SYMPOSIA PAPER Published: 01 January 2007
STP45509S

Fatigue Strength in Presence of Inhomogeneities: Influence of Constraint

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The effect of defects on the entity of the fatigue limit is nowadays well known and is demonstrated to be equivalent to the nonpropagating condition of short cracks. The influence of constraint at the defect tip has been addressed in the present paper considering a mild steel whose mechanical behavior has been experimentally determined together with the propagation threshold values for long cracks. The activity has first dealt with the determination of the Kitagawa diagram by means of fatigue limit tests using specimens containing micro-notches with different shapes (drilled holes and narrow slits). Experimental results showed a significant influence of the defect shape on the fatigue limit and thresholds. In order to understand the reasons, defects have then been analyzed by elasto-plastic FEM analyses. Computational results have confirmed a significant difference in the global constraint factor at the crack tip between round and narrow defects.

Author Information

Beretta, Stefano
Politecnico di Milano, Milano, Italy
Carboni, Michele
Politecnico di Milano, Milano, Italy
Madia, Mauro
Politecnico di Milano, Milano, Italy
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Details
Developed by Committee: E08
Pages: 137–147
DOI: 10.1520/STP45509S
ISBN-EB: 978-0-8031-6247-1
ISBN-13: 978-0-8031-3406-5