The impact excitation resonance technique is a commonly used method for assessing the stiffness of materials by measurement of vibrational frequencies. It has proved to be a fast and reliable approach for machine strength grading of new structural timber in Europe and beyond (see [1] table 6). It also has significant potential for use in the strength grading of recovered wood, but there are several additional factors to consider, which can require the use of more sophisticated analysis than is typically used. These factors include the relatively short lengths, uneven ends, and the possible presence of mechanical damage within the timber length (both visible and hidden). This paper describes an approach that can be used to give more confidence in the stiffness assessment without needing sophisticated or expensive equipment.
Keywords: NDT, grading, assessment, acoustic, recycled, reuse, circular economy
Authors
Daniel Ridley-Ellis
Edinburgh Napier University, United Kingdom
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