Applied Mechanics and Materials Vols. 138-139

Abstract: The Green quasifunction method (GQM) is applied to solve the bending problem of clamped orthotropic thin plates with trapezoidal boundary shape on Winkler foundation. Firstly the governing differential equation of the problem is reduced to the boundary value problem of the biharmonic operator, and then it is reduced to the Fredholm integral equation of the second kind by Green’s formula. A Green quasifunction is established by using the fundamental solution and the boundary equation of the problem. This function satisfies the homogeneous boundary condition of the problem. The singularity of the kernel of the integral equation is overcome by choosing a suitable form of the normalized boundary equation. The comparison with ANSYS finite element solution shows good agreement. The proposed method is a novel and effective mathematical one.

Abstract: The stress-strain curves of glass-fiber reinforced silica aerogels (GRSA) are obtained by carrying out the quasi-static and split Hopkinson pressure bar (SHPB) experiments. The dynamic compression process of experimental materials are precisely controlled with the “frozen strain” method, and the effects of relative density, diameter and strain rate on dynamic compressive mechanical properties are discussed. Then the compressed samples are observed with scanning electron microcopy (SEM). Considering the Sherwood-Frost constitutive relation and contribution of gas to the strength of the material, the macroscopic phenomenological constitutive relation of this material is developed.

Abstract: The electricity changing models for the energy supply of electric vehicles are described and introduced. A more suitable method of fast replacing battery of electric vehicles is found and the practical method and process of quickly replacing battery are focused as a major topic. The changing equipment used is studied and described while the efficiency of electrical changing equipments is discussed. The reserve number of batteries in power charging plant and the number of vehicles that each quickly changing device could service are studied and derived.

Abstract: In this paper, the principles of modern emission spectrography technique was described and the analytical process and characteristics of it was introduced. Based on an review of its application in equipment oil monitoring, emission spectrography was thought a very valuable technique of lubricants condition monitoring. Now, emission spectrography has become the core of the modern oil monitoring technique, and its development and application prospect are extremely wide.

Abstract: The amorphous formation mechanism was studied from the viewpoint of the crystallography. The experimental results showed that the heterogeneity atoms with chemical bonds had a higher capability of forming into compounds than that of congener atoms. It was proposed that the banded structure was induced by the variation of active atoms with a proper thickness, alternated depletion and enrichment of anions in the diffusion layer due to generation and evolution of hydrogen gas. The chemical force plays an important part in the formation. The factors working on chemical reaction affect the formation in the same. A number of steady motes are in a high speed movement, and collide with each other in all probability. The formation of amorphous alloys is the result of massive nucleus appearance, which was proposed from the crystallography in this paper. The cause of the chaotic distribution is of the suppression of each nucleus growth. The short-range order atomic structure is of the atomic nucleus growth orientation. And the long-range disorder structure is of the massive nucleus suppression growth.

Abstract: Cladding experiment with parameter variations was presented to manufacture the better processing property coating by laser cladding self-fused Ni-based ceramic powder of ZrO₂ composite on the excircle surface of 304 SUS. The influence of the laser process parameters on macroscopic view, microstructure and micro-hardness of the laser cladding layers were investigated. The results show that we can get better coating when laser power is 1.5KW, and that the cladding layer microstructure has the trend of refined framework with the growing of scanning speed; micro-hardness will be higher and distribution from substratum to surface with little fluctuate by optimizing scanning speed.

Abstract: ROPS is an effective way to reduce casualty rate in the rolling accident. This paper introduces the design of a cab to strengthen safety-ROPS large wheel loader method. The finite element model, it's a ROPS rear, absorbers and supporting structure frame of the safety-cabs, was created. Force and displacement boundary conditions obtained in accordance with the international standard ISO3471:2008-The large deformation elastic-plastic finite element analysis, horizontal, vertical and ROPS vertical load cases of performance testing and the corresponding lab for investigation. The test results show that the design can meet the requirements of ISO3471 ROPS: 2008. Test results differences and simulation and welded joint of the fracture analysis on the reason.

Abstract: A vibration test and modal analysis has been completed, in order to improve the use reliability and extend service life of the large vibrating screen. Accurate natural frequency, modal shape, modal damping and some other modal parameters is got in the presented work. The result shows that there is one order frequency near working frequency of the vibrating screen and the modal shape is whole torsion around the x axis and the discharge end’s bend along z axis. This order frequency can increase the elastic deformation of the screen surface in the four horns points and change the materials movement speed which makes the moving of the materials nonuniform. We also know that the bend displacement of the discharge end is larger which indicates that the stiffness of this part is smaller. So the structure of the discharge end needs to be modified. The analysis result also demonstrates that the part of the side plate near the feed end has a larger vibration, thus a further stress analysis of the side plate should be made. The analysis result of the modal test is used to correct the finite element theory model, to make the theory modal reasonable, thus a further dynamic optimization of the vibrating screen can be finished easily.

Abstract: To solve the problem of part’s section thinning easily occurred in hot press forming, the numerical simulation model of hot press forming process of a B-Pillar on one domestic car was established, the forming process was simulated by PAM-STAMP 2G software, the area thinning on the part were forecasted. Then through modifying the corner radius and the tiny shape of the part, the thinning level lightened greatly, the effect was certificated by new simulation results and practical production.

Abstract: The effect of forming temperature on the deep drawability (limit drawing ratio (LDR)) of AZ31 magnesium alloy sheet was studied both numerically and experimentally by the use of finite element analysis software DYNAFORM and specially designed warm deep drawing die set. The simulation model was built by SolidWorks 2009, 3-Parameter_Barlat model with BT shell unit was adopted as material model. The constitutive relation of the material was provided by uniaxial isothermal tension tests at different temperatures. After being set, all parameters were referred to famous explicit dynamic solver LS-DYNA. The simulation results showed that the LDR of the AZ31 magnesium alloy sheet is increased with the increase of the temperature initially, but after the temperature reached 423K, the LDR reached the maximum, and then decrease with the increase of temperature in the temperature range studied (room temperature-673K). PTEF was used as lubricant in the experiment. Experimental results showed same trend as numerical simulation results in the studied range of temperature, and LDR reached the maximum of 3.0 at 423K. It is shown that the results of numerical simulation have a good agreement with that of the experiment. By analyzing the microstructure of the drawn-cup walls at different temperatures, it is found that grains were stretched along the direction of tension at temperatures lower than 423K. And there appeared a large number of fine recrystallized grains when forming temperature is 423K showing that dynamic recrystallization occurred during forming process. Dynamic recrystallization conducted completely when forming temperature increased higher than 423K, but the material softening would aggravate with the increase of temperature and on the contrary would do harm to the deep drawing of AZ31 magnesium alloy sheet, resulting the decrease of LDR.