Impact elastic and plastic bending of beam with open cross section
Maekawa Ichiro; Uda Kazufumi
Abstract:This paper describes a work which is a part of systematic study for understanding the mechanism of particle board dimensional stabilization by steam pretreatment. Particular interest was centered on an in plane swelling stress of wood particles which causes the breakage of adhesive bond between particles. The effects of steam temperature on the following factors were investigated by the use of uncompressed wood blocks: swelling stress by water absorption, hygroscopic swelling, and Young's modulus in the tangential direction. The swelling stress was found to decrease with increasing steam temperature and became one fifth of the control when steamed at 220 deg. for 10 minutes. The hygroscopic swelling, the maximum swelling, and the Young's modulus also showed a trend of decreasing with increasing steam temperature. Therefore, the elastic model which describes swelling stresses by elastic strain and Young's moduli was applied. The calculated change of swelling stress by steaming was found to agree well with the observed one, which suggests that the decrease of swelling stress can be derived from the synergistic effect of decrease in both swelling and elasticity. Key Words:particleboard, steam pretreatment, swelling stress, hygroscopicity, hygroscopic swelling