Fault detection and isolation in nonlinear systems

This paper deals with fault detection and identification in dynamic systems when the system dynamics can be modeled by smooth nonlinear differential equations including affine, bilinear or linear parameter varying (LPV) systems. Two basic approaches will be considered, these apply differential algebraic and differential geometric tools.In the differential algebraic approach the state elimination methods will be used to derive nonlinear parity relations. In the specific case when a reconstruction of the fault signal is needed the dynamic inversion based approach will be investigated. This approach will also be studied from geometric point of view. The geometric approach, as proposed by Isidori and De Persis, is suitable to extend the detection filter and unknown input observer design approaches (well elaborated for LTI systems) to affine nonlinear systems.Beyond the development of the theory of fault detection and identification it is equally important to offer computable methods and to analyze the robustness properties against uncertainties. Both the observer based and the inversion based approaches will be elaborated for LPV systems that may offer computational tools inherited from linear systems and also allow to design for robustness utilizing results from robust filtering and disturbance attenuation.     

CFD analysis on the catalyst layer breakage failure of an SCR-DeNOx system for a 350 MW coal-fired power plant

Selective catalytic reduction as one of the secondary NO_x control technologies is widely used in industrial sources including coal-fired power plants and large boilers. The performance of an SCR-DeNO_x system is sensitive to the installment of its components such as turning vanes and hybrid grids. In this work, three-dimensional CFD simulations are carried out to analyze the breakage failure of an SCR-DeNO_x system for a certain 350 MW coal-fired power plant. Research results are consistent with the phenomena that occur in the industrial application. It reveals that the breakage failure in the industrial application is likely to be caused by the inappropriate installation of the turning vane 3 locating closest to the catalyst, especially the angle of the turning vane 3. The analysis further shows that the lifetime or the breakage of the catalyst layers depends highly on the gas velocity, the fly ash distribution and its particle velocity.     

Designing economic np control charts: A programmed simulation approach

This paper presents control charts models and the necessary simulation software for the location of economic values of the control parameters. The simulation program is written in FORTRAN, requires only 10K of main storage, and can run on most mini and micro computers. Two models are presented - one describes the process when it is operating at full capacity and the other when the process is operating under capacity. The models allow the product quality to deteriorate to a further level before an existing out-of-control state is detected, and they can also be used in situations where no prior knowledge exists of the out-of-control causes and the resulting proportion defectives.     

人工神经网络与失效评定图在压力容器安全评定中的应用

采用人工神经网络与失效评定图相结合的方法对压力容器进行安全评定,样本评定结果和Ｒ６ 失效评定图方法的评定结果一致,并对评定结果进行了参数敏感性分析,分析结果令人满意。人工神经网络为压力容器安全评定智能化提供了一个有效的手段。     

Modeling and characterization of dynamic failure of borosilicate glass under compression/shear loading

In this paper, we study the impact-induced dynamic failure of a borosilicate glass block using an integrated experimental/analytical approach. Previous experimental studies on dynamic failure of borosilicate glass have been reported by Nie et al. [Nie X, Chen WW, Sun X, Templeton DW. Dynamic failure of borosilicate glass under compression/shear loading – experiments. J Am Ceram Soc, in press.] using the split Hopkinson pressure bar (SHPB) technique. The damage growth patterns and stress histories have been reported for various glass specimen designs. In this study, we propose to use a continuum damage mechanics (CDM)-based constitutive model to describe the initial failure and subsequent stiffness reduction of glass. Explicit finite element analyses are used to simulate the glass specimen impact event. A maximum shear stress-based damage evolution law is used in describing the glass damage process under combined compression/shear loading. The impact test results are used in quantifying the critical shear stress for the borosilicate glass under examination. It is shown that with only two modeling parameters, reasonably good comparisons between the predicted and the experimentally measured failure maps can be obtained for various glass sample geometries. Comparisons between the predicted stress histories for different sample designs are also used as model validations.     

Fabrication and Characterization of Electrodeposited Ni-SiC-h/BN Composite Coatings

Ni—SiC—h/BN composite materials were prepared by electrodeposition technique with the dispersion of SiC（10 g/L） and h/BN nanosheets（10 g/L） in a nickel sulfamate electrolytic bath.Different ratio of sodium dodecyl sulfate（SDS） and cetyltrymethyl ammonium bromide（CTAB） surfactants were used to evaluate the effect of surfactants on the properties of the electrodeposited composite coatings.The coating samples were characterized by scanning electron microscopy,X-ray diffraction,Vickers microhardness test,scratch and tribology tests.The results revealed that the co-deposition of nanoparticles was significantly influenced by surfactants during electrodeposition process.Pyramidal or polyhedral nickel crystallites were observed at higher ratio of SDS/CTAB while smaller oval grains with refined surface morphologies were obtained at lower ratio of SDS/CTAB surfactants.In addition,wt%of particles co-deposition was increased,and Vickers microhardness,wear and coefficient of friction of the electrodeposited composite coatings were improved at increased CTAB and decreased SDS contents in the electrolyte during electrodeposition process.     

Failure of a 17-4 PH stainless steel sailboat propeller shaft

In this study, a 17-4 PH precipitation hardening stainless steel propeller shaft failed in use when installed in a sailboat working in a marine environment. Failure analysis was conducted on the propeller shaft. Results indicate that the failure was caused by the fracture of the propeller shaft by torsional fatigue and stress corrosion cracking (SCC). SCC progressed transgranulary in the martensitic matrix.     

空调风系统调试中的主要问题及其研究

空调风系统的调试工作对于系统建成后运行效果的好坏有着重要的影响,本文在分析国内调试工作现状的基础上对目前存在的几个主要问题进行讨论研究,包括进行四通局部阻力系数的确定以及计算机辅助调试系统的开发,研究的结果将有利于国内空调风系统调试水平的发展和提高.     

液压电梯用管道破裂阀管道失效模拟试验探讨

欧洲标准EN81-2：1998和美国标准ASMEA171-2000对液压电梯用管道破裂阀的使用和试验要求，按EN81-2：1998相关要求对管道破裂阀进行了全部管道失效模拟试验．并对试验结果进行了分析讨论。试验中发现相关标准对管道破裂阀的使用要求，试验方法和对试验结果的判定方法上有值得探讨之处，特提出共析疑。     

Stability analysis of vertical boreholes using the Mogi–Coulomb failure criterion

A main aspect of wellbore stability analysis is the selection of an appropriate rock failure criterion. The most commonly used criterion for brittle failure of rocks is the Mohr–Coulomb criterion. This criterion involves only the maximum and minimum principal stresses, σ₁ and σ₃, and therefore assumes that the intermediate stress σ₂ has no influence on rock strength. As the Mohr–Coulomb criterion ignores the strengthening effect of the intermediate stress, it is expected to be too conservative in estimating the critical mud weight required to maintain wellbore stability. Recently, Al-Ajmi and Zimmerman [Relationship between the parameters of the Mogi and Coulomb failure criterion. Int J Rock Mech Min Sci 2005;42(3):431–39.] developed the Mogi–Coulomb failure criterion, and showed that it is reasonably accurate in modelling polyaxial failure data from a variety of rocks. We then develop a model for the stability of vertical boreholes, using linear elasticity theory to calculate the stresses, and the fully-polyaxial Mogi–Coulomb criterion to predict failure. Our model leads to easily computed expressions for the critical mud weight required to maintain wellbore stability.