高速動(dòng)平衡機(jī)的隨機(jī)可靠性分析方法研究
[Abstract]:With the popularization of the concept of Engineering reliability, the reliability of mechanical equipment performance has gradually become a necessary performance evaluation index in the design, manufacture and use of equipment. Relying on the National 863 Project (2009 AA04Z419) "Reliability and Life Reassessment and Growth Technology of Typical in-service Major Equipments", this paper systematically and thoroughly studies the static and dynamic performance and stochastic reliability analysis method of high-speed dynamic balancing machine, with the high-speed dynamic balancing machine as the main analysis object, in order to make it possible for the rotating machinery major equipment. The mechanical system of high-speed dynamic balancing machine belongs to the category of rotor dynamics. Its mechanical research can be divided into two levels: one is equal stiffness pendulum part; the other is pendulum-bearing-rotor coupling dynamic system (referred to as pendulum-rotor system). For the research object, the balanced rotor is considered in the form of load; the latter also needs to consider the interaction between the balanced flexible rotor and the balanced flexible rotor. As a result, the performance of high-speed dynamic balancer will show many uncertainties, which makes the deterministic performance evaluation results can not reflect the real performance of mechanical equipment. Random uncertainty analysis and reliability evaluation are the main ways to deal with uncertain factors. In order to improve the margin of safe and reliable operation of high-speed dynamic balancing machine, in fact, high-speed dynamic balancing machine belongs to small sample high-reliability equipment, and usually has the characteristics of complex model, large amount of calculation, high non-linearity and high dimension. The main contents can be summarized as follows: (1) The static bearing capacity, static/dynamic stiffness characteristics and stress fatigue life of the equi-stiffness pendulum of high-speed dynamic balancer are studied. Firstly, the pendulum is established. The static finite element model of the frame is established, and the static load-bearing capacity and radial static stiffness of the pendulum under several typical tonnage rotors are analyzed. Then, the dynamic stiffness curve of the pendulum frame is measured based on the hammering method, and the current dynamic stiffness characteristics of the pendulum frame are analyzed in detail. Finally, the stress fatigue life of the main elastic support of the pendulum under several typical tonnage rotors is estimated based on the stress state of the pendulum under quasi-unbalanced force and the estimated first-order critical speed and unbalanced force amplification coefficient. (2) The beam element finite element method of the high-speed dynamic balancer is studied. Based on the modeling theory and the direct differential method of response sensitivity analysis, the equivalent stiffness damping coefficient formulas of the pendulum-bearing part are given, and the estimation formulas of the first-order critical speed and the unbalanced force amplification coefficient are deduced. After analyzing the defining parameters involved in the equation, the formulas for solving the sensitivity of modal eigenvalues and critical speeds to the defining parameters are given, and the hierarchical relations between the coefficients of the corresponding equations and the direct derivatives of the defining parameters are given. On the basis of these formulas, the first-order critical speed estimation formula based on a simple swing-bearing-rotor system model and the force amplification coefficient estimation formula under unbalanced load on the swing frame are derived. These formulas are very useful for the fatigue life estimation of the main support stress of the swing frame. Finally, the rotor motion of a 50 MW steam turbine is analyzed. (3) The rackwitz-fiessler method for space transformation of stochastic factors in high-speed dynamic balancing machine is studied. The forward-inverse transformation process and the correlation variation law of the rackwitz-fiessler method are discussed in detail. The enhanced R-F method is proposed. Firstly, the equivalent R-F condition and the corresponding correlation are given. Mathematical deduction proves the consistency between the positive transformation from physical X-Space to standard normal Y-Space in the r-f method and the equal probability edge mapping transformation in the nataf-pearson (n-p) method. Based on this conclusion, it can be concluded that the correlation variation formula of the equivalent normalization process in the r-f method is also derived by derkiureghian and Liu Finally, the computational complexity and efficiency of the enhanced R-F method and the N-P method are discussed. (4) Based on the copula theory, the rackwitz-fiessler method is improved and generalized, and the improved R-F method and the generalized R-F method are proposed respectively. Firstly, to overcome the shortcomings of the linear correlation coefficient, the basis method is proposed. Then, considering the Gaussian opula hypothesis in the traditional R-F method, a generalized R-F method based on the elliptic copula family is proposed. In order to make the first-order reliability method fit the generalized R-F method, a concept based on the most likely failure point in the unrelated standard sphere u space is proposed. The generalized first-order reliability index and the generalized first-order reliability method are given. Finally, the reliability of the main elastic support of the pendulum with infinite fatigue life is analyzed by means of an engineering example. (5) An adaptive MPP fast search algorithm, ahlrf method, is proposed, and the convergence proof is given. The efficiency of the algorithm is discussed. Firstly, on the basis of the existing MPP search method based on hlrf, a MPP search algorithm, ahlrf, is proposed to estimate the parameters of the algorithm adaptively by using the existing iterative information. It can be proved that ahlrf has global convergence and the convergence rate is at least linear. Eleven engineering examples are selected to validate the aHLRF method. Finally, the stress fatigue life of the main elastic support and the reliability of the stability margin of the rotor system at operating speed are analyzed by means of an engineering example. (6) The stochastic uncertainties of the critical speed and the unbalanced steady-state response of the high-speed dynamic balancer based on the spectral method are studied. Firstly, the error sources and the influence degree of the Karhunen-Loeve (K-L) expansion method based on the wavelet basis-Galerkin solution for Gaussian random field approximation are discussed. Based on the sub-sphere filling scheme, a programming scheme for automatically generating polynomial chaotic basis functions with arbitrary dimension and order is given in detail. In order to rewrite the right-hand-end term of the spectral stochastic finite element equation into the expression of polynomial chaotic basis expansion, a recursive implementation scheme is proposed. Finally, the uncertainty of the critical speed of the 50 MW turbine rotor dynamic balancing system is analyzed based on the non-invasive spectral stochastic finite element method, and the common unbalance between the random point unbalance and the distributed unbalance of the 50 MW turbine rotor dynamic balancing system is analyzed based on the embedded spectral stochastic finite element method. In a word, the static and dynamic performance analysis and stochastic reliability analysis methods of high-speed dynamic balancer are studied in this paper, taking into account the characteristics of complex model, large amount of calculation, high nonlinearity, high dimension and the fact that it belongs to small sample and high reliability equipment. The Rackwitz-Fiessler random space transformation method, the adaptive MPP search algorithm aHLRF method and the random uncertainty analysis method based on the spectral method are also very suitable for the random reliability analysis of other rotating machinery equipment.
【學(xué)位授予單位】:上海交通大學(xué)
【學(xué)位級(jí)別】:博士
【學(xué)位授予年份】:2014
【分類號(hào)】:TB114.3
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