1. Konstruiranje strojev in naprav : učbenikJanez Kramberger, Stanislav Pehan, Srečko Glodež, 2023, higher education textbook Abstract: Učbenik celovito predstavlja sodobne sistemske postopke pri konstruiranju strojev in naprav. Osnovni namen učbenika je najprej na preprost način prikazati napotke, s pomočjo katerih je mogoče izpolniti predvsem splošne zahteve glede varnosti strojev, ki jih na tem področju postavljata evropska in slovenska zakonodaja. V nadaljevanju so potem podane nekatere smernice za ergonomsko načrtovanje strojev. Osrednji del učbenika predstavlja obravnava nevarnosti in ocenjevanja tveganja v povezavi z načrtovanjem in uporabo strojev, podrobno pa je opisana tudi zahtevna problematika varnostne tehnike strojev. Na koncu je na kratko opisan osnovni vpliv strojev na okolje. Učbenik je v osnovi namenjen študentom strojništva pri predmetu Konstruiranje strojev in naprav, uporaben pa je tudi pri predmetih sorodnih vsebin. V učbeniku je vključenih precej praktičnih zgledov, zato predstavlja koristen pripomoček tudi načrtovalcem in konstruktorjem, ki se v vsakdanji praksi ukvarjajo s problematiko načrtovanja in varnostjo strojev.
E-knjiga dostopna le za študente Univerze v Mariboru, Fakultete za strojništvo.
Keywords: konstruiranje, stroji in naprave, tehniški predpisi in standardi, delovno okolje, ergonomija, nevarnosti in tveganja, varnostna tehnika
Published in DKUM: 18.07.2023; Views: 548; Downloads: 136
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2. Numerično simuliranje površinske utrujenostne razpoke na zobeh zobnikovGorazd Fajdiga, Jože Flašker, Srečko Glodež, Zoran Ren, 2000, original scientific article Abstract: 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.
Keywords: strojni elementi, zobniška gonila, lomna mehanika, utrujanje, jamičenje, mazanje, kontaktni problemi, dotikalne površine
Published in DKUM: 10.07.2015; Views: 1554; Downloads: 65
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3. Numerical modelling of micro-pitting of gear teeth flanksGorazd Fajdiga, Jože Flašker, Srečko Glodež, Trevor K. Hellen, 2003, original scientific article Abstract: A two-dimensional computational model for simulation of contact fatigue of gear teeth flanks is presented. In the model, it is assumed that the initial crack of length 0.015 mm is initiated at the surface due to previous mechanical or heat treatment of the material as well as a consequence of the running in process. The discretized model with the initial crack is then subjected to normal contact pressure, which takes into account the elasto-hydro-dynamic (EHD) lubrication conditions, and tangential loading due to friction between contacting surfaces. The model also considers the moving contact of gear flanks, fluid trapped in the crack and residual stresses due to heat treatment of the material on crack propagation. The virtual crack extension (VCE) method, implemented in the finite element method, is then usedfor simulating the fatigue crack growth from the initial crack up to the formation of the surface pit. The computational results show that the initial surface crack of length 15 m and the considered boundary conditions lead to the appearance of very small surface pits, which can be termed as micro-pitting on gear teeth flanks. The numerical results correspond well withavailable experimental data.
Keywords: machine elements, gearing, fracture mechanics, numerical analysis, micro pitting, pitting simulation, matematical model, fatigue, contact mechanics, crack propagation
Published in DKUM: 01.06.2012; Views: 2660; Downloads: 0 |
4. The influence of different parameters on surface pitting of contacting mechanical elementsGorazd Fajdiga, Jože Flašker, Srečko Glodež, 2004, original scientific article Abstract: The paper describes a general computational model for simulation of surface pitting of mechanical elements subjected to contact loading conditions. In the model it is assumed that the initial crack of length 0.015 mm is initiated at the contacting surfaces due to previously thermal, mechanical treatment of the material or running in process. The discretised model with the initial crack is then subjected to normal contact pressure, which takes into account the EHD lubrication conditions and tangential loading due to friction between contacting surfaces. The model accounts also for the influence of fluid trapped in the crack on crack prppagation. The virtual crack extension VCE method within FEM analysis is then used for 2 dimensional simulation of fatigue crack propagation from the initial crack up to the formation of the surface pit. The pit shapes and relationships between the stress intensity factor and crack length are determined for various combinations of contacting surface curvatures and loadings. The comparison of computational and available experimental results shows that the proposed model reliably simulates the surface fatigue crack growth under contact loading and can be used for computational predictions of surface pitting for various contacting mechanical elements.
Keywords: machine elements, gears, contact problems, pitting, fatigue crack growth, simulation, model
Published in DKUM: 01.06.2012; Views: 2182; Downloads: 111
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5. Pitting formation due to surface and subsurface initiated fatigue crack growth in contacting mechanical elementsGorazd Fajdiga, Srečko Glodež, Janez Kramar, 2007, original scientific article Abstract: A computational model for simulation of surface and subsurface initiated fatigue crack growth due to contact loading is presented. The model is based on fracture mechanics theory where the required materials properties are obtained from common fatigue tests. For computational simulations an equivalent model of two contacting cylinders is used instead of simulating theactual contact of mechanical elements. The discretised model with the initial crack on or under the surface is then subjected to normal contact pressure, which takes into account the EHD-lubrication conditions, and tangential loading due to friction between contacting surfaces. The model considers also the moving contact of mechanical elements and for the surface initiated crack also the fluid trapped in the crack. The virtual crack extension method, implemented in the finite element method is then used for simulating the fatigue crack growth from the initial crack up to the formationof the surface pit. The numerical results correspond well with available experimental data. The described model can be used for simulation ofpitting phenomenon of contacting mechanical elements like gears, bearings, wheels, etc.
Keywords: fracture mechnaics, machine elements, gears, contact fatigue, pitting, subsurface crack initiation, computational analysis
Published in DKUM: 31.05.2012; Views: 2353; Downloads: 114
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