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    Efficiency of radiofrequency-vacuum (RF/V) technology for mixed-species drying of wood disks with inherent defects
    (Taylor & Francis Inc, 2020) Tarmian, Asghar; Ciritcioglu, Hasan Huseyin; Unsal, Oner; Ahmadi, Peyman; Gholampour, Behnam; Oladi, Reza
    Freshly cut 30-mm-thick wood disks of Scots pine, Caucasian elm, narrow-leafed ash, wild cherry, black walnut, and European alder with various natural grade defects were dried together in a radiofrequency-vacuum (RF/V) dryer. A mild four-step drying schedule at the maximum temperature of 45 degrees C and power density in the range of 1-2 kWm(-3)with an on-off control of RF radiation at the final step was used. The moisture content of the disks at the end of drying ranged from 10.6% to 13.4%. An almost uniform radial moisture gradient developed in the dried disks. The six wood species, however, exhibited variations in checking. The RF/V drying schedule used here was able to completely inhibit near-bark radial checking in all disks but pine and elm, whereas it failed to efficiently prevent V-cracking in pine and ash with a high mean tangential to radial shrinkage anisotropy (S-T/S-R). A strong positive correlation was also found between S-T/S(R)and the proportion of V-cracked disks. The occurrence of ring failure within the reaction wood-containing disks of walnut, pine, and elm was almost completely prevented by the drying schedule, but a significant correlation was observed between the pith eccentricity and V-crack length in the compression wood-containing disks of pine. All other natural defects, i.e., scar in cherry, bark pocket, double or triple pithing in walnut and elm, sound knots in pine, and roundness deviation, exhibited no statistically significant effect (p > 0.05) on check formation.
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    Öğe
    Using acoustic emission technique for detecting checks on industrial-size beech wood disks during drying
    (Taylor & Francis Inc, 2022) Ciritcioğlu, Hasan Hüseyin; Tarmian, Asghar; Görgün, Hızır Volkan; Unsal, Oner
    Wood disks are very susceptible to checking during drying. The present study was aimed to determine a suitable transducer mounting configuration to detect the drying checks with acoustic emission (AE) technique. AE generated during drying of 30-mm-thick beech (Fagus orientalis L.) wood disk with a diameter of 300 mm were monitored using piezoelectric AE transducers operating at frequency of 50-200 kHz. The transducers were directly attached on the disks with four combinations depending on the sensor number and grain direction. Total number of AE events and event rate were associated with drying time and checking features. The successive formation of near-bark radial checks was detected due to fluctuations in the AE event rate. Results showed that if the transducers are attached to the disk lateral surfaces, the formation of pith checks cannot be detected in the early stages of the check formation. The V-shaped cracks can be only detected when the transducer is mounted very close to the crack location. Overall, our results showed that more than two transducers are required to detect all types of checks occurred during drying of wood disks of this size. They should be attached parallel to the grain, one near to the pith and the rest at a suitable distance around periphery of the disk.