal creep force- wset1- F CF01X Longitudinal creep force- wset2- L CL02X Longitudinal creep force- wset2- R CR02X Longitudinal creep force- wset2- F CF02X Lateral creep force- wset1- L CL01Y Lateral creep force- wset1- R CR01Y Lateral creep force- wset1- F CF01Y Lateral creep force- wset2- L CL02Y Lateral creep force- wset2- R CR02Y Lateral creep force- wset2- F CF02Y Wear number (no spin)- wset 1- L 1000*(ABS(CL01X*VL01X)+ABS(CL01Y*VL01Y)) Wear number (no spin)- wset 1- F 1000*(ABS(CF01X*VF01X)+ABS(CF01Y*VF01Y)) Wear number (no spin)- wset 2- L 1000*(ABS(CL02X*VL02X)+ABS(CL02Y*VL02Y)) Wear number (no spin)- wset 2- F 1000*(ABS(CF02X*VF02X)+ABS(CF02Y*VF02Y)) velocity m/s SP * Tgamma calculation guidance note- issue 1.doc Page 6/7

7 Appendix 3 Details of track files and vehicle speeds to attain the required cant deficiencies Curve Installed Vehicle speed (m/s) radius (m) cant (mm) 40mm cant deficiency Cant equilibrium 20mm cant excess n/a n/a 10, n/a Tgamma calculation guidance note- issue 1.doc Page 7/7