MHSS压缩有效力学性能研究

金属空心球结构(Metallic hollow sphere structure,MHSS)是一种新型的超轻多孔金属材料。利用ANSYS有限元分析软件模拟了薄壁金属空心球的压缩过程,采用非线性和瞬态分析方法得出了其名义应力-应变曲线,与实验曲线进行对比分析发现两条曲线较为吻合。对3种不同堆积模式的金属空心球结构进行了压缩数值模拟分析,得出了其压缩的有效屈服极限和有效弹性模量等力学性能。通过研究材料中单球的受力状态,分析了不同堆积模式材料力学性能出现差异的原因,其理论预测结果与数值模拟结果具有相同的规律。

强韧支架用丝素蛋白基生物墨水及其3D打印支架模拟软件的开发

基于丝素蛋白(SF)和有限元分析方法,开发了一种强韧支架用丝素蛋白基生物墨水及其3D打印支架压缩性能模拟软件。表征了墨水的可打印性及对应水凝胶和3D打印支架的力学性能,评估了相关打印支架的细胞相容性。基于所述丝素蛋白基生物墨水,设计并制备了不同高度和孔隙率的3D打印支架,利用所开发软件和电子万能材料试验机对打印支架的压缩性能进行了模拟预测和实测对比。结果表明:该墨水可打印性佳,对应支架强度高韧性好、细胞相容性好。所开发软件操作简便,具有3D打印支架建模、模型压缩力学性能预测以及指导3D打印支架快速制备等功能。

一种低造价叠层橡胶隔震支座的试验及模拟研究

提出了一种适用于村镇民居的新型低造价隔震支座,即采用低成本的3240环氧树脂板材作为叠层橡胶隔震支座的加劲层。分别对3240板材和隔震支座进行了力学性能试验,分析了竖向刚度与竖向面压的关系、水平刚度随不同竖向面压或剪应变的变化规律以及支座的力学和变形性能;对隔震支座进行压缩和剪压数值模拟,探究支座的应力分布规律以及翘曲现象对支座性能的影响。研究结果表明:3240隔震支座具有良好的力学和变形性能,支座的竖向刚度随竖向面压增大而减小,水平刚度随剪应变增大而减小;竖向压缩模拟时,支座最大竖向应力和最大水平应力均为竖向面压2倍左右;翘曲会使支座产生较大水平应力且降低支座水平刚度,工程中建议采用螺栓连接避免支座翘曲破环。

Molecular dynamics study on temperature and strain rate dependences of mechanical tensile properties of ultrathin nickel nanowires

Based on the EAM potential, a molecular dynamics study on the tensile properties of ultrathin nickel nanowires in the （100〉 orientation with diameters of 3.94, 4.95 and 5.99 nm was presented at different temperatures and strain rates. The temperature and strain rate dependences of tensile properties were investigated. The simulation results show that the elastic modulus and the yield strength are gradually decreasing with the increase of temperature, while with the increase of the strain rate, the stress--strain curves fluctuate more intensely and the ultrathin nickel nanowires rupture at one smaller and smaller strain. At an ideal temperature of 0.01 K, the yield strength of the nanowires drops rapidly with the increase of strain rate, and at other temperatures the strain rate has a little influence on the elastic modulus and the yield strength. Finally, the effects of size on the tensile properties of ultrathin nickel nanowires were briefly discussed.

A novel method to improve interfacial bonding of compound squeeze cast Al/Al-Cu macrocomposite bimetals:Simulation and experimental studies

A facile and innovative method to improve bonding between the two parts of compound squeeze cast Al/Al-4.5 wt.%Cu macrocomposite bimetals was developed and its effects on microstructure and mechanical properties of the bimetal were investigated.A special concentric groove pattern was machined on the top surface of the insert(squeeze cast Al-4.5 wt.%Cu) and its effects on heat transfer,solidification and distribution of generated stresses along the interface region of the bimetal components were simulated using ProCAST and ANSYS softwares and experimentally verified. Simulation results indicated complete melting of the tips of the surface grooves and local generation of large stress gradient fields along the interface. These are believed to result in rupture of the insert interfacial aluminum oxide layer facilitating diffusion bonding of the bimetal components. Microstructural evaluations confirmed formation of an evident transition zone along the interface region of the bimetal. Average thickness of the transition zone and tensile strength of the bimetal were significantly increased to about 375 μm and 54 MPa, respectively, by applying the surface pattern.The proposed method is an affordable and promising approach for compound squeeze casting of Al-Al macrocomposite bimetals without resort to any prior cost and time intensive chemical or coating treatments of the solid insert.

Feasibility of using recycled CRT funnel glass as partial replacement of high density magnetite sand in radiation shielding concrete

The recycled cathode ray tube(CRT)funnel glass was used as replacement of magnetite sand in the concrete,and its mass replacement rates were 0,20%,40%and 60%,respectively.The flowability,apparent density and mechanical properties of the radiation shielding concrete were investigated,while itsγ-ray radiation shielding parameters such as linear and mass attenuation coefficients(μandμm,respectively),thickness values of half-value layer(hHVL)and tenth-value layer(hTVL)were obtained by theoretical calculation,experiment and Monte.Carlo N-Particle(MCNP)simulation code.The experimental results show that the flowability of the concrete increases significantly,whilst its apparent density,compressive strength and static elastic modulus decrease slightly.The calculated,simulated and experimentalμm,μ,hHVL and hTVL values of all concrete samples are very consistent at the sameγ-ray photon energy,and it is feasible to use MCNP code to simulateγ-ray radiation shielding parameters of materials.The calculated results show that in a wide range ofγ-ray photon energy,theμm value of the concrete with CRT funnel glass replacing magnetite sand is improved effectively,and its radiation shielding performances are the same as those of the control concrete(M.1).By comprehensively comparing the flowability,mechanical properties andγ-ray radiation shielding properties,the concrete samples with 20%.40%funnel glass as fine aggregate have good performances.

Stability control of a deep shaft insert

The deterioration of a deep shaft insert at the Xing'an Coal Mine was analyzed by studying the physical and mechanical properties of the rock located at key positions relative to the shaft. Factors that influence shaft stability were obtained. The numerical simulation program FLAC3D was used to simulate the destruction of the deep shaft insert. Two different support methods were analyzed by simulation. The simulations demonstrate that a single stiffness support is inappropriate for this shaft insert. The appropriate support method is an integrated coupling method of rigid and flexible supports. The flexible support is applied first and then the rigid support is second. Engineering practice in the Xing'an Coal Mine shows that this technology can effectively control deep-shaft insert deterioration. This support approach provides an important direction for future project design and construction, as well.

Simulation of Morphologies and Mechanical Properties of A/B Polymer Blend Film

The effects of blend composition and micro-phase structure on the mechanical behavior of A/B polymer blend film are studied by coupling the Monte Carlo(MC) simulation of morphology with the lattice spring model(LSM) of micro mechanics of materials.The MC method with bond length fluctuation and cavity diffusion algorithm on cubic lattice is adopted to simulate the micro-phase structure of A/B polymer blend.The information of morphology and structure is then inputted to the LSM composed of a three-dimensional network of springs to obtain the mechanical properties of polymer blend film.Simulated results show that the mechanical response is mainly affected by the density and the composition of polymer blend film through the morphology transition.When a force is applied on the outer boundary of polymer blend film,the vicinity of the inner cavities experiences higher stresses and strains responsible for the onset of crack propagation and the premature failure of the entire system.

Experimental and Molecular Dynamics Simulations for Investigating the Effect of FattyAcid and Its Derivatives on Low Sulfur Diesel Lubricity

In this work,fatty acid and its derivatives were adopted as lubricity additives for low sulfur diesel.Tribological evaluation obtained from the High-Frequency Reciprocating Rig(HFRR)apparatus showed that the lubricating performance of the additives increased in the following order:stearic acid>glycol monopalmitate>stearyl alcohol>ethyl palmitate>cetyl ethyl ether.The adsorption behavior of the additives on Fe(110)surface and Fe2O3(001)surface was investigated by molecular dynamics(MD)simulations to verify their lubricity performance.The results suggested that adsorption energies of the additives on Fe(110)surface are determined by the van der Waals forces,while adsorptions on Fe2O3(001)surface are significantly attributed to the electrostatic attractive forces.Higher values of adsorption energy of the additives on Fe2O3(001)surface indicate that the additive has more efficient lubricity enhancing properties.

Complete Modeling for Systems of a Marine Diesel Engine

This paper presents a simulator model of a marine diesel engine based on physical, semi-physical, mathematical and thermodynamic equations, which allows fast predictive simulations The whole engine system is divided into several functional blocks： cooling, lubrication, air, injection, combustion and emissions. The sub-models and dynamic characteristics of individual blocks are established according to engine working principles equations and experimental data collected from a marine diesel engine test bench for SIMB Company under the reference 6M26SRP1. The overall engine system dynamics is expressed as a set of simultaneous algebraic and differential equations using sub-blocks and S-Functions of Matlab/Simulink. The simulation of this model, implemented on Matlab/Simulink has been validated and can be used to obtain engine performance, pressure, temperature, efficiency, heat release, crank angle, fuel rate, emissions at different sub-blocks. The simulator will be used, in future work, to study the engine performance in faulty conditions, and can be used to assist marine engineers in fault diagnosis and estimation （FDI） as well as designers to predict the behavior of the cooling system, lubrication system, injection system, combustion, emissions, in order to optimize the dimensions of different components. This program is a platform for fault simulator, to investigate the impact on sub-blocks engine＇s output of changing values for faults parameters such as： faulty fuel injector, leaky cylinder, worn fuel pump, broken piston rings, a dirty turbocharger, dirty air filter, dirty air cooler, air leakage, water leakage, oil leakage and contamination, fouling of heat exchanger, pumps wear, failure of injectors （and many others）.

A Comparative Study on Hydrodynamic Performance of Double Deflector Rectangular Cambered Otter Board

In the present work,the hydrodynamic performance of the double deflector rectangular cambered otter board was studied using wind tunnel experiment,flume tank experiment and numerical simulation.Results showed that the otter board had a good hydrodynamic performance with the maximum lift-to-drag ratio(K_(MAX) = 3.70).The flow separation occurred when the angle of attack(AOA) was at 45?,which revealed that the double deflector structure of the otter board can delay the flow separation.Numerical simulation results showed a good agreement with experiment ones,and could predict the critical AOA,which showed that it can be used to study the hydrodynamic performance of the otter board with the advantage of flow visualization.However,the drag coefficient in flume tank was much higher than that in wind tunnel,which resulted in a lower lift-to-drag ratio.These may be due to different fluid media between flume tank and wind tunnel,which result in the big difference of the vortexes around the otter board.Given the otter boards are operated in water,it was suggested to apply both flume tank experiment and numerical simulation to study the hydrodynamic performance of otter board.

Microstructure and mechanical properties of friction stir processed TA5 alloy

Ultra-fine grained TA5 titanium alloy was fabricated by friction stir processing(FSP).Temperature distribution and material flow were simulated by the coupled Euler−Lagrange(CEL)method.The microstructure and mechanical properties of TA5 alloy were characterized by optical and scanning electron microscope,Vickers hardness,and tensile tests.The processed alloy was composed of ultra-fine grained and equiaxed grains due to dynamic recrystallization.The microstructure recrystallized through grain boundary rotation and dislocation accumulation.The grain size reached the minimum on the advancing side of the stir zone with the highest grain misorientation.Ultimate tensile strength was promoted to over 830 MPa after FSP at a rotating speed of 200 r/min,whereas elongation varied a little.The specimens all fractured on the retreating side of the stir zone and smaller dimples were depicted from the fracture morphologies of FSP specimens.

Effects of tensile temperatures on phase transformations in zirconium by molecular dynamics simulations

The effects of tensile temperatures ranging from 100 K to 900 K on the phase transition of hexagonal close-packed(HCP)zirconium were investigated by molecular dynamics simulations,which were combined with experimental observation under high resolution transmission electron microscopy.The results show that externally applied loading first induced the HCP to body-centered cubic(BCC)phase transition in the Pitsch-Schrader(PS)orientation relationship(OR).Then,the face-centered cubic(FCC)structure transformed from the BCC phase in the Bain path.However,the HCP-to-BCC transition was incomplete at 100 K and 300 K,resulting in a prismatic-type OR between the FCC and original HCP phase.Additionally,at the temperature ranging from 100 K to 600 K,the inverse BCC-to-HCP transition occurred locally following other variants of the PS OR,resulting in a basal-type relation between the newly generated HCP and FCC phases.A higher tensile temperature promoted the amount of FCC phase transforming into the BCC phase when the strain exceeded 45%.Besides,the crystal stretched at lower temperatures exhibits relatively higher strength but by the compromise of plasticity.This study reveals the deformation mechanisms in HCP-Zr at different temperatures,which may provide a better understanding of the deformation mechanism of zirconium alloys under different application environments.

A coupled DEM and LBM model for simulation of outbursts of coal and gas

An outburst of coal and gas is a major hazard in underground coal mining. It is generally accepted that an outburst occurs when certain conditions of stress, coal gassiness and physical-mechanical properties of coal are met. Outbursting is recognized as a two-step process, i.e., initiation and development. In this paper, we present a fully-coupled solid and fluid code to model the entire process of an outburst. The deformation, failure and fracture of solid （coal） are modeled with the discrete element method, and the flow of fluid （gas and water） such as free flow and Darcy flow are modeled with the lattice Boltzmann method. These two methods are coupled in a two-way process, i.e., the solid part provides a moving boundary condition and transfers momentum to the fluid, while the fluid exerts a dragging force upon the solid. Gas desorption from coal occurs at the solid-fluid boundary, and gas diffusion is implemented in the solid code where particles are assumed to be porous. A simple 2D example to simulate the process of an outburst with the model is also presented in this paper to demonstrate the capability of the coupled model.

A Simulation Software for the Prediction of Thermal and Mechanical Properties of Wood Plastic Composites

Modelling and simulation has become an important tool in research and development. Simulation models are used to develop better understanding of the internal properties and impact of various parameters on the final quality of the product or process. Simulation model reduces the number of experiments and saves the wastage of material, time and money and are widely used in automobile industry, aircrafts manufacturing, process engineering, training for military, health care sector and many more. Wood Plastic Composite （WPC） is a bio-composite made by mixing wood fibers and plastic granules together at high temperature by compression molding or injection molding. A large quantity of WPC is rejected due to poor quality and low mechanical strength. There is a need to improve the understanding of the wood plastic composites, with both theoretical and experimental analysis. The impact of various parameters and processing conditions on the final product is not known to the industry people, due to less simulation models in this field. A new simulation software WPC Soft is developed to predict the mechanical and thermal properties of WPC. The software can predict the mechanical and thermal properties of WPC. The simulation results were validated with the experimental results and it was observed that the predicted values are quite close to the experimental values and with the further refining of the model, prediction can be further improved. The present simulation software can be easily used by the industry people and it requires very little knowledge of computers or modeling for its operation.

A stability study of goaf based on mechanical properties degradation of rock caused by rheological and disturbing loads

Based on the classical static theory and static numerical simulation,the static method could not accurately reflect the stability of goaf where the rocks on the pillar and roof are influenced by Theological and blasting disturbance for a long time.According to the test from the site,an experimental study was made in Theological and dynamic disturbance.After that,on the basis of variable rock mechanics parameters from the experimental data,numerical simulation was used to analyze the vertical stress distribution of goaf,vertical displacement and plastic area of roof in the "deterioration" caused by Theological and blasting,which shows that the mechanics properties of the rock were greatly influenced by Theological,and dynamic disturbance.The results of the experimental study and numerical simulation show that the mechanics properties of rock are greatly influenced by Theological and dynamic disturbance.As a result,the stability of goaf is greatly reduced.Finally,by comparing golf monitoring results with the analysis of theoretical calculation,it was found that the results were approximately the same,which testifies the reliability of the method.This method provides a new way of studying the stability of goaf as well as laying a basic foundation for future safety management.

Energy conserving effects of dividing wall column

The energy-conserving performance of dividing wall column(DWC) is discussed in this paper. The heat transfer through the dividing wall is considered and the results are compared with that of common heat insulation dividing wall column(HIDWC). Based on the thermodynamic analysis of heat transfer dividing wall column(HTDWC) and HIDWC, both computer simulation and experiments are employed to analyze the energyconserving situation. Mixtures of n-hexane, n-heptane and n-octane are chosen as the example for separation.The results show that the energy consumption of HTDWC is 50.3% less than that of conventional distillation column, while it is 46.4% less than that of HIDWC. It indicates that DWC is efficient on separating threecomponent mixtures and HTDWC can save more energy than HIDWC. Thus it is necessary to consider the heat transfer while applying DWC to industry.

Geometry effect on mechanical properties of woven fabric composites

The effects of geometry on mechanical properties in woven fabric composites were explored. Two types of composites, including one-layered and two-layered composites, were designed and studied. For one-layered composites, inter-strand gap effects on the mechanical properties were studied, while three cases of geometries with inter-strand gaps in two-layered composites were evaluated. A woven fiber micromechanics analytical model called MESOTEX was employed for theoretical simulation. The predicted results show that the inter-strand gap and simple variation of the strand positions in a repeating unit cell significantly affect the mechanical properties of woven fabric composites.

Effects of circumferential configuration concerning splitter blade on the aerodynamic performance in a transonic axial fan

For a certain type of transonic axial fan, the flow field of a fan rotor with splitter blade was computed by numerical simulation, and the shape of the rotor was modified. The effects of different circumferential distributions concerning the splitter cascades upon the aerodynamic performance were investigated. The studies show that the optimum splitter cascade is not very close to the suction side of main blade. The load between the main blade and the splitter blade can be soundly distributed in terms of the adjustment of circumferential position of the splitter blade. The best aerodynamic performance can be successfully obtained according to the optimum shape of the expanding fluid channel reasonably formed by the splitter blade and the main blade.

THE MEASUREMENT AND STUDY OF BLASTING VIBRATION AFFECTING IN SITU CAST CONCRETE LINING OF VERTICAL SHAFT

Vertical shaft is main form of drivage in deep mineral depoist. They also serve as the entrance into and the exit from the underground mine. The main problems in shaft and tunnel engineering is to solve the contradiction between drivage and lining. The measurement of blasting vibration affecting concrete lining strength of vertical shaft is carried out in experiment and theory in this paper.