A numerical and experimental study of stress and crack development in kiln-dried wood

Numerical and experimental investigations were carried out on well defined log-disc samples of Norway spruce consisting of both heartwood and sapwood, with the aim of gaining more adequate knowledge of stress and fracture generation during the drying process. Use of thin discs of a log enabled a well-controlled and simplified drying history of the samples to be obtained.

Experiments supported by the numerical simulations showed the heartwood to dry below the fibre saturation point (FSP), much earlier than the sapwood, and thus to start shrinking at a much earlier stage. The variation in the moisture histories for different parts of a cross section was the main reason for the stress development during the drying process.