As the main energy absorbing area of a railway vehicle, the front-end structure is critical to reduce the collapse of the passenger area and increase the safety of the vehicle in case of collision. In this paper, a front-end structure with integrated energy absorbing is introduced in detail as well as the iteration process. The front-end structure is mainly composed of anti-climber, collision posts, corner posts and four kinds of crush elements including center crush elements, side crush elements, interior crush elements and head girders. The shape, dimension, position, connection and material of those components are optimized multiple times based on the finite element analysis results of various load cases. The finalized structure can provide progressive controlled collapse with energy absorbing capacity of 1.22MJ and impact force less than 4450kN. At the same time, it is capable to withstand a static longitudinal load of 1224kN and vertical load of 334kN. To validate the design and analysis, the front-end structure is manufactured and tested under impact. The crash velocity, deformation and impact force show great agreement between the simulations and test results. From the design and optimization of this front end structure, it is concluded that placing the crush elements behind the collision post is beneficial for static strength design, the energy absorbing capability can be largely increased without taking additional space by using interior crush element and the geometry of the head girders plays an critical role in balancing the force distribution and providing stable crush performance.
The development of a multi-axial failure criterion for trabecular skull bone has many clinical and biological implications. This failure criterion would allow for modeling of bone under daily loading scenarios that typically are multi-axial in nature. Some yield criteria have been developed to evaluate the failure of trabecular bone, but there is a little consensus among them. To help gain deeper understanding of multi-axial failure response of trabecular skull bone, we developed 30 microstructural finite element models of porous porcine skull bone and subjected them to multi-axial displacement loading simulations that spanned three-dimensional (3D) stress and strain space. High-resolution microcomputed tomography (microCT) scans of porcine trabecular bone were obtained and used to develop the meshes used for finite element simulations. In total, 376 unique multi-axial loading cases were simulated for each of the 30 microstructure models. Then, results from the total of 11,280 simulations (approximately 135,360 central processing unit-hours) were used to develop a mathematical expression, which describes the average three-dimensional yield surface in strain space. Our results indicate that the yield strain of porcine trabecular bone under multi-axial loading is nearly isotropic and despite a spread of yielding points between the 30 different microstructures, no significant relationship between the yield strain and bone volume fraction is observed. The proposed yield equation has simple format and it can be implemented into a macroscopic model for the prediction of failure of whole bones.
Brake is a safety critical system for railway vehicles and brake failures have caused many catastrophic accidents in the history. Detailed accident investigation reports are available and National Transportation Safety Board (NTSB) also makes safety recommendations to Federal Railroad Administration and the industry. However, there is limited research on how to improve the brake safety from the perspective of design, system integration and safety analysis. In this paper, a framework for braking safety design and analysis is introduced, which includes four parts: failure alarming system, safety design, safety analysis and preventative maintenance. For failure alarming, according to the severity level, the failures will be notified to the operator, to Operation Control Center (OCC) or saved for the maintainer. For safety design, redundant design for fail-safe feature, automatic braking, brake release, weight control, ergonomics design for easy operation and maintenance are discussed and several application examples are illustrated. In the safety analysis section, Preliminary Hazard Analysis (PHA) as a semi-quantitative analysis, Failure Modes, Effects, and Criticality Analysis (FMECA) as a bottom-up method and Fault Tree Analysis as a top-down method are used. The hazards details, system assurance actions and closure references are recorded in the Hazard Tracking Log (HTL) to ensure all the safety related items are well tracked and documented. Preventative Maintenance (PM) which is regularly performed on the brake components to lessen the likelihood of failing is also discussed in combination with the reliability prediction and safety analysis for a balance of safety and economy. The safety design framework and principles introduced in this paper can also be applied into other railway systems, such as Propulsion, Signaling, Doors, etc. and may provide insights to similar industries such as automotive, energy and so on.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.