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Assessment of the impact of the type of wood on the properties of snowboard board core
Jiřík, Adam ; Borůvka, Vlastimil (advisor) ; Gašparík, Miroslav (referee)
Snowboarding as one of the fastest developing sports nowadays forces
manufacturers to improve equipment for this sport or to introduce other innovations
that would enhance pleasure of the ride. The most important and expensive part of the
equipment is the snowboard itself. So far, the high-quality snowboards with the best
ride properties include wood core. Every year a competition called Good Wood is
organized for the best snowboard models of the season.
This thesis deals with design and assessment of the new innovative composition
of snowboard cores using different combinations of wood and other structural solutions.
These compositions were compared with an already time-proven composition currently
used by Hackboards Ltd. company. By using the stress simulation with the finite
element method in SolidWorks Simulation program the stress progress and the
deflection size of designed cores and the reference core were found out. Part of this
thesis was also determining some of the physical and mechanical properties of native
wood types according to relevant norms. Measured values were used to verify
possibilities of using data of appropriate wood type from literatur efor simulation.
Designed composition of the wood core formed by battenboard combining by
poplar and beech reached very similar values as the reference composition formed by
battenboard made of poplar and ash. The composition of combined laminated poplar
and beech veneers showed a little worse properties. The composition formed by beech
battenboard and the composition of laminated beech veneers showed worse properties
in comparison with the reference composition.
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Trends in the design and creation of new materials
Rodrová, Veronika ; Gaff, Milan (advisor) ; Borůvka, Vlastimil (referee)
The objective of my research is to examine the influence of densified wood in combination with native wood on its mechanical properties such as moduls of elasticity, bending strength, limit of proportionality, bendability coefficient and tensile-shear strength of glued line.
The examined woods are Europen beech (Fagus Sylvatica L.) and Aspen (Populus tramula L.). The tests were carried out on speciemens with different thickness. The densification by 10% and 20% was performed. For the glued joint polyurethane adhesive and polyvinylacetate glue were used.
The thesis includes simulation of the properties, their computer program tetsing, and the comparsion with the values obtained from real measurement. The purpose of this part of thesis is to achieve a simulation that will replace laboratory tests or disprove this method of scientific research and deepen our knowledge of proceses occuring during the pursued way of stress.
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Rheological characteristics of untreated and thermally modified wood under long-term loading in bending
Berková, Tereza ; Borůvka, Vlastimil (advisor) ; Ruman, Daniel (referee)
Heat-treatment belongs to the most ecological methods of wood preservation methods and increase of its natural stability in exposition to outdoor conditions. Research of mechanical properties opens new possibilities of thermowood usage in general.
Wood appertains to viscoelastic materials and due to long-term loading creeps. There currently rise both elastic deformation, deformation elastic in time and plastic deformation. Partially there are irreversible changes due to stress even after unloading.
This work presents first insight to the matters of thermowood rheology and inspects its behavior under long-term loading in bending. This paper compares ratio of these three types of deformation in untreated wood and thermally modified wood in seven different temperatures (140; 160; 180; 190; 200, 210°C). The samples were exposed to 600 hours applied loading covering 40% of ultimate stress (modulus of rapture). Test were performed under constant conditions in special creep units in conditioning kiln. Increasing deformation under constant load was analyzed by Burger rheological model.
The results show that samples treated under lower temperatures (140 and 160°C) exhibit greater creep than untreated wood. This result is positive for structural usage of wood. On the other hand the samples treated under higher temperatures levels (200 an 210°C) display deterioration of mechanical properties. This is due to changes in wood structures caused by heat-treatment.
The most important impact of this work goes to future research of this field. Next development has to apply for the best quality of samples and also select rather prismatic parallelism than transversal one. Also application of 40% ultimate stress loading appeared as too high and together with wood defects led to destruction of samples.
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