SYMPOSIA PAPER Published: 01 January 1970
STP26849S

The Role of Residual Stresses in Increasing Long-life Fatigue Strength of Notched Machine Members

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High compressive residual stress and high hardness were utilized to obtain high fatigue strength in nonrotating bending. A compressive residual stress of 250 ksi, obtained in a 0.25-in. notch in SAE 1045 specimens of 1.50-in. diameter, resulted in a one million-cycle fatigue strength of ±230 ksi. An investigation showed that, over the range studied, maximum residual stress from heat treatment was produced with maximum hardness, medium carbon content, maximum section size (to 4-in. diameter), and minimum hardenability. At high hardness, cold working by shot peening was found to decrease the high residual stress from heat treatment. Fatigue tests were run on peened and unpeened specimens of various hardnesses with a machine that had provisions for applying a mechanical mean stress. Various net mean stress conditions, residual plus mechanical, could then be obtained. The fatigue strength of hard specimens with a tensile, applied mean stress was reduced by the presence of crack-like defects created by peening. Data were interpreted in terms of a theory in the literature involving crack initiation, crack propagation, and yielding.

Author Information

Nelson, DV
Caterpillar Tractor Co., Peoria, Ill.
Ricklefs, RE
Caterpillar Tractor Co., Peoria, Ill.
Evans, WP
Caterpillar Tractor Co., Peoria, Ill.
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Details
Developed by Committee: E08
Pages: 228–251
DOI: 10.1520/STP26849S
ISBN-EB: 978-0-8031-4587-0
ISBN-13: 978-0-8031-0030-5