Advanced Materials Research Vols. 291-294

Abstract: This paper presents a condition diagnosis method for a roller bearing using the ant colony optimization (ACO). The symptom parameters in frequency domain are considered for reflecting the feature of vibration signals measured under different states. The states identification for machinery diagnosis is converted to clustering problem of different states. The distance-based diagnosis method, which distinguishes the machinery states by comparing the distance, is proposed using the ACO clustering algorithm and utilized to detect faults and recognize fault types. The analysis results demonstrate that the proposed method can recognize the faults types effectively.

Abstract: This paper takes marine Kingsbury sliding thrust bearing as the research object and conducts the finite element dynamic analysis with the aid of ANSYS software. On this basis, the acoustic boundary element model of a sliding thrust bearing shell is established with the ANSYS dynamic analysis results as the boundary excitation conditions. Besides, the radiated sound power of the shell is calculated by indirect boundary element method in SYNOSISE software. The influence of different condition parameters on the radiated sound power of the shell is perceived through the analysis of several rotation-thrust conditions. As for the special structure of this kind of sliding-thrust bearing, this paper states the impact of the supporting structure performance parameters, the pad number and damp of shell on the shell radiated sound power. The optimized measure for the supporting structure and the plan concerning the pad number’s selection lays the theoretical basis for damping and noise-reducing research on marine sliding-thrust bearing and its rotor system.

Abstract: This paper presents a new rotordynamic measurements conducted on a test rig for evaluation of multiple rings of labyrinth seals. Considering the tilting motion of cylinder occurs in experiments, the impedance matrix of cylinder system is obtained first. An equivalent seal force identification model is set up for multiple seals based on double plane balance theory of rotor dynamics. The resultant seal forces are calculated on two end planes of the cylinder, and resolved to multiple sections that seals located. A frequency domain identification method delivers the test seals stiffness and damping coefficients. Compressed air inlet tests were run from 1000 rpm-2200rpm, 0.1-0.6Mpa supply pressures were used. For each ΔP test condition, the static eccentricity ratio ε=e/Cr is range from zero to approximately 0.6. Results show that 8 rotordynamic coefficients increase almost linearly with inlet/outlet pressure ratio. Increasing eccentricity ratio weakens the stability of seal-rotor system obviously.

Abstract: Through woodworking four-side planer vibration test, this article studies its dynamic characteristics and dynamic response to identify the vibration magnitudes law of each feed roll shafts of the four-side feed beam; then finds the natural frequency and damping ratio of the feed beam and lathe bed; obtains the mathematical model of feed roll shaft vibration magnitude changing with the feed rate U under different process thicknesses. The analysis of feeding quantity and the rationality of lathe bed from the perspective of vibration design supplies the designs and operation staff with reference data.

Abstract: In this paper, the eco combination yarns of bamboo carbon fiber and cotton fiber which have the same yarn count are used to knit four structures by computerized flat knitting machine such as plain jersey, half cardigan stitch, milano rib stitch and half-milano rib stitch. Through testing, comparing and analyzing on drape, air permeability, moisture absorption and bursting strength, the results show that the plain jersey knitted products are the best.

Abstract: The effects of high density ultrasonic field coupling on the microstructures and properties of Al-12Si alloy were investigated. It is shown that when the melt undergoes ultrasonic coupling processing prior to solidification, the nucleation rate of liquid phase can be raised to make α(Al) dendrite transform towards near equiaxed grains, the growth of Si phase is restrained and eutectic Si microstructure is refined due to acoustic streaming effect and thermal mechanism; When the melt undergoes ultrasonic coupling processing during the melt solidification, large degree of supercooling is produced in the liquid phase in the solidification interface front edge to reduce the critical radius of crystal nucleus and critical work of nucleation and break up, rupture by melting and refine the Si phase to improve obviously the strength of Al-12Si alloy due to its cavitation effect, acoustic streaming action and heat undulation; The crushing effect of ultrasonic coupling on Si phase occurs mainly during the crystallizing solidification and threshold sound intensity exists.

Abstract: An approach of multi-resolution correlation filtering was presented to identify the transient responses of acoustic emission (AE). Two techniques were combined to avoid computational difficulties and obtain high identification efficiency. Wavelet multi-resolution analysis was first employed to decompose the original signal into a set of levels that correspond to different frequency bands. Using Mallat fast algorithm, the reconstructed signal in a certain level was obtained, which retained the main information of the original signal. These resulted in a considerable reduction in the data and a reduction in the computational time to perform correlation. Technique of Laplace correlation filtering was then used to identify frequency and damping characteristics of the reconstructed signal. Computational results demonstrated the accurate identification of the transient response of both a synthetically generated signal and actual acoustic emission testing signals. As a result, the approach of multi-resolution correlation filtering could be effectively utilized in AE detecting.

Abstract: In order to reduce the meshing noise of silent chain drive, a new concept of the chain (silent chain including silicon fluorine rubber link plate) was proposed. It could change the meshing contact state by changing the shape of traditional steel chain plate and arranging the silicon fluorine rubber link plate reasonably, which reduced meshing impact, so the meshing noise was reduced. Through the platform contrast test, a noise test was made with different types of silent chain at the same speed, and the results shown that the silent chain including silicon fluorine rubber plate drove more smoothly than other silent chains, the level of noise was reduced 2dB～3dB, which verified the fact that the silent chain including silicon fluorine rubber link plate could reduce noise.

Abstract: Bearing faults signal is very weak under a low rotating speed, and therefore fault diagnosis for bearings under a low rotating speed, is more difficult than under a high rotating speed. The wavelet analysis technique is adopted for fault diagnosis of rolling element bearing under low rotating speed. This work also acquired vibration signals and acoustic emission signals from the rolling bearing under low speed respectively, and analyzed the both kinds of signals for diagnosing the typical bearing faults contrastively.

Abstract: The vibration occurring in cutting process is a very harmful phenomenon, which destroys the surface finish and dimensional integrity of workpieces and quickens the wear of cutting tool. Cutting chatter can be suppressed or reduced by applying the method of suppressing chatter by variable speed cutting. In order to investigate the effect of variable speed parameters and cutting conditions on suppressing the chatter in face milling, the tests have been conducted.The results have shown that cutting with variable spindle speed cutting in face milling will suppress the development of chatter. If chatter occurs in cutting process, the vibration amplitude of variable speed cutting can reduce by 3-6 times lower than that of constant speed cutting, as long as the variable speed parameter are selected suitably.The values of speed variation amplitude Δn/n_o and speed variation frequency f_n of spindle speed trajectory parameter have great effect on suppressing chatter, Δn/n_o = 15- 20% and f_n = 0.4 - 0.5Hz are suitable.