Papers by Keyword: Mechanical Failure

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Authors: Wen Li Zhao, Zhi Gang Wang, Zhen Qiang Huang
Abstract: A new model is introduced in this article with which high frequency weak signal could be detected from strong noise background effectively. And meanwhile the process is displayed perfectly by using computer simulation. It will play an important role in detecting high frequency signal concealed in noise .Which can be used in detecting fault condition signals of mechanical system.
Authors: Miao Shang, Guo Min Lin, Wen Guang Zhang, Fei Zhou
Abstract: The common failures of three-phase motor are described, the specific reasons of failure are analyzed, the treatment of common failures are illustrated, the motor repair methods are summarized, the troubleshooting process is pointed out, the developing direction of common troubleshooting is put forward. For saving production resources, improving the efficiency of enterprise's safety production and economic benefit, it has important guiding significance.
Authors: Hiroyuki Nakata, Akira Yamauchi, Shigeji Taniguchi, Ii Ryoung Sohn, Jin Won Choi, Kazuya Kurokawa
Abstract: Low carbon steels containing Si of 0.1 and 1.0 mass%, and 99.5 mass% pure Fe were oxidized in laboratory air and in a H2O-containing atmosphere at 1173 K. Acoustic emission technique was used to assess the temperature (TF) at which the first major scale failure takes place during cooling. TF of 1.0 %Si steel oxidized in the air was found to increase with an increase in the scale thickness and cooling rate, while TF of 0.1 %Si steel had almost no dependence on these parameters. Moreover, the values of TF of both the steels oxidized in the H2O-containing atmosphere are higher than those in the air. These differences are attributable to the cooling rate, scale structure, and eutectoid reaction. In general, higher cooling rate implies a higher strain rate and there may be a larger temperature gradient across the scale thickness, which additionally enhances the scale failure. The metallographic examinations revealed that eutectoid magnetite particles in the scales formed on 0.1 %Si steel coarsen as the cooling rate decreases and magnetite seam was formed at the bottom of the iron oxide layer. It is clear that the influence of magnetite precipitation increases as the cooling rate decreases and thus the stress in the scale increases.
Authors: Song He Zhang, Yue Gang Luo, Bin Wu, Bing Cheng Wang
Abstract: The RBF network was applied in the rotor system to realize the fault diagnosis aiming the mapping complexity between fault symptoms and fault patterns. It can overcome the problems of low learning rates of convergence and falling easily into part minimums in BP algorithm, and improve the precision of diagnosis. The normalized values of seven frequency ranges in amplitude spectrum were used as the fault characteristic quantity, the RBF network was trained to diagnose the faults of rotor system. The results show that RBF neural network is a valid method of diagnosis of mechanical failure.
Authors: Shigeji Taniguchi, Yuki Hanamoto, Junji Nakata
Abstract: The scale failure temperature (Tf) during cooling from 1173 K of low carbon steels containing Si of up to 2.1% was assessed by in-situ acoustic emission measurements and analyses including wavelet transform. In general, Tf lowers with an increase in the Si content for steels without S or P, indicating that the scales on higher Si-content steels are more resistant to thermal stress. This tendency becomes larger for higher cooling rate. Contrarily, Tf rises with an increase in the S, P or (S+P) content for 1% Si steels. This means that the scale failure is enhanced by the additives. S segregates at the scale/substrate interface and seems to enhance the partial scale separation. P is incorporated in the (FeO+SiO2) layer on the substrate and forms microspores at the interface to the FeO layer, and thus enhanced the crack initiation by providing the sites for stress concentration. Wavelet transform showed that the scale failure mode is mainly the following; local separation of the scale over a small area takes place first, and then cracking in the scale follows. For steels containing S or/and P scale cracking is the initial failure in many cases, probably because the stress concentration sites are already formed during the scale growth.
Authors: Amit Puri, Alexander D. Fergusson, I. Palmer, Andrew Morris, F. Jensen, John P. Dear
Abstract: This paper presents the experimental results obtained of flexurally loaded wind turbine blade cross section material. All material was extracted from a wind turbine blade box girder and testing was conducted in four point configuration. The aim was to gain an understanding of the structural integrity of this lightweight material as it deforms in flexure. To allow for thorough analysis, digital image correlation (DIC) was used to produce full field strain maps of the deforming specimens. Results highlight the capability of the DIC technique to identify regions of failure, as well as the aspects responsible for them. Overall, the results present a foundation for tests on larger substructure, and eventually integration into manufacturing and maintenance aspects of the industry.
Authors: Fei Fan, Wei Wang
Abstract: To detect circuit breaker mechanical failures that are still in their early stages in order to avoid more serious failures and ensure reliable and safety of the grid operation, we uses a type ZW17-40.5 35 kV circuit breaker to simulate three typical incipient mechanical failures about stagnation of the energy storage spring, the dowel on the connecting rod and the moving arc. This analysis uses a digital camera detection method to record the processes for normal circuit breaker opening and closing conditions and conditions under stagnation. Additionally, by using a specially developed software to extract travel, speed and acceleration of specific location in every frame, we can discover features of the mechanical failure from the resulting data. This article provides a basis for identifying characteristics of stagnation and state monitoring of circuit breakers.
Authors: Guang Pei Cong, Jin Ji Gao, Bing Hou, Jing Zhu, Bao Wei Zhang
Abstract: The risk- and condition-based dynamic inspection proposed to decrease losses and costs caused by accidents which is not only a decision-making and optimal method for inspection strategies, but is also a soft measurement system for fixed equipment safety status. In the risk- and condition-based dynamic inspection method, data collection is standardized to decrease the impact of personal factors on the data. Moreover, a procedure in which experts approve the data collected from plants is supplemented to amend error and supplement omission of data in time. A relevant inspection strategy is adopted based on the different damage types and its initiation and growth for the aspect of inspection decision-making. In the meantime, the cost-risk efficiency of the inspection is regarded as an objective function to optimize inspection strategies according to the risk status of equipment. Finally, a model is established to assess the frequency of in-service inspection and ensure equipment safety during the end of equipment life based on the fitted linear relationship between the corrosion rate and stress energy.
Authors: Tian Tai Li, Ming Zhang
Abstract: It is accepted that the water flux in/out of the shale during drilling is the key factor, which controls wellbore instability. This flow can be divided into two components:1) the hydraulic flow due to the difference between the wellbore and pore hydraulic pressure; 2) the osmotic flow due to the imbalance between activities of the shale and the drilling fluid. The former can be prevented by adjusting the wellbore hydraulic pressure balance in the well hole, while the latter is much more difficult to control . The water activity of shale is a controlling factor in many areas of drilling. It impacts all situations wherein the temperature or the stress state of a shale is altered such as in wellbore stability, drilling rate and hydraulic fracturing. This chemical “potential activity interaction” produces a mechanical failure due to the movement of water in/out of shales. In order to have no shale alteration, it requires that the chemical potential of each component must be the same in all phases. This is seldom the case. After a lot of studies the shale activity is shown to be a function of pressure and temperature. Results showed inverse relationship between the platelet distance and the shale water activity. This experimental method proves to be a reliable and efficient way for studying the relationships for the shale water activity, comfining pressure, temperature, and platelet distance.
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