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The tensile fracture of mild steel

Citation

Clausing, Don Paul (1966) The tensile fracture of mild steel. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechTHESIS:07222014-133942786

Abstract

The fibrous and cleavage tensile fracture of an annealed mild steel was investigated. Round tensile specimens of two geometries, one straight and one with a circumferential notch, were pulled at temperatures between room temperature and liquid nitrogen temperature. Tensile fractures occurred at average strains from 0.02 to 0.87. The mechanism of fibrous fracture at room temperature was investigated metallographically. The stress-strain values at which fibrous and cleavage fractures are initiated were determined.

Many fine microcracks, which are associated with pearlite colonies and inclusion stringers, develop prior to fibrous fracture. The macrofracture, which leads to final separation of the tensile specimen, is initiated by the propagation of a microcrack beyond the microstructural feature with which it is associated. Thus, the fibrous fracture of mild steel does not develop by the gradual growth and coalescence of voids that are large enough to be visible in the optical microscope. When the microcracks begin to open and propagate, final fracture quickly follows. Axial cracks are a prominent feature of the macrofracture that forms in the interior of the specimen immediately before final fracture.

The Bridgman distribution of stresses is not valid in a notched tensile specimen. Fibrous and cleavage fractures occur at approximately the same value of maximum tensile stress. When the maximum tensile stress that is necessary for cleavage fracture is plotted against the corresponding maximum tensile strain, the result is an unique locus.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Materials Science
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Materials Science
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Wood, David Shotwell (advisor)
  • Clark, Donald S. (co-advisor)
Thesis Committee:
  • Unknown, Unknown
Defense Date:1 January 1966
Record Number:CaltechTHESIS:07222014-133942786
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:07222014-133942786
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:8584
Collection:CaltechTHESIS
Deposited By: Benjamin Perez
Deposited On:22 Jul 2014 21:00
Last Modified:22 Jul 2014 21:00

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