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  • 1
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    Probabilistic structural analysis to quantify uncertainties associated with turbopump blades (1989)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal (ISSN 0001-1452); 27; 809-813
    Format: text
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  • 2
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    Advanced probabilistic methods for quantifying the effects of various uncertainties in structural response (1988)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The effects of actual variations, also called uncertainties, in geometry and material properties on the structural response of a space shuttle main engine turbopump blade are evaluated. A normal distribution was assumed to represent the uncertainties statistically. Uncertainties were assumed to be totally random, partially correlated, and fully correlated. The magnitude of these uncertainties were represented in terms of mean and variance. Blade responses, recorded in terms of displacements, natural frequencies, and maximum stress, was evaluated and plotted in the form of probabilistic distributions under combined uncertainties. These distributions provide an estimate of the range of magnitudes of the response and probability of occurrence of a given response. Most importantly, these distributions provide the information needed to estimate quantitatively the risk in a structural design.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA. Lewis Research Center, Lewis Structures Technology, 1988. Volume 2: Structural Mechanics; p 219-232
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  • 3
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    Quantifying uncertainties in the structural response of SSME blades (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: To quantify the uncertainties associated with the geometry and material properties of a Space Shuttle Main Engine (SSME) turbopump blade, a computer code known as STAEBL was used. A finite element model of the blade used 80 triangular shell elements with 55 nodes and five degrees of freedom per node. The whole study was simulated on the computer and no real experiments were conducted. The structural response has been evaluated in terms of three variables which are natural frequencies, root (maximum) stress, and blade tip displacements. The results of the study indicate that only the geometric uncertainties have significant effects on the response. Uncertainties in material properties have insignificant effects.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA. Lewis Research Center Structural Integrity and Durability of Reusable Space Propulsion Systems; p 167-173
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  • 4
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    Probabilistic SSME blades structural response under random pulse loading (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The purpose is to develop models of random impacts on a Space Shuttle Main Engine (SSME) turbopump blade and to predict the probabilistic structural response of the blade to these impacts. The random loading is caused by the impact of debris. The probabilistic structural response is characterized by distribution functions for stress and displacements as functions of the loading parameters which determine the random pulse model. These parameters include pulse arrival, amplitude, and location. The analysis can be extended to predict level crossing rates. This requires knowledge of the joint distribution of the response and its derivative. The model of random impacts chosen allows the pulse arrivals, pulse amplitudes, and pulse locations to be random. Specifically, the pulse arrivals are assumed to be governed by a Poisson process, which is characterized by a mean arrival rate. The pulse intensity is modelled as a normally distributed random variable with a zero mean chosen independently at each arrival. The standard deviation of the distribution is a measure of pulse intensity. Several different models were used for the pulse locations. For example, three points near the blade tip were chosen at which pulses were allowed to arrive with equal probability. Again, the locations were chosen independently at each arrival. The structural response was analyzed both by direct Monte Carlo simulation and by a semi-analytical method.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA. Lewis Research Center Structural Integrity and Durability of Reusable Space Propulsion Systems; p 161-166
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  • 5
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    NESTEM-QRAS: A Tool for Estimating Probability of Failure (2002)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: An interface between two NASA GRC specialty codes, NESTEM and QRAS has been developed. This interface enables users to estimate, in advance, the risk of failure of a component, a subsystem, and/or a system under given operating conditions. This capability would be able to provide a needed input for estimating the success rate for any mission. NESTEM code, under development for the last 15 years at NASA Glenn Research Center, has the capability of estimating probability of failure of components under varying loading and environmental conditions. This code performs sensitivity analysis of all the input variables and provides their influence on the response variables in the form of cumulative distribution functions. QRAS, also developed by NASA, assesses risk of failure of a system or a mission based on the quantitative information provided by NESTEM or other similar codes, and user provided fault tree and modes of failure. This paper will describe briefly, the capabilities of the NESTEM, QRAS and the interface. Also, in this presentation we will describe stepwise process the interface uses using an example.
    Keywords: Quality Assurance and Reliability
    Type: Fifth Annual Workshop on the Application of Probabilistic Methods for Gas Turbine Engines; 197-220; NASA/CP-2002-211682
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  • 6
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    Probabilistic structural analysis to quantify uncertainties associated with turbopump blades (1988)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A probabilistic study of turbopump blades has been in progress at NASA Lewis Research Center for over the last two years. The objectives of this study are to evaluate the effects of uncertainties in geometry and material properties on the structural response of the turbopump blades to evaluate the tolerance limits on the design. A methodology based on probabilistic approach was developed to quantify the effects of the random uncertainties. The results indicate that only the variations in geometry have significant effects.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-TM-100278 , E-3919 , NAS 1.15:100278
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  • 7
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    Probabilistic structural analysis to quantify uncertainties associated with turbopump blades (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A probabilistic study of turbopump blades has been in progress at NASA Lewis Research Center for over the last two years. The objectives of this study are to evaluate the effects of uncertainties in geometry and material properties on the structural response of the turbopump blades to evaluate the tolerance limits on the design. A methodology based on probabilistic approach has been developed to quantify the effects of the random uncertainties. The results of this study indicate that only the variations in geometry have significant effects.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA PAPER 87-0766
    Format: text
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  • 8
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    Shrouded CMC Rotor Blades for High Pressure Turbine Applications (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The density of Ceramic Matrix Compos-ite(CMC) materials is approximately 1/3 the density of metals currently used for High Pressure Turbine(HPT) blades. A lower density, and consequently lower centrifugal stresses, increases the feasibility of shrouding HPT blades. Shrouding HPT blades improves aerodynamic eciency, especially for low aspect ratio turbine blades. This paper explores aerodynamic and structural issues associated with shrouding HPT rotor blades. Detailed Navier-Stokes analysis of a rotor blade showed that shrouding improved blade row aerodynamic eciency by 1.3%, when the clearance was 2% of the blade span. Recessed casings were used. Without a shroud the depth of the recess equaled the clearance. With a shroud the recess depth increased by the shroud thickness, which included a knife seal. There was good agreement between the predicted stage eciency for the unshrouded blades and the experimentally measured efficiency. Structural analysis showed a strong interaction between stresses in the shroud and peak stresses at the hub of the blade. A thin shroud of uniform thickness only moderately increased maximum blade stress, but there were very high stresses in the shroud itself. Increasing shroud thickness reduced stresses in the shroud, but increased blade stresses near the hub. A single knife seal added to the thin shroud noticeably decreased maximum shroud stress, without increasing maximum blade stress. Maximum stresses due to pressure loads and combined pressure and centrifugal loads were nearly the same as the maximum stresses for individual pressure or cen-trifugal loads. Stresses due to a 100K temperature
    Keywords: Aircraft Design, Testing and Performance; Aerodynamics
    Type: GRC-E-DAA-TN57524 , ASME Turbo Expo; Jun 11, 2018 - Jun 15, 2018; Oslo; Norway
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  • 9
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    Design Concepts for Cooled Ceramic Composite Turbine Vane (2015)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: The objective of this work was to develop design concepts for a cooled ceramic vane to be used in the first stage of the High Pressure Turbine(HPT). To insure that the design concepts were relevant to the gas turbine industry needs, Honeywell International Inc. was subcontracted to provide technical guidance for this work. The work performed under this contract can be divided into three broad categories. The first was an analysis of the cycle benefits arising from the higher temperature capability of Ceramic Matrix Composite(CMC) compared with conventional metallic vane materials. The second category was a series of structural analyses for variations in the internal configuration of first stage vane for the High Pressure Turbine(HPT) of a CF6 class commercial airline engine. The third category was analysis for a radial cooled turbine vanes for use in turboshaft engine applications. The size, shape and internal configuration of the turboshaft engine vanes were selected to investigate a cooling concept appropriate to small CMC vanes.
    Keywords: Aeronautics (General); Composite Materials; Structural Mechanics
    Type: NASA/CR-2015-218390 , E-18975 , GRC-E-DAA-TN16487
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  • 10
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    Probabilistic structural analysis of aerospace components using NESSUS (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Probabilistic structural analysis of a Space Shuttle main engine turbopump blade is conducted using the computer code NESSUS (numerical evaluation of stochastic structures under stress). The goal of the analysis is to derive probabilistic characteristics of blade response given probabilistic descriptions of uncertainties in blade geometry, material properties, and temperature and pressure distributions. Probability densities are derived for critical blade responses. Risk assessment and failure life analysis is conducted assuming different failure models.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA PAPER 88-2373 , Structures, Structural Dynamics and Materials Conference; Apr 18, 1988 - Apr 20, 1988; Williamsburg, VA; United States
    Format: text
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