Papers by Author: Chang Qing Su

Abstract: On the basis of the dynamic equations of rotor system with pedestal looseness, the random response method of rotor system with pedestal looseness is researched. The method is based on stochastic perturbation theory and the Kronecker algebra, matrix calculus and random perturbation are used. The reliability model of rotor system with pedestal looseness is proposed. The reliability of rotor system with pedestal looseness is obtained by way of statistical fourth moment method, random perturbation technique. Numerical results are also presented and discussed.

Abstract: Parameter uncertainty of general systems is inherent in most engineering problems. Based on the regularity of oil whip and resonance for rotor system, the reliability problem of rotor system with oil whip and resonance is studied by applying random perturbation technology and reliability theory considering the correlation of the multi-order natural frequency. The reliability mode and the failure probability of rotor systems are defined. The second-order joint failure probability is obtained by using the numerical integration method. The presented method provided the theoretic basis for the reliability design of the rotor system. A numerical example demonstrated that the proposed method is effective.

Abstract: Large flexible clamping tooling stent is mostly volume which wasted a lot of materials. Structure size is to optimize the details of the flexible clamping tooling optimization design. It is by changing the properties of the structural unit - for example, the shell element thickness, the cross-sectional properties of the beam element, the stiffness of the spring element and the quality of the mass element to achieve a certain design requirements (such as stress, mass, displacement)。This design is use of hyper mesh software to optimize the size of the pillar on the flexible clamping tooling bracket. The pillars can be as a shell for analysis, a stress constraint is specified materials at least, reduce the weight of the parts, save the cost of production to achieve the optimization purposes.

Abstract: Oil whip phenomenon is the common fault in rotor-bearing system. The reason why oil whip happens often has been researched in high-speed rotor-bearing system. But in practice engineering, due to the requirement of work condition, oil whip cannot be avoided all the time in rotor-bearing system. The paper is based on the relation criterion of oil whip happens in rotor-bearing system, the reliability mode and system reliability of oil whip are defined, and the reliability analysis method for avoiding oil whip in rotor-bearing system is carried out. The effect on reliability sensitivity of random parameters is studied. Numerical results are also presented and discussed.

Abstract: The material properties and geometry of rotor system are random parameters because of the manufacturing environment, manufacturing and installation errors and other factors. Based on the reliability design theory, the reliability sensitivity technique and the robust design method, the frequency reliability robust optimization method of rotor system is extensively discussed. The frequency reliability sensitivity is added to the reliability-based optimization design model of rotor system. The frequency reliability robust design is described as a multi-objection optimization. The method presented provided the theoretic basis for the reliability robust design of the rotor system. A numerical example demonstrated that the proposed method is effective.

Abstract: Based on Saddlepoint Approximation method and sensitivity analysis method, reliability sensitivity analysis for differential expansion of steam turbine with random parameters are studied. On the premise of the probability distribution of random parameters, using Saddlepoint Approximation method, probability density function of limit state function of differential expansion of steam turbine is obtained. The result of Saddlepoint Approximation method is very close to the one of Monte-Carlo, and the computing speed is fast. Then, the sensitivity analysis method and probability density function were employed to discuss the variation regularities of reliability sensitivity and the effect of design parameters on reliability of differential expansion of steam turbine is analyzed.

Abstract: Based on the reliability-based optimization design theory, the reliability sensitivity technique and the robust design method, the reliability-based robust design of rubbing rotor system is extensively discussed and a numerical method for reliability-based robust design is proposed. The reliability sensitivity is added to the reliability-based optimization design model and the reliability-based robust design is described as a multi-objection optimization. On the condition of known first four moments of basic random variables, the respective program can be used to obtain the reliability-based robust design information of rubbing rotor system accurately and quickly using the fourth moment technique. According to the numerical results, the approach proposed is a convenient and practical reliability-based roust design method.

Abstract: The reliability analysis for differential expansion of steam turbine is discussed extensively. The ultimate state equation of differential expansion of steam turbine is proposed according to stress-strength interference theory. Based on the premise that the probability distribution of random parameters has been known, the differential expansion of steam turbine is analyzed by saddlepoint approximation method. The probability density function and cumulative distribution function of the ultimate state equation are accurately and quickly obtained by the way of saddlepoint approximation and, as a result, the saddlepoint approximation method is proved accurate with high computing speed in comparison with the Monte-Carlo method. Therefore, the application of the saddlepoint approximation method is accurate and efficient.

Abstract: The rubbing phenomenon occurs when a rotating element eventually hits a stationary part of the rotating machinery. Increasing the rotor speed and decreasing the radial clearance between the rotating and the non-rotating parts can enhance the performance of the rotating machinery. This leads to an increased risk of rubbing contact. Rotor rubbing is the source of numerous different phenomena, for example sub- and super-harmonic vibrations, amplitude jumps and rotor instability. So the reliability analysis and sensitivity analysis of rotor system with rubbing is important for design purposes. Reliability analysis can help the designer to establish acceptable tolerance on rotor system. Sensitivity analysis can help the designer to know which problem in rotor system with rubbing is being solved and how the solution may affect the design of rotor system for system correction and reanalysis. On the basis of the dynamic equations of the cracked rotor system model and with consideration of the random parameters including shaft stiffness and damping, disk damping, radial clearance and stator radial stiffness, the random responses of cracked rotor system are researched. The reliability and sensitivity analysis of the cracked rotor system with rubbing are studied. According to the discretization of random process and stress-strength interference theory, the transient reliability model of cracked rotor system with rubbing is proposed. The reliability for rubbing in cracked rotor system is obtained by way of statistical fourth moment method, Edgeworth series technique and first passage theory. Numerical results are also presented and discussed.