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Analysis of methods for determining wood moisture by non-destructive methods
Změlík, Jiří ; Zach, Jiří (referee) ; Vaněrek, Jan (advisor)
Subject of this bachelor thesis is the analysis and comparison of hygrometers considering their price, availability and applicability. Theoretical part compared available types of hygrometers based on their operating principle. Subsequently, resistance, capacitive and microwave portable hygrometers were compared in more detail. There were five reviewed hygrometers in total, with three of them capacitive and one of each resistance and microwave. The measurement was performed on beech and spruce trees at gravimetrically known humidity, ranging from extremely low to extremely high values (even out of bounds recommended by the manufacturer). The evaluation of the methods was performed according to the Saaty´s AHP method. Hygrometers were then selected by their optimization. After the experimental part, the suitability of individual methods was determined. The best method was capacitive, followed by resistance and the worst microwave method.
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Hodnocení vybraného elektrického vlhkoměru při měření vlhkosti dřeva smrku v průběhu procesu navlhání
Konečný, Filip
The content of this bachelor's thesis deals with the measurement of the moisture content of spruce wood (Picea abies (L.) Karst.) in the wetting process. Spruce wood was added to zero moisture (w = 0%) and then stored in an air-conditioned room. Wood moisture was measured using an Orion 950 dielectric hygrometer. The moisture values measured on this hygrometer were subsequently compared with the actual moisture found, which was determined using the gravimetric method. The interface of the selected hygrometer enables the setting of the wood density value as well, thus allowing the comparison of the wood moisture with the actual density and with the table density given in the tables from the wood hygrometer manufacturer. The measured spruce wood samples were divided into two groups of 15 pieces each, namely samples without defects or with only minimal defects, and samples with larger defects, especially with resin streaks or knots. Most accurately, the hygrometer measured with the actual density of the samples for both groups. There was always a very significant difference of values when the table density was set.
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TEMPERATURE MOISTURE PROCESS STUDY IN MODERN WOOD STRUCTURES
Dohnal, Jakub ; Hradil, Petr (referee) ; Straka,, Bohumil (referee) ; Pěnčík, Jan (advisor)
In building structures wood is very often used as construction material and can also be used for supplemental non-supporting structures, e.g. as wood panelling, screening elements, etc. The most common woody plant species that can found in the biotope of the Czech Republic are Norway spruce (Picea abies L.) and Scots pine (Pinus sylvestris L.). Wood as construction material is popular in architect comunity as well as this material like also investors, who prefer living in healthy and natural environments. Wooden structures are also popular with structural engineers for their good mechanical properties and low weight, which, however, depends on moisture. Wood properties vary in every natural way and need to be taken into account at the beginning of the designing process. This dissertation aims to contribute to the description of mechanical characteristics of wood during changes of moisture content in the wood structure. Various experimental tests and numerical modelling were used in the thesis in order to reach the aims. The experimental tests examined mechanical properties at different sample moisture of selected woody plant species. Subsequently, the obtained values were compared with values available in specialist and scientific literature, so that these values could subsequently be used as input values for numeric calculations. The conclusions of the dissertation will contribute to more accurate calculations and further analysis.
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Analysis of methods for determining wood moisture by non-destructive methods
Změlík, Jiří ; Zach, Jiří (referee) ; Vaněrek, Jan (advisor)
Subject of this bachelor thesis is the analysis and comparison of hygrometers considering their price, availability and applicability. Theoretical part compared available types of hygrometers based on their operating principle. Subsequently, resistance, capacitive and microwave portable hygrometers were compared in more detail. There were five reviewed hygrometers in total, with three of them capacitive and one of each resistance and microwave. The measurement was performed on beech and spruce trees at gravimetrically known humidity, ranging from extremely low to extremely high values (even out of bounds recommended by the manufacturer). The evaluation of the methods was performed according to the Saaty´s AHP method. Hygrometers were then selected by their optimization. After the experimental part, the suitability of individual methods was determined. The best method was capacitive, followed by resistance and the worst microwave method.
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