In-situ thermal Raman mapping and stress analysis of CNT/CF/epoxy interfaces

A study of the interfacial behavior and internal thermal stress distribution in fiber-reinforced composites is essential to assess their performance and reliability.CNT/carbon fiber(CF)hybrid fibers were constructed using electrophoretic deposition.The interfacial properties of CF/epoxy and CNT/CF/epoxy composites were statistically investigated and compared using in-situ thermal Raman mapping by dispersing CNTs as a Raman sensing medium(CNT_(R))in a resin.The associated local thermal stress changes can be simulated by capturing the G'band position distribution of CNT_(R) in the epoxy at different temperatures.It was found that the G'band shifted to lower positions with increasing temperature,reaching a maximum difference of 2.43 cm^(−1) at 100℃.The interfacial bonding between CNT/CF and the matrix and the stress distribution and changes during heat treatment(20-100℃)were investig-ated in detail.This work is important for studying thermal stress in fiber-reinforced composites by in-situ thermal Raman mapping technology.

An Effective 3D-CFD Methodology for the Complementary Virtual Development of Alternative Fuels and Engine Concepts

With the aim of reducing the cost of developing internal combustion engines,while at the same time investigating different geometries,layouts and fuels,3D-CFD-CHT simulations represent an indispensable part for the development of new technologies.These tools are increasingly used by manufacturers,as a screening process before building the first prototype.This paper presents an innovative methodology for virtual engine development.The 3D-CFD tool QuickSim,developed at FKFS,allows both a significant reduction in computation time and an extension of the simulated domain for complete engine systems.This is possible thanks to a combination of coarse meshes and self-developed internal combustion engine models,which simultaneously ensure high predictability.The present work demonstrates the capabilities of this innovative methodology for the design and optimization of different engines and fuels with the goal of achieving the highest possible combustion efficiencies and pollutant reductions.The analysis focuses on the influence of different fuels such as hydrogen,methanol,synthetic gasolines and methane on different engine geometries,in combination with suitable injection and ignition systems,including passive and active pre-chambers.Lean operations as well as knock reduction are discussed,particularly for methane and hydrogen injection.Finally,it is shown how depending on the chosen fuel,an appropriate ad-hoc engine layout can be designed to increase the indicated efficiency of the respective engines.

Ultimate flexural strength of normal section of FRP-confined RC circular columns

Numerical analysis is carried out to study the sectional properties of the fiber-reinforced polymer（FRP）-confined reinforced concrete（RC）circular columns. The axial load ratio, the FRP confinement ratio and the longitudinal reinforcement characteristic value are the three main parameters that can influence the neutral axis depth when concrete compression strain reaches an ultimate value. The formula for computing the central angle θ, corresponding to the compression zone, is established according to the data regression of the numerical analysis results. The numerical analysis results demonstrate that the concrete stress enhancement from transverse confinement and strain hardening of the longitudinal reinforcement can cause a much greater flexural strength than that defined by the design code. Based on the analytical studies and the test results of 36 large scale columns, the formula to calculate the flexural strength when columns fail under seismic loading is proposed, and the calculated results agree well with the test results. Finally, parametric studies are conducted on a typical column with different axial load ratios, longitudinal reinforcement characteristic value and FRP confinement ratios. Analysis of the results shows that the calculated flexural strength can be increased by 50% compared to that of unconfined columns defined by the code.

Effects of different modifiers on the properties of wood-polymer composites

Wood-polymer composites (WPC) were prepared from wood fiber and four kinds of plastics such as PE, PS, ABS, and SAN. The effects of different modifiers on the mechanical properties of the composites were studied. The results showed modifiers could raise the bonding strength of wood fiber with polymer and improve the mechanical properties of the composites. Different modifiers had different effects on the properties of wood-polymer composites, and comparatively the modifier of isocyanate produced a better result. Wood-polymer composite takes not only the advantages of both wood fiber and polymer, but waterproof, dimensional stability and dynamic strength are also significantly improved. Key word Wood fiber - Thermoplastic polyester - Wood-polymer composites - Modifier - Mechanical properties CLC number TB332 Document code A Foundation item: This study was supported by the Harbin Technology Tackle Key Plan (Development Research of Wood-Polymer Composites with High Wood Matrix) and by Heilongjing Nature Science Fund (Composite Mechanism Study of the Wood Polymer).Biography: XU Min (1963-), Female, Associate professor in Material Science and Engineering College, Northeast Forestry University, Harbin 150040, P. R. China.Responsible editor: Chai Ruihai

Sintering formation of oriented linear cutting copper fibers

The formation mechanism of oriented linear cutting copper sintered felt was analyzed. The influences of sintering temperature, sintering atmosphere and sintering time on the sintering formation were investigated. And the tensile mechanical properties of sintering fibers under different sintering conditions were also analyzed. The results indicate that the formation of sintered necks in the contacted area due to the materials migration of microstructures on the surfaces of fibers promotes the tight connection of oriented linear cutting copper fibers. It is also found that both sintering temperature and sintering atmosphere show important effects on the sintering formation while the influence of sintering time is not so obvious. Sintering at 800 °C for 60 min under low temperature reduction can produce sintered necks to make fibers tightly connect together and maintain the coarse microstructure on the surface of fibers, and the best tensile mechanical property can be obtained as well.

Rheological and mechanical properties of wood fiber-PP/PE blend composites

For evaluation of the rheological and mechanical properties of highly filled wood plastic composites （WPCs）, polypropylene/polyethylene （PP/PE） blends were grafted with maleic anhydride （MAH） to enhance the interfacial adhesion between wood fiber and matrix. WPCs were prepared from wood fiber up to 60 wt.% and modified PP/PE was blended by extrusion. The rheological properties were studied by using dynamic measurement. According to the strain sweep test, the linear viscoelastic region of composites in the melt was determined. The result showed that the storage modulus was independent of the strain at low strain region （〈0.1%）. The frequency sweep resuits indicated that all composites exhibited shear thinning behavior, and both the storage modulus and complex viscosity of MAH modified composites were decreased comparing to those unmodified. Flexural properties and impact strength of the prepared WPCs were measured according to the relevant standard specifications. The flexural and impact strength of the manufactured composites significantly increased and reached a maximum when MAH dosage was 1.0 wt%, whereas the flexural modulus after an initial decreased, also increased with MAH dosage. The increase in mechanical properties indicated that the presence of anhydride groups enhanced the interracial adhesion between wood fiber and PP/PE blends.

Thermodynamics and kinetics of adsorption for heavy metal ions from aqueous solutions onto surface amino-bacterial cellulose

Amino-bacterial cellulose（amino-BC） was prepared by chemical modification of bacterial cellulose（BC）.The adsorption characteristics and mechanism of amino-BC were studied.The results show that adsorption data can be fitted well by Langmuir equation and the pseudo-second order kinetics,indicating that the adsorption of amino-BC would obey monolayer molecule adsorption and the main action was chemisorption.Meanwhile,the adsorption process was studied by the Elovich equation and the intra-particle diffusion model,indicating that the absorption characteristics of metal ions on amino-BC is controlled by both film diffusion and particle diffusion.The increase of reaction temperature will accelerate the adsorbing rate because of endothermic reaction.

Three-dimensional numerical simulation of the flow past a circular cylinder based on LES method

The hydrodynamic characteristics of a rigid, single, circular cylinder in a three dimensional, incompressible, uniform cross flow were calculated using the large-eddy simulation method of CFX5. Solutions to the three dimensional N-S equations were obtained by the finite volume method. The focus of this numerical simulation was to research the characteristics of pressure distribution （drag and litt forces） and vortex tubes at high Reynolds numbers. The results of the calculations showed that the forces at every section in the spanwise direction of the cylinder were symmetrical about the middle section and smaller than the forces calculated in two dimensional cases. Moreover, the flow around the cylinder obviously presents three dimensional characteristics.

Thermodynamics analysis of Ni^(2+)-C_2H_8N_2- C_2O_4^(2-)-H_2O system and preparation of Ni microfiber

According to the principles of simultaneous equilibrium and mass equilibrium, the thermodynamics model of the precipitation-coordination equilibrium of Ni2＋-C2H8N2- 2-2 4C O -H2O system was established, and calculation for the relationships between concentration of each substance in solution and parameters was carried out, including pH value, concentrations of ethylenediamine and oxalate by MATLAB program. The results show that Ni exists as Ni2＋and [Ni（C2O4）n]2-2n mainly at pH〈1 and pH=1-6, respectively. When pH〉6, the complex between Ni2＋and ethylenediamine is predominant. The precursor of Ni microfiber was prepared by an oxalate precipitation process using ethylenediamine as a coordination agent, and the role of ethylenediamine in the growth of the precursor fiber was discussed. The Ni microfiber can be obtained by a thermal decomposition-reduction process of the precursor in N2 and H2 mixed atmosphere. The diameters and aspect ratios of the obtained Ni microfibers are 0.2-1 μm and 20-30, respectively.

MICRO MECHANICAL ANALYSIS OF 3-D WOVEN COMPOSITES

A micro mechanical model is carried out to predict micro stresses and macro elastic properties of 3-D woven composites. A unit cell is composed of two phases. One is fiber yarn and the other is resin or fiber yarn in transverse. The additional shearing introduced by bending of fiber yarn is considered. The method to determine the microstructure is also discussed. This model is applied to the analysis of a 3-D woven graphite/epoxy composite. Micro stresses of the cell are studied, and then macro modulus is obtained by employing the average method. The predictions agree well with experimental results.

AIoT与AIOps赋能DCIM

分析了DCIM发展的现状和困境,指出AIoT+AIOps技术的必要性,通过诠释AIoT和AIOps的技术内涵,引出力维在AIoT+AIOps方面的技术实践。对于改善监控核心问题的能力,打造更高效、智能的数据中心,提高了运维效率,具有重要意义。

Extrapolated Tikhonov method and inversion of 3D density images of gravity data

Tikhonov regularization（TR） method has played a very important role in the gravity data and magnetic data process. In this paper, the Tikhonov regularization method with respect to the inversion of gravity data is discussed. and the extrapolated TR method（EXTR） is introduced to improve the fitting error. Furthermore, the effect of the parameters in the EXTR method on the fitting error, number of iterations, and inversion results are discussed in details. The computation results using a synthetic model with the same and different densities indicated that. compared with the TR method, the EXTR method not only achieves the a priori fitting error level set by the interpreter but also increases the fitting precision, although it increases the computation time and number of iterations. And the EXTR inversion results are more compact than the TR inversion results, which are more divergent. The range of the inversion data is closer to the default range of the model parameters, and the model features and default model density distribution agree well.

Contact Problem in Decagonal Two-Dimensional Quasicrystal

As a new structure of solid matter quasicrystal brings profound new ideas to the traditional condensed matter physics, its elastic equations are more complicated than that of traditional crystal. A contact problem of decagonal two? dimensional quasicrystal material under the action of a rigid flat die is solved satisfactorily by introducing displacement function and using Fourier analysis and dual integral equations theory, and the analytical expressions of stress and displacement fields of the contact problem are achieved. The results show that if the contact displacement is a constant in the contact zone, the vertical contact stress has order -1/2 singularity on the edge of contact zone, which provides the important mechanics parameter for contact deformation of the quasicrystal.

Improvement of Cellulase Producing Capacity of Aspergillus niger by Ultraviolet Mutation

[Objective] The research aimed to breed the high-yield production strain of cellulase.[Method] Aspergillus niger was used as the starting strain,and a high-yield production strain of cellulase was selected after UV mutation treatment.[Result] Under the suitable condition,the strain 2（15） with the highest CMC production capacity was selected,which nearly increased 50% than that of the starting strain.[Conclusion] The research provided the foundation for its appliation in the feed production in the future.

Influence of FeCrAl fiber on microstructure and mechanical properties of FeCrAl(f)/HA composites

FeCrAl fiber-reinforced hydroxyapatite（HA） biocomposites（FeCrAl（f）/HA） were fabricated by the hot pressing technique.The metallographic microscopy,X-ray diffractometry,scanning electron microscopy（SEM） and energy dispersive spectroscopy（EDS） were used to observe and analyze the microstructure and composition of FeCrAl（f）/HA composites,respectively.The mechanical properties of FeCrAl（f）/HA composites were measured by the three-point-bending test.The results show that the composite can be reinforced by FeCrAl fiber and enhanced gradually,and then declined with the increase of the content of FeCrAl fiber（0-11%,volume fraction） in the whole range of experiments.Both the HA matrix and FeCrAl fiber integrate very tightly and bit into each other very deeply and counter-diffusion takes place to some extent at two-phase interface.The optimum parameters of FeCrAl（f）/HA composite are diameter of 22 μm,length of 1-2 mm and of volume faction of about 7% for FeCrAl fibers.

INCLINED LAMINAL COMBINATION MODEL OF 3D BRAIDED COMPOSITES

As an advanced composite material, the 3D braided composite has received more and more attention in foreign countries. However, it has received less attention in China. The geometric unit cell which can describe the basic structure and the relationship between the braiding angle and geometric parameters of the fabric and fiber volume ratio are given in this paper based on two 3D braiding processes, namely, the four-step and the twostep ones. Several existing mechanical models to predict groperties of the 3D braided comPOsites are discussed and their shortcomings are pointed out herein. Then a new model called the inclined laminal combination model is proposed, which is based on the classical laminated plate theory and can predict the basic mechanical behavior of the two 3D braided composites with four-step or two-step braid. In the model, each yarn in the unit cell is regarded as an inclined laminate and then a 3D analysis is performed. It is found that the predicted mechanical properties of the 3D braided composites by the proposed model are compared well with the experimental data.

THE CALCULATION OF THE VOLUME INTEGRAL IN BEM OF TWO DIMENSIONAL ELASTICITY

In this paper, a method of transforming volume integrals to boundary integrals is given for complicated loadings such as a i(y)x i and b i(x)y i . In the present method the volume integrals are approximately transformed to boundary integrals.

Caustics study of the effect of glass fibres on dynamic fracture of hardened cement paste

The reflected optical caustics method is applied to study dynamic fracture problems in hardened cement paste. First both the unreinforced cement paste and the glass fibres reinforced cement paste specimens were fabricated and the reflective coating on the surface of the specimen was prepared. Secondly the crack path and the shadow spot patterns during the crack propagation process for the two specimens were recorded by using a multi-spark high speed camera.Thirdly some dynamic parameters of two cement paste specimens including crack onset time the dynamic stress intensity factor and crack growth velocity were determined and analyzed comparatively.This indicates that the glass fibres can improve the fracture resistance and delay fracture time.These results will play an important role in evaluating the dynamic fracture properties of cement paste.

Grain refinement of Mg-Al alloys by optimization of process parameters based on three-dimensional finite element modeling of roll casting

To study the influence of roll casting process parameters on temperature and thermal-stress fields for the AZ31 magnesium alloy sheets,three-dimensional geometric and 3D finite element models for roll casting were established based on the symmetry of roll casting by ANSYS software.Meshing method and smart-sizing algorithm were used to divide finite element mesh in ANSYS software.A series of researches on the temperature and stress distributions during solidification process with different process parameters were done by 3D finite element method.The temperatures of both the liquid-solid two-phase zone and liquid phase zone were elevated with increasing pouring temperature.With the heat transfer coefficient increasing,the two-phase region for liquid-solid becomes smaller.With the pouring temperature increasing and the increase of casting speed,the length of two-phase zone rises.The optimized of process parameters（casting speed 2 m/min,pouring temperature 640 ℃ and heat transfer coefficient 15 kW/（m2·℃） with the water pouring at roller exit was used to produce magnesium alloy AZ31 sheet,and equiaxed grains with the average grain size of 50 μm were achieved after roll casting.The simulation results give better understanding of the temperature variation in phase transformation zone and the formation mechanism of hot cracks in plates during roll casting and help to design the optimized process parameters of roll casting for Mg alloy.