Applied Mechanics and Materials Vols. 105-107

Abstract: In this paper, a multi-fractal algorithm for vibration signal fault diagnosis is proposed to compute the multi-fractal dimension (D_q) automatically and perform the fault diagnosis accurately. This extended G-P generalized multi-fractal dimension algorithm is based on the qth-order correlation integral and the Grassberger-Procaccia (G-P) mono fractal correlation dimension algorithm. Experiment results verify the feasibility and effectiveness of the proposed algorithm. The obtained D_q unambiguously identifies the vibration signals sampled at the various states and provides more information of the vibration signals than the mono fractal correlation dimension . Hence it should be a more effective tool for vibration signal fault diagnosis. The analysis also indicates that the fluctuation amplitude of D_q is related with the frequency component distribution of the vibration signal.

Abstract: The system uses GRAP in Grey Theory to conduct fault diagnosis of fan and chooses LabWEV for software platform, developing a set of system aiming at fault monitoring on line and diagnosis of mine fan in order to guarantee the running state of fan continuously and efficiently . This system has functions of monitoring on line,fault diagnosis,fault warning,data storage, history inquiry and so on.

Abstract: To meet the requirement that continuous monitoring the mine special gear box, an embedded health evaluation system was designed in this paper. The software and hardware components of the system were described. The reasoning mechanism of expert systems used in the system was proposed. The system can report the whole machine health status based on crest factor, kurtosis and various bands. And the system is helpful for guiding equipment management, maintenance and maximizing efficiency of assents.

Abstract: Analysis of the study based on the Working principle of machine isolators-flexible foundation system which combines with multiple exciters and sensors, an MIMO active vibration isolation test model is constructed. In addition, the choice of system device and the distribution position of the vibration isolators and sensor are revealed and analyzed. Ultimately the Pilot scheme of the MIMO active vibration isolation Pilot scheme is confirmed.

Abstract: There are some problems in the control for a large flexible spacecraft on orbit such as the coupling, destabilization, and performance of the control system. To solve the problems, an active tuned mass damper (ATMD) is developed utilizing the piezoelectricity smart material, and an optimal output feedback control strategy is proposed based on the positive position feedback (PPF) method. The numerical simulations show that the developed ATMD/PPF method can suppress the flexible structural vibration induced by disturbances effectively. Using the method, the stability of the control system can be ensured and a good performance can be maintained even in case that the ATMD is in failure.

Abstract: In real life many agencies are using the flexible foundation as a base of support, such as ship hull or deck, the chassis of car, and machine tools work on stairs. With the traditional theory, the mathematical model between machine and based simplified as single-degree-of-freedom, assuming foundation is a rigid, and many investigate for a single machine, ignoring the dynamic coupling of base and the coupling characteristics between vibrators. This paper build a dynamics model with flexible basis and multiple machines, it’s multi-degrees-of-freedom model. The foundation is flexibled. On this basis builiding a model about multiple machines, flexible foundation and vibration isolation system. This paper resolve to the problem of the machine work on stair, research the system include vibrator, actuators, and flexible foundation. Using Lagrange equation deduce dynamics equation. Express every factor in eqution,deduced the state and space expression.Take prepare for optimal and system simulation.

Abstract: Aero-engine rotor system is the core component of engine. Aim at difficulties of fault diagnosis of engine rotor system, a method to detect the fault feature is proposed, which is based on recurrence plot (RP) and recurrence quantification analysis(RQA) by research of the characteristics and the mechanism of faults. An experiment is used to detect the fault of rotor system by using this new method. The results showed that the RQA is an effective way to extract features from vibration signal and by the use of quantitative features it is possible to identify and classify different types of rotor. Comparing with classical statistical features, the proposed algorithm has better classification rate. The research will be helpful in the further study of fault diagnosis of rotor system.

Abstract: Leakage of ship pipeline system has become a great hidden danger, which affects safe operation of ship and causes environmental pollution. In order to isolate leaking pipeline safely in emergency conditions, Real-time monitoring of ship pipeline system leakage is very important. In this paper, the real-time models of ship isothermal and thermal pipeline were established with a set of equations which is running synchronized with the actual execution pipeline, and the real-time model method was used to monitor ship pipeline system leakage. If the difference between measured values and calculated values is greater than a certain range, pipeline leakage is identified. The location of leakage is calculated based on pressure gradient. Only pressure, flow and temperature of the first and second end of the pipeline were needed, can this method achieve leakage detecting and locating. According to the analysis and verification from the experimental data, this method has high leakage resolution and positioning accuracy.

Abstract: In the present study, the modal parameters of cracked plain cement concrete beams have been studied theoretically. A crack in a beam element introduces considerable local flexibility, which has been expressed by local flexibility matrix, the dimension of which depends upon the numbers of degree of freedom considered. An approach based on linear fracture mechanics theory has been used to find flexibility matrix for the cracked element. The FEM program has been developed for eigen-value problems to determine the modal parameters of the cracked beams. Changes in natural frequencies and mode shapes between the damaged and intact beam have been observed. Numerical studies are performed by considering simply supported beam with single and multiple cracks at different locations with different crack depths.

Abstract: With the C# language and Access database, Building Foundation Pit Monitoring Information System (BFPMIS) was developed. At the process of developing the excavation monitoring system, the design of the system data structures and the data types are discussed. The excavation monitoring system contains main data structure and assistant data structure. The data structure, data element and data type of projects, bids, sections, monitoring point types, point property, alert values, bore information, pile information and beam information are analyzed emphatically. The application of the tree structure in the main data structure is introduced. And the monitoring points are classified according to the monitoring objects to describe and store the monitoring data. The system set orange alarm and red alarm to every monitoring point.