Showing papers in "Journal of Mechanical Strength in 2006"

New continuous fatigue damage model based on whole damage field measurement

Abstract: First of all,the whole damage field curves with toughness that selected as the fatigue damage variable was measured,then on the basis of frame of nonlinear continuum fatigue damage theory,the expressive form of fatigue damage parameter was decided by means of the tested curve data,and a new nonlinear fatigue damage cumulative model was proposed.Comparison of the new nonlinear fatigue damage model with test results showed reasonably good agreement.Based on this comparison,formula of lifetime calculation on complex loading was derived and mean stress was considered by the formula of lifetime calculation.Experiment stated clearly that two loading prediction by means of this calculation model was quite reasonable.

Research on structure static and dynamic design based on fea of machining center columns

Abstract: The design method and it’s process of columns structure of machine center are proposed based on dynamic design principle and variation analysis technology by finite element method (FEM). With ANSYS software, the static analysis and modal analysis to the column of the machining center are done. The influence by the inner frame in column to the static and modal performance is researched. Through three structures calculated, the best frame of column is found out. The method of the paper is an example for the effective design to the big parts of machine tool.

Analysis of the random-fuzzy reliability based on the information entropy theory

Abstract: Based on the principle of the information entropy theory that the information entropy of a variable does not change with its expressed type,the fuzzy variables in a structural analysis were transformed into random ones or the random variables into fuzzy onesThen,the strength reliability degree of a structure was solved out by use of the random reliability method,the random-fuzzy reliability one and the fuzzy reliability one,respectivelyFinally,the strength reliability degree of a pressure vessel was given by the three methods aboveThe comparisons indicate that the results from the three methods are much close to one another and the transformation method is effective

Finite element analysis for the elastic modulus of open-cell foams based on a tetrakaidecahedron model

Abstract: The cellular structure of open-cell foams can be modeled and their elastic modulus can be calculated by the finite element method. In the calculation, all tetrakaidecahedrons with the same size are used and the effects of two different sections shape (circular and Plateau struts) on elastic modulus are considered. In addition, the variation of elastic modulus with model sizes is investigated by numerical method. At the same time, the effect of boundary condition on the calculation for elastic modulus of open-cell foams is also discussed. The results show that the elastic moduli obtained by model with Plateau struts are significantly higher than the ones of model with circular struts. In addition, the elastic modulus of two models all increases with their sizes and approach to a stable value which is agreement with the theoretical prediction of Warren and Kraynik model. Furthermore, the effect of boundary condition on the rigidity of model is decreased gradually with increase of model sizes.

Research for hinge sleeve’s structural optimal design based on fatigue intensity

Abstract: By the means of the structural analysis, the key part of the diamond six-faces presser——the hinge sleeve’s finite element model and the structural optimal design model is set up. Taking into account of the fatigue intensity, the structural optimal design of the hinge sleeve has been finished. A comparatively complete design method and system could be afforded for the key part of the diamond six-face presser. According to the characteristic of the hinge sleeve, the dissertation realizes a data interchange between Pro/E and ANSYS in the IGES standard. The efficient integrated CAD(computer aided design)/CAE(computer aided engineering)system of the hinge sleeve is made out. It is a beneficial trial for the research of CAD(computer aided design)/CAE(computer aided engineering)/CAM(computer aided manufacture) system integration. Using the APDL language of ANSYS, the structural optimal design program-ODPST is programmed. Taking the C0 (0-step) method, the accurate and reliable design parameter can be obtained. This improves the fatigue intensity of the hinge sleeve effectively. In the optimization process, the sensitivity analysis technology is used to improve calculation efficiency.

Review of models in machinery fault prediction

Abstract: An overview and classification of fault prediction techniques in machinery systems is presented. The importance of applied modeling approaches in fault forecast is introduced. Emphasis is focused on the advantages and disadvantages of the conventional forecasting models. The suitable range and applications of these models are also shown. Moreover, the trend of machinery fault prediction is discussed. For precise and reliable machinery fault detection, it is essential to use multivariable forecasting modes to describe the changes in several diagnostic indices. There are various trends in machinery fault development, so the fault quantification could be performed by means of combined forecast models.

Study on dynamics and fault characteristics of two-span rotor-bearing system with pedestal looseness

Abstract: A non-linear dynamic model was established of a two-span elastic rotor-bearing system with pedestal looseness fault supported on three plain journal bearings. The complex motion characteristics of the rotor-bearing system were numerically studied, and the influences of the looseness mass to the nonlinear characteristics were analyzed. The results indicate there are marked influences of the looseness mass to the characteristics of the system in high rotate speed region, especially the chaos and period-3 motions. Peculiar trajectories of loosened journal center slightly shaking pedestal is found. A theoretic reference is provided to diagnose the fault of pedestal looseness in the rotor-bearing system effectively.

Undecimated wavelet transform based on lifting scheme and it’s application in fault diagnosis

Abstract: Because decimation operation is applied in classical discrete wavelet transform when signals decomposed, some temporal signatures of the signals are not nicely preserved in decomposition signals. Moreover, the decomposition signals are translation variant. As motioned above, the decomposition signals can not perfectly characterize fault feature in the time domain. In order to overcome the drawbacks above, a framework of undecimated wavelet transform (UWT) via lifting scheme was proposed on the basis of the principle of UWT. Firstly, removing split step of the lifting wavelet transform by using signal transformation technique, the UWT framework based on lifting scheme was obtained. Then, by virtue of the framework, the transformation relations of predictor and updater between UMT and decimated wavelet transform were found, and an algorithm for UWT decomposition and reconstruction was developed. The proposed UWT effectively extracted the friction fault features of amplitude modulation and transient impact from vibration signal of a gearbox.

Threshold problems on fault diagnosis of the atomic emission spectrometer oil analysis

Abstract: The importance and formulation method of the oil analysis for threshold have been researched.The threshold differentiate two classes, that is concentration and trend,they contain nomorl and margin and abnormal separately.Mainly for to determine the threshold of the atomic emission spectrometer oil analysis,the method is researched and has been used in practice.

Application of recurrence plot and approximate entropy on complexity analysis of machinery fault signal

Abstract: One dimension time series is extended to high dimension phase space by using phase space reconstruction algorithm. By studying the distribution rule and movement characteristic of neighborhood points of time series in high dimension. The method of recurrence plot and approximate entropy used for getting the dynamics behavior of original time series were proposed. The influence of noise on recurrence plot and numerical calculation stability of approximate entropy method are studied. The results show that the two methods can depict the complexity of signal effectively. Approximate entropy and recurrence plot are used for characterizing complexity analysis of machinery fault signal, the approximate entropy and recurrence plot of two different signals are compared. The calculation results are consistent with the fact.

New method for the calculation of the characteristics of aerodynamic bearings

Abstract: The compressible Reynolds equation, which is the basic equation of the mathematical model of aerodynamic bearings, was mathematically transformed into standard elliptic PDE (partial differential equation) form, and as a result, MATLAB’s PDE Toolbox can be utilized as a PDE solver. An iterative calculation program was developed and the high precise calculation of aerodynamic bearings is realized. The calculation results were validated and show good agreements with those already published. This indicates the correctness of the presented method. The idea of the presented method can be applied to other types of bearings and PDE problems.

New reliability analysis method based on artificial neural network

Abstract: For implicit limit state equations in most engineering reliability analysis,a new method is presented on the basis of artificial neural network(ANN),where the training samples are appropriately selected.Due to the powerful tool of function approximation,ANN is employed to obtain the relationship of the input parameters and the output parameters in the implicit limit state equation.The reliability analysis for the implicit limit state is then transformed to that for the explicit limit state,and the computational efforts are greatly decreased.Comparing with available reliability analysis based on ANN, the presented method has a different strategy on selection of the training samples,in which the implicit state equation can be more appropriately approximated.The precision of the presented method is higher than that of the available method,and this advantage is illustrated by examples.

Small sample test method for s—n and p—s—n curves

Abstract: Based on the heteroscedastic regression analysis theory,a small sample test method for S—N and P—S—N curves is established,which can obtain S—N and P—S—N curves of metal materials by scattered test.All the test data of a S—N curve in different stress levels can be analyzed as an integration,so its information quantity is much bigger than traditional group test method.To the group test data,the presented method precision is also higher than the group test method.Therefore,by the presented method,P—S—N curves can be obtained without complementary test through treating the existed test data of S—N curves.Monte Carlo simulations and engineering applications show that comparing with traditional method in the same precision upwards of 60% specimens can be saved by this method.

Frictional contact analysis of packer rubber with large deformation based on adhesive-slip frictional contact method

Abstract: s Frictional contact for rubber in large deformation is a complicated nonlinear problem. About the calculation of contact stress for packer rubber, the model of adhesive-slip frictional contact was took into account. A numerical approach, by combining Penalty method with incremental loads method of large deformation to deal with this problem, is described. The friction contact between casing pipe, oil pipe, supporting loop and packer rubber was analyzed with this numerical approach. The results show that this approach can simulate the deformation and contact stress of the packer rubber in its service, and more accurate as compared with other classical analytical formulas. Friction coefficient has the obvious affects on contact stress of packer rubber.

Low cycle fatigue life prediction method based on power-exponent function model

Abstract: The analysis took two points into account,namely quadratic characters of plastic strain amplitude vs.reversals to failure in log-log scale coordinates and the residual stabilization.Based on power transformation methods,it advanced a power-exponent function model for LCF(low cycle fatigue) life prediction.The investigation gave some power transformation exponents (p) and model performances contrast results of some materials.The contrast results show that power-exponent function model has better performances and precisions for LCF life prediction.In fact,Manson-Coffin equation is the first order Taylor expansion approximation of power-exponent function model in log-log scale coordinates and is the equivalence form when p is equal to 1.The enhancement of nonlinearity makes the power-exponent function model present better precision.The new life prediction model remains the simpleness for engineering application that the model parameter estimation still use linear regression method.

Research on a micro-accelerometer’s systemic modeling based on equivalent circuit method

Abstract: An approach to establish the system-level dynamic model for a type of closed-loop capacitive micro-accelerometer is discussed The work focuses on the macromodeling of a variable capacitor as an elementary electromechanical transducer at first To get an equivalent circuit representation of the model, the device is linearized for incremental variables around its equilibrium point, using Taylor series expansion Based on it, the macromodels of the two differential capacitors, which respectively serve as sense and force element in the sensor, are presented and coupled with outside components Then, an example is illustrated and the validity of the proposed methodology is proved The constructed system-level equivalent circuit, which can be analyzed by commercial circuit simulators, OrCAD etc, provides reliable foundation for further system simulation and global optimization for the prototype product

Discriminant approach to the machinery or sensor fault based on the k-l divergence

Abstract: It is usually the case for a mechanical fault diagnosis system to configure two sensors in the same monitoring positionThe two sensors' output signals are used to estimate their respective probability density using kernel density estimation method,and then the K-L(Kullback-Leiber) divergence between two output signals is calculatedA discriminating approach of machinery or sensor faults is proposed based on the K-L divergenceThrough evaluating real vibration signals measured on a gearbox and some simulated sensor fault signals,it is shown that contrasted to the K-L divergence between two sensors' output signals with fault-free condition,the K-L divergence decreases significantly when a progressed pitting in gears occurs;while it increases significantly when one of two sensors shows some faultsTherefore,the K-L divergence could be an index to distinguish between machinery and sensor faults

Research on calculating the reliability of mechanical component with correlaed failure modes

Abstract: The reliability of mechanical component is of great value in engineering design,but the correlation of the failure modes of mechanical component brings the difficulty on calculating the reliability.The simplification way to calculate the reliability of component with correlated failure modes is presented,and it is proved by the narrow reliability bounds theory that was presented by O.Detlevsen.At last,the simplification method is compared with the Monte Carlo simulation by the example calculating the reliability for axis.The result shows that the simplification method considering the correlation is simple,efficiency and accurate,and is of great value for calculating the reliability of correlated failure modes in engineering design.

THERMO-FATIGUE LIFE PREDICTION METHODOLOGIES FOR SnAgCu SOLDER JOINTS IN FLIP-CHIP ASSEMBLIES

Abstract: Thermal fatigue failure, due to the fracture of solder joints which was caused by the mismatch deformation, is frequently encountered in flip chip (FC) assemblies Unfortunately, there is no widely accepted method to evaluate the reliability of solder joints, especially for lead-free solder joints, in such assemblies up to now The constitutive models of double power law and the hyperbolic sine law were implemented to simulate the deformation of SnAgCu solder joints in flip chip assemblies The accumulated creep strain and accumulated creep strain energy density of the solder joints were calculated, via finite element method, and were use to predict the thermal fatigue life of flip chip assemblies The applicability of the above life prediction methods was evaluated through cross check of the present results with that of the literatures It was found that the life of the FC assemblies could be estimated by the prediction of the life of the corner solder joints The thermal fatigue life, estimated according to accumulated creep strain energy density is closer to the test data than that of the life estimated according to accumulated creep strain The life predicated according to accumulated creep strain shown a slightly high value than that predicated according to accumulated creep strain energy density The double power law constitutive equation results in a higher predicted life

Analysis vibration characteristic of electromechanical coupling system of rolling mill based on ac drive

Abstract: Establishing a suitable model of rolling mill systems which displays dynamic processes correctly and effectively is a key for system design,control,condition monitoring and fault diagnosis of rolling mill systems. With the rapid development of the AC(alternating current) technique,AC motor has be applied in drive system of the rolling mill. The effects of motor on rolling mill systems are considered and an electromechanical model is established. By simulating electromechanical coupling dynamic processes of rolling mill systems caused by serious capacitors in power network,friction,clearance and load changing,a conclusion was proved that the electromechanical coupling model is very useful in analyzing dynamic principles of rolling mill systems,and it can provided information for vibration control of rolling mill.

Response surface method for reliability analysis of implicit limit state equation based on weighted regression

Abstract: A response surface method on the basis of weighted regression is proposed for reliability analysis of implicit limit state equation,in which a linear response surface function(RSF) is used to fit the actual implicit limit state.The strategy of the method can be summed up as three.(1)The sampling points are selected at those experimental points with smaller absolute value of actual limit state(AVALS).(2) In regression analysis,the weight factor for each point is calculated based on its AVALS.By the weighted regression,the effect of those sampling points with smaller AVALS on determination of RSF is augmented,and the effect of those sampling points with bigger AVALS is weakened.(3) Analogous as the traditional response surface method,the iteration strategy converging at design point is employed in the method.The above three strategies ensure the linear RSF can fit the actual implicit limit state equation better in the vicinity of the design point.Therefore highly precise evaluation of reliability index can be obtained.The examples are illustrated the advantage of this method.Further more,through the combination of the multiple linear response surfaces,the present method can be developed as a precise reliability evaluation method for the implicit limit state equation with high non-linearity in limit state and high coefficients of variability in basic variables.

Six sigma robust design methodology based on dual response surface model

Abstract: Dual response surface methodology has been proposed for engineering robust design by constructing the response surface models of mean value as well as variance,through experimental design.While the quality of product or process in engineering is usually assessed by statistical item-σ level.To link the quality control requirement with the engineering design optimization,the paper proposed a 6σ robust design methodology based on dual response surface model.The establishment of dual response surface model as well as optimization efficiency was investigated.The application of this method to structural design and sheet metal stamping process design were performed.Compared with traditional optimization method,this new method can improve not only the design efficiency,but also the design reliability and robustness.

Research on the vertical stiffness and damping of the air spring with auxiliary chamber by test

Abstract: Based on the 1T15M-2 reversible sleeve air spring made by Firestone Corp., an air spring with auxiliary chamber was built. The character of the air spring in vertical direction was described as a linear spring damper element. Using the method of free vibration with damping, the changing rules of the stiffness and damping under different pressure in the air spring with the change of throttle orifice diameter have been studied experimentally. The researches found out that, under individual pressure, the diameter of throttle orifice had the influence on both the vertical stiffness and damping. When the diameter of the throttle orifice changed from 3 mm to 10 mm, the stiffness of the air spring with auxiliary chamber changed greatly, and the larger the throttle orifice was, the smaller the stiffness became, the sensitive changing range of the damping was 0 to 20 mm. The damping reached the maximal value at about 5mm. The research results provided a basis for developing the air suspension system with continuously adjustable stiffness and damping.

Finite element analysis of shrink fit in disc with shaft

Abstract: Based on the contact simulation,discuss the applications of the general contact elements in the shrink fit in disc and shaft.The model of impeller with shaft of steam turbines is set up and the contact stress of shrink on disc has been investigated by using ANSYS.Comparison with traditional method is also given.Illustrates the accuracy,effectiveness and reliability for calculating the contact stress of shrink-on disc by using this new finite element method.And it also shows the limitation of the traditional method.

Method for time-varying series analysis

Abstract: The time-varying series model whose white-noise standard deviation varies with time is researched. A method for determining the function forms of white-noise standard deviation, autoregressive and moving average coefficients is established. The least square method and the maximum likelihood method are used respectively to determine the parameters. The prediction formula and its error estimation are also established. Its regression and time-varying autoregression model is presented.

Research on hole-edge stress distribution of composite materials plate with complex holes by integral equations method

Abstract: Hole-edge stress analysis of composite materials plate with complex holes was presented base on the nonhomogeneous anisotropic elastic theory, which resolves boundary conditions problem of complex holes, gets stress distributing of opening structure and gives accurate analytical solutions on composite materials plate with hexagon, rectangular and aerofoil manhole at last, moreover, constrast calculates were carried through FEM(finite element method). The plane stress field is obtained by complex stress function with conformal mapping method, and then the influences on hole-edge stress concentration factors are discussed under different loads and machine direction cases.

Strength analysis of engine suspending bearings

Abstract: The finite element model for engine suspending bearings was established,considering the contact condition between the rubber and steel,contact pairs that satisfy manufacture requirements(there must be rubber adheres to the steel) were established.The loads that the bearings endured during operation were analyzed.Since the deformation of rubber material is incompressible and nonuniform,the material property of rubber was assumed to be hyperelastic,isotropic and isothermal.The original fatigue position of the structure was determined from the contours of stress intensity calculated by finite element program,which accords with the actual initial fatigue crack position.The ultimate fracture surface was also proposed.The calculated alternating stress intensity of the structure confirmed the fatigue failure position ulteriorly.The regular distribution of stress intensity provides a basis for simplifying this three dimensional structure into two dimensional structure to perform fracture calculation, so that the calculation scale can be reduced significantly.

Research of fault diagnosis of rolling bearings based on emd and power spectrum analysis method

Abstract: According to the non-stationary and non-linear characteristic of rolling bearing vibration signal,an analysis method based on empirical mode decomposition and power spectrum is put forwardFirstly,the original vibration signals are decomposed into a finite number of stationary intrinsic mode functions(IMFs) by EMD(empirical mode decomposition)Then the IMFs relating to fault information are applied to power spectrum analysisThe result of the method is the power spectrum of relating IMFs,which can illustrate the characteristic of the signal clearly and extract the fault characteristic information easilySince the EMD method is self-adaptive,it is applicable to non-linear and non-stationary signalsApplied example proves the effectiveness of the method

Study on the preliminary deformation force of the flexspline in harmonic gear driving

Abstract: Based on the principle and characteristic of harmonic gear driving, researched the problem about the sharp increase of stress in short flexspline deformation. Applying the finite element method, studied the preliminary deforming status of the flexspline in HGD(harmonic gear driving). Discussed what influence that the geometry factors of flexspline bring to the pre-deforming force of flexspline. Get the conclusion that the length of flexspline cup body and the thickness of flexspline cup wall are the foremost geometry factors to influence the pre-deforming force. At last, made many regression analysis for the rule of the flexspline wall thickness influence the pre-deforming force and the rule of the flexspline length-diameter ratio influence the pre-forming force.

Study of stability of moderately thick composite laminates under axial compression loading and shear loading

Abstract: The stability of moderately thick composite laminates under axial compression loading and shear loading is analyzed by means of linear buckling analytical method and arc-length methodThe first order buckling mode and buckling equilibrium path are presentedUnder axial compression loading,the laminates can not take on any increasing load after they lost stability,but Laminates are impossible lost stability under shear loading