Applied Mechanics and Materials Vol. 389

Abstract: The curved structural plate components have been widely used in petroleum, natural gas, chemical industry, and other industries fields, monitoring and detecting the curved structural plate components flaw has a great significance for improving the components integrity, reliability and lifespan in service. Based on the elastic wave fundamental theory, elastic wave equations, and phase velocity dispersion characteristic curves in curved plate component, the article gives the phase velocity practical detecting method. By using the comsol finite element software, the author proposed a wave propagating forward modeling analytical method, which gives a guidance to study the relationship between the wave and the flaw. By adopting the ellipse algorithm, the article proposed a positioning and imaging method which was used to locate the flaws position and distinguish the flaws direction. Based on the theoretical and technical analysis above, a number of experiments has been done, and the results shows that the detecting and imaging method can locate and image the flaws position and its geometrical morphology precisely for the curved plates flaw detecting.

Abstract: The maglev chopper is a very important part in the maglev train technology. This paper briefly analyses the working principle of a kind of two-quadrant zero-transition soft-switching maglev chopper, discussing the choosing of the key parameters, also with the experimental study on the choosing of the switching-on time, the experimental results indicate that, if you choose the switching-on time correctly, the pulse spike and ripple wave at the switching-on time is decreased, the resonance degree is subdued, and the efficiency is improved.

Abstract: This work studied the effect of tin (1%Sn) addition in brass 60%Cu+40%Zn (commercial grade) by casting process conducted poured melt metals inside a sand mould and heat treatment in cast brass on microstructure and mechanical properties for solving the cracking of nut and bolt. Three conditions of brass sample for experiment viz.- brass 60%Cu + 40%Zn (commercial grade), brass 60%Cu + 39%Zn+1%Sn (as-cast) and brass 60%Cu+39% Zn+1%Sn (precipitation hardening). The microstructure of specimens all condition, it was found that consists of α phase and β phase. Which brass addition 1% Sn, the β phase content in α phase matrix structure more than brass commercial grade. For microstructure of brass produce by precipitation hardening, shape of α phase are slender and long which have slight distributed in β-phase. The mechanicals properties, that is hardness, ultimate tensile strength and compressive strength. It was found that the brass 60%Cu+39% Zn+1%Sn (precipitation hardening), all test mechanical properties it was higher than the all samples condition. This results can be explain incharacterization of microstructure to gives deformation of copper alloy.

Abstract: The performance of the power amplifier is closely related to their hardware components and current control modes. The work was focused on comparison of the experimental results based on different current sensors and the application of two different current control modes for 3-state amplifiers. When the same control mode was used, three kind of current sensors were tested and the corresponding amplifier current ripples were measured. Experimental results shown that when using a faster current sensor, the amplifier achieved smaller current ripples. Then a 3-state PWM current control mode and a Sample-Hold current control mode were compared based on the power amplifier circuit with the same hardware components. The performance difference in the experiments were studied and explained. The 3-state PWM power amplifier could achieve a better performance in actual use.

Abstract: Based on the properties of silica sand from gold ore tailings, several experiments, such as flotation of sulphide ore, separation of calcite and dolomite, flotation of mica and feldspar, acid leaching tests, were researched in the flotation experiment. The results showed that with series optimum conditions,SiO₂98.12% was got with 50% productivity (for raw ore) with Al₂O₃ 1.00% ,Fe₂O₃0.10% , which reached the second product standard of glass raw materials.

Abstract: The shape memory effect is associated to the recovering of a previous memorized shape due to an external action, generally a thermic triggering. In this work, we show the state of the art of shape memory materials and their applications especially as actuators and integrated in more complex machines.

Abstract: Friction stir welding (FSW) is a rapidly emerging joining technology due to significant advancements in tooling and process development. Latest literature relating to finite element analysis (FEA) of mechanical behaviour of FSW joints is reviewed in this paper. The recent development in FEA of mechanical behaviour of FSW joints is described with particular reference to two major factors that influence the performance of FSW joints: static behaviour and fatigue behaviour. The main FE methods used in FSW performance are discussed and illustrated with brief case studies from the literature.

Abstract: In this paper, a new kind of finite element method (FEM) is proposed, which use the two-dimensional Hermite interpolation scaling function constructed by tensor product as the basis interpolation function of field function, and then combine with the energy functional with related mechanics and variational principle, the wavelet finite element equations for solving elastic thin plate unit that constructed in this paper are derived. Then the bending problem of thin plate is solved very quickly and availably through the matlab program. The numerical example in this paper indicates the correctness and validity of this method, and has high calculation precision and convergence speed. Moreover, it also provides a reliable method to solve the free vibration problem of thin plate and the pipe crack problems.

Abstract: In this study, a novel process to forge thin walled products using bulk-sheet forming concept is developed to overcome drawbacks of a conventional multistage backward extrusion. A newly developed process design is suggested based on numerical analysis, and feasibility of one-stage forging process is discussed.

Abstract: Multiwalled carbon nanotubes treated by hydrochloric acid treatment were in detail analysized by thermogravimetric analysis and SEM. The optimal technological conditions are that the concentration of the solution is 6 mol/L, the treating temperature is 90 °C, the treating time is 4 h and the mass ratio of solution to MWCNTs is 200:1. This result can also be verified by the contrast of SEM photographs of untreated and treated MWCNTs.