A METHOD OF MEASURING VISCOELASTIC PROPER TIES OF WOOD UNDER HIGH-TEMPERATURE AND HIGH-PRESSURE STEAM CONDITIONS

A method of measuring the viscoelastic properties of wood under high-t emperature and high-pressure steam conditions was developed. An autocl ave built-in testing machine was used for the measurements. In the ins ide of the autoclave a newly developed load cell capable of resisting a steam pressure of 16 kg/cm(2) and a temperature of 200 degrees C was installed. We observed that this load cell could be used for detectin g loads precisely under steaming at temperatures from 100 to 200 degre es C. In addition to load-detecting problems, we need to avoid the non -uniform thermal degradation of wood in the measuring process under st eaming at high temperatures. This non-uniform degradation can be minim ized by minimizing the time required for wood attaining a thermal equi librium state through specimens in the FSP (fiber saturation point) st ale. According to this method, a stress relaxation curve for sugi (Cry ptomeria japonica D. Don) wood in compression under steaming at 180 de grees C was obtained. The stress was seen to decrease rapidly with tim e, reaching almost 0 at 3000 sec.