Design and development of a clamping device for fatigue testing of wood

Les, kot naraven material, se danes uporablja tudi za izdelke, ki so izpostavljeni dinamičnim obremenitvam. V fazi snovanja izdelka je zato zelo pomembno, da poznamo dinamične mehanske lastnosti lesa. Le-te izmerimo na namenskih merilnih strojih. Pri tem je ključnega pomena, da je merjeni material v stroj vpet togo. Pri pregledu literature ni mogoče najti standardiziranih testov določevanja dinamičnih trdnostnih lastnosti lesa. V okviru diplomskega dela smo zasnovali lasten vpenjalni sistem, ki je združljiv s strojem za merjenje dinamičnih trdnostnih lastnosti lesa, zasnovanim in izdelanim v Laboratoriju za mehansko obdelovalne tehnologije lesa (Univerza v Ljubljani, Biotehniška fakulteta). V prvem delu diplomskega dela je narejen pregled standardnih testov za določevanje statične trdnosti lesa in idejna zasnova omenjenega vpenjalnega sistema, v drugem delu pa je narejen preračun oz. dimenzioniranje vpenjalne priprave. Vpenjalna priprava je zasnovana tako, da z inovativno rešitvijo z vpenjanjem s pomočjo distančnikov omogoča tudi preizkušanje manjših vzorcev. Izbrana rešitev je trdnostno preverjena z metodo končnih elementov v programskem paketu Abaqus. Za izbrano konstrukcijo vpenjalne priprave so v programskem paketu SolidWorks izdelane delavniške risbe.Wood is a natural material used also for pruducts exposed to dynamic loads. Consequently, when designing a product, it is of utmost importance to know the dynamic mechanical properties of wood. Special measuring machines are used to measure these properties. It is of key importance that the measured material is rigidly clamped into the machine. When studying literature, it was impossible to find standardised tests for determining dynamic strength properties of wood. As part of the thesis, we designed our own clamping system that can be used with the machine for measuring dynamic strenght properties of wood. The system was designed and produced in the Laboratory of Mechanical Processing Technologies (University of Ljubljana, Biotechnical Faculty). In the first part of the thesis, an overview of standard tests for determining statical strength of wood and the concept of the mentioned clamping system are described. In the second part, the calculations concerning the dimensions of the clamping device are presented. The clamping device is designed in such a way that it makes it possible, based on an innovative solution, to test also smaller samples, using spacers. The selected solution is checked in terms of strength with the finite element method in the Abaqus software package. In the SolidWorks software package, workshop drawings are produced for the selected design of the clamping device