HYPERLOS® wheels for shoe-braking applications

It’s well known that Fracture Mechanics is an innovative science developed on the field of materials initially in Universities and Research Center, with the aim to understand mechanisms of failures and avoid “brittle fractures”. According to the history of the solid wheel described in the Chapter 6.6.2, the transfer of Fracture Mechanics in railway sector has been required by railway end users in the last ’80s, in order to avoid brittle fractures in service of rim chilled solid wheels for freight cars and, in this case, Fracture Mechanics became a special “safety index” for railway end users. The LRS TECHNO 1 book, published by LRS in 2008, represented the first attempt to closely examine the state of the art of Fracture Mechanics applied to railway “shoe braked” rim chilled solid wheels in the period 1986 - 2006. In recent years we have seen the wheels of Lucchini RS, as described in previous issues of the LRS_TECHNO book series, “rolling” through several environments, equipping trains of all kinds, but the old “shoe-braking system” remains a stable and not dead technology. In fact, the technology of “shoe-braking” is still active not only for standard shoe-braking applications of freights, but also for special application on the High Speed service and on the “Snow block brake control” for train operating in winter climate. For this reason, LRS decided to propose again an updating of Fracture Mechanics applied to materials design for solid wheels from 2008 upwards (2020). The in-depth research and development work conducted by Lucchini RS with the continuous and precious cooperation of the University of Brescia in the last decade allows us to present an innovative steel grade, called HYPERLOS®, designed specifically for the heaviest shoe-braking application of the worldwide market, in the respect of the EN13262 standard. Exposure to elevated temperatures due to thermal overloading of shoe-braking has been carefully studied by Lucchini RS and University of Brescia, using Fracture Mechanics, experimental tests by “special small-scale testing devices” and numerical simulations by FEM analysis. HYPERLOS® characterization and comparison with other potential materials suited for shoe-braking application has been carried out coupled with all the new brake block materials (P10, K or LL type). The high sustainability of the HYPERLOS® solution is carried out by LRS thanks to the steel production integrated into the most innovative industrial processes and the most advanced and efficient technologies, in the respect of the Cradle to Cradle (C2C) philosophy. The collected results on the production of HYPERLOS®, monitored over a long period, according to the Fracture Mechanics approach, demonstrates the efforts towards the right direction in materials design: better Strength and better Fracture Toughness. In addition to its integrated steel-manufacturing process, the Lucchini RS Group operates a worldwide customer assistance network, and supports the Users in materials design and collecting feedback from the field. Optimization of the Total Life Cycle Cost of the wheel should induce Operators to select qualified suppliers able not only to guarantee the steel itself, but also to understand the potential damage mechanisms encountered in special applications, so that the best technical solution should be proposed and put into service. The latest volume of the LRS_TECHNO 13 series is a clear example of the application of this philosophy. The reader will discover in the LRS_TECHNO 13 book the complex technologies and evolved methods required to develop innovative wheel materials, as well as Lucchini RS Group’s passion, talent and creativity for advanced Customer-oriented solutions.