EJPAU, 2004, Volume 7, Issue 1
Wood Technology

The flexural creep behaviour of oriented strandboards OSB/3 10 mm thick was investigated for a period of 72 days. The samples divided into two series were loaded in the plane of the panel in 4-point bending under four stress levels: 30, 40, 50 and 60% of MOR (modulus of rupture). Values of rheological constants were calculated using the 3-element rheological model. Deflections increased about linearly with respect to stress level up to 50% of MOR. The creep process of samples tested at stress level of 60% of MOR was rather nonlinear. Many samples tested at this stress level failed before the experiment was completed.

The aim of the presented investigations was to analyse the influence of parameters of particleboards production on cutting properties of boards. Parameters that varied were temperature (180 and 220 °C) and pressure (2.5 and 4.0 MPa). Factors to define the cutting properties were: the work of fracture and the work of chip formation. Those factors describe the general work of cutting. Sharp and blunt tools were used. Cutting tests were carried out by using an equipped microtome technique.

The object of the presented research project was sapwood of Scots pine (Pinus sylvestris L.), which was subjected to thermal and hydrothermal treatment. The objective of the performed investigations was to determine fungal resistance of this material to wood destroying fungi. Experimental wood was modified in the atmosphere of air and water vapour in conditions of the following temperatures: 160, 190 and 220°C for 6 and 24 hours. Fungal resistance of modified wood was determined applying an accelerated mycological test. The following test fungi were used in the performed experiment: Coniophora puteana, Gleophyllum trabeum, Poria placenta and Coriolus versicolor. The obtained results showed a correlation between conditions of the performed hydrothermal process of wood treatment and its resistance to test fungi species. Wood modified in the atmosphere of water vapour at the temperature of 220°C for 24 hours was characterised by the highest resistance against the s

The study investigated deformations, stresses and the character of changes induced by the non-free shrinkage of beech timber specimens (Fagus sylvatica L.) in the radial direction, in the conditions of varied drying intensity. During the experiments, the program of intense drying (T=60°C, EMC=10%) and the program of moderate drying (T=40°C, EMC=15%) have been taken into consideration, and the values of the accepted timber shrinkage have been differentiated. The varied efficiency of the mechanical restraint of the timber specimens deformations has been obtained due to the use of dynamometers of various characteristics. The research results prove the relationship between the values of durable deformation and the values of accepted shrinkage

The presented study is of theoretical nature aiming to perform a numerical analysis of structural strength of skeleton furniture subjected to real useful loads. The objective of the performed investigations was to determine the state and distribution of stresses in the angle joint of a spatial structure of skeleton furniture. Experiments were carried out on dowel and tenon and mortise joints, which belong to the group of flat angle joints. The performed experiments allowed to develop a numerical model of a skeleton construction which was later used to perform calculations determining: reduced stresses according to the von Mises theory, tangential stresses in glue lines of dowel and tenon and mortise joints and tangential stresses in the wood of dowel joints. The results presented in this study are of cognitive nature. They determine values of stresses in joints of the loaded furniture piece and identify places with the greatest effort.

This study investigated the changes in the supramolecular structure of pine wood cellulose in situ treated by various of doses gamma radiation (from 20 kGy to 9000 kGy). From the dose of 120 kGy the degree of crystallinity (x_c) of wood cellulose slightly decreased, while at the dose of 500-4500 kGy dropped rapidly. At 9000 kGy occures a total degradation of cellulose, both crystalline and amorphous. Along with the increase in the gamma radiation of wood, both the crystallinity degree and the average size of the crystallites of cellulose decrease. The curve of changes in the crystallinity degree was similar to that of the changes in the average size of the crystallites of cellulose.