Eventos Anais de eventos
COBEM 2023
27th International Congress of Mechanical Engineering
Fatigue life prediction of medium carbon steel with an artificial defect based on small crack growth relations
Submission Author:
Nathalia Santos , DF , Brazil
Co-Authors:
Nathalia Santos, Fábio Castro
Presenter: Nathalia Santos
doi://10.26678/ABCM.COBEM2023.COB2023-0152
Abstract
The influence of defects on the durability of components is important in fatigue design since their presence may reduce fatigue life. Studies have indicated that total fatigue life of a metal with a small defect is mainly occupied by the life required for a crack to propagate up to macroscopic size. Therefore, relations capable to describe small crack growth are useful for estimating the fatigue life. In this work, an experimental evaluation of the Nisitani relation for small fatigue crack growth is performed. Uniaxial fatigue tests were conducted on SAE 1045 steel with an artificial cylindrical hole with diameter and depth of 400 µm. The specimens were subjected to fully reversed tension-compression with stress amplitudes ranging from 250 to 160 MPa, resulting in number of cycles to failure from 10^4 cycles up to the run-out condition (10^7 cycles). Fatigue crack growth was accompanied by periodically interrupting the tests and measuring the crack length with a confocal laser microscope. It was found that half of the fatigue life was spent on small crack growth until the crack reaches 1.5 mm. Also, the results indicated Nisitani relation could provide satisfactory live estimates up to 5×10^5 cycles, but it was not accurate on predicting fatigue lives longer than 10^6 cycles.
Keywords
Fatigue Life, Small Fatigue Crack Growth, Microdefects, SAE 1045 Carbon Steel
