Recent research development of energy-absorption structure and application for railway vehicles

As the application of energy-absorption structure reaches an unprecedented scale in both academia and industry, a reflection upon the state-of-the-art developments in the crashworthiness design and structural optimization, becomes vital for successfully shaping the future energy-absorption structure. Physical impacting test and numerical simulation are the main methods to study the crashworthiness of railway vehicles at present. The end collision deformation area of the train can generally be divided into two kinds of structural design forms: integral absorbing structure design form and specific energy absorbing structure design form, and different energy-absorption structures introduced in this article can be equipped on different railway vehicles, so as to meet the balance of crashworthiness and economy. In pursuit of improving the capacity of energy dissipation in energy-absorption structures, studies are increasingly investigating multistage energy absorption systems, searching breakthrough when the energy dissipation capacity of the energy-absorption structure reaches its limit. In order to minimize injuries, a self-protective posture for occupants is also studied. Despite the abundance of energy-absorption structure research methods to-date, the problems of analysis and prediction during impact are still scarce, which is constituting one of many key challenges for the future.

Energy-absorption forecast of thin-walled structure by GA-BP hybrid algorithm

In order to analyze the influence rule of experimental parameters on the energy-absorption characteristics and effectively forecast energy-absorption characteristic of thin-walled structure, the forecast model of GA-BP hybrid algorithm was presented by uniting respective applicability of back-propagation artificial neural network （BP-ANN） and genetic algorithm （GA）. The detailed process was as follows. Firstly, the GA trained the best weights and thresholds as the initial values of BP-ANN to initialize the neural network. Then, the BP-ANN after initialization was trained until the errors converged to the required precision. Finally, the network model, which met the requirements after being examined by the test samples, was applied to energy-absorption forecast of thin-walled cylindrical structure impacting. After example analysis, the GA-BP network model was trained until getting the desired network error only by 46 steps, while the single BP-ANN model achieved the same network error by 992 steps, which obviously shows that the GA-BP hybrid algorithm has faster convergence rate. The average relative forecast error （ARE） of the SEA predictive results obtained by GA-BP hybrid algorithm is 1.543%, while the ARE of the SEA predictive results obtained by BP-ANN is 2.950%, which clearly indicates that the forecast precision of the GA-BP hybrid algorithm is higher than that of the BP-ANN.

Synthesis and anti-shock activity of divalent β-D-galactopyranosyl-(1→4)-β-D-glucopyranosides

Three divalent β-D-galactopyranosyl-（1 → 4）-β-D-glucopyranosides were synthesized using acetylated lactosyl bromide as donor and polyethylene glycols with different polymeric degree （n = 4, 5, 6） as linker, and evaluated for in vivo inhibitory activity to leukocyte-endothelial cell adhesion on severe bum-shock rats. The result showed that the length of linkers had apparent influence on anti cell adhesion activity.

Numerical simulation of the anti-shock performance of a gear case

Both sea battles and testing of ship in underwater explosions reveal unacceptably poor anti-shock performance of important shipboard equipment. Anti-shock performance of shipboard equipment is a significant factor determining fighting strength and survivability. The anti-shock performance of a shipboard gear case based on BV043/85 was investigated using numerical simulation. A geometric model of the gear case was built using MDT software and meshed in HyperMesh software, and then the finite element model of the gear case was formed. Using ABAQUS software, the anti-shock performance of the gear case was simulated. First, shock response of typical regions of gear case was determined. Next, some generalizations were made about the anti-shock performance of the gear case by analyzing the Mises stress of typical regions varied with shock inputs. Third, weak regions were determined from simulation results. The threshold values of shock resistance of the gear case at different impulse widths were obtained through interpolating the numerical simulation results selected from the most dangerous spot. This research provides a basis for further optimization of the design of gear cases.

A novel anti-shock silicon etching apparatus for solving diaphragm release problems

This paper presents a novel anti-shock bulk silicon etching apparatus for solving a universal problem which occurs when releasing the diaphragm （e.g. SiNx）, that the diaphragm tends to be probably cracked by the impact of heatinginduced bubbles, the swirling of heating-induced etchant, dithering of the hand and imbalanced etchant pressure during the wafer being taken out. Through finite element methods, the causes of the diaphragm cracking are analysed. The impact of heating-induced bubbles could be the main factor which results in the failure stress of the SiNx diaphragm and the rupture of it. In order to reduce the four potential effects on the cracking of the released diaphragm, an anti-shock hulk silicon etching apparatus is proposed for using during the last etching process of the diaphragm release. That is, the silicon wafer is first put into the regular constant temperature etching apparatus or ultrasonic plus, and when the residual bulk silicon to be etched reaches near the interface of the silicon and SiNx diaphragm, within a distance of 50-80μm （the exact value is determined by the thickness, surface area and intensity of the released diaphragm）, the wafer is taken out carefully and put into the said anti-shock silicon etching apparatus. The wafer＇s position is at the geometrical centre, also the centre of gravity of the etching vessel. An etchant outlet is built at the bottom. The wafer is etched continuously, and at the same time the etchant flows out of the vessel. Optionally, two symmetrically placed low-power heating resistors are put in the anti-shock silicon etching apparatus to quicken the etching process. The heating resistors＇ power should be low enough to avoid the swirling of the heating-induced etchant and the impact of the heating-induced bubbles on the released diaphragm. According to the experimental results, the released SiNx diaphragm thus treated is unbroken, which proves the practicality of the said anti-shock bulk silicon etching apparatus.

Dynamic crushing behavior and energy absorption of hybrid auxetic metamaterial inspired by Islamic motif art

Auxetic honeycomb structures are promising metamaterials with outstanding mechanical properties,and can be potentially used in energy absorption applications.In this study,a novel modified re-entrant hybrid auxetic metamaterial inspired by Islamic motif art is designed by integrating four-pointed double re-entrant motifs with symmetric semi-hexagonal unit cells to achieve a high energy absorption capacity(EAC).Theoretical analyses and numerical simulations are performed to examine the dynamic crushing behavior of the four-pointed double re-entrant combined structure(FDRCS).The developed finite element models(FEMs)are validated by the experiments under quasi-static compression.The deformation mode and stress-strain curves are further studied under low,medium,and high crushing velocities.The theoretically predicted plateau stress of the FDRCS under different crushing velocities is consistent with the numerical simulation results.The crushing stress and the EAC of the FDRCS are influenced by the geometric parameters and crushing velocities.The FDRCS exhibits a negative Poisson's ratio(NPR),owing to the four-point re-entrant structure(RES).Moreover,the specific energy absorption(SEA)of these structures is higher than that of nonauxetic hexagonal and auxetic re-entrant structures,owing to the generation of more plastic hinges that dissipate more energy during dynamic crushing.

Crashworthiness Analysis on Alternative Square Honeycomb Structure under Axial Loading

Hexagonal metal honeycomb is widely used in energy absorption field for its special construction. However, many other metal honeycomb structures also show good energy absorption characteristics. Currently, most of the researches focus on hexagonal honeycomb, while few are performed into different honeycomb structures. Therefore, a new alternative square honeycomb is developed to expand the non-hexagonal metal honeycomb applications in the energy absorption fields with the aim of designing low mass and low volume energy absorbers. The finite element model of alternative square honeycomb is built to analyze its specific energy absorption property. As the diversity of honeycomb structure, the parameterized metal honeycomb finite element analysis program is conducted based on PCL language. That program can automatically create finite element model. Numerical results show that with the same foil thickness and cell length of metal honeycomb, the alternative square has better specific energy absorption than hexagonal honeycomb. Using response surface method, the mathematical formulas of honeycomb crashworthiness properties are obtained and optimization is done to get the maximum specific energy absorption property honeycomb. Optimal results demonstrate that to absorb same energy, alternative square honeycomb can save 10% volume of buffer structure than hexagonal honeycomb can do. This research is significant in providing technical support in the extended application of different honeycomb used as crashworthiness structures, and is absolutely essential in low volume and low mass energy absorber design.

EFFECTS OF ACUPUNCTURE ON THE CONTENTS OF ENKEPHALINS IN DIFFERENT BRAIN REGIONS AND CORTICOSTERONE IN PLASMA OF RATS WITH ENDOTOXIN SHOCK

In this experiment,we have observed the effects of acupuncture on the contents ofenkephalins in different brain regions and corticosterone in plasma of rats with endotoxin shock.Theresults showed that after acupuncture the endogenous enkephalins were significantly decreased(P【0.05)in the midbrain and brain stem of endotoxin shock rats,suggesting the anti-shock of acupuncture might be related to the enkephalins in the midbrain and brain stem.In addition,there was a rising trend in plasma corticosterone of the rats with toxic shock.

Numerical research on dynamic response of naval equipments subjected to impact loads

When subjected to underwater explosion,the anti-shock performance of naval equipment is a key factor affecting the fighting capacity and safety of a war ship. For large-scale naval equipment,it is costly to do the shock test for its huge mass and large size. Consequently,the numerical research was carried our to study the shock resistance of the equipment. Taking turbo-charger set for example,its anti-shock performance was studied using software ABAQUS based on the time-domain shock analysis method presented in BV043 /85. According to the analysis results,shock response of typical regions is obtained,some regularity curves are concluded by analyzing the Mises stress of the typical regions,and the weak regions are found out. The study can provide some references on design of turbo-charger set.

Simulation and analysis of effects of Young’s modulus of isolation material on natural frequencies of the sensor package and displacement of the chip

For the first time an anti-shock packaging model of an acoustic-vibration sensor system has been designed by using the shocking isolation principle. The finite element analysis has been applied for design and simulation of the model. The effects of Young’s modulus of anti-shock rubber on naturally occurring frequencies of the combination of rubber and an acoustic sensor chip were analyzed. The displacement of the acoustic sensor chip is loaded with force. The results of static analysis and harmonic analysis show that while increasing Young’s modulus of anti-chock rubber, the first five natural frequencies of the package body also increases. Yet the displacement of the acoustic sensor chip around the resonant frequency decreases. The results of static and transient analysis show that the displacement of the acoustic sensor chip decreases with the increase of Young’s modulus of anti-chock rubber being loaded with either transient force or static force at the bottom of the combination of rubber and acoustic sensor chip.

Frequency Analysis and Anti-Shock Mechanism of Woodpecker＇s Head Structure

The mechanical properties of the skull and the anti-shock characteristics of woodpecker＇s head were investigated by ex- periment and numerical simulation. We measured the micro-Young＇s modulus of the skull by nano-indentation method and calculated the macro-equivalent Young＇s modulus of the skull at different positions using homogenization theory. Based on the Computerized Tomography （CT） images of woodpecker head, we then built complete and symmetric finite element models of woodpecker＇s skull and its internal structure and performed modal analysis and stress spectrum analysis. The numerical results show that the application of pre-tension force to the hyoid bone can increase the natural frequency of woodpecker＇s head. The first natural frequency under the pre-tension force of 25 N reaches 57 Hz, which is increased by 21.3% from the non-pre-tension state and is more than twice the working frequency of woodpecker （20 Hz 25 Hz）. On the application of impact force to the tip of beak for 0.6 ms, high magnitudes of stress component occur at around 100 Hz and 8,000 Hz, far away from both the working frequencies and the natural frequencies of woodpecker head. The large gaps among the natural, working and stress response frequencies enable the woodpecker to effectively protect its brain from the resonance injury.

Energy conversion in woodpecker on successive peckings and its role on anti-shock protection of brain

To investigate the mechanism of brain protection of woodpecker,we built a finite element model of a whole woodpecker using computed topography scanning technique and geometry modeling.Dynamic analyses reveal:(i)99.7%of the impact energy is converted into strain energy in the bulk of body and 0.3%is converted into strain energy in the head after three successive peckings,indicating the majority of the impact energy is stored in the bulk of body;(ii)the strain energy in brain is mainly converted into the dissipated energy,alleviating the mechanical injury to brain;(iii)the deformation and the effective energy dissipation of the beaks facilitate the decrease of the stress and impact energy transferred to the brain;(iv)the skull and dura mater not only provide the physical protection for the brain,but also diminish the strain energy in the brain by energy dissipation;(v)the binding of skull with the hyoid bone enhances the anti-shock ability of head.The whole body of the woodpecker gets involved in the energy conversion and forms an efficient anti-shock protection system for brain.

Anti-shock loading capability of a fluidized-bed flocculator

The efficiency of a fluidized-bed flocculator with 800-um particles of 1360 kg/m3 in density was studied, and the anti-shock capability of the unit was estimated for three kinds of industrial wastewater： heavy turbidity wastewater, dispersed dyeing wastewater and starch wastewater. Steady removal efficiency was contributed by the following characteristics of the flocculator： （1） the dynamic conditions, flocculation time and velocity gradient, which were stabilized at a steady level as the loading rate changed; （2） hydrodynamic characteristics, especially the considerable rise of expanded bed height with increasing superficial velocity when small and light particles were employed as the solid phase; （3） flocs growth characteristics in the fluidized bed, which caused the density and size of the flocs being maintained at a compensational relationship, resulted the stabilized settling velocity of the flocs.