Applied Mechanics and Materials Vol. 455

Abstract: Foam glass was prepared by boron mud, broken glass, foaming agents and fluxes. The appropriate foaming temperature and foaming time were got by sintering parameter optimization. The effects of preparation conditions on propertis of the foam glass for soilless cultivation matrix were investigated. The results show that under the optimum preparation conditions (the foaming temperature is 800 °C and foaming time is 40 min), the formula for boron mud/broken glass: Borax: Sodium nitrate: Calcium carbonate is 35/50: 5:7:3, the bulk density is 247 kg/m3, the open porosity is 70%, the water absorption rate is 202.3%, the pH value of soak solution keeps at about 6.5 with the increase of immersion time. All of these will meet the application requirement of soilless cultivation.

Abstract: Caries progress might be controlled when collagen matrix could be preserved after demineralization. The aim of this study was to investigate the effect of EGCG, a major polyphenol of green tea, on changes in loss of dry weight or solubilization of collagen from demineralized dentin sections. Dentin sections (1mm×5mm×5mm) were completely exposed to the acetic acid solution to form dentine caries. After baseline measurements of dry mass, the samples were divided into 2 groups and incubated at 37°C in either media containing EGCG or artificial saliva only for 24h, 3 days, 1 week, 2 week and 3 weeks. Following hydrolyzed with HCl, hydroxyproline (HOP) as an index of solubilization of collagen was analysed quantitatively. Both the storage medium and the storage time showed significant effects on mass loss and HOP release (p < 0.05). The incubation in EGCG resulted in relatively rapid and significant (p < 0.05) decrease in the amounts of mass loss. The HOP content of the experimental media also increased with incubation time but was significantly lower (p < 0.05) than in the control artificial saliva medium. It can be concluded that EGCG can inhibit collagen degradation and affects the further demineralization in dentin matrix, which consequently inhibits the advanced dentine caries.

Abstract: This paper mainly states that under the PID program control, syntactic foam cantilever beam and piezoelectric composite cantilever beam which are studied with the momentary force and the alternating force signal, in the effective of active damping. The vibration stopping time changes under the momentary force and the amplitude changes under the alternating force signal. Comparing under the same initial amplitude, the amplitude changes of syntactic foam cantilever beam and piezoelectric composite cantilever beam under the active damping.

Abstract: Bearing steel tube blanking has application potential in bearing ring manufacturing. However, compared with sheet blanking, tube blanking has been rarely studied yet. In order to achieve an intensive understanding of the mechanism of the tube blanking process, an numerical simulation has been carried out by using the commercial software package DEFORM, which is capable of dealing with crack initiation and propagation of material. The McClintock criterion is adopted to estimate the crack initiation and propagation during blanking. Damage value of the criterion in simulation is decided with the experiment data of tension and compression test of GCr15 bearing steel. The blanking of the tube with 42 mm in outer diameter and 3 mm in thickness was simulated and the simulation was validated with experiment.

Abstract: In this paper, we carry out linear response calculation to determine the phonon density of states and the thermodynamic properties of the wurtzite and zinc-blende AlN by using the norm-conserving pseudo-potential method. The optimized lattice constant is in good agreement with the available experimental data. The internal energies increase almost linearly with temperature and the phonon free energy curves move down with increasing temperature in both structures. The zero value of the lattice vibration free energy appears at temperature 707K in wurtzite and 728K in zinc-blende AlN respectively. The specific heat capacity of the wurtzite AlN is higher than that of the zinc-blende AlN at room temperature owing to the difference of the phonon spectra.

Abstract: Cu-7.5wt%Cr alloy was subjected to severe plastic deformation at room temperature using the procedure of equal channel angular pressing. Microstructures of the processed material were investigated by metallographic analysis, SEM and TEM. The results show that grains size of the processed materials was obviously fined. Cr precipitated in matrix was distributed uniformly. And micro-hardness of the copper alloy increased a lot.

Abstract: In this paper, a multi-band chiral metamaterials (CMMs) based on complementary cross-wire structure is proposed and studied numerically. The finite element method (FEM) method was used to simulate the EM properties of the designed structure. Numerical results indicate that the giant optical activity and multiband negative refractive index can be realized in terahertz region. The proposed CMMs may have some potential applications in novel terahertz device.Particle size of bayerite (d₅₀) was about 24 μm. Al₂O₃ was obtained after calcination at 1050 °C for 1.5 h.

Abstract: In order to study the impact on the roller abrasion resistance of the surface structure parameters such as stripes depth and number, roller abrasion model experiments were carried out with quartz sand as granular material and optimal design method was used to arrange testing program. Based on structural features of roller press, a model test bed was build and stripes roller were design and manufactured according to similar principles. Roller surface structure parameters were determined by orthogonal polynomial regression design method. By processing the test data, a regression equation was obtained with stripes depth, number and the amount of wear as parameters. The results showed that: Stripes structure grinding rollers have better abrasion resistance than the light roller; The depth and the number of stripes have a greater impact on the abrasion resistance and there was an interaction between them; In the same conditions, when the stripe depth is fixed, the wear amount increases with the number of stripes increasing; when a fixed number of stripes, the wear amount decreases with stripes depth increasing.

Abstract: Ternary compound LaCo₂Ge₂ was synthesized and characterized by means of XRD, magnetic and electrical measurements. Rietveld structure refinements of powder XRD patterns confirm that LaCo₂Ge₂ compound crystallizes with a body-centered tetragonal structure of ThCr₂Si₂-type (space group I4/mmm) with the unit lattice parameters a=4.105(6) Å and c=10.264(7) Å. Nd, Co and Ge occupy 2a, 4d and 4e crystal positions, respectively. Magnetism measurements show that LaCo₂Ge₂ is nearly temperature-impendent Pauli paramagnetic down to 100 K, whereas orders diamagnetic at elevated temperatures. The (T) measurement showed that is 0.34625 and a positive temperature coefficient for LaCo₂Ge₂ is equal to 0.82178, indicating that LaCo₂Ge₂ exhibits typical semimetallic.

Abstract: Aluminum and aluminum alloy were widely used in various industrial fields,the key to application is the reliable welding. In this thesis,LF21 aluminum alloy brazing materials were designed and prepared by Orthogonal experiment,and mechanical properties of the brazing specimen was tested. Based on the GRNN(Generalized Regression Neural Network),Nonlinear relationship modle of brazing material preparation parameters and mechanical properties of the weldment was established.The results show that the model has better stability.When smooth factor value is 0.1,the network approximation error and prediction error absolute value is 0.01%.It can be realized that an nonliner mapping between the aluminum alloy brazing preparation parameters and solder joint tensil strenth based on the Orthogonal test and can do better prediction of the weld mechanical properties,according to brazing material preparation parameters.