含水率对微钻阻力仪钻针阻力的影响

Effect of moisture content on drill resistance of micro drill resistance instrument

【目的】微钻阻力仪钻针阻力与木材密度正相关,与木材含水率的关系尚不明确。为了科学、合理地解释微钻阻力仪的钻针阻力,本研究进一步研究含水率与钻针阻力之间的关系。【方法】使用Resistograph 650-S微钻阻力仪测量包含针叶树、软阔叶树、硬阔叶树9个树种的木材在湿木状态和绝干状态下的钻针阻力,首先初步判断木材含水率与钻针阻力之间的关系;然后建立各树种木材含水率、木材绝干密度双因子与钻针阻力之间的广义相加模型以及木材绝干密度单因子与钻针阻力之间的广义相加模型,分析两个模型的拟合结果,分析木材含水率对微钻阻力的影响程度;最后建立每个树种木材含水率与湿木状态与绝干状态下钻针阻力差值之间的广义相加模型,分析木材含水率对钻针阻力的影响规律。【结果】1)麻梨、李、桃和樱桃这4个树种湿木状态与绝干状态下钻针阻力平均值差值的平均值小于0,毛白杨、泡桐、马尾松、杉木、麻栎这5个树种的平均值大于0。2)各树种双因子模型R^(2)的平均值比单因子模型高0.231,相比提高了52.620个百分点;各树种双因子模型方差解释率的平均值比单因子模型高22.475%,相比提高了48.892个百分点;各树种双因子模型AIC的平均值比单因子模型低60.39,相比降低了5.489个百分点。3)各树种湿木含水率与湿木状态与绝干状态下阻力差值的GAM模型的自由度在1~6.062之间,P值在0~0.619之间,F值在0.25~23.45,R^(2)在0~0.644之间,方差解释率在0.579%~66.7%之间。【结论】1)含水率对钻针阻力有显著有影响,增加含水率因子能显著提高钻针阻力的方差解释率。2)不同树种之间含水率对钻针阻力的影响程度和影响规律存在较大差异。

【Objective】Drill resistance is positively correlated with wood density,but the relationship between drill resistance and moisture content is not clear.In order to scientifically and reasonably explain drill resistance,this paper further studied the effect of moisture content on drill resistance.【Method】The resistance of 9 tree species including conifer,soft broad-leaved and hard broadleaved trees was measured by Resistograph 650-S under wet and absolutely dry conditions.Firstly,the relationship between moisture content and drill resistance was preliminarily judged.Then,a generalized additive model between wood moisture content,wood absolute dry density and drill resistance and the model between wood absolute dry density and drill resistance were established.The fitting results of the two models were analyzed,and the effect of moisture content on drill resistance was analyzed.Finally,a generalized additive model between the moisture content of each tree species and the difference in drill resistance was established to analyze the influence law of moisture content on drill resistance.【Result】1)The average value of the difference in the drill resistance among the four tree species(Pyrus serrulate,Prunus salicina,Amygdalus persica and Cerasus pseudocerasus)under wet and absolutely dry conditions was less than 0,while that of five tree species(Populus tomentosa,Paulownia fortune,Pinus massoniana,Cunninghamia lanceolate and Quercus acutissima)was above 0.2)The average R^(2) of the two-factor model was 0.231 higher than that of the single-factor model,exhibiting an increase of 52.620%.The average value of the variance interpretation rate of the two-factor model was 22.475%higher than that of the single-factor model,exhibiting an increase of 48.892%.The average AIC of the two-factor model was 60.39%lower than that of the single-factor model,showing an increase of 5.489%.3)The freedom degree of the GAM model between moisture content and the resistance difference between the wet wood state and the dry state was 1-6.062,the P value of the model was 0-0.619,the F value of the model was 0.25-23.45,the R^(2) of the model was 0-0.644,and the explanation rate of variance of the model was 0.579%-66.7%.【Conclusion】1)Moisture content has a significant effect on drill resistance,and adding moisture content as a factor while modelling can significantly improve the variance interpretation rate of drill;2)There are great differences in the influence degree and influence law of moisture content on the drill resistance among different tree species.