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Cutting-type structures, because of their desirable mechanical characteristics, high energy absorption capabilities and excellent guiding performance, has been extensively employed in high-speed trains. Its lightweight design and optimization problems are also the hotspot of research directions in present. This paper designed a new-type structure, i.e., magnesium alloy cutting-type energy-absorbing structure (CTEAS), taking into account its excellent properties of high lightweight level and ease of processing demonstrated through AZ31B magnesium alloy tensile mechanical test. Subsequently, experimental study on magnesium alloy CTEAS are conducted by trolley impact tests of train considering different cutting depths and different velocity levels. The results confirmed the outstanding advantages, including high lightweight level and higher absorbed energy properties, and lower demands of knives, compared with the structures with Q345 steel. In addition, the mechanism of knives cracking and melting phenomenon found in the experiment is explored by finite element analytical method. The results show that the temperature difference between the high-temperature surface and the interior during the cutting Q345 steel process is maybe the key influencing factor leading to knives damage. This research provides an effective tool for the design and analysis of excellent performance energy absorbing structure of high-speed trains. • AZ31B magnesium alloy can be used to cutting-type energy-absorbing structures. • Magnesium alloy structure has outstanding advantages in lightweight and higher SEA. • Temperature of the tools during the cutting process of Q345 steel is more than 900 °C. • Temperature of the tools is less than 800 °C when AZ31B magnesium alloy is cut. [ABSTRACT FROM AUTHOR]

• A collision scene of high-speed train-moose collision was applied to the study. • A full finite element model of the moose was developed and validated. • Considering the impact on the pantograph after the obstacle was hit. • The collision force and trajectory of the moose after being hit were analyzed. Collisions between trains and moose that cross a track are common occurrences according to rail accident statistics. A moose lying on a track after a crash may increase the risk of train derailment. In addition, a moose thrown into the air during a collision may also hit and damage the pantograph, which prevents a train from running. This paper developed a finite element (FE) model of moose and is aimed at investigating the train crash safety and moose motion trajectory in train-moose collisions for different moose crossing scenarios using the FE method. Material biomechanics tests were conducted to obtain the mechanical property parameters of moose. Drop hammer impact tests were performed to validate the constitutive models of different moose segments. The whole moose FE model was verified against previous vehicle-moose crash tests. The numerical impact scenes of moose crossing the rail at different collision positions were established in LS-DYNA. The results showed that the impact force depends on the contact area between the train and the moose. A larger contact area corresponded to a larger impact force. The moose would be pushed away by the V-shaped locomotive and would not cause a derailment, and the height of the moose thrown into the air cannot reach the height of the pantograph, which would prevent damage to the pantograph of a bullet train. [ABSTRACT FROM AUTHOR]

• The higher the order of BDFS is, the better the crashworthiness performance will be. • Structures with regular polygonal wall are better than circular with the same ribs. • The SEA, PCF and ULC of any structure are not all the best. • BDFS with six ribs and 3rd-order parting have the best comprehensive performance. • A hybrid multi-stage optimization decision system, i.e., MCDM-MOP-MCDM, is proposed. Rail vehicles offer the characteristics of large carrying capacity and high running speed. Train accidents usually result in substantial personal casualties and economic losses. Energy-absorbing structures can efficiently and quickly absorb and disperse the energy generated during collisions. In this paper, the performances with different cross-sections and partings of the bionic dendritic furcal structure (BDFS) inspired by the furcal branch and bifurcation structure of neurons are analyzed and compared by numerical simulation. The simplified super folding element theory and experiments verify that the finite element models are effective. A hybrid multi-stage optimization decision system, i.e., multi-criteria decision-making (MCDM)- multi-objective optimization (MOP)- MCDM, which integrates the VlseKriterijumska Optimizacija I Kompromisno Resenje (VIKOR) method, the multiple objective particle swarm optimization-crowding distance (MOPSO-CD) evolutionary algorithm and repetitive VIKOR method, is proposed to find the optimal structure and obtain the optimal parameter alternative of the structure. Comparisons and analyses of experiments and simulations are carried out to verify the effectiveness of the proposed method. The results show that BDFS with six furcal ribs and 3rd-order parting display the best comprehensive crashworthiness under the working condition of 10 m/s specified in EN15227 standard. When the single target requirement is considered, specific energy absorption (SEA) can be increased by 16.18%, peak crushing force (PCF) can be decreased by 67.07%, and undulation of the load-carrying capacity (ULC) can be decreased by 14.02%. This study provides an effective tool for the analysis and optimization of energy-absorbing structures. [Display omitted] [ABSTRACT FROM AUTHOR]

Lightweight design of high temperature ceramic is in urgent need, as their engineering application requires higher payload. Current approach to design lightweight ceramic is either porous ceramics or ceramic foams. Here, as a new approach, ZrO 2 ceramic corrugated core sandwich panel is proposed for lightweight design. The high temperature mechanical behaviors are systematically obtained through experimental measurements, theoretical analysis and numerical simulation. Under room temperature and 1000 °C, the compressive strength are as high as 11.8 and 8.5 MPa, and the stiffness are 375.9 and 340.9 MPa, which agree well with the analytical predictions. The specific bending strengths are 124.3 MPa/(g/cm 3 ) under room temperature and 114.6 MPa/(g/cm 3 ) under 1000 °C, which are twice higher than that of the ZrO 2 bulk ceramic. We reveal that with increasing temperature up to 1000 °C, the critical relative density for the failure models under compression shows significant change, while the failure model boundaries under three point bending display small difference. Moreover, the finite element analysis reveals that distinguished stress peaks are as high as 748 MPa in compression and 710 MPa in bending. The peak stresses locate at the connections between the facesheets and core sheets, and illustrate the failure mechanism of the experimentally observed failure models. [ABSTRACT FROM AUTHOR]

• Proposed a method to simulate the residual stress in tempered glass. • Developed a simulation framework for tempered laminated glass. • Characterized the typical crack features and propagation process of tempered laminated glass. • Formulated the relationships between geometrical variables and impact mechanical responses. The tempered laminated windshield used in high speed train is different with that used in auto. This work aims to study the crack propagation and dynamic impact responses of tempered laminated windshield. To achieve this point, a cohesive element based finite element model that take residual stress into consideration was built and validated by safety hammer impact experiment. Afterwards, the crack features and propagation process were characterized. The simulation results show that the fracture fronts in the interior tensile zone is ahead of that in the near surface compression zone and the fragment is much smaller than that of float glass, which demonstrate residual stress has significant influence on fracture mechanism and crack modes. And then, a parametric discussion about the influence of impact velocity and thickness of tempered laminated glass's components on the impact performances were carried out and correlated. The results show that the impact responses are velocity sensitivity. The front glass layer (G1) has more significant effects on the energy absorption and peak acceleration comparing with back glass layer (G2). In practical engineering application, increasing the thickness of PVB film appropriately could not only reduce peak acceleration but also consume more impact kinetic energy. [ABSTRACT FROM AUTHOR]

Abstract: The objective of the present study is to investigate the mechanical behavior of windshield laminated glass in the case of a pedestrian's head impact. Windshield FE models were set up using different combinations for the modeling of glass and PVB, with various connection types and two mesh sizes (5 mm and 10 mm). Each windshield model was impacted with a standard adult headform impactor in an LS-DYNA simulation environment, and the results were compared with the experimental data reported in the literature. The results indicated that the behavior of the windshield model with a double-layered shell of glass and PVB and a tied element connection support test results from previous studies. Furthermore, the influence of glass fracture stress on the same windshield model was investigated, and the cracked area and the peak value of the headform's linear acceleration were determined by the critical fracture stress. It was observed that a 50-MPa fracture stress in the glass best predicted the observed headform's linear acceleration level and the cracks of the windshield at the time of impact. [Copyright &y& Elsevier]

The engineering materials and structures, which usually suffer both temperature variation and mechanical loading, motivate the urgent need of the multifunctional metamaterials with simultaneously programmable coefficient of thermal expansion (CTE) and Poisson's ratio (PR). Whereas, the current 3D metamaterials can not continuously program the CTE and PR. Herein, a class of 3D metamaterial is originally devised by an exclusive geometrical methodology. The explicit expressions of the CTE and PR are theoretically established and are also verified by the numerical modeling. The analysis confirms that the CTE can be widely tailored by varying the geometrical parameters and selection of the constituents. Besides, the controllable PR can be also easily obtained by adjusting the geometrical parameters. Moreover, the devised 3D metamaterial gives paired tailorable CTE and controllable PR, including especially negative CTE + negative PR. An arrangement rule is developed to construct a series of hierarchical cells which can program CTE and PR in multi principle axes and can be periodically arrayed for obtaining the 3D cellular metamaterials. The devised 3D metamaterials are capable of realizing the widely coupled programmability of both CTE and PR and provide a strategy of shape morphing stimulated both by temperature variation and mechanical loading. [ABSTRACT FROM AUTHOR]

• A combination of the gradient perforated porous absorber and coiled resonator is studied. • The resonance of coiled-up channel intennsifies energy dissipation in porous materials. • Absorption performance is studied by theoretical models based on the transfer matrix method. • Parallel-connection unit cells achieve low-frequency broadband (211-3000 Hz) semi-sound absorption. A compact structure comprising the gradient perforated porous material and the coiled-up channel (GPPC) is proposed. The sound absorption performance is investigated by a theoretical model based on the transfer matrix method (TMM) and simulation with the finite element method (FEM), and the simulations are experimentally validated. Broadband absorption of porous material can be shifted to a lower frequency and enhanced by coiled-up channel of GPPC, which are due to the resonances of the meso-pore with coiled-up channel and the coupling effect of multiscale porous material and coiled-up channel, and the energy trapping between the meso-pore and porous material matrix. The effects of the geometry parameters of the meso-pore and coiled-up channel on the absorption properties are also discussed. Moreover, the absorption enhancement of GPPC relative to homogeneous porous relies on a proper porous material matrix. Finally, the GPPCs with a width and thickness of 70 × 100 mm is designed by parallel coupling, and the absorption coefficient exceeds 0.7 at [240, 3000] Hz, which is promising in engineering noise control and provides some preliminary understanding of the combination of the gradient perforated porous absorber and the coiled resonator. [Display omitted] [ABSTRACT FROM AUTHOR]

To improve the crash performance of subway vehicles, this study presents an investigation of a newly designed gradual energy-absorbing structure subjected to impact loads using a test trolley for experimental and numerical simulations, as referenced in EN15227:2008. The structure is composed of a front-end beam, rear-end plate, outer-side beams, inner-side beams, cross beams and longitudinal beams. In this work, a finite element model (FEM) was established and effectively verified using experimental data. To evaluate the effect of the thicknesses of the longitudinal beams ( t 1 ), outer-side beams ( t 2 ) and inner-side beams ( t 3 ) on the energy absorption ( EA ) and peak crushing force ( F p ), sensitivity study was performed using extreme difference ( R ) analysis. Then, a polynomial response surface method (PRSM) was employed to formulate the output responses of EA and F p with the input parameters of t 1 , t 2 and t 3 . In order to optimize the crash performance of the structure, a Non-dominated Sorting Genetic Algorithm (NSGA) was used in a multi-objective optimization to achieve the maximum EA and minimum F p values. The optimal EA and F p with the associated thickness parameters ( t 1 , t 2 , and t 3 ) of the gradual energy-absorbing structure were obtained in the form of Pareto fronts. Additionally, the Pareto solutions derived from the surrogate models of the quadratic, cubic and quartic polynomials eventually converge at intersection D (i.e., F p =7.2940×10 3 kN, EA =1.3511×10 3 kJ). [ABSTRACT FROM AUTHOR]

This work investigated the energy absorption behavior of expansion circular tubes. This kind of energy absorption device dissipates the impact of kinetic energy through plastic deformation and friction. A finite element model (FEM) was established with reference to the size of the coupler, which was used for connecting two vehicles. A special case was designed to validate the accuracy of the FEM. Furthermore, a theoretical prediction model that took into consideration the additional shear deformation and expansion ratio enlargement was compared with the steady compressional force of the experiment and numerical simulation. The theoretical prediction was accurate. Based on this valid FEM, a series of parameter studies was developed. Specifically, a list of conical mandrels with different angles from 5° to 40° was established, and the coefficient of friction varied from 0 to 0.3. Both had great influence on energy absorption. The relationship between the expansion angle and steady compressional force is nonlinear, while the friction coefficient and steady compressional force are linear. With friction, the inflection point of force curve existed between 10° and 20°. [ABSTRACT FROM AUTHOR]