# Study on the Influence of Collision Scene on the Energy Dissipation Process for Train Collision
## 4 Analysis of Train Collision Response
### Collisional Kinetic Energy Dissipation Process  
The variation of collision kinetic energy with time indicates the process of energy dissipation in the whole collision system. The faster the collision kinetic energy dissipates, the more intense the energy dissipation process is, and the greater the acceleration change of the vehicle is. Under the action of inertial force, the a greater possibility of secondary collision between the occupant and vehicle equipment. Therefore, in the design of train crashworthiness, the dissipation process of train collision energy also needs to be paid attention to. Based on this, the concept of energy dissipation rate is proposed to demonstrate the intensity of energy change. The energy dissipation rate refers to the change rate of collision kinetic energy with time during the collision process. The calculation method is as follows,  
\[P_{t}=\frac{dE_{kineticenergy}(t)}{dt} \tag{2}\]  
In the formula, \(P_{t}\) represents the energy dissipation rate at time \(t\) during the train collision, and \(E_{kineticenergy}(t)\) represents the kinetic energy of the train at time \(t\). In the collision scenarios of 1, 2, 3 and 4, the energy dissipation rate curves during the EMU train (8 units) collision, the coupler force curves of the interface 0, 1, 2 and 3, and the compression displacement curves of the interface 0 and 1 are demonstrated in Figure 6. On the whole, the energy dissipation process of train collision is divided into three stages: stage 1 shows the steady-state dissipation process, stage 2 shows a rapid dissipation process with variable amplitude, and stage 3 indicates a stepwise slow dissipation process. The EMU train (8 units) is taken as an example to describe the changes in each stage. Stage 1 is the initial collision stage. The couplers of the head car and middle car crush stably to absorb the collision kinetic energy with a smaller amplitude of energy dissipation rate. The peak values 1, 2 and 3 correspond to the coupler crushing tubes at the interface 0, 1 and 2, respectively, participating in energy dissipation. In this stage, the compression displacement of interface 0 increases rapidly, whereas the compression displacement of the intermediate interface 1 increases slowly. \begin{table}
\begin{tabular}{c c c c c} \hline
**Speed (km/h)** & **Scenario 1** & **Scenario 2** & **Scenario 3** & **Scenario 4** \\ \hline Train A & 36 & 42 & 25 & 18 \\ Train B & 0 & 6 & \(-11\) & \(-18\) \\ Relative & 36 & 36 & 36 & 36 \\ collision speed & & & & \\ \hline \end{tabular}
\end{table} 
Table 5: Initial speeds of trains in scenarios 1, 2, 3 and 4. Stage 2, the primary energy-absorbing device of the head car, participates in energy dissipation. In addition to interfaces 1 and 2, the middle interface 3 also participates in energy dissipation synchronously. Therefore, the energy dissipation rate increases rapidly. The peak of energy dissipation rate occurs when intermediate interface energy absorption devices are involved in energy dissipation. In this process, the compression displacement of interface 0 and interface 1 increases extremely to approach the maximum value, and then stage 3 appears, and the energy dissipation rate gradually decreases. In stage 3, with the progress of collision, the compression displacement of interfaces of 0 and 1 gradually reaches the maximum (taking interfaces of 0 and 1 as examples here), and the maximum energy dissipation of the interface arises. Meanwhile, the overall energy dissipation rate gradually decreases with a step-by-step oscillation variation trend. Furthermore, the energy dissipation rate curves in the process of train collision under collision scenarios 1, 2, 3 and 4 basically coincide on the whole; the transformation processes of collision kinetic energy under the four scenarios are basically consistent. It can be seen from Figure 7 that the EMU train (16 units and 8 units) possesses the same change trend of energy dissipation rate curves and a similar energy dissipation process, which is no longer elaborated in detail.