The lower sheave assembly is a series of elements that make the whole, over which load is transferred from the hooks on the crane. Taking into account responsibility and consequences of these elements (injury of people and economic damage from the fall of cargo) that are possible in the case of a collapse of the element or assembly as a whole it is quite justifiable request for a detailed scrutiny of their validity and security. Classical (conventional) methods include the making of necessary number of prototype elements, which after computation checks are additionaly analysed what includes certain economic and time costs. This paper gives an overview of geometrical modeling of parts and the formation of the lower sheave assembly in CAD/CAE software CATIA V5. Engineering (stress deformation) analysis of carrier sheet metal is made. The aim is to present the methods that provide additional security at the planning and contribute to faster and cheaper development of new products.

The work presented here provides a mathematical model for solving the problem of lubrication (calculation of efficiency) of worm gear drives, including a description of the engagement geometry and comprehensive modeling of the worm gear drive lubrication process based on the physical characteristics of the lubricant and the applied materials of contact bodies. The established mathematical model is based on the thermo-elasto-hydrodynamic (TEHD) lubrication theory that has proven to be successful in the analysis of journal bearings. The solution of the problem on hand by analyzing the loss of power in gearing, i.e. by analyzing the efficiency ratio of the gear, is basically reduced to the problem of mathematical modeling of local friction coefficients in the oil film along the contact line of the gears. The applicability of TEHD lubrication and the developed computer program were verified by comparing numerical results with experimental values obtained on a test bench using a real worm gear.

U primjeni masinskih elemenata kao sto su zupcanici i kotrljaj n i ležajevi ostvareni kontakti rade u specificnim režimima podmazivanja. Projektovani kontakti masina sa zahtjevnim namjenama obicno rade u razlicitim radnim uslovima, a neki od njih u podrucju mjesovitog podmazivanja. U cilju optimiranja kontakata analizom koeficijenta trenja i vijeka upotrebe neophodno je razviti TEHD (termo-elasto-hidrodinamicki) model za mjesovito podmazivanje. Ovaj model baziran je na cinjenici da se ukupno opterecenje kontakta prenosi dijelom preko pritiska u uljnom filmu i dijelom preko kontakta cvrstih tijela a sila trenja je suma sile trenja kontakta cvrstih tijela i sile trenja hidrodinmiicke komponente. Za kompletno rjesenje TEHD modela mjesovitog podmazivanja neophodno je poznavanje koeficijenta trenja cvrstih tijela preko vrhova neravnina a koji se mora odrediti eksperimentalnim putem. Ovaj rad daje provedene eksperimente za određivanje koeficijenta trenja cvrstih tijela.

U slucajevima mnogih zupcastih parova, ležajeva i kontakata, sile se prenose kroz tanke, kontinualne uljne filmove, koji odvajaju dva elementa u kontaktu. Objekti u kontaktu normalno su izloženi trenju i trosenju, koji mogu biti efektivno reducirani koristenjem maziva. Za kontaktna opterecenja sa malim geometrijskim konformitetom kao sto su zupcanici, kotrljajni ležejevi zbog visokih pritisaka koristi se elasto-hidrodinamicko podmazivanje. U slucaju EHD podmazivanja elasticne deformacije kontaktnih elemenata te porast fluidnog viskoziteta sa pritiskom veoma su znacajni i ne mogu biti ignorisani. Posto deformacije rezultiraju promjenom geometrije uljnog filma koji dalje determinise raspodjelu pritiska, EHD matematicki model mora istovremeno zadovoljiti složene integralne jednacine elasticnosti kao i Reynoldsove diferencijalne jednacine podmazivanja. Ovaj rad daje opis jednacina kod EHD podmazivanja i njihovo rjesavanje primjenom Njutnovog metoda direktnih utjecaja.