Accession Number : ADA132600

Title :   Degradation of Fracture Toughness in Steels due to Prior Strain: A Predictive Model.

Descriptive Note : Master's thesis,

Corporate Author : NAVAL POSTGRADUATE SCHOOL MONTEREY CA

Personal Author(s) : Sanford,Gregory Benson

PDF Url : ADA132600

Report Date : Jun 1983

Pagination or Media Count : 83

Abstract : This thesis quantifies the relationship between prior plastic strain, fracture toughness (J sub Ic), plane strain fracture strain (epsilon sub fps), and yield strength (Q sub y) of HY-series steels at room temperature. Based upon initial J-integral test results of compact tensile specimens that showed a reduction in the fracture toughness with increasing of prestrain, a correlation has been developed where JIc is directly proportional to epsilon sub fps to the fourth power. Thus, small changes in epsilon sub fps will cause large changes in JIc. Further, it has been found that prestrain reduces epsilon sub fps by an amount equal to the prestrain. The combination of these two correlations provides a very simple method of estimating the fracture toughness subsequent to plastic straining. Scanning electron microscopy was used to measure the crack tip stretch zone width (SZW), which is a good estimate of the crack tip strain prior to fracture. The SZW does decrease with increasing prior plastic strain verifying the decrease in epsilon sub fps.

Descriptors :   *Steel, *Strength(Mechanics), *Fracture(Mechanics), Strain(Mechanics), Cracking(Fracturing), Plastic properties, Toughness, Degradation, Tensile properties, Correlation techniques, Electron microscopy, Models, Mathematical prediction, Theses

Subject Categories : Metallurgy and Metallography
      Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE