Advanced Materials Research Vols. 479-481

Abstract: The dynamic characteristics of the NC machine are the important technical indicators of NC machine performance, and the precision of existing machine's dynamic characteristics evaluation analysis that based on structural dynamics modeling and simulation is poor. For this problem, this paper presents NC machine dynamic characteristics evaluation methods based on Grey Correlation Analysis. This method, by measuring the vibration signal of feature points in NC machine and making 1/3 octave spectrum analysis for vibration signal, can obtain the characteristics data sequence of vibration signal. Through the grey correlation analysis method, calculate the relevancy between the characteristics data sequence of each vibration signal and that of ideal dynamic characteristics, and quantitatively evaluate the dynamic characteristics of machine tools according to the size of the grey correlation. Took three same type NC milling machines as study objects, designed the cutting vibration resistance experiments, used this paper's method for the evaluation analysis of the comprehensive dynamic characteristics of NC milling machine, and obtained the evaluation results which is in line with the actual dynamic characteristics of machine tools, and verified the evaluation method of comprehensive dynamic characteristics that proposed in this paper.

Abstract: The vibration of a complicated pipeline connected with centrifugal pump has been studied by ANSYS. The first 32 natural frequencies and the first five modal shape of the pipeline system is obtained by Modal analysis. The result shows that its excited frequency is close to the 30th natural frequency of the pipeline system，which will result in resonance. Because excited force caused by pulsatile fluid in pipe can make pipeline to has a compulsive vibrations, harmonic respones analysis is used to determine continuous dynamic characteristics of pipeline. The critical frequencies of node with the maximal amplitude at 30th modal shape are 12.452Hz and 56.284Hz by investigating its spectrum image of displacement. The major principal stress at two critical frequencies, far exceeding the yield strength of material, is respectively -1223MPa and 621 MPa, which demonstrates that the pipeline are very incidental to be destroyed.

Abstract: Because of PASSIM 12K cigarette machine improper design, equipment parts wear and tear, and aging sound-absorbing material, unit will generate a lot of noise when running. Through analysis noise spectrum characteristics of main suction cabinet, determine the characteristics of broadband noise spectrum, complete the design of vibration isolation system. And after transforming, measure noise spectrum value of main suction cabinet from 86dB to 76.5 dB

Abstract: Isoparametric B-spline wavelet functions can provide excellent approximation for smooth functions. In this paper, the response of composite laminated plate subjected to explosions is analyzed by using a double thick beam FEM mode based on the spline wavelet function. This mode, which can be considered in the distribution of normal stress and transverse shear stress simultaneously, is very important in the analysis of thick plate or blast-damage mechanism. The mode in analyzing underground structure and earth medium respond has the advantage of high precision and fast constringency and is easy to establish a element displacement function. The comparison between simulative and experimental results shows the effectiveness and precision of this method.

Abstract: Considering back and forth and the complexity of earthquake loading, according to theoretical analysis, this paper is verified theoretically that the natural frequency changes of structure contain the information such as location and degree of the damage in earthquake, based on this theory, applying the large common software – ANSYS, and an experiment to simulate the damage of a six-storey-high frame structure is used, extracting the natural frequency changes and forming the input vectors of the neural network, the structural damage is detected by the neural network trained, the result showed the effectiveness of this method in the engineering.

Abstract: To make the structure of the car more rational, we established a modal test system of car's body-in-white in this paper. In experiments, we use the method of single-point excitation and multi-point collecting vibration, PULSE 12.5 modal test consultant and Mescope modal analysis software. Meanwhile, the excitation point is in the front of the load beam of better rigid. Through the system, different order modal frequencies and modal characteristics of body in white are computed. The modal analysis results and frequency characteristics of the car’s excitation are compared and analyzed, and they can supply the reference standard for dynamic design and revision．

Abstract: Analysis of slope stability based on BP neural network, the analytical model of slope stability is built. Aiming at the defects that BP neural network is likely to fall into local optimum in the progress of parameter optimization; DE is associated to put forward the DE-BP neural network prediction model that is coded by real numbers. The results show that this model has a high precision for the analysis of slope stability. It is feasible and efficient to analyze slope stability based on BP neural network.

Abstract: Magnetorheological grease is a new smart magnetorheological material with non-sedimentation problem after magnetorheological fluid and elastomer. Squeeze-type damper is designed with small displacement; vibration characteristic tests of magnetorheological grease damper are presented, and the test-data is processed with matlab software. Under different current and frequency, the characteristic relationship of damping force-displacement and changes of the indicator diagram are studied experimentally. It comes to the maximum effective load current and the maximum effective vibration frequency of magnetorheologic grease damper, and damping characteristic by data fitting. Though analyzing the vibration reaction, vibration characteristics are obtained, it can also provide important support for MRG damper in development and vibration applications.

Abstract: According to the relation between exciting force and the pretightening force, the parameter of pedestal and equipment systems can be variable or invariable. The differential equation for forced vibration problem of the system has been established. The condition whether piecewise linear vibration will happen has been found. The result shows that the system will appear multi-frequency vibration response on the condition of single-frequency turbulence force. The results in this paper can be applied to the installation of the equipment.

Abstract: Based on finite unit impulse response, FIR digit filter is designed according as the given power spectral density (PSD) characteristics beforehand. By controlling the parameters of filter, amplitude-phase characteristics that can meet completely the preconditions and demand is obtained. And then white noise is inputted to filter, random vibration time signal is generated. Moreover, the method of parameters analysis of AR autoregressive model is used to estimate and validate power spectrum of the gotten random vibration time domain signal. The result shows that the accuracy and error of PSD between AR model and the given function are within the range of the permitted value. And random vibration time signal obtained by using the redesigned FIR filter can meet absolutely the precision demand beforehand in the simulation and test.