Computational method for load enhancement factors
First Claim
1. A method of computing at least one of a Load Factor, a Life Factor and a Load Enhancement Factor using Modified Joint Weibull Analysis, comprising the steps of:
- retrieving a test data set from at least one database;
analyzing the retrieved test data of the test data set for fit with a Weibull distribution model for the test data;
analyzing the retrieved test data to determine if at least two coupons have been tested and if applied loads and duration of testing at a component-level were varied;
computing at least one shape parameter for the Weibull distribution model and storing the at least one shape parameter;
computing at least one scale parameter for the Weibull distribution model of the test data and storing the at least one scale parameter;
computing a stress to life cycle relationship accounting for scatter in the test data through the Weibull distribution model of the test data by relating a log of the scale parameter of the Weibull distribution model with a log of a stress level of a stress to life cycle relationship; and
computing, using a processor, the at least one of a Life Factor, a Load Factor and a Load Enhancement Factor as a function of a slope and an intercept of the computed stress to life cycle relationship, thereby accounting for scatter in the at least one Life Factor, a Load Factor and a Load Enhancement Factor.
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Abstract
The computation of a Load Factor, a Life Factor or a Load Enhancement Factor using Modified Joint Weibull Analysis may include retrieving a test data set from at least one database and analyzing the data retrieved for fit with a Weibull distribution model. The test data may be analyzed to determine if at least two coupons have been tested and if applied loads and duration of testing at a component-level were varied. A shape parameter may be calculated for the Weibull distribution model. A scale parameter may be calculated for the Weibull distribution of the data. A stress to life cycle relationship may be calculated to account for scatter in the data through the Weibull distribution data. The Life Factor, the Load Factor or the Load Enhancement Factor may be calculated based on the stress to life cycle relationship to account for scatter.
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Citations
37 Claims
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1. A method of computing at least one of a Load Factor, a Life Factor and a Load Enhancement Factor using Modified Joint Weibull Analysis, comprising the steps of:
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retrieving a test data set from at least one database; analyzing the retrieved test data of the test data set for fit with a Weibull distribution model for the test data; analyzing the retrieved test data to determine if at least two coupons have been tested and if applied loads and duration of testing at a component-level were varied; computing at least one shape parameter for the Weibull distribution model and storing the at least one shape parameter; computing at least one scale parameter for the Weibull distribution model of the test data and storing the at least one scale parameter; computing a stress to life cycle relationship accounting for scatter in the test data through the Weibull distribution model of the test data by relating a log of the scale parameter of the Weibull distribution model with a log of a stress level of a stress to life cycle relationship; and computing, using a processor, the at least one of a Life Factor, a Load Factor and a Load Enhancement Factor as a function of a slope and an intercept of the computed stress to life cycle relationship, thereby accounting for scatter in the at least one Life Factor, a Load Factor and a Load Enhancement Factor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A method of calculating a Load Enhancement Factor for a composite structure using Weibull Regression Analysis, comprising the steps of:
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obtaining coupon test data of a material from which the composite structure is formed; applying a Weibull distribution regression function to the coupon test data to develop an estimated stress to fatigue life curve and applying an equation to relate the log of a scale parameter of the Weibull distribution regression function with the log of a stress level of the stress to fatigue life curve; implementing an estimation procedure to incorporate a stress to fatigue life relationship in the calculation of the Load Enhancement Factor through an intercept and a slope of the estimates of the stress to fatigue life curve; and specifying, by a user, a confidence level defined in a stress level of a fatigue cycle distribution; and calculating, using a processor, the Load Enhancement Factor using a variance and a co-variance matrix associated with the confidence level and representing the intercept and the slope of the stress to fatigue life curve and developed from the estimation procedure and wherein the Load Enhancement Factor is a scaled ratio of an expected failure stress and the stress level upon which the confidence level is based. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36)
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37. A method of evaluating a composite component of an aircraft, comprising the steps of:
calculating a Load Enhancement Factor of the composite component of the aircraft using Modified Joint Weibull Analysis, wherein calculating the Load Enhancement Factor comprises the steps of; retrieving a test data set from at least one database; analyzing the retrieved test data of the test data set for fit with a Weibull regression model; computing at least one scale parameter for the Weibull regression model; calculating a stress to life cycle relationship accounting for scatter in the retrieved test data through the Weibull regression model of the retrieved test data by relating a log of the scale parameter of the Weibull regression model with a log of a stress level of a stress to life cycle relationship; and calculating, using a processor, the Load Enhancement Factor as a function of a slope and an intercept of the stress to life cycle relationship.
Specification