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Copyright QinetiQ Pty Ltd 20141

Rail Bogie Structural AssuranceRoss StewartP. Hayes, S. Trezise, M.I Houston , A. Jackson, T. CooperA presentation to: Fatigue 2014 Conference

March 2014

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Contents

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1. Introduction2. Loads and Spectrum

Measurement

3. Finite Element Model4. Condition Assessment5. Structural Life Assessment6. Technical Assurance

Instructions

7. Conclusion


1. Introduction

Two types of classical cast steel rail bogies have been affected by cracking and defects, resulting in the bogies being removed from service over structural integrity concerns. The task was undertaken in two stages: Stage 1: Rapid relief engineering assessment that allowed some bogies to be returned

to operations for a limited 6 month period subject to amended operational and maintenance requirements.

Stage 2: More detailed engineering assessment to allow both bogies to be used for an extended period. The tasks undertaken for Stage 2 were: Loads and spectrum measurement FEM

Condition assessment Structural life assessment Technical assurance instructions

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1. Introduction

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Side View of Bogie Assembly


1. Introduction

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Single steel casting40-60 years30-40 yearsNo certification basisNo in-service structural failuresMany repairs


2. Loads and Spectrum MeasurementBogie instrumentation: Instrumented 2 bogies 2 x 16 channel loggers 22 strain gauges Wheel sensor speed / distance

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2. Loads and Spectrum Measurement

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Vertical Load Calibration

The strain gauges were calibrated by a shunt calibration and axial, lateral and longitudinal load calibrations.


2. Loads and Spectrum Measurement

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Operational data of over 20000 km was recorded for one bogie type and over 11000 km was recorded for the other bogie. This data was health checked, processed and rain flow counted to provide spectra for different locations on each bogie. Stress spectra were derived from the usage strain data.

Longitudinal Load Calibration Lateral Load Calibration


3. Finite Element Model

Bogie frame geometries were first modelled in AutoDesk Inventor Computer Aided Design (CAD) software, version 2011.

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The bogie CAD geometry was imported into Patran as a Parasolid file, which defined the frame component as a solid geometry entity for meshing and analysis.The axles and horn keeps (attached to the bottom of each pair of horns) were connected to appropriate points on the bogie frame in specific degrees of freedom using rigid link elements (RBE2 elements).Longitudinal loads from the axles due to braking were transmitted to the appropriate faces of the horns by the RBE2 elements acting in the X direction only.

Boundary Conditions of the FEM



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Linear static analysis using MSC.Nastran FEA solver and MSC.Patran pre- and post-processer.

Typical Mesh Detail FEA Output



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Load cases from AS 7519.3: 2008, BS-EN-13749:2011, one additional usage derived load case.


3. Finite Element ModelDeflected Shape and Contour Plot for Load

Case 1

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4. Condition Assessment

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Condition data was obtained from inspection reports and grouped by defect size, location, type and orientation.

Bogies striped and grit blastedBogie split in sections


4. Condition Assessment

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All bogies inspected had from 10 to 230+ defectsMajority of defects were Crack Like Indications (CLIs) Over 21 CLIs > 200 mm, the largest 725 mm

Most 10-25 mm 27 CLIs were found associated with welds Only one through crackMany CLI from manufactureMost CLI not fatigue all impact residual strength all potential fatigue cracks


5. Structural Life Assessment

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A list of assessment locations was developed and prioritised based upon a number of criteria consequence of failure number of defects in the general area stress magnitude the operational load survey



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Residual Strength Diagrams (RSD) critical crack length

Different flaw shapes to match condition data 56 and 49 separate locations Combination of locations and orientations

13 Load cases to consider Combinations of FEM and Analytical

Typical RSD



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Damage Tolerance Assessments (DTA) of a sub set of critical locations were undertakenLocations expected to produce the shortest crack lives- based on: critical crack lengths max operational stress spectrum local geometry

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Some locations produced unrealistic Crack Growth Lives (CGL) compared to their known service life. No fatigue test to peg CGL CGL pegged to service life Swing link lug used - worst CGL Loading known

A scaling factor was developed from this location and applied to the CGL at all locations.



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Raw CG Curve Scaled CG Curve

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a/c=3

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Maximum Acceptable Crack Length



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Acceptable flaws sizes where then calculated from the scaled crack growth curves, by allowing for the interval multiplied by a suitable safety factor.Crack growth curves for different a/c ratios to allow for alternate acceptance criteria developed.

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Acceptable crack length 38 mm

Interval * SF


5. Technical Assurance Instructions

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Technical assurance instructions covered the return to service for the customer agreed period.

This was based on initial inspection to examine the entire bogie frame using Magnetic Particle Inspection (MPI) and compare flaws at critical locations with the flaw acceptance criteria.

Any CLI at a critical location above the maximum acceptable size resulted in the bogie being classified unfit for service.


5. Technical Assurance Instructions

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Additional criteria were provided to account for flaw interaction assess weld repairs found Allow larger flaw sizes but with repeat inspections every 6 months

No growth allowed No through cracks 24 months/ 400,000 km limit

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