Influence of base material,tempered condition and hardening pattern on the residual stress profile of induction hardened gears

Forschung im Ingenieurwesen - This paper discusses influences of the base material, pre-heat treatment and hardening pattern on the residual stresses of induction hardened gears with module 2 and...     

Alternative microstructures and their influence on mechanical properties of case-hardened gears

Forschung im Ingenieurwesen - Case hardening is one of the most common heat treatment processes for highly loaded shafts and gears. Due to numerous investigations, a microstructure...     

Verkürzte Lebensdauertests von Zahnradgetrieben unter Lastkollektivbeanspruchung

Forschung im Ingenieurwesen - Im Rahmen dieses Beitrags wird ein Vorgehensmodell zur Planung und Durchführung von verkürzten Lebensdauertests bei Zahnradgetrieben vorgestellt, um einen...     

Flank load carrying capacity of oil-lubricated high performance plastic gears

Forschung im Ingenieurwesen - Plastic gears for power transmitting gearboxes are gaining more and more importance. Operation under oil-lubricated conditions and the use of high-performance...     

Fracture analysis of fisheye failures in the tooth root fillet of high-strength gears made out of ultra-clean gear steels

Forschung im Ingenieurwesen - In shot-peened components, failures can be caused by a crack initiation below the surface at a non-metallic inclusion in the steel matrix. This...     

Investigation on the flank surface durability of gears with increased pressure angle

Within a funded research project (reference number 0325244C, BMWi – Federal Ministry for Economic Affairs and Energy of Germany), the load-carrying capacity of alternative involute gears was investigated. To find qualified variations for use in gear drives, increased pressure angles (α_n > 20°) and/or asymmetric tooth shapes (α_n < 20° and α_n > 20°) have been examined experimentally. Optimization goals were the power to weight ratio of the transmission and the power density in the drive train.In this report gears with reference tooth shape (α_n = 20°) as well as gears with modified tooth shape (α_n = 28°) are discussed with focus on the load carrying capacity of the tooth flank with special regard to the damage mechanisms pitting, micro-pitting and scuffing. The results of experimental and test accompanying studies are shown. They allow a direct comparison between standard and special gears as well as a classification in context of the actual state of knowledge.     

On the determination of the bending fatigue strength in and above the very high cycle fatigue regime of shot-peened gears

Demands on modern gearboxes are constantly increasing, for example to comply with lightweight design goals or new CO₂ thresholds. Normally, to increase performance requires making gearboxes and powertrains more robust. However, this increases the weight of a standard gearbox. The two trends therefore seem contradictory. To satisfy both of these goals, gears in gearboxes can be shot-peened to introduce high compressive residual stresses and improve their bending fatigue strength. To determine a gear’s tooth root bending fatigue strength, experiments are conducted up to a defined number of load cycles in the high cycle fatigue range. However, investigations of shot-peened gears have revealed tooth root fracture damage initiated at non-metallic inclusions in and above the very high cycle fatigue range. This means that a further reduction in bending load carrying capacity has to be expected at higher load cycles, something which is not covered under current standard testing conditions. The question is whether there is a significant decrease in the bending load carrying capacity and, also, if pulsating tests conducted at higher load cycles—or even tests on the FZG back-to-back test rig—are necessary to determine a proper endurance fatigue limit for shot-peened gears. This paper examines these questions.

     

Investigations into non-metallic inclusion crack area characteristics relevant for tooth root fracture damages of case carburised and shot-peened high strength gears of different sizes made of high-quality steels

Forschung im Ingenieurwesen - Case carburised and shot-peened high-strength gears can fail by tooth root bending failures in the very high cycle fatigue range of the S‑N-curve due to crack...     

Theoretical investigations of the load distribution of small sized crown gear sets different material pairings

Forschung im Ingenieurwesen - An analytical approach for the calculation of the load distribution on the flank of crown gears, based on the theory according Placzek, is proposed. The teeth of the...