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Digital monitoring and health diagnosis for mechanical equipment operation safety based on fiber Bragg grating sensor
Zude ZHOU, Desheng JIANG, Quan LIU
Front Mech Eng Chin. 2009, 4 (1): 5-14.
https://doi.org/10.1007/s11465-009-0011-3
This paper introduces fiber Bragg grating (FBG) based on a fiber optic grating sensor developed to be embedded on mechanical equipment for digital monitoring and health diagnosis. The theoretical and experimental researches on the new-style FBG sensor (FBGS) technology, high-speed demodulation, and data transmission are discussed. The transmission characteristics between the FBG and the detection interface, modeling and compensation method for online distributed multi-parameter digital monitoring and methods for data processing, synchronous sampling, and long-term dynamic digital monitoring using embedded technology are also presented. The acquired information by an FBGS can be used for the optimization of maintenance schedules and refinement of mechanical equipment design. It is a challenge to gather real-time data from components working at high speed and in a severe environment of high temperature, high pressure, and high rotation speed. Currently, there are no sensors or technologies available for digital monitoring and health diagnosis under this rigorous situation for use in mechanical engineering operation safety. As a result, this paper introduces an online distributed and integrated digital monitoring system and health diagnosis. The new principle and new method will contribute to modern measurements in science and technology, mechanical engineering, and large mechanical equipment operation safety.
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Robust control of XYZ flexure-based micromanipulator with large motion
Xueyan TANG, I-Ming CHEN
Front Mech Eng Chin. 2009, 4 (1): 25-34.
https://doi.org/10.1007/s11465-009-0004-2
This article describes the development of an XYZ flexure-based micromanipulator, with the features of decoupled kinematic structure, large motion range, high positioning precision, and fast response. The large motion range of flexure mechanisms is quantified by a given definition. Based on the given definition, large motion is achieved in the mechanical design of the XYZ-flexure parallel mechanism (FPM). To ensure high positioning precision and fast dynamic response, a hybrid control algorithm with both position control and vibration control are designed, using the H∞-theory. The controller strongly solves the three common problems of flexure mechanisms simultaneously, including unmodeled uncertainties, the external disturbances and vibration caused by inherent low damping.
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Application of metal magnetic memory test in failure analysis and safety evaluation of vessels
Yiliang ZHANG, Song YANG, Xuedong XU
Front Mech Eng Chin. 2009, 4 (1): 40-48.
https://doi.org/10.1007/s11465-009-0003-3
Metal magnetic memory test (MMMT), which is a new subject in the field of nondestructive examination, can determine regions of stress concentration by testing the distribution of the magnetic field of metal structures so as to effectively diagnose premature defects. MMMT and other test methods are applied in the study to put a propylene purifier of a temperature-jump accident and a leaked ammonia vessel through safety evaluation. Results are as follows: The margin of safety declines after the purifier is overburnt; several stress concentrations are observed within the overburnt area and the level of stress concentration rises after one-month operation; and overpressure operation of the purifier must be strictly avoided and carefully monitored during later operation. Cracks are observed on the ammonia vessel after one year’s service. Extremely high residual stress is the primary cause of cracks. After four years in service, the residual stresses existing in the area of the base metal and weld zone are still greater than 0.5sS, which results in numerous cracks due to stress corrosion. From the MMMT result of the ammonia vessel’s defects, it can be seen that the derivative of magnetic density (dHp/dx) is an important reference variable. Within the 31 leakage points, 67.7% of them whose dHp/dx values are more than 10, and 96.8% of them whose dHp/dx values are more than 8.
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CNC programming system for complex components based on KBE within integrated environment of CAD/CAPP/CAM
Shengwen ZHANG, Guicheng WANG, Liang ZHANG, Xifeng FANG
Front Mech Eng Chin. 2009, 4 (1): 97-102.
https://doi.org/10.1007/s11465-009-0007-z
To promote the research and development of modern digital and intelligent manufacturing technology and overcome shortcomings of computerized numerical control(CNC) programming for complex components, an innovative idea has been proposed to introduce knowledge based engineering (KBE) into the field of CNC programming within the integrated environment of CAD/CAPP/CAM. This paper constructs the architecture of CNC programming based on KBE within CAD/CAPP/CAM and explores the key technology of applying KBE to CNC programming — knowledge representation, knowledge acquisition, knowledge reasoning, and generalized knowledge base system of CNC programming. The integration of the CAD/CAM system and the CAPP system of enterprises has been achieved by taking the powerful CAD/CAM system of UG NX as a platform. The prototype system of CNC programming for complex components based on KBE within CAD/CAPP/CAM has been developed by means of UG/Open,VC++6.0, and SQL Sever 2000. Finally, a frame example, one of the complex components of a marine diesel, is presented, and the academic production and the intelligence of the system are verified.
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16 articles
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