Enhancement of fatigue life of rail-end-bolt holes by slide diamond burnishing

The fatigue failure around rail-end-bolt holes is particularly dangerous since it leads to derailment of trains and consequently to inevitable accidents. It is well-known that the fatigue life of structural holed components, subjected to cyclic load, can be increased by generating compressive hoop stresses around the holes.
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Enhancement of fatigue life of rail-end-bolt holes by slide diamond burnishing Engineering Solid Mechanics 2 (2014) 247-264 Contents lists available at GrowingScience Engineering Solid Mechanics homepage: www.GrowingScience.com/esmEnhancement of fatigue life of rail-end-bolt holes by slide diamond burnishingJ. T. Maximov*, G. V. Duncheva, A. P. Anchev, I. M. Amudjev and V. T. KuzmanovDepartment of Mechanical Engineering, Technical University of Gabrovo, 5300 Gabrovo, BulgariaARTICLE INFO ABSTRACTArticle history: The fatigue failure around rail-end-bolt holes is particularly dangerous since it leads toReceived June 6, 2014 derailment of trains and consequently to inevitable accidents. It is well-known that the fatigueAccepted 17 June 2014 life of structural holed components, subjected to cyclic load, can be increased by generatingAvailable online compressive hoop stresses around the holes. These beneficial residual compressive stresses19 July 2014Keywords: significantly reduce the maximum values of the operating tensile stresses arising at the criticalRail-end-bolt holes points of the components and thus impede the formation of first mode cracks. A new approachFatigue failure to enhancement of fatigue life of rail-end-bolt holes has been developed. The approach involvesResidual stresses sequential drilling and reaming through a new combined tool and then slide diamondCold working burnishing by a new device. The technology implementation was carried out on machine tool.Finite element simulation The process of creating residual stresses has been studied both experimentally and numerically. The experimental study was conducted by means of a modified split ring method. A reliable finite element modeling approach to the slide diamond burnishing process was developed. On this basis, the process was optimized by means of a genetic algorithm. As a result, the optimal combination of the governing process parameters is established, which ensures both maximum depth of the compressive zone and maximum absolute values of the residual stresses. © 2014 Growing Science Ltd. All rights reserved.1. Introduction Railway transport is acquiring greater significance in the development of modern transport. Thistendency is a direct consequence from the energy and environmental crises. In this aspect researchdirected to higher safety, long life and economy of components composing railways, is becomingmore and more topical. Building of high-speed railway lines is related to the so-called continuously welded rails.However, bolted joint railways cannot be done away with by 100% – in broken country andcurvilinear railroad tracks they have no alternative. There are a large number of bolted rail joints inheavy lines and mountainous lines. In Bulgaria, for instance, bolted joint railroads are 64.4% of the* Corresponding author.E-mail addresses: jordanmaximov@gmail.com (J. T. Maximov)© 2014 Growing Science Ltd. All rights reserved.doi: 10.5267/j.esm.2014.7.0012482railwayr netw work and thheir overall extended llength is 47 760 km (Vaalkov and G Grozdanov, 2009). Twoojoint bars oor fishplatess and four bolts are uused to con nnect the ends of adjooining railss. When theeremainingr cconditions are a the samee, reliabilityy, service liffe as well ass maintenannce and repaair activitiessdependd on tthe state off componennts composinng rail join nts: rail end ds, joint barrs and bolt connectionss(Fig.( 1). The elements in a rail joiint are subjeected to cycclic and imp pact loads aas a result of o passing oftrainst (Cai et al., 20007). The dy ynamic charracter of lo oads causess fatigue inn material in i rail joinntcomponentsc s or railwayy axles and d respectiveely provokes originatin ng and grow wth of fatiggue cracks -mostlym arouund the bollt holes or notches, w which are naatural stresss concentraations(Cai et e al., 20077,TorabiT and A Aliha, 20133). A mode of failure inn bolted joinnts is fatigue crack inittiation and growth g frommthet bolt holees in the endd rail (Fig. 2). 2 rails fishpla ate bolt con nnections Fig. 11. Bolted raail joint com mponents 2 Typical cracks Fig. 2. c originnating at raiil-end-bolt hole The fatiggue failure around a ...