Angelo Mazzù

• PhD
• Professor (Associate) at University of Brescia

This study aimed to investigate the impact of thermal loading resulting from shoe braking on ER8, SUPERLOS Ò and ER-TEN railway wheels. To assess the effects of exposure to temperatures ranging from 700 to 970°C, a series of tests, including hardness, tensile, toughness, fatigue crack growth rate tests and microstructural analysis, were conducted....

Twin-roll casting is a technology for the production of thin strips directly from liquid metal by combining continuous casting with hot rolling in a single step. The thermo-mechanical cyclic interaction with the solidifying strip causes fatigue crack formation at the outer surface of the rolls. A 2D FEM model with Eulerian boundary conditions and t...

Railway systems play a pivotal role in modern transportation networks, contributing to both efficiency and environmental sustainability. This study investigated the multifaceted aspects of wear phenomena in railway engineering, focusing on their significant implications for environmental costs and operational efficiency. Experimental trials were co...

The diffusion of brake-shoe system has made it necessary to study brake–wheel–rail interactions. This study aims to elucidate this topic with an innovative small-scale test rig, the ‘4-contact machine’. A test procedure is designed in which an ER7 steel wheel is coupled with a R260 steel rail and two different brake-shoe materials (cast iron and si...

Small-scale experimental tests were carried out by a bi-disc machine to reproduce the phenomena occurring in shoe-braked railway wheels. Wheel specimens of three different steels were subjected first to a braking step against cast iron brake-block specimens in full sliding condition, then to a running step against a rail steel in rolling-sliding co...

In windblown sand environments, sand transport rate (the mass of sand passing through a unit sectional area in a unit time, mg·cm⁻²·s⁻¹) varies in different underlying surfaces. This work aimed to explore the influence sand transport rate on rolling wear and damage behaviors of wheel and rail materials in Gobi and desert windblown sand environments...

A semianalytical model is introduced to assess rolling contact fatigue problems in railway applications. The constitutive law is based on the nonlinear kinematic and isotropic hardening model of Chaboche–Lemaitre, which allows the cyclic elastoplastic strain under the contact surface to be evaluated. The much higher computational effectiveness in c...

A Failure Assessment Diagram (FAD), developed for rolling contact, was specifically formulated for railway wheel steels. The FAD allows combining a multiaxial fatigue criterion with the linear elastic fracture mechanics concept; in particular, it was used to assess the fatigue failure in wet contact, related to the pressurization of the fluid entra...

The dynamical behaviour of the Bronze Age war chariots was studied, considering the different assembly solutions that were found in evidences and pictures. In particular, the chariots with the axle in rear position, typical of Near-East and Egypt, were compared with the European ones, which generally had the axle in central position under the chari...

The introduction of two-wheel chariots, pulled by horses, was a key technological innovation in the Bronze Age. Archaeological evidences, found in Northern Africa, Europe and Asia, allowed identifying various chariot typologies and understanding their main features. However, many questions about the function of single pieces and the behavior of the...

The effect of material plastic properties in solid-contaminated wheel-rail couplings was studied by simplified finite element models, considering typical couplings of steels following European and American standards. Analyses of non-contaminated contact were performed for comparison. It resulted that in clean contact there is a reciprocal influence...

A vision-based experimental methodology was developed for monitoring the surface state evolution of specimens during twin-disc rolling contact tests, aimed at providing information for identifying the damage phenomena. The system is based on a high-speed camera and three laser pointers for illuminating the specimen surface. Images of the specimen s...

Wheel microstructure significantly affects railway wheel performances. Although wheel microstructure traditionally consists of pearlite-ferrite, it is possible to detect some intermediate structures traces, for instance bainite, generated during the thermal treatment process. The difference in mechanical properties between pearlite and bainite caus...

The microstructural and hardness properties of welded joints of AA 6005-T6 aluminum alloy obtained with metal inert gas (MIG), fiber laser–MIG hybrid, and cold metal transfer (CMT) welding were analyzed immediately after welding and after 3 years of natural aging. The fine hardening precipitation within the heat-affected zone, fusion zone, and base...

A recent interest on emergency shoe braking in high speed trains stimulated the research on the damage due to sliding contact between brake blocks and wheel tread. Bi-disc tests, with rolling/sliding contact between specimens extracted from wheels and brake blocks, were previously performed in constant working conditions to reproduce the temperatur...

The effect of shoe braking on three railway wheel steels was studied by means of bi-disc tests, in order to evaluate the applicability of shoe braking as an emergency stop braking system in high-speed passenger trains. Disc-shaped specimens, extracted from real wheels, were initially paired with discs extracted from cast iron brake blocks, in condi...

This work aims to better understand the complex damage phenomena taking place at the wheel/brake block interface due to the thermomechanical load. An experimental procedure, articulated in three series of tests carried out with a bi-disc machine, was designed in order to experimentally simulate in controlled laboratory conditions the thermomechanic...

The purpose of this work is to gain a better understanding of the complex damage phenomena taking place at the railway wheel/brake block interface due to thermo-mechanical loading. Initially, full-stop braking was studied using Finite Element (FE) simulations to estimate the temperature reached in the wheel rim. Experiments to reproduce wheel damag...

An investigation was carried out to study the effects caused by shoe braking on the microstructure and mechanical properties of ER7, CLASS B, CLASS C, and SANDLOS® wheels as a result of the thermal load. Particular attention was given to cases of exposure to medium and high temperatures, namely from 700 °C to 970 °C, followed by air cooling. Hardne...

An analytical model for the assessment of a contact in the presence of a solid contaminant is presented, mainly aimed at studying the damage to railway wheels and rails operating in third-body-contaminated environments. The model, developed under 2D plane strain idealization, includes multiple evenly spaced rigid cylindrical contaminant bodies entr...

Wear and rolling contact fatigue are competing phenomena in railway wheels, as wear tends to shorten or remove surface cracks nucleated by ratcheting. The presence of water at the contact interface can enhance crack propagation leading to fatigue failure. This topic was studied taking advantage of innovative measurement systems developed for assess...

A machine learning technique was used to monitor the state of damage of steel specimens subjected to cyclic contact fatigue tests and to make a continuous measurement without coming into contact with the specimens examined. Six different sets of specimens were considered and the torque and vibration data obtained from their respective tests were an...

An improved railway wheel steel containing higher contents of C, Mn, Si, and V than the traditional ER7 steel was developed by alloy design for shoe-braked high-speed train applications. The effects of the thermal load on the microstructure and mechanical properties of a wheel made from this steel were investigated using a combined experimental and...

The Bronze Age crossbar wheel found in the XIX century in Mercurago (Italy) is an amazing example of the technical innovations stimulated by the diffusion of horse draught war chariots in Europe across the third and second millennium b.C. In this paper the tools of modern engineering were used to study the structural issues concerning the wheel and...

Twin-disk tests are an effective method to characterize the material response to rolling sliding contact, to reproduce the damage phenomena of real components at a laboratory scale in controlled working conditions. Usually the monitoring is performed by means of “gross” parameters, such as weight loss, coefficient of friction and Barkhausen noise,...

Unidirectional plastic strain accumulation (ratcheting) is one of the main causes of surface crack nucleation in rails and wheels in dry condition. It is related to frictional forces which develop at the contact interface due to sliding, especially in curve and in braking. Surface cracks generated by ratcheting can subsequently lead to severe damag...

The interaction between wear and rolling contact fatigue in wet contact was investigated by means of experiments on a two-disk test bench. Specimens of various railway wheel steels were coupled with specimens of the same rail steel, subjected to rolling and sliding wet contact with varying sliding/rolling ratio. Some tests with a dry rolling–slidin...

The Bronze Age crossbar wheel found in the XIX century in Mercurago (Italy) is an amazing example of the technical innovations stimulated by the diffusion of horse draught war chariots in Europe across the third and second millennium B.C. It is a tripartite wheel, with two felloes attached to a diametric crossbar by means of internal dowels, and fo...

We present the in-field use of a recently developed on-line, real time, optical monitoring system for bi-disk rolling contact tests on railway-wheel- and rail- steel disks, based on laser illumination and a high-speed camera. Qualitative, as well as quantitative information can be obtained by the use of specific indexes derived from the images usin...

An experimental investigation was carried out to study and compare the response to cyclic loading of the high-performance railway wheel steels ER8 EN13262 and SUPERLOS®. Rolling contact tests were performed with the same contact pressure, rolling speed and sliding/rolling ratio, varying the lubrication regime to simulate different climatic conditio...

This work studies the effect of desert sand at the wheel-rail contact interface on two standard railway wheel steels (ER8 and CLASS C) and two upgraded steels (SANDLOS® S and SANDLOS® H) specifically designed for sandy environments. Rolling contact tests were carried out by means of a two-disc testing machine with and without sanding at the contact...

The goal of this paper is to investigate the failure of a mandrel pin mounted on a rolling contact test bench. For this purpose, different methods of analysis were conducted, including metallography and stress analysis. The stress values in the failed pin were determined by Finite Elements. The high notch effect and the incorrect mounting of the sp...

Shear propagation of subsurface cracks under rolling contact fatigue was investigated on quenched and tempered SAE 5135 gear steel. The formation of subsurface cracks almost parallel to the contact surface was observed, highlighting the de-attachment of micro-particles from the cracks surfaces due to shear. Subsequent wear and plasticization proces...

Rolling contact fatigue (RCF) plays a critical role in railway components, and the characterization of materials used, in terms of RCF life, is still an open task, made complex by the interactions of different phenomena. The contact surface has a direct impact on the pressure exerted and can change during the test, due to wear. The procedure propos...

The assessment of damage in rail-wheel cyclic contact requires considering the combined action of different damage mechanisms, such as wear, ratcheting, surface or subsurface crack nucleation and propagation. Models, usually requiring experimental calibration, are available for assessing these phenomena. The best way to calibrate them is based on c...

A procedure for damage assessment in wheel–rail contact is still an open task: much work has been done for understanding failure mechanisms such as wear, cyclic plasticity and Rolling Contact Fatigue, but only recently the competition between them has been taken into account. In this study, a numerical procedure for damage assessment of railway whe...

Rolling contact fatigue (RCF) plays a critical role in railway components, and the characterization of materials used, in terms of RCF life, is still an open task, made complex by the interactions of different phenomena, such as wear, cyclic contact, and ratcheting. The presented case study regards a bi-disk test bench, used to evaluate the RCF beh...

A procedure for wheels and rails material characterization is still an open task in railway industry. Common standardized procedures, both for calculations and experimental characterization of materials and components, are usually founded on empirical models, or on simple and controlled damage phenomena, such as wear, unidirectional or bidirectiona...

Viene proposta una procedura di calcolo per la caratterizzazione di acciai per ruote e rotaie ferroviarie, considerando la complessa interazione tra i diversi meccanismi di danneggiamento che possono presentarsi in esercizio. Utilizzando un banco bi-disk sono state eseguite prove di fatica per contatto ciclico su coppie di provini di acciaio ruota...

Deforestation is one of the most dramatic threats to environmental equilibrium and food safety in many regions of the world, and particularly in sub-Saharan Africa. It is enhanced by many kinds of human activities, among which is the earth brick-firing process that needs large amounts of wood for attaining and maintaining temperatures required duri...

Subsurface crack mode II propagation parallel to the contact surface is a damage mechanism leading to dramatic failure in many components subjected to cyclic loading. A weight function (WF) was elaborated for calculating the applied mode II stress intensity factor (SIF) of a crack in a two-dimensional half-space in plane strain condition, for crack...

A failure assessment diagram for components subjected to rolling contact with hardness varying along the depth is presented.The approach takes into account the influence of inherent defects on subsurface fatigue: considering a 2D plane strain model, crack propagation from inherent defects was assessed in terms of applied stress intensity factor; de...

Wear and rolling contact fatigue were investigated on unfilled PEEK and on three PEEK short fiber reinforced composites. For this aim, roller-shaped specimens were subjected to rolling contact tests at different contact pressure levels. Wear rate-pv product and contact pressure-life diagrams were obtained, depending on material hardness. Microscopi...

Access to modern energy services is still low in developing countries and this lack of access affects in particular the Least Developed Countries (LDCs) and sub-Saharan Africa. The large majority of population in the Logone Valley at the border between Chad and Cameroon still relies on wood fuel burnt in smoky and inefficient fireplaces for cooking...

The paper presents an extension to finite life of a failure assessment diagram recently proposed for components subjected to rolling contact loading. The approach considers inherent defects, like inclusions, as potential sources of crack initiation and propagation. A predictive model based on the critical distance theory was proposed for this aim,...

A development of a failure assessment diagram for the evaluation of the safe working area of components subjected to rolling contact loading is here presented regarding the application to components whose hardness varies along the depth. The approach takes into account the influence of inherent defects in determining subsurface rolling contact fati...

Rolling contact fatigue tests were carried out on ring specimens made of quenched and tempered SAE 5135 gear steel with three different steel-production processes, through a bi-disc machine under pure rolling condition and water lubrication. Early formation of micro-pits then coalescing into macro-pits was observed on the rolling surface, while the...

The paper presents a ratchetting model, based on the non-linear kinematic-isotropic hardening law of Leimatre and Chaboche, able to predict the shear strain accumulation during rolling contact loading and including wear as a competitive phenomenon. A procedure was proposed to calibrate the model with the material constants suitable for rolling cont...

In many developing countries wood is the main energy source, and its exploitation is accelerating deforestation and desertification. In order to reduce wood consumption, an innovative biomass press was designed, aimed at providing alternative fuel by compacting dry waste biomass. The machine is based only on mechanisms, and can work by animal power...

The paper describes a prototype of a low-budget, low-power Ringbom-Stirling engine which contains air as the working fluid. This solution is being investigated as it seems appropriate for electric energy production in non-grid-connected locations of developing countries. The engine is thought to be heated with biomass from agricultural wastes eithe...

In many isolated settings electricity is not available or is supplied by fossil fuels, while biomass is used for cooking purposes, not exploiting all of its potential. We are building a prototype of a biomass powered 1kWel Ringbom-Stirling engine that doesn't require high technology, but nevertheless brings relevant innovations. This solution aims...

A previously published model for plasticity assessment in rolling contact, based on a simplification of the non- linear kinematic and isotropic hardening model of Chaboche and Lemaitre, is discussed, and an update is introduced in order to improve its accuracy in the plastic strain prediction within the region just underneath the contact surface. T...

Recent studies of the rail—wheel interface have shown that wear and rolling contact fatigue (RCF) are competitive phenomena. Wear, by removing the material from the contact surface, tends to limit the propagation of cracks formed by cyclic contact stresses. Several parameters influence these phenomena. This article studies the effects of various wo...

A model for plasticity assessment in rolling contact is introduced, aimed at simulating the effect of the application of thousands of load cycles in a reasonable time. It is based on the non-linear kinematic and isotropic hardening model of Lemaitre and Chaboche in a simplified formulation suitable for contact problems and allows the calculation of...

Wear and rolling contact fatigue interaction in rolling/sliding contact is an important topic in the research on structural integrity of rails and railway wheels. Wear is in competition with rolling contact fatigue, as it removes surface material layers, reducing cracks length and hindering their propagation. Cracks nucleate by accumulation of cycl...

An animal traction piston press was studied for applications in developing countries, aimed at producing biomass briquettes as alternative household fuel. Experiments were carried out with different biomasses for determining the minimum compaction pressure and the relationship between applied pressure and volume reduction. Two cams were designed fo...

A model for assessing wear and rolling contact fatigue (RCF) in rails is proposed, with particular emphasis for their competitive role.RCF was studied taking into account different mechanisms of crack nucleation and propagation in different working conditions, and failure indexes are proposed to predict which damage mechanism prevails.Wear was inve...

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Different damage phenomena can occur in components subjected to cyclic contact, depending on material properties and working condition. These phenomena can occur also simultaneously and competitively, and the final failure is due to the prevalent mechanism. The damage mechanisms occurring in RCF can be roughly divided into three families: surface o...

The general properties of a mode II Weight Function for a subsurface crack in a two-dimensional half-space are discussed. A general form for the WF is proposed, and its analytical expression is deduced from the asymptotic properties of the displacements field near the crack tips and from some reference cases obtained by finite elements models. Alth...

The competitive aspect of surface and subsurface fatigue crack propagation in hardened components subjected to rolling contact fatigue is highlighted, the former being greatly affected by the working conditions (in particular the presence of tangential stresses and lubricant), the latter depending mainly on the inclusions content and on the hardnes...

Different failure mechanisms are possible in cyclic contact phenomena, from wear to surface or subsurface fatigue. The limit of the material elastic shakedown is a critical parameter, because an early failure has to be expected when it is exceeded. It depends on all the tribological quantities involved in the process, which determine the effective...

Sommario Questo lavoro presenta il progetto di una pressa pe r la compattazione di biomassa di scarto, finalizza ta a produrre combustibile alternativo alla legna nei Paesi in via di sviluppo, specialmente quelli minacciati dalla deforestazione. La compattazione a vviene per estrusione ad alta pressione della biomassa tramite l'azione di un pistone...