KINK BAND INITIATION AND BAND BROADENING IN CLEAR WOOD UNDER COMPRESSIVE LOADING

Compression kinking failure in spruce (Picea Abies) is investigated ex perimentally using a high resolution video camera. Three distinct stag es of kinking are identified; incipient kinking, transient kinking and steady-state kinking. The different mechanisms governing these stages are discussed. Incipient kinking is found to be governed by the longi tudinal shear yield strength and the high local fiber misalignments in trinsic in the microstructure of wood. Steady-state kinking takes plac e under constant applied stress and continues even for very large defo rmations.