Variability in Flight-By-Flight Crack Growth Rate Behavior

Abstract

The initial result of variable amplitude fatigue crack growth rate test program are presented. The test program was designed to study the influence that the stress intensity factor gradient (dK/da) had on crack growth rate behavior in 7075-T6 aluminum alloy. Constant stress intensity factor conditions were used to study this behavior, using a twenty-four inch wide center-cracked panel. Based on earlier work by Hillberry on constant amplitude crack growth rate behavior, a three-parameter lognormal distribution function was selected to describe the crack growth rate data. Comparison of crack lengths showed no gradient effect. Parameters of the statistical distribution were compared using the secant and incremental polynomial methods of differentiation and for different flight intervals achieved by removing points prior to the differentiation process.

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Document Details

Document Type
Technical Report
Publication Date
Jan 01, 1978
Accession Number
ADA374011

Entities

People

  • Harold D. Stalnaker
  • Margery E. Artley

Organizations

  • Flight Dynamics Laboratory

Tags

Communities of Interest

  • Space

DTIC Thesaurus Topics

  • Air Force
  • Aluminum Alloys
  • Coefficients
  • Distribution Functions
  • Flight Loads
  • Government Procurement
  • Governments
  • Intensity
  • Measurement
  • Normal Distribution
  • Standards
  • Statistical Analysis
  • Steady State
  • Stress Intensity Factors
  • Structural Integrity
  • Test Equipment
  • Test Methods

Readers

  • Approximation Theory.
  • Materials Science (Mechanical Engineering).
  • Statistical inference.