Methode zur Optimierung der Zahnfußtragfähigkeit einsatzgehärteter Zahnräder

Translated title of the contribution: Method for the optimization of the tooth root load carrying capacity of case hardened gear wheels

Christoph Haberer

Research output: ThesisDoctoral Thesis


The automobile industry always has the ambition to reduce the weight to power ratio of the gear train through innovative development and to simultaneously increase the cost effectiveness of the production line. The cyclic loading on the gear wheels in operation can lead to complex damage mechanisms. The damage mechanism tooth root fracture is of high importance because it directly limits the lifetime of the gear train in operation and also the kinematic function of the power transmission. Therefore the aim of the present thesis is to evaluate the local tooth root load carrying capacity of modern automotive gears, to optimize the shape of the tooth root, to characterise the influence of alternative forming manufacturing technologies and to assess the relevance of the case hardening depth on the local load carrying capacity. For this purpose a finite element simulation method for differentially non describable tooth root geometries was developed, with which it is possible, to simulate the engagement of a gear pair based on the real geometry and to display the time and position dependent stress distributions. Furthermore the simulation method builds the basis for transferring the results of the component tests and for the shape optimizations of the tooth root fillet. For the evaluation of the influence of new forming technologies orbital forging for hypoid gears, cold extrusion for planet gear wheels and rotary swaging for gear shafts on the local load carrying capacity of gear components extensive analyses on the material and on the fatigue behavior of specimen and components were performed. As part of the thesis new test procedures for life fatigue tests on real hypoid gear wheels were developed. Therefore several influences on the local tooth root load carrying capacity can be analysed and assessed in reference tests. A comparison of the local tooth root load carrying capacity already shows a very good applicability for the new forming technologies compared to the common milling processes. As part of the cyclic tests on rotating bending specimen, the influence of the case hardening depth on the local fatigue behaviour is examined. A model based on estimating the local endurance limit is presented and used for calculating the local fatigue limit of the case hardened layer. The results and methods gained from this thesis are an important step for the development of new gear parts. They help to optimize the load carrying capacity of components and also show the potential of alternative forming manufacturing technologies.
Translated title of the contributionMethod for the optimization of the tooth root load carrying capacity of case hardened gear wheels
Original languageGerman
  • Eichlseder, Wilfried, Assessor A (internal)
  • Affenzeller, Josef, Assessor B (external), External person
Publication statusPublished - 2010

Bibliographical note

no embargo


  • tooth root load carrying capacity
  • gear wheel
  • optimization

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