Estudo do comportamento à fadiga de metais dentro e fora da água na presença de pressão hidrostática

Abstract

The fatigue is the most common form of structural failure and, throughout time, it has been a challenging problem due to the imposed solicitations and the kind of load applied. In this work, the fatigue study effects of the SAE A-36 steel were studied in three different environments: cooled, water layer and inside the water in the presence of hydrostatic pressure with 5 atm. For this, a rotating bending fatigue machine directed for specific conditions was developed and built with the purpose of being tested in distinct environments, simulating the work conditions of steel.This is important, therefore there is no confirmation of the resistance to the underwater fatigue. The underwater fatigue tests are normally carried out in contact with air and not water. The S-N curves were obtained with the results of the fatigue tests. With this data, the S-N-P curves were made with a fault probability of 1%, 50% e 99% to verify the limit of resistance to the fatigue for the environments. The regression model was the methodology used for the data of the accelerated life tests. To evaluate the cumulative damage, some known literature models were used. Following this idea, a method of foreseeing the life span of the materials submitted to the fatigue was proposed, considering the numbers of cycles and the cumulative damage in each applied stress.To complement this study the macrohardness, microhardness and SEM analysis were carried out.