Classification of log based on sound analysis and its application for grading system and drying process control

通过测量声波在原木横截面上产生的纵波的固有频率，确定原木的弹性模量。测定了用该原木生产的带髓材和定径材的Et值。结果如下：（1）静态弯曲试验结果表明，弹性模量（Es）与Et具有良好的线性关系，堆场打桩对纵波第三阶固有频率的影响较小，纵波声分析可作为一种合理的选材和控制系统。(2)由于后施胶材的Et和各层的Et平均值与原始原木的Et具有高度的线性关系，因此，这种原木的粗略分类可用于结构材和胶合板原料的选择。(3)由于干燥过程中固有频率的变化受Et的增加和水分解吸失重的影响，因此在已知的Et增加范围内，可以有效地作为干燥质量的粗略控制。(4)在集成材厂，利用纵波声波分析对原木进行分类。它可以作为一个合理的选择系统。

The modulus of elasticity (Et) of log was determined by measuring the natural frequency of longitudinal wave due to sound when hitting cross section. The Et of laminae and post-sized lumber with pith produced by the log were also measured. Results were as follows: (1) Et was recognized to be highly linear to the modulus of elasticity due to static bending test(Es).The third-term natural frequency of longitudinal wave was hardly affected by piling in stock yard as compared to the first or second ones,thus longitudinal wave sound analysis could be considered as a reasonable material selection and control system. (2) Since the Et of post-sized lumber and the average value of Et of laminae was recognized to be highly linear to Et of the original log, this rough classification of log could be useful in the selection of raw materials for structural lumber and glue-laminated lumber. (3) Since changing of natural frequency during drying process was affected by the increase of Et and weight loss due to desorption of water,it might be effective as rough quality control of drying within a well-known increase of Et. (4) In the glue-laminated lumber mill, the classification of log was conducted by longitudinal wave sound analysis. It could be efficient as a reasonable selection system for laminae.