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This paper presents an experimentally validated model for the computational analysis of metal-reinforced wooden composites. The model can be used in both research and in industry to effectively estimate how much a certain composite design improves the bending stiffness and strength of a hybrid metal-reinforced wooden component. A model based on computer simulations allows the prediction and analysis of the mechanical behaviour of a hybrid composite material consisting of several interconnected components made of different base materials. The model for different boundary conditions and parameters provides the correct data on stiffness, especially bending, and the associated maximum displacements. It allows for a variation of the mechanical and geometrical properties, and makes it possible to observe the initiation of irreversible change in the window-frame member. The model enables parametrical simulations to find the optimum layout of reinforcements in the window-frame member, as well as to make estimations of the maximum performance of certain designs.

The paper presents a computational model for the simulation of surface initiated fatigue crack growth on contacting mechanical elements as used in gears, bearings, etc. A simple equivalent model of two cylinders is used for simulation of fatigue crack growth under conditions of rolling and sliding contact. The equivalent model is subjected to the normal and tangential contact forces which also take into account the influence of EHD-lubrication conditions as well as the associated lubricant pressure acting on the crack faces. The VCE method in the framework of FEA is used for simulating the fatigue crack propagation from the initial crack up to the formation of the surface pit.

The paper describes a two-dimensional computational model for simulation of the surface-initiated fatique-crack growth in the contact area of gear-teeth flanks. The discretised model of gear teeth is subjected to normal loading (Herzian contact pressure), tangential loading (friction between gear-teeth flanks) and additional external contact forces that arise the EHD-lubrication conditions. The J-integral method in the framework of the finite-element analysis is used for the simulation of the fatique-crack propagation from the initial to the critical crack length, when the material's surface layer breaks away and a pit appears on the surface. The comparison of computational and experimental results shows that the proposed model reliably simulates the surface-fatique crack growth under contact loading and can be used for computational predictins of surface pitting for various contacting mechanical elements like gears, bearings, wheels, etc. V tem prispevku je predstavljen dvodimenzijski računski model za simuliranje širjenja površinsko začetne utrujenostne razpoke v stičnem področju dveh zobnih bokov zobnikov. Diskretiziran model zoba zobnika je obremenjen s pravokotno obremenitvijo (Hertzov stični tlak), strižno obremenitvijo (trenje med zobnimi boki zobnikov) in dodatno stično silo, ki je posledica elastohidrodinamičnih (EHD) pogojev mazanja. Za določitev širjenja utrujenostne razpoke od začetne do kritične dolžine, ko se delček materiala odlomi od površine in povzroči nastanek jamice, je uporabljen postopek J-integrala v okviru metode končnih elementov. Primerjava računskih in eksperimentalnih rezultatov kaže, daje predstavljeni model primeren za spremljanje širjenja površinske utrujenostne razpoke pri stični obremenitvi in ga kot takega lahko uporabimo pri napovedovanju pojava jamičenja na stično obremenjenih elementih, kakor so zobniki, ležaji, kolesa itn.

V nalogi smo preverili skladnost preizkusov in obstoječega preizkuševališča s standardi. V analizi smo ugotovili, da preizkusi in preizkuševališče niso skladni z veljavnimi standardi, ki za to področje veljajo v Evropski uniji. Les uvrščamo med inženirske materiale, zato je preizkušanje njegovih lastnosti pomembno, ker na ta način pridobimo pravilne podatke o fizikalnih in mehanskih lastnostih. Ugotovili smo, da nadgradnja preizkuševališča ni smiselna, zato smo izdelali projekt novega preizkuševališča in določili potek preizkusa ter pripravo vzorcev za določanje upogibne trdnosti. Projekt novega preizkuševališče smo vsebinsko razdelili na dva dela. Prvi del vsebuje konstruiranje in dimenzioniranje. Sestavnim delom smo določili obliko, dimenzijo in naredili trdnostni preračun. Pripravili smo sestavni načrt preizkuševališča, ki je osnova za pripravo delavniških risb sestavnih delov. V drugem delu smo določili pogon, merilno krmilni sistem in programsko opremo za zajem podatkov. Za pogon smo izbrali servo motor z ustreznim navorom. Za merjenje sile smo uporabili dinamometer. Izhodne podatke dinamometra v obliki električne veličine, smo preko ojačevalnika in merilne kartice s pomočjo programske opreme LabView zajemali na osebnem računalniku v obliki elektronskih preglednic. S tem omogočimo njihovo nadaljnjo obdelavo. Izdelali smo stroškovnik materialov. S tem smo želeli ugotoviti ali je smiselno preizkuševališče kupiti na trgu. In the experiment we checked the compatibility of the tests and the existing testing station with the standards. In the analysis, we found that the tests and the test station were not compatible with the standards that apply in this field. Wood is classified as an engineering material in the European Union and thus testing of its properties is important, as we can then obtain the correct data on its physical and mechanical properties. We thus aimed to develop a new testing machine and determined the course of the test and the preparation of samples for determining the bending strength. The project was divided into two parts. The first was construction and sizing of the machine. In this we determined the shape, dimensions and for some parts the solidity of the machine. We have prepared a blueprint of the testing machine and a plan of parts. In the second part of the project, we determined the drive, the measurement system and the software used for data acquisition. For the drive we selected a servo motor with a suitable torque. To measure the force, we chose a dynamometer. The output data of the dynamometer is in the form of an electric signal, which is captured on a personal computer in the form of electronic spreadsheets, which allows for further processing. We made a price analysis and compared the price of our proposed system with that of the testing stations on the market, as we wanted to know if it would be better to buy a new test station that is currently commercially available.

CNC stroji so danes tako v lesni industriji kot pri obrtnikih postali osnovni obdelovalni stroji. Z njimi močno povečamo storilnost in kakovost izdelkov. CNC stroje relativno enostavno programiramo s CAD/CAM programsko opremo, če pa so stroji opremljeni z avtomatsko izmenjavo orodij, lahko stroj enostavno, varno in hitro opravi več operacij. Razvoj CNC strojev je hiter, saj proizvajalci sledijo novostim na področju elektronike in informacijskih tehnologij. Manjšim obrtnikom predstavlja nakup novega sodobnega CNC stroja velik strošek. V nalogi je predstavljena nadgradnja malo rabljenega 3 osnega CNC stroja z zastarelo krmilno elektroniko v sodoben 3 osni CNC stroj z avtomatsko izmenjavo orodij. V prvem delu je predstavljena mehanska nadgradnja stroja z obdelovalnim agregatom z avtomatsko izmenjavo orodij in vrtalno enoto. Zasnovan in izdelan je bil nosilni vmesnik obdelovalnega agregata, ki je bil preverjen z napetostno deformacijsko analizo z metodo končnih elementov v računalniškem programu Autodesk Fusion 360. V drugem delu pa je predstavljena posodobitev krmilne enote stroja s strojno opremo Hyper Cut in Mach 3 CNC krmilnikom, ter programiranje makrojev za avtomatsko menjavo orodij. Nadgrajeni stroj izpolnjuje vse postavljene zahteve in se uporablja v obrtniški delavnici. CNC machines have become fundamental machine tools in wood industry and also in craft industry. By using them, it is possible to increase productivity and the quality of products. They are fairly easy to be programmed, using CAD/CAM software if they are equipped with the automatic tool exchange, the machines can perform several operations simply, safely and quickly. The development of machine tools is rapid as producers keep up with novelties in the field of electronic and information technologies. The purchase of a new modern CNC machine represents a large expense for smaller craftsmen. In the thesis, the upgrade of a 3 axes CNC machine not much used and with obsolete control electronics to a modern 3-axes CNC machine with the automatic tool exchange is presented. In the first part, the mechanical machine upgrade with a machining unit with the automatic tool exchange and a drilling unit is described. The supportive interface of the machining unit was conceived and produced it was checked on the basis of stress and deformation analysis with the finite element method, using the Autodesk Fusion 360 software. In the second part, the control unit upgrade with Hyper Cut hardware and Mach 3 CNC software and macro programming for the automatic tool exchange are presented. The upgraded machine fulfils all the requirements and is used in a workshop.

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.