Advanced Materials Research Vol. 908

Abstract: The unsteady aerodynamic loads are the basic of the aeroelastic. This paper focuses on the computation of the unsteady aerodynamic loads for forced periodic motions under different Mach numbers. The flow is modeled using the Euler equations and an unsteady time-domain solver is used for the computation of aerodynamic loads for forced periodic motions. The Euler equations are discretized on curvilinear multi-block body conforming girds using a cell-centred finite volume method. The implicit dual-time method proposed by Jameson is used for time-accurate calculations. Rigid body motions were treated by moving the mesh rigidly in response to the applied sinusoidal motion. For an aircraft model, a validation of the unsteady aerodynamics loads is first considered. Furthermore, a study for understanding the influence of different Mach number was conducted. A reverse of the trend of hysteretic loops can be observed with the increasing of the Mach number.

Abstract: Multiple site damage (MSD) usually occurs in the form of some small fatigue cracks at several sites within aging aircraft structures. It is very important to study the fatigue life of this kind of structure. This paper used testing method to observe the phenomenon of crack propagation, to analysis the result of the crack propagation. It provides testing reference for the study on fatigue life of MSD structures. According to the analysis of fatigue life of typical structures, a series of valuable conclusions are obtained.

Abstract: The disturbance attenuation control of the permanent magnet synchronous linear motor is studies in this paper, and its good stability is proved theoretically, using step response and MATLAB simulation the disturbance attenuation control strategy is analyzed in the sense of the gain. The simulation results of the feedback control is not only stability, but also in 0.001 seconds can make this permanent magnet synchronous linear motor system stabilizes quickly, with very good performance and stability.

Abstract: Based on acetone-H₂O system, the influence of the gas-liquid distribution inducer on the mass transfer coefficient in the rotating packed bed with the stainless steel packing was investigated. Furthermore, the absorption performance was also obtained under the experimental condition of the rotational speed of 630 rpm, the gas flow rate of 2 m³/h and the liquid flow rate of 100 L/h in the rotating packed bed with different types and different installation ways of the distribution inducer. The experimental results showed that the volumetric mass transfer coefficient K_yα per unit contact length of gas-liquid was increased by 8.6% for the forward-curved fixed blade, by 19.8% for the backward-curved rotor blade and by 33.2% with the combination of the straight radial rotor blade and the backward-curved fixed blade, respectively. Furthermore, when the gas flow rate was 2.5 m³/h, K_yα per unit contact length of gas-liquid was increased by 2.9% for the forward-curved fixed blade, by 25.3% for the backward-curved rotor blade, by 42.7% for the combination of the straight radial rotor blade and the backward-curved fixed blade, respectively. The results indicated that the distribution inducer play an important role on the improvement of the mass transfer coefficient in acetone-H₂O system.

Abstract: Drilling frame on TD165CH Down-The-Hole Drill that has large slenderness ratio and be longer than 10m is one component of Down-The-Hole drill which is mainly subjected to load.In the process of drilling, drilling frame is not only subjected to loads which are like tensile, compression and torsion and so on, and be under the influence of impacting and vibration of impactor,the situation of force is complicated.By analysing of working condition of Down-The-Hole drill,there get all kinds of limit states of typical working conditions, and then using Ansys doing finite element analysis, there get distribution of the stress and strain of drilling frame and the result of modal analysis to check whether drilling frame meets the requirements of strength and stiffness or not,and whether it is possible to resonate with the impactor or not.By analysis,Structure strength and stiffness of drilling Frame on TD165CH Down-The-Hole drill meet the requirements of practical engineering, and drilling Frame does not resonate with the impactor.

Abstract: By means of resistance strain gauge and multifunctional test bench of materials mechanics, the relation curve between the axial compressive forces of the two-ends hinged column with a rectangular cross-section and total bridge strain was obtained by the resistance strain measurement method, accordingly, by the horizontal asymptote of this relation curve the critical load of compression column was obtained. The study indicates that the critical load obtained respectively by the resistance strain measurement method and Euler formula theory fits very well, and the research results verified the reliability of the experimental method.

Abstract: A new down-the-hole drill (DTH) position method based on binocular stereo vision was presented. In this method, a pair of stereo images containing holes marker were obtained by stereo cameras, which were then segmented by the fuzzy threshold method based on trapezoidal membership functions. The hole mark centre was extracted by image invariant moment principle. Then hole mark 3D locations can be calculated by triangulation principle. Finally, the autonomous position experiments based on binocular stereo vision system were implemented on DTH test-bed. The experiments results show that the binocular stereo vision system applied to DTH drill position is reliable, and the position error is within 25mm.

Abstract: To investigate the impact of low pressure accumulator to the performance of hydraulic impactor, mathematic model of hydraulic impactor was established. By application of AMESim, The simulation models of hydraulic impactor with low pressure accumulator and hydraulic impactor without low pressure accumulator were obtained. After model calculation, the displacement, velocity of the piston and the return pressure were shown in figures. Rationality of the simulation system was verified by the compare between simulation results and experimental results. The simulation results show that low pressure accumulator can increase the impact energy and frequency of hydraulic impactor in a small degree and reduce the impact of return pressure significantly. Article provides theory basis for the designation of hydraulic impactor.

Abstract: This article investigates the effect of different injection timings on the combustion and emission characteristics of a Chinese V high pressure common rail diesel engine fuelled with blends of biodiesel and diesel (the volume ration of biodiesel is 20%). The Results show that, retarded injection timing resulted in decrease of ignition delay and combustion duration at all loads, except for 25 percent of full load. Peak cylinder pressure and maximum rate of peak pressure significantly reduced at retarded injection timing. The cycle-by-cycle variation of peak cylinder pressure first increased and then decreased, and the highest was obtained at -4°CA of injection timing. BSFC increased by 0.3% to 4.2% with retarded injection timing. Postponing injection timing effectively reduced NO_x emission. NO_x and PM emissions simultaneously decreased at full load when postponing injection. At 25% load HC and CO emissions were significantly higher than other loads and the effect of injection timing was most obvious.

Abstract: For decreasing the stress and displacement of pile clamping mechanism of hydraulic static pile drivers in the process of pile driving, optimizing the pile clamping mechanism and improving quality of pile driving, the working principle of pile clamping and pile driving were introduced briefly. The parametric model of pile clamping mechanism was constituted in ANSYS; the main parameters of the model were set. The command-flow was programmed with APDL standing for ANSYS parametric design language. And then the serialization simulation analysis of pile clamping mechanism was achieved; the cloud diagram of Von Mises stress and the maximal Von Mises stress and displacement vector sum of pile clamping mechanism were elicited. The simulation results were analyzed.