“…The stresses that still exist after unloading are residual stresses. As the longitudinal stress plays a key role in the initiation and propagation of rail fatigue cracks, 31,32 previous studies 15,33 focused on the longitudinal residual stress of rail, which this study also focused on. Figure 4.Shape of the wheel–rail contact patch during the first rolling pass.CNORMF: contact normal force (unit: MPa).Figure 5.Curve of the time-dependent stresses at point M at the first rolling pass. σ x : the vertical stress; σ y : the transverse stress; σ z : the longitudinal stress; and σ xy , σ xz and σ yz : shear stresses.…”
Section: Developments Of Residual Stress Of Railsmentioning
Rolling contact fatigue damage of rails is significantly influenced by residual stresses. A three-dimensional elastic-plastic finite element model of wheel–rail contact was established in the present study, and the influence of initial stresses resulting from rail manufacturing process on the residual stress distribution of rails was analyzed. The repeated rolling passes were simulated and the stable residual stress distribution of rails was obtained. The influence of factors, such as wheel load, friction coefficient, and longitudinal creep rate, on the residual stress distribution of rails was investigated. It is found that within the limited special scale affected by the wheel–rail contact, the difference between the longitudinal residual stress with initial stresses applied and that without initial stresses applied becomes quite small once enough rolling passes have occurred (i.e., 10 rolling passes). When the initial stresses are applied, the longitudinal residual compressive stress on wheel–rail contact center of the rail is approximately 500 MPa. The residual compressive stress decreases with the increasing depth and changes from compression to tension at the depth of 6 mm beneath wheel–rail contact center of the rail. The wheel load mainly affects the residual stress distribution along the depth direction beneath rail surface. The friction coefficient mainly affects the residual stress distribution on the rail surface. The longitudinal creep rate has a great influence on the longitudinal residual stresses at the surface and along the depth of the rail.
“…The stresses that still exist after unloading are residual stresses. As the longitudinal stress plays a key role in the initiation and propagation of rail fatigue cracks, 31,32 previous studies 15,33 focused on the longitudinal residual stress of rail, which this study also focused on. Figure 4.Shape of the wheel–rail contact patch during the first rolling pass.CNORMF: contact normal force (unit: MPa).Figure 5.Curve of the time-dependent stresses at point M at the first rolling pass. σ x : the vertical stress; σ y : the transverse stress; σ z : the longitudinal stress; and σ xy , σ xz and σ yz : shear stresses.…”
Section: Developments Of Residual Stress Of Railsmentioning
Rolling contact fatigue damage of rails is significantly influenced by residual stresses. A three-dimensional elastic-plastic finite element model of wheel–rail contact was established in the present study, and the influence of initial stresses resulting from rail manufacturing process on the residual stress distribution of rails was analyzed. The repeated rolling passes were simulated and the stable residual stress distribution of rails was obtained. The influence of factors, such as wheel load, friction coefficient, and longitudinal creep rate, on the residual stress distribution of rails was investigated. It is found that within the limited special scale affected by the wheel–rail contact, the difference between the longitudinal residual stress with initial stresses applied and that without initial stresses applied becomes quite small once enough rolling passes have occurred (i.e., 10 rolling passes). When the initial stresses are applied, the longitudinal residual compressive stress on wheel–rail contact center of the rail is approximately 500 MPa. The residual compressive stress decreases with the increasing depth and changes from compression to tension at the depth of 6 mm beneath wheel–rail contact center of the rail. The wheel load mainly affects the residual stress distribution along the depth direction beneath rail surface. The friction coefficient mainly affects the residual stress distribution on the rail surface. The longitudinal creep rate has a great influence on the longitudinal residual stresses at the surface and along the depth of the rail.
“…de trilhos e rodas ferroviárias [5][6][7]. Devido ao excesso de tensões decorrentes do contato entre a roda e o trilho, pode ocorrer a iniciação e a propagação de trincas na superfície dos trilhos, as quais podem originar defeitos e fraturas, dentre esses, destaca-se o spalling no boleto [8][9][10][11][12].…”
Section: Caracterização Da Estruturalunclassified
“…De acordo com [13], o spalling na superfície de contato dos trilhos é um defeito típico de RCF que interfere na manutenção da via além de acentuar as interações dinâmicas no sistema roda-trilho. O defeito surge com alguns milímetros de profundidade na pista de rolamento do trilho evoluindo gradativamente à medida que a roda ferroviária passa sobre sua região de localização [7,12]. Esta irregularidade na via causa vibração anormal no veículo ferroviário [13].…”
Publicado pela ABM. Este é um artigo publicado em acesso aberto (Open Access) sob a licença Creative Commons Attribution, que permite uso, distribuição e reprodução em qualquer meio, sem restrições desde que o trabalho original seja corretamente citado. a
ResumoDentre os defeitos provenientes de fadiga de contato de rolamento (RCF) nos trilhos ferroviários, o spalling se apresenta como um dos mais severos devido às suas características morfológicas. Este trabalho envolve a análise de um amostra de solda aluminotérmica de trilho ferroviário contendo um defeito do tipo spalling, nas caracterizações buscou-se fazer a correlação entre o defeito, a microestrutura e as propriedades mecânicas na região do trilho. Foram realizados ensaios de dureza e microdureza, além da caracterização microestrutural e fractográfica via microscopia óptica. Os resultados mostraram que o spalling possui uma forte tendência em ocorrer na região da Zona Termicamente Afetada (ZTA), expressa pela variação microestrutural e dureza ao longo da amostra e as trincas são influenciadas pela microestrutura deformada da superfície do trilho. Palavras-chave: Defeitos em trilhos; Caracterização; Fadiga de contato de rolamento; Spalling.
“…In recent years, increasing train speeds and axle loads have caused higher wheel-rail contact stress, which results in more fatigue cracks at the railhead, leading to significantly higher rail maintenance costs [2]. Moreover, if measures are not taken in time to restrain crack propagation, rail spalling and even breakage can eventually occur [3], severely threatening the operational safety of trains. Therefore, it is of great importance to study railhead fatigue crack propagation to ensure train operation safety and to reduce rail maintenance work.…”
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