1 2012-01-10

Användning av andraderivator av Spårlägesparameterar

för Värdering av Spårlägeskvaliten

Martin Li

Trafikverket,

Underhåll / Ban o vägssystem / Spårsystem

78189, Borlänge, Sweden

Transportforum 2012, 11-12 januari I Linköping

2 2012-01-10

On the Use of Second-Order Derivatives of Track

Irregularity for Assessing Track Geometry Quality

Martin Li1 , Ingemar Persson2 , Jan Spännar1 and Mats Berg3

1. Swedish Transport Administration (Trafikverket), Borlänge, Sweden

2. AB DEsolver, Optand, Sweden

3. KTH, Rail Vehicles, Stockholm, Sweden

22nd IAVSD Symposium

14-19 August 2011

Manchester, UK

The paper has been reviewed and accepted for publication on the journal Vehivle

system Dynamics (VSD)

3 2012-01-10

Background

• Measuring and assessing track geometry quality play an important role for safety control and track maintenance.

• By using a modern track recording car (TRC), track geometry data including longitudinal level, alignment, gauge, cross level and twist, are routinely collected and assessed.

• Current standards and assessment methods are based on the track geometry data alone, by comparing isolated defects with predefined limit values and by computing their standard deviations

• But it is the dynamic responses of vehicle and track that are relevant to safety, maintenance costs and ride comfort.

4 2012-01-10

Track recording car (TRC) in Sweden

STRIX Infranord SWE owns 1 pcs.

principal Track record. veh. at TRV.

New Track record. veh. is planned for 2010

(IMV 200 Infranord) delayed until 2011/12?

5 2012-01-10

TRV Limit Values (BVF 587.02)

6 2012-01-10

On-track test results: low correlation between Q-force and LL

[5] T. Karis, Track Irregularities for High-Speed Trains, Master Thesis, KTH, 2009

7 2012-01-10

Alert! > 9 mm

No forces….

Short waved irregularity

High forces !!

Not easy to detect

8 2012-01-10

Motivations of using the derivatives of longitudinal level (LL2)

• Only using amplitudes of isolated defects and standard deviations is

neither sufficient for vehicle dynamics nor efficient for track maintenance

• Without taking into account wavelength and defect shape, the correlation

between amplitudes of isolated defects and wheel-rail force is low

• Enhanced assessment can be made by Vehicle Response Analysis

(VRA), e.g., Pupil by ProRail and VRA-method by DB. However, we

observe:

– VRA method tends to be very expensive and complex to use

– Difficult to consider all vehicle types and all speed ranges

– Most importantly, although the VRA-results are good, eventually, it is the track

sections and defects that need to be inspected and identified so that

appropriate correction maintenance can be taken.

• Question: are the derivatives of track defects (LL2) useful?

9 2012-01-10

Theoretical study: SDOF model

The dynamic equation can be written as

Note: it is LL2 not LL that contributes directly to the dynamic force due to unsprung mass.

The wheel-rail contact force can be calculated as

Transfer function from LL to z

10 2012-01-10

Gensys simulation results

LL

LL2

Q_dyn

• A modified regional passenger train

• Vehicle model has been developed and verified by the Green train project at KTH [12]

• Speed: V= 220 km/h

11 2012-01-10

Gensys simulation results:

• The correlation coefficient for Q_dyn – LL is only 0.17

• The correlation coefficient for Q_dyn – LL2 is increased to 0.63

12 2012-01-10

Simulation results for three theoretical track defects

(A) Single cosine, 10 m

wavelength, ballast

settlement

(B) Sinusoidal and triangle,

standard defect in

S&Cs ([8])

(C) Harmonic function, 3 m

wavelength, initial rail

defect

• Same amplitude: 4 mm

• Different wavelength

and shape

• Different second-order

derivatives

• Different dynamic track

forces

13 2012-01-10

Summary

• Current methods of assessing track geometry quality based on amplitudes

of isolated defects and standard deviations are neither effective for planning

track maintenance nor sufficient for evaluating vehicle dynamics

• Theoretical study, simulation results and PSD analysis in this study

demonstrate that the second-order derivatives of longitudinal level (LL2)

can be used to enhance the assessment of vertical track geometry quality.

• Advantages of using LL2:

– wavelength and shape of track defects are considered

– easy to use.

• LL2 cannot and shall not replace the Vehicle Response Analysis (VRA)

– When VRA is available, LL2 is useful to further characterise the track defect type

– When VRA is not available, LL2 provides an effective analysis of track defects

that potentially may result in severe vehicle responses

14 2012-01-10

‘Good’: normal track

Both amplitude and 2nd derivatives are big!

Thank you for your attention!

’Bad’ : track shifted after a test run