Papers by Author: L'uboš Krišták

Abstract: Article discusses effect of environmental condition on heat transfer from wood sample during burning process. The aim of the paper is to characterize temperature vs time dependence of irradiated wood surface as a function of heat source distance , total heat transfer coefficient and thermal diffusivity . From temperature vs time dependence on the irradiated side is possible to compute heat ignition temperature of wood as one of the most important characteristics of wood burning. All measured values of studied parameters are in very good agreement with table values.

Abstract: The paper deals with the research into the heat transfer during high temperature pressing of 3D moulded veneer plywood consisting of seven plies. Plywood was being pressed at two temperatures (110 °C and 120 °C), whereby the impact of the pressing temperature on the speed of heat transfer across the surface and through the mass of the pressed material was evaluated. Following the experiment the optimum pressing time was determined. Attention was paid also to the evaluation of impact of temperature on selected mechanical and physical properties of plywood. Following properties were evaluated: bending strength, modulus of elasticity in bending, compression degree and density. Results indicate that higher pressing temperature decreases the pressing time by 23,7 s representing a 7.3% time saving. In addition, higher pressing temperature increases slightly the bending strength (by 7.5%) as well as modulus of elasticity in bending (by 11.8%).

Abstract: The article presents results of the granulometric composition of chip particles when sanding wood (beech) and wood-based materials (particleboard and semi-hardboard) using different types of sanders – wide belt sander, narrow belt sander, and hand sander. On the basis of the carried out sieve analyses, the proportion of produced particles, which can be marked as dust with the particle size of ≤ 80 μm, is high at the interval from 89.21% - 96.29 %. The highest percentage of dust particles was reached at dust from the hand disk sander. At the end of the article we point to possible technical safety measures – additional dust exhausting, suction, to possibly reduce the dust getting to the working environment.

Abstract: The article deas with evaluation of the selected parts of a life cycle of timber formwork on a wooden basis, notably in the field of manufacturing and usage. Experimental research focused mainly on assessing the possibilities of energy savings in a manufacturing process through shortening a technological process of moulding. By optimalisation of a moulding period, it is possible to achieve considerable energy savings. Based upon the experiments, we created an experimental model in order to determine optimum moulding time. Withing a process of usage, we evaluated particular materials with regard to re-use cycle based upon the experience of commercial manufacturers.