Energy Absorbing Structures Research Articles

Crushing behaviours and energy absorption characteristics of square antiprisms structure against flatwise crushing

In this study, a type of thin-walled energy absorber named square antiprisms (SAP) is proposed, which can be used as a core of cladding “sandwich” panel design for improving crashworthiness. Three types of SAP structure, i.e. open SAP, half-enclosed SAP and all-enclosed SAP are studied. The purpose of this unique geometric structure is to increase the energy absorption capacity of the thin-walled structure while maintaining a uniform collapsing resistance under various crush loading rates as compared with other existing conventional thin-walled structures (i.e. cylindrical tube, square tube), and folded square dome shaped structure proposed recently [50]. A unit cell of standard Miura-origami folding core is numerically simulated and calibrated with the experimental results. Good agreement on the peak and average crushing force between numerical results and experimental data is achieved. The calibrated numerical model is then used to simulate the structural response of thin-walled energy-absorbing structures under various loading rates. The collapse modes and the energy absorption capacity including average and peak stress, energy absorption, crush force efficiency and densification strain are compared among these structures. The proposed open SAP structure shows good energy absorption characteristics under quasi-static loading and dynamic loading by yielding low initial peak stress, big crush force efficiency, large densification strain and more uniform collapsing. In addition, unlike the existing typical axial crashed thin-walled energy absorber, the SAP structure show shows insensitivity to the medium and low crushing speed (no more than 63 km/s) in terms of initial peak stress and uniformity ratio. Compared with the existing typical thin-walled structures, the proposed SAP structure demonstrates a superior performance to most of the axially loaded thin-walled components, indicating a potential application as an energy absorber.

Lessons from nature: 3D printed bio-inspired porous structures for impact energy absorption – A review

As a result of their mechanical characteristics, biological structures often provide inspiration for the development of high-performance mechanical structures. Nevertheless, traditional production processes are often incapable of precisely reproducing the intricate and exquisite nature of biological systems. Modern additive manufacturing techniques provide a pathway to the creation of materials with complex patterns that are inspired by biological processes. In this paper, we identify the different types of biomimetic porous structures seen in nature, many of which are composite structures, and categorise them. We also identify the natural species with porous structures and illustrate their functions. In addition, this review paper presents how these porous structures have been mimicked for engineering applications. Figures are shown to demonstrate the scale (meso, micro, and nano) at which the porous structures are emulated. As biological porous structures have been successfully mimicked into synthetic materials using additive manufacturing (AM), we classify the types of 3D printing with respect to impact loading applications and describe the various types of additive manufacturing processes used to manufacture biomimetic porous structures. This review paper will be of interest to academics looking to design innovative lightweight porous composite structures and use emerging technologies to investigate their energy absorption properties, which have a wide range of engineering applications.

Conversion of low density polyethylene foams into auxetic metamaterials

AbstractCellular polymers, such as polyethylene foams, are commonly used in the packaging industry. These materials have short service life and generate a high volume of waste after use. In order to valorize this waste and produce added‐value applications, it is proposed to convert these materials into highly efficient energy absorption structures. This was done by modifying the original cellular morphology of the foams (spheroidal or polygonal) into a re‐entrant structure to produce auxetic materials. This work presents an optimized process combining mechanical compression and solvent vapor evaporation‐condensation leading to low density foams (77–200 kg/m3) having negative Poisson's ratios (NPR). Three series of recycled low density polyethylene (LDPE) foams with an initial density of 16, 21, and 36 kg/m3 were used to optimize the processing conditions in terms of treatment temperature, time, and pressure. From all the samples prepared, a minimum Poisson's ratio of −3.5 was obtained. To further characterize the samples, the final foam structure was analyzed to relate with mechanical properties and compare with conventional foams having positive Poisson's ratios. The results are discussed using tensile properties and energy dissipation which were shown to be highly improved for auxetic foams. Overall, the resulting foams can be used in several applications such as sport and military protection equipment.

Topometry Optimization of Energy Absorbing Structure through Targeting Force-Displacement Method considering Tailor Rolled Blank Process

Inspired by topometry optimization, this work proposed a new design approach that mixed of targeting force-displacement (TFD) method and tailor rolled blank (TRB) process for thin-walled energy absorption structures, which has vast applied prospects in the aerospace and automotive industries. This method not only overcomes manufacturing difficulty caused by the TFD method based on topometry optimization but also provides a new idea for TRB energy absorption structure. The optimized results can be transferred to the computer aided design environment without additional postprocessing. Firstly, a uniform thickness constraint is introduced to make the designed structure have constant thickness distribution along desired direction; topometry optimization is carried out to use TFD method. Secondly, a method that can automatically divide the design domain is developed. The adjacent elements with smaller thickness differences are merged to form TRB subdomains based on the optimization results of forestep, and the TFD method is used again. Finally, TRB finite element modeling codes is developed. According to the second step, modeling of the transition zone is added to finally form the TRB structure that meets the requirements of manufacturing. This method is used to optimize the crashworthiness of the thin-walled tube under axial and oblique loading. Numerical results demonstrate the effectiveness of this method. Therefore, this method can be used to design high-efficiency energy absorber on aircraft or automobile, such as the strut of aircraft and energy absorption box of automobile.

Crashworthiness of lantern-like lattice structures with a bidirectional gradient distribution

Oblique impact loading conditions strongly influence the crashworthiness of energy-absorbing structures. In the present work, inspired by the distribution characteristics of spider webs, a bidirectional gradient configuration of cell wall thickness was introduced to enhance the crashworthiness of lattice structures based on the functional similarity of longitudinal gradient distribution and lateral gradient distribution. A comparative study of different gradient configurations was carried out using the finite element (FE) simulations. It was found that the longitudinal gradient distribution was beneficial to improve the comprehensive energy absorption capacity of the lattice structure, especially under small-angle impact conditions. With the increase of impact angle, the effect of the lateral gradient distribution on the stability of energy absorption became more prominent. In comparison to the uniform structure and the single gradient structure, the lattice structure with the positive longitudinal gradient and the negative lateral gradient distribution exhibited great potential in enhancing the energy absorption capacity and reducing the peak crushing force. A detailed parametric study was executed to explore the effects of the gradient layer number and the gradient thickness increment of the bidirectional gradient distribution on the comprehensive energy absorption capacity and energy absorption stability of the structure under multi-angle impact conditions. The findings of this research provide valuable guidelines to design bio-inspired lattice structures subjected to complex loading conditions.

Research on Optimization Design of Key Energy-Absorbing Structure of a Helicopter Seat Based on Human–Seat Coupling System

During the process of emergency landing, the energy of the impact in the vertical direction is dissipated through the deformation of the structure. The landing load is transferred to the spine of the occupant through the landing gear, the fuselage and finally the seat. This can cause serious damage to the human body. Since the seat is in direct contact with the human body, the energy absorption capacity of the seat is the most direct manifestation of the Crashworthiness of the helicopter. The solutions proposed in the paper may reduce the impact of the seat on the spine of the occupant during the collision by optimizing the key energy-absorbing structure. Taking the seat of the H135 helicopter as a case, the mechanical model of the human–seat coupling system, which is based on the theories of energy methods and structural mechanics, is simplified. Additionally, the simulation was considered reasonable by comparing the simulation results with the results of crashworthiness tests. On the basis of the above, the optimization of the key energy-absorbing structure of the seat was completed by using Latin hypercube sampling and the kriging model. Overall, the optimization effectively enhanced the crashworthiness of this helicopter seat and provided a solution for the passive safety design of aviation seats.

Optimization of Anti-Impact Energy Absorption Structure of Hydraulic Support

Rock bursts are a frequent occurrence in deep coal mining, and reducing the risk of rock bursts is necessary for the safe and efficient mining of coal. As honeycomb structures have good impact resistance, the design suggests that a honeycomb structure is adopted in the roof. A mechanical model of the hydraulic support is established, and the influence of geometric parameters on the impact resistance of the honeycomb structure is studied. Finally, the orthogonal test method was used to analyze the influence and weight of the geometric parameters on the anti-impact performance of the honeycomb structure with hydraulic leg stress and roof displacement as the evaluation indexes. This paper provides a new design idea for the research and development of an impact resistance hydraulic support in the underground coal mine, which is significant in ensuring coal mine safety.

Correlation Study between the Mechanical Property of the Square Cone Energy-Absorbing Structure and Collision Energy Distribution for Urban Rail Trains

In order to study the influence of the square cone energy-absorbing structure of urban rail trains on the collision energy distribution of trains during the collision process, an eight-marshalling train crash dynamics model was established, and the force–displacement energy-absorbing characteristic curve of the anti-climbing structure was obtained through a full-scale impact experiment. According to the characteristics of the curve, the influence of the initial peak force, the platform force and the slope of the platform force of the anti-climbing energy-absorbing device on the energy absorption of the train collision under a 25 km/h condition was studied. Based on this, the multi-objective genetic algorithm was used to optimize the overall energy distribution scheme of the train. The results showed that the changes in the initial peak force, the platform force and the slope of the platform force will lead to changes in the energy absorption of the four-section moving train and the four-section stationary train that are closer to the collision interface, and the other is almost unchanged. Through the optimized design, the energy absorption of the head car impact interface is increased by 0.74%, the energy absorption of the first impact interface of the middle cars is reduced by 3.36% and the third impact interface of the middle cars is increased by 9.17%. The distribution of the collision energy of the train is more reasonable. At the same time, the deformation of the middle car body is reduced, and the utilization efficiency of the overall energy-absorbing structure of the train is improved.

Study on energy absorption characteristics of expansion tube with light magnesium alloy

This paper proposed a lightweight magnesium alloy expansion energy-absorbing structure. The structure adopts lightweight materials, which can greatly reduce its own weight on the basis of ensuring energy absorption performance. Firstly, the geometric model of structure is designed and the corresponding physical prototype is processed. The theoretical model of magnesium alloy expansion tube is studied, and the main mechanical response is analyzed. Then the structural mechanical properties are studied by quasi-static compression test. Combined with the theoretical model, several typical deformation stages in expanding are analyzed. The effects of geometric parameters on the energy absorption performance are studied. The results show that with the increase of die angle, die expansion size and tube thickness, the maximum peak force, average force, energy absorption and specific energy absorption increase. Then the test results are compared with the corresponding theoretical steady force to verify the applicability of the theoretical model. The theoretical values are basically in good agreement with the experimental values. The error of all results is within 10%. Finally, comparing the characteristics of magnesium alloy, aluminum alloy and steel energy absorbing tube with the same quality, it is concluded that the specific energy absorption of magnesium alloy structure is 31.6% and 4.1% higher than that of steel and aluminum respectively, and magnesium alloy tube has higher specific energy absorption.

Efficient crash structure design for road traffic accidents of tomorrow

Energy absorbing structures (EAS) play a vital role in automotive crash mitigation systems and save countless lives each year. Innovative EAS design ideas such as cross-sectional geometry is an area under intense research as evidenced by a large number of publications in recent years. It is however very difficult to directly compare the efficiency of the design suggestions due to parameter variation. This paper identifies designs with the highest potential, introduces an efficient reduced order modelling methodology and provides the first comprehensive unbiased benchmark. Critical evaluation of results reveal that some designs have inherent issues not previously reported, whilst others demonstrate significant potential for improving EAS performance compared to “conventional” designs.

Sandwich structure with negative Poisson’s ratio of periodic rectangular tube: Mechanical properties and energy absorption

Due to its unique deformation form, Negative Poisson’s ratio sandwich structure has excellent energy absorption, but the low load capacity limits its engineering applications. In this paper, we design a new negative Poisson’s ratio rectangular tube periodic sandwich structure. There are many beams in this structure which appear plastic hinges when compressed. After further compression, the rectangular tube wall buckles and the core shrinks inward, which realizes that the structure exhibits high-performance energy absorption ability and excellent mechanical properties. Three-dimensional finite element model of sandwich structure with negative Poisson’s ratio of periodic rectangular tube quasi-static compression test and low-velocity impact were investigated by the use of ABAQUS/Explicit software. The accuracy of the simulation method was verified by the comparison of test and simulation results. Based on the validated numerical models were further investigated to comprehensively understand the influence of rectangular tube unit cell wall thickness ( t) and cell height ( h) on the load capacity and energy absorption capacity of the specimen. The energy absorption capacity and mechanical properties of the proposed negative Poisson’s ratio sandwich structure could be enhanced by optimizing the design of rectangular tube unit cell wall thickness ( t) and rectangular tube unit cell height ( h). The present findings offer insights into the application of negative Poisson’s ratio sandwich structure impact energy-absorbing structures in aerospace, automotive and other fields.

A hybrid MCDM-based optimization method for cutting-type energy-absorbing structures of subway vehicles

A hybrid MCDM-based optimization method for cutting-type energy-absorbing structures of subway vehicles

Multiobjective and multicollision scenario reliability-based design optimization of honeycomb-filled composite energy-absorbing structures for subways

Multiobjective and multicollision scenario reliability-based design optimization of honeycomb-filled composite energy-absorbing structures for subways

Mechanical properties of a novel two-phase hybrid plate-lattice metamaterial

Lattices were lightweight load-bearing and energy absorption structures, while the traditional designs with a periodic arrangement of single-type cells restricted the design domains. In this work, novel two-phase hybrid strategies based on different types and numbers of thin-plate cubic cells were proposed, and quasi-static compression experiments and finite element numerical simulations were performed to investigate their energy absorption characteristics and deformation mechanisms. The effects of the relative density and load direction on the compression responses were also explored. The results showed that SC-BCC lattices exhibited higher specific energy absorption than conventional lattices and other practical metamaterials, and changing the number and arrangement of cells of the hybrid structures achieved better mechanical properties in a specific loading direction. The specific energy absorption capacity of the hybrid plate-lattice can be up to 4.30 J/g in the present work, which is higher than the SEA capacity of conventional aluminum lattice and TPU truss lattice structure. These findings provided a novel structural design strategy for fabricating the plate-lattice architectures in conjunction with additive manufacturing.

Experimental testing of selected energy absorbers in the context of their use in rear underrun protective devices

The energy-absorbing structures have been being developed for many years by various research centres all over the world. The article presents experimental test results obtained for selected structures designed for the absorbing of kinetic energy in order to reduce the loads on occupants of a motorcar when hitting the rear of a motor truck. The differences between selected energy-absorbing structures have been analysed, based on impact resistance indicators having been determined. The main objective of this research work was to verify the applicability of selected energy absorbers to the rear underrun protective devices as the truck parts accountable for vehicles’ passive safety.

Investigation of design and self-recovery characteristics of multicellular energy-absorbing structures manufactured via laser powder bed fusion

Direct structuring of three-dimensional structures by laser powder bed fusion (LPBF) offers a higher degree of freedom in structural design and solves the difficult problem of traditional machining for complex structural parts. Here, we report the energy absorption characteristics of different multicellular structures manufactured via LPBF. We evaluate the energy absorption properties for different multicellular structures [triangular multicellular structure, quadrilateral multicellular structure, pentagonal multicellular structure (PMS), hexagonal multicellular structure, and octagonal multicellular structure (OMS)] by experimental and numerical calculations. The accuracy of the simulation is verified by comparing the deformation and force–displacement curves of different structures. The PMS has the best overall performance, with specific energy absorption and crushing force efficiency being 3331 mJ and 3165.74 J/kg, respectively. At the same time, the shape memory effect of all structures under 15% deformations is more than 95%. However, partial failure of the OMS occurred within 15% of the deformation. Therefore, the problem of partial failure of the structure under low deformation is a critical problem to be solved urgently in the future.

Bending Response of Lattice Structure Filled Tubes under Transverse Loading

Thin-walled tubes are widely used as passive energy-absorbing structures in a variety of industries. These structures are typically filled with lightweight materials to improve their energy absorption capabilities. At this point, additive manufacturing technology offers a great chance researchers for the production of novel filler structures to increase the crashworthiness performance of thin-walled tubes. In the current work, additive manufacturable body-centered cubic (BCC) lattice structures are suggested as filling materials for thin-walled tubes, and the bending response of these structures is investigated under transverse loads via a finite element modeling approach. The aspect ratio and strut diameter are considered as design parameters, and three-point bending simulations are conducted to understand the transverse load bearing behaviors of the structures. Different loading offsets are also taken into account for three-point bending simulations. The numerical results revealed that the BCC lattice structures used as filler materials significantly increase the energy absorption performance of thin-walled tubes due to synergetic interactions. In particular, the simulation results revealed that the hybrid tubes can absorb up to 84% more energy than the empty tubes, while the crush force efficiency of these structures is up to 42% higher compared to the empty tubes. The present study also showed that the transverse crushing characteristics of tubes can be considerably improved by suitable selection of the design parameters. These primary outcomes reveal that the proposed lattice structures can be considered as a potential alternative to traditional filler materials for enhancing the bending response of thin-walled tubes under transverse loading.

Crashworthiness investigation of draw bead in aluminum tubes under axial loading condition

This study aims to investigate the effects of the draw beads on the crashworthiness of the aluminum tubes under axial quasi-static loading. Based on this design philosophy, a total of 12 beading tube designs with various configurations were developed. Within each design, the effect of arrangement bead form on the crashworthiness performance was also analyzed. A finite element model, validated using experimental tests, was used to study the crashworthiness performance and progressive deformation of the tubes. Based on the results, a multi-criteria decision-making method known as Technique of Order Preference by Similarity to Ideal Solution was employed to determine the most suitable tube that features high energy absorption and low impact force. The best tube with a high score was selected to investigate the effect of bead formed direction on aluminum tubes. Consequently, the study identified a bead shape tubes configuration that exhibits superior crashworthiness and low impact force. The beading tube design methodology presented in this study allows the exploitation of variable shapes geometries for the development of high-efficiency energy-absorbing structures and their crushing behaviors.

Mechanical performance of triply periodic minimal surface structures with a novel hybrid gradient fabricated by selective laser melting

Triply periodic minimal surface (TPMS) structures have been extensively investigated for their excellent mechanical properties and lightweight potential. In this study, a new hybrid gradient (HG) TPMS structure was proposed by combining geometrically deformed gradient (GDG) and volume fraction gradient (VFG). All designed structures were fabricated by selective laser melting (SLM) using Ti-6Al-4V. They were investigated experimentally in terms of deformation behavior, stress–strain curve and energy absorption. The results demonstrated that the GDG structure can develop a better deformation mode to enhance the energy absorption, while the VFG structure can help to reduce the initial peak force and delay the densification point. Most importantly, the hybridization of these two gradients can both greatly enhance the energy absorption capacity and delay the densification point. Compared with the uniform structures, the hybrid gradient structures can almost double the energy absorption under compression. The results of this research may provide valuable insights for the design of high-performance energy-absorbing structures in the future.

Optimization design of the coupler overload protection component: numerical simulation and experimental validation

Under the impact condition, the coupler buffer device faults because of overload, the connection of the car body fails and the energy absorption structure in the front end of the vehicle absorbs energy through collision contacts, which is an important process for achieving passive safety protection of a train. Controlling the threshold of the impact force for overload protection and matching it with the compressive strength of the car body structure is the focus of this article. In this article, two schemes of setting the induction groove and optimizing the rounded cross-section are proposed, and collision dynamics analysis is carried out. The value of the fracture force under the induction groove setting is 2602.31 kN, and the optimized round cross-section is 2262.08 kN. The results show that, compared with the initial structure, the fracture force under the two induction methods decreased by 6.46% and 18.69%, respectively. The tensile and compressive strengths of both structures satisfy the strength requirements of the operating conditions. The cross-section optimization method is more effective than the induction slot method. The impact experiment was carried out on the second structure, and the fracture force obtained was 2285.12 kN. The deformation mode and fracture force are basically consistent with the simulation results. The optimized coupler overload protection device effectively improves the safety performance of a train in operation.