Time filter

Source Type

Lovere, Italy

Cantini S.,Lucchini RS | Beretta S.,Polytechnic of Milan | Carboni M.,Polytechnic of Milan
Rivista Italiana della Saldatura | Year: 2010

Rail service safety related topic is, now more than ever, a living matter with a focus on safety-critical components of rolling stock such as wheels and axles. This article, starting from an overview of the current European standardization, proposes some guidelines for a proper development of the in-service control plan of railway axles, with particular attention to the effectiveness of the chosen control and the reliability of its repeatability. Proper training aspects of non destructive testing personnel, devoted to the maintenance, are deliberately overlooked. To fill the lack of standardization on this matter, primary for assessing the reliability of the control, guidelines are now being discussed to define an univocal training scheme for the operators.

Cervello S.,Lucchini RS
International Journal of Fatigue | Year: 2016

Euraxles project was a European Research project brought over under the 7th European Frame Work and promoted by the European association of Railway Wheelsets manufacturers. The present paper is a dissemination of the main results achieved during the full-scale axles fatigue test campaign in which various axles configurations were tested. This experimental activity was part of the work package 3 of the Euraxles project.The main scope of WP3 was to provide new fatigue limits for the Standard steel grades considering also the effect of surface conditions that may be different from the normal newly machined axles, like surface corrosion that can appear during the service or surface blasting as a method to improve paint adhesion.The areas of the axles considered were the free body transitions or groves and the wheel seats where at high bending rates relative micro slips take place generating the so called fretting fatigue phenomena.The paper provides in the conclusions a comparison with the fatigue limits that are today included in the European Standards.Another aspect that is treated in this work is the stress concentration effect that takes place along the transitions where the body fatigue limit is verified. These parameters were measured by strain gauges during each test and used inside the Euraxle project to validate their estimation through FE model calculation. Also in this case a comparison is made with the stress concentration values reported in the EN Standards that appear to be underestimated. © 2016 Elsevier Ltd.

Beretta S.,Polytechnic of Milan | Carboni M.,Polytechnic of Milan | Cervello S.,Lucchini RS
Materialwissenschaft und Werkstofftechnik | Year: 2011

Railway axles are designed for an infinite life with admissible stress levels which correspond to generous safety factors applied to full-scale fatigue properties of materials. Nevertheless, in order to keep an adequate safety level for such a long-lasting component (an axle can typically run for ×106 km) subjected to surface deterioration or corrosion, the design is complemented by "damage tolerance" analyses, in which it is assumed that a flaw could grow under service loads, in order to define an appropriate inspection plan. The ultimate "damage tolerance" approach is to design an axle so that there is no need for periodic NDT inspections except those carried out at overhauls (the so called "one million miles axle"). The aim of this paper is to describe the application of this concept to the axle of a freight train comparing this new design concept with the traditional fatigue design. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mazzu A.,University of Brescia | Solazzi L.,University of Brescia | Lancini M.,University of Brescia | Petrogalli C.,University of Brescia | And 2 more authors.
Wear | Year: 2015

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 cyclic contact tests, as these represent the real working conditions more closely. However, some experimental information, such as microstructural changes or crack paths, can be obtained only by destructive methods at the end of the tests, and their evolution cannot be monitored; other parameters, such as the wear rate, can only be determined during time consuming breaks to the tests. In this work, non destructive measurements of vibrations, torque and Barkhausen noise were introduced as indicators of damage evolution in cyclic contact tests on a high performance steel for railway wheels, coupled with a rail steel. In particular, their correlation with surface state, wear rate, subsurface microstructure and presence of cracks was shown. © 2015 Elsevier B.V.

Mazzu A.,University of Brescia | Petrogalli C.,University of Brescia | Lancini M.,University of Brescia | Ghidini A.,Lucchini RS | Faccoli M.,University of Brescia
Civil-Comp Proceedings | Year: 2016

The interaction of wear and rolling contact fatigue (RCF) in railway wheel steels subject to wet contact was studied using experiments and numerical simulations. Both surface and subsurface fatigue was considered. The experiments were carried out by a two-disc machine with specimens of three different wheel steels, coupled with the same rail steel. Some couples were tested with fully wet contact with different sliding-rolling ratios, others in dry contact and subsequently in wet contact. In the dry-wet tests severe surface damage occurred after a few cycles during the wet phase; in fully wet tests both surface and subsurface origin RCF occurred at a higher cycle number than in mixed tests. The role of wear in delaying the occurrence of surface RCF was experimentally proven. The observed phenomena were evaluated by means of a numerical code aimed at simulating different concurrent phenomena in cyclic contact. © Civil-Comp Press, 2016.

Discover hidden collaborations