Banca de DEFESA: Nathalia Manes Santos

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : Nathalia Manes Santos
DATE: 14/12/2023
TIME: 09:00
LOCAL: Microsoft TEAMS
TITLE:

Fatigue life of 1045 steel with an artificial small defect: Experiments and modeling based on small crack growth

KEY WORDS:

fatigue life, small defect, 1045 steel, small crack growth

PAGES: 41
BIG AREA: Engenharias
AREA: Engenharia Mecânica
SUMMARY:

A large portion of the fatigue life of materials consists in the growth of small cracks. Despite the progress in the understanding of small fatigue crack growth over the last 50 years, it remains a fundamental and active research topic. In this context, the aims of the present work were twofold: (i) to experimentally characterize the small crack growth of 1045 carbon steel with a small surface defect when subjected to cyclic loading and (ii) to assess the accuracy of small crack growth models in predicting fatigue life. Cylindrical specimens with an artificial cylindrical hole (diameter and depth of 400 µm) were subjected to cyclic axial loading under load ratios of -1 and 0.1. The tests were conducted in the high-cycle fatigue regime, with lives ranging from 10^4 to 10^7 cycles. Crack growth in the vicinity of the hole was monitored by periodically interrupting the tests and measuring the crack length using a confocal laser microscope. The incremental polynomial method was then used to obtain the crack growth rate vs. crack length. A modified form of the Fatemi model for small crack growth rate was developed by substituting the Smith–Watson–Topper parameter for a Walker-type parameter. The constants of the model were determined by fitting the small crack growth data obtained under uniaxial loading. To verify the accuracy of fatigue life predictions under multiaxial loading, axial/torsional test data previously produced by the Fatigue, Fracture, and Materials research group of the University of Brasília were used. The data included in-phase and out-of-phase loading conditions and the presence of mean stress. It was demonstrated that the use of the Walker-type parameter yielded improved life estimates, especially for the tests involving mean stress. Most of the fatigue life estimates were within a factor of 3 with respect to the measured lives. 

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