Abstract
The surface strain of wood with a bolt hole under compressive loads was measured using a three-dimensional digital image correlation (3D-DIC) technique. Square bars with a 20 mm x 20 mm cross section sawn in the radical section of Japanese cedar were used as compressive specimens in the longitudinal and transversal directions. The measured surfaces of the specimens with a straight, flat and end grains were sprayed with white paint and speckled with black paint on the white paint. Images of the specimen surface during loading were captured at a constant time interval using two CCD cameras, and the strain on the specimen surface was calculated from the images using a 3D-DIC software. Results revealed that large strains were generated at several positions around the bolt hole before the initiation of cracks, cracks propagated from the positions, and finally the specimens fractured. This indicated that the initiation of the fracture of wood with a bolt hole can be probably predicted by measuring the strain around the hole.
