Crash Energy Management Research Articles

Multi-body dynamic modelling and simulations for train crashworthiness design analysis

ABSTRACT One of the most important issues for rail passenger vehicles is on occupant safety through vehicle crashworthiness. Crashworthiness, in terms of rail vehicle designs, is the capability to dissipate the crash energy in such a controlled fashion that the overall damage is inconsequential to passenger space. A case study on a popular city passenger train has been conducted using a multi-body formulation of a three-dimensional, non-linear rigid body dynamic train model. The simulated crash scenario details a one to eight vehicle train in a front-on collision onto a fixed block. The crashworthiness is measured in terms of the degree of impact energy absorption, vehicle deceleration, and passenger injury criteria. The results showed that in a single vehicle, the crash energy management systems (CEMS) adequately compensated for the effects of impact at a crash speed of 44.5 km/h and below. At higher speeds, it is projected that the energy crush zones will need significant structural increases in both its crush length and crush force. An increase in the crush length is normally preferred over the crush force so as to maintain the longitudinal deceleration gradient within a tolerable range to ensure passenger safety. The benefits of computational modelling and simulations should not be underestimated as it allows for a thorough appreciation of a sound appreciation of the crashworthy structures and energy absorbers within any rail vehicle during the initial periods of the design process.

Evaluation of Crash Energy Management of the First-Developed High-Speed Train in Indonesia

Crash energy management is an essential evaluation stage of passive safety systems for high-speed trains. As a part of crash energy management, crash energy absorption has been researched for the last decade. The development of its components has also been performed individually. This paper presents a numerical analysis of the configuration of an energy absorption system for high-speed trains developed in Indonesia. Three placement configurations of the energy absorption system were investigated using explicit dynamic analysis in ANSYS. Total energy absorption, deceleration pulse, and deformation length were considered in the evaluation of the numerical analysis results. The collision criteria used in this study were according to EN 15227 and CFR 238 standards. This study revealed that the existing design could fulfill the energy absorption and average deceleration pulse required by EN 15227. Nevertheless, the existing design could not fulfill the energy absorption and maximum deceleration pulse required by CFR 238. It was also indicated that by positioning the anti-climber slightly forward, changing the deformation force of the crush box, and adding an impactor, the quality of energy absorption and average deceleration pulse could be improved.

Frontal Vehicular Crash Energy Management Using Analytical Model in Multiple Conditions

When it comes to frontal vehicular crash development, matching the stiffness of the front-end structures reasonably, i.e., impact energy management, can effectively improve the safety of the vehicle. A multi-condition analytical model for a frontal vehicular crash is constructed by a three-dimensional decomposition theory. In the analytical model, the spring is used to express the equivalent stiffness of the local energy absorption space at the front-end structure. Then based on the analytical model, the dynamic responses and evaluation indexes of the vehicle in MPDB and SOB conditions are derived with the input of the crash pulse decomposition scheme. Comparing the actual vehicle crash data and the calculation results of the proposed solution method, the error is less than 15%, which verifies validity of the modeling and the accuracy of the solution. Finally, based on the solution method in the MPDB and the SOB conditions, the sensitivities of the crash pulse decomposition scheme to evaluation indexes are analyzed to obtain qualitative rules which guide crash energy management. This research reveals the energy absorption principle of the front-end structure during the frontal impact process, and provides an effective optimization method to manage the multiple conditions of the vehicle crash energy such as the FRB (frontal rigid barrier), the MPDB (mobile progressive deformable barrier), and the SOB (small overlap barrier).

Design and optimization of anti-climber device for light rail transit crash energy management system

The study of a new anti-climber structural concept for a light rail transit crash energy management system is intended to improve passive safety performance that reduces the risk of overriding during a car-to-car collision. The anti-climber design and configurations are optimized to achieve the best crashworthiness performances. Several model variations are created, to which design factors are assigned based on the L16 orthogonal array. The optimum configuration is estimated using Taguchi’s Robust Parameter method. The controlled variables’ influence on the performance is analyzed using the Analysis of Variance method. The results show that the optimum configuration for the system’s crash energy absorption and crashbox deformation performances are toothed ends-Al6061-T6-30 mm-lower offset with 1.5 dB gain and toothed ends-Al6061-T6-20 mm-lower offset with 3.3 dB gain, respectively. The most influential parameter is the anti-climber material (29.79%) for the system’s crash energy absorption performance and teeth thickness (50.26%) for the crashbox deforming performance.

Review on the design of an aircraft crashworthy passenger seat

In this article, a comprehensive overview of the global state-of-the-art in the development of aircraft passenger seat crashworthiness is presented. With the increasing use of aeroplanes as means of transport in everyday life, the probability of accidents and injuries has also increased. This trend makes the safety of human life a top priority for the airplane designers. Based on a large number of studies coming from different industrial branches, military organizations, and academic centers, this article presents a review of the crashworthiness of aircraft passenger seats from the aspect of research approaches, accident investigations, mechanism analysis of occupant injuries and aircraft damage, strategies of occupant protection, and crashworthy design (crash energy management design) and performance of aircraft structures during collision scenarios. Finally, the trends in scientific research regarding the improvement of aircraft seat structure design and material composition are summarized.

Energy absorption design for crash energy management passenger trains based on scaled model

Energy absorption design for crash energy management passenger trains based on scaled model

MEM vs. FEM: practical crashworthiness insights for macro element modelling applied to sub-assembly and full vehicle automotive structures

This paper proposes a modelling approach for integral vehicle structures, applied to frontal crash loading, based on the Macro element approach. Addressing the idealisation of complex sub-structures and full vehicle was through identification of critical parameters for conversion of validated FEM into MEM equivalents through sensitivity analyses. Two examples of impact onto rigid barriers are presented; 1). Frontal crash energy management system (consisting crush-can and longitudinal engine rail), impacting at 8.6 m/s and 2). A complete vehicle impact at 56 km/hr (15m/s). Both case studies predict key features of collapse, with force-time histories agreeing within ±10–15% against FEM. Case study 1 required a 3 second solution time versus 1.5 h (8CPUS) mass-scaled FEM (105k element). For Case study 2, MEM required 7.5mins versus 16.5 hrs for a 3 M element FEM vehicle. For all simulations, LS-DYNA R10.0 and Visual Crash Studio R4.0 used. Developing a framework to overcome accuracy/stability problems, together with issues related to robustness and error reduction is discussed. Model complexity was progressive, involving a-priori knowledge of collapse and/or analysing several sub-assemblies to guide idealisation. The level of agreement demonstrates the advantages of MEM as a complementary method to support conceptual vehicle design and offers significant advantages for design exploration, particularly across multiple crash certification cases. Highlights Idealisation of complex sub-structures into Macro element modelling (MEM) equivalents using high fidelity finite element models (FEM) Methodology based on critical parameters for conversion of validated FEM into MEM Proposed MEM conversion for complete vehicle frontal impact onto a rigid barrier Correlation of critical parameters with structural behaviour through sensitivity analyses MEM error in force-time histories within 10–15%, relative to high fidelity FEM FEM Solution times reduced from several hours to several minutes for MEM equivalents

Impact Attenuator Optimum Design for a FSAE Racing Car by Numerical and Experimental Crash Analysis

One of the most important requirements of the Formula SAE (Society of Automotive Engineers) race car design competition is that the car structure must guarantee a high protection level in case of frontal impacts, by preventing intrusions into the driver foot zone or dangerous deceleration levels. These functions are mainly performed by the impact attenuators, which have to guarantee a high specific energy absorption capacity (SEA) and in order to preserve vehicle performances, have to be as light weighted as possible. The aim of this study is the design of an impact attenuator, to be mounted on a Formula SAE car, which main purpose is to obtain the optimal crash energy management, maximizing the absorbed energy and optimizing the geometry. The outcome of the study highlights that the absorber structure made up of honeycomb sandwich panels (primary energy absorbers), realized by means of different aluminium alloys employing an innovative design considering particular geometrical cavities within the structure, could lead to reduce the overall weight and to achieve a more progressive deformation during the impact.

Optimization Design on Functionally Graded Cem for Trains Based on LPM Model with Calibrated Parameters

Lumped parameter modeling (LPM) combined with optimization techniques is an efficient approach for parametric configuration design of energy absorption to improve crashworthiness performance during train collision. This work proposed a simplified model by introducing a bar element to consider the influence of the carbody in a collision process. The optimization method is applied to calibrate the equivalent parameters of the bar element. Bar elements with calibrated parameters are adopted in establishing a one-dimensional (1D) model for the train crash. Subsequently, a novel crash energy management (CEM) mode with functionally graded energy (FGE) configuration is introduced to the train crash model for improving crashworthiness performance. The influence of parameters in graded function on interfacial force and peak acceleration is investigated and optimal design parameters are obtained by Nondominated Sorting Genetic Algorithm (NSGA-II). It is concluded that considering the behavior of the carbody can improve the accuracy of LPM in predicting the longitudinal response, and the gradient CEM is a potential energy configuration mode to improve the crashworthiness of the train in a collision.

Rail vehicle crashworthiness based on collision energy management: an overview

ABSTRACT This paper summarizes the research on passive safety of rail vehicles from the perspective of Crash Energy Management (CEM) in recent decades, which covers the analysis of main crashworthiness standards, as well as the latest research progress in theoretical methods, numerical simulation, and experimental technology of rail vehicles crashworthiness. According to the research status of each subject, some weak links and potential research suggestions are pointed out, such as the requirements of CEM in standards, the influence mechanism of the coupler under different collision speeds, structural compatibility and standardization of anti-climbers, the establishment of vehicle structure crashworthiness design method in design-simulation-test closed-loop system, etc. In the future, under the support of mature CEM theory, more detailed and reliable numerical simulation models, more comprehensive vehicle crash test data, and higher computer computing efficiency, the passive safety of rail vehicles will be guaranteed to the maximum extent.

Crashworthiness of passenger rail vehicles: a review

In this article, based on a broad review of the literature, a comprehensive overview of the global state of the art in the development of rail vehicle crashworthiness is presented. Following large number of studies on rail vehicles, this article presents a review of the crashworthiness of passenger rail vehicles from the aspects of research approaches, accident investigations, mechanism analysis of occupant injuries and train damage, strategies of occupant protection, and crashworthiness design (crash energy management design) and performance of rail vehicles in collisions. Finally, some conclusions and recommendations for future research are presented.

AHSS AUTO STAMPING CHALLENGES: RECTIFYING SPRINGBACK

To improve crash worthiness and fuel economy, the automotive industry is, increasingly, using Advanced High Strength Steel (AHSS). The main reason to utilize AHSS is their better performance in crash energy management, which allows one to down gauge with AHSS. In addition, these engineered AHSS address the automotive industry’s need for steels with higher strength and enhanced formability. The improved capabilities the AHSS bring to the automotive industry do not bring new forming problems but certainly accentuate problems already existing with the application of any higher strength steel. These concerns include higher loads on presses and tools, greater energy requirements, and increased need for springback compensation and control. Springback problem, consistently, is one of the leading roadblocks hindering auto stamping productivity. This paper describes the origins and types of springback, characterizes what causes it, and elaborates ways to rectify it through, stabilization, compensation, and verification.

Multi-cornered thin-walled sheet metal members for enhanced crashworthiness and occupant protection

Crash energy management in frontal crumple zone of the automotive body is one of the key elements for the design of automotive structure. Improving energy absorption characteristics reduces the magnitude of forces transferred to the occupant compartments. Here, a new strategy has been proposed to improve energy absorption efficiency of thin-walled columns by introducing extra stable corners in the cross-section. Several profiles of multi-corner thin-walled columns obtained through this strategy were presented and their crashworthiness capacities under axial crush loading were investigated analytically, experimentally, and numerically. First, explicit formulations for predicting the mean crushing force of multi-corner thin-walled columns were derived using the theory of super folding element (SFE). Predicted results of these formulations showed a good agreement with the results of quasi-static experiments and CAE simulations, which were performed by explicit non-linear finite element code through LS-DYNA. Based on this agreement, other significant crashworthiness assessment parameters were then investigated experimentally and numerically. Newly introduced 12-edge section with high energy absorption capacity was developed and its dominance was established through the responses in quasi-static experiments and CAE simulations. Finally, the foundational dominance of the 12-edge section was extended to the dynamic environment through a full vehicle crash test simulation to evaluate overall reduction in crashworthiness parameters which reflected occupant safety. Interestingly, in the case of using 12-edge section as crush absorbers, specific energy absorption (SEA), dash intrusion and maximum occupant’s chest deceleration showed significant improvement, compared to the baseline design which used a rectangular section.

Performance evaluation of vehicle front structure in crash energy management using lumped mass spring system

The design for vehicle structural crashworthiness which ensures that components of desired crash performance characteristics are used in product manufacturing essentially involves the evaluation of the energy absorption potentials of the structures using suitable computation method. Due to unresolved difficulties in achieving detailed results through the existing methods researchers seek for more alternative computation methods. Although previous efforts in this regard are quite significant, yet some concerns still exist on accuracy or computational efficiency achievable through the conventional methods. The lumped mass spring (LMS) method is applied in the present study. Some new steps were introduced in the basic procedure to improve the accuracy and computational efficiency of the method. A new dynamic stiffness formula is written in terms of the specific energy absorption indices of the structural components. The new procedure allowed for standard state-space formulation of the crash problem. The performance of the new simulation approach is tested for a typical vehicle structure in two possible orientations called normal mode and reversed mode. The results obtained for the impact problem in normal structural mode show that a desirable energy absorption pattern of 45%, 25% and 20% of the total impact energy could be achieved through plastic deformation of the front frame, sheet metal and torque box respectively. Testing the impact system in reversed structural mode results in a rather poor energy absorption pattern in which 2.5%, 50% and 43% of the total impact energy were absorbed through deformation of the front frame, sheet metal and torque box respectively, showing that unreasonably high percentage of the total impact energy is transmitted to the interior structures. The effort to quantify the energy absorbed by major vehicle front structure in both desirable and undesirable crash responses, and the computational efficiency achieved through the present method could help to enhance decision process during assessment of the components or prototype. It is found that good crash performance may be guaranteed by ensuring sufficiently high (up to 65%) contribution to the energy absorption scheme through the deformation of the foremost structures which includes the front frame and the sheet metal.

Progressive collapse of foam-filled conical frustum using kinematically admissible mechanism

A kinematically admissible mechanism is presented for the progressive collapse of a foam-filled and unfilled circular frustum. The mechanism uses a three-limb model of collapse for the frustum shell, taking into account the plastic strain and circumferential strain energy dissipation during collapse. For the foam-filled case, the energy dissipation due to the plastic collapse of the foam and the interaction effects between it and outer frustum shell were considered. To account for the interaction effects, a pressure equivalent to the stress plateau of the foam was applied only to the inward bending proportion of the frustum. This is the result of our extensive experimental studies, which shows that Poisson's effects are negligible and that there will be no transverse strains resulting from the axial collapse of the frustum. We have further conducted analysis of empty frustum. A comparative analysis for the developed mechanism and previously conducted experimental studies showed good agreement between the two. Lastly, a parametric study of the mechanism correctly predicts that the magnitude of the crushing load depends on the length and proportion of the inward folds. Our upper-bound model gives a closed form solution for the collapse of foam-filled and unfilled frusta that can be used for crash energy management in automobiles.

Development of a design for a crash energy management system for use in a railway passenger car

A design approach for a crash energy management (CEM) system for a N13-type railway passenger car used by the Turkish State Railway Company is developed in this paper. The components of the CEM system are honeycomb-structured boxes, primary energy absorbers, shear bolts, a sliding sill mechanism and a fixed sill mechanism that are located in the passenger-free space at the end of the passenger car. In order to investigate the benefits provided by the CEM system, a full-scale railway passenger car collision with a rigid wall is simulated by using dynamic/explicit finite element (FE) methods. The crushing force, secondary impact velocity, acceleration and velocity curves, and deformation modes are computed to allow a comparison of the crashworthiness performance of a passenger car equipped with the proposed CEM system with that of a conventional passenger car. Comparisons of FE analysis results show that a passenger car incorporating the CEM system has a superior crashworthiness performance to that of the conventional passenger car.

Use of Composite Metal Foam for Improving Absorption of Collision Forces

Studies devoted to understand the mechanical behavior of Composite Metal Foams (CMFs) have revealed superior energy absorption capacity under quasi-static loading. Accordingly, CMF is a great nominee to replace currently used materials in vehicles crash energy management system. However, in order to utilize the full capacity of CMF under impact loading, understanding its high strain rate behavior is needed. This paper seeks to investigate the strain rate sensitivity of CMF by conducting Split Hopkinson Pressure Bar experiments. The test samples were manufactured using powder metallurgy technique and the role of loading rate and sample size was studied. The obtained results shows high rate dependency of the stress-strain behavior and an improvement in energy absorption capacity under impact loading.

A Crashworthy Problem on Composite Structures Using a Mathematical Approach

Abstract During the last decades the attention given to vehicle crash energy management has been centred on composite structures. The use of fibre-reinforced plastic composite materials in automotive structures, in fact, may result in many potential economic and functional benefits due to their improved properties respect to metal ones, ranging from weight reduction to increased strength and durability features. Although significant experimental work on the collapse of fibre-reinforced composite shells has been carried out, studies on the theoretical modelling of the crushing process are quite limited since the complex and brittle fracture mechanisms of composite materials. Moreover most of the studies have been directed towards the axial crush analysis, because it represents more or less the most efficient design. A mathematical approach on the failure mechanisms, pertaining to the stable mode of collapse of thin-walled composite structures subjected to axial loading, is investigated. The analysis is conducted from an energetic point of view. The main energy contributions to the absorption (bending, petal formation, circumferential delamination, friction) are identifies and then the total internal energy is equated to the work done by the external load. The total crushing process can be seen as a succession of deformation states, each responsible for a partial absorption. The minimum configuration for each impact force in the specific state of deformation, function of several variables and dependent on geometric and material parameters is obtained. A comparison between theory and experiments concerning crushing loads and total displacements is presented, showing how the proposed analytical model is effective in predicting the energy absorption capability of axially collapsing composite shells.

Development of the Next Generation of Intercity Corridor Bi-Level Equipment with Crash Energy Management

An innovative rail car procurement specification was developed for bi-level equipment. This specification was developed to fulfill the Passenger Rail Investment and Improvement Act of 2008 (PRIIA). PRIIA is a congressional mandate to the National Railroad Passenger Corporation, state departments of transportation, FRA, and passenger rail car builders and suppliers to develop the next generation of passenger rail equipment for intercity corridor service for speeds up to 125 mph. Technological innovations are to be used to improve safety incrementally, and components are to be standardized to the extent possible to leverage economies of scale to help revitalize the manufacturing base for domestic passenger equipment. This paper focuses on the technical discussions held by a cross section of key industry stakeholders to develop specification language for crash energy management features as an overlay on a fully compliant bi-level car design. The purpose of the paper is to widely disseminate the methodology and process used and to provide background information on the values chosen for individual car crush zone performance.

Development of a novel material for improved crash energy management in collisions involving vulnerable road users

Correctly packaged, foam-filled fluids are a material technology that will lead to enhanced pedestrian safety. It is the combination of energy absorption mechanisms and how this combination can be altered by changes to the properties of the constituent components that provides significant opportunity for tailoring the response of the energy absorber to meet the different demands placed upon it. To date, the research stream has tended to focus on one-factor-at-a-time (OFAT) characterisation in order to develop an understanding of the individual energy absorption mechanisms present in the system. It is unlikely that the full implications of setting the design variables could be understood for such a complex system using an OFAT approach. An experimental design approach to the problem of characterising the response of foam-filled fluids is proposed. To demonstrate the applicability of this approach, the work presented here investigated four process parameters over a limited number of levels. Out of the four parameters, velocity and length were shown to be the significant process parameters determining peak load; velocity and capsule size were shown to be the significant process parameters determining deflection; and viscosity was shown to be the significant process parameter determining absorber efficiency. On the basis of the work presented, a methodology for simultaneous optimisation is proposed that will support the vehicle designer in the development of a foam-filled bumper system. The work is considered timely because of changes in regulations and will support the automotive industry and the requirement to design future vehicles that afford additional protection for pedestrians.