Residual Stress in Rails Effects on Rail Integrity and Railroad Economics Volume II: Theoretical and Numerical Analyses

Rail integrity is a current application of engineering fracture mechanics at a practical level. Although railroad rails have been manufactured and used for more than a century, it is only in the last ten years that the effects of their crack propagation and fracture characteristics have been considered from a rational viewpoint. The J,Jractical objectives are to develop damage tolerance ~delines for rail inspection and to improve the fracture resistance of new rail productiOn. Rail fatigue crack propagation rates and fracture resistance are strongly influenced by residual stresses, which are introduced into the rail both during proouction and in service. Therefore, the rail residual stress field must be well understood before fracture mechanics can be usefully applied to the subject of rail integrity. The three-dintensional character of rail and its stress fields make it essential to apply both experimental and analytical methods in order to twderstand the effects of pro­ duction and service variables on residual stress and the effects of the stress on fatigue crack propagation and fracture. This volume brings to~ether field observations and experimental stress analysis of railroad rails in the Umted States and Europe. The ongoing search for an efficient and accurate technique is emphasized. A companion volume brings together several analytical investigations, based on advanced compu­ tational mechanics methods, for correlation of the experimental data as well as eval­ uation of the effects of residual stress on rail integrity.

of Volume II.- 1. Residual stresses and web fracture in roller-straightened rail.- 1.1 Introduction.- 1.2 Determination of residual stresses.- 1.3 Effects of residual stresses on web fracture.- 1.4 A saw-cutting test to quantify severity of residual stresses.- 1.5 Stress transients and short cracks at rail ends.- 1.6 Creation of residual stresses: analyzing the roller-straightener.- 1.7 Conclusions.- Acknowledgements.- References.- 2. Some factors influencing the transition from shelling to detail fracture.- 2.1 Introduction.- 2.2 Crack path stability of statically growing shells.- 2.3 Dynamic crack curving.- 2.4 Calculation of shell growth rates.- 2.5 Conclusions.- Acknowledgement.- References.- 3. Analysis of crack front propagation in contact.- 3.1 Introduction.- 3.2 Existing theories and research objective.- 3.3 Two-dimensional model.- 3.4 Method of solution.- 3.5 Results.- 3.6 Conclusions.- 3.7 Appendix — matrix equations for contact solution.- References.- 4. Effect of load sequence on fatigue life of rail steel.- 4.1 Introduction.- 4.2 Strain energy density criterion.- 4.3 Material characterization.- 4.4 Load spectra.- 4.5 Finite element analysis.- 4.6 Discussion and conclusions.- References.- 5. On residual stresses in corrugated rails and wheel/rail interaction.- 5.1 Introduction.- 5.2 Simple models of wheel/rail interaction.- 5.3 Simulation of rolling contact process.- 5.4 Measurements of residual stresses in corrugated rail.- 5.5 Final remarks.- References.- 6. Prediction of actual residual stresses by constrained minimization of energy.- 6.1 Introduction.- 6.2 Mechanical models.- 6.3 Numerical models.- 6.4 Optimization strategy.- 6.5 Numerical results.- 6.6 Concluding remarks.- References.- 7. Hybrid finite element method for estimation of actual residualstresses.- 7.1 Introduction.- 7.2 Numerical approach.- 7.3 Performance tests.- 7.4 Example analysis of a rail.- 7.5 Discussion and conclusions.- References.- 8. Application of the constrained minimization method to the prediction of residual stresses in actual rail sections.- 8.1 Introduction.- 8.2 Background.- 8.3 Analysis method.- 8.4 Results.- 8.5 Discussion and conclusions.- References.- 9. Estimation of actual residual stresses by the boundary element method.- 9.1 Introduction.- 9.2 Estimation of residual stresses by the BEM.- 9.3 Results of numerical examples.- 9.4 Conclusions.- References.- 10. A new feasible directions method in nonlinear optimization.- 10.1 Introduction.- 10.2 New algorithm.- 10.3 Tests and comparisons.- 10.4 Concluding remarks.- References.- 11. Enhancement of experimental results by constrained minimization.- 11.1 Introduction.- 11.2 General formulation of the problem.- 11.3 Tests of enhancement concept.- 11.4 Conclusion.- References.- 12. On future development of the constrained energy minimization method.- 12.1 Introduction.- 12.2 Continuation of current work.- 12.3 New topics.- References.