**3. Rail-wheel analysis**

The railway train comprises of engine and number of wagons. The engine has 12 wheels, 6 axles. The wagon has eight wheels, 4 axles. This is the description of Indian Railways. Below **Figure 3** explains the rail cross section. Main parts of rail are


Rail track is an important part of the railways which gives persistent and level surface for movement of the train made up of steel. Rail act as guide for the wheels in a lateral manner. When wheels of the wagon rotates on the rail there are certain forces exerted on the surface of the rail and different static and dynamic stress and strain are developed on the rail. The stress distribution is an important factor at the rolling interfaces between rail-wheel which depends on the geometry of the contacting surfaces, loading and boundary conditions and material properties of wheel and rail as given in [11].

Defects on the rail surface occur due to the cracks generated by repeated passage of trains and may increase with time. When wheel rotates on the rail track the contact between the wheel and the rail, many problems may arise which are

**Figure 3.** *Rail-wheel model.*

*Smart Monitoring of Flat Wheel in Railway Using Optical Sensors DOI: http://dx.doi.org/10.5772/intechopen.97847*


The wheel and rail interaction can be carried out by different methods


### **3.1 Hertz theory**

Railway wagon is a complex mechanical structure with body, wheel and axle as three main parts. It has several degree of freedom which includes linear and nonlinear springs and various types of damping system. When wheel rotates on the rail, different forces acting on the rail surface are vertical forces, horizontal longitudinal and transverse forces as given in [12].

**Figure 4** gives the various forces acting on the railway track. The static force acting on the mass is the weight of bogie and car (*mb* + *mc*)gand Hertzian spring acting in the wheel/rail contact area is kHz. The 1/4 bogie model is a two-mass model, in which the other mass (mass of wagon *mb*) is added over the mass in the 1/2 axle model that simulates the structure of the bogie, between the two masses is located the vehicle's primary suspension (k1, c1), and the static force acting on the superior mass is the weight of the car mcg.

**Figure 5** describes the vehicle model as given in [13]. The 1/8 vehicle model is a three-mass model, in which the other mass (mass of wagon *mc*) is added over the masses of the 1/4 bogie model that simulates the box of the vehicle, the vehicle's secondary suspension (k2, c2) is located between the upper masses.

#### **3.2 FEA analysis using ANSYS software**

Ansys 15.0 is a mechanical tool to perform finite element analysis (FEA) for structural analysis. Different types of model can be designed and analysed using this software [14]. The ANSYS software can be used for Finite Element Analysis of rail-wheel part. It has three working sub parts. They are

**Figure 4.** *Different forces applied on the rail.*

**Figure 5.** *Vehicle model.*
