Crash Box Research Articles

Stochastic analysis of a crash box under impact loading by an adaptive POD-PCE model

Stochastic analysis of a crash box under impact loading by an adaptive POD-PCE model

A review of performance improvement approaches on crash boxes

Kaza anında araçların hızları ve kütleleri sebebiyle yüksek miktarda enerji açığa çıkmakta ve bu enerjinin uygun şekilde sönümlenmesi gerekmektedir. Düzgün sönümlenemeyen enerji iç parçalara, sürücüye ve yolculara zarar verecek kuvvetlerin oluşmasına sebep olarak hayati sorunlara yol açar. Araçlarda bu sönümlemeyi yapabilmek için devletlerin, kurumların ve sigorta şirketlerinin öne sürdüğü kriterleri karşılayabilecek özel tasarlanmış çarpışma kutusu adındaki parçalara ihtiyaç duyulmaktadır. Sürdürülebilirlik, çevre, yakıt tasarrufu gibi kavramlarla beraber araçlarda hafifliğin ön plana çıkması ve artan rekabet, kaza dışında âtıl duran çarpışma kutuları üzerinde önemli çalışmalara yol açmıştır. Bu nedenlerle, çarpışma kutularının kinetik enerjiyi emme performansı, üretilebilirliği, maliyeti, hafifliği göz önünde bulundurularak uygun seçimler yapılmalıdır. Bu çalışma, çarpışma kutusunun performansını artırıcı temel faktörleri ele alan kapsamlı bir literatür araştırmasını içermektedir. Çalışmada, çarpışma kutularının enerji sönümleme yeteneği; geometri, malzeme ve dolgu gibi üç temel başlık altında ele alınmıştır. Bu kapsamda, literatürdeki çalışmalar incelenerek çarpışma kutuları ile gerçekleştirilen enerji emilimi konusundaki önemli noktalar derlenmiştir.

Development of efficient energy absorption components for crashworthiness applications: An experimental study

AbstractThis work experimentally investigates the quasi‐static crush response and energy absorption of glass‐reinforced epoxy thin‐walled crash box filled with nano‐aluminum oxide (Al2O3). The effect of the triggering (45 edge chamfering) and the weight percentage (wt%) of Al2O3 on the crushing performance have been studied. Field emission scanning electron microscope (FE‐SEM) and energy‐dispersive X‐ray spectroscopy (EDX) were adapted to show the elemental composition of the fabricated samples' surfaces. To follow the fracture mechanism, visual inspection, and scanning electron microscope (SEM) were performed. Two‐parameter Weibull distribution function was employed to statistically analyze the experimental results. Failure probability curves were established to help the designers in selecting the suitable material for energy‐absorbing applications. Results indicated that for untriggered glass/epoxy composite crash boxes, the inclusion of 1, 2, and 3 wt% of nano‐Al2O3 leads to an increase of, respectively, 16.34%, 48.46%, and 68.70% in the absorbed energy (U). While there is a decrease of 32.72% in (U) when adding 4 wt% of nano‐Al2O3. An enrichment of 9.00%, 18.04%, 31.53%, and 11.30% in crush force efficiency (CFE) was reached by the inclusion of, respectively, 1, 2, 3, and 4 wt% of nano‐Al2O3. Triggering has a considerable effect on the crashworthiness parameters of the fabricated composite crash boxes. A decrease of 6.56%, 10.11%, 4.01%, 4.76%, and 11.62% in the initial peak load (), an enrichment of 34.10%, 26.06%, 26.77%, 18.08%, and 28.97% in (CFE) and an improvement of 36.43%, 31.32%, 29.27%, 12.99%, and 52.47% in (U) were reported for composite crash boxes filled with 0, 1, 2, 3, and 4 wt% of nano‐Al2O3. It is obvious that glass/epoxy triggered composite crash boxes filled with 3 wt% of nano‐Al2O3 are appropriate to be used as energy absorbing device employed in vehicles due to their enhanced energy absorbing capabilities.

Effect of heat-treatment on crash performance in bumper beam and crash box design and optimization of the system

Abstract Within the study’s scope, impact analyses of homogeneous bumper beam-crash box systems designed from AA6063-O, AA6063-T5, and AA6063-T6 materials and hybrid systems designed from combinations of these materials were made and compared in terms of energy absorption values. In designs where failure does not occur, the highest energy absorption value was obtained using the AA6063-T5 bumper beam and AA6063-O crash box system, and single and multi-objective optimization studies were conducted using this design. The optimal bumper system improved the crash performance of the structure. Accordingly, this bumper system can be used in vehicles to improve crashworthiness.

An investigation of the crashworthiness performance and optimization of tetra-chiral and reentrant crash boxes

In this study, the crash performances of square and cylindrical crash boxes with tetra-chiral and reentrant unit cell structures were explored and optimized. First, tensile tests were conducted to determine the mechanical properties of the Al 6061-T6. These mechanical properties were then incorporated in the finite element (FE) models generated using LS-DYNA. To validate the FE models, tetra-chiral and reentrant crash plates were produced, and the FE analysis results were compared with the test results. Subsequent to this validation, for each crash box design type (i.e., tetra-chiral cylindrical, tetra-chiral square, reentrant cylindrical, and reentrant square), Kriging surrogate models were constructed using MATLAB for two crash metrics: specific energy absorption (SEA) and crash load efficiency (CLE). Finally, a multi-objective optimization problem was formulated for each crash box design type, the generated Kriging models are integrated into genetic algorithm available in MATLAB, and the Pareto optimal crash box designs were obtained. It was found that the SEA and CLE of reentrant crash boxes were better than those of the tetra-chiral crash boxes. In addition, the reentrant cylindrical crash box displayed better performance than the reentrant square, as well as the tetra-chiral cylindrical and square crash boxes.

Robust design assessment of automotive crash box structures through model order reduction

The research work is focused on a comprehensive study of crashworthiness parameters associated with widely used crash box components of passenger cars. The finite-element models representing the automotive crash box structure were procured from full-car digital models issued by NHTSA. From the full car model, the crash box geometry is extracted for the crash analysis and further design optimizations. The crashworthiness parameters such as energy absorption, crush force efficiency, specific energy absorption is studied in detail with analytical and finite-element solutions for each variant and are further enhanced using multi-objective design optimization through RSM-based DOE methods. For guiding engineers in real- time design exploration and other parametric assessments, a reduced-order model for each of the variants was developed by using the sPGD (sparse Proper Generalised Decomposition) method. The developed reduced order models of the crash boxes were able to accurately capture the non-linearities associated with them and delivered accuracy of 90%. On undergoing robust design assessment with crash box designs, taking into account of all variants, an average of 34.33% in energy absorption capacity was achieved. The heavier crash box variants which had good SEA capacity are performed for successful mass reduction of 18.91% without affecting their crash performance. For the explicit crash simulations, the virtual performance solution finite-element solver from the ESI group is utilized.

Mechanism of reproducible axial impact of square crash boxes

Axial crushing of square crash boxes (CBs) is a complex phenomenon in which the unrepeatability of the tests is quite common. Conducting an acceptable experiment that can be used for validating a finite element (FE) setup is normally based on the researcher’s experience. The researchers deal with a large number of irreproducible test results. Likewise, the FE simulations face the same issue, owing to the high sensitivity of the stability simulations, which can crucially mislead the FE outcomes. These uncertainties decrease the reliability of the results of the studies. The present study focus on this issue. It examines the compression behavior of the CBs and the effect of the imperfections and explains the resources of this irreproducibility. Furthermore, it analyzes the production of the different folding patterns and shows that buckling coupling of the square CB and its side plates results in different folding patterns.

Formability of roll-formed carbon fibre reinforced metal hybrid components and its experimental validation

Carbon Fibre Reinforced Metal Hybrid (CFRMH) materials that combine a sheet metal substrate with a reinforcing carbon fibre patch represent a promising solution to reduce weight while increasing the structural and crash performance of future automotive vehicles. CFRMHs cannot be formed with conventional stamping processes and at high volumes. This currently reduces their widespread application. Roll forming is increasingly used in the automobile industry for the forming of lightweight and high-strength metal structural components. The major deformation mode in roll forming is simple bending and this reduces interlaminar shear and compressive stresses that lead to fibre failure and delamination issues when stamping CFRMH sheet materials. This work analyses the potential of applying the conventional roll forming process for the manufacture of a simple top hat section shape from CFRMH sheet. For this, first, the material is produced in a hot press and then formed to shape in a laboratory roll forming facility at room temperature. Different layup sequences are tested, and component quality is analysed after roll forming by visual inspection. The results suggest that roll forming presents a promising manufacturing method for the production of automotive components from CFRMH sheets. The roll formed open shells are joined to produce crash box structure and tested in 3-point bending. The results show that depending on the fibre orientation a significant increase in weight specific strength is achieved.

Accurate numerical prediction of thermo-mechanical behaviour and phase fractions in SLM components of advanced high strength steels for automotive applications

Conventional crash absorber in automotive applications, so called crash boxes are fabricated via deep drawn sheet metal resulting in significant lead times and costs. Laser Powder Bed Fusion processes, like Selective Laser Melting (SLM) offer an attractive alternative for the fabrication of crash parts while eliminating any need for costly forming dies and reducing the lead times, provided required material properties are achieved. Reliable numerical simulation model to predict the SLM build process with greater spatial resolution and accuracy is indispensable to understand the process further in order to ensure its applicability to crash structures. In this paper, an improved simulation methodology for SLM process is presented to predict the material behaviour via temperature, deformation, hardening, flow stress and phase fractions throughout the component with increased accuracy and greater resolution. To achieve desired spatial resolution, the equivalent layers are subdivided into individual tracks, which are then deposited sequentially to simulate the printing process. The material is a medium manganese (7­-8 %) transformation induced plasticity (TRIP) steel with austenite and martensite primary phases. The multiple solid-state phase transformation cycles undergone by the material are modelled in the simulation and the final phases are predicted. The results indicate improved accuracy and higher resolution in predictions for temperature, phase fractions and deformation.

Exploration-oriented sampling strategies for global surrogate modeling: A comparison between one-stage and adaptive methods

Studying complex phenomena in detail by performing real experiments is often an unfeasible task. Virtual experiments using simulations are usually used to support the development process. However, numerical simulations are limited by their computational cost. Metamodeling techniques are commonly used to mimic the behavior of unknown solver functions, especially for expensive black box optimizations. If a good correlation between the surrogate model and the black box function is obtained, expensive numerical simulations can be significantly reduced. The sampling strategy, which selects a subset of samples that can adequately predict the behavior of expensive black box functions, plays an important role in the fidelity of the surrogate model. Achieving the desired metamodel accuracy with as few solver calls as possible is the main goal of global surrogate modeling. In this paper, exploration-oriented adaptive sampling strategies are compared with commonly used one-stage sampling approaches, such as Latin Hypercube Design (LHD). The difference in the quality of approximation is tested on benchmark functions from 2 up to 30 variables. Two novel sampling algorithms to get fine-grained quasi-LHDs will be proposed and an improvement to a well-known, pre-existing sequential input algorithm will be discussed. Finally, these methods are applied to a crash box design to investigate the performance when approximating highly non-linear crashworthiness problems. It is found that adaptive sampling approaches outperform one-stage methods both in terms of mathematical properties and in terms of metamodel accuracy in the majority of the tests. A proper stopping algorithm should also be employed with adaptive methods to avoid oversampling.

Multi-objective optimization of hexahedral pyramid crash box using MOEA/D-DAE algorithm

Crash box is an important energy-absorbing part of the automobile body, so this paper aims to explore a novel hexahedral pyramid (H-P) crash box with excellent overall performance, which is composed of H-P negative Poisson’s ratio (auxetic) inner core structure and outer shell layer. On this basis, a many-objective optimization design for the novel crash box is conducted to enhance its performance by integrating the response surface model (RSM) method and the multi-objective evolutionary algorithm based on decomposition with detecting and escaping strategy (MOEA/D-DAE). The results demonstrate that, compared with the hollow crash box, the hexagonal honeycomb crash box and the re-entrant hexagon crash box, the initial H-P crash box has better energy absorption characteristics and comprehensive crashworthiness. Moreover, the optimized novel H-P crash box with the MOEA/D-DAE can improve its crashworthiness, energy absorption capability and lightweight more effectively, and make the collision process more controllable and stable.

Optimal design of a novel crash box with functional gradient negative Poisson’s ratio structure

Crashworthiness and anti-vibration performance play critical roles in the performance of passenger cars. Aiming at enhancing the crash resistance and vibration resistance of vehicles thus providing good protection for passengers and drivers, a novel crash box with three-dimensional double arrow type negative Poisson’s ratio structure with functional gradient filling inner core (FGNPR crash box) is introduced in this paper and its performance is studied in detail through the comparison with the conventional crash box and the crash box filled with the uniform gradient negative Poisson’s ratio structure (NPR crash box) in crashworthiness and vibration resistance. Furthermore, range analysis is used to screen out the design variables that have little influence on the evaluation indexes and eliminate them. Based on these, neighborhood cultivation genetic algorithm (NCGA) and non-dominated sorting genetic algorithm-ii (NSGA-II) are selected as the optimization algorithms to carry out optimization design respectively and a comparison is made between the two suboptimal results screened out based on the normal boundary intersection (NBI) method to determine the overall optimal solution. Results show that the optimized FGNPR crash box has better crashworthiness and vibration resistance over the other crash boxes and its performance is further verified based on the peak acceleration of B-pillar in full vehicle crash condition. This paper provides some theoretical reference support for the development and exploration of automobile crash box systems.

Large Torsion Deformation: Centrosymmetric Reentrant Honeycomb

There exist some problems in the crash box and anti-collision beam sandwich structure, such as monotone deformation pattern and uneconomical energy absorption performance. In order to raise the deformation capacity and energy absorption performance of sandwich structure, centrosymmetric reentrant honeycomb (CRH) and hexagonal centrosymmetric reentrant honeycomb (HCRH) are proposed based on auxetic reentrant honeycomb (ARH) in this work. Based on HCRH, four kinds of transverse combination structures and two kinds of longitudinal combination structures are obtained. The results of specific energy absorption show that the energy absorption capacity of the angular contact homodromous combination structure (ACOC) is about 3 times that of the other three transverse combination structures. Compared with longitudinal heterodromous combination structure (LHEC), the energy absorption capacity of longitudinal homodromous combination structure (LHOC) is improved by 72.7%.

Numerical simulation of crashworthiness parameters for design optimization of an automotive crash-box

Automotive manufacturers rely on rigorous testing and simulations to construct their vehicles durable and safe in all aspects. One such vital factor is crash safety, otherwise known as crashworthiness. Crash tests are conventional forms of non-destructive methods to validate the vehicle for its crashworthiness and compatibility based on different operating conditions. The frontal impact test is the most primary form of crash test, which focuses on improving passenger's safety and comfort. According to NHTSA, a vehicle is rated based on these safety criteria, for which automobile manufacturers conduct a plethora of crash-related studies. Numerical simulation aids them in cutting down testing time and overall cost endured by providing a reliable amount of insights into the process. The current study is aimed at improving the crashworthiness of a crash box in a lightweight passenger car, such that it becomes more energy absorbent in terms of frontal impacts. All necessary parameters such as energy absorption, mean crush force, specific energy absorption, crush force efficiencies are evaluated based on analytical and finite element methods. There was a decent agreement between the analytical and simulation results, with an accuracy of 97%. The crashworthiness of the crash box was improved with the help of DOE-based response surface methodology (RSM). The RSM approach helped in improving the design of the crash box with enhanced EA & CFE by 30% and 8.8% respectively. The investigation of design variables on the energy absorption capacity of the thin-walled structure was also done. For the axial impact simulations, finite element solver Virtual Performance Solution − Pam Crash from the ESI group is used.

FEA and Quasi-static Test on Energy Absorption Characteristic of Space Orthogonal Concave Honeycomb Structure with Negative Poisson’s Ratio

As a representative of metamaterials, negative Poisson’s ratio (NPR) material possesses special mechanical properties such as expansion, negative compression ratio and so forth. As a result, it is widely used in the fields of vehicles, aerospace, et al. In this paper, a novel space orthogonal concave honeycomb structure (OC) is designed based on traditional concave honeycomb structure (CHS). In order to explore the influence rule of OC structure on the deformation and energy absorption capacity of crash box under low-speed collision, mechanical analysis and parameter research on OC structure are conducted through quasi-static compression test and numerical simulation. The results suggest that the finite element results of OC structure fit well with the experimental results, and the FEM is highly credible. In addition, the novel OC sandwich structure can effectively enhance the deformation capacity and improve the energy absorption performance of the crash box. When the wall thickness ? of OC structure is 1mm and angle ? is 50°, the deformation and energy absorption capacity of the crash box increased by 25.6% and 19.3% respectively.

クラッシュボックスの最大反力予測モデルの構築

The structural strength evaluation of crash boxes is predicted by machine learning in this study. The training data was obtained from the dynamic elastic plastic analysis of the crash box. The input physical quantities are barrier angle, box thickness, material properties and mass equivalent to vehicle weight. The output physical quantity is the reaction force. Buckling occurs in the analysis and different directions of corruptions are one of the most interesting phenomenon from a point of engineering view. Physically meaningful features that take into account physical laws, physical properties, shape, and so on were added. As a result, we showed that learning by CNN is possible with higher accuracy. In addition, data design and data augmentation that takes physical phenomena into account are necessary to deal with large outlier. We would like to propose an adaptive method for machine learning in structural evaluation that can be used for a wide range of structural evaluations.

Interval methods for lack-of-knowledge uncertainty in crash analysis

This paper deals with lack-of-knowledge uncertainty in complex non-linear simulations on a component level, i.e., a crashbox during frontal impact of a vehicle. Specifically, the focus lies on using interval field techniques to model the uncertain boundary conditions during impact simulations. The uncertainty considered in this work is the unknown mechanical response from the adjacent structure. This uncertainty is considered to be epistemic, representing the case where this adjacent structure is unknown at the time the impact analysis is performed. In practice, this refers to the situation where the adjacent structure is still under development, e.g., at a different department or even outsourced. In addition, the safety critical performance of both, the component and the overall structure should be guaranteed under a wide range of circumstances, which are typically encountered in real-life situations. Typically, car manufacturers use multidisciplinary optimisation to identify component designs that perform best on all requirements in a deterministic sense, while minimising the overall weight. Unfortunately, the results of such optimisation schemes are known to converge to an often non-robust optimum. As a result, the response of the structure may be sensitive to small changes in input parameters or boundary conditions.As an answer to these challenges, this paper proposes an interval field approach that accounts for the epistemic, i.e., lack-of-knowledge, uncertainty of the adjacent structures, even in an early design stage. This is accomplished by introducing a spatially varying uncertain mechanical compliance in elements that connect the component to the adjacent structures. These elements have an interval valued stiffness, which is varied along the component following the realisations of an interval field. The bounds on the interval-valued response quantities of interest, i.e., mean force and peak force, are identified using a differential evolution algorithm. This method is demonstrated on four case studies of a full overlap crash analysis of a rectangular crash box, which represents a generic component within the front structure of a vehicle. These case studies demonstrate the applicability and the potential of the proposed method. In addition, in the last case it is shown that the performance of the component can be assessed under an increasing range of uncertainty.

Deformation Mode and Energy Absorption Analysis of Bi-Tubular Corrugated Crash Box Structure

In this research, the characteristic of crash box with bi-tubular corrugated structure are numerically examined under axial loading condition. The crash box characteristic were observed in the compression test of aluminum alloy (AA6061) using ANSYS software. The comparation were carried out on two geometrical types, namely: ordinary corrugated tube (OCT) and bi-tubular corrugated tube (BCT). The result showed that comparing both of crash box structure exhibit the Simultaneous crush mode (S-mode) deformation. The force-displacement present a stable diagram without any fluctuation. BCT structure resulted 71% energy absorption capacity increment compared to OCT structure. The highest energy absorbed by BCT structure was 10.8 kJ. There are no significant specific energy absorption different between the specimen and the highest SEA occurat OCT structure with 31.281 kJ kg-1.

Crash Analysis and Size Optimization of a Vehicle’s Front Bumper System

Bumper beams and crash boxes are structural vehicle elements that have very critical functions during frontal collisions. This study examined the energy ab-sorbed by the front bumper system and the reaction forces to the cage structure representing the vehicle cabin frame during a full frontal crash against a rigid wall. For this purpose, 25 different crash analyses were conducted using the ANSYS software by changing the sheet thickness values of the bumper beam (t1) and crash boxes-frontal crash rails (t2) that make up the front bumper system. The internal energy (absorbed energy) of the front bumper elements from the analysis results and the reaction forces acting on the representative cage struc-ture in the opposite direction to the movement were examined. When the ob-tained data were interpreted according to variable thickness, it was observed that the variable t2 significantly affected both the absorbed energy and reaction force results, while the variable t1 did not have a significant effect on the results. Based on this, the thickness value t2 was determined as the design variable of the size optimization problem. When the optimization problem established with the reac-tion force and absorbed energy constraint functions was solved, the optimal t2 thickness value with the highest absorbed energy / peak reaction force ratio was found.

The effect of modal properties of crash box structures with trigger mechanisms towards the crashworthiness by using finite element analysis

In the automotive structure, there are different components that utilise aluminium alloy (AA) sheets and it is used widely in the car body-in-white which comprise bumpers and the crash box structure at the front end of the car which specifically designed to withstand the event of collision. As the structures are also experiencing dynamic loading, it were also a concern for the structures to show satisfied modal properties. In this study, the modal properties of the crash box structures are investigated along with the effect of the modal properties towards the crashworthiness behaviour of the structure itself with the approach of finite element analysis. Experimental modal analysis was also done to further validating the finite element analysis of the modal properties. Three different designs of trigger mechanisms are applied towards the crash box structure to observe on both findings. For the connector element, equivalent nodes of both parts of the crash box structures are used. For the results, the correlation from both findings did show that the presence of trigger mechanism did decreased the magnitude of natural frequencies as well as the mode shape as shown by crash box type 3 by 9.50% and for the crashworthiness output, the crashworthiness behaviour of the crash box with trigger mechanisms were better in term of the collisions phases indicated by the primary peak force and the secondary peak force from the force-displacement curve as also shown by crash box structure type 3 with the percentage of 22.59%. The study does shows that the stiffness and mass distribution due to the presence of trigger mechanism do affect the modal properties of a structure as well as its crashworthiness output.