• Fracture Mechanics• Adhesion Theories• NDT methods for track and wheel sets• Rolling contact defects• Rail Inspection methodsStage 2: Static Analysis • Wheel and profiles: • Creating 3D models of the wheel and track using geometricaldimensions from published data.
• Short track and a section of the wheel “reducesimulation time”• FEA – Using Ansys software• Determine area formed by contact bodies (contactpatch)• Determine stresses: (Normal, compressive)• Analytical approach – Hertz Method• Validation of FEAresults using published data and analytical method• Fatigue analysisusing FEA and Fracture mechanics assuming a defect has been detected by NDTmethodsStage 3: Dynamic Analysis• Create a 3D model of the track and wheel • 100m long straight track and a complete wheel • Consider effects of changing:• Applying different wheel velocities• Track curvatureStage 4: Discussions and Conclusions• Discussion of Static and dynamic models• Fatigue life analysis and maintenance recommendations• Recommendations for future work • ConclusionsEvaluation and TestingMethodsThe procedurefor evaluating FEA will be undertaken using grid dependency testing techniques.This involves producing an initial set of results with a course mesh thenproceeding to refine the mesh until there is little or no change betweenstresses achieved from one iteration to another. While refining the mesh at thebeginning of each study, a mesh quality metrics will be evaluated beforeproceeding with the FEA simulation. Validation of the FEA model will be doneusing published data and also compared with Hertz analytical methods forcontact stress and fracture mechanics for fatigue cycles to failure.Economic, legal, social,ethical and environmental considerationsEconomic The railindustry is a very lucrative sector not only because of the numbers of peoplethat use the trains for transport but also long haulage and mass movement ofheavy loads. To keep the wheels of the economy moving on the rail it is vitallyimportant that the infrastructure is available almost all the time and that servicework between peak times is kept at a minimum as much as possible to avoid anydisruptions to the network. The types of tracks, wheels and locomotives used ona given section of line should be chosen with a clear understanding of thegeography in that area.
This helps to prolong track life and reduce financialpenalties incurred due to regular maintenance. Furthermore, regular maintenancecalls for more operatives and this can impact on company profits etc. Legal To preventendangering people’s lives and damage to reputation of organisations controlstandards have been put in place to make sure that suppliers of rail equipmentsuch as tracks and wheel all conform to the guiding procedures. The proceduresgives limits on material requirements, profile designs and tolerances, loadlimits, wear limits and maintenance requirements just to name a few.Wheel profile designsIn the United Kingdom, wheelprofile design shall be done in line with Railway Group Standard GM/RT2466Section 2.
3 of Part 2 which states that:New wheelsetdesigns shall use monobloc design wheels. The width of the wheel rim (thedistance between the flange back and the outside face of the rim) shall bewithin the range 127 to 150 mm and the Tread profile limits are shown in AppendixK. For monobloc wheels only, it is permissible to reduce the rim thickness atthe final re-profiling such that the fatigue life of the wheel rim becomesfinite. The predicted fatigue life of the wheel after the final re-profilingshall be not less than three times the remaining service life.
New wheeldesigns shall make provision for balancing without the need for holes in thewheel. Maintenance requirements for wheels should be in keeping with Part 4which states when what action is required when wheel flats reach a certainlength as shown in Appendix J. (Railway Group Standard, 2009)Track profile designsGuidance for design track systems is highlighted in the RailwayGroup Standard GC/RT5021 which covers many aspects of track design whichinclude but not limited to:Track geometryrequirements – which in itselfincludes things like circular curves, transition curves, track gauge, normallimit design values, general horizontal alignments requirements, railinclinations etc. Track systems and component requirements – gives guidance on performance specification fortrack systems, requirements for rails, rail, gaps and fastening requirements.
AppendixA of GC/RT5021 gives guidance for the geometrical requirements for a 60E2 railprofile recommended for high speed infrastructure and it is also shown in thisreport in Appendix M. Requirements for other rail profile systems includingthat of UIC60 which is being investigated in this project are shown in AppendixG.Social and ethical Working withrail infrastructure such as tracks and train accessories such as train wheelseither from a design, maintenance or management stand point in my opinioncarries the same responsibility as a doctor would to their patients. Theconditions under which the rail and the track operate are very arduous to saythe least and this naturally places them in in the same bracket as other riskadverse structures such as bridges, aeroplanes cars e.tc. People’s lives are atstake and the safety of passengers who commute by rail on daily basis dependson the competency and professionalism of the people who are committed toapplying best practice in designing and maintenance of our rail network.
It istherefore, important to understand the implications of designing track andwheel profiles in a certain way, not only on the aspect of safety but also interactionphenomenon between the track and wheel for passenger comfort and reducingpremature wear of these structures.Environmental There is amassive drive nowadays by governments of leading nations to reduce pollutioneither at manufacturing and consumption level. Environmental agencies have beenset-up to take a leadership role in setting the standards to which manycompanies are subscribed including rail operators and those that look after therail network such as Network Rail in the UK. That said, it is imperative from adesign stand point to have a clear understanding of track defects which areinfluenced by the types of wheels used on given track locations so that bestconditions are created for sustained usage and reduced wear rates.
Track lifecan be extended by applying good design practice, this translates to reducedreplacements which intern reduces consumption of row materials atmanufacturing. Furthermore, extended maintenance operations can cause airpollution through moving earth and transport of raw materials on site.Stage 2 AttainmentsStatic Analysis Thestatic analysis model was created using the profile of a UIC60 rail and a monoblock wheel published in the article by (J. P. Srivastava, 2014) . The results from this paper were used to validate our FEAmodel. 3DCAD models of wheel and the rail which were created using an external 3D CADpackaged then imported into Ansys for FEA analysis.
The dimensions of the wheeland rail are shown in Figure 13. To enable a like for like comparison with theresults obtained in the publication the rail and the wheel were assumed tolinear elastic. The material properties used in the static analysis wereassumed to be as follows:- Elastic Modulus, E = 210GPa for both the wheel andthe rail and the Passions ratio was and Density 7850kg/m3.
Thecoefficient of friction between the rail and the wheel were considered to be0.3.FEAsimulation set-up assumes a fixed support at the base of the rail to preventrigid body motion. To reduce the complexity of the FEA model only a section ofthe wheel was modelled. A compressive load of 10 tonnes (98100N) was applied onthe bearing surface of the wheel where the axle is mounted.
A mesh dependencystudy was conducted starting a default course mesh then refining it until itwas observed that the results obtained one iteration to another remained unchangedor virtually the same. Analyticalmethods have been employed using Hertz theory the details of which will becovered in the body of the main report. However, for the purposes ofsubmission, Appendix N showsa screen shot of the excel file used to compute the analytical Max contact stresslisted in Table 1.
ResultsTheresults for each iteration leading to the final converged set, mesh convergenceplot, contact analysis are shown in Appendix H. Convergence was reached whenthere was 1.42% change between simulation number 7 and 8. The highest stressescan be seen on the rail head towards the gauge corner where the contactanalysis plot indicates sliding behaviour between the rail and the wheel. TheVon-Mises stress at this point is 480.6MPa. This is considered to be thecritical location for fatigue crack initiation.
The Contact Pressure is1031.8MPa, again this is shown in Appendix H. A like for like comparison hasbeen done between FEA results and published in form of contour plots to see thedistribution of stresses around the contact point.
Max values are shown inTable 1 to further validate the FEA model. Table 1.Table of results to validate FEA model. Static Analysis Contact Stress (MPa) Von-Mises Stress (MPa) FEA Published data Analytical FEA Published data Analytical 1031.8 1226.8 1205.387 480.6 350.
59 In progress Project Management Project planningand execution shall be done as shown in Appendix I starting with identificationof project and drafting a proposal leading up to submissions which already beenaccomplished in Milestone 1. Milestone 2 which where I am herded will culminatein the submission of a Preliminary Report which is due on the 15thof Jan 2018. Extracts of what been achieved so far has been highlighted in the background,literature review and Stage 2 attainments. Time scales leading up to theInterim Presentation, Viva Voice and Final submission including sub-steps inbetween have also been presented in the Gantt chart.
Conclusion Notable headwayhas been made in directing this project on a path that pursues in the bestpossible way the list of objectives which have been commitment to at theproposal stage. Comprehensive literature on different accidents which haveoccurred in the past have been reviewed from which the ones discussed in thissubmission have emerged. It quite intriguing to learn how crucial the contactpoint between the rail and the track from both a safety and design point ofview and also what can happen when things go wrong.
Common track defects havebeen highlighted and will be embellished on later as the report progresses.What has been observed thus far is that fatigue accounts for some of the mostdisastrous accidents which have occurs on the railway all over the world andcontinues to be a major issue even in recent years. FEA analysis of UIC60 railand mono block wheel with a tread diameter of 1000mm has been undertaken understatic loading conditions.
The results obtained have been validated usingpublished data and analytical methods to show a good correlation between allthree. Although the FEA model predicts the lowest contact pressure thedifference to the published results is 16% and 14.4% lower than the analyticalresults. Factors which influence these observations shall be look into at alater stage with a fine tooth comb. The bulk of work intended to reachMilestone 2 as shown in Appendix I has been met to a level that warrants submission.
It is on this strength that I believe the project to be on track and I can nowtake aim at Milestone 3.