权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Studies on Mechanism of Creep of Wood under Changing Moisture Content Conditions and Methods for Reducing its Creep

改变含水率条件下木材蠕变机理及减少蠕变方法的研究

基本信息

批准号：
02660168
负责人：
FUSHITANI Masami
金额：
$ 1.28万
依托单位：
Tokyo University of Agriculture and Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1991
项目状态：
已结题

项目摘要

1. We investigated the stress dependence of bending creep of wood under changing moisture content conditions and the acoustic emission(AE)generated during its creep process. In the exponential regression equation between the change in moisture content and the creep strain, the fitted values of exponent increased with increasing stress level under moisture-regain condition, whereas they are somewhat more than 1 and independent of stress level under moisture-loss condition. AEs generally were generated beyond the stress level within which creep strain was proportional to the applied stress. Under air-dry and moisture-regain conditions, AEs were generated above a stress level of 50 while under high moisture content and moisture-loss conditions, they were done above a stress level of 35 %. When creeprupture occurred, many AEs were generated immediately or for a short time before specimen was-ruptured.2. We investigated the reducing effect of acetylating treatment on the bending creep of laminated wood under changing moisture content conditions in connection with the layers composed of acetylated laminae. The creep of laminated wood with acetylated laminae in compression side and tension side layers was smaller than that of laminated wood composed only of untreated laminae under moisture-regain and moisture-loss conditions. The laminated wood with the acetylated lamina in tension side layer showed the largest creep under moisture-regain and moisture-loss conditions, whereas the laminated wood with the acetylated lamina in compression side layer had the smallest creep under moisture-loss condition, and had a little more creep than the laminated wood only with untreated laminae under moisture-regain condition. This phenomenon can be explained in terms of both the warps due to the differences in shrinkage and swelling between the acetylated and the untreated laminae and the differences in compressive and tensile creeps between them.

1.研究了木材在不同含水率条件下弯曲蠕变的应力依赖性及其蠕变过程中产生的声发射。在含水率变化与蠕变应变的指数回归方程中，回潮条件下指数拟合值随应力水平的增加而增大，而失水条件下指数拟合值均大于1，且与应力水平无关。AE通常在应力水平以上产生，在该应力水平内蠕变应变与施加的应力成比例。在风干和回潮条件下，AE在高于50的应力水平下产生，而在高水分含量和水分损失条件下，AE在高于35%的应力水平下产生。当蠕变破裂发生时，许多AE在标本破裂前即刻或短时间内产生。本文研究了乙酰化处理对层积材弯曲蠕变的降低作用。在复湿和失水条件下，压缩侧和拉伸侧层积材的蠕变均小于未处理层积材的蠕变。拉伸侧层积材在回潮和失水条件下的蠕变最大，压缩侧层积材在失水条件下的蠕变最小，在回潮条件下的蠕变略大于未处理层积材。这种现象可以用乙酰化和未处理的层片之间的收缩和溶胀差异以及它们之间的压缩蠕变和拉伸蠕变差异引起的翘曲来解释。