ISSN:0748-8017    

DOI:10.1002/qre.4680020302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractHot‐spot detection, a thermographic technique with liquid crystals, marks hot regions on a surface. The use of this highly sensitive method in failure analysis of integrated devices allows the detection of points on a chip where electrical power is converted into heat. Points such as these are often indicative of a fault, e.g. a leakage path or an increase in transfer resistance. The technique is based on the birefringence of a liquid crystal (LC) in the anisotropic state below the clearing temperature(Tc). Above this temperature, in the isotropic state, the effect disappears. The device under test, covered with the LC, is observed below the clearing point in polarized light with a crossed polarizer and analyser. Owing to the optical rotation of the anisotropic LC the image is bright. At hot spots the LC changes to the isotropic state and a dark spot is produced. A decisive factor for the thermal resolution of the technique is the precise temperature adjustment of the tested device. With lateral resolution of some tenths of a μ‐m it is still possible to detect current paths with dissipation of 50 to 500μW. The sensitivity can be increased further. Square‐wave pulses of selectable voltage, frequency and duty cycle are used to drive the test item. Four examples from failure analysis demonstrate the possibilities of using hot‐spot thermography, the main features of which are speed, uncomplicated handling and depth of in

ISSN:0748-8017    

DOI:10.1002/qre.4680020303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractFailure mode and effect analysis (FMEA) is often performed when assessing equipment reliability. Some failure modes can occur that are only revealed when a demand is placed upon the system, thus causing a hazard. Such failures are only detectable by regular proof testing of the system. Availability calculations generally do not take into consideration down‐time caused by the duration of such proof tests. Testing of a large system is both laborious and time consuming, and may cause either partial or total system unavailability. Microprocessor based equipment reduces the duration of this task, but the question arises of how often?' The following method shows how the optimum proof test interval can be determined based on Markovian reliability models. It should be borne in mind that figures used in reliability prediction should not be considered to be precise data. Such figures should be treated as approximations for comparative use only. The purpose of this paper is to provide a guide for use by engineers involved in reliability/availability prediction; it serves to replace intuitive decision

ISSN:0748-8017    

DOI:10.1002/qre.4680020304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractThis paper discusses the particular test needs of non‐standard, application‐specific integrated circuits (ASICs). It covers the need for accurate device simulation integrated with a post‐processor and test system software, to enable cost‐effective testing to be pe

ISSN:0748-8017    

DOI:10.1002/qre.4680020305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractThis paper describes, and gives a mathematical analysis of, the performance of two makes of CRT bleed resistors which exhibit markedly different characteristics under heat soak conditions. By examining the observed resistance changes with temperature, and relating these to the Arrhenius equation, the reaction activation energies can be determined.Further analysis of the power consumption characteristics of the resistors leads to the establishment of resistance‐time curves for both makes of resistor. These indicate very different conclusions than might otherwise have been drawn from initial test data. Finally the Monte Carlo' simulation technique is used to determine the most likely survival characteristics in a field situation, and a quantitative assessment of the reliability of CRTs using these bleed resistors is given.The construction of the resistor body is common to both makes and comprises a resistor substrate enclosed within an overcoat which is in turn encapsulated in epoxy. One make (type A) is a glass thick film structure, whereas the other is a polymer thick film syste

ISSN:0748-8017    

DOI:10.1002/qre.4680020306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractA typical flexible manufacturing system, Westland Helicopters' sheet metal detail manufacturing complex, has been analysed for reliability. The techniques of fault tree analysis and event tree analysis are presented and their applicability to this study investigated. Event tree analysis has been found to be a more effective method for analysing manufacturing systems. The failure states of the system have been identified from the construction of an event tree which considers random hardware faults that influence production. Failure rate data have been used to quantify the critical production failure states in terms of machine failures. Estimates are made of the system's MTTF and percentage availability using typical MTTR figures. The probability that a selected production route fails to complete the manufacture of a set of parts is also evaluated. A dependency of systems reliability on the production demand has been discovered, and a possible method for modelling and assessing the reliability of systems capable of producing several products is proposed.

ISSN:0748-8017    

DOI:10.1002/qre.4680020307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractDetermination of the optimum equipment replacement policy and time is of great economic importance. After a brief survey of the models which have been used for decision making, the paper looks at methods for detecting and quantifying growth of failure frequency (peril rate) in repairable equipment. It examines the trend detection methods of Laplace and Mann when the peril rate varies as a power of equipment age and also applies them to some actual field failure data. An economic model is developed, based on total discounted future cost and providing for ongoing future technological growth. The cost comprises not only the conventional cost of ownership, but also the shortfall between an equipment's achieved benefit and that which would be achieved by an ideal equipment in the same demand environment. The inclusion of this shortfall, called incapacity cost', enables the replacement decision to be based not only on the deterioration of equipment but also on its performance inadequacy and on the availability of technological improvement in present and future challengers.The formulation of the cost model is such that for both a single‐replacement finite planning horizon and an infinite horizon the total discounted future cost is readily computed for a range of alternative replacement times and the optimum replacement programme thereby determined. The sensitivity of total cost to the replacement times and the sensitivity of the optimum times to the variability of assumed input data are easily examined.The application of the model to traffic signal equipment is described. In this application the total cost is shared between the nominal owner of the equipment and the communit

ISSN:0748-8017    

DOI:10.1002/qre.4680020308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractFor the prediction of life leading to fatigue crack initiation, a method for performing a cycle‐by‐cycle local stress analysis at the stress concentration area of a structural component was developed. Elastoplastic stress‐strain values along the hysteresis loop are traced for each load reversal in making the life prediction calculations. In this manner, the load sequence effect and the residual stress due to local yielding are inherently included.Neuber's rule and a linear rule were used with this method and compared. The results of life prediction were compared with test results. The use of the linear rule provided more accurate predictions than using other alternatives, including Miner's

ISSN:0748-8017    

DOI:10.1002/qre.4680020309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

ISSN:0748-8017    

DOI:10.1002/qre.4680020310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

ISSN:0748-8017    

DOI:10.1002/qre.4680020311

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY