Crashworthiness Evaluation of a Parallel 5-Tube Circular Multi-Segment Crash Box with Cutting Die Trigger for Railway Safety

A crash box design is developed to enhance the crash box’s abilities to absorb crash energy. Previous research has developed the crash box by adding filler material. Adding the filling material to the crash box will increase energy absorption. Aluminum honeycomb has a combination of lightweight mass and an ability to absorb crash energy. The addition of filler material to the crash box will also reduce the possibility of global bending in the crash box. The method of study is a computer simulation using ANSYS Academic software ver 18.1. This research used circular, square and hexagonal cross-section variations, which reached the same cross-sectional area design. Geometry model for the crash box and honeycomb filler is defined as crash box thickness (tc) 1.6 mm, honeycomb filler thickness (t) 0.5 mm for single layer and 1 mm for double layer and crash box length (l) 120 mm. The materials used were AA6063-T6 for crash boxes and AA3003 for honeycomb fillers. The test model consisted of two types, namely frontal load and oblique load test. The impactor velocity (v) is set to 15 m/s. The impactor and the fixed support are modeled as a rigid body, while the crash box is assumed as an elastic body. Observations were done by using the characteristics of deformation pattern and the absorption amount of produced energy due to the given loading model. Based on the deformation pattern results, it can be found that in the crash box model with square and hexagon honeycomb filler, the occurred deformation pattern was concertina, while the crash box with circular honeycomb filler was the mixed mode in the frontal load test. Regarding the oblique loads, the crash box remains to collapse the global bending on all models. Simulation results with the frontal load test model found that the crash box with circle-shaped honeycomb has the highest energy absorption while the crash box with hexagonal honeycomb filler has the highest Specific Energy Absorption (SEA). In the oblique load test, it was found that the crash box with hexagonal honeycomb filler has the highest energy absorption and SEA. By comparing the hexagonal crash box model with and without honeycomb filler, it is noted that the hexagonal crash box with honeycomb filler has higher Crash Force Efficiency

The crease line formed in an origami-shaped crash box (OSCB) acts as a geometric imperfection and mode inducer. Such geometric imperfections make it possible to protect occupants by lowering the peak force in the event of a collision. The OSCB also shows desirable performance as a crashworthy structure by inducing a collapsing mode with excellent energy absorption. There are many studies on crash boxes with origami patterns applied, but few studies on performance optimisation. This article describes the structural optimisation of an OSCB to maximise the specific energy absorption (SEA) by setting the corner length c and module length l as design variables. Numerical and experimental investigations of the crashworthiness performance were conducted by comparing the optimised OSCB to a circular crash box (CCB), which is known to have the best SEA among straight tubes. The numerical and experimental results were in good agreement, with the optimised OSCB collapsing into the diamond mode. The results of the numerical comparison showed that the SEA and the crush force efficiency (CFE) of the optimised OSCB were increased by 5.94% and 115.58%, respectively. However, in a quasi-static axial crushing experiment, the SEA of the optimised OSCB was 10% lower than that of the CCB, and the CFE was increased by 88.5%. The optimised OSCB in this study displayed an improvement in the SEA compared to the reference OSCB, as well as a reduction in the difference from the CCB, indicating high maintenance performance of the CFE.

Partially Alulight and Hydro Al closed-cell foam-filled commercial 1050H14 Al and 6061T4 Al crash boxes were optimised using the response surface methodology in order to maximise specific energy absorption (SEA). The quasi-static crushing of empty and filled crash boxes was simulated using LS-DYNA, and the results were further confirmed with experimental quasi-static crushing testing of empty and Alulight foam-filled commercial 1050H14 Al crash boxes. Results showed that partial foam filling of commercial crash boxes increased both SEA and mean load because of foam filler axial and lateral deformation in between the progressing folds of the crash box. Within the studied constraint range of box mean load, box wall thickness and foam filler density, the optimised Alulight and Hydro foam-filled 1050H14 and 6061T4 crash boxes resulted in 26%–40% increase in total energy absorption as compared with empty crash boxes. Considering the same weight basis, the use of a higher yield strength box wall material and higher plateau stresses of Al foam filler resulted in higher energy absorptions in partial foam-filled boxes at relatively low displacements.

This work investigates the crash response of conical tubes made from different steel grades ranging from low to high strength steels using finite element (FE) simulations. The FE model was first validated against experimental results before being applied for the numerical analysis using LS DYNA software. Peak crushing load, mean load, energy absorption, crush force efficiency (CFE) and specific energy absorption (SEA) were evaluated from the cones of different steel grades and of various thicknesses. It was found that high strength steel exhibit high SEA and low CFE values. Both SEA and CFE were found to increase with increase in tube wall thickness for the five steel compared. For improved safety of the occupant, steel-CA5 is best because of higher CFE values for 1.5 mm, 2.0 mm and 2.5mm thicknesses. For better weight reduction, steel-DP600 with SEA of 10.6 kJ/kg is the best. Steel-HA3 and steel-SAP H440 with 2.5 mm thickness offer moderate CFE and SEA values. The findings of this study are useful in designing high safety performance vehicle front energy absorption components. Keywords : Conical tube; Crashworthiness; Crush force efficiency; Specific energy absorption

Lattice structures and thin-walled tubes are two types of energy-absorbers widely studied and applied in engineering practice. In this study, a new type of lattice-structure filled thin-walled tube (LFT) was proposed by combining these two energy absorbers and designed via a new explainable data mining method. In this new type of LFT, a BCC-Z (Body- centred cubic unit cell with vertical struts) lattice structure was filled into a square thin-walled tube. Then, the new LFT was parameterized by five design variables, that is, the number of layers in the longitudinal direction (n), number of cells in the transverse direction (m), rod diameter (d), tube thickness (t) and height difference between tube and lattice structures (h). Using Latin hypercubic sampling algorithm, 150 design cases were generated. Numerical models were then developed to simulate their crush behavior, and the simulation dataset was used for data mining. The results showed that (1) Filling the BBC-Z lattice structure into a thin-walled tube can significantly improve the energy absorption (EA) capacity of the structure. (2) SEA (Specific Energy Absorption) of LFT significantly increased by increasing the rod diameter d, number of cells in the transverse direction m and number of layers in longitudinal direction n. (3) The decision trees generated in the data mining process indicated that the rod diameter d of the lattice structure is the key design variable that has most significant impact on EA, followed by m and n. (4) The design rules to build LFTs with high EA efficiency (SEA ≥ 16 kJ/kg and CFE (Crush Force Efficiency)≥45%), high total EA (SEA ≥ 16 kJ/kg and EA ≥ 6 kJ) and lightweight (SEA ≥ 16 kJ/kg and Mass ≤ 0.45 kg) were obtained from decision trees. The ideal configurations of LFT corresponding to these three objectives are: d > 2 mm, n > 2 and m > 3 for high EA efficiency; d > 2 mm, n > 2 and m > 3 for high total EA; and d > 2 mm, n > 2, m ≤ 4 and t ≤ 1.7 mm for lightweight.

In this paper the crashworthiness capabilities of thin-walled corrugated crash boxes in axial crushing relative to flat sidewall boxes from the same material are investigated. In order to achieve this, various design of corrugated aluminium alloy 6060 temper T4 crash boxes were chosen and their axial crushing behaviour under impact loading was studied by developing a theoretical model based on \textit {Super Folding Element} theory and by conducting finite element analysis using LS-DYNA in ANSYS. From the theoretical and FE analysis the crush force efficiency, the specific energy absorption and the frequency and amplitude of fluctuation of the dynamic crush force of the corrugated crash boxes were calculated and the results were compared with the reference uncorrugated model. It was shown that the corrugated crash boxes have advantages of a lower initial collapse force, a lower crush force fluctuation frequency and amplitude relative to a flat sidewall box.

Optimum crashworthiness design of tapered thin-walled tubes with lateral circular cutouts

Braided-textile reinforced thin-walled conical tubular structures: Designing, manufacturing and testing

This study presents a series of novel mirrored multi-cell square tubes (NMST) developed through the application of various evolutionary designs and mirror settings to traditional multi-cell square tubes. Numerical simulations were performed using validated models to assess their crashworthiness under conditions of uniform wall thickness and mass. The findings indicate that the implementation of mirror settings significantly enhances the crashworthiness of the structure, with strategy E demonstrating a particularly marked improvement. Under conditions of equal wall thickness, NMSTE4 exhibited increases in specific energy absorption (SEA) and crush force efficiency (CFE) of 47.15% and 24.15%, respectively, when compared to NMSTE1. Under equal mass conditions, these values increased by 24.84% and 25.53%, respectively. Parametric studies revealed that both an increase in wall thickness and the incorporation of additional mirror settings contribute positively to the energy absorption performance of the structure. The integration of the design characterized by strategy D with those of other strategies further enhances the impact resistance of the original structure, with the AD combination yielding the most substantial improvement. Specifically, compared to NMSTA4, NMSTAD demonstrated increases in energy absorption (EA), SEA, and CFE of 43.85%, 21.91%, and 13.20%, respectively. A comparative analysis was conducted, revealing that compared to non-mirrored design structures, NMSTD4 achieved SEA and CFE improvements of up to 106.38% and 32.43%, respectively.

Lateral crushing behavior of novel carbon fiber/epoxy composite bidirectional self-locked thin-walled tubular structure and system

The use of bio-inspired structures in vehicles is promising. The crashworthiness performance of crash boxes inspired by honeycomb, bamboo, and horsetail structures was compared according to impact simulations. Results were compared regarding specific energy absorption (SEA), peak crushing force (PCF), and specific energy absorption to peak crushing force ratio. Single and multi-objective optimization studies were carried out with a horsetail crash box, which gave the best results. This crash box design can be used in vehicles to improve passive safety.

The study aims to investigate the effect of different infill pattern structures on the energy-absorbing characteristics of single filament wound carbon fiber-reinforced plastic tubes, single polylactic acid and hybrid carbon fiber-reinforced plastic/ polylactic acid tubes under quasi-static axial compression condition, which were fabricated using filament winding and additive manufacturing techniques. Five infill pattern structures of single polylactic acid tubes and hybrid tubes were studied and compared on their energy-absorbing characteristics, which referred to normal, triangle, square, hexagonal and tetrahedral patterns. It concluded that the effect of the infill pattern structure had a significant influence on energy-absorbing characteristics of single polylactic acid and hybrid carbon fiber-reinforced plastic/polylactic acid tubes. For pure polylactic acid tubes, the triangle infill pattern tube represented the highest values of energy absorption ( EA) of 0.75 kJ, specific energy absorption ( SEA) of 28.50 J/g, compressive strength and modulus of 69.72 MPa and 1.40 GPa, yield strength of 27.80 MPa, peak crushing force ( Fpeak) of 23.13 kN and mean crushing force ( Fmean) of 18.82 kN. For the hybrid carbon fiber-reinforced plastic/polylactic acid tube, tetrahedral infill pattern tube showed the highest values of EA with 0.99 kJ, SEA with 29.66 J/g, Fpeak with 22.68 MPa and yield strength with 29.91 MPa. Energy absorption interaction ( EAinteraction) and interaction ratio ( φe) of all specimens were evaluated, which showed that the tetrahedral infill pattern tube recorded the highest of all hybrid tubes with 259.92 J and 35.72 %. The result revealed that the tetrahedral pattern displayed better crashworthiness in terms of crushing force efficiency ( CFE), EA and SEA in the hybrid structure, which had greater potential to apply as energy absorbers. Moreover, triangle and square infill patterns of hybrid tubes provided the negative interaction effect results, which conducted lower energy-absorbing characteristics compared to individual tubes, respectively.

Axial crushing behaviors of buckling induced triangular tubular structures

Crashworthiness of a material is a measure of its ability to absorb energy during a crash. A well-designed crash box is instrumental in protecting the costly vehicle components. A square, hollow, hybrid beam of aluminum/CFRP was subjected to dynamic axial load to analyze the effect of five different lay-up sequences on its crashworthiness. The beam was placed between two plates. Boundary conditions were imposed on them to simulate a frontal body crash test model. Modeling and dynamic analysis of composite structures was done on ABAQUS. Different orientation of carbon fibers varies the crashworthiness of the hybrid beam. Addition of CFRP layer showed clear improvement in specific energy absorption and crush force efficiency compared to pure aluminum beam. Two layers of CFRP oriented at 90° on Aluminum showed 52% increase in CFE.

This 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.