Progress in phase angle thermography

Abstract

Phase angle thermography is basically spatially multiplexed photothermal radiometry. It provides images for remote detection and imaging of damage. For energy deposition one can use external heat sources ͑e.g., light or convective heating͒ or internal heat generation ͑e.g., electric current, microwaves, eddy current, or elastic wave͒. More complete information about defects is obtained by combining information from external and internal heating methods: Effects of intact thermal structure can be distinguished from defect specific thermal signatures. Our recent results relate to multifrequency excitation allowing for depth profiling from one lock-in-thermography measurement and, additionally, to modulated ultrasound frequency burst phase angle thermography where effects of standing elastic waves are eliminated. This way the applications for nondestructive evaluation become more reliable and faster.

Modelling of the frequency modulated thermal wave imaging process through the finite element method for non-destructive testing of a mild steel sample

“…Passive thermography relies on the naturally existing temperature difference over the object, while active thermography involves an external heat stimulus to obtain a significant contrast [1] . In most cases, the applied thermal excitation is either in a pulsed form (pulse thermography (PT) and pulsed phase thermography (PPT)) or a mono-frequency sinusoidal modulated form (lock-in thermography(LT)) [2][3][4][5][6][7][8][9][10][11] .…”

Infrared Thermal Wave Imaging for Nondestructive Testing of Fibre Reinforced Polymers

“…Of various active thermographic methods , Pulse Thermography (PT) [3] and continuous wave Lock-in Thermography (LT) [8][9][10][11][12] are widely used. In PT, a shortduration high peak power stimulus is applied over test object and the captured temporal temperature response is used to reveal the details of the hidden defects (time period of stimulus vary from few milliseconds for high conductive materials to a few seconds for low conductive materials).…”

Effect of modulation frequency on detecting defects of metal plates using infrared lock-in thermography

“…It could avoid burn of structure surface. Optical Lock-in Thermography (OLT) is infrared lock-in thermography, in which excitation sources is periodic modulated lamp [4][5] . Optical Lock-in Thermography is being used as a powerful tool for remote non-contact detection of defects 6 .…”