Applied Mechanics and Materials Vols. 385-386

Abstract: In order to explore the effect of ionic groups on the properties of the liquid-crystalline polymers, a series of new main-chain liquid-crystal ionomers (LCIs) were prepared from sebacoyl chloride (SD), brilliant yellow (BY) and various amount of 4, 4-Dihydroxy-2, 2-dimethyl Benzalazine (DDBA) and isosorbide (ISO). The structures of the polymers were characterized by FT-IR and UV spectroscopies. Differential scanning calorimetry (DSC) was used to measure the thermal properties of the polymers. The mesogenic properties were investigated by polarized optical microscope (POM), differential scanning calorimetry and X-ray diffraction measurements. The results show that the LCIs are chiral smectic C (S_C^*) and nematic (N) LCIs exhibiting broken focal-conic texture and schlieren texture. The introduction of ionic units in the LCIs led to the clearing point and mesogenic temperature range increasing and the glass-temperature decreasing, but did not affect the mesogenic type and texture, as compared with the corresponding polymer P₀.

Abstract: The purpose of this paper is to find a efficient model to simulate the thermal ignition of gasoline-air mixture. First, Detailed chemical reaction model of gasoline-air mixture thermal ignition is discussed. that is, chemical reaction chains of controlling of thermal ignition are got according to the characteristic of gasoline-air mixture; through sensitivity analysis of temperature and species concentration, reaction equations are selected within a certain temperature range; based on the relation between chemical reaction rate of species and thermodynamic parameters, both the rate of species consumption or production and the heat release rate of species chemical reaction are got. Then using low mach, compressible equation as control equations, coupling the detailed chemical reaction model and radiation model, the mathematical model of gasoline-air mixture thermal ignition process, namely comprehensive model,has been established on the basis of unification of chemical kinetics and thermodynamics in this paper. In the end, taking gasoline-air mixture thermal ignition due to contacting with hot wall continuously where temperature is raising in a confined insulation space as example, this paper complete the numerical simulation analysis based on the comprehensive model. The result is demonstrated by the experiment data.The research result shows that the comprehensive model, in which fluid field, boundary conditions and detailed chemical reaction control together is efficient for gasoline-air mixture thermal ignition.

Abstract: This paper presents an experimental study on the tensile mechanical properties of carbon nanotube (CNT) fibers by in situ Raman spectroscopy. The comprehensive spectral information, such as Raman shift, width and intensity, are recorded during the whole loading–unloading–reloading procedures of CNT fibers. Based on the experimental results, the elastic-plastic deformation evolution of CNT fibers are analyzed at multi-scale levels. It is found that the elastic deformation of the fiber is mainly attributable to the elastic stretching of the CNTs inside the bundles. And the plastic deformation is caused mainly by the slippages at the interfaces among CNTs inside the bundles. Meanwhile, the CNTs deform elastically during the whole loading–unloading–reloading procedures.

Abstract: We present the sum-frequency (SF) generation of antiferromagnetic sandwich structure NM/AF/NM in the THz frequency field. In the geometry with the anisotropy axis parallel to the film surface and normal to the plane, using TE wave obliquely incident upon the film, we find that SF outputs is sensitively affected by the incident angle and the incident frequencies.

Abstract: To enhance the microstructure properties and dimensional accuracy of drill steel, rigid plastic finite element methods were used to analysis the Mannesmann piercing in drill steel production. The three-dimensional thermal-force coupling FEM models were built with different plug position. Influence of plug position on the force and strain rate is got through simulation. The results show that the dimensional accuracy of drill steel hollow can by increased by the amount of increase plug position.

Abstract: Multi-point forming (MPF) is an advanced flexible manufacturing technology for three-dimensional sheet metal forming. The substance of MPF is replacing the conventional solid dies by a set of discrete punches called punch group. Due to the discrete contacts between the workpiece and punches, the dimple defects occurred, which are inevitable and particular for MPF. In this study, the analysis of the deformation features of the dimple defects was implemented. The dynamic explicit finite element method was chosen to implement the simulation of MPF process. The influencing factors of the surface defects were researched. The relevant experiment was implemented, and it verified that the forming defects decreased with the increasing of the thickness of metal plate and the objective surface curvature radius.

Abstract: The combination of numerical simulation and orthogonal experimental design method can reduce the test number. Structural parametric modeling research on corrugated tube of heat exchangers in our work to establish the fluid flow and heat transfer numerical simulation model. A scheme of orthogonal test of a corrugated tube, which includes 4 factors and 3 levels and has taken heat exchange quantity, resistance of the internal tube and annular gap as evaluation indexes, was designed. A method combining with the difference and the variance analysis was taken to analysis the result of orthogonal test, and the effect of different structure parameter on corrugated tube was achieved. Finally the optimal structure parameter of the corrugated tube was obtained by a comprehensive balance method, and those methods above-mentioned provide a reference for the design or promotion of the corrugated tube of tube heat exchanger.

Abstract: The workspace of a machine tool is an important indicator to measure a machine tool performance as well as the important data of mechanical design and motion planning. This article in view of the 3-TPT parallel machine tool. First, according to the positive and inverse solution of Mechanism kinematics, the expression of the range of motion of the moving platform reference point was calculated. Then, by considering the effects of rod length and Hooke joints on the workspace, the workspace could be simulated by using MATLAB software and LabVIEW software.The simulation results show that the parallel machine tool workspace is continuous and no caves.

Abstract: Rotating platform is one of the railway cranes key components, for the installation of crane jib, lifting mechanism, luffing mechanism and rotating mechanism. In order to guarantee the normal operation of the crane, the rotating platform should have enough stiffness and strength. Based on the finite element analysis software WORKBENCH, this paper takes a kind of 160t double rotary rescue railway crane as the research background, and completed the parametric modeling and structure analysis of the rotating platform including the flexible counterweight for the first time. Thus avoiding the errors brought by the equivalent weight before. And on this basis, through the finite element analysis software ANSYS, the thickness of various parts of the rotating platform was optimized. As a result, the weight of the rotary table has a significant reduction. This will provide a new method for the design of railway crane in the future.

Abstract: This paper researches on the optimization of the effective thermal efficiency of diesel engines for the target optimization on the test bench to investigate the economical efficiency impact of combustion system parameters of diesel engine fueled with biodiesel to determine the optimum value of these parameters in order to improve the burning biodiesel combustion efficiency of the diesel engine. Results show that the system parameters through the optimization of combustion can meet the standard of the diesel calibration power levels up to the original machine, combustion efficiency can be achieved for more than 32%.