PSI - Issue 17

Eduardo A. Lima et al. / Procedia Structural Integrity 17 (2019) 246–253 Eduardo A. Lima/ Structural Integrity Procedia 00 (2019) 000 – 000

247

2

1. Introduction

The growth of railway transport in Brazil is an ongoing objective of the commodities companies. It happens due to the country large territorial extension and necessary movement of commodities. One of the main transported items is ore, and Carajás Railroad (EFC) is the leading track in this task. Ore makes up 74.2% of the all transported goods in Brazil (CNT, 2019). Due to the heavy-haul freight operations required by this type of commodity, each component of the train requires attention, especially the railway wheel. The wheel is a component that is susceptible to many failure mechanisms and, when the load is high, the main one is known as shelling. Shelling can be defined as material loss of the wheel tread due to rolling contact fatigue. Shell cracks begin near the surface and grow at an approximate 45° angle to the wheel tread (Stone, 2008). This subsurface fatigue defect type is a common phenomenon and has been occurring on the EFC over the years . In both forged and cast wheels, the thermal treatment process is the last step of the manufacturing process. After this heat treatment process, a residual circumferential (hoop) compressive stress is developed in the wheel rim. Gordon (1998) claims that the residual hoop stress in the rim helps to prevent the formation of fatigue cracks and to retard their growth when they occur. According to Soares (2018) the heat treatments and material fatigue behavior have a strong influence on the fatigue life of railway wheels. In a work focused on the fatigue life of the railway axle, Hutař (2017) showed analyzed the effect of the residual stress and found that it increases the fatigue life of the axle, if compressive . The same conclusion is expected for railroad wheels, based on several previous works on the literature. This study employs the finite element method (FEM) to evaluate the stress and strain during the wheel-rail contact and considered the effect of residual hoop stress of the thermal treatment process. The fatigue life of the railway wheel before the crack arises is determined by the modified Dang Van high cycle fatigue criterion ( Santos, 2008).

Nomenclature α

thermal expansion coefficient constant of Dang Van criterion fatigue shear strength exponent

α DV

b’ C

s pecific heat

thermal conductivity

k p n

point

normal vector in plane defined by θ and Ø

N

number of cycles

t

time

T s e

temperature

fatigue limit in pure bending

σ H σ uts

hydrostatic stress

ultimate tensile strength shear stress amplitude

τ a

τ DV Dang Van stress τ DVmax maximum Dang Van stress τ e fatigue limit in pure shear τ f ’

fatigue shear strength coefficient

angle of definition of the plane with normal vector n angle of definition of the plane with normal vector n

θ

Ø

2. Methodologies A D- 38” class C wheel , freight profile, and a TR-68 rail type were modelled using finite element method. The 3D models were made in the commercial software ABAQUS and divided into two different types: the t hermal treatment model and the rolling model. The Dang Van model is used for fatigue life evaluation.