nach oben

1994 | Buch

Kapitel lesen Erstes Kapitel lesen

Quality and Reliability of Technical Systems

Theory — Practice — Management

verfasst von: Professor Dr. Alessandro Birolini

Verlag: Springer Berlin Heidelberg

Enthalten in: Professional Book Archive

Einloggen, um Zugang zu erhalten

Über dieses Buch

High reliability, maintainability, and safety are expected from complex equipment and systems. To build these characteristics into an item, failure rate and failure mode analyses have to be performed early in the design phase, starting at the com ponent level, and have to be supported by a set of design guidelines for reliability and maintainability as well as by extensive design reviews. Before production, qualification tests of prototypes must ensure that quality and reliability targets have been reached. In the production phase, processes and procedures have to be selec ted and monitored to assure the required quality level. For many systems, availabi lity requirements must also be satisfied. In these cases, stochastic processes can be used to investigate and optimize availability, including logistical support. This book presents the state of the art of the methods and procedures necessary for a cost and time effective quality and reliability assurance during the design and production of equipment and systems. It takes into consideration that: 1. Quality and reliability assurance of complex equipment and systems requires that all engineers involved in a project undertake a set of specific activities from the definition to the operating phase, which are performed concurrently to achieve the best performance, quality, and reliability for given cost and time schedule targets.

Inhaltsverzeichnis

Frontmatter

1. Basic Concepts, Tasks, and Organization of Quality and Reliability Assurance

Abstract

Quality and reliability assurance of complex equipment and systems requires from all engineers involved in a project a set of specific activities from the definition to the operating phase, performed concurrently to achieve the best performance, quality, and reliability for given cost and time schedule targets. This includes the definition of goals, planning and performing analyses and tests, selection and qualification of components and materials, management of the configuration, qualification and control of production processes and procedures, as well as quality and reliability growth during production. Many of these activities are engineering tasks, others are more for coordination and control. This chapter introduces the basic concepts and discusses the main tasks and organizational requirements necessary to assure cost effectively the quality and reliability of complex equipment and systems.

Alessandro Birolini

2. Reliability Analysis During the Design Phase

Abstract

Reliability analysis during the design phase is necessary to detect and eliminate reliability weaknesses as early as possible, and to perform comparative studies with respect to reliability. Such analysis includes failure rate and failure mode investigations as well as the verification that appropriate guidelines for reliability have been applied. This chapter introduces the methods for failure rate and failure mode analysis of complex electronic and electromechanical equipment and systems. Design guidelines for reliability are given in Section 3.4 and those for maintainability and software quality in Sections 4.3 and 5.3, respectively (for reliability tests one may refer to Chapters 3, 7, and 8). Section 2.2 deals with series/parallel structures and Section 2.3 with more complex topics (non series/parallel structures, stress/strength and drift analysis, elements with more than one failure mode), as well as with parallel models with load sharing (in particular warm and standby redundancy). A versatile program (CARP) for the computation of the predicted reliability of arbitrarily complex systems is presented in Section 2.4 (see Section 6.8.2 for the case of repairable systems). Theoretical foundations for this chapter may be found in Appendix A6.

Alessandro Birolini

3. Selection and Qualification of Components and Materials, Design Guidelines for Reliability

Abstract

Components and materials have a major impact on the quality and reliability of the equipment and systems in which they are used. Their selection and qualification must therefore be considered carefully. Besides cost and availability on the market, important selection criteria are the intended application (particular stresses), technology, quality, long-term behavior of relevant parameters, and reliability. Qualification includes characterization (at different thermal and electrical stresses), environmental tests, reliability tests, and failure analysis. This chapter deals first with the selection criteria for electronic components and then considers the qualification of complex integrated circuits (for the qualification of electronic assemblies one can refer to Section 8.3, screening of components and assemblies are considered in Sections 8.2 and 8.4, respectively). Failure modes, mechanisms, and analysis of electronic components are described in Section 3.3. Section 3.4 gives important design guidelines for reliability at the component and assembly level.

Alessandro Birolini

4. Maintainability Analysis During the Design Phase, Design Guidelines for Maintainability

Abstract

At the equipment and system level, maintainability has a significant influence on reliability and availability. This is particularly true if redundancy has been implemented and redundant parts can be repaired on line, i.e. without interruption of operation. Maintainability thus represents an important parameter in the optimization of the life-cycle cost (LCC). Achieving a high maintainability target requires appropriate activities which must be started early in the design phase and be coordinated by a maintenance concept. To this belong fault detection and isolation (attained with built-in tests), partitioning of the equipment or system into almost independent last repairable units (spare parts at equipment or system level), and realization of logistical support (also including after-sales service). Because of the diversity of equipment and systems as well as maintainability requirements, a maintenance concept must generally be tailored to the specific project considered. After a brief discussion of the basic terms, this chapter introduces the maintenance concept as applied to complex equipment and systems, and deals then with design guidelines for maintainability and testability, maintainability calculation techniques, and basic models for spare part provisioning.

Alessandro Birolini

5. Software Quality Assurance

Abstract

Computer software plays an increasingly important role in equipment and systems, both in terms of technical relevance and of development costs (often higher than 50% of the total costs even for small systems). Unlike hardware, software does not go through a production phase, since for a given application it can be copied without errors. Also in contrast to hardware, software cannot break or wear out. However, it can fail to satisfy its required function because of defects which manifest themselves while the system is operating (dynamic defects). A fault in the software is thus still caused by a defect, even if it appears randomly in time. Software problems are thus primarily quality problems and should be solved with quality assurance tools (configuration management, testing, and quality data reporting systems). This chapter gives an introduction to the concept and tools of software quality assurance, showing in particular the importance of preventive actions. Because of their utility in debugging complex software packages, models for software quality growth are also briefly considered.

Alessandro Birolini

6. Reliability and Availability of Repairable Systems

Abstract

Reliability and availability analysis of repairable systems is generally performed using stochastic processes, including Markov, semi-Markov, and semi-regenerative processes (as in Section 2, system designates the highest integration level of the item considered). The mathematical foundation of these processes can be found in Appendix A7 and the main equations for Markov and semi-Markov processes are summarized in Table 6.2. This chapter investigates systematically the reliability models encountered in practical applications. To unify the models and simplify calculations, Sections 6.2 – 6.6 assume that the system has only one repair crew and that no further failures can occur at system down. Starting from constant (time independent) values, repair and failure rates are generalized up to the case in which the process involved remains regenerative (often with just one or a few regeneration states). Section 6.7 then deals with approximate expressions for large series/parallel structures, assuming independent elements or using macro structures, and Sections 6.8 – 6.10 then consider briefly systems with complex structures as well as the influence of imperfect switching and of preventive maintenance. A powerful computer program (CARAP) is introduced in Section 6.8.2.

Alessandro Birolini

7. Statistical Quality Control and Reliability Tests

Abstract

Statistical quality control and reliability tests are performed for estimating or demonstrating quality and reliability characteristics on the basis of data collected from sampling tests. Estimation leads to a point or interval estimate of an unknown characteristic, demonstration is a test of a given hypothesis on the unknown characteristic in an acceptance test. The estimation and demonstration of an unknown probability is investigated in Section 7.1 for the case of a defective probability p and in Section 7.2.1 for reliability, maintainability, or availability. Estimation and demonstration of a constant failure rate λ or of an MTBF = 1/λ and of an MTTR are discussed in Sections 7.2.2 and 7.3, respectively. Basic models for accelerated tests and for goodness-of-fit tests are considered in Sections 7.4 and 7.5. To simplify the notation, the term sample will be used instead of random sample. Theoretical foundations for this chapter may be found in Appendix A8.

Alessandro Birolini

8. Quality and Reliability Assurance During the Production Phase

Abstract

Quality and reliability assurance activities have to be continued during the production phase. Key points are the monitoring and control of the production procedures and of the item’s configuration, the performance of in-process and final tests, the screening of critical components and assemblies, and the systematic collection, analysis, and correction of defects and failures. The last measure is basic for a learning process, whose aim is to optimize the improvement of quality and reliability during production, taking into account cost and time schedule limitations. This chapter introduces the general aspects of quality and reliability assurance during production, discusses test and screening procedures for electronic components and assemblies, introduces the concept of a test and screening strategy, and discusses some models for reliability growth during production.

Alessandro Birolini

Backmatter

Titel: Quality and Reliability of Technical Systems
verfasst von: Professor Dr. Alessandro Birolini
Verlag: Springer Berlin Heidelberg
Electronic ISBN: 978-3-662-02970-1
Print ISBN: 978-3-662-02972-5
DOI: https://doi.org/10.1007/978-3-662-02970-1

Springer Professional

Über dieses Buch

Inhaltsverzeichnis

Frontmatter

1. Basic Concepts, Tasks, and Organization of Quality and Reliability Assurance

2. Reliability Analysis During the Design Phase

3. Selection and Qualification of Components and Materials, Design Guidelines for Reliability

4. Maintainability Analysis During the Design Phase, Design Guidelines for Maintainability

5. Software Quality Assurance

6. Reliability and Availability of Repairable Systems

7. Statistical Quality Control and Reliability Tests

8. Quality and Reliability Assurance During the Production Phase

Backmatter