Eventos Anais de eventos
COBEM 2019
25th International Congress of Mechanical Engineering
EFFECT OF LOAD RATIO ON FATIGUE CRACK GROWTH IN THE NEAR-THRESHOLD REGIME IN STEELS FOR AUTOMOTIVE APPLICATIONS USING A COMBINED CRACK CLOSURE AND DRIVING FORCE APPROACH
Submission Author:
Leonardo Godefroid , MG
Co-Authors:
Tainan Muniz, Leonardo Godefroid, Jefferson José Vilela, Fabiano Machado
Presenter: Leonardo Godefroid
doi://10.26678/ABCM.COBEM2019.COB2019-0077
Abstract
This research consisted in the evaluation of the effect of load ratio, R, on fatigue crack growth in one HSLA steel and three different AHSS steels, all materials for automotive applications. The objective of the work was to combine fatigue crack growth results for several R values in a single model that can predict the material behavior in the near threshold ΔKth region. For this, the methodology proposed recently by Zhu, Xuan and Tu (2013, 2015) was used to combine two approaches currently adopted in this context: by crack closure and two-parameters driving force. The microstructure of the steels was characterized by optical microscopy and scanning electron microscopy. Basic mechanical tensile and hardness tests were performed. C(T) test specimens with 3mm thick were used for the fatigue tests at room temperature and at a frequency of 35Hz, with a load ratio of 0.03, 0.1, 0.4, 0.5 and 0.7. The traditional effect of fatigue strength loss with increasing load ratio was verified. The application of the mentioned model was validated, from the comparison between the values for the experimental and predicted threshold ΔKth, showing the reasonableness of the methodology developed.
Keywords
fatigue crack growth, Load ratio, Crack closure, Driving force parameters, Steels for automotive industry
