Applied Mechanics and Materials Vol. 164

Abstract: 9 models of tall buildings with different rectangular cross-sections are tested in a wind tunnel. After processing and analyzing the measured data of fluctuating pressure on the models, the effects of models’height, aspect ratio, side ratio on the power spectra of torsional wind loads are studied. New formulas of power spectral density of torsional wind loads are proposed by curve fitting method. The applicability of the formulas has been verified by the results from the wind tunnel test.

Abstract: A new type of tire building drum based on parallel mechanism was presented and the analysis of the structure was carried out.The calculation of dof and the output motion type analysis and positive solution and inverse solution were included. Solid model of the mechanism was set up and the trajectory analysis was conducted using software of UG and MATLAB, which provided theoretical base for optimal design application of the mechanism.

Abstract: Shapes and geometry parameters of piezoelectric vibrator have a greatly influences on its energy harvesting ability. In this paper, both of static and modal characteristics of piezoelectric vibrators were respectively simulated by using the finite element analysis software Ansys, where influences from stress and the exciting force’s frequency on the outputting voltage of a cylindrical piezoelectric vibrator and a triangular cantilever piezoelectric vibrator were analyzed. The numerical simulation results show that its geometry sizes of triangular cantilever piezoelectric vibrator could result in its outputting voltage and first-order natural frequency’s shift, however, the exciting frequency of the external force has no any influences on its outputting voltage of the cylindrical vibrator. Besides, an optimized design was researched in order to improve its power generation capacity per unit volume for the triangular cantilever piezoelectric vibrator.

Abstract: Some problems of testing rock dynamic parameters in the SHPB experiment were analyzed and the relevant measures were proposed, which included how to determining the fracture time and the dynamic load etc. Based on the dynamic fracture experiment in the SHPB system with flattened Brazilian disc made of marble, the strain gauge technique to get the accurate fracture time was applied, and the different pulse shaper were adopted to get more precise wave data. The effective test methods of determining rock dynamic fracture toughness were discussed.

Abstract: In order to meet the demand of the oil-well pump lifting test, designed a set of dynamic system, which can do long stroke reciprocating motion rapidly. On the use of composite liquid cylinder can effectively solve the problem of the load force is not the average when the cylinder moves reciprocally. The maximum lifting force of dynamic system is 120kN; maximum speed is 0.8m/s, reached the design index. At the same time, this set of dynamic system combined electro-hydraulic proportional control method and the oil production, provides a new exploring space.

Abstract: Due to business development, a Shipyard Co., Ltd. in Guangdong planned to remould a double girder gantry crane of MG32/10-37A5 (32t-37m) into a type of 20t-37m and to heighten 6m lifting height of structure. A Cranes Machinery Co., LTD. in Guangzhou undertook this job. After the completion of transformation for the crane, the serious laterodeviations of the crane were found in operational process, which affected its safety use. This paper used a finite ANSYS to perform the modal analysis of the crane before and after reconstruction. The results show that the dynamic stiffness of the remoulded crane was reduced obviously. For the reason, the four reinforcement schemes of the crane were put forward by the Cranes Machinery Co., LTD.. This study again performed the model analysis for the schemes and selected an optimal one by calculation, analysis and contrast, which has successfully solved the above problem. The present results can provide a reference for solving similar problems in the future.

Abstract: Through the wave-packet propagation diagnosis (WPD), the essay discusses and analyzes the characteristics of wave packet distribution and dynamic system of wave energy propagation during the extended period of the massive drought in southwestern region in the country by using the reanalysis grid data of the daily NCEP/NCAR geopotential height field and 10×10 horizontal resolution from September 2009 to April 2010. The results show that: the characteristics of dynamic system of wave energy propagation at the middle and high height fields can better reflect the stage features of this drought during the period. The wave energy time-variation chart shows that the wave disturbance during the drought is weak and the wave packet value is small. However, the wave packet value during the drought still has some changes, reflecting the characteristics of the drought change in weakness. At the maintenance period of the wave packet value, the drought is often severe, and when the wave packet value changes greatly, the magnitude of the drought will change. Seen from the characteristics of longitudinal and altitudinal propagation of the wave energy, when the wav packet strength increases, the energy will accumulate and the drought tends to be weakened; on the contrary, when the wave packet strength decreases, energy will discharge and the drought will become more severe—particularly when the wave packet weakens quickly, the drought will become more drastic. This study provides a meaningful idea for discussing the forecast of the scale weather process during the extended period.

Abstract: In order to measure accurately air fuel ratio in the engine exhaust gas, the Hammerstein model of the exhaust gas oxygen (EGO) sensor was identified using the multivariable output error state space (MOESP) algorithm. Firstly, a static model of the EGO sensor was identified based on engine experiment data as a static nonlinear part of the Hammerstein model. Then, the MOESP algorithm was used to build a state space model (SSM) of dynamic linear part of the Hammerstein model. To estimate model order, the Akaike Information Criterion (AIC) and the Minimum Description Length (MDL) criterion were computed, and validity of structure identification was verified by residual analysis. Then, the auto-regressive model with exogenous input (ARX) was compared with a subspace model. The result shows that a two-order SSM using MOESP algorithm is suitable to dynamic part of the Hammerstein model for EGO sensors.

Abstract: Nowadays, the spiral cutting machines have been widely used in many areas, such as packaging materials. However, the theoretical researches of that are very rare in academia. On the one hand, the machines’ technological principles are the commercial secrets. On the other hand, developing manufacturing of the machines has no theoretical basis. So, in a word, it’s blank in academia about the spiral cutting machines. In this article, we did quantitative analysis on the part of spiral knife roller and blade, and also set up a modal by describing that in a mathematical way. In addition, we analyzed spiral knife dynamically establishing equations of blade, ground point, roller as well, and finally realized dynamic simulation of the spiral knife by matlab tool. What’s the most special feature of this simulation is that it can do simulations for different parameters. The simulation is convenient for deepening theoretical researches, optimizing parameter selections and being auxiliary tools of design.

Abstract: A new photochromic diarylethene compound, 1-[(2-methyl-5-(4-cyanophenyl)-3-thienyl)]-2-(2-methylnaphthlen-1-ly)perfluorocyclopentene (1o), was synthesized. Its properties, including photochromism, fluorescence and kinetics properties optical storage propertieswere investigated in detail both in solution and PMMA amorphous film. It underwent reversible cyclization and cycloreversion reactions upon alternating irradiation with UV and visible light in hexane