Development of a Self-reference Lock-in Thermography for Remote Nondestructive Testing of Fatigue Crack (1st Report, Fundamental Study Using Welded Steel Samples)

Gigacycle fatigue behaviour of austenitic stainless steels used for mercury target vessels

“…This temperature rise is also reported for carbon steel and aluminium alloys, and it is suggested that the plastic deformation around the crack tip contributes to the temperature rise [24,25]. It is proposed that the detection of the macro fatigue crack initiation of the structural material by measuring the temperature distribution could be done using thermography [26], and it is also proposed that the evaluation of the dissipated energy by measuring the temperature distribution could be used for estimating the fatigue limit [27]. Furthermore, these methods were performed under the conditions of conventional fatigues (~10 Hz), and seems to be applicable for our case regardless of strain rate.…”

Detection of Through-Deck Type Fatigue Cracks in Steel Bridges by Self-Reference Lock-in Thermography

“…The self-reference lock-in thermography [3], developed by the present authors, enabled us to measure the distribution of relative intensity of applied stress under random loading without using any external load signal. In the self-reference lock-in thermography, a reference signal was 38011-p.2 14th International Conference on Experimental Mechanics constructed from the reference region arbitrarily set on the same sequential infrared images on thermoelastic temperature change.…”

“…Thus fatigue cracks can be detected from localized high thermoelastic temperature change observed at crack tips due to stress singularity. The present authors developed a self-reference lock-in thermography [3], which does not require any external reference signals and can be employed even under random loading. Nondestructive inspections of fatigue cracks in steel bridges were conducted by the proposed selfreference lock-in thermography in the previous paper [4].…”

Accuracy improvement of self-reference lock-in thermography method and its application to detection of fatigue cracks in steel bridges

“…The self-reference lock-in thermography [1], developed by the present authors, enabled us to measure the distribution of relative intensity of applied stress under random loading without using any external load signal. In the self-reference lock-in thermography, a reference signal was constructed from the reference region arbitrarily set on the same sequential infrared images on thermoelastic temperature change.…”

“…Fatigue cracks can be identified and evaluated from localized thermoelastic temperature change at crack tips under variable wheel loading by the traffics on the bridge. For measuring small temperature change, selfreference lock-in data processing technique was developed for the improvement of signal/noise ratio in the crack detection process [1]. Detection of the cracks in steel deck was conducted by the self-reference lock-in thermography in the previous paper [2].…”