Distribution of Wood Residual Strain Around Holes Due to Drilling

Drilling-induced residual strain of timber member around fastener holes (such as bolts) often leads to deterioration of mechanical properties. In this paper, the effects of diameter of holes (14, 18 and 22 mm), drilling speed (95 and 190 r/min) and wood species (Spruce, Spruce-Pine-Fir and Douglas Fir) on the residual strain of wood specimens were evaluated. The dimensions of the specimens were determined according to Standard Test Method for Evaluating Dowel-Bearing Strength of Wood and Wood-Based Products (ASTM D5764). Based on an open source 2D digital image correlation (DIC) MATLAB program, Ncorr, the drilled-induced residual strain around the hole was assessed by comparing the wood deformation for specimen before and after drilling. The results indicated that with the same drilling speed, the residual strain distribution of specimens did not vary remarkably with different hole diameters. The maximum residual compressive strain increased with increase of drilling speed, while it did not vary significantly with the hole diameter or wood species. The research provides theoretical guidance for improving the elastic—plastic analysis of mechanical behaviour of bolted timber connections.