The effect of strain hardening on shakedown limits of a pearlitic rail steel

The load limit below which a material remains elastic for the first application of load is known as the elastic limit. However, material in a railway rail is loaded not once but many times and the load limit below which the material remains elastic in the steady state is known as the elastic shakedown limit, This limit is higher than the elastic limit, and is the basis of tribological design. Such limits are known for solids which have hardness unvarying with depth. However, techniques of heat treatment or coating lead to a variation in hardness with depth for which the effect on the shakedown limit has only recently been established. In the present work the influence of strain hardening on the shakedown limit of a pearlitic rail steel has been analysed. The data used were taken from an experimental study by Tyfour et al. (1) in which wheel-rail contact was simulated by rolling-sliding line contact. The results indicate that the load bearing capacity increases to about four times that without strain hardening in line contact, and even more in point contact.