The Effect of Grain Size on the Yielding Behavior of Very Low Carbon Steel.

Citation

Russell, Thomas Lee (1958) The Effect of Grain Size on the Yielding Behavior of Very Low Carbon Steel. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/77XQ-5M30. https://resolver.caltech.edu/CaltechETD:etd-01232006-153919

Abstract

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. This thesis presents the results of an experimental investigation of the effect of grain size on the yielding behavior of very low-carbon steel. Steel specimens of five grain sizes were produced for testing. The average grain diameter of these specimens ranged from 1.1 x 10(-3) in. to 8.1 x 10(-3) in. Two types of tensile tests were performed, one by the application of very low loading rates and the other by the rapid application of a constant stress. Both types of tests were performed at temperatures of 72°F and -320°F, while a few rapid loading tests were performed at a temperature of -109°F. Both the static upper and lower yield points are observed to increase linearly with [...], where d equals the average grain diameter. Delay time and pre-yield micro strain for specimens that exhibited a yield point were determined from the rapid loading tests conducted at room temperature. Delay time decreases with increasing grain diameter for a given stress. The experimental results are compared with several dislocation models for yielding. These models are shown to be incapable of describing the experimental results of this investigation. A more detailed model, based on Cottrell's yielding mechanism, is described. Plastic deformation by twinning occurred in both static and rapid loading tests performed at a temperature of -320°F. A critical stress for twinning was observed. This stress is independent of stress rate in the range from [...] to [...]. The critical twinning stress increases linearly with [...]. The existence of a critical stress for twinning is shown to be compatible with Cottrell and Bilby's theory for the formation of twin bands.

Thesis Files