Eventos Anais de eventos
COBEM 2019
25th International Congress of Mechanical Engineering
EFFECT OF MICROALLOYING ON FATIGUE INITIATION AND CRACK GROWTH RESISTANCE OF A RAILROAD STEEL
Submission Author:
Leonardo Godefroid , MG
Co-Authors:
Andrew Souza, Luiza Pessoa Moreira, Leonardo Godefroid, Rodrigo Porcaro, Geraldo Lúcio de Faria
Presenter: Leonardo Godefroid
doi://10.26678/ABCM.COBEM2019.COB2019-0076
Abstract
This research characterized the microstructure and evaluated the mechanical behavior of two pearlitic steels used in Brazilian railroads, a C-Mn-Si steel and a Nb-V-microalloyed steel. The microstructures were observed by light optical, scanning electron and atomic force microscopy. Prior austenite grain size, pearlite colony size and pearlite interlamelar spacing were measured. The mechanical behavior was evaluated by tensile tests, hardness tests, fracture toughness tests (linear elastic fracture mechanics - KIC), and fatigue resistance tests: crack initiation tests (σa x Nf) and crack growth tests (da/dN x ΔK). The fatigue tests were performed with a load ratio R=0.1, at room temperature and frequency of 30Hz. The fracture surfaces of all tested specimens were analyzed by scanning electron. The presence of niobium and vanadium provided a more refined microstructure for the microalloying steel. However, hardness, yield and tensile strength, and fracture toughness were similar for both steels. The main difference in the mechanical behavior was verified in the fatigue crack growth tests: the fatigue resistance was higher for the microalloyed steel. These fatigue results are important to predict the actual behavior of steels used in the railway sector, to perform a proper maintenance control avoiding a premature failure and a consequent catastrophic accident, and to select the adequate material for this application.
Keywords
Fatigue crack tests, Microalloying, Railroad steel
