Có 40+ tài liệu thuộc chủ đề "thiết kế cơ khí"
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the reliability of relatively simple systems with series and parallel assemblies, to estimations of the reliability of multi-state systems with random failure occurrences and repair times (i.e. Reliability assessment in this context is considered during the preliminary or schematic design phase of the engineering design process, with an estimation of the probability that items of equipment will perform their intended...
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Table 3.7 Failure mode effect severity classifications. 1 Catastrophic The occurrence of failure may result in death or equipment loss. A 2 Critical The occurrence of failure may result in severe injury. B 3 Marginal The occurrence of failure may result in minor injury. C 4 Minor The failure is not serious enough to lead to injury. 1 I Frequent...
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The last part of the curve, the increasing hazard rate region, is designated the. ‘wear-out phase’ of the equipment. In the calculations for reliability, it is important to note that reliability is an indirect function of the probability of the occurrence of failure.. The probability of the occurrence of failure is given by the failure distribution, or failure probability (FP)...
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α 0 = the total number of items put on test at time t = 0, α S = the number of items surviving at time t or at t + Δt.. A more common notation for the ith component reliability is expressed in terms of the mathematical constant e. The mathematical constant e is the unique real number, such...
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This constitutes an analysis of the rows of the matrix, in which. This constitutes an analysis of the columns of the matrix, in which. where m is the number of performance parameters, n is the number of design alternatives, and OPI lies in the range 0–100 and can thus be indicated as a per- centage value.. 3.3.1.5 Labelled Interval Calculus....
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all-parts only flow 2 . With the labelled interval of displacement between 0 . 5 × 10 −3 and 6 × 10 −3 cu- bic metre per revolution and the labelled interval of RPM in the interval of 75 to 150 RPM, the pumps can produce flows only in the interval of 2 . The elimination condition is true in...
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The overall performance index, OPI, can be calculated as. The overall performance index, OPI, is a combination of the parameter perfor- mance index, PPI, and the system performance index, SPI, and indicates the over- all performance of the operational parameters (PPI), and the overall contribution of the system’s items on the system (SPI) itself.. However, as the main use of...
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presence of non-linear properties (for example, in the modelling of performance characteristics of relief valves, non-return valves, end stops, etc.).. In engineering design, and in particular in the FMEA, it is common not to know the precise values of quantities, especially in the early design stages. It would thus be more intuitive to be able to relate design criteria in...
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These modifiers change the shape of a fuzzy set using mathematical operations on each point of the set. In the above table, the variable y represents each member- ship value in the fuzzy set, and A represents the entire fuzzy set (i.e. When a modifier is used in descriptive expressions, it can be used in upper or lower case (i.e....
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In traditional propositional logic, there are two very important inference rules as- sociated with implication and proposition, specifically the inferences modus ponens and modus tollens.. Modus ponens:. Premise 1: ‘x is A’;. Premise 2: ‘IF x is A THEN y is B’;. Consequence: ‘y is B’.. Modus ponens is associated with the implication ‘A implies B’. In terms of propo-...
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3.3.2.8 Uncertainty and Incompleteness in Engineering Design Analysis Uncertainty and incompleteness is inherent to engineering design analysis. Uncer- tainty, arising from the complex integration of systems, can best be expressed in qualitative terms, necessitating the results to be presented in the same qualitative measures. An important question is to decide what kind of possibility theory or fuzzy logic representation (in...
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3 .3 A n aly tic De v elo p m en t o f R elia b ility an d P er fo rm an ce in E n g in ee Table 3.16 Extract from FMECA worksheet of quantitative RAM analysis field study: motor RJS pump no. RJS pump no. Motor fails to start or drive pump. TLF...
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It is often more convenient to define an additional covariate, x o = 1, in order to allow the Weibull scale parameter to be included in the vector of regression coefficients, and the proportional hazards model expressed solely by the beta (shape parameter), together with the regression parameters and covariates. The PH reliability function is thus given by the expression...
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The parameter of the exponential distribution can also be estimated using the maxi- mum likelihood estimation (MLE) method. F is the number of groups of times-to-failure data points.. N i is the number of times to failure in the ith time-to-failure data group.. λ is the failure rate parameter (unknown a priori, only one to be found).. T i is...
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ment of the characteristics of failure. A major problem arises, though, when the measures and/or estimates of the Weibull parameters cannot be based on obtained data, and engineering design analysis cannot be quantitative. Credible and statisti- cally acceptable qualitative methodologies to determine the integrity of engineer- ing design in the case where data are not available or not meaningful are...
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The likelihood function is a fundamental concept in statistical inference. For instance, suppose an unknown random variable u that has values in the set U is to be estimated. Suppose also that the distribution of u depends on an unknown parameter F , with values in the parameter space F. F ) be the probability distribution of the variable u,...
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Thus, in the case of expert judgment, new estimate values in the form of a like- lihood function are incorporated into a Bayesian reliability model in a conventional way, representing updated information in the form of a posterior (a posteriori) prob- ability distribution that depends upon a prior (a priori) probability distribution that, in turn, is subject to the estimated...
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In any complex process plant, there are literally thousands of different systems, sub-systems, assemblies and components, which are all subject to failure and, there- fore, require specific attention with respect to the integrity of their design, design configuration as well as integration. Cost critical items are the relatively few systems items of which the engineer- ing costs (development, operational, maintenance...
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3.4 Application Modelling of Reliability and Performance in Engineering Design 253. equipment physical data such as type, make, size, mass, volume, number of parts;. equipment rating data such as performance, capacity, power (rating and factor), efficiency and output;. equipment measure data such as rotation, speed, acceleration, governing, fre- quency and flow in volume and/or rate;. equipment operating data such as...
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3.4 Application Modelling of Reliability and Performance in Engineering Design 263. 3.67 Hazards criticality analysis assembly condition. portion of the FMEA results are very similar at both levels. Thus, in a hazards criti- cality analysis of the condition of selected components for inclusion in a design, the following component condition data illustrated in Fig. Figure 3.68 illustrates a hazards criticality...