Papers by Keyword: Vibration

Abstract: Resonant pavement breaker is an excellent technique to reform worn cement concrete pavement (PCC). When the frequency of the machine adjusted to the resonant frequency of the worn cement concrete pavement, the pavement will be broken to discrete blocks. For the full use of this technique, this article studied the dynamic properties such as natural frequencies and modalities of worn cement concrete pavements of national secondary road. FEM was used to discretize models of different damaged degrees. The influence of different damaged degrees on natural frequencies and modes was studied. It was discovered that the new cement concrete pavement’s frequency was bigger than worn ones, and the modes were influenced by the damage locations and their degrees, the more worn, the more irregular.

Abstract: The main aim of this work is to identify the natural frequency of mild steel sandwich shaft disc system. An experimental evaluation is completed to evaluate the natural frequency and damping response of mild steel sandwich shaft disc system using Lab VIEW 8.5 software and National Instrument’s data acquisition (DAQ) system. The validation of the experimental results carried out using ANSYS 13.0, a finite element analysis software package. In addition, the effect of shaft thickness, disc thickness, shaft length variation, second, third, four and five systems also studied. The outcome of the results show that the increase in the parameter values have significant effect in the vibration responses of the mild steel sandwich shaft disc system which provide very much helpful information for the designers and researchers.

Abstract: Chatter is an unwanted phenomenon in metal cutting that involves violent vibrations of the cutting tool resulting in marked reduction in tool-life and increased roughness of the cut surface. Researchers have shown that chatter occurs due to resonance of the machine-tool-work system‘s natural frequency with that of the secondary saw teeth chip formation. This work investigates the modeling and free vibration analysis of a SANDVIK steel turning tool holder (DSSNR2525M12) set at 50, 70, 100, and 120 mm overhang, with a SANDVIK COROMANT titanium nitride coated carbide insert. The simulated free vibration data is compared to those obtained via experiments. The results show a correlation between simulated and experimentally obtained data for the tool holder set at the 50 and 70 mm. However there is a large discrepancy in results for the 100 and 120 mm overhang cases. This latter difference is unavoidable, due to the experimental test setup whereby the tool holder is clamped within the fixture with only 2 pins as opposed to the more rigid boundary condition applied to the finite element model, whereby the whole holder length within the carriage is rigidly supported at the element nodes. Hence the discrepancy is accentuated as the overhang is increased. This study is part of an ongoing research that aims at modeling and simulating the turning process itself, with the ultimate goal of providing off-line simulation and prediction of chatter.

Abstract: In order to avoid the damage of structure caused by the vibration, the natural frequency and vibration mode figure of the stiffness characteristics of the hoist’s structure should be analyzed. Modal analysis method is presented for solving above problem, and the first 6 order natural frequencies in different working conditions have been calculated in this paper. Vibration mode figure of structure system have been simulated corresponding to the first 6 order natural frequencies based on ANSYS. It is shows that the external excitation force have a great influence on the top of the free end when the cage moves to a different location. So, in the actual construction, the stiffness of top free ends connected tie-in device should be strengthened, therefore the system stability will be improved.

Abstract: The operation condition of the rotor system is strong nonlinear state; even with severe breakdown, weak nonlinear state appears; due to the nature of the rotor system is nonlinear. The system of the weak nonlinear state could mutate for strong nonlinear state. So the rotor system of weak nonlinear state vector in the system analysis and fault diagnosis is very important. Therefore, this paper analyzes universality of weak nonlinear of the system. It introduces segmentation system displacement vector into two little freedom of time to approximate equation system vector into a order system method.

Abstract: This paper introduces the working principle of the micromacined gyroscope, and establishes the drive equation of it. By solving the differential Equation, the analytical solution and the amplitude-frequency characteristics of the driving mode are obtained. By the visual measurement based on high-speed photography and the post image processing, it measures the vibration of the drive mode of the micromachined gyroscope. And it puts forward a novel displacement detect algorithm that based on the image processing, and with Matlab it verifies the analytical solution and the amplitude-frequency characteristics of drive mode of the micromachined gyroscope. This helps the study on the vibration of the micromacined gyroscope, and provides a new way to measure MEMS.

Abstract: Rolling element bearings are widely used in various rotary machines. Most rotary machine failures are attributed to unexpected bearing faults. Accordingly, reliable bearing fault detection is critically needed in industries to prevent these machines’ performance degradation, malfunction, or even catastrophic failures. Feature extraction plays an important role in bearing fault detection and significant research efforts have thus far been devoted to this subject from both academia and industry. This paper intends to provide a brief review of the recent developments in feature extraction for bearing fault detection, and the focus will be placed on the advances in methods for dealing with the nonstationary characteristics of bearing fault signatures.

Abstract: Several solutions have been proposed to mitigate the vibrations of stay cables in bridges, which are subjected to wind, rain and traffic loads. One possible solution relates to the use of semi-active devices, such as the ones based on magneto-rheologic fluids. These devices need guaranteed electrical power, together with computational effort and technical attention. In contrast, shape memory alloy (SMA) wires were studied for application as passive elements. In the present work, the properties of SMA that are required to realize dampers provided with an appropriate reliability are discussed. In particular, the fatigue/fracture life of the SMA wires and the thermal effects induced by both external temperature and the self-heating process are studied. The SMA dampers were applied to stayed cables of realistic size and tested in "facilities." Namely, the cables No 1 of 45 m length available at the ELSA-JRC in Ispra, Italy, and the 50 m cable of IFSTTAR near Nantes, in France, were considered. The experimental results establish a reduction of the vibration amplitude to one half or less than the one observed in the un-damped case. Furthermore, the installation of the SMA dampers causes an increase of the cable frequency. Performing a Windowed Fourier Transform or a Wavelet Transform analysis the evolution of frequency with the signal amplitude was studied. The change of amplitude produces a change of stiffness in the SMA. The adoption of an appropriate phenomenological model of the hysteresis cycle permits to perform numerical simulations using standard Finite Elements Analysis tools such as, for instance, the ANSYS software.

Abstract: To treat gear pair vibration due to internal excitation, an active internal gearbox structure near the gear pair is developed based on an active shaft transverse vibration control concept in the effort to tackle the gear excitation problem more directly. A controller of the FxLMS algorithm combined with frequency estimation technique is designed. And it is evaluated based on the experimental setup of the active gearbox vibration control system in contrast to fuzzy-PD controller. The experimental results show that 9.94dB attenuation in the gearbox housing vibration response can be achieved at the first gear mesh frequency by FxLMS controller, but only 5.62dB attenuation by fuzzy-PD controller. Besides, the insufficient effect at 210.8Hz and 216.2Hz is caused by typical out-of-band overshoot.

Abstract: Abstract. The multi-body dynamics simulation model of the hybrid system with a flexible shaft was established through rationally simplifying the system structure of a parallel hybrid system, assembling the flexible shaft, pulley, piston assembly , rod assembly and the rotor shaft according to the actual constraints, and adding the appropriate connections. The engine cylinder pressure reconstruction model and the motor vector control model were established in MATLAB as system shafting incentives. The simulation analysis of the dynamic characteristics of the system shafting was carried out in the boost mode of the hybrid system. The results show that: the shaft torsional vibration and bending vibration have happened when the hybrid system is running, and the engine cylinder pressure change was the main factor which caused the shaft vibration. Torsional vibration occurs mainly near the even multiple of the frequency of the shaft rotational frequency, and the torsional amplitude decreases gradually with the increase of resonance frequency; radial vibration occurs mainly in the range of 0 to 3 times the rotational frequency.