Abstract:

The research on drying stresses is an important part of wood science, which is capable of guiding wood processing as well as providing an important basis for establishing and optimizing drying schedule. This study systematically and comprehensively summarized the research status of wood drying stresses from experimental research and numerical analysis, and discussed the merits and demerits for each method. It aimed to provide some valuable information for the further research on wood drying stresses, and to promote the correlational studies to a higher and deeper level as well as lay a foundation for the high quality drying of wood. In experimental research, the prong and slice method in traditional are still the commonly used method for testing wood drying stresses. The modern technologies, such as digital image correlation technology and near infrared spectroscopy, provide new opportunities to the research of wood drying stresses. However, so far there is still no a test method to wood drying stresses with high precision and good popular conditions. In terms of numerical analysis, the models of drying stresses based on wood rheological theory have become more robust, and reached a plateau. With the development of computer technology and numerical analysis software, the finite element method has been used to simulate wood drying stresses, which had some advantages in dealing with the anisotropic materials, and it is in rapidly developing stage now. Based on the current research, the experimental research and numerical analysis play irreplaceable roles in the investigation of wood drying stresses. The combination of the two is the key to comprehensively evaluating drying stresses. The exploration of new devices or technologies, which can rapidly, accurately and continuously detect wood drying stresses, is still the focus in the future research. The finite element method is the most potential numerical analysis method for wood drying stresses. The model with wide applicability should consider the multi-scale and multi-layer characteristics of wood, and also obtain accurate model parameters by the use of advanced instrument and equipment. Furthermore, the proposed model should be put into the control system of drying equipment, and providing the guidance and service to actual production.

Key words: wood drying, drying stresses, test method, model prediction