Fatigue crack initiation and growth in a 35CrMo4 steel investigated by infrared thermography

Abstract

A B S T R A C TThe present work is devoted to the investigation of fatigue crack initiation and growth in middle-cycle fatigue (∼10 5 cycles). Smooth specimens made of 35CrMo4 quenched and tempered steel were loaded in fully reversed plane bending. Temperature field evolution in time was recorded with an infrared camera. The experimental results show that the local heating of metal under fatigue loading is a sensitive and accurate enough manifestation of small fatigue crack initiation. It is shown that the time evolution of the spatial standard deviation of the temperature field can be used to investigate the damage localization and to monitor both the crack initiation and the current location of the fatigue crack tip. This should help to investigate the behaviour of defect during cyclic loading.

Investigation of mechanical properties of Armco-iron during fatigue test

“…It should be noted that the armco-iron specimens under tensile loading demonstrate abnormal deformation behavior. According to literature (Plekhov et al 2005), a decrease in the resonant frequency during the fatigue test on ultrasound machine is an irreversible process and corresponds to the emergence of a subsurface fatigue crack. In the case of armco-iron, the decay of the resonance frequency did not imply mechanical (macroscopic) destruction of the specimen after stopping the testing machine.…”

“…The experimental study of fatigue properties of the material on such a cyclic basis involves significant time costs. Nowadays, with the advent of ultrasonic testing machines the researchers can operate with the real-time data and measurements (Bathias & Gigacycle 2004;Botvina 2004;Plekhov et al 2005;Shaniavski & Skvortsov 1999;Zhu et al 2006).…”

Monitoring of glass-ceramic composites under static and dynamic loading by combined NDE methods

“…Among many other successful applications, it has been used for the measurement of crack length [12] and for the determination of crack growth rate [9,10,13] in compact tension specimens. In addition, it has been employed for detection of cracks due to local temperature increment, determination of crack initiation and prediction of crack propagation [14].…”

Theoretical and experimental study of energy storage process in metals under plastic deformation

“…Taylor [7] gives good results in mechanical calculations mainly at high strain rates [9]. At slow strain rates and in some particular cases such as, for instance, an application of infrared thermography for damage monitoring [10,11] we need a adequate physical model of energy balance in a material.…”

“…Recently a lot of experimental works discover interesting thermomechanical phenomena such as: thermal front propagation under quasi-static loading [12], Joule-Thomson effect in thermoelasticity [13], high temperature frequency generation under sinusoidal fatigue loading [11,14] in solids and shows a lack in adequate theoretical models.…”