Date of Award
Fall 1973
Document Type
Thesis - Restricted
Degree Name
Master of Science (MS)
Department
Mechanical and Industrial Engineering
First Advisor
Fournelle, R. A.
Second Advisor
Hirthe, Walter M.
Abstract
A low carbon, low alloy steel was subjected to fully reversed axial fatigue loading in both the high and low cycle ranges. Both as-received, and 5% axially prestrained specimens, in tension and compression, were tested. No consistent, significant difference could be established between the fatigue endurance of the prestrained and unprestrained specimens. Monotonic tensile properties were obtained, and incremental step tests were conducted on all three prestrain conditions . Monotonic and cyclic stress-strain curves, strain-life curves, monotonic and cyclic strain hardening exponents, and "stress-amplitude-versus-percent-of-life" curves were determined. High and low cycle loads were then paired in such a manner that at any point during this "superimposed life" test, a specimen would have been exposed to approximately an equal percentage of the total life-to-failure at each of the two loading levels. In all cases it was found that fatigue failure was greatly accelerated over the simple additive prediction on the basis of Minor's Rule. This is our most dramatic finding and is in agreement with work done by Dowling (3). An increase in reversed plastic flow of the "fully elastic" range stress-cycles, following a plastic range "spike", was recorded, and is believed to be responsible for the reduction in life. A slight drop in stress amplitude, as was normally noted around half-life in the constant-strain- controlled, low cycle tests, resulted in near immediate failure of the superimposed life specimens - usually in the very next block of low-stress cycles (see Figure 18). This behavior suggests the presence of another failure-accelerating mechanism. An original gripping fixture and specimen geometry, specifically designed for the high volume study of sheet and plate stock, were employed; and are described and discussed.
Recommended Citation
Ruehl, Phillip C., "The Effect of Prestrain and Periodic Low Cycle Fatigue 'spikes' on the Normal Cyclic Behavior of a Low Alloy Steel" (1973). Master's Theses (1922-2009) Access restricted to Marquette Campus. 4050.
https://epublications.marquette.edu/theses/4050