Applied Mechanics and Materials Vols. 423-426

Abstract: This article is based on TengChong County municipal sewage treatment plant supporting pipe network project, monitored and analyze the vibration influence on the historic building taiji bridage by the Pipe-jacking blasting construction. Via regression analysis of velocity in vertical direction of measuring points on the basis of monitoring data, obtained the attenuation laws toward taij bridage direction. The vibration signals were decomposed into IMF components by using HilbertHuang transform (HHT),analyzed the several IMF components could be acquired the timefrequency characteristics of the vibration signals. These will provide references to the similar projects.

Abstract: Dividing wheel-track system of subway into a series of sub-systems, the statistical energy analysis (SEA) model of wheel/track system is established. The factors affecting the wheel/track noise, such as modal density, damping loss factors, coupling loss factors, are gotten by theoretical analysis combined with experiments. The calculated results show that the track noise is about 4.5 dB(A) higher than the wheel noise at 160 km/h, and the wheel noise is reduced by 2.8 dB(A) at 160 km/h and by 2.3 dB(A) at 90 km/h by attaching damped layer plates to the wheels, but the total reduction is only 0.9 dB(A) at 160 km/h and 0.4 dB(A) at 90 km/h, so the attempts to reduce the total noise should exert noise control measures on the track, not on the wheel.

Abstract: The self-feedback-friction damper can adjust damping force according to the intensity of vibration. Damper will produce suitable damping force to achieve the purpose of damping energy consumption. At the same time, the damper may also produce a large amount of heat which can greatly affect the damper's energy consumption performance. A temperature compensation system is designed to solve the problem in the article. Structure temperature field is also worked out by finite element analysis to find out the effect of temperature on the damping force.

Abstract: In this paper, two ways of levitation support of ultrasonic thrust bearing are disscussed. Based on the mechanism of the near-field ultrasonic levitation, the front cover of the piezoelectric transducer is designed as conical structure.The ultrasonic radiation pressure which distributes on the conical surface can be decomposed into the axial and radial supporting the levitation subject bidirectionally. Finnally contrast experiments are carried out, indicating that when the requirement of levitation mass being satisfied, the way of bidirectional support runs more stably compared with the pure way of the axial levitation support.It supposes that the way of bidirectional levitation support is more conducive to improve the rotating speed of the rotor.

Abstract: Dynamic models of the heating, ventilation and air-conditioning (HVAC) systems in a temperature controlled room are very useful for controller design, commissioning, and fault detection and diagnosis. A transient model is a set of time differential equations in mass, energy and momentum balances. These transient equations contain parameter values for validation. The parameter such as thermal capacitances of the room chamber, heat transfer coefficient of room panel, heat transfer coefficient of evaporator are difficult to determine because they are related to unsteady condition and have to be considered to account for room energy storage. Many researchers have been studied the transient model for HVAC system by setting an assumption that there parameters are already known. None of them has been investigated into the parameter identification. This research work focused into the parameter identification technique to determine the thermal capacitances of the room chamber, heat transfer coefficient of room panel, and heat transfer coefficient of evaporator. The transient model of a refrigeration unit for an air-conditioned room was analyzed. Block diagram technique along with computer simulation technique were applied for the task. Experimental tests were setup to validate this model.

Abstract: The response of a large-size cooling tower with 250m high subjected to the seismic action are investigated by both random vibration theory and response spectrum method. Shell element is taken to model the tower body, and beam element is used for the circular foundation and supporting columns. The earthquake motion input is a colored filtered white noise model and mode superposition method is adopted to analyze the random response of the large-size cooling tower. The paper presents the power spectrum density functions (PDF) and standard deviation of the displacement of the top and characteristic node, and the analysis results indicate that the results of the stationary random vibration theory and the response spectrum method are the same order of magnitude. The power spectrum density function of the bottom node stress is obviously bigger than the one at the top and the throat, and the random response of meridonal stress is dominated at the top. In addition, the peak frequency position of the power spectrum density function is different from the corresponding stress.

Abstract: There are a lot of connection forms between the machine parts, of which the most typical are bolted joints. There are many factors influencing the dynamic properties of bolted joints and their mechanism is very complicated. Their properties have great significance to machine accuracy prediction. Domestic and overseas scholars have conducted many extensive researches on bolted joints, which main influence factors and internal mechanism are clarified. There is a more in-depth research on the analytical solution and the parameter identification of dynamic properties of bolted joints, and has achieved certain results, but the researches on mechanical properties are not mature. This article bases on microscopic analysis, macroscopic modeling, macroscopic test, nonlinear problems to classify research results, analyze the deficiencies, and point out the future research trend.

Abstract: Through the analysis and comparison of the results of static and dynamic performance testing of a series of laminated steel pieces isolators used in the vibration isolation of warships, in the number and thickness of laminated steel pieces of the same circumstances, laminated steel arc and preload of test samples had a certain impact on the values ​​of static stiffness, dynamic stiffness, damping ratio as well as dynamic and static stiffness ratio.

Abstract: Horizontal-screw conveyor is a key equipment for bulk delivery. In order to optimize the design and improve the efficiency of bulk delivery, this paper makes a depth research on it. Analysis tool (EDEM) with discrete element and a setting periodic boundary model are applied in this work to simulate the horizontal single head screw conveyors grain (e.g. rice) delivery condition under different fill levels and screw rotational speeds. From the analysis of the simulation results, a conclusion can be drawn that when conveying grain materials, horizontal single head screw conveyor should set an appropriate fill level and screw rotational speed according to the property of grain materials, to make the horizontal screw conveyor with a high transmission efficiency and low energy consumption.

Abstract: A slope landslides generally at the place where the shear strain increment is the largest. This position is considered as the standard of defining sliding surfaces to assess the slope stability under the action of the foundation. A new method is proposed to determine the potential sliding surface, which is based on the largest shear strain increment. Firstly, the stress and strain in the slope were calculated by using the finite difference software-FALC3D. Secondly, a series of vertical line would be set in the calculating section. And then the discrete coordinates of the sliding surface, where the shear strain is largest on the vertical line, would be found through programming fish program. At last the position and shape of the sliding surface can be obtained through carrying on curve fitting of the discrete points by using the least squares method. The concept of this method is clear and can reflect the true form of the sliding surface through contrasting with the limit equilibrium method. Sliding surfaces of different depths and distances of slope are researched and a quadratic function is put forward which can describe the trends of glide direction. Three coefficients of the quadratic function were analyzed and the corresponding expression was obtained which can provide a reference to specification revision and engineering.