Reliability Of Mechanical Components Research Articles

Surrogate model building and error analysis for the damage tolerance life of penetration type fatigue crack

The penetration type cracks are often found in the components of mechanical systems and are a major threat to the operational reliability of mechanical components. There are many factors affecting the fatigue crack damage tolerance life, so the numerical calculation of 3D fatigue crack propagation is a complex process. Therefore, it is significant to improve the calculation efficiency of fatigue crack life with guaranteeing the calculation accuracy. The crack life is the result of the integration of crack propagation length and stress intensity factor(SIF). In this paper, a surrogate model for calculating the damage tolerance life of penetrating fatigue cracks is constructed using Kriging method based on the results of experimental tests and finite element analysis(FEA). The surrogate model is a four-dimensional response-value solution model, which can solve the fatigue crack life under random parameters. Finally, an error analysis is performed on the results of the surrogate model calculation. The results indicate that the error of the surrogate model calculation is relatively low, and the overall error is within 2%. Therefore, the surrogate model is characterized by high efficiency and accuracy.

Effect of magnetic field intensity on friction and wear of TiN- and TiCN-coated neodymium magnets

Numerous machinery components are constantly influenced by magnetic fields, mainly because of the environments in which they operate. In addition, these components show different friction and wear characteristics throughout their lifetime because of their operating conditions. Here, the tribological characteristics of magnetized materials were investigated. The magnet specimens consisted of a neodymium magnet, which is one of the strongest magnets, coated with TiN or TiCN. Sliding tests were conducted with a ball-on-disk-type tester. The tribological properties of magnetized samples were compared considering their different coating conditions. The wear amount was measured under constant load and cycle conditions. The measured wear amount was used to evaluate the specimens’ tribological characteristics. One of the important factors affecting the wear and friction properties is the magnetic flux density and the formation of an oxidative transfer layer under a magnetic field. Samples subjected to a magnetic field showed better wear resistance as a result of a magnetic effect that resulted in debris being oxidized at the rubbing interface, which reduced debris production. These results can be used to evaluate the reliability of mechanical components exposed to a magnetic field.

Study on the Reliability of Mechanical Components of Squib Valve in Passive Nuclear Power Plant

The action principle of squib valve employed in passive nuclear power plant was introduced and the main factors affecting the reliability of the mechanical components of the squib valve were analyzed, and the shear cover material of the squib valve was subjected to different strain rates at normal temperature, 155 °C and 350 °C, The parameter distribution of Johnson-Cook constitutive model was obtained by fitting the test data, and the impact velocity, material properties and failure strain of the squib valve piston were selected as random variables, and the reliability of the mechanical components of the squib valve was calculated by the joint simulation of ABAQUS+NESSUS. The results show that the reliability of the squib valve is high, and the mechanical performance of the shear cap material is the biggest impact on the mechanical reliability of the squib valve. The mechanical reliability of the squib valve is positively related to the impact speed of the piston. This study provides a reliable basis and reference for quantitative assessment of the overall reliability of the squib valve and the application in passive nuclear power plant.

Modern Diagnostic Techniques and Mathematical Models of Reaching High Reliability and Safety in Engineering Systems during Design and Tests of Developmental Prototypes

This article is about reaching and securing high reliability and safety in engineering systems during the design and testing of developmental prototypes. A new approach to and technique of calculation of the design reliability is proposed, taking into account both kinds of failure rates, those that are constant and those that change over time. The function for calculation of design reliability is represented by the product of three constituents of failsafe operation probabilities throughout the whole period of operation, considering the calculation of the reliability of mechanical components and metalwork. The calculation model proposed for reaching and securing the required reliability and safety levels takes into account controlling actions. A new approach and technique, as well as mathematical models, for planning the scope of testing for various laws of run-to-failure distribution are proposed on the basis of nondiscardability of expensive objects. The study results are recommended for use in creating complex engineering systems.

Time-dependent reliability analysis of the motor hanger for EMU based on stochastic process

Purpose Most of the previous work on reliability analysis was based on the traditional reliability theory. The calculated results can only reflect the reliability of components at a specific time, which neglects the uncertainty of load and resistance over time. The purpose of this paper is to develop a time-dependent reliability analysis approach based on stochastic process to deal with the problem and apply it to the structural design of railway vehicle components. Design/methodology/approach First, the parametric model of motor hanger for electric multiple unit (EMU) is established by ANSYS parametric design language, and its structural stress is analyzed according to relevant standards. The Latin hypercube method is used to analyze the sensitivity of the structure, and the uncertainty parameters (sizes and loads) which have great influence on the structural strength are determined. The D-optimal experimental design is carried out to establish the polynomial response surface function, which characterizes the relationship between uncertainty parameters and structural stress. Second, the Poisson stochastic process is adopted to describe the number of loads acting, and the Monte Carlo method is used to obtain the load acting history according to its probability distribution characteristics. The load history is introduced into the response surface function and the uncertainty of other parameters is considered at the same time, and the stress history of the motor hanger is obtained. Finally, the degradation process of structural resistance is described by a Gamma stochastic process, and the time-dependent reliability of the motor hanger is calculated based on the reliability theory. Findings Time and the uncertainties of parameters have great impact on reliability. The results of reliability decrease with time fluctuation are more reasonable, stable and credible than traditional methods. Practical implications In this paper, the proposed method is applied to the structural design of the motor hanger for EMU, which has a good guiding significance for accurately evaluating whether if the design meets the reliability requirements. Originality/value The value of this paper is that the method takes both the randomness of load over time and the uncertainty of structural parameters in the design and manufactures process into consideration, and describes the monotonous degradation characteristics of structural resistance. At the same time, the time-dependent reliability of mechanical components is calculated by a response surface method. It not only improves the accuracy of reliability analysis, but also improves the analysis efficiency and solves the problem that the traditional reliability analysis method can only reflect the static reliability of components.

Reliability calculation method based on the Copula function for mechanical systems with dependent failure

In order to accurately calculate the reliability of mechanical components and systems with multiple correlated failure modes and to reduce the computational complexity of these calculations, the Copula function is used to represent related structures among failure modes. Based on a correlation analysis of the failure modes of parts of a system, a life distribution model of components is constructed using the Copula function. The type of Copula model was initially selected using a binary frequency histogram of the life empirical distribution between the two components. The unknown parameters in the Copula model were estimated using the maximum likelihood estimation method and the most suitable Copula model was determined by calculating the square Euclidean distance. The reliability of series, parallel, and series–parallel systems was analyzed based on the Copula function, where life was used as a variable to measure the correlation between components. Thus, a reliability model of a system with life correlations was established. Reliability calculation of a particular diesel crank and connecting rod mechanism was taken as a practical example to illustrate the feasibility of the proposed method.

Improving the Reliability of Mechanical Components That Have Failed in the Field Due to Repetitive Stress

To improve the reliability of mechanical parts that have failed in the field, a reliability methodology for parametric accelerated life testing (ALT) is proposed. It consists of: (1) a parametric ALT plan, (2) a load analysis, (3) a tailored series of parametric ALTs with action plans, and (4) an evaluation of the final designs to ensure the design requirements are satisfied. This parametric ALT should help an engineer reproduce the fractured or failed parts in a product subjectedto repetitive loading and correct the faulty designs. As a test case, the helix upper dispenser of a refrigerator ice-maker fractured in field was studied. Using a load analysis, we discerned that the helix upper dispenser fracture was due to repetitive loads and a faulty design with a 2 mm gap between the blade dispenser and the helix upper dispenser. During the first and second ALTs, the fracture in the helix upper dispenser was reproduced. The failure modes and mechanisms found were similar to those of the failed sample in field. As an action plan, the design of the helix upper dispenser was modified by eliminating the 2 mm gap and adding enforced ribs. In the third ALT there were no problems. After three rounds of parametric ALTs, the reliability of the helix upper dispenser was guaranteed as a 10-year life with an accumulated failure rate of 1%.

Reliability evaluation and improvement of manufacturing helicopter in an aircraft manufacturing company - case study: skid types helicopter landing gear

Due to its sensitivity to time and accuracy, aerospace equipment requires a highly accurate manufacturing process to achieve higher reliability compared to other equipment. Focusing the studied helicopter, this study examines reliability of components of a landing gear manufactured by an aircraft company to improve total reliability of the product. Developing a model for risk-based design of a landing gear, this study proposes an inclusive approach for evaluating and promoting total reliability of the landing gear. Obviously, the reliability of components leads to the total reliability of product. This study identifies different components of a product to examine reliability of a component of that product. Then, the components are prioritised by FMEA for promotion to increase total reliability of the product. In conclusion, the objective of this study is to develop an inclusive model for improving reliability of mechanical components of landing gear manufactured by an aircraft company.

Reliability evaluation and improvement of manufacturing helicopter in an aircraft manufacturing company - case study: skid types helicopter landing gear

Due to its sensitivity to time and accuracy, aerospace equipment requires a highly accurate manufacturing process to achieve higher reliability compared to other equipment. Focusing the studied helicopter, this study examines reliability of components of a landing gear manufactured by an aircraft company to improve total reliability of the product. Developing a model for risk-based design of a landing gear, this study proposes an inclusive approach for evaluating and promoting total reliability of the landing gear. Obviously, the reliability of components leads to the total reliability of product. This study identifies different components of a product to examine reliability of a component of that product. Then, the components are prioritised by FMEA for promotion to increase total reliability of the product. In conclusion, the objective of this study is to develop an inclusive model for improving reliability of mechanical components of landing gear manufactured by an aircraft company.

Principle of maximum entropy for reliability analysis in the design of machine components

We studied the reliability of machine components with parameters that follow an arbitrary statistical distribution using the principle of maximum entropy (PME). We used PME to select the statistical distribution that best fits the available information. We also established a probability density function (PDF) and a failure probability model for the parameters of mechanical components using the concept of entropy and the PME. We obtained the first four moments of the state function for reliability analysis and design. Furthermore, we attained an estimate of the PDF with the fewest human bias factors using the PME. This function was used to calculate the reliability of the machine components, including a connecting rod, a vehicle half-shaft, a front axle, a rear axle housing, and a leaf spring, which have parameters that typically follow a non-normal distribution. Simulations were conducted for comparison. This study provides a design methodology for the reliability of mechanical components for practical engineering projects.

Research on the Variety Law of Time-Dependent Reliability Model of Picking Link Rod in Sewing Machine

The reliability of mechanical component is a time-varied process because the parameters such as operation condition, load, strength, are varied with time or the loading numbers. This paper builds the time-dependent reliability model when life is measured by the loading numbers. The variety-law of component’s reliability with the lifetime is derived from the built model and simulation of picking link rod used in sewing machine. It is shown that the time-dependent reliability model is effective and the reliability of component decreases obviously with the time and the increasing load standard deviation.

Reliability-Based Robust Design of Mechanical Components with Correlated Failure Modes Based on Moment Method

There are usually several potential failure modes in mechanical components. The conventional model for the system analysis is built under the condition that all failure modes are independent of each other. However, in engineering practice, failure modes are mostly dependent due to the fact that the elements involved in each failure mode are closely interrelated. System reliability analysis and evaluation simply conducted under independent assumption often result in excessive errors or even wrong conclusion. A novel method to evaluate system reliability of mechanical components with multiple failure modes based on moment method are proposed here. Firstly, the moment-based reliability and reliability sensitivity analysis method is proposed with independent assumption. Secondly, the proposed method is deduced by taking the correlation between failure modes into account and the correlation model is established with the copula function, which is proved to be a useful tool to model nonlinear correlation with marginal distributions. The robust design is performed as a biobjection optimization process based on the reliability sensitivity. The numerical examples show that the applied procedure is able to efficiently consider various failure modes of mechanical components in probabilistic assessment and reliability-based optimization.

Mechanical Component Reliability Calculation through Multi-Plane Combination Method

For the performance function with high nonlinearity around the most probable failure region, stress-strength interference model and advanced first-order second-moment method (AFOSM) can cause huge errors in the computation results. The multi-plane combination method is presented to calculate reliability of the mechanical component, in which the component reliability calculation is first transformed into a relatively simple system reliability problem, and then the equivalent calculation method is applied to estimate system reliability. The example application shows the accuracy and efficiency of the multi-plane combination method.

Reliability Model for Complex Mechanical Component Design

Taking into account the uncertainty in material property and component quality, a complex mechanical component such as a gear should be treated as a series system instead of a component when evaluating its reliability, since there exist many sites of equal likelihood to fail. Besides, conventional system reliability model is not applicable to such a system because of the statistical dependence among the failures of the every element (damage site). The present paper presents a model to estimate complex mechanical component reliability by incorporating order statistic of element strength into load-strength interference analysis, which can deal with multiple failure mechanisms, reflect statistical dependence among element failure events and that among different failure modes.

Reliability Calculation Method for Mechanical Components with Dependent Failure Modes

A mechanical component may fail in many modes that are usually not independent. There is generally not a joint probability density function to describe these correlated failure modes. Thus, it is difficult to compute the reliability with considering the correlations between the failure modes. It is supposed that three or more failure modes arise synchronously to be a very small probability event. The relationship between ultimate state functions in different failure modes is established by utilizing linear regression method. A double integration modal for reliability of mechanical components with dependent failure modes is built according to stress-strength interference model. In case of square, cube or exponential relationship between two ultimate state functions, a linear transformation is made. An example of pin is discussed. Its reliability is compared with that obtained using Monte Carlo method, which represent that the reliability model with multi-failure modes proposed is correct.

Reliability Model of Mechanical Components with Dependent Failure Modes

A mechanical component may fail in many modes that are usually not independent. There is generally not a joint probability density function to describe these correlated failure modes. Thus, it is difficult to compute the reliability when considering the correlations between the failure modes. It is supposed that three or more failure modes arise synchronously to be a very small probability event. The relationship between ultimate state functions in different failure modes is established by utilizing linear regression method. A double integration model for reliability of mechanical components with dependent failure modes is built according to stress-strength interference model. In case of square, cube, or exponential relationship between two ultimate state functions, a linear transformation is made. An example of pin that may fail in shear fracture, bruise, or both is discussed. The reliability is compared with that obtained by using Monte Carlo method, which represents that the reliability model with dependent failure modes proposed is correct.

PROcedures for TESTing and measuring wind turbine components; results for yaw and pitch system and drive train

ABSTRACTPROcedures for TESTing (PROTEST) and measuring wind energy systems) was a pre‐normative project that ran from 2008 to 2010 in order to improve the reliability of mechanical components of wind turbines. Initiating the project, it was concluded that the procedures concerning these components should be further improved. Within the PROTEST project, complementary procedures have been developed to improve the specification of the design loads at the interfaces where the mechanical components (pitch and yaw system, as well as the drive train) are attached to the wind turbine. This is required, since in optimizing wind turbine operation and improving reliability, focus should be given to the design, not only to safety related components but also to the rest of the components affecting the overall behaviour of the wind turbine as a system. The project has resulted in a proposal for new design load cases, specifically for the drive train, a description of the loads to be defined at the interfaces of each mechanical system, as well as a method to set up and use the prototype measurements to validate or improve the load calculations concerning the mechanical components. Following this method would improve the reliability of wind turbines, although more experience is needed to efficiently use the method. Examples are given for the analysis of the drive train, pitch system and yaw system. Copyright © 2012 John Wiley & Sons, Ltd.

Optimization Design on Dynamic Reliability of a Tension Bar

This template explains and demonstrates how to prepare your camera-ready paper for Trans Tech Publications. The best is to read these instructions and follow the outline of this text. The variation rules of strength, load, and reliability of mechanical components are studied with a change in time, and a model is established for dynamic reliability of mechanical components under the random load acting. By combining the theory of reliability design with the method of sensitivity analysis, the computational method of dynamic reliability sensitivity design with arbitrary distribution parameter is proposed based on the methods Edgeworth and perturbation, and the problem of dynamic reliability sensitivity design of mechanical components distributed arbitrary distribution is solved as well as the variation rules of dynamic reliability sensitivity are given. The variation of reliability is studied as design parameters change a little, which provides theoretical data for dynamic reliability design of mechanical components.

A Six Steps Approach to Set up a Measurement Campaign to Validate or Improve the Wind Turbine Component Model

The reliability of mechanical components of wind turbines needs to be improved. In the PROTEST project, a pre-normative project, complementary procedures are developed to improve the specification of the design loads at the interfaces where the mechanical components (pitch and yaw system as well as the drive train) are attached to the wind turbine. This has resulted in a new approach of how to set up and use the prototype measurement campaign. This new approach contains six steps: 1. identify failure modes, 2. design a model, 3. run the load cases, 4. identify input and output certainty, 5. set-up a measurement campaign and 6. process the results to check or improve the models. The main focus of this approach is to enable validation and improvements of the model and its input parameters using a prototype measurement campaign. A flexible approach seems to be essential, as it is unlikely that a strict standard can be created for these components that show several different build-ups and for which very different models are often used. The suggested approach is illustrated using the friction of the pitch bearing as an example.

Dynamic Reliability Sensitivity Design of Mechanical Components with Arbitrary Distribution Parameters

The variation rules of strength, load, and reliability of mechanical components are studied with a change in time, and a model is established for dynamic reliability of mechanical components under the random load acting. By combining the theory of reliability design with the method of sensitivity analysis, the computational method of dynamic reliability sensitivity design with arbitrary distribution parameter is proposed based on the methods Edgeworth and perturbation, and the problem of dynamic reliability sensitivity design of mechanical components distributed arbitrary distribution is solved as well as the variation rules of dynamic reliability sensitivity are given. The variation of reliability is studied as design parameters change a little, which provides theoretical data for dynamic reliability design of mechanical components.