TY - CONF A1 - Vössing, Konrad A1 - Gaal, Mate A1 - Niederleithinger, Ernst A2 - Ross, R. A2 - Sauter, U. T1 - Contactless testing of wood-based materials with novel air-coupled ultrasonic transducers T2 - 21. International Nondestructive Testing and evaluation of Wood Symposium N2 - The detection of delamination, rot and cracks causing a decrease of strength in wooden construction elements is a key task for nondestructive testing (NDT). Air-coupled ultrasound (ACU) is used to detect flaws without having to provide contact to the surface or otherwise affect the object. Novel ferroelectric transducers with a high signal-to-noise ratio enable an accurate flaw detection. Transducers made of cellular polypropylene (PP) are suitable for characterizing wood-based materials (WBM) because their extremely low Young’s modulus and low density mean a favorable acoustic impedance for the transmission of ultrasonic waves between the transducer and air. The transducers can be applied during the production of WBM and during its service life. The device enables a fast in-situ recognition of defects with frequencies between 90 kHz and 250 kHz. Measurements can be performed in through transmission for a high resolution or in pulse-echo technique in case of one-sided access at the expense of reduced signal strength. Ultrasonic quality assurance for wood is an important attempt to increase the acceptance of wooden structures and towards sustainability in civil engineering in general. PB - FVA CY - Freiburg T2 - 21. International Nondestructive Testing and evaluation of Wood Symposium CY - Freiburg, Germany DA - 24.09.2019 KW - Air-coupled ultrasound KW - Defect detection KW - Nondestructive Testing KW - Timber PY - 2019 UR - https://opus4.kobv.de/opus4-bam/frontdoor/index/index/docId/49169 AN - OPUS4-49169 SP - 100 AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany