The purpose of this study was to confirm the influence of bleaching on the plastic flow deformation of bulk wood irradiated by the electron-beam (EB). Flat-sawn wood samples of hinoki (Chamaecyparis obtusa) in the oven-dry condition were irradiated by EB at several levels of absorbed dose ranging from 0 to 263 kGy, and subsequently bleached using the mixed aqueous solution of hydrogen peroxide and ammonia. Free compression along radial direction of wood were performed on the treated samples at moist and heated conditions. The obtained strain-stress (s-s) curves indicated that the deformation behavior was affected by the bleaching as well as the EB irradiation. The proportional limit strain, flow starting strain, and maximum strain in the s-s curves indicated that the flow deformation was decreased by the bleaching and was promoted by the EB irradiation, though the elastic deformation and densification deformation were not affected by both treatments. The flow deformation along tangential direction of wood was decreased by the bleaching, while the deformation along fiber direction was promoted by the bleaching. It was shown from the scanning electron microscope (SEM) observation that the deformation along the fiber direction increased with increasing the number and scale of fracture of wood fibers. By the EB irradiation on the sample, the flow deformation became more easily started and was promoted till the end of the deformation. By the bleaching of the sample, the flow deformation became more easily started, however its progression was suppressed.
