ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Aircraft Design, Testing and Performance  (6)
  • COMPOSITE MATERIALS  (6)
  • Quality Assurance and Reliability  (1)
  • 11
    facet.materialart.
    Unknown
    Detection of Delaminations in Composite Beams Using Piezoelectric Sensors (1994)
    In:  CASI
    Details
    Publication Date: 2019-08-17
    Description: This paper investigates the feasibility of a proposed technique for detecting delamination using piezoelectric layers or patches embedded or bonded to a composite structure. Variations in the voltage generated in the piezoelectric layers indicates the presence and location of delamination, when the structure is excited either externally or via actuators. The theoretical foundations of a method for predicting the dynamic response of delaminated composite beams with piezoelectric layers are described. The governing equations are presented for the case of external vibroacoustic excitation, as well as, for the case of locally induced vibrations by some of the embedded piezoelectric elements. An exact solution is developed within the limits of linear laminate theory. Applications illustrate the feasibility of delamination detection in cantilever beams. The results illustrate that the proposed technique may provide accurate detection of the presence, size, and location of a delamination.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-TM-106611 , E-8894 , NAS 1.15:106611 , AIAA PAPER 94-1754 , Structures, Structural Dynamics and Materials Conference; Apr 18, 1994 - Apr 21, 1994; Hilton Head, SC; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 12
    facet.materialart.
    Unknown
    A Subsonic Aircraft Design Optimization With Neural Network and Regression Approximators (2004)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The Flight-Optimization-System (FLOPS) code encountered difficulty in analyzing a subsonic aircraft. The limitation made the design optimization problematic. The deficiencies have been alleviated through use of neural network and regression approximations. The insight gained from using the approximators is discussed in this paper. The FLOPS code is reviewed. Analysis models are developed and validated for each approximator. The regression method appears to hug the data points, while the neural network approximation follows a mean path. For an analysis cycle, the approximate model required milliseconds of central processing unit (CPU) time versus seconds by the FLOPS code. Performance of the approximators was satisfactory for aircraft analysis. A design optimization capability has been created by coupling the derived analyzers to the optimization test bed CometBoards. The approximators were efficient reanalysis tools in the aircraft design optimization. Instability encountered in the FLOPS analyzer was eliminated. The convergence characteristics were improved for the design optimization. The CPU time required to calculate the optimum solution, measured in hours with the FLOPS code was reduced to minutes with the neural network approximation and to seconds with the regression method. Generation of the approximators required the manipulation of a very large quantity of data. Design sensitivity with respect to the bounds of aircraft constraints is easily generated.
    Keywords: Aircraft Design, Testing and Performance
    Type: NASA/TM-2004-213059 , AIAA Paper 2004-4606 , E-14504 , 10th Multidisciplinary Analysis and Optimization Conference; Aug 30, 2004 - Sep 01, 2004; Albany, NY; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 13
    facet.materialart.
    Unknown
    Efficient Evaluation and Optimization of Structural Reliability (1997)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Use of approximations for calculating the structural failure probability under uncertainties is a necessary aspect. But efficient use of suitable approximations at different stages of reliability prediction and design makes this valuable tool practical for many large scale structures. This research addresses the modern approximation concepts and their utility in structural reliability estimation. Emphasis is placed on building higher order approximations using intervening variables to closely represent the nonlinear limit state functions. Several test problems with highly nonlinear performance functions are used to demonstrate the accuracy of the proposed method. Many of the structural problems are modeled and simulated using the finite element methods (FEM) for obtaining a detailed structural response. FEM is a computationally intensive numerical procedure with a large number of degrees of freedom. With an increase in the complexity of the structural model and the multidisciplinary nature of analyses, the number of limit states and their computation increases very significantly. The requirement of frequent repetitive analysis of the structure hinders the utility of any tool and discourages that approach from being used. One particular tool which faces this difficulty is the computation of the structural reliability under parametric uncertainties.
    Keywords: Quality Assurance and Reliability
    Type: Paper-25 , Physics and Process Modeling (PPM) and Other Propulsion R and T; 2; NASA-CP-10193-Vol-2
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...