Wälzfestigkeit erodierter Oberflächen im Zwei-Scheiben-Zahnradanalogieversuch

Due to advances in power electronics and high-frequency process control, the technology of electrical discharge machining (EDM) has received a decisive technological boost in the last two decades to increase the achievable removal and cutting rates and to minimize the thermally influenced surface zone. At the same time, wire electrical discharge machining in particular has always been characterized by high achievable geometrical accuracy. In addition, a cup-shaped surface structure is formed in EDM as a result of the individual discharge points, which can offer targeted optimization potential with regard to tribological properties in rolling-sliding contacts. For this reason, the objective of this report is the knowledge of the contact fatigue strength of eroded surfaces in comparison to a ground reference with a focus on tribological contact conditions typical for gears.

Contact Fatigue Strength of Austempered Ductile Iron (ADI) in Gear Applications

Austempered Ductile Iron (ADI) is widely implemented to achieve lightweight and optimized components in power transmissions (e.g., internal gear in planetary stages), by substituting steel castings or a combination of Ductile Iron and steel-assembled structures. In this paper, the contact fatigue of two ADI grades (ADI J/S900-8; ADI J/S1200-3) is investigated by disk-on-disk tests. The disk-on-disk contact is an analogy model of the tooth contact and represents the tribological conditions at a specific point on the path of contact. The experimental results cover the endurance limit as well as the short time fatigue behavior for both ADI variants. In addition, the pitting characteristics and microstructural changes are analyzed in order to get a further understanding of the fatigue behavior of ADI.

Analytical Calculation of the Tooth Surface Contact Stress of Cylindrical Gear with Variable Hyperbolic Circular-Arc-Tooth-Trace

In order to theoretically research the tooth surface maximum contact stress of a Cylindrical Gear with Variable Hyperbolic Circular-Arc-Tooth-Trace (VH-CATT), the computing formula of maximum contact stress of VH-CATT cylindrical gear is investigated according to Hertz formula in this paper. Insufficient contact fatigue strength will lead to pitting corrosion, plastic deformation of tooth surface and other damages. Therefore, the maximum contact stress of tooth surface must be carried out. The contact stress calculation formula is particularly considering the effect of normal force, total carrying length, synthetical curvature radius, and position angle. The present work establishes analytical solutions to research the effect of different parameters for the contact stress of VH-CATT cylindrical gear incorporating elastic deformation on the tooth surface, and which have shown that the different module, transmission ratio, pressure angle, tooth width, and the cutter head radius have a crucial effect on the contact stress and contact ellipse of VH-CATT cylindrical gear along the tooth width direction. Moreover, a finite element analysis is carried out to verify the correctness of the theoretical computing formula of contact stress of VH-CATT cylindrical gear. By contrast with the theoretical calculated value and the stress value of finite element analysis, its error is very small. It is indicated that the derived formula of contact fatigue strength of VH-CATT cylindrical gear has high accuracy and can accurately reflect the real contact stress value of tooth surface, which is beneficial for research on tooth break reduction, pitting, wear resistance and fatigue life improvement of the VH-CATT cylindrical gear. The study results also have a certain reference value for the design and check calculation of the VH-CATT cylindrical gear.

Current state of problem in wheel pair flange damages and methods for decrease of their wear and contact fatigue

Within the limits of the paper there is formed a generalized idea of the problem of flange damages in railway wheel pairs, and also a comparative analysis of different methods application to increase wear-resistance and contact fatigue strength of surfaces mentined.