ELECTRIC-POTENTIAL TECHNIQUE FOR DETERMINING SLOW CRACK GROWTH

Abstract

Slow crack growth was followed as a function of applied load during fracture toughness testing of high-strength sheet materials (4340 and 300M steels) by means of continuous measurement of electric potential field changes across the crack. The instrument employed is a commercially available millionmeter and uses the ammetervoltmeter measurement method with a minimum of current passing through the test specimen. Voltage drop across the crack, rather than resistance, is measured. Electronic and mechanical testing techniques are described. Typical potential field distribution diagrams illustrate the potential change with crack growth. A single calibration curve for crack size versus potential drop may be obtained independent of material and specimen configuration by maintaining geometrical similarity of current and potential contacts. Calibration data are readily obtainable for any specimen design by duplicating the specimen in aluminum foil and simulating crack growth with a razor.

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Document Details

Document Type
Technical Report
Publication Date
Dec 01, 1963
Accession Number
AD0432497

Entities

People

  • Albert A. Anctil
  • Eric B. Kula
  • Eugene Dicesare

Organizations

  • United States Army Research Laboratory

Tags

Communities of Interest

  • Weapons Technologies

DTIC Thesaurus Topics

  • Aluminum
  • Aluminum Foil
  • Calibration
  • Crack Propagation
  • Fracture (Mechanics)
  • Government Procurement
  • Heat Treatment
  • Materials
  • Materials Testing
  • Measurement
  • Mechanical Engineering
  • Mechanics
  • Resistance
  • Standards
  • Test Methods
  • Voltage
  • Yield Strength

Fields of Study

  • Materials science

Readers

  • Aerospace Test and Evaluation
  • Materials Science (Mechanical Engineering).
  • Systems Analysis and Design

Technology Areas

  • Microelectronics