多测点无损检测法评估古建木材抗弯强度

为了提高无损检测手段预测古建木材抗弯强度的精度,用应力波仪和阻力仪对藏青杨旧材抗弯试样进行了多测点无损检测,通过对比试样抗弯强度,分析了无损指标与木材抗弯强度的相关性,讨论了测试手段、测点位置、测点数量对相关系数的影响,以及多参数时预测模型的最优自变量组合.结果 表明:增加测点数量可提高无损指标与木材抗弯强度的相关系数;当自变量较多时,逐步回归法适合应用于确定最优自变量组合,同时避免自变量共线性问题;相较于一元线性模型,使用最优自变量组合确定的多元线性模型可使无损指标与抗弯强度的相关系数和校正决定系数分别提高20.54％和42.92％,表明多测点无损检测法可以有效提高木材抗弯强度预测的准确性.

Evaluation of Bending Strength of Ancient Building Wood by Multi-point Nondestructive Testing Method

In order to improve the accuracy of nondestructive testing methods to predict the bending strength of ancient building wood, multi-point nondestructive test was carried out on ancient Tibetan Populus cathayana bending specimens with stress wave detector and resistograph detector. By comparing the bending strength of the specimens, the correlation between nondestructive testing index and the bending strength was analyzed. The influence of measur? ing method, location and number of measuring points on the correlation coefficient, as well as the optimal combina? tion of independent variables in the multivariate model were discussed. The results indicate that the correlation coeffi? cient between nondestructive index and bending strength increases with the increasing of the number of measuring points; the stepwise regression method can quickly determine the optimal combination of independent variables in the multivariate model, while avoiding the colinearity of independent variables. Compared with the univariate linear model, multivariate linear model determined by the optimal combination of independent variables can increase the correlation coefficients and adjust R square between nondestructive index and the bending strength by 20.54% and 42.92%, respectively, which proves that the multi-point nondestructive testing method can effectively improve theprediction accuracy of bending strength of ancient building wood.