Eventos Anais de eventos
COBEM 2017
24th ABCM International Congress of Mechanical Engineering
Crack initiation test in bending fatigue: detecting by the loss of gas-tightness
Submission Author:
José Felipe Dias , MG , Brazil
Co-Authors:
Tomás Londe Camargos, Ewerton Augusto Sousa Nogueira, Denilson Carmo, Gabriel Ribeiro, Ana Maria Figueiredo, José Felipe Dias
Presenter: José Felipe Dias
doi://10.26678/ABCM.COBEM2017.COB17-0680
Abstract
The fatigue crack initiation method is investigated in a specimen with a cavity under positive or negative pressure. The test is stopped automatically when a fatigue crack causes the loss of tightness of the cavity. A bending fatigue testing machine has been developed and adapted to test specimen with a pressurized cavity or under vacuum. Fatigue tests were performed under constant strain amplitude on test specimens made of SAE 1045 steel with a pressurized cavity of inert gas and a wall thickness of 1 mm. In order to verify if the investigated method would be able to detect the influence of surface finishing on the initiation of fatigue crack, machined and drawn specimens were used. In the analysis of the experimental results the Coffin-Manson curve and the SWT models were used. The curve parameters ε-N according to Baumel-Seeger, Roessle-Fatemi and Castro-Meggiolaro were applied. The test results showed consistent with the predictions of the models used, indicating that the method of crack detection by the loss of tightness is effective and technically viable and capable of detecting the influence of the surface finish in the fatigue crack initiation resistance. The tests demonstrated that the sensitivity of the method is related to the used type of pressure sensor and differential pressure specified for the shutdown of the machine after the loss of gas-tightness.
Keywords
fatigue, fatigue crack initiation, crack detection method, bending test apparatus, strain control
