汽车前部部件的碰撞吸能能力分析

汽车前部碰撞吸能区承担着主要的吸能缓冲的责任,对车内乘员的保护有重要作用,为提高其碰撞吸能能力,文章使用整车有限元模型,在LS-DYNA环境当中进行整车碰撞有限元分析。确定了FEMB前处理当中关键步骤及参数的确定,为进行有限元分析提供了方法依据。通过研究汽车正面碰撞过程中整车的运动状态及前部各吸能部件的吸能情况,得出:前部组件共吸收能量占整车吸收能量的47.74%,汽车前纵梁共吸收能量占整车吸收总能量的18.52%。故前纵梁组件为碰撞吸能的主要部件,为提高汽车安全性能分析提供了方向。

高速杆式弹侵彻下蓄水结构防护效能数值分析

为探讨蓄水结构抗侵彻防护效能,采用动态非线性有限元,结合箱型蓄水结构弹道冲击试验,分析了蓄水结构在高速杆式弹侵彻下的防护效能及水介质对结构吸能性能的影响,并将有限元结果与试验结果进行了比较,两者吻合良好。比较结果表明:水介质的抗侵彻吸能能力随弹体初速v0的增加而迅速增强;当v0>1 500m/s时,其防护效能高于同等重量的船用钢。

波纹管碰撞性能的试验研究

对波纹管碰撞性能进行了比较详细的试验研究。试验结果表明 :波纹管的吸能曲线比较平稳 ,是一个很好的汽车碰撞吸能部件 ;壁厚对于提高波纹管的吸能效果有很大的作用 ;动态冲击时的加速度比准静态时要高 ,且冲击速度越高 。

An improved theoretical procedure for the pore-size analysis of activated carbon by gas adsorption

Amorphous carbon materials play a vital role in adsorbed natural gas(ANG) storage. One of the key issues in the more prevalent use of ANG is the limited adsorption capacity, which is primarily determined by the porosity and surface characteristics of porous materials. To identify suitable adsorbents, we need a reliable computational tool for pore characterization and, subsequently, quantitative prediction of the adsorption behavior. Within the framework of adsorption integral equation(AIE), the pore-size distribution(PSD) is sensitive to the adopted theoretical models and numerical algorithms through isotherm fitting. In recent years, the classical density functional theory(DFT) has emerged as a common choice to describe adsorption isotherms for AIE kernel construction. However,rarely considered is the accuracy of the mean-field approximation(MFA) commonly used in commercial software. In this work, we calibrate four versions of DFT methods with grand canonical Monte Carlo(GCMC) molecular simulation for the adsorption of CH_4 and CO_2 gas in slit pores at 298 K with the pore width varying from 0.65 to 5.00 nm and pressure from 0.2 to 2.0 MPa. It is found that a weighted-density approximation proposed by Yu(WDA-Yu) is more accurate than MFA and other non-local DFT methods. In combination with the trapezoid discretization of AIE, the WDA-Yu method provides a faithful representation of experimental data, with the accuracy and stability improved by 90.0% and 91.2%, respectively, in comparison with the corresponding results from MFA for fitting CO_2 isotherms. In particular, those distributions in the feature pore width range(FPWR)are proved more representative for the pore-size analysis. The new theoretical procedure for pore characterization has also been tested with the methane adsorption capacity in seven activated carbon samples.

Adsorption mechanism of expanded graphite for oil and dyes

Expanded graphite （r-;G） shows higher adsorption capacity for oils than for dyes. To illustrate the different adsorption mechanism of EG for these pollutants, adsorption capacities of dyes and oil on EG were firstly studied. And then stepwise adsorption for oils was carried out with EG which has been saturated firstly by dyes, the difference between adsorbance of oil on EG was checked with deviation analysis. Scanning electronic microscopy （SEM） analysis was used to show structure difference of EG adsorbed different adsorbates. These used adsorbates were SD300 oil, basic fuchsine, Auramine lake yellow O and acid brilliant red 3B. The adsorption isotherm of dyes on EG is type 11 or type 1, and their equilibrium adsorbances are less than 1.0 g/g. While, adsorbance for SD300 oil can reach 104.5 g/g. Deviation analysis for stepwise adsorbances of oil shows no statistical significance. EG saturated firstly by dyes, still has an average adsorption capacity of 35 g/g for SD300 oil, and it does not change with the initial dyes concentration. SEM photos illustrate the adsorption of oil on EG is mainly filling, In the adsorption of dyes, there is severe breakage of the V-type pore and shrinkage of the particle. Kinetic difference is analyzed also.

Design and energy absorption enhancement of vehicle hull under high dynamic loads

V-shape hulls are widely used in peacekeeping efforts such as demining vehicles in order to deflect the blast energy and reduce the effects of mine blast. Blast resistant design and energy absorption enhancement of V-shape plates were carried out using finite element analysis package ABAQUS. Various geometries of V-shape plates with and without interlayer of materials like Al-foams and honeycomb were employed to analyze their effects on the deformation of the plate and applied stresses and strains. The results obtained show that application of metallic foams leads to better response of the plate and consequently results in more energy dissipation, less dame to vehicle and enhances crew survivability.

Synthesis of flowerlike nickel particles and their microwave absorbing properties

Two kinds of nickel particles with flower-like struc~＇es assembled with a number of nano-flakes were synthesized and the relationship of their morphology and microwave absorbing properties was studied. The electromagnetic parameters of these flower-like Ni were measured with vector network analyzer at 2-18 GHz frequency and the reflection losses （RL） with different sample thicknesses were calculated. The results indicate that the flower-like nickel-wax composites with the sample thickness less than 2 mm show excellent absorbing ability. This result is expected to play a guiding role in the preparation of the highly efficient absorber.

Modeling of Water Vapor Condensation by Using Computer Methodology

The excessive moisture has an adverse effect on the building materials structure. Most standard construction materials are characterized by porous structure, resulting in the ability to absorb water in liquid and gaseous phases in the inner pores. Under certain conditions, water fills the pores within the structure of building material and then moves back to its surrounding. Many technical studies have shown that monitoring the moisture transport is mainly based on experimental methods. This work is based on models of transport of moisture in building physics, i.e., the description of the moisture behaviour of building materials based on physical laws models （KRISCHER, KIESSL）. The aim of this work is to obtain the parameters of distribution of moisture for calculation capillary conductivity coefficient for practical using by means of non-destructive method. The authors have now developed all the software required to perform a boundary element analysis of problems in potential flow. The examples which the authors can analyse will, however, be restricted to homogenous domains.

Theoretical Study and Performance Analysis of an Adsorption Chiller

The thermodynamic cycle for an adsorption system is presented inp-T diagram. In order to investigate the performance of the adsorption system, a lumped parameter transient model of the chiller is developed, in order to predict the behaviors of the adsorption chiller system and find the influence of working conditions on its operation. For the working process of the main components of the system, including adsorber, condenser and evaporator, the coupled unsteady equations were set up for each stage. The model was then solved using stable numerical methods from EES （equation engineering solver）, and the performance of the adsorber and condenser/evaporator of the system was analyzed. The condensation, evaporation and adsorber temperature values as well as the adsorption ratio and desorption ratio were obtained as function of operating time. Also, the coefficient of performance was analyzed in function of the heat source temperature and the cooling source temperature.

Comparison of Phosphorus Sorption by Light-Weight Aggregates Produced in the United States

In this study, phosphorus(P) sorption of thirteen light-weight aggregates(LWAs) from USA was compared during batch equilibrium experiments in order to identify those materials which had the highest P sorption capacity for further study. Seven different levels of sorption activity were observed, which were broadly grouped into three categories—high performing, middle performing, and low performing aggregates. Chemical analysis of Ca, Al, Fe, and Mg was used to describe the differences between LWAs. There was a significant correlation between cation(especially Al, Ca, Fe, and Mg) content and P sorbed. Langmuir isotherms were used to describe P sorption maximum and binding affinity for four of the top five performing LWAs, Universal, Stalite "D", Stalite "Mix", and TXI.The fifth aggregate, Lehigh, exhibited more complex sorption, and was better described by the Freundlich isotherm. Universal had a mean P sorption at the highest concentration of 824 mg kg-1, well above its calculated sorption maximum(702 mg kg-1), and also had the highest binding affinity(1.1 L mg-1). This experiment suggests that the top performing LWA(Universal) may perform poorly in column and field studies due to observed precipitates, which could degrade constructed wetland performance. Other LWAs may exhibit superior field performance due to their high calculated sorption maxima. In general, these results highlight the importance of batch experiments as a first step in identifying materials suitable for column and field experiments.

Heat Transfer Analysis of an Elevated Linear Absorber with Trapezoidal Cavity in the Linear Fresnel Reflector Solar Concentrator System

This paper describes various aspects of the design methodology and heat transfer calculations for an elevated linear absorber. The absorber is a part of the linear Fresnel reflector solar concentrator system, in which hot fluid is generated. The design of the absorber is an inverted trapezoidal air cavity with a glass cover enclosing a multi tube absorber. In a trapezoidal cavity absorber, a set of linear multi tube absorber with plate(named as "plane surface") and without plate(named as "tube surface") underneath are considered. An analytical simulation is done for different gaps between the tubes and for different depths of the cavity. A better design of the absorber is found out to maximize the heat transfer rate supplied to the absorber tube fluid. Also, the experimentally obtained overall heat loss coefficients are compared with the analytical values for the considered arrangements of absorber set up and results are discussed in details.

Performance analysis of the silicon waveguide-based wavelength converter

The conversion efficiency and noise figure (NF) of the silicon-on-insulator (SOI) waveguide-based wavelength converter are investigated with the coupled equations. The effects of the pump power, the nonlinear absorption and the waveguide length on the conversion efficiency and noise figure are discussed. The conversion efficiency decreases with the increasing pump power and the noise figure is degraded due to the two-photon absorption (TPA) and the TPA-induced free-carrier absorption (FCA) at the higher pump power. With the increasing of the free carrier lifetime, the conversion efficiency will decrease and the noise figure will increase accordingly. The optimal waveguide length depends on the pump power and the free carrier lifetime. In practical applications, the high conversion efficiency and low noise figure can be achieved by choosing suitable parameters of the silicon waveguide.