Лесотехнически Университет

Резюме

The Douglas-fir is a perspective species for Europe, introduced in Bulgaria long ago. During this time many studies have been made on the growth and productivity of forests of this tree species. Mechanical properties are an important part in the design of timber structures and the calculation of processing regimes. The values given for the properties depend on the altitude and the location of the wood under study in the stem.

The subject of the research in this study is the Douglas fir wood and the determination of some mechanical properties of the wood, which  has been done for the first time in our country. Standard methods and test bodies were used to establish the mechanical properties in this study.

Резюме

As the water content changes, the wood cells shrink or swell. These are some of the processes characterising the variability of wood. They greatly complicate processing and limit the application of wood materials. These properties depend on many factors, one of which is the scale (dimensions) of the wooden samples. Many observations show that the shrinkage and swelling processes proceed differently when the wooden samples is a few millimeters or a few centimeters. There is an even greater difference in the behavior of earlywood and latewood when they are examined separately.

The article study the processes of shrinkage and swelling during repeated wetting and drying. Samples with a constantly decreasing cross-section were investigated.

Резюме

Wood is widely used to produce sound emitters (decks) of musical instruments. This wood is called resonant. Although this name does not accurately reflect the physical nature of the phenomena occurring in wood when used in musical instruments, it is widely used in practice and in technical literature. 
The article examines the parameters that make a wood resonant. It is suggested that wood should be tested only when it meets part of the requirements and does not have good sound qualities. In this way, the influence of one or several factors can be isolated, and their importance on the quality of the wood can be determined.