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A Study of Single and Polycrystalline Ingot Iron Under Repeated Stress


McClintock, Frank Ambrose (1950) A Study of Single and Polycrystalline Ingot Iron Under Repeated Stress. Bachelor's thesis, California Institute of Technology. doi:10.7907/A49D-6315.


Specimens of single and polycrystalline ingot iron were tested in a rotary bending fatigue machine and examined microscopically in order to check previous observations of slip and to study the nature of crack formation and growth. As has been reported, slip takes place on surfaces of high shear stress parallel to a <111> direction in the crystal lattice. In contrast to recent work, the slip was found to occur on wavy surfaces rather than pairs of crystallographic planes. Fatigue cracks were found to follow surfaces of high shear stress containing a <111> direction. The conclusion that fatigue failures are primarily shear failures is strengthened by a statistical explanation of the mechanism by which a microscopic shear failure can lead to the apparent tension failure commonly observed in rotary bending tests on polycrystalline iron. Microscopic observation of the polycrystalline specimens revealed that cracks originate at the grain boundaries before 30,000 cycles in a specimen which would very probably run for at least 106,000 cycles.

Item Type:Thesis (Bachelor's thesis)
Subject Keywords:(Mechanical Engineering and Mathematics)
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Mechanical Engineering
Minor Option:Mathematics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Hudson, Donald E.
Thesis Committee:
  • Unknown, Unknown
Defense Date:1949
Record Number:CaltechETD:etd-03272007-130713
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:1174
Deposited By: Imported from ETD-db
Deposited On:27 Mar 2007
Last Modified:31 Mar 2023 19:28

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PDF (McClintock_fa_1950.pdf) - Final Version
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