Papers by Author: Jin Ji Gao

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.

Abstract: By analysis of the reasons such as maladjustment, vibration and long balancing time which from existing motor-driven bi-weight balancer; we propose solutions and apply them into a new design of magnetic-driven bi-weight balancer. By means of analyzing the bi-weight balancer system, we have raised the rules for optimum movement of the balancing weight and its judgment principles. We have summarized the maladjustment-free control algorithm of bi-weight balancer, carried out simulation experiment verification. The results show that the mobile strategy can effectively improve the quality of auto-balancing and achieve the purpose of no maladjustment, no oscillation and short balancing time.

Abstract: The rotor mass imbalance is main reason of rotating mechanical vibration. A new dynamic balance weighting method for single-disk rotor system based on phase difference mapping is presented. Firstly, the influence coefficient method and its characteristics are analyzed in detail. Secondly, the equivalent phase difference mapping relationship between incentive and vibration response for single-disk rotor system is proved by differential equations and Laplace transform theory. Finally, a specific application instance is showed. The new method is simple and easy to peel the phase coupling relationship between incentive and response, which can be used to guide dynamic balance weighting for single-disk rotor system on site.

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: 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: Animals possess the function of self-recovery for adapting the change in their living conditions. Can machinery, by bionic design, just like animals, also possess the function of self-recovery for making itself free of fault, or for eliminating fault automatically during operation In this paper, a new theory of Engineering Self-recovery is discussed, which could provide theoretical basis and new methodology for creating a new generation of machinery with fault self-recovery function. The engineering self-recovery theory is different from engineering cybernetics. Engineering cybernetics endows machinery with purposive behavior which originally is one of animal’s common characteristics, while engineering self-recovery theory endows machinery with the new function of fault self-recovery which originally is another one of animal’s common characteristics. Under the guidance of engineering cybernetics, the automation of machinery has come true. While under the guidance of engineering self-recovery theory, a new generation of machinery with the new function of fault self-recovery could also be realized. The self-recovery system, which can provide fault self-recovery force to restrain fault force, is investigated in detail. Based on fault mechanism and risk analysis, and by bionic design, a fault self-recovery system, which is a dynamic system to store, supplement and transfer the self-recovery force, is endowed to a machine with the ability to maintain the machine in a health state. Also, the research in engineering application of the new concept, fault self-recovery, is on the way. As an example, the new concept centrifugal compressor with fault self-recovery function is discussed here with axial displacement and flow induced vibration fault self-recovery as examples to show the steps of fault self-recovery system construction such as fault mechanism, necessity, determination, possibility, fault tolerance, limitation and execution.

Abstract: In this paper, a new method for time-varying machine condition monitoring is proposed. By Choi-Williams distribution, the interference terms produced by the bilinear time-frequency transform are reduced and the fault signal is processed by the correlation analysis of the Choi-Williams distribution. For machine fault diagnosis, both the feature extractor and classifier are combined to make a decision. It is particularly suited to those who are not experts in the field. Satisfactory results have been obtained from a real example and the effectiveness of the proposed method is demonstrated.

Abstract: Nucleus prosthesis replacement is considered as an ideal solution to low back pain. The purpose of this paper is to predict the suitable material properties and shape for the nucleus prosthesis of Chinese people based on biomechanical analysis using three-dimensional (3D) finite element (FE) method combined with experiments. The results suggest that a pillow-shaped nucleus prosthesis made of the polymer biomaterial with a Young’s modulus of 0.1-100 MPa is qualified to replace the degenerated nucleus. Then under the guidance of the FE predictions, a novel nucleus replacement material of polyvinyl alcohol hydrogel was prepared; the mechanical experiment shows that it has a compressive modulus of 1.0-6.8 MPa over a strain range of 10-60 %. The finite element predictions and experimental results have implications for the nucleus prosthesis designs.