PREDICTING STRESS-STRAIN BEHAVIOUR OF WHITE SPRUCE IN RADIAL COMPRESSION AT DIFFERENT TEMPERATURES

摘要

White spruce specimens were subjected to radial compressive load at different temperatures under microscope and empirical models were obtained to explain effect of temperature on cell wall modulus and cell wall yield point. These empirical models were then incorporated into mechanical models to predict gross elastic part and yield point of stress-strain response of softwoods behaviour at different temperatures. Plateau part of stress-strain curve was predicted by compression factor which is a function of cell lumen removal of earlywood cells. Since at the end of compression test latewood cells remain in elastic deformation, the mechanical models were applied to these cells to predict the last upward of stress-strain curve. By this approach the whole stress-strain curves of white spruce at different temperatures were predicted. Predicted stress-strain curves were compared with experimental curves. Results approved that above approach is a good tool to predict radial compression stress-strain curve of softwoods at different temperatures.