Crashworthiness Safety Research Articles

Failure mechanisms and acoustic responses of cylindrical lithium-ion batteries under compression loadings

To understand the crashworthiness safety of lithium-ion battery (LIB) comprehensively, acoustic emission (AE) testing technology is introduced to explore the mechanical response and failure mechanism. In this paper, the compression process and failure behavior of 18650 LIBs under plane compression, local indentation and three-point bending are experimentally investigated. The effects of indenter diameter, state of charge (SOC) and capacity of the battery on the force-voltage-temperature responses are discussed in detail. The relation between the failure behavior and acoustic response of LIB is studied in combination with AE detection technique. The results show that the deformation of the battery can be divided into three stages before the failure, including the stress on the shell, compression on the internal gap and electrolyte, and stress on the whole. The failure inside the battery is caused by fold, shear fracture, local buckling and tensile break under different loading forms. The smaller the diameter of the indenter is, the lower bearing capacity at the point of failure is. High-SOC batteries experience higher forces and displacements at the failure point. High-capacity batteries have poor bearing capacity and are more prone to thermal runaway. AE signal can be detected at special points during the compression. Combined with the acoustic response of the battery, the whole deformation process is divided into five stages. The researches will provide a guidance for the failure detection and safety evaluation of LIBs.

Quasi-static crush response of lightweight sandwich composite tubes fabricated via newly designed internal thermal expansion technique

Different from conventional unidirectional outward-inward forming methods, this study employs a multidirectional internal expansion shaping approach to fabricate lightweight sandwich composite tubes. Integrating carbon fiber reinforced polymer (CFRP), thermal expansion foam and polymethacrylimide (PMI) foam, the sandwich composite tubes demonstrate adaptability in terms of material properties as validated through several experimental trials. The one-step molding process eliminates the requirements for subsequent structural assembly and bonding, while ensuring adhesion between diverse material components. The sandwich composite tubes exhibit superior impact resistance, showcasing a stable progressive crushing failure. The energy absorption mechanism shifts from single CFRP damage to a multi-material composite energy absorption mode. The specific energy absorption (SEA) value of designed sandwich composite tube is up to 102 J/g. The sandwich composite tubes fabricated in this study hold promising applications in advanced vehicle/aerospace lightweighting and crashworthiness safety.

Crashworthiness optimisation and lightweight for front-end safety parts of automobile body using a hybrid optimisation method

This study proposes a hybrid optimisation method integrating contribution analysis, Entropy weight Technique for Ordering Preferences by Similarity to Ideal Solution (E-TOPSIS), design of experiments (DOEs), and grey relational analysis (GRA) for optimisation design of front-end safety parts of automobile bodies to improve the crashworthiness and lightweight of vehicles. First, the finite element model (FEM) of vehicle is established, and the simulation analysis and test of frontal collision for vehicle are performed. The key crashworthiness quotas of vehicle and the mass of safety parts are extracted as the optimisation responses. Second, the material, wall thickness and cross-sectional shape of the safety parts of the automobile body are taken as initial design variables. A variable screening method of contribution analysis combined with E-TOPSIS is proposed. The comprehensive contribution coefficient of numerous initial design variables to the crashworthiness and lightweight of vehicle is calculated using the proposed method, and the design variables are objectively screened by taking this coefficient as an evaluation index. Third, the DOE using Hammersley sampling is performed. Finally, the GRA method is proposed to analyse the experimental design results and obtained the optimal parameter combination of the material, wall thickness, and cross-sectional shape of the safety parts. After optimisation of the front-end safety parts of the automobile body, the crashworthiness safety performance of the vehicle is significantly improved and the mass of the safety parts is reduced by 11.02%. Therefore, the proposed hybrid optimisation method can effectively improve the crashworthiness and lightweight of vehicle.

A systematic approach for multi-objective lightweight and stiffness optimization of a car body

Optimization for the car body under the condition of guaranteeing vehicle overall mechanical performance remains a key automotive engineering design challenge currently. The present study first attempts to group the car body components into safety components (SCs) and non-safety components (NSCs) based on their correlation with crashworthiness safety and then focuses on the potential of NSCs, which compromise a group of thin-walled plate parts that basically have little impact on overall vehicle crashworthiness, for multi-objective lightweight and stiffness optimization. To be more specific, the finite element (FE) models of significant vehicle performance, including the static-dynamic stiffness of the car body and the frontal and side crashworthiness of the vehicle, were first separately established and validated against experimental outcomes. On this basis, SCs closely related to vehicle crashworthiness safety, including frontal safety components (FSCs) and side safety components (SSCs), were figured out through crashworthiness analyses. As a result, the initial NSCs (INSCs) were also determined by filtering out all the SCs from the car body. Subsequently, sensitivity analysis (SA) was employed to screen the INSCs for the final NSCs (FNSCs) for multi-objective lightweight and stiffness optimization, considering minimizing the total mass while maximizing both the static global torsional stiffness and the dynamic first-order torsional frequency of the car body as three optimization objectives. Radial basis function (RBF), multi-objective particle swam optimization (MOPSO) algorithm and modified grey relational analysis (MGRA) were then separately utilized for constructing meta-models, solving optimization process, and identifying the best trade-off design. In addition, different optimization strategies were compared. According to the optimized outcomes, the car body is dramatically lightweight optimized by 7.92 kg; meanwhile, the static-dynamic stiffness of the car body is slightly improved and the overall vehicle crashworthiness is basically guaranteed. Hence, the proposed systematic approach gains insight on reasonable and efficient multi-objective optimization for the car body.

Multi-material design of a vehicle body considering crashworthiness safety and social effects

In the vehicle design, crashworthiness safety has always been a crucial issue; also, social effects are currently attracting much attention for a sustainable-development and friend environment. This study develops and performs a multi-material design for a vehicle body considering both crashworthiness safety and social effects. Numerical vehicle crash models for full-front impact, side impact, off-front impact and roof crush were established and validated according to relevant vehicle test laws. Crashworthiness and social-effect (i.e. weight, cost, manufacture and recycle) objectives with the analytical factors of the vehicle body were defined. Design materials (including both metals and composite materials) were adopted. Uniform design with non-linear normalisation method was utilised for the analysis of the crashworthiness simulation responses. Technique for order preference by similarity to ideal solution (TOPSIS) with the accident-data analysis-based weight ratios was applied for the material design of the vehicle body under multiple objectives. The results show that, when considering both crashworthiness safety and social effects, the composite materials are advantageous for applying to the energy-absorption components; also, different materials have their unique edges in different sections of a vehicle body. This investigation provides a series of useful data for the multi-material design of the vehicle body in engineering.