Predicting the Strength of Norway Spruce by Microwave Scanning: A Comparison with Other Scanning Techniques

Nils Lundgren, Mattias Brännström, Olle Hagman, Johan Oja


In this study, 90 boards of Norway spruce (Picea abies (L.) Karst.) sized 48 x 148 mm in cross-section, have been examined using different scanning and measurement techniques. All of the boards originated from a sawmill located in southern Finland. Planar X-ray scanning, microwave scanning, and grain-angle measurement have been performed. In addition, strength and elastic properties were assessed for each piece by four point bending. The purpose of the study was to relate the potential of microwave scanning compared to other, industrially available techniques and to explain the physiological background of the microwave responses. The results show that the microwave signal, after transmission through wood, contains information about the bending strength and the modulus of elasticity. The correlation to density is a key factor. Annual ring width was also found to be correlated both to microwave measurements and strength properties.


Wood;spruce;grading;microwave;x-ray;scanning;modulus of elasticity (MOE);modulus of rupture (MOR)

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