A reliability simulation approach for use in the design process

World Abstracts on Microelectronics and Reliability hardware and software capability include saving of time, faster intervention in production and facilities for processing standardized data elsewhere in the company. This improves response to market requirements. Quality assurance, jnstqn-time with the worldwide EDIFACT stald~'d. DETLEVSIECH and ESERP.AROFRAHr~. Quality Europe (Germany), 49 (1991). Quality is a question of the interplay of companies and factories. With 80% of the faults detected only on the finished product the interchange of quality-related information gains strategic importance. The weakest link in the chain of just-in-time delivery contracts is the flow of quality-related information (requiring paperwork and manual processes). The concepts worked out by VDA-CAQ committees and resolved by the VDA-DGQ group on 28 November 1990 point to a new direction. Electronic data interchange is indispensable if qualityrelated data are interchanged rapidly, comprehensively, and economically. This article describes conventional methods and opposes them to new solutions already in use or about to be implemented. Implementing total quality management into reliability and maintainability. JAMESN. YOO and GEORGESMITHII. Proc. A. Reliab Maintainab. Symp., 547 (1991). Implementing total quality management (TQM) as defined by the Department of Defense (DoD) is a requirement for defense contractors of the future. Creating scenarios or techniques for TQM is on the agenda for most companies, whether defense-oriented or commerical. DoD is developing programs encouraging industry to adopt continuous process improvement plans and objectives during source selection. In addition, the Systems Reliability and Engineering Division of the Rome Air Development Center has written a training text on analysis methods useful in TQM activities. Now companies must establish methods for implementing these policies in their day-to-day business practices. This paper discusses the methodology for implementing TQM in reliability and maintainability (R&M) engineering. A maintenance policy for repairable systems based on opportanistie failure-rnte tolerance. XITONGZI-IENO and NASSER FARD. IEEE Trans. Reliab. 40(2), 237 (1991). An opportunistic hazard rate replacement policy for a repairable system with several types of units is presented. A unit is repaired at failure when the hazard rate falls in (0, L - u). A unit is replaced at failure when the hazard rate falls in (L - u , L). An operating unit is replaced when its hazard rate reaches L. When a unit is replaced because its hazard rate reaches L, all operating units with their hazard rates falling in (L - u, L) are replaced. The long-run mean cost rate as a function of L and u is derived. Optimal L and u are obtained to minimize the total maintenance cost rate. Application and analysis of results are demonstrated through a numerical example. The maintenance model is designed for a system with multi-type units. Each type has its own increasing hazard rate. Units are repaired or replaced depending on their hazard rate at a failure or active replacement of another unit. The repair interval, replacement limit, and replacement tolerance are determined to yield the optimal total maintenance cost rate. Modeling a shared-load k-out-of-n:G system. JIANJUNGSHAO and LEOHAaD R. LAMBERSON.IEEE Trans. Reliab. 40(2), 205 (1991). This paper presents a Markov model for analyzing the reliability and availability of an n-anit shared-load repairable k-out-of-n:G system with imperfect switching. The equations for both time-dependent and steady-state system availability are given. An inverse Laplace transform is used to solve the simultaneous differential equations for the nonrepairable case. A generalized analytic function for

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system reliability is obtained. Examples are provided to demonstrate the model and the impact of a load-sharing strategy on the reliability. The load-sharing strategy can improve system reliability and availability, if the controller and switching parameters are adequate. Our approach and solution are helpful to system engineers and reliability analysts. Rainbow net analysis of VAXelaster sytem availability. ALI~N M. JOHNSONJR and MICHAEL A. SCtlOEHFELDER. IEEE Trans. Reliab. 40(2), 226 (1991). A new modeling technique, rainbow nets, is used to evaluate the availability and mean time-to-interrupt of the VAXcluster. These results are compared to the exact analytic results showing that reasonable accuracy is achieved through simulation. The complexity of the rainbow net implemented for the VAXcluster does not increase as the number of processors increases, but remains constant. This is unlike a Markov model which increases in size exponentially. The constancy is achieved by using tokens with identity attributes (items) that can have additional attributes associated with them (features) which can exist in multiple states. The time to perform the simulation increases, but this is a polynomial increase rather than exponential. With rainbow nets, there is no restriction on distributions used for transition firing times. This freedom allows real situations to be modeled more accurately by choosing the distribution which best fits the system performance. This eliminates the need to make the many simplifying assumptions that are typically required to keep analytic calculations from becoming intractable. Optimal accelerated life-time plans that min|mize the maximum test-stress. RUSSELLR. BARTON.IEEE Trans. Reliab. 40(2), 166 (1991). This paper proposes a variation of the optimum accelerated life-test plans described by Nelson and others, and shows how to minimize the maximum test-stress that is required, subject to meeting a certain standard-deviation limit on the estimate. Previous optimal life-test plans have shown how to minimize the standard-deviation of the estimated product life, subject to a given maximum teststress. K-terminal reliability of hierarchies/networks. Toga' P. No.

IEEE Trans. Reliab. 40(2), 218 (1991). This paper describes a class of networks called hierarchical networks and shows how reliability can be computed efficiently in a hierarchical network. In particular, it describes an algorithm for the K-terminal problem: computing the probability that a set of k nodes (k > 1) can communicate through the network. The algorithm complexity is polynomial with a small degree. The exact degree depends on the distribution of the nodes that desire to communicate and the external gateways. A reliability simulation approach for use in the design process.

THOMASL. LANDERS, HAIVlDYA. TArA and ~ L. KING. IEEE Trans. Reliab 40(2), 177 (1991). We report a simulation model for use in the engineering design process. The simulation model facilitates reliability modeling by design engineers and reliability analysts early in the design process. The model applies to preliminary feasibility and design tradeoff studies. This paper describes the model, focuses on applications to mission reliability analysis, and gives a case study for the voice.communication system of the F-16 fighter aircraft. Sculabillty analysis in Oacefully-degradabie large systems. WALID A. NAJJARand JEAN-Luc GAUDiOT. IEEE Trans. Reliab. 40(2), 189 (1991). The availability of large multiprocessor systems raises new issues in the design of highly fault-tolerant architectures, As the number of active processors in large systems increases, its computing power