动态冲击荷载作用下橡胶材料吸能率分析

橡胶材料作为一种高分子复合材料,具有很好的减震吸能特性,在防护结构设计中通常作为重要的吸能减震材料。采用改进的SHPB试验装置,对3种不同配比的橡胶材料进行了试验研究,结果表明:橡胶的应变率效应十分明显,橡胶的硬度是影响吸能率的重要因素。

基于吸能率的车辆碰撞相容性分析及优化设计

开展了车辆防撞性和碰撞相容性的设计分析,提出了一种新型相容性指标——吸能率rE并验证其合理性,该指标可望解决现有评价指标对车辆侵入程度的量化缺乏连续性和普适性的问题。然后对参数化模型进行自动更新,从而进行设计变量优化求解,最终形成一套集成设计方法。工程实例显示,提出的吸能率指标rE可实现对目标车辆攻击性程度的连续量化评估,参数化优化策略可有效提升车辆碰撞相容性和设计优化效率。

Carbon-Epoxy圆管件的静态吸能特征

Carbon/Epoxy 复合材料可以用作理想的吸能材料。为了考察材料体系对结构吸能性能的影响,对一系列Carbon/Epoxy圆管件进行了静态吸能性能试验。试验结果表明,在基体种类相同的条件下,结构的压溃失效模式有很大的区别。材料的吸能性能不仅同材料性能关系密切,而且也受材料纤维方式影响。

填充泡沫铝的多层铝管动态压溃吸能特性研究

采用数值模拟的方法研究和分析了无填充物的多层铝管结构的吸能特性,结果发现多层铝管相比单层铝管,不但具有较大的吸能量,而且还具有较高的比吸能率;在此基础上,设计了不同层数的多层管泡沫铝填充结构,研究发现泡沫铝不但受轴向压溃变形,同时也受到了铝管层之间的相互作用力使其在径向发生了变形;之后对多层管填充3种不同密度的泡沫铝,采用变参分析的方法研究了多层管层数和泡沫铝密度对整个结构吸能特性的影响;研究结果表明:填充泡沫铝的多层管,随着层数的增加,其比吸能率和吸能量也随之有所增加,随着泡沫铝密度的提高,比吸能率的提高量开始下降,但仍高于填充相同泡沫铝的单层管。

工业安全帽抗冲击性能研究

为研究安全帽安全性与保护性问题,利用落锤冲击实验,对不同材质安全帽吸能率、冲击力峰值进行研究。结果表明:随冲击能量增加,安全帽受冲击力峰值呈指数倍增长,吸能率呈指数倍下降;ABS树脂与玻璃钢材质安全帽头模受冲击力峰值小于HDPE材质安全帽;当冲击能量大于60 J,HDPE材质安全帽丧失保护功能;ABS安全帽能够承受最大冲击力能量值为70 J,玻璃钢安全帽最大承载力高于ABS树脂安全帽。研究结果可为安全帽质量设计提供理论依据。

城市轨道车挡防撞液压缓冲系统仿真研究

针对城市轨道失控车辆在轨道终端产生的撞击动能问题,采用液压缓冲油缸车挡防撞装置进行动能吸收,提出一种城市轨道车挡防撞液压缓冲系统,对城市轨道车挡防撞液压缓冲系统工作原理进行了研究,利用AMESim对车挡防撞液压缓冲系统仿真模型进行了搭建,对系统动态性能开展了仿真分析,并仿真研究了失控车辆质量、溢流阀开启压力对系统性能的影响情况,进一步归纳计算了系统吸能率,最后分析了控制车辆缓冲制动位移措施。研究结果表明:城市轨道车挡防撞液压缓冲系统对失控车辆实现了匀减速制动;车挡防撞液压缓冲系统吸能率可达到95%以上;失控质量增大,系统吸能率先减小后增大;溢流阀开启压力增大,系统吸能率也增大;增大溢流阀开启压力、缓冲油缸活塞有效面积可缩短车辆缓冲制动位移。

汽车平台化开发前舱空间的正向设计方法研究

整车耐撞安全性是车身平台架构设计的一项重点问题,本文提出了一种基于区段能量统计的车身结构耐撞性评价方法。通过此方法,在总布置阶段可以获取整车G-S曲线,供安全开发部门参考评估。文中提出了区域段吸能率的概念,通过对区域段吸能率的评估,可以判断不同空间布置下压溃空间利用率情况,以指导结构设计。

Elasto-plastic constitutive model of aluminum alloy foam subjected to impact loading

A multi-parameter nonlinear elasto-plastic constitutive model which can fully capture the three typical features of stress-strain response, linearity, plasticity-like stress plateau and densification phases was developed. The functional expression of each parameter was determined using uniaxial compression tests for aluminum alloy foams. The parameters of the model can be systematically varied to describe the effect of relative density which may be responsible for the changes in yield stress and hardening-like or softening-like behavior at various strain rates. A comparison between model predictions and experimental results of the aluminum alloy foams was provided to validate the model. It was proved to be useful in the selection of the optimal-density and energy absorption foam for a specific application at impact events.

Calculation of Electromagnetic Field and SAR Dis- tributions of Two Antenna Structures for Bone Tu- mors Microwave Hyperthermia

Objective: To investigate the electromagnetic field and specific absorptionrate (SAR) distribution of different structure applicators with different depths for treating bonetumors using microwave hyperthermia. Methods: The finite element method (FEM) was used to calculate,electromagnetic field and SAR distribution. Two different structure applicators were simulated. Theone is simple coaxial antenna, which has been successfully used in clinic treating bone tumors inTangdu hospital of the Forth Military Medical University several years. It was formed by a coaxialcable peeled off the out copper at end. The other applicator was coaxial- slot antenna, which waswidely used in microwave hyperthermia. The applicator inserted into the cylindrical bone withdifferent depths, and worked at the frequency of 2 450 MHz. Results: The electric field and SARgenerated by the simple coaxial applicator were mainly concentrated out the tissues, and were notuniform in the tissues, while the coaxial- slot applicator well transmits the electric field and SARinto the tissues, and can easily treat different position by adjusting the slat position.Conclusion: The results calculated by EFM, were well accordant with the experimental and clinicalresulls, and will be important for improving the clinical effects of microwave hyperthermia.

Estimation of Net Primary Productivity of Terrestrial Vegetation in China by Remote Sensing

Among the many approaches for studying the net primary productivity (NPP), a new method by using remote sensing was introduced in this paper. With spectral information source (the visible band, near infrared band and thermal infrared band) of NOAA-AVHRR, we can get the relative index and parameters, which can be used for estimating NPP of terrestrial vegetation. By means of remote sensing, the estimation of biomass and NPP is mainly based on the models of light energy utilization. In other words, the biomass and NPP can be calculated from the relation among NPP, absorbed photosynthetical active radiation (APAR) and the rate (epsilon) of transformation of APAR to organic matter, thus: NPP = ( FPAR x PAR) x [epsilon * x sigma (T) x sigma (E) x sigma (S) x (1 - Y-m) x (1 - Y-g)]. Based upon remote sensing ( RS) and geographic information system (GIS), the NPP of terrestrial vegetation in China in every ten days was calculated, and the annual NPP was integrated. The result showed that the total NPP of terrestrial vegetation in China was 6.13 x 10(9) t C . a(-1) in 1990 and the maximum NPP was 1 812.9 g C/m(2). According to this result, the spatio-temporal distribution of NPP was analyzed. Comparing to the statistical models, the RS model, using area object other than point one, can better reflect the distribution of NPP, and match the geographic distribution of vegetation in China.

Collision performance of bitubular tubes with diaphragms

A numerical study of bitubular tubes with diaphragms compared with single and bitubular tubes subjected to dynamic axial impact force was presented. At first, the energy absorption response of the composite structure under axial loading was analyzed by finite element simulation. The results show that the efficiency of energy absorption can be improved by introducing diaphragms to the double-walled columns. Then, the effect of the amount and location of diaphragms, the shape and the size of the inner tubes, and the thickness of the composite structures were also studied numerically. The collision performance of the composite structure is affected by the deformation of diaphragms, as well as the interaction of outer and inner tube. The non-uniform distribution of diaphragms can improve the energy absorption efficiency of structures for a constant number of diaphragms. The specific energy absorption of the hexagonal inner tube is the highest, followed by the circular, octagonal and square ones.

Synthesis of activated carbon from spent tea leaves for aspirin removal

Adsorption capacity of activated carbon prepared from spent tea leaves （STL-AC） for the removal of aspirin from aqueous solution was investigated in this study. Preliminary studies have shown that treatment with phosphoric acid （H3PO4） increased removal efficiency of STL-AC. Characterizations on STL-AC revealed excellent textural properties （1200 m2.g-1, 51% mesoporosity）, as well as distinctive surface chemistry （1.08 mmol.g-1 and 0.54 mmol.g-1 for acidic and basic oxygenated groups, pHpzc = 2.02）. Maximum removal efficiency of aspirin observed was 94.28% after 60 rain when the initial concentration was 100 mg.L-1, 0.5 g of adsorbent used, pH 3 and at a temperature of 30 ℃. The adsorption data were well fitted to the Freundlich isotherm model and obeyed the pseudo-second order kinetics model. The adsorption of aspirin onto STL-AC was exothermic in nature （△H = - 13.808 kJ.mol-1） and had a negative entropy change, △S （-41.444 J.mol-1）. A negative Gibbs free energy, △G was obtained indicating feasibility and spontaneity of the adsorption process. The adsorp- tion capacity of △C-STL （178.57 mg.g-1） is considerably high compared to most adsorbents synthesized from various sources, due to the well-defined textural properties coupled with surface chemistry of STL-AC which fa- vors aspirin adsorption. The results demonstrate the potential of STL-AC as aspirin adsorbent.

Dynamic rupture and crushing of an extruded tube using artificial neural network(ANN)approximation method

A numerical study of the crushing of thin-walled circular aluminum tubes has been carried out to investigate the crashworthiness behaviors under axial impact loading. These kinds of tubes are usually used in automobile and train structures to absorb the impact energy. Previous researches show that thin-walled circular tube has the highest energy absorption under axial impact amongst different structures. In this work, the crushing between two rigid flat plates and the tube rupture by 4 and 6 blades cutting tools is modeled with the help of ductile failure criterion using the numerical method. The tube material is aluminum EN AW-7108 T6 and its length and diameter are 300 mm and 50 ram, respectively. Using the artificial neural network （ANN）, the most important surfaces of energy absorption parameters, including the maximum displacement of the striker, the maximum axial force, the specific energy absorption and the crushing force efficiency in terms of impact velocity and tube thickness are obtained and compared to each other. The analyses show that the tube rupture by the 6 blades cutting tool has more energy absorption in comparison with others. Furthermore, the results demonstrate that tube cutting with the help of multi-blades cutting tools is more stable, controllable and predictable than tube folding.

Precipitation Pulses and Soil CO_2 Emission in Desert Shrubland of Artemisia ordosica on the Ordos Plateau of Inner Mongolia,China

Precipitation is the major driver of ecosystem functions and processes in semiarid and arid regions. In such waterlimited ecosystems, pulsed water inputs directly control the belowground processes through a series of soil drying and rewetting cycles. To investigate the effects of sporadic addition of water on soil CO2 effux, an artificial precipitation event （3 mm） was applied to a desert shrub ecosystem in the Mu Us Sand Land of the Ordos Plateau in China. Soil respiration rate increased 2.8 4.1 times immediately after adding water in the field, and then it returned to background level within 48 h. During the experiment, soil CO2 production was between 2 047.0 and 7 383.0 mg m^-2. In the shrubland, soil respiration responses showed spatial variations, having stronger pulse effects beneath the shrubs than in the interplant spaces. The spatial variation of the soil respiration responses was closely related with the heterogeneity of soil substrate availability. Apart from precipitation, soil organic carbon and total nitrogen pool were also identified as determinants of soil CO2 loss in desert ecosystems.

Adsorptive potential of Acacia nilotica based adsorbent for chromium(Ⅵ) from an aqueous phase

The objective of this research was to enhance adsorption capacity of Acacia nilotica （keekar） sawdust for the abatement of chromium bearing wastewater and to investigate the effect of process parameters on adsorption capacity. The sawdust was activated by acid wash and functionalized subsequently with formaldehyde. Functionalization of activated sawdust raised its chromium removal efficiency of almost 10% as compared to its adsorption removal efficiency of HCl treated sawdust in a batch adsorption study. Adsorption kinetic data provided better fitting with pseudo second order model. Maximum adsorption capacity calculated through the best fitting Langmuir model was 6.34 mg·g^-1 and 8.2 mg·g^-1 for HCl treated and formaldehyde functionalized sawdust adsorbents, respectively. The adsorption of Cr（VI） was endothermic when studied by varying temperature from 20℃ to 50℃ for both activated and functionalized adsorbents.

Dynamic Adsorption of Microwave Modified Attapulgite on Micro-polluted Phenol Wastewater

[Objective] The paper was to study the dynamic adsorption of microwave modified attapulgite on micro-polluted phenol wastewater. [Method] Cetyl trimethyl ammonium bromide （CATB） modified attapulgite was used to modify attapulgite, and conducted dynamic test on micro-polluted phenol wastewater. The dynamic charac- teristics of phenol removal were also studied. [Result] Attapulgite modified by CATB has strong adsorption ability on phenol in micro-polluted water, the phenol removal rate increased with the decrease of flow rate of wastewater. When pH value was 6- 8, phenol concentration in wastewater was 17.74 mg/L, flow rate was 2 m/s and ad- sorption time was 25 rain, the removal rate reached 93.07%. The modified atta- pulgite could be regenerated with alkali, and its adsorption ability after regeneration had no obvious decline. The dynamic adsorption process of phenol accorded with the first-order kinetic equation. [Conclusion] The study provided basis for further study on ＂organic matter removal in wastewater.

Glass formation,thermal and mechanical properties of ZrCuAlNi bulk metallic glasses

The glass forming ability, thermal and mechanical properties of some Zr Cu Al Ni bulk metallic glasses were analyzed. The compositions of the alloys were theoretically determined with the dense packing and kinetic fragility index models. Cylindrical and conical ingots were produced by copper mould suction-casting under Ar atmosphere. The conical ingots were characterized by means of X-ray diffraction in order to determine the glassy structure. It was found that both alloys have a critical glassy diameter, Dc, of 3 mm. Thermal behaviours were investigated by differential scanning calorimetry at heating rates of 0.5, 0.67 and 0.83 K/s. The gamma parameter γ, supercooled liquid region ΔTx, and reduced glass transition temperature Trg, of the experimentally obtained glasses indicated high glass forming ability. The glassy compositions showed a fragility index of ~40 GPa. The compression test of the investigated alloys was carried out at a strain rate of 0.016 s^-1, obtaining a elastic modulus of ~83 GPa, total deformation of ~5%, yield strength of 1.6 GPa and hardness of 4 GPa. It was concluded that the use of the dense packing and kinetic fragility index models helped to predict glass-forming compositions in the family alloy investigated.

Effect of Phenylephrine on Alveolar Fluid Clearance in Ventilator-induced Lung Injury

Objective To investigate the effect of phenylephrine （an α-adrenergic agonist） on alveolar fluid clearance （AFC） in ventilator-induced lung injury and the possible mechanism involved. Methods A total of 170 male Wistar rats were randomly allocated into 17 groups （n= 10） using ran- dom number tables. Short-term （40 minutes） mechanical ventilation with high tidal volume （HVT） was per- formed to induce lung injury, impair active Na＋ transport and lung liquid clearance in the rats. Unventilated rats served as controls. To demonstrate the effect of phenylephrine on AFC, phenylephrine at different con- centrations （1×10^-5, 1 ×10^-6, 1×10^-7, 1×10^-8, and 1×10^-9 mol/L） was injected into the alveolar space of the HVT ventilated rats. To identify the influence of adrenergic antagonists, Na＋ channel, and microtubular sys- tem on the effect of phenylephrine, phenylephrine at 1×10^-5mol/L combined with prazosin （an α1-adrener- gic antagonist, 1×10^-4 mol/L）, yohimbine （an α2-adrenergic antagonist, 1×10^-4 mol/L）, atenolol （a β1- adrenergic antagonist, 1×10^-5 mol/L）, ICI- 118551 （an β2-adrenergic antagonist, 1×10^-5 mol/L）, amiloride （a Na＋ channel blocker, 51×10^-4mol/L）, ouabain （a Na＋/K＋-ATPase blocker, 5~×10^-4mol/L）, colchicine （a mi- crotubular disrupting agent, 0.25 mg/100 g body weight）, or β-lumicolchicine （an isomer of colchicine, 0.25 mg/100 g body weight） were perfused into the alveolar space of the rats ventilated with HVT for 40 minutes. AFC and total lung water content were measured. Results Basal AFC in control rats was （17.47±2.56）%/hour, which decreased to （9.64± 1.32）%/hour in HVT ventilated rats （P=0.003）. The perfusion of phenylephrine at 1 ×10^-8, 1×10^-7, 1×10^-6, and 1×10^-5 mol/L significantly increased the AFC in HVT ventilated rats （all P〈0.05）. This effect of phenylephrine on AFC was suppressed by prazosin, atenolol, and ICI-118551 in HVT ventilated rats by 53%, 31%, and 37%, respectively （all P〈0.05）. The AFC-stimulating effect of phenylephrine was lowered by 33% and 42% with amiloride and ouabain, respectively （both P〈0.05）. Colchicine significantly inhibited the effect of phenylephrine （P=0.031）. Conclusion Phenylephrine could increase the AFC in HVT-ventilated rats and accelerate the ab- sorption of pulmonary edema.

圆环列吸能器的力学机理及应用

为了进一步研究吸能器的机理,采用实验和数值模拟相结合的方法,对冲击载荷作用下6060T 5铝圆环列系统的动力学行为进行了研究。采用改进的SHPB实验系统并配以高速摄影设备,分别记录圆环列的入射波、透射波波形变化及变形过程。数值研究前,利用实验数据对计算模型和计算参数进行验证和标定。对工程实际中的若干工况进行了数值分析。结果表明,圆环列吸能器具有较高的吸能率,该系统通过弯曲塑性变形能来消耗冲击能量,回弹发生后整个吸能过程结束。在工程实际中,双层疏排圆环列组合方式是较好的选择。

Study on Absorption and Regeneration Performance of Novel Hybrid Solutions for CO_2 Capture

Recently, a kind of hybrid solution MEA-methanol shows a better CO_2 capture performance over aqueous MEA solution. However, the vaporization of methanol is the biggest disadvantage that hinders its application, so it is necessary to minimize the vaporization of methanol during both the absorption and regeneration processes. In this work, two kinds of hybrid solutions were studied and compared with aqueous MEA solution and MEA-methanol solution, including MEA/TEA/methanol solution and MEA/glycerol/methanol solution. The absorption property of MEA/glycerol/methanol solution is better than aqueous MEA solution within a certain period of time and the absorption property of MEA/TEA/methanol solution is too poor to be used in CO_2 capture. By increasing the concentration of TEA and decreasing the concentration of MEA, the absorption rate, CO_2 capture efficiency and absorption capacity all decreased. Upon adding glycerol, the cyclic capacity decreased and the generation temperature increased, and moreover, the density and viscosity also increased considerably. So after adding TEA and glycerol, the CO_2 capture performance of MEAmethanol solvent cannot be improved.