This paper presents the failure analysis of two joining bolt from a Komatsu excavator revolving frame that has undergone facture by fatigue. The bolt ´s material corresponds to a quenched and tempered 41xx steel series. The bolts we subjected to tensile and compressive loads at a rate of 82 cycles per hour for about 9500 hours before failure. The excavator bucket was exchanged to increase its loading bucket volumetric capacity from 1,6 to 2,1 m 3 in order to remove a higher amount of mineral. This decision made the revolving frame to experience a larger cyclic momentum that increased the stress amplitude over the bolts making them more likely to fail by crack growth. Numerical analysis done using ANSYS 11 and Beasy v10.r12 supported the assumed fatigue failure hypothesis.
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