Influence of Tip Relief Profile Modification on Involute Spur Gear Stress

This paper deals with the effects of linear tip profile modification on the stress of tooth root and tooth flank of involute spur gears. An increase in the tooth flank stress due to the tip profile modification is potentially hazardous because there is an increased risk of micro pitting initiation. The required magnitude of tip relief profile modification depends on the magnitude of tooth elastic deformation that needs to be compensated for. In order to study the effects of linear tip profile modification on gear stress, two matching finite element models of involute spur gear pairs have been created, and tip relief profile modification has been applied to one pair. Tooth root and tooth flank stresses in both gear pairs have been compared in order to establish the effect of tip relief profile modification on gear stress

Some Considerations About Engineering Ethics

Engineers and scientists today bear the responsibility for the quality of life of future generations more than ever before. Engineering is an important and learned profession, which has a direct and vital impact on the quality of life for all people. The decisions and actions of engineers have a profound impact on the world we live in, and society at large. Accordingly, engineers must provide their services on the basis of honesty, impartiality, fairness, and equity, and must be dedicated to the protection of public health, safety, and welfare. Engineering failures are often found to stem from deficiencies in engineering ethics, and engineers are responsible for their actions to the engineering community, to political and societal institutions as well as to their employers, customers, and technology users. Unfortunately, we are frequently witnesses to more and more negative consequences of scientific and technological advances markedly caused by neglect of moral principles in human activities. Engineers have to be aware of ethics in decision-making during their professional practice and they should not think only about profit, because when things go wrong, there is always an ethical dimension

Genetic algorithm based optimisation of conveyor belt material cross section area

Trakasti transporteri se koriste za brzi i ekonomični transport velikih količina rasutog materijala na kratkim do srednjim udaljenostima, npr. za transport od mjesta iskopa do pogona za pročišćavanje ili mjesta pretovara. Kapacitet trakastog transportera ovisi o više vrijednosti, poput poprečnog presjeka materijala na transportnoj traci, brzine kretanja trake, gustoći transportiranog materijala te kuta nasipanja materijala. Poprečni presjek materijala ima najveći utjecaj na kapacitet trakastog transportera pa su uspoređeni poprečni presjeci za komercijalno dobavljive valjne slogove s poprečnim presjecima valjnih slogova odgovarajuće geometrije, no optimiziranih putem genetskog algoritma. Provedena je i usporedba s dubokim polukružnim valjnim slogom putem radne širine trake zbog bitnog povećanja poprečnog presjeka materijala kod tog valjnog sloga u odnosu na jednovaljčane, dvovaljčane, trovaljčane i peterovaljčane slogove.Belt conveyors are used to transport large quantities of bulk material quickly and economically over short to medium distances, e.g. for transfer from the extraction point to a processing station or shipment point. The load capacity of a belt conveyor depends on several factors, such as the trough cross section of the conveyor belt, belt speed, material density and material angle of surcharge. The load capacity of belt conveyors is mostly determined by the trough cross section, so cross sections of commercially available troughs have been compared to cross sections of matching roller layout, but optimised via a genetic algorithm. A comparison has also been made with deep semi-circular troughs, due to a significant increase in material cross section when compared to flat, v-shaped, trapezoidal and polygonal troughs

SOME CONSIDERATIONS ON THE LOAD CAPACITY OF INTERNAL HIGH TRANSVERSE CONTACT RATIO INVOLUTE GEARING

Evolventni zupčanici s velikim stupnjem prekrivanja profila (VPP) nude određene prednosti u odnosu na standardno evolventno ozubljenje, poput povećane nosivosti, jednoličnijeg prijenosa okretnog momenta, smanjenog šuma zahvata te povećane trajnosti. Kako je unutarnje ozubljenje važno za konstrukciju mjenjača brzina i mehanizama za okretanje dizalica, analizirana je nosivost unutarnjeg VPP ozubljenja te je istražen problem raspodjele opterećenja kod unutarnjeg VPP ozubljenja. Na temelju rezultata ove analize izračunato je naprezanje u korijenu zuba i Hertzovo naprezanje uzduž zahvatnog puta zupčanika. Najveće naprezanje uzduž zahvatnog puta kao referentna vrijednost uspoređeno je s vrijednostima naprezanja zuba izračunatim prema standardu DIN 3990, čime se pokazalo da proračun prema DIN 3990 daje vrijednosti koje poprilično odstupaju od izračunatih, iako je pogreška na strani sigurnosti.High transverse contact ratio (HCR) involute gears present advantages in relation to standard involute gears, such as improved load capacity, smoother torque transfer, reduced meshing noise and extended gear life. As internal gearing is important for the design of gearboxes and crane rotation mechanisms, the load capacity of internal HCR gearing has been analyzed and the problem of load distribution in internal HCR gearing researched. Based on the results of this analysis, tooth root and Hertzian stresses along the path of contact have been calculated. The maximum stresses along the path of contact were used as a reference value and compared to results of tooth stress calculations according to the DIN 3990 standard. Research has shown that the calculation according to DIN 3990 provides rather inaccurate results for internal HCR gearing, although with higher safety factors

THE SELECTION OF OPTIMAL REVERSIBLE TWO-SPEED PLANETARY GEAR TRAINS FOR MACHINE TOOL GEARBOXES

The application of multi-criteria optimization to two-carrier two-speed planetary gear trains is outlined in this paper. In order to determine the mathematical model of multi-criteria optimization variables, the objective functions and conditions must be determined first. Two-carrier two-speed planetary gear trains with brakes on coupled shafts are analyzed in this paper. The mathematical model covers the determination of the set of the Pareto optimal solutions as well as the method for selecting an optimal solution from this set. A numerical example is provided to illustrate the procedure in which the optimal two-speed planetary gear train is selected and defined by design parameters

Design proposal for a hydrostatic city bus transmission

A city bus is probably one of the harshest operating environments for a vehicle transmission. The average operating speed is low, while frequent stops require swift acceleration from standstill. The options for the placement of transmission and suspension components are highly restricted as the passenger space must be as large as possible, with a completely flat vehicle floor for ease of passenger movement, and ground clearance is kept as low as possible to facilitate the entry and exit of passengers. Therefore, it is common to place the engine and gearbox at the rear end, and power is transmitted to the wheels via a propeller shaft and a rigid rear axle, effectively ruling out any completely level floor design. An improvement is offered by the hydrostatic transmission, using high pressure fluid for the power transmisison. The fluid flows from a pump to a motor via relatively small diameter pipes, enabling the design of a completely level floor. The hydrostatic transmission offers continuous variation of transmission ratios and the possibility that hydraulic motors can be placed very close to the wheels, thus enabling all- wheel drive and increased passenger space. Finally, hydraulic accumulators can be added to a hydrostatic transmission in order to recover and reuse kinetic energy which would otherwise be lost by braking

Design proposal for a hydrostatic city bus transmission

A city bus is probably one of the harshest operating environments for a vehicle transmission. The average operating speed is low, while frequent stops require swift acceleration from standstill. The options for the placement of transmission and suspension components are highly restricted as the passenger space must be as large as possible, with a completely flat vehicle floor for ease of passenger movement, and ground clearance is kept as low as possible to facilitate the entry and exit of passengers. Therefore, it is common to place the engine and gearbox at the rear end, and power is transmitted to the wheels via a propeller shaft and a rigid rear axle, effectively ruling out any completely level floor design. An improvement is offered by the hydrostatic transmission, using high pressure fluid for the power transmisison. The fluid flows from a pump to a motor via relatively small diameter pipes, enabling the design of a completely level floor. The hydrostatic transmission offers continuous variation of transmission ratios and the possibility that hydraulic motors can be placed very close to the wheels, thus enabling all- wheel drive and increased passenger space. Finally, hydraulic accumulators can be added to a hydrostatic transmission in order to recover and reuse kinetic energy which would otherwise be lost by braking

APPLICATIONS OF STROBOSCOPES

Stroboskopi su uređaji za promatranje predmeta u brzom periodičnom gibanju stvaranjem optičke iluzije zaustavljenog ili usporenog predmeta, a oslanja se na tromost ljudskog oka kako bi se postigao željeni učinak. Osim za promatranje predmeta u brzom gibanju stroboskopi se primjenjuju na mnoge raznovrsne načine: od ispitivanja strojeva do podešavanja broja okretaja gramofona.Stroboscopes are devices for observation of cyclically moving high-speed objects by creating an optical illusion of stopped or slowed motion. The stroboscopic effect relies on the persistence of vision in the human eye to achieve the desired effect. In addition to the observation of fast moving objects, stroboscopes can be used in a variety of applications ranging from machinery inspection to turntable pitch control

Mjerenje i analiza vibracija energetskih transformatora s ciljem smanjenja buke

Karakterizacija dinamičkog odziva je ključna pri analizi buke energetskih transformatora te određivanju mjera za minimizaciju buke. Nastajanje buke je uvjetovano međudjelovanjem uzbude jezgre i namotaja te prijenosom uzbude fluidom za hlađenje do oplate. Taj kompleksni mehanizam može se analizirati jedino naprednim numeričkim modelima temeljenim na mjerenjima. U ovom se radu, kao izvanredan primjer prijenosa znanja, opisuje napredna vremenska i frekvencijska analiza vibracijskih učinaka temeljena na pažljivom planiranju eksperimenata DoE metodama te opsežnim eksperimentalnim mjerenjima dinamičkog odziva oplate energetskog transformatora tvrtke Končar D&ST d.d. provedenima koristeći beskontaktnu lasersku Doppler interferometrijsku metodu. Provedena analiza stvara preduvjete za razvoj modela koji će omogućiti unapređenje konstrukcije analiziranih kompleksnih sustava s ciljem smanjenja buke te daljnjeg zadovoljavanja sve strožih međunarodnih normi za energetske transformatore

Mjerenje i analiza vibracija energetskih transformatora s ciljem smanjenja buke

Karakterizacija dinamičkog odziva je ključna pri analizi buke energetskih transformatora te određivanju mjera za minimizaciju buke. Nastajanje buke je uvjetovano međudjelovanjem uzbude jezgre i namotaja te prijenosom uzbude fluidom za hlađenje do oplate. Taj kompleksni mehanizam može se analizirati jedino naprednim numeričkim modelima temeljenim na mjerenjima. U ovom se radu, kao izvanredan primjer prijenosa znanja, opisuje napredna vremenska i frekvencijska analiza vibracijskih učinaka temeljena na pažljivom planiranju eksperimenata DoE metodama te opsežnim eksperimentalnim mjerenjima dinamičkog odziva oplate energetskog transformatora tvrtke Končar D&ST d.d. provedenima koristeći beskontaktnu lasersku Doppler interferometrijsku metodu. Provedena analiza stvara preduvjete za razvoj modela koji će omogućiti unapređenje konstrukcije analiziranih kompleksnih sustava s ciljem smanjenja buke te daljnjeg zadovoljavanja sve strožih međunarodnih normi za energetske transformatore