ISSN:0748-8017    

DOI:10.1002/qre.4680080102

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

年代:1992

数据来源: WILEY

摘要:

AbstractPorous sintered steels, because of porosity, present low tensile elongation and impact strength, suggesting reduced ductility and consequently poor reliability in structural applications. However, they present some typical features of ductile materials. To study the reliability of these materials, some Fe‐C‐P alloys were selected and tested by means of the Weibull analysis. The results are very encouraging, since they demonstrate that porous sintered steels may be compared to conventional structural steels. The values of the Weibull modulus are affected by the chemical composition, varying between 20 and 55. The aim of this paper is to correlate the microstructural characteristics and the fracture behaviour of the specimens, pointing out how the intrinsic properties of the microstructural constituents affect reliabil

ISSN:0748-8017    

DOI:10.1002/qre.4680080103

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

年代:1992

数据来源: WILEY

摘要:

AbstractCurrent developments in expert system technology make it possible to devise systems for on‐line quality control. Knowledge can be acquired and coded into a program to enable the operator or foreman to take immediate action to maintain product quality level through on‐line monitoring. This paper presents TEMPEX, a knowledge‐based statistical process control system for controlling the temperature in an injection moulding machine. The system is able to determine the process limits, detect out of control situations, find possible assignable causes and suggest corrective actions. The system is based on Leonardo, an expert system shell with a hybrid knowledge representation facility enabling the use of rules, rulesets, frames and procedures. The system contains 207 rules, 19 rule‐sets, 315 frames and 28 pro

ISSN:0748-8017    

DOI:10.1002/qre.4680080104

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

年代:1992

数据来源: WILEY

摘要:

AbstractShewhart charts are direct plots of the data and they have the potential to detect departures from statistical stability of unanticipated kinds. However, when one can identify in advance a kind of departure specifically feared, then a more sensitive detection statistic can be developed for that specific possibility.In this paper Cuscore statistics are developed for this purpose which can be used as an adjunct to the Shewhart chart. These statistics use an idea due to Box and Jenkins which is in turn an application of Fisher's score statistic. This article shows how the resulting procedures relate to Wald‐Barnard sequential tests and to Cusum statistics which are special cases of Cuscore statistics. The ideas are illustrated by a number of examples. These concern the detection in a noisy environment of (a) an intermittent sine wave, (b) a change in slope of a line, (c) a change in an exponential smoothing constant and (d) a change from a stationary to a non‐stationary state in a process rec

ISSN:0748-8017    

DOI:10.1002/qre.4680080105

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

年代:1992

数据来源: WILEY

摘要:

AbstractWhen accelerated life tests can be applied to simulate the normal product operating conditions, engineers usually terminate the test upon successfully running to a multiple of a prespecified bogey without any failure to demonstrate a required minimum reliability level. This testing philosophy is called ‘bogey test’ (or extended test) in the automotive industry and is a subset of type I censored tests in standard reliability literature. Sometimes engineers encounter the difficulty of using this reliability demonstration approach when incidents do occur during the test. The incident might be a legitimate failure or a withdrawal caused by external forces such as a broken fixture of a non‐functional power supply. This paper derives a two‐stage sampling plan for possible back‐up solution on planning and running a bogey test with possible occurrence of incidents. A Weibull distribution with a given shape parameter is assumed for the underlying life chara

ISSN:0748-8017    

DOI:10.1002/qre.4680080106

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

年代:1992

数据来源: WILEY

摘要:

AbstractA new scheme for multivariate statistical quality control is investigated and characterized. The control scheme consists of three steps and it will identify any out‐of‐control samples, select the subset of variables that are out of control, and diagnose the out‐of‐control variables. A new control variable selection algorithm, the backward selection algorithm, and a new control variable diagnosis method, the hyperplane methods, are proposed. It is shown by simulation that the control scheme is useful in cases where the process variables are correlated and where they are uncor

ISSN:0748-8017    

DOI:10.1002/qre.4680080107

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

年代:1992

数据来源: WILEY

摘要:

AbstractA signal‐to‐noise ratio proposed by Taguchi for ‘nominal the best’ can be made more flexible and used additionally for the cases ‘smaller the better’ and ‘larger the better’. The main feature which distinguishes this generalized ratio from Taguchi's signal‐to‐noise ratios is that its precise form is determined by the experimental data. Taken together with a transformation of the mean response it effectively identifies adjustment (signal) factors and dispersion factors. Examples are given to illustrate the routine operational procedure and also to demonstrate that Taguchi's signal‐to‐noise ratios can lead to inefficient, and sometimes incorrect, identification of design factors. Two important considerations are to preserve the evident appeal of the Taguchi method to engineers and also to provide a theoretical justification which is acceptable to statisticians.The principal objective of the joint transformation is to achieve approximate functional independence between the mean and variance in the new metric. This, in turn, leads to efficient identification of adjustment and dispersion factors. A comparison is made with a similar approach using Box

ISSN:0748-8017    

DOI:10.1002/qre.4680080108

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

年代:1992

数据来源: WILEY

摘要:

AbstractAn available numerical approximation to the Student'stdistribution is described and its use in the construction oft‐tests is presented. The result is a convenient and accurate computer based approach to the selection of the sample size and critical value to be used in at‐test. Computational logic for implementation of the approach is provided and the method is illustrated by an exam

ISSN:0748-8017    

DOI:10.1002/qre.4680080109

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

年代:1992

数据来源: WILEY

摘要:

AbstractFor censored life data, Kapur and Lamberson and O'Connor recommend the use of Johnson's formula for non‐parametric estimation of the failure distribution,F(t). The formula is used to calculate theadjusted ranksof the recorded failures, which are input into the median rank estimation equation ofF(t). It is our experience that Johnson's formula is fairly difficult for the reliability practitioner to understand and implement. Fortunately, an alternative formula has been developed which is much easier to use. It is demonstrated that the calculated adjusted ranks may be used in either the mean rank or median rank equations for the estimation ofF(t).The question which we pose is the following: How does the performance of Johnson's estimator compare with that of the more commonly known and understood Kaplan‐Meier, or product‐limit, estimator?' To answer this question, the Kaplan‐Meier procedure is evaluated with respect to its equivalent adjusted rank of recorded failures. The two procedures are determined to be equivalent with respect to adjusted rank criteria. Therefore, it is proved that with Johnson's estimator adapted for use with the mean rank estimator, the two procedures will yield identical estimates of the failure probabilities. Based upon this finding, it is our recommendation thatthe reliability practitioner use the alternative formula for generation of the adjusted ranks, followed by use of either the mean or median rank

ISSN:0748-8017    

DOI:10.1002/qre.4680080110

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

年代:1992

数据来源: WILEY

ISSN:0748-8017    

DOI:10.1002/qre.4680080111

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

年代:1992

数据来源: WILEY