Papers by Keyword: Reliability Estimation

Abstract: The paper describes the basic principles and some results of obtaining data by means of integral strain gauges about load-carrying capacity and durability of gear transmissions for new specimens of machines when running in the transmissions in structure of gear box on the stand, or in short-term trials of machines in field conditions.

Abstract: The article describes an approach dedicated to a hybrid representation of mechatronic systems combining matrix and block notations. The main attention is focused on the identification of relationships between mechatronic machines in respect of functional reliability (analysed in the form of block and digraph notations) and rules that allow for the simplification of the reliability function in the systems of machines connected in parallel, series and complex arrangement. The author has adopted a functional representation based on system demonstration employing a binary function of reliability in which the equation is determined based on the method for setting minimum paths in the graph (structural representation of each subsystem). The introduced assumption allows reducing any structure to a serial connection of functional blocks. The author of the paper has also described a manner of implementation in real systems. This article does not include the description of the method used for determining the reliability function, but only theoretical assumptions used in case of identifying functional dependencies.

Abstract: Aimed at the problem that because common proportional hazards model (PHM) cannot fuse new failure data of long-life complex equipment, which features a small-sample, the reliability estimation accuracy will decline, a new condition-based maintenance strategy based on dynamic PHM was proposed. Kalman filtering theory was adopted to fuse in-time new failure data and expand sample size. Extended Kalman filtering method was used to solve the nonlinearity of the observation equation of PHM and then its regression coefficient was online updated, according to which the residual life was estimated and the optimal maintenance decision was made. Finally, the condition monitoring data and historic operation data of a certain kind of wind power gearbox were used to validate this method. The result indicates that this method has good dynamic estimation ability under the condition of small sample with a 20.6% increase in the accuracy of regression coefficient estimation and a 8.7% decrease in optimal preventive maintenance interval estimation error.

Abstract: Suppose that the life of unit is distributed as two-parameter exponential distribution. The Bayesian estimation for cold standby series system is studied based on general Progressive type II censored samples. Under the different error loss, the Bayesian estimation of the unknown parameter and reliability function are derived where hyper-parameters are estimated by using Maximum likelihood method. At last, a numerical example is given by means of the Monte-Carlo simulation to illustrate the correctness and feasibility for the method proposed in this paper.

Abstract: Two methods acquiring p-S-N curve for machine parts are given, namely directly searching out the p-S-N curve of the material from material database and using the idealized p-S-N curve. Reliability estimation methods of fatigue life of machine parts are derived under uniaxial constant amplitude load. Two kinds of circumstances (fixed stress and probabilistic stress) and two kinds of stress cycles (reversed cycle and unsymmetric reversed cycle) are considered. An iteration method is presented and the corresponding computer program is developed for estimating reliable life of machine parts. The engineering application results show that the calculated results are closer to experimental results. The suggested method can be convenient to fatigue reliability design of machine parts. It has good stimulative effect on popularization and application of existing anti-fatigue design method for machine parts, and high value of engineering application.

Abstract: The expression of reliability estimation method for fatigue life of machine parts was derived, and two kinds of stress cycles (reversed cycle and un-symmetric reversed cycle) were considered. An iteration method is presented and the corresponding computer program named STRENGTH-2 is developed for estimating reliable life of machine parts. The engineering application results show that the calculated results are close to experimental results. The proposed method can be convenient to carry out the fatigue reliability design for machine parts under the action of uni-axial and multi-axial loadings, and promote the popularization and application of existing anti-fatigue design method. It has the high value of engineering application.

Abstract: Complex mechatronic systems sometimes do work in difficult and adverse environment. Such environment may affect the system’s performance and also dependability characteristics. Since we use complex systems with one shot items we need to know basic characteristics of such a system. The paper deals with advanced mathematical methods used for field data assessment in order to prove presumed impact of mission profile and system real operation profile onto system reliability. Thank to the collected data set it is assumed that operation of the system is actually a kind of time series. The paper presents identification of the time series model, its parameters´ estimation and prediction of system characteristics – like reliability/survivability function of the system for instance. Since the model of the time series has not been known, correlations with other system can be further determined and mission duration estimated. This estimation helps to organize support and operation of the system.

Abstract: The reliability estimation of pipeline is performed in accordance with the probabilistic methods such as the FORM (first order reliability method) and the SORM (second order reliability method). A limit state function has been formulated with help of the FAD (failure assessment diagram). Various types of distribution of random variables are assumed to investigate its effect on the failure probability. It is noted that the failure probability increases with the increase of the dent depth, the operating pressure and the outside radius, and the decrease of the wall thickness. Furthermore it is found that the failure probability for the random variables having the Weibull distribution is larger than those of the normal and the lognormal distributions.

Abstract: The reliability estimation of pipelines is performed with help of the probabilistic method which considers the uncertainties included in the load and resistance parameters. The FORM (first order reliability method) is carried out to calculate the failure probability of corroded pipeline for the classified six distribution types of random variables. And the reliability of pipelines is assessed by using the failure probability. Furthermore, the MCS (Monte Carlo Simulation) is used to verify the results of the FORM. It is noted that the failure probabilities of the linear and the power models for surface corrosion are similar and those of the two-phase model for surface corrosion are somewhat different for six cases of two failure pressure models such as ASME B31G and MB31G models. And it is also found that the FORM and the MCS give similar results for varying exposure time.

Abstract: In this paper, the FORM (first order reliability method) has been employed to estimate the probability of failure for the buried pipeline degraded by corrosion defects. The estimated results are used to assess the reliability of buried pipeline exposed to varying external and internal boundary conditions corresponding to a required target safety level. Furthermore, the effects of distribution types of random variables affecting the strength of buried pipelines on the probability of failure and the reliability of the buried pipeline are systematically investigated. The plant-engineers should be informed about the margin of safety level of existing pipelines corresponding to the target safety level to assess the integrity of the corroded pipeline under operation.