Prediction Of Creep Effects In Aircraft Structures

Item

Title
Prediction Of Creep Effects In Aircraft Structures
Description
A step-by-step numerical process for introducing thermal and creep effects into a redundant structural analysis was developed. This process involves seven consecutive steps: (1) elastic thermal stress determination; (2) unit displacement determination in terms of stiffness patterns; (3) relaxation increment determination; (4) real thermal stress determination resulting from summation of thermal and relaxation stresses; (5) incremental stress determination; (6) determination of stress redistribution attendant to creep; and (7) summation of elastic, thermal and creep stresses. Calibrations with model materials and structural elements, seeking verification of structural criteria introduced into numerical processes are demonstrated. An example problem for a delta wing illustrates method of calculation.

A critical re-examination of interpretative approaches for reducing creep data derived from materials tests into simplified form suitable for numerical analysis of redundant structures is introduced.

The creep test independent variables, time, temperature and stress, were examined with reference to their influence upon the dependent variable, strain. These examinations explored three fields of creep activity operative under conditions of (1) constant stress and constant temperature, (2) varying stress and constant temperature, and (3) constant stress and varying temperature. Comparisons of effects arising from constant stress and constant temperature exposures also are presented.
Date
1960
Index Abstract
Contrails and DTIC condensed
Photo Quality
Incomplete
Report Number
WADD TR 60-411 Part 1
Creator
Alesch, C. W.
Riparbelli, C.
Steurer, W. H.
Robe, W.
Corporate Author
Convair, A Division of General Dynamics Corporation Engineering Department
Laboratory
Flight Dynamics Laboratory
Date Issued
1960-04-15
Extent
246
Identifier
AD0261976
AD0261976
Access Rights
ASTIA
Distribution Classification
1
Contract
AF 33(616)-6567
DoD Project
1367
DoD Task
13584
DTIC Record Exists
Yes
Distribution Change Authority Correspondence
PER WL/AFSC (IST) ltr
Report Availability
Full text available by request
Abstract
A step-by-step numerical process for introducing thermal and creep effects into a redundant structural analysis was developed. This process involves seven consecutive steps: (1) elastic thermal stress determination; (2) unit displacement determination in terms of stiffness patterns; (3) relaxation increment determination; (4) real thermal stress determination resulting from summation of thermal and relaxation stresses; (5) incremental stress determination; (6) determination of stress redistribution attendant to creep; and (7) summation of elastic, thermal and creep stresses. Calibrations with model materials and structural elements, seeking verification of structural criteria introduced into numerical processes are demonstrated. An example problem for a delta wing illustrates method of calculation.

A critical re-examination of interpretative approaches for reducing creep data derived from materials tests into simplified form suitable for numerical analysis of redundant structures is introduced.

The creep test independent variables, time, temperature and stress, were examined with reference to their influence upon the dependent variable, strain. These examinations explored three fields of creep activity operative under conditions of (1) constant stress and constant temperature, (2) varying stress and constant temperature, and (3) constant stress and varying temperature. Comparisons of effects arising from constant stress and constant temperature exposures also are presented.
Provenance
IIT
Type
report
Subject
Airframes
Aerodynamic Loading
Creep
Beams (Structural)
Deformation
Structures
Elastic Properties
Test Methods
Stainless Steel
Mathematical Prediction
Copper
Mathematical Analysis
Sheets
Equations
Delta Wings
Thermal Stresses
Aircraft Panels
Beams (Electromagnetic)
Materials
Lead (Metal)
Load Distribution
Aluminum Alloys
Publisher
Wright-Patterson Air Force Base, OH : Wright Air Development Division, Air Research and Development Command, United States Air Force
Format
xvii, 246 pages : ill. ; 28 cm.
Distribution Conflict
No