Qualitative and quantitative assessment of aerospace structures by pulsed thermography

Abstract

Pulsed thermography (PT) is an NDT&E technique allowing the remote examination of materials and systems. PT is particularly interesting for the inspection of aerospace structures since it can be used to perform safe inspection of large structures in a fast manner and without having to remove the components from the aircraft. Pulsed thermographic data however, is contaminated by noise of many forms. Fortunately, numerous signal processing techniques are available to perform qualitative and quantitative data analysis of data. In this paper, we present three processing techniques that have shown very promising results. We provide the theoretical background and experimental details as well as some representative results that highlight the pros and cons of each technique. As it will be pointed out, an interesting approach is the combination of existing processing techniques in order to use the most attractive features from each technique while reducing the non-desirable characteristics.

Review of pulse phase thermography

“…The following example (from reference [16]) illustrates the usefulness of the combined application of PPT and TSR for an aeronautical sandwich structure. The inspected specimen is shown in Figure 7a, it is a section from a larger a military aircraft that was inspected by pulsed thermography.…”

Comparative evaluation of aerospace composites using thermography and ultrasonic NDT techniques

“…The most common in use active mode, this of Transient Thermography and in particular, this of photothermal pulsed thermography compares favourably to conventional inspection technologies in terms of speed and sensitivity, while offering the advantage of contactless evaluation. Applications range from in-service maintenance of the structure to the process control during the manufacturing stages [5,6]. In the past, the practice of thermography was based almost entirely on the visual assessment of the thermographic images, searching for temperature differences on the surface of the investigated target.…”

A fast lock-in infrared thermography implementation to detect defects in composite structures like wind turbine blades

“…Infrared thermography is an attractive NDT method for testing blades because of its full-field imaging capability. The problem of defect detection using infrared thermography has been studied extensively in the literature [3][4][5][6][7]. The most common implementation is based on Pulsed Thermography which is very well suited for detection of shallow defects.…”