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Research of dynamic effects in the process of operation of linear comparator
Get PDFTopicality of the problem is the fact that in the process of increasing the quality of line scale gage calibration vibrations have substantial influence. In order to assess vibration influence we need to solve a lot of science and engineering tasks. To accomplish mathematical analysis we confronted with a lot of difficulties in creating of the analytical model and in finding of the values of coefficients. For this solution we need to make thorough analysis of the means for line scale measurements, because most of the coefficients we could only find by making experimental measurements and processing of their results
Simplified computational method for mooring forces of mooring systems
Get PDFThe most common marine mooring systems of floating structures are taken as the numerical models. The effects of wave parameters and structural parameters on the wave forces are studied. A simplified formula of wave forces is established and the valuing ranges of key parameters are determined. Results obtained by the simplified computational method show great agreement with those obtained by numerical simulations and physical modelling experiments. The mooring forces can be obtained easily and efficiently by the proposed method
Measurement of stability of a pipe system with flowing fluid
Get PDFThe two dimensional system of coupled vibrating pipes is investigated. The model of a pipe system consisting from two dimensional beams is employed. The problem of stability because of the reduction of stiffness caused by the flow of fluid is solved and the stability eigenmodes are determined. The places where the deflections of the stability eigenmodes are large are recommended for the location of measurement devices
Experimental study on the bursting vibration effect in ground surface of large-diameter and high-pressure steel pipe
Get PDFIn order to study the harmful effects of seismic waves generated by the bursting of large-diameter high-pressure gas pipelines, through two half-buried three-pipe air bursting tests and with the use of three-vector velocity sensors, vibration speeds in three different directions when pipe bursting seismic waves propagate along the surface can be obtained. Propagation characteristics and spectral characteristics of pipe bursting seismic waves can be gained by comparison and the Fourier transform analysis of the autocorrelation function. According to results, major seismic wave energy concentrates in 0-100 Hz frequency range where the maximum power spectral density corresponds to a frequency, which is less than 10 Hz and has strong destructive impacts on the buildings around the pipelines. Linking test results to safety threshold that have been studied allows some data to be acquired. When natural gas pipelines are under construction, the safe distance between parallel buried pipelines is 60-70 m; from pipelines to traffic tunnels and mine workings the safe distance is 50-100 m; from pipelines to the buildings it is100-240 m
Study on the optimization system of supporting schemes for foundation pit
Get PDFAt present, there are various supporting schemes for foundation pit that could be adopted in actual projects; however, there are also certain differences in construction cost and applicability of different schemes. To guarantee reasonable and efficient choice of supporting schemes for foundation pit, it is necessary to implement selection of supporting schemes purposefully. This essay discusses mainly the optimization system of supporting schemes for foundation pit. Through analysis of the affecting factors of supporting schemes of foundation pit, comprehensive optimization system of supporting schemes for foundation pit has been constructed, optimization model of supporting schemes based on TOPSIS has been created and comprehensive optimization system of supporting schemes for foundation pit has also been established
Modal analysis of the certain membrane disc coupling
Get PDFThe membrane disc coupling has the ability to transmit higher power under high-speed rotation. It also has the ability of compensation angular and radial displacement. The finite element model of the coupling was established and vibrational characteristics were analyzed. The modal experiments were carried out with hammering method, the modal parameters were obtained and the correct of the simulations was verified under the same constraints with the FEM model. The results showed that simulating results agreed well with that of the experiments
Identification of open crack of beam using model based method
Get PDFThis research aims at identifying the position and depth of the open transverse crack of the beam using the model based method. The stiffness matrix of the cracked beam element and the basic principle of the model based method are introduced. It is discussed to estimate the generalized displacement of all nodes of the beam by the measured displacements of a few degrees of freedom. The relative change rate of the equivalent external load between the intact and cracked elements is compared with that of mode shape, nature frequency and displacement amplitude between the intact and cracked beam. The position and depth of the crack are identified by the model based method in two cases. In first case, the measured displacement is assumed not to include noise. The identification results based on the actual displacement and rotation of all nodes are compared with the results using the estimated generalized displacement. In second case, the measured displacement includes noise and the generalized displacement of all nodes is estimated by the displacement of two measurement points. The simulation results shown there is no error to identify the position, the relative depth identification error of the crack with 1 μm depth is 2.34 % without noise, and the relative depth identification error of the crack with 200 μm depth could be down to about 5 % with the energy signal to noise ratio being about 7.00 before denoising
Multiple-input multiple-output proportional-integral-proportional-derivative type fuzzy logic controller design for a twin rotor system
Get PDFA new multiple-input multiple-output (MIMO) proportional-integral-proportional-derivative (PIPD) type fuzzy logic controller (FLC) is proposed for pitch and yaw motion control of a twin rotor system in this study. A fuzzy feedforward compensator for gravity effects on pitch motion of the twin rotor is also designed. Fuzzy logic was preferred for controller design since it can be applied to nonlinear systems and do not require the mathematical model of the system. The twin rotor system is a highly nonlinear system that includes coupling effects between pitch and yaw motions and has similar dynamics to that of a helicopter in certain aspects. Experimental results demonstrate that the proposed controller is able to stabilize the system along with good trajectory tracking performance
Vortex signal detection method with stochastic resonance based on adaptive coupled feedback control
Get PDFThe control of stochastic resonance is the key to its application. A feedback method is proposed to control the generation of stochastic resonance with coupling, and then enhance resonance effect with the optimization of control parameters. The method is applied to detect vortex signal. Artificial fish swarm algorithm is used to adjust the control variables adaptively, thus the optimal control of the coupled bistable stochastic resonance is realized. Numerical simulation and experimental results manifest that by this means the resonance effect can be enhanced effectively, the signal-to-noise ratio (SNR) of vortex signal can be improved, and the vortex shedding frequency can be obtained accurately
Experimental study on high frequency chatter attenuation in 2-D vibration assisted micro milling process
Get PDFRegenerative chatter is an unstable form of self-excited vibration in the machining process, and it is one of the main obstacles which limit the productivity and the surface quality of the component. This paper investigates the effect of 2-D vibration assistance on high frequency regenerative chatter in the micro milling process. External vibration is applied on the workpiece in a range of frequencies and amplitudes using the piezoelectric actuators. The chatter vibration is monitored using the sound pressure signal measured by the microphone. The chatter amplitude with vibration assistance in 1-D (feed or normal direction) and 2-D is studied. The effect of the frequency and amplitude of the vibration assistance on chatter amplitude is analyzed. It is concluded that the vibration assistance is able to effectively attenuate the high frequency chatter by modifying the dynamic chip thickness and adding process damping in the micro milling process