Infrared thermography in materials inspection and thermo-fluid dynamics

Abstract

Infrared thermography is becoming ever more popular and is being used in an ever-increasing number of applications mainly due to its accuracy as well as non-contact and two-dimensional characters. In particular, the thermal signatures, which are visualized over a body surface through the use of a remote infrared imaging device, may be exploited to gain information in both the body and the fl uid surrounding it. In fact, thermal images may contain either information about the body’s material conditions at a given instant (e.g. material integrity or presence of defects), or its behaviour under mechanical load (e.g. during bending or impact) or about the ability of the fl uid fl ow passing over the body surface to convey heat (i.e. cooling or heating it). Of course, what is important is the choice of the technique and of the procedure used in taking thermographic images, as well of the computational method applied in reducing data for a correct representation and interpretation of the thermal phenomena under study. The specifi c intention of this work is to highlight the usefulness of infrared thermography within two main tasks of materials inspection and thermo-fl uid dynamics. With regard to the fi rst one, the different thermographic techniques, which can be used for non-destructive testing, are described with the data processing procedures; then some key examples, mainly involving composite materials, are reported and discussed. The second topic is illustrated through different fl ow confi gurations, such as impinging jets, which are encountered in the industrial context for heating or cooling purposes, a free stream fl owing over a body to assess separation and/or reattachment location and a disk rotating in still air. However, a part is spent in the description of theoretical approaches and standard procedures for acquisition of thermographic images, as well of methods for data reduction and computation of the required quantities.