Residual stress in laser cladded rail

To improve the fatigue life of components subject to loads with high surface strain gradients, it is possible to coat them with an alloy of higher durability. The present study focuses on the effect of cladding high value track components, made of a standard rail steel UIC 900A/grade 260, with a layer of a premium martensitic stainless steel to reduce wear and fatigue. The laser cladding process inevitably generates residual stresses in the clad and parent metal, which could be detrimental to the integrity of the component. Therefore, measurements to determine the residual stress state of cladded rail were performed using semi-destructive centre-hole and deep hole drilling and non-destructive neutron diffraction techniques. Subsequently, the effects of cycling loading and wear, representative of typical service loads, on the redistribution of the residual stress field were investigated. It was observed that laser cladding causes a triaxial compressive residual stress field in the clad and near the interface and a tensile stress field in the parent material. The stress field is shown to change when the first cycle of load is applied but reaches a steady state after only 10 cycles: After the 10th cycle there is no evidence that the clad continues accumulating strain which could indicate that there is low risk of ratcheting. Wear effect on residual stress redistribution was found to be local on the surface of the specimen only

Corporate & Investment Banking

La crisi economica e finanziaria esplosa con il fallimento di Lehman Brothers ha messo in discussione il modello operativo e le scelte strategiche messe in atto dalle Investment Banks e, di fatto, la loro funzione-utilità all’interno di un sistema finanziario. La rincorsa scellerata al profitto di breve termine, l’assunzione di livelli elevatissimi di rischio favoriti da un indebolimento della normativa e dei controlli interni hanno portato le banche di investimento sull’”orlo dell’estinzione”. Le scelte spesso eticamente discutibili se non addirittura illegali ne hanno minato la reputazione e causato l’applicazione di pesanti sanzioni da parte delle autorità di vigilanza. Eppure, per un sistema economico, rimane fondamentale poter disporre di una catena finanziaria evoluta nell’ambito della quale i servizi di Corporate & Investment Banking sono fondamentali per l’elevato valore aggiunto che sono in grado di esprimere. L’accesso a queste particolari tipologie di operazioni, spesso, rappresenta per l’impresa un’occasione per intraprendere un percorso virtuoso di miglioramento della propria cultura finanziaria. Il testo descrive le tecniche, le logiche e i vincoli che regolano la costruzione delle operazioni tipiche di questa specifica area dell’intermediazione. In particolare, la trattazione si sofferma ad analizzare la struttura di operazioni normalmente sviluppate secondo una logica “tailor made”. All’intermediario è infatti richiesto di supportare l’impresa seguendo una logica di forte personalizzazione per riuscire a soddisfarne le esigenze finanziarie di maggiore complessità. Il volume fornisce un supporto logico e teorico per approcciare le technicalities utilizzate dagli operatori nell’attività di corporate banking (valutazione d’azienda, analisi del merito creditizio, analisi degli investimenti, diagnosi dei fabbisogni finanziari e copertura dei rischi). Al contempo, offre l’opportunità di approfondire, con taglio applicativo, l’analisi delle diverse operazioni di Corporate & Investment banking che rappresentano l’insieme delle attività di chi opera nel settore (venture capital e private equity, quotazione d’azienda ed emissioni di prestiti obbligazioni, mezzanine finance, operazioni di M&A e LBO, ristrutturazione d’impresa, copertura dei rischi)

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

Interpretation of RCF and wear tests on wheel-rail steels

Oral presentation - ESIS-TC24 workshop on “Application of Fracture Mechanics to Railway Components-2