Image-based industrial non-destructive testing techniques are commonly used for assessing material integrity. The cameras used for these tasks have lenses that can present form deviations, promoting anomaly creation on the acquired images. This problem also affects infrared cameras, but very often nothing is done to correct it, usually due to the cost of calibration tools for infrared wavelength. This paper describes then a manufacturing process based on the ablation of copper material with a pulsed laser of a cost-effective, infrared-reflective chessboard pattern for calibrating infrared cameras. Measurements of artificial defects in carbon fiber reinforced plastic plates with active lock-in thermography were performed and a comparison between the results with and without the corrections given by the calibration was done. The metrological benefits of applying the proposed calibration procedure have been evidenced by the reduction of the measurement bias and repeatability, which is important especially considering industrial non-destructive testing evaluations.
Moisture-harvesting lizards, such as the Texas horned lizard Phrynosoma cornutum, have remarkable adaptations for inhabiting arid regions. Special skin structures, in particular capillary channels in between imbricate overlapping scales, enable the lizard to collect water by capillarity and to transport it to the snout for ingestion. This fluid transport is passive and directional towards the lizard's snout. The directionality is based on geometric principles, namely on a periodic pattern of interconnected half-open capillary channels that narrow and widen. Following a biomimetic approach, these principles were transferred to technical prototype design and manufacturing. Capillary structures, 50 μm to 300 μm wide and approx. 70 μm deep, were realized by use of a pulsed picosecond laser in hot working tool steel, hardened to 52 HRC. In order to achieve highest functionality, strategies were developed to minimize potential structural inaccuracies, which can occur at the bottom of the capillary structures caused by the laser process. Such inaccuracies are in the range of 10 μm to 15 μm and form sub-capillary structures with greater capillary forces than the main channels. Hence, an Acceleration Compensation Algorithm was developed for the laser process to minimize or even avoid these inaccuracies. The capillary design was also identified to have substantial influence; by a hexagonal capillary network of non-parallel capillaries potential influences of sub-capillaries on the functionality were reduced to realize a robust passive directional capillary transport. Such smart surface structures can lead to improvements of technical systems by decreasing energy consumption and increasing the resource efficiency.
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