DEFORMATION OF ROUND PINE ASSORTMENT OF CONSTRUCTION SIZE

Urgency of the research. Study of wood behavior under load will allow us to deepen our understanding of technological processes and evaluate performance characteristics of finished product. Target setting. Knots are the main flaw that forming defects. Their influence on strength and deformation of small diameter wood has not been studied yet. Therefore, determination of indicators for wood mechanical properties with defects, taking in consideration their moisture content will allow to determine beams design in wooden structures. Actual scientific researches and issues analysis. There are some studies today how to determine mechanical state of wood under different methods of load application. However we don’t have publications which examine the issues of applying load to samples of construction dimensions with defects. Uninvestigated parts of general issues defining. Construction is one of the main wood consumer. It is known that wood structures can come as round wood of coniferous and hardwood . The presence of wood flaws such as knots and cracks affects it’s strength significantly. It should be noted that experimental and theoretical results of studies of wood flaws influence on its strength refer only to the presence of knots in lumber. Dependence of round timber strength characteristics on flaws and wood moisture content is not well understood. In this regard it becomes necessary to determine these dependencies and opportunity to use small diameter logs in building structures. The research objective. The main purpose of this study is to present some results of experimental investigation of how deformation of small diameters round pine assortment depends on presence of knots and moisture content under compression parallel to grain. The statement of basic materials. This article presents some study results about a pattern of deformation development in small diameters round pine assortments depending on size of knots and wood moisture content. Deformation was higher in test samples with knots and moisture content above saturation limit of cell walls than in control samples. The lower deformation was observed in dry samples with W – 16-18 %% as well as in samples with the knots. Total value of residual deformation of dry wood is determined . It should be noted that dry wood has residual deformation after 30th loading cycle. Conclusions. It is determined that under application of compressive static load along the grain with the upper compression limit which is lower than conditional limit of proportionality the process of deformation for wood with knots and without knots is almost the same. The control samples were deformed less and deformation value of samples with knots had higher numerical value and increased with the size of the knots.