Static and dynamic study for the prediction of contact fatigue on spur gear teeth

The main objective of this article is to study the influence of static and dynamic behavior on the occurrence of contact fatigue on spur gear tooth. For this end, a dynamic model of geared transmission in one degree of freedom, with Crossland criterion, are used. The motion equation is analyzed step par step in the time in order to determine the dynamic load in all contact points on teeth profile. In this way, the time-varying dynamic loads on tooth flanks are determined and the subsurface stress components can be derived from the classic Hertzian theory.

Design a new cutting system for portable plants-eater

A new system was designed in portable plants-eater to improve the performance and productivity and for using it in the harsh environment containing like-cane dense brushes with high efficiency, quality and lowest power requirement and to harvest some crops are grown in small areas. The new system includes three types: link chain, straight blades chain and oblique blades chain, each chain is fixed on central aluminum disk. the three chains were tested on tensile, the results were satisfactory. The cutters was tested in the field on four types of stalk Wheat, Yellow Maize, Sorghum Helpenese and imperata cylindrical. Cutting force, productivity, fuel consumption, power requirement was calculated with deferent rotation speeds. The straight blades chain has the best cutting quality and lowest energy requirement on maize and sorghum halepense, the oblique blades chain was better on wheat and imperata cylindrical. The greatest values of energy requirement and cutting forces appeared with link chain cutter-head. In general, these cutter-heads are useable in weed-eater with higher efficiency than the old designs.

Modeling of the fatigue crack initiation period on the helical gears

A computational model of the fatigue crack initiation period on the helical gears ,with consideration of the heat treatment by carburization and friction effects, is presented. In order to calculate the number of stress cycles required for the appearance of the initial cracks, and study the influence of dynamic behavior. For this end, a dynamic model of gear with two freedom degrees in torsion developed in Matlab and fatigue criteria are used. The computational results are compared with those obtained using strain- life method. The obtained results show that appearance of initial fatigue crack depends strongly on the friction coefficient between the surfaces, heat treatment, and on the dynamic load.