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A New Approach to Extreme Value Estimation Applicable to a Wide Variety of Random VariablesDesigning reliable structures requires an estimate of the maximum and minimum values (i.e., strength and load) that may be encountered in service. Yet designs based on very extreme values (to insure safety) can result in extra material usage and hence, uneconomic systems. In aerospace applications, severe over-design cannot be tolerated making it almost mandatory to design closer to the assumed limits of the design random variables. The issue then is predicting extreme values that are practical, i.e. neither too conservative or non-conservative. Obtaining design values by employing safety factors is well known to often result in overly conservative designs and. Safety factor values have historically been selected rather arbitrarily, often lacking a sound rational basis. To answer the question of how safe a design needs to be has lead design theorists to probabilistic and statistical methods. The so-called three-sigma approach is one such method and has been described as the first step in utilizing information about the data dispersion. However, this method is based on the assumption that the random variable is dispersed symmetrically about the mean and is essentially limited to normally distributed random variables. Use of this method can therefore result in unsafe or overly conservative design allowables if the common assumption of normality is incorrect.
Document ID
19970026131
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Holland, Frederic A., Jr.
(NASA Lewis Research Center Cleveland, OH United States)
Date Acquired
August 17, 2013
Publication Date
April 1, 1997
Publication Information
Publication: Physics and Process Modeling (PPM) and Other Propulsion R and T
Volume: 2
Subject Category
Structural Mechanics
Report/Patent Number
Paper-20
Accession Number
97N25479
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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