Problem be used for evaluating products quality: - Destructive evaluation, in which the product is destroyed in order to analyse its properties and internal structure; - Non destructive evaluation (NDE), used for identifying defect and irregularities, without damaging the product. These non destructive evaluation methods include [1-4]: ‐ Visual and optical testing – VT; ‐ Magnetic particle testing – MT; ‐ Liquid penetrant testing –PT; ‐ Radiographic testing – RT ; ‐ Ultrasounds testing – UT; ‐ Eddy current testing – ET; One of the most frequently used method of non destructive examination is PT or dye penetrant testing (DPT), due to the low costs involved, ease of use and flexibility, suitability to a large number of applications. This method evaluates the presence of open discontinuities (or cracks) on the surface part, based on reverse capillary action and on the developer absorption effect which draw out penetrant and produces indications visible for the inspector (see fig.1 for a principle scheme of LP examination [5]). Although widely used, PT has several disadvantages: - Limitation to surface defects or to the defects which communicates with the surface; - Only products with non porous surfaces (or with low porosity) can be inspected; - Important amount of time used for manipulating the parts during inspection; - Results interpretation heavily depends on subjective aspects such as operator experience, knowledge and motivation. In order to eliminate or reduce the operator involvement in the process steps, research has being made for automating the process, such examples of liquid penetrant inspection lines can be found in [10-15]. However, in all analysed automated PT systems, the inspection is still made visually by an inspector, who gives a pass/fail grade for the inspected parts. The difficulty of fully automating the liquid penetrant inspection process is due not only to the necessity to precisely determine and control process parameters (dwell time, developer time, drying time, quantity of penetrant, developer and cleaning water, pressure for spraying solutions with penetrant, developer and cleaning water, transport speed, etc.) but also to the evaluation and results interpretation process. Thus, even if there are patents [16-17] which present approaches and general frameworks for fully-automated LPT systems, including also automatic image processing of the flaws, to the best of the authors’ knowledge, these equipment are not yet implemented. In this context, this paper presents an experimental stand for a fully automated liquid penetrant inspection line, which includes the development and use of dedicated imaging software used for real time interpretation of the images acquired using a digital camera. The novelty of the research consist in designing and building a fully-automated LPT stand, controlled by a soft which contains also a module for acquisition and image processing in real time without no human implication.
Leveraging object-orientation for real-time imaging systems
