# Effect of Control Measures on Wheel/Rail Noise When the Vehicle Curves
## 3 Results and Discussions  
### Wheel/Rail Noise Prediction and Preliminary Validation  
This section gives the wheel/rail force, acceleration and sound pressure level of the wheels under the wheel/rail force excitation with and without squealing phenomenon in a sharp curve. When a vehicle curves, the leading wheel (front wheel) has a potential to produce squeal and the trailing wheel (rear wheel) should not produce squeal. Figure 7 gives the lateral creep force of the leading wheelset when a vehicle runs from a tangent line to a narrow circular curve at the speed of 45 km/h. The curve radius is 250 m, and the track cant is 96 mm. The main physical parameters of the metro vehicle used in the simulations are given in Table 1. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Notations** & **Parameters** & **Values (End)** \\ \hline \(M/l\) & Body inertia & \\ \(M_{c}\) & Car body mass (kg) & 2.16 \(\times\) 10\({}^{4}\) \\ \(M_{b}\) & Bogie mass (kg) & 4.00 \(\times\) 10\({}^{3}\) \\ \(M_{w}\) & Wheelset mass (kg) & 1.86 \(\times\) 10\({}^{3}\) \\ \(I_{cx}\) & Car body roll moment of inertia (kg\(\cdot\)m\({}^{2}\)) & 3.11 \(\times\) 10\({}^{4}\) \\ \(I_{cy}\) & Car body pitch moment of inertia (kg\(\cdot\)m\({}^{2}\)) & 8.61 \(\times\) 10\({}^{5}\) \\ \(I_{cz}\) & Car body yaw moment of inertia (kg\(\cdot\)m\({}^{2}\)) & 8.56 \(\times\) 10\({}^{5}\) \\ \(I_{bx}\) & Bogie roll moment of inertia (kg\(\cdot\)m\({}^{2}\)) & 1.19 \(\times\) 10\({}^{3}\) \\ \(I_{by}\) & Bogie pitch moment of inertia (kg\(\cdot\)m\({}^{2}\)) & 8.76 \(\times\) 10\({}^{2}\) \\ \(I_{bz}\) & Bogie yaw moment of inertia (kg\(\cdot\)m\({}^{2}\)) & 2.10 \(\times\) 10\({}^{3}\) \\ \(I_{ux}\) & Wheelset roll moment of inertia (kg\(\cdot\)m\({}^{2}\)) & 1.04 \(\times\) 10\({}^{3}\) \\ \(I_{uy}\) & Wheelset pitch moment of inertia (kg\(\cdot\)m\({}^{2}\)) & 1.37 \(\times\) 10\({}^{2}\) \\ \(I_{uz}\) & Wheelset yaw moment of inertia (kg\(\cdot\)m\({}^{2}\)) & 1.04 \(\times\) 10\({}^{3}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Main parameters of metro vehicle. It can be seen from Figure 7 that the lateral creep force is very stable at tangent line. In addition, the fluctuation of lateral creep force increases gradually from transition curve to circular curve, and reaches maximum when the vehicle negotiates the circular curve. Figure 8 shows the lateral creep forces of leading and trailing wheels. It can be seen that the fluctuation of lateral creep force of leading wheel is larger than trailing wheel. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Notations** & **Parameters** & **Values (End)** \\ \hline \(K/C\) & Primary suspension & \\ \(K_{yx}\) & Longitudinal stiffness (MN/m) & 17.62 \\ \(K_{yy}\) & Lateral stiffness (MN/m) & 9.62 \\ \(K_{yz}\) & Vertical stiffness (MN/m) & 0.60 \\ \(C_{yz}\) & Vertical damping coefficient (kN-s/m) & 13.00 \\ \(K/C\) & Secondary suspension & \\ \(K_{xx}\) & Longitudinal stiffness (MN/m) & 0.16 \\ \(K_{yy}\) & Lateral stiffness (MN/m) & 0.16 \\ \(K_{zz}\) & Vertical stiffness (MN/m) & 1.39 \\ \(C_{yy}\) & Lateral damping coefficient (kN-s/m) & 23.00 \\ \(C_{zz}\) & Vertical damping coefficient (kN-s/m) & 25.00 \\ \hline \(L/D/H\) & Dimension & \\ \(R_{w}\) & Wheel radius (m) & 0.42 \\ \(L_{v}\) & Vehicle length (m) & 19.5 \\ \(L_{b}\) & Distance between two axes of a bogie (m) & 2.3 \\ \(L_{c}\) & Distance between two bogie centers (m) & 12.6 \\ \(D_{ps}\) & Lateral span of primary suspensions (m) & 2.01 \\ \(D_{ss}\) & Lateral span of secondary suspensions (m) & 1.9 \\ \(H_{bw}\) & Height of bogie centre from wheelset centre (m) & 0.069 \\ \(H_{cb}\) & Height of car body centre from bogie centre (m) & 1.37 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: _Cont._  
Figure 7: Lateral creep force of the leading wheelset when a vehicle negotiates a narrow curve (simulation results). Figure 9a,b give the acceleration of leading inner wheel and trailing inner wheel in time domain and frequency domain.