红锥木材蠕变特性研究

Creep Characteristics of Castanopsis hystrix Wood

采用4点加载方式对红锥木材试件进行短时间(420min)弯曲蠕变试验,获取红锥木材弯曲蠕变特性曲线,根据弯曲蠕变特性曲线确定红锥木材的粘弹性元件常数。同时研究红锥木材在强度极限内,应力水平与木材蠕变的关系。结果表明:当弯曲应力为σb20%时,J0(瞬间弹性柔量)为7.101×10-7 cm2/N、η0(粘性系数)为573.604×10-7 min.N/cm2、∑Ji(延迟弹性柔量)为0.694×10-7 cm2/N;当弯曲应力为σb30%时,J0为6.356×10-7 cm2/N、η0为513.636×10-7 min.N/cm2、∑Ji为0.972×10-7 cm2/N;当弯曲应力为σb40%时,J0为8.408×10-7 cm2/N、η0为436.293×10-7 min.N/cm2、∑Ji为0.784×10-7 cm2/N。结论:随着应力水平的增加,J0和∑Ji产生波动,应力水平为中等时(σb30%),J0有较小值,∑Ji有较大值;粘性系数η0则随着应力水平的增加逐级降低,级间降幅依次递增10.43%和15.06%,说明红锥在较高应力水平下抗蠕变能力下降较快。

By means of the 4-point loading method on the horse of Castanopsis hystrix wood samples,a short-term（420 min） bending creep test was conducted to obtain bending creep characteristic curve,and then to determine the viscoelastic element constants.The relationship between the creep and the stress level within the strength limitation of the wood was also examined.When the bending stress was σb20%,the related constants were J0（instantaneous elastic compliance）：7.101×10-7 cm2/N,η0（viscosity coefficient）：573.604×10-7 min·N/cm2,and ∑Ji（delayed elastic compliance）：0.694×10-7 cm2/N.When the bending stress was σb30%,J0：6.356×10-7 cm2,η0：513.636×10-7 min·N/cm2,and ∑Ji：0.972×10-7 cm2/N.When the bending stress was σb40%,J0：8.408×10-7 cm2/N,η0：436.293×10-7 min·N/cm2,and ∑Ji：0.784×10-7 cm2/N.It was concluded that with the increase of stress level,J0 and the ∑Ji fluctuated,when the stress level was in the middle（σb30%）,the value of J0 was low,and ∑Ji was high.Viscosity coefficient η0 decreased step by step when the stress level increased,the reduction amplitude between the interstage creased by 10.43% and 15.06%,respectively,indicating that C.hystrix creep resistant ability droped quickly under the higher stress level.