Key Takeaways & Executive Findings
- •• A novel multi-layer progressive analysis method decomposes train collision energy flow into conversion, dissipation, and transfer layers, enabling systematic understanding of energy distribution. • Power flow theory-based modeling reveals that collision energy decays by 79% along the train operation direction, highlighting the dominant role of energy dissipation in the front structures. • The study identifies that even when mean acceleration meets standards, jerk can exceed human tolerance, posing secondary collision injury risks—critical for occupant safety design. • Energy convergence in perforated structures leads to localized deformation when accumulated energy exceeds structural capacity, guiding crashworthiness optimization.
Abstract
The huge impact kinetic energy cannot be quickly dissipated by the energy-absorbing structure and transferred to the other vehicle through the car body structure, which will cause structural damage and threaten the lives of the occupants. Therefore, it is necessary to understand the laws of energy conversion, dissipation and transfer during train collisions. This study proposes a multi-layer progressive analysis method of energy flow during train collisions, considering the characteristics of the train. In this method, the train collision system is divided into conversion, dissipation, and transfer layers from the perspective of the train, collision interface, and car body structure to analyze the energy conversion, dissipation and transfer characteristics. Taking the collision process of a rail train as an example, a train collision energy transfer path analysis model was established based on power flow theory. The results show that when the maximum mean acceleration of the vehicle meets the standard requirements, the jerk may exceed the allowable limit of the human body, and there is a risk of injury to the occupants of a secondary collision. The decay rate of the collision energy along the direction of train operation reaches 79%. As the collision progresses, the collision energy gradually converges in the structure with holes, and the structure deforms when the gathered energy is greater than the maximum energy the structure can withstand. The proposed method helps to understand the train collision energy flow law and provides theoretical support for the train crashworthiness design in the future.
1. Introduction
The rapid development of rail vehicles has brought great convenience to people's travel. However, train collisions cannot be avoided due to factors such as natural environmental changes, equipment failures and personnel operational errors. As a multi-vehicle coupled system, collision energy changes exist in energy dissipation in multi-stage crashworthy structures, kinetic energy conversion between vehicles, and energy transfer in the car body structure. In the process of conversion, dissipation and transfer, the initial collision kinetic energy of the train gradually decreases, which is irreversible. Using the concept of energy flow in the food chain as a reference, the kinetic energy conversion, energy dissipation and energy transfer during a train collision are collectively referred to as energy flow.
Previous studies have paid to the refined train collision dynamics modeling method [1–3], the prediction of the energy absorption characteristic curve of the energy absorption structure at the end of the train based on the new method [4, 5], the influence of different collision scenarios on the dynamic characteristics of the occupant and the energy dissipation process of the energy absorption structure [6–8], and the bionic design and optimization of the energy absorption structure at the end of the train [9]. The energy conversion process between two train systems, the transfer and attenuation law of collision energy within the car body structure and the influence of collision energy on the deflection behavior of the car body structure has been neglected.
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Jingke Zhang, Tao Zhu, Xiaorui Wang, Bing Yang, Shoune Xiao, Guangwu Yang, Yuru Li (2025). A Multi-Layer Progressive Analysis Method for Collision Energy Flow in Rail Trains. Chinese Journal of Mechanical Engineering. https://doi.org/10.1186/s10033-025-01353-0
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Frequently Asked Questions
What is the multi-layer progressive analysis method for train collision energy flow?
The method divides the train collision system into three layers: conversion, dissipation, and transfer, corresponding to the train, collision interface, and car body structure. It analyzes energy conversion, dissipation, and transfer characteristics systematically, using power flow theory to model energy paths.
How does collision energy decay along the train?
The study found that the decay rate of collision energy along the direction of train operation reaches 79%, meaning most energy is absorbed or dissipated in the front sections, reducing energy transfer to rear vehicles.
What are the implications for occupant safety?
Even when the maximum mean acceleration meets standards, the jerk (rate of acceleration change) can exceed human tolerance limits, posing a risk of injury from secondary collisions. This highlights the need to consider jerk in crashworthiness design.
How does the method support crashworthiness design?
By revealing energy flow laws, the method helps identify critical energy-absorbing structures and potential weak points, guiding the design of energy-absorbing structures and car body to improve crashworthiness and occupant protection.
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