Novel developments of Moiré techniques for industrial applications
The family of moire and fringe projection techniques can be used to measure the shape, orientation and deformation of arbitrary objects. These experimental techniques are easy to automate, allow remote operation, provide full-field information and are versatile, inexpensive and relatively simple. They have been applied extensively in the past, but mostly in the controlled environment of a laboratory. There is great potential in the use of these techniques for a variety of industrial applications including quality control and process monitoring. However, this implies dealing with the adverse conditions of the factory, hangar or similar environment. In addition, these techniques will only appeal to industry if they are fast, simple, and foolproof. The main goal of this research was to exploit recent technological advances to fulfil the requirements of industry, making these techniques easier to use and more robust, and explore the potential offered by the combination and cross-fertilization of moire methods with techniques from different fields such as experimental stress analysis, non-destructive evaluation, and machine vision. This research resulted in the development of a number of instruments and procedures for industrial applications based in moire and fringe projection techniques, including: • A handheld instrument based in the shadow moire technique designed to assist in the detection of very small surface defects in aircraft parts, during in-service maintenance inspections; • A multi-purpose system to measure remotely (i) the shape and deformation of three dimensional objects by means of the fringe projection technique, and (ii) the location of the object by means of triangulation. The elements were integrated in a portable instrument, and fully automated novel algorithms were implemented to process the data; • Finally, a novel experimental technique is proposed that uses thermal marking to measure deformation in a component, in a combination of concepts from moire and thermography. Experimental results obtained in a range of situations are presented in several industrial applications in the context of the aerospace industry and in bioengineering.