Pre-grading of spruce logs containing frozen and unfrozen water by means of frequency-based nondestructive testing (NDT)

Abstract

The possibility for pre-grading of logs throughout the year has been evaluated based on dynamic modulus of elasticity (MOEdyn or simplified Edyn) by means of frequency-based nondestructive testing (NDTfreq). The challenge is that Edyn is variable in the frozen, partly frozen, and unfrozen states of logs (state of matter). In the unfrozen state, NDTfreq is reliable if the moisture content does not fall below fiber saturation. The state of the matter was tested via temperature measurements of air and log by means of an infrared technique and sensors, and information was evaluated from NDTfreq. The temperature measurements proved to be inefficient for industrial application because of unreliable data and long measurement times, whereas the NDTfreq measurements allowed the determination of meaningful damping factors. A sufficient level of predictability for more than 60% of the measurements was found. The log measurements in the partly frozen state are inconclusive because Edyn data fluctuate in the presence of both liquid and frozen water. For the completely frozen logs, a correction is introduced as a precaution that avoids an overestimation of Edyn in the unfrozen state.

Predicting structural timber grade-determining properties using acoustic and density measurements on young Sitka spruce trees and logs

“…There are several established NDT methods applied in sawmills for grading of timber boards (Ridley-Ellis et al 2016), such as the longitudinal stress wave propagation, which are suitable for the evaluation of timber quality on standing trees and logs (Legg and Bradley 2016). The stress wave (acoustic) velocity (SWV) can be measured by the resonance method, in which the fundamental frequency is considered, and the time-of-flight method (TOF), which measures the time required for a wave to travel between two sensors (Arriaga et al 2014(Arriaga et al , 2017Denzler and Weidenhiller 2016). The former is typically used on logs, while the latter one on standing trees (Wang 2013).…”

“…Acoustic measurements on logs have been frequently described (Tsehaye et al 2000;Wang et al 2004;Lindström et al 2009;Yin et al 2011; Baltrušaitis and Aleinikovas 2012;Denzler and Weidenhiller 2016). However, stress wave propagation in the stem of a standing tree is not fully understood (Wang et al 2004;Zhang et al 2011;Searles 2012).…”

Prediction of Douglas Fir Sawn Timber Yield Based on Log Computed Tomography

“…However, a linear regression model for , based on the Young's modulus from the FE model and on , led to an = 0.67. Therefore, we also looked at yield prediction models including , , even though this quantity is not used in practice in Europe -for logs in intermediate states between frozen and thawed, , cannot be determined reliably [19]. A further possibility for improving the prediction of the Young's modulus would be to base the FE model on a three-dimensional grid of fibre orientations instead of on a two-dimensional grid.…”

The Application of Labview-based Virtual Instrument Technology In Nondestructive Testing

“…This kind of human-computer interaction is implemented by parameter setting and output interface display. When a front panel is used, the LabVIEW platform system user can "draw" on the panel by operation, without the need of programming [4].…”

“…Tab. 4 shows results of leakage test of this crude oil pipeline leakage real-time monitoring and positioning system. From this table, we can understand the effectiveness of this crude oil pipeline leakage real-time monitoring and positioning system visually.…”