Comparison of Numerical Models for Gear Tooth Root Fatigue Assessments

2005 ◽  
Author(s):  
Damir T. Jelaska ◽  
Srdjan Podrug ◽  
Srecko Glodez
Keyword(s):  
Fatigue Crack ◽  
Service Life ◽  
Numerical Models ◽  
Experimental Testing ◽  
Gear Tooth ◽  
Moving Load ◽  
Fatigue Crack Initiation ◽  
Homogeneous Material ◽  
Force Model ◽  
Tooth Root

A several kinds of numerical models, including moving force model, for determination the service life of gears in regard to bending fatigue in a gear tooth root, is presented. The critical plane damage model, Socie and Bannantine [1], 1988, has been used to determine the number of stress cycles required for the fatigue crack initiation. This method determines also the initiated crack direction, what is good base for a further analyses of the crack propagation and the assessment of the total fatigue life. Finite element method and linear elastic fracture mechanics theories are then used for the further simulation of the fatigue crack growth under a moving load. Moving load produces a non-proportional load history in a gear’s tooth root. An approach that accounts for fatigue crack closure effects is developed to propagate crack under non-proportional load. Although some influences (non-homogeneous material, traveling of dislocations, etc.) were not taken into account in the computational simulations, the presented model seems to be very suitable for determination of service life of gears because numerical procedures used here are much faster and cheaper if compared with the experimental testing. The computational results are compared with other researchers’ numerical results and with service lives of real gears. The fatigue lives and crack paths determined in this paper exhibits a substantial agreement with experimental results and significant improvement compared with the existing numerical models.

Gear Tooth Root Fatigue Assessments by Estimating the Real Stress Cycle

2007 ◽  
Author(s):  
Damir T. Jelaska ◽  
Srdjan Podrug
Keyword(s):  
Fatigue Crack ◽  
Numerical Models ◽  
Gear Tooth ◽  
Moving Load ◽  
Force Model ◽  
Tooth Root ◽  
Stress Cycle ◽  
Linear Elastic ◽  
Moving Force ◽  
Elastic Fracture

A several kinds of numerical models, including moving force model, for determination the service life of gears in regard to bending fatigue in a gear tooth root, is presented. Finite element method and linear elastic fracture mechanics theories are then used for the further simulation of the fatigue crack growth under a moving load. Moving load produces a non-proportional load history in a gear’s tooth root. The corresponding stress cycle is obtained which enables more precise computing. An approach that accounts for fatigue crack closure effects is developed to propagate crack under non-proportional load. The computational results are compared with other researchers’ numerical results and with service lives of real gears. The fatigue lives and crack paths determined in this paper exhibits a substantial agreement with experimental results and significant improvement compared with the existing numerical models.

Numerical Modelling of the Crack Propagation Path at Gear Tooth Root

2003 ◽  
Author(s):  
Damir T. Jelaska ◽  
Srecko Glodez ◽  
Srdjan Podrug
Keyword(s):  
Fatigue Crack ◽  
Service Life ◽  
Crack Propagation ◽  
Experimental Testing ◽  
Gear Tooth ◽  
Fatigue Crack Initiation ◽  
Propagation Path ◽  
Tooth Root ◽  
Stress Cycles

A numerical model for determination of service life of gears in regard to bending fatigue in a gear tooth root is presented. The Coffin-Manson relationship is used to determine the number of stress cycles Ni required for the fatigue crack initiation, where it is assumed that the initial crack is located at the point of the largest stresses in a gear tooth root. The simply Paris equation is then used for the further simulation of the fatigue crack growth, where required material parameters have been determined previously by the appropriate test specimens. The functional relationship between the stress intensity factor and crack length K = f(a), which is needed for determination of the required number of loading cycles Np for a crack propagation from the initial to the critical length, is obtained numerically. The total number of stress cycles N for the final failure to occur is then a sum N = Ni + Np. Although some influences were not taken into account in the computational simulations, the presented model seems to be very suitable for determination of service life of gears because numerical procedures used here are much faster and cheaper if compared with the experimental testing.

A Numerical FEM Solution of Gear Root Stress in Offset Axial Mesh Misalignment

2013 ◽  
Vol 393 ◽  
pp. 375-380 ◽  
Author(s):  
Mohd Rizal Lias ◽  
Mokhtar Awang ◽  
T.V.V.L.N. Rao
Keyword(s):  
Stress Distribution ◽  
Critical Path ◽  
Gear Tooth ◽  
Contact Region ◽  
Moving Load ◽  
Spur Gear ◽  
Load Factor ◽  
Tooth Root ◽  
Load Model ◽  
The Impact

Gear offsets mesh in axial misalignment always leads to unevenness of load transferred contributing the impact of stress value and distribution along important critical path of the tooth root. Its happening due to overpress fitting when the gear is mounted onto the shaft as an interference hub fit. Current design methodology based on empirical model provide solution by approximation load factor fail to attributes in detailed regarding this phenomenon This paper determined to focus on this phenomenon in term of methodology to the stress distribution at the critical contact region of the tooth root of the gears. Pair of spur gear with real geometrical construction and condition was constructed with offset parameter. A moving load quasi-static model with a numerical FEM solution using ANSYS is presented with modification in loading variation. For verification, the stress value at the critical path of the tooth root is compared between standard high point single tooth contacts (HPSTC) loading to moving load model. As the result, a numerical FEM methodology to calculate the stress distribution of the gear tooth root in offset axial misalignment with moving load model approach is determined. The proposed method is also found reliable as an alternative solution to define an accurate load factor calculation compared to the approximation provided by the standard empirical procedure.

scholarly journals The Effect of the Microstructure and Defects on Crack Initiation in 316L Stainless Steel under Multiaxial High Cycle Fatigue

2014 ◽  
Vol 891-892 ◽  
pp. 815-820 ◽  
Author(s):  
Raphaël Guerchais ◽  
Franck Morel ◽  
Nicolas Saintier
Keyword(s):  
Stainless Steel ◽  
Fatigue Crack ◽  
Crack Initiation ◽  
High Cycle Fatigue ◽  
Driving Forces ◽  
Numerical Models ◽  
Fatigue Crack Initiation ◽  
Defect Size ◽  
Cycle Fatigue ◽  
Fatigue Crack Nucleation

The aim of this study is to analyse the influence of both the microstructure and defects on the high cycle fatigue behaviour of the 316L austenitic stainless steel, using finite element simulations of polycrystalline aggregates. High cycle fatigue tests have been conducted on this steel under uniaxial (push-pull) and multiaxial (combined in-phase tension and torsion) loading conditions, with both smooth specimens and specimens containing artificial semi-spherical surface defects. 2D numerical models, using a cubic elastic constitutive model, are created to determine the degree of heterogeneity of the local stress parameters as a function of the defect size. This has been done for one microstructure using several orientation sets generated from the initial texture of the material. The grains are explicitly modelled and the anisotropic behaviour of each FCC crystal is described by the generalized Hookes law with a cubic elasticity tensor. From the simulations carried out with different defect sizes and orientation sets that are representative of the real texture of the tested material, statistical information regarding mesoscopic mechanical fields provides useful insight into the microstructural dependence of the driving forces for fatigue crack nucleation at the mesoscopic scale (or the scale of individual grains). The results in terms of the stress fields and fatigue crack initiation conditions are determined at both the mesoscopic and macroscopic scales. The results from these FE models are used along with an original probabilistic mesomechanics approach to quantify the defect size effect. The resulting predictions, which are sensitive to the microstructure, include the probability distribution of the high cycle fatigue strength.

Evaluation of the Service Life of Gear in Regard to Bending Fatigue in a Gear Tooth Root

2003 ◽  
Vol 251-252 ◽  
pp. 297-302 ◽  
Author(s):  
Srečko Glodež ◽  
Boris Aberšek ◽  
Jože Flašker ◽  
Janez Kramberger
Keyword(s):  
Service Life ◽  
Gear Tooth ◽  
Tooth Root ◽  
Bending Fatigue

Crack Identification in Gear Tooth Root Using Adaptive Analysis

2007 ◽  
Vol 348-349 ◽  
pp. 697-700
Author(s):  
Ales Belsak ◽  
Jože Flašker
Keyword(s):  
Fatigue Crack ◽  
Signal Analysis ◽  
Gear Tooth ◽  
Crack Identification ◽  
Test Plant ◽  
Tooth Root ◽  
Dynamic Parameters ◽  
Unit Operation ◽  
Tooth Stiffness ◽  
Non Stationary Signal

Problems concerning gear unit operation can result from various typical damages and faults. A crack in the tooth root, which often leads to failure in gear unit operation, is the most undesirable damage caused to gear units. This article deals with fault analyses of gear units with real damages. A laboratory test plant has been prepared; it has been possible to identify certain damages by monitoring vibrations. In concern to a fatigue crack in the tooth root significant changes in tooth stiffness are more expressed. When other faults are present, however, other dynamic parameters prevail. Signal analysis has been performed also in concern to a non-stationary signal, using the adaptive transformation for signal analysis.

Analysis on Fatigue Crack Initiation and Fatigue Crack Propagation in a Gear

2018 ◽  
Vol 4 (7) ◽  
pp. 13
Author(s):  
Anand Mohan Singh ◽  
Mrs. Madhulata Sharma
Keyword(s):  
Fatigue Crack ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Failure Modes ◽  
Gear Tooth ◽  
Crack Depth ◽  
Dynamical Behavior ◽  
Fatigue Crack Initiation ◽  
Design Guidelines ◽  
Operating Conditions

An effective gear design balances strength, durability, reliability, size, weight and cost. Because of the advantage of gear, gearbox was used widely. But its fault also brought many losses of the production and society. It was necessary to research and analysis on the dynamical behavior of the gear system. The engineering structures may fail due to crack, which depends on the design and also on operating conditions in which it operates. It can be avoided by analyzing and understanding the manner in which it originates. It is necessary to develop design guidelines to prevent failure modes considering gear tooth fracture, by studying the crack propagation path in a gear. In variety of gear tooth geometry the crack propagation paths are predicted at various crack initiation location. The objective of this study was to follow the crack propagation in the tooth foot of a gear by the Finite Element Method (FEM). The study concludes with the analysis of available for standard gears, to highlight the different behavior in crack propagation. The influence of crack position and crack depth etc. on dynamic characteristics of gear has also been studied.

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