Reliability Engineering最新文献

TQC (Total Quality Control) and elimination of the early failure can make the average lifetime of PARS (Piezoelectric Angular Rate Sensors) increase by 8·95 and 9·20 times, respectively. With the two methods, the lived distributions of uniaxial and triaxial PARS are also Weibull distributions. The MTBF are 20 250 and 6750 hours, respectively, i.e. increase by 20·92 and 20·96 times.

The concept of pseudo-switching (PS) functions has definite advantages in representing nonbinary discrete random functions, usually encountered in the study of flow networks. That concept is utilized in the development of star-delta and delta-star transformations that preserve the source-to-terminal (s−t) capacity function in a flow network. The usefulness of these transformations in reducing complex networks to equivalent series-parallel ones is illustrated by examples. The resulting series-parallel networks are easily solvable for the networks s−t capacity function, which is a compact expression of the probability mass function (p.m.f.) of the maximum s−t flow.

Markov models are frequently used in connection with system reliability evaluations. In this paper we study Markov models both for single components and for systems of possibly dependent, components. The purpose of the paper is to indicate how certain monotonicity properties of the model can be utilized in order to derive inequalities for interesting reliability parameters. As another application it will be indicated how monotonicity properties can be used to simplify problems concerning optimal replacement of components or systems. The paper is based on results published in probability and operations research journals during the past few years.

The need arose in a large team of safety assessors for a standard method of treating common cause failures to be defined so that a consistent approach could be followed across a range of projects. The requirements of the model were: acceptability, applicability, flexibility and consistency. It was found by combining the ß-factor model with limiting values and allowing the value of β to reduce as the protection against CCF increases, it was possible to meet the objectives of the model. An example of the use of the model is included.

Limit state models based on multi-dimensional rotational paraboloids and hyperboloids are described, and approximate closed form solutions obtained for the associated failure probability and corresponding reliability index. The solutions presented depend only on the number of variables, minimum distance of the limit state surface from the origin and mean curvature at the design point, in a standard normal space. These results extend the range of analytic solutions for reliability indices, from linear and spherical surfaces, to include these rotational quadrics, and so permit a wider choice of limit state models.

Event trees are an essential tool in reliability studies of systems. Their main goal is to define the significant accident sequences. This paper presents the general aspects of the event tree technique and the AREV software package for automatic treatment of event trees, which comprises four main modules: data introduction module, reduction module, probabilistic evaluation module and plotting module. Finally an example is given for illustration. This package is implemented on the PC computer.

With the continued improvement in electronic product reliability the requirement to test larger and larger samples is becoming more and more difficult to manage. As a result methods by which these sample sizes might be reduced are extremely attractive. This paper investigates an approach in which the one-parameter Weibull distribution is assumed to explain the failure mode, and looks at the consequences if this assumption turns out not to be valid. Specifically, the effect on calculated MTTF is examined from the point of view of variation in the shape parameter, and it is shown that massive errors can result for only slight variations in this parameter.