Effective non-destructive methods for identifying poor quality and knotty timber in standing trees can contribute to higher quality timber reaching the appropriate processing mills and to a reduction in transport costs of harvested timber. Eucalyptus nitens is a major temperate plantation hardwood species primarily used in paper production. More recently it has also been considered as a potentially suitable source to produce high quality sawlogs. One important aspect of the economic viability of this sawlog business is being able to differentiate between pruned (higher quality) and unpruned (lower quality) plantation eucalyptus. Low quality stems contain higher percentages of features such as knots and/or branch traces that lessen the quality and value of logs that can be produced. Unfortunately, it is not possible to visually discriminate between pruned and unpruned standing trees and while wood processors do use large x-ray image machines during processing, finding ways to reduce transportation costs by enhancing timber quality remains a major challenge. This research presents results from ultrasonic and thermal testing to non-destructively detect internal defects in 17 year old E. nitens grown in Tasmania, Australia. For the investigation, 12 samples (billets) from different parts of the trunk of an E. nitens tree were selected and conditioned to levels of forest moisture content of 120% (70% water content). The samples were scanned by two ultrasonic techniques through-transmission and pulse-echo. In the through-transmission method, the waves were propagated at 10 cm intervals in the longitudinal direction and at 45 degree angle spacing in the circumferential direction. In the pulse-eco method, the surface of the billets were scanned in 10cms intervals around the billets. Unpruned billets were also evaluated for moisture content using a thermal camera to examine the effect on ultrasonic wave propagation. The ultrasound revealed significant differences between recorded ultrasonic waveforms propagated through unpruned billets and pruned ones. Unpruned billets produce a much larger effect on ultrasonic waves when compared with the waves propagated by the pruned billets tested. The thermal camera highlighted that wet knotty wood tends to have higher moisture content than clear wood except when the timber is air dried which produces a slightly lower moisture content being detected in knotty timber over clear wood. Results provide evidence that in-field non-destructive techniques for standing trees internal structural assessment are viable and could be operationalised within Tasmanian E. nitens plantations.

中文翻译：

---

超声波和热测试可无损识别人工林桉树的内部缺陷

用于识别立树中劣质和多节木材的有效非破坏性方法有助于将更高质量的木材送到适当的加工厂，并降低采伐木材的运输成本。Eucalyptus nitens 是主要用于造纸的主要温带种植园硬木树种。最近，它也被认为是生产高质量锯材的潜在合适来源。这种锯木业务的经济可行性的一个重要方面是能够区分修剪过的（质量较高的）和未修剪的（质量较低的）种植园桉树。低质量的茎包含更高百分比的特征，例如节和/或分支痕迹，这些特征会降低可生产的原木的质量和价值。很遗憾，无法在视觉上区分修剪过的和未修剪过的立木，虽然木材加工商在加工过程中确实使用大型 X 射线成像机，但寻找通过提高木材质量来降低运输成本的方法仍然是一项重大挑战。这项研究展示了超声波和热测试的结果，以无损检测澳大利亚塔斯马尼亚州 17 岁 E. nitens 的内部缺陷。为进行调查，选择了来自 E. nitens 树干不同部位的 12 个样品（坯料），并将其调节到 120%（70% 的含水量）的森林含水量水平。通过透射和脉冲回波两种超声波技术对样品进行扫描。在直通传输方式中，波在纵向以 10 厘米间隔传播，在圆周方向以 45 度角间隔传播。在脉冲-生态方法中，以 10cms 的间隔在钢坯周围扫描钢坯表面。还使用热像仪评估了未修剪钢坯的水分含量，以检查对超声波传播的影响。超声波显示通过未修剪的坯料和修剪的坯料传播的记录超声波波形之间存在显着差异。与测试的修剪过的坯料传播的波相比，未修剪过的坯料对超声波的影响要大得多。热像仪突出显示，湿多节木材往往比透明木材具有更高的水分含量，除非木材风干时，在多节木材中检测到的水分含量略低于透明木材。结果提供的证据表明，用于立木内部结构评估的现场无损技术是可行的，并且可以在塔斯马尼亚 E. nitens 种植园内实施。