Applied Mechanics and Materials Vols. 121-126

Abstract: According to the detection and monitoring requirements of the mechanical equipments used in coal mine, this paper achieves the state signal acquisition of the mechanical equipments in coal mine by using self-research portable intrinsically safe recorder of vibration measurement used in cool mine, and uses the vibration signal analysis technology to analyze the obtain signal, actualizing the running condition detection and monitoring of the mechanical equipments in coal mine. This paper presents a method for fault diagnosis of the gear reducer in coal mine.

Abstract: The classical preload design method of prestressed frame of hydraulic presses is based on the assumption that the beams of the frame are rigid, which is not agree with practice. In order to eliminate the unbalance load of the frame of a 100MN hydraulic press due to improper prestressing, tie rod preload distribution in prestressing of the frame is researched with respectively mechanics of materials and the finite element methods. According to mechanics of materials and finite element analysis results, reasonable tie rod preloads and sequence of preloading are obtained and the unbalance load of the frame of the hydraulic press is solved. It also provides references for the preload design of prestressed frame of hydraulic presses.

Abstract: Various frequency bands of noises are contained in the actual signal. And it's difficult to eliminate the noise portion, which has a time delay and same spectrum with the original signal with conventional filtering methods. Based on the time delay and the multiplication delay characteristics of the fractional Fourier transform (FRFT), we put forward a FRFT time delay model, which can increase distance between the signal and the noise component. Through corresponding Fractional Fourier Transform to noise-containing signal, the distance between the signal and common frequency noises can be constantly increased within the transform domain, thus easily separating the noise component. The algorithm of the model can be simply deduced, easy realized and converged fast. In the experiment, we simulated the separating characteristics of the transform, and used the method to de-noise the grating signal. Compared with other traditional methods, we find that the FRFT acquired a better result.

Abstract: Aimed to overcome the deficiency of abundant data to web mining, the paper proposed an association-analysis based algorithm. Firstly, we construct the relation Information System using original data sets. Secondly, make use of attribute reduction theory of Rough sets to produce the Core of Information System. Core is the most important and necessary information which cannot reduce in original Information System. So it can get a same effect as original data sets to data analysis, and can construct classification modeling using it. Thirdly, construct indiscernibility matrix using reduced Information System, and finally, get the classification of original data sets. The experiments shows that the proposed algorithm can get high efficiency and can avoid the abundant data in follow-up data processing.

Abstract: In order to determine the key parameters of blueberry picking machine, the three-dimensional solid modeling of Blueberry Picking System is researched based on the Pro/ Engineer of CAD software. The mechanical dynamic software MSC.ADAMS is used to carry out dynamic simulation for the model of Blueberry Picking System. The key parameters of the system are chosen through the force of the branches. The working parameters of the picking system were optimize by simulating the parameter in the limited range step by step, which provides technical evidence for the achievement of physical mechanism.

Abstract: The acoustic signals were strongly related to the behavior of the arc column, the molten pool and droplet transfer in gas metal arc welding(GMAW).In this study, all the work pieces (JIS SS400) were welded at the same speed with different currents using a gas metal arc; the purpose was to observe the relationship between these factors. Using a sound capture card and microphone we collected the audio signals generated by the welding. In this paper, wavelet package transformation (WPT) decomposes the sounds signals into 128 channels within the frequency domain. The properties of the audio signals were analyzed by the wavelet-based channel energy. The ROC (Receiver Operating Characteristic) parameters, (Ac, Se, Sp, ppv, and npv), were used for classification performance evaluation. Experimental results also show that acoustic emissions are useful in the quality control of plasma arc welding.

Abstract: Numerical simulation of three-dimensional transient turbulent flow in the whole flow passage of a Francis turbine were based upon the large eddy simulation(LES) technique on Smargorinsky model and sliding mesh technology. The steady flow data simulated with the standard k-εmodel was used as the initial conditions for the unsteady simulation. The results show that LES can do well transient turbulent flow simulation in a Francis turbine with complex geometry. The computational method provides some reference for exploring the mechanism of eddy formation in a complex turbulent of hydraulic machinery.

Abstract: As for the widely used five-axis NC machine with dual turntable, this paper constructs the kinematics mathematic model and finishes solving the machine kinematics formula on the basis of workpiece coordinates system. On the basis of detailed discussion on the effective method for calculating nonlinear error, this paper provides the analysis and calculation and processing procedure for overproof. By processing cutter location (CL) data, the validity and feasibility of the method is tested correct by simulation. Accordingly, this paper provides an inerrable basis for the overproof processing method for design of the general postprocessing system.

Abstract: A kind of wind-solar hybrid experiment system is designed for teaching and research. The experiment system is consisted of wind energy subsystem, solar energy subsystem and energy storage subsystem. Both wind turbines and photovoltaic arrays can generate electrical power independently. The wind energy subsystem and solar energy subsystem have independent control modules. The whole experiment system connect grid with an inverter. And the control module manages the three parts to cooperation in the reasonable way.

Abstract: The subsurface transverse median crack system due to spherical contact in brittle coating-bond -substrate sandwich structure is investigated with an emphasis on stress intensity factor near the crack front using finite element method. This crack system emanates from the lower surface of the brittle layer and extends transversely towards the top of contact surface, resulting in ultimate failure of the structures. In this paper, finite element mesh is designed, and the crack front mesh designing solution for a surface crack subjected to remote tension is validated with Newman and Raju empirical equation. Then the proposed crack front mesh design solution is applied to a typical sandwich structure of various modeling parameters to obtain the SIF with 3D-J integral.