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Öğe 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, RezaFreshly 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.Öğe Optimizing Lumber Drying Schedules For Oriental Beech and Sessile Oak Using Acoustic Emission(North Carolina State Univ Dept Wood & Paper Sci, 2020) Unsal, Oner; Dundar, Turker; Gorgun, Hizir Volkan; Kaymakci, Alperen; Korkut, Suleyman; As, NusretThe aim of this work was to detect sounds providing evidence of the creation of drying defects and to correlate such data with drying quality. A further goal was to establish sound wave thresholds of ideal drying through the drying process by using an acoustic emission (AE) monitoring method. Thus, it is projected to decrease long drying times and also drying costs by reaching to ideal drying schedules. In this study, commercially preferred sessile oak and oriental beech structural lumbers were dried with three different schedules in a conventional kiln. The lumbers were listened to with AE sensors while drying according to the first two schedules, which were called protective and severe, respectively. AE events of the drying experiments were compared with ambient conditions and drying classes according to the standard of European Drying Group. The third drying schedule was optimized based on the AE peaks and applied. The results showed that ideal drying times were reduced up to 19% relative to the protective drying schedule, while obtaining the same drying quality for both species.Öğe SURFACE ROUGHNESS AND WETTABILITY PERFORMANCE OF THERMALLY MODIFIED ROWAN WOOD AS A FAST-GROWING SPECIES(Inst Technol Drewna, 2021) Candan, Zeki; Gorgun, Hizir Volkan; Korkut, Suleyman; Unsal, OnerThis study aims to examine the effect of the thermal modification process on the surface roughness properties of the wood of rowan (Sorbus aucuparia L.) as a fast-growing species. Four thermal modification processes were applied, with temperatures of 160 and 180 degrees C and durations of 2 and 4 hours. In total five groups were compared, including the untreated group. Arithmetical mean roughness, maximum height, ten-spot average roughness, and root-mean-square deviation were measured using a stylus-type profilometer, both parallel and perpendicular to the grain, according to the JIS B 0601 standard. Wettability was determined by measuring the contact angle of a droplet of distilled water. After dripping, the camera captured several images to measure the contact angle. The results showed that thermal modification decreases the wettability of the samples. Moreover, increments in temperature and duration may further decrease wettability. On the other hand, there are no significant differences between groups in terms of the surface roughness values, measured both parallel and perpendicular to the grain, except for two groups. It is concluded that these process conditions did not substantially change the surface roughness properties of rowan wood panels. However; the decrease in wettability may provide new possibilities for the use of less-known wood species.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, OnerWood 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.
