Influence of Fatigue Crack Closure on the Growth Rate of Surface Flaws

Abstract

Inconsistent experimental results of fatigue crack closure studies over the past 15 years have caused recent investigators to conclude that the fundamental phenomena controlling the crack driving mechanisms are not understood. A major contributor to this misunderstanding is an inadequate understanding of the complex three-dimensional nature of closure. This is true for two-dimensional thru-the-thickness cracks as well as for three-dimensional part-thru surface cracks. To assess the three-dimensional influences of fatigue crack closure on the growth rate of surface flaws, an experimental investigation was conducted using a rectangular plate of polymethylmethacrylate (PMMA) material loaded in four-point bending. The use of transparent PMMA material and a Newton optical interferometer system with a laser light source provided the capability to simultaneously measure three-dimensional crack opening displacement (COD) profiles and closure loads (Pc1).

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Document Details

Document Type
Technical Report
Publication Date
Feb 01, 1994
Accession Number
ADA279130

Entities

People

  • William A. Troha

Organizations

  • Wright Laboratory

Tags

Communities of Interest

  • Air Platforms

DTIC Thesaurus Topics

  • Accuracy
  • Air Force
  • Bending Moments
  • Crack Propagation
  • Cutting Tools
  • Cyclic Loads
  • Data Analysis
  • Engineering
  • Geometry
  • Light Sources
  • Materials
  • Materials Laboratories
  • Measurement
  • Mechanics
  • Modulus Of Elasticity
  • Three Dimensional
  • Two Dimensional

Readers

  • Materials Science (Mechanical Engineering).
  • Strategic Security Studies
  • Structural Health Monitoring of Composite Structures.

Technology Areas

  • Directed Energy