Predictive reliabilities for electronic components

A reliability model to study the behavior of an electronic component subject to several failure mechanisms ls developed. The mechanisms considered for the analysis are of degradation type where the number of defects for a mechanism increases with time, eventually causing the failure of the component. The failure pattern of the component subject to a single mechanism · with given initial and final number of defects is modelled as a pure birth process. Failure time for this mechanism is expressed as the first passage time of the birth process to state k from initial state l. First passage time distribution is derived for different forms of transition rates. When the initial and final states of the process are considered as random, the failure time is expressed as the mixture distribution obtained from the conditional first passage time distributions. The mixture distributions are well represented by a Weibull distribution. A computer program is developed to compute the parameters of the Weibull distribution iteratively by the method of matching moments. The approximation results are statistically validated. The results for a single mechanism are extended to the case of multiple mechanisms. Extreme·value theory and competing risk theory are applied to analyze the simultaneous effects of multiple mechanisms. lt is shown that the aggregate failure time distribution has a Weibull form for both the theories. The model explains the influence of physical and chemical properties of the component and the operating conditions on the failure times. It can be used for accelerated testing and for lncorporating reliability at product design stage.Ph. D

An object‐oriented decision support system for maintenance management

As the world approaches a new millennium, more and more industrial and manufacturing processes are being computerized and rapid retrieval and use of necessary information is vital if an organization is to remain competitive. The present work develops a computerized decision support system to assist in maintenance planning. The system design and analysis, and the decision support system design and development are all developed in an object‐oriented environment. The support system is driven by maintenance performance indices. Both object‐oriented databases and relational databases are used, for transient and permanent entities respectively. A knowledge base with if‐then rules is developed for fault diagnosis and repair. The methodology was applied to a powder coating plant to develop its maintenance decision support system.</jats:p

Case study: RCM – yes, no or maybe?

The basic research question of this paper is how to determine the optimum maintenance concept for an industrial installation in a practical, i.e. with a reasonable input effort, way. The paper starts out with a critical review of maintenance concepts available from literature. These concepts are considered for use in a specific case, i.e. a paint spraying robot in an automobile manufacturing plant, and it is decided to implement a RCM‐like approach. The original RCM concept is modified in order to better fit the specific needs in terms of technical and organizational requirements of the company in question. The paper concludes with some general thoughts on the applicability of such an RCM‐like concept for the company in question.</jats:p

DEVELOPMENT OF FLEXIBLE SIMULATION MODELS OF PRODUCTION SYSTEMS ON THE WORLD WIDE WEB

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