Türker Dündar

Dimensional Stability of Fire-Retardant-Treated Laminated Veneer Lumber

Test of fire-retardant-treated (FRT) laminated veneer lumber (LVL) indicated moisture gain under adsorption and moisture loss under desorption conditions. The moisture content of FRT specimens increased considerably under adsorption conditions compared with control specimens, while it was not found to be a significant difference under desorption conditions. The statistical findings revealed that impregnation with chemical salts had significant effects on the expansion properties. Fire-retardant treatment also had meaningful effects on the swelling properties. However, the expansion and swelling properties of the LVL were not affected significantly by the veneer drying temperature. Generally, equilibrium moisture content of LVL decreased with increasing veneer drying temperature. The interactions between fire-retardant chemicals and veneer drying temperature were also found to be insignificant.

Potential of ultrasonic pulse velocity for evaluating the dimensional stability of oak and chestnut wood.

The objective of this study was to examine the potential of ultrasonic velocity as a rapid and nondestructive method to predict the dimensional stability of oak (Quercus petraea (Mattuschka) Lieblein) and chestnut (Castanea sativa Mill.) that are commonly used in flooring industry. Ultrasonic velocity, specific gravity, and radial, tangential and volumetric shrinkages were measured on seventy-four 20×20×30-mm(3) specimens obtained from freshly cut oak and chestnut stems. The ultrasonic velocities of the specimens decreased with increasing moisture content (MC). We found that specific gravity was not a good predictor of the transverse shrinkages as indicated by relatively weak correlations. Ultrasonic velocity, on the other hand, was found to be a significant predictor of the transverse shrinkages for both oak and chestnut. The best results for prediction of shrinkages of oak and chestnut were obtained when the ultrasonic velocity and specific gravity were used together. The multiple regression models we developed in this study explained 77% of volumetric shrinkages in oak and 72% of volumetric shrinkages in chestnut. It is concluded that ultrasonic velocity coupled with specific gravity can be employed as predicting parameters to evaluate the dimensional stability of oak and chestnut wood during manufacturing process.

Prediction of transverse shrinkages of young-growth Sitka spruce (Picea sitchensis) and western hemlock (Tsuga heterophylla) with ultrasonic measurements

Abstract The objective of this study was to examine the potential of acoustic measurement as a rapid and nondestructive method to predict the dimensional stability of young-growth Sitka spruce and western hemlock. Ultrasonic velocity, peak energy, specific gravity, and radial and tangential shrinkages were measured on twenty-four 25-×102-×y 25-mm specimens obtained from a 58-year-old stand in Southeast Alaska. We found that specific gravity and peak energy of ultrasonic signals were not good predictors of transverse shrinkage, as indicated by poor correlations. Ultrasonic velocity, on the other hand, was found to be a significant predictor of transverse shrinkage and therefore has good potential to be used as a field method to evaluate dimensional stability. The single-parameter prediction model explained 86% of transverse shrinkages in western hemlock and 71% of transverse shrinkages in Sitka spruce. Further study is needed to test the capability and feasibility of using acoustic velocity to predict both longitudinal and transverse shrinkages of wood in standing trees.

MICRO-MECHANICAL PROPERTIES OF OAK WOOD AND COMPARISON WITH STANDARD-SIZED SAMPLES

The aim of this study was to investigate micro-mechanical properties of Oak (Quercus petraea) wood and to compare with standard-size test specimens values. Bending strength, modulus of elasticity in bending, compression strength and tensile strength were determined using micro- and standard-size mechanical test samples. In the micro- and standard size samples, bending strengths were evaluated as 71,2 MPa and 99,4 MPa, modulus of elasticity in bending as 2741,3 MPa and 11394,1 MPa tensile strengths as 98,7 MPa and 93,8 MPa and compression strengths as 45,4 MPa and 46,6 MPa respectively. The results showed that the bending strength, modulus of elasticity and compression strength of the micro-size samples were lower compared to the standard-size samples, while the tensile strength was higher in the micro-size samples. The compression strength values of micro- and standard-size samples were not significantly different. The regression analyses indicated a positive linear regression between the mechanical properties of micro- and standard-size samples. Micro-size specimens can be used to estimate the mechanical properties of Oak wood when obtaining standard-size specimens is not possible.

PAVLONYA KERESTELERİNİN TUTKALLI LAMİNE KESRETE ÜRETİMİNDE ORTA TABAKADA KULLANIM OLANAKLARI

Bu calismanin amaci hizli gelisen ve gorece dusuk kalitede bir oduna sahip olan pavlonya (Paulownia elongata)’nin lamine yapi kerestesi uretiminde orta tabakalarda kullanilma olanaklarinin arastirilmasidir. Boylece ekonomik degeri dusuk olan pavlonya odununun katma degeri yuksek bir urune donusturulmesi amaclanmaktadir. Bu amacla 10×110×1000 mm olculerinde lameller ve poliuretan tutkali kullanilarak ortadaki uc tabakasi pavlonya, alt ve ust yuzey tabakasi saricam olmak uzere 5 tabakadan olusan 5 adet deney ornegi uretilmistir. Karsilastirmak amaciyla tamami saricam lamellerden olusan 5 adet kontrol ornegi uretilmistir. Uretilen deney ornekleri uzerinde yogunluk, egilme direnci ve egilmede elastikiyet modulu denemeleri gerceklestirilmistir. Elde edilen sonuclar laminasyonda orta tabakada pavlonya kullanilan orneklerin yogunluk degerlerinin onemli oranda azaldigini, buna karsin egilme direnci ve egilmede elastikiyet modulu degerlerinde istatistik olarak anlamli bir kayip meydana gelmedigini gostermistir. Sonuc olarak laminasyonda dolgu malzemesi olarak orta tabakada pavlonya kullanilmasinin yapisal bakimdan avantaj saglayan hafif, buna karsin yeterli dirence sahip yapi elemanlarinin uretimine imkân saglayacagi ve ekonomik degeri dusuk pavlonya odununun ekonomik degeri yuksek bir urune donusturulebilecegi tespit edilmistir.