The Effect of Spur Gear Tribo-Dynamic Response on Pitting Crack Nucleation

2017 ◽  
Author(s):  
Sheng Li ◽  
Anusha Anisetti
Keyword(s):  
Crack Nucleation ◽  
Axial Stress ◽  
Contact Fatigue ◽  
Elastohydrodynamic Lubrication ◽  
Normal Pressure ◽  
Spur Gear ◽  
Dynamics Simulation ◽  
Dynamic Surface ◽  
Fatigue Crack Nucleation ◽  
Gear Mesh

This study investigates the role of the tribo-dynamic behavior in the contact fatigue crack nucleation for spur gears. To describe this fatigue phenomenon, a six-degree-of-freedom (DOF) lumped parameter dynamics formulation is coupled with a set of mixed elastohydrodynamic lubrication (EHL) governing equations. The former provides the dynamic tooth force to the EHL analysis, and the latter yields the gear mesh damping as well as the friction excitations that are required in the gear dynamics simulation. The converged tribo-dynamic surface normal pressure and tangential shear are then used to determine the multi-axial stress fields using the potential theory based closed-form stress formulation for half space. Lastly, the stress means and amplitudes are implemented in a multi-axial fatigue criterion to assess the fatigue damage.

Research on Influence of Intertooth Space Confriction to Transmission Efficiency under EHL

2012 ◽  
Vol 605-607 ◽  
pp. 1158-1163
Author(s):  
Wen Hong Liang ◽  
Kai Liu ◽  
Xiao Lin Liu ◽  
Ya Hui Cui
Keyword(s):  
Hydrodynamic Lubrication ◽  
Normal Pressure ◽  
Spur Gear ◽  
Transmission Efficiency ◽  
Gear Train ◽  
Gear Teeth ◽  
Gear Mesh ◽  
Nonlinear Relation ◽  
On Line ◽  
Planet Gear

Engagement between gear teeth with confriction has been analyzed aim at low speed and heavy transmission mode of spur gear in aerogenerator gearbox. Nonlinear relation between parameters such as confriction, normal pressure, number of teeth, ratio of transmission, and thickness of fluid film has been deduced by using the theory of elasto-hydrodynamic lubrication (EHL) and gear mesh. Numerical calculation of these equations has been made progress by using MATLAB software under the premise of no analytical solution. The efficiency of each point on line of action has been received. And then the influence of confriction in intertooth space to transmission efficiency under EHL has been analyzed. The results can be provided as argument and numerical value reference for optimization of the gearbox lectotype in areogenerator to make the efficiency maximized, and for further research on transmission efficiency of planet gear train.

A Computational Study on the Mechanical Power Loss of a Spur Gear Pair Under the Thermal Tribo-Dynamic Condition

2015 ◽  
Author(s):  
Sheng Li
Keyword(s):  
Power Loss ◽  
Computational Study ◽  
Dynamic Condition ◽  
Elastohydrodynamic Lubrication ◽  
Static Condition ◽  
Spur Gear ◽  
Mechanical Power ◽  
Gear Pair ◽  
Gear Mesh ◽  
Six Degree Of Freedom

This study proposes a formulation for the description of the gear mesh mechanical power loss under the thermal tribodynamic condition. A six degree-of-freedom motion equation set that models the vibratory motions of a general spur gear pair is coupled with the governing equations for the description of the gear thermal mixed elastohydrodynamic lubrication to include the interactions between the gear dynamics and gear tribology disciplines in the modeling of the gear mesh mechanical power loss. The important role of the gear thermal tribo-dynamics in power loss is demonstrated by comparing the predictions of the proposed model to those under the thermal quasi-static condition, and the iso-thermal tribo-dynamic condition, respectively.

A Fatigue Model for Spur Gear Contacts Operating Under Mixed Elastohydrodynamic Lubrication Conditions

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
S. Li ◽  
A. Kahraman ◽  
M. Klein
Keyword(s):  
Crack Nucleation ◽  
Surface Condition ◽  
Elastohydrodynamic Lubrication ◽  
Spur Gear ◽  
Mixed Lubrication ◽  
Distribution Model ◽  
Tooth Surface ◽  
Stress Concentrations ◽  
Fatigue Model ◽  
Lubrication Conditions

This paper presents a model to predict the crack formation fatigue lives of spur gear contacts operating under mixed lubrication conditions where surface roughnesses introduce intermittent metal-to-metal contacts and severe stress concentrations. The proposed model consists of several submodels, including (i) a gear load distribution model to determine the normal tooth force distribution along the tooth surface, incorporating any profile modifications and manufacturing deviations, (ii) a mixed elastohydrodynamic lubrication model customized to handle transient contact conditions of gears, (iii) a stress formulation that assumes the plane strain condition to compute the transient elastic stress fields on and below the tooth surface induced by the mixed lubrication surface pressure and shear stress distributions, and (iv) a multi-axial fatigue model to predict the crack nucleation life distribution. The proposed spur gear fatigue model is used to simulate the contacts of gear pairs having different surface roughness amplitudes. The predictions are compared to the measured gear fatigue stress-life data for each surface condition to assess the model accuracy in the prediction of the crack nucleation fatigue lives as well as the location of the critical failure sites.

A Fatigue Model for Spur Gear Contacts Operating Under Mixed Elastohydrodynamic Lubrication Conditions

2011 ◽  
Author(s):  
Sheng Li ◽  
Ahmet Kahraman ◽  
Mark Klein
Keyword(s):  
Crack Nucleation ◽  
Surface Condition ◽  
Elastohydrodynamic Lubrication ◽  
Spur Gear ◽  
Mixed Lubrication ◽  
Distribution Model ◽  
Tooth Surface ◽  
Stress Concentrations ◽  
Fatigue Model ◽  
Lubrication Conditions

This paper presents a model to predict the crack formation fatigue lives of spur gear contacts operating under mixed lubrication conditions where surface roughnesses introduce intermittent metal-to-metal contacts and severe stress concentrations. The proposed model consists of several submodels including (i) a gear load distribution model to determine the normal tooth force distribution along the tooth profile, incorporating any profile modifications and manufacturing deviations, (ii) a mixed elastohydrodynamic lubrication model customized to handle transient contact conditions of gears, (iii) a stress formulation that assumes the plane strain condition to compute the transient elastic stress fields on and below the tooth surface induced by the mixed lubrication surface pressure and shear stress distributions, and (iv) a multi-axial fatigue model to predict the crack nucleation life distribution. The proposed spur gear fatigue model is used to simulate the contacts of gear pairs having different surface roughness amplitudes. The predictions are compared to the measured gear fatigue Stress-Life data for each surface condition to assess the model accuracy in predicting the crack nucleation fatigue lives as well as the location of the critical failure sites.

A numerical study on the contact fatigue life of a coated gear pair under EHL

2018 ◽  
Vol 70 (1) ◽  
pp. 23-32 ◽  
Author(s):  
Ye Zhou ◽  
Caichao Zhu ◽  
Huaiju Liu ◽  
Chaosheng Song ◽  
Zufeng Li
Keyword(s):  
Fatigue Life ◽  
Numerical Study ◽  
Contact Fatigue ◽  
Elastohydrodynamic Lubrication ◽  
Spur Gear ◽  
Hard Coatings ◽  
Gear Pair ◽  
Content Type ◽  
Life Model ◽  
Contact Fatigue Life

Purpose Coatings are widely used in gears to keep interface from wearing excessively. The purpose of this paper is to study the effect of coating properties and working conditions on the pressure, the shear traction, stresses as well as the fatigue life of spur gear. Design/methodology/approach A numerical contact fatigue life model of a coated spur gear pair under elastohydrodynamic lubrication (EHL) is developed based on the characteristics of gear geometry and kinematics, lubrication conditions and material properties. Frequency response functions and the discrete convolute and fast Fourier transform (DC-FFT) algorithm are applied to obtain elastic deformation and stress. Mutil-axial fatigue criteria are used to evaluate the contact fatigue life based upon the predicted time-varying stress fields of coated bodies. Findings The maximum Mises stress decreases while the fatigue life increases as the coating modulus decreases. A thinner coating leads to a longer life and a smaller maximum Mises stress for hard coatings. The load has more significant effect on the contact fatigue life of soft coatings. Originality/value The developed model can be used to evaluate the contact fatigue life of coated gear under EHL and help designers analyze the effect of coating elastic modulus and thickness on the contact pressure, film thickness and stress.

Prediction of Spur Gear Mechanical Power Losses Using an EHL Model With Time-Varying Contact Parameters

2009 ◽  
Author(s):  
S. Li ◽  
A. Kahraman
Keyword(s):  
Power Loss ◽  
Normal Load ◽  
Elastohydrodynamic Lubrication ◽  
Spur Gear ◽  
Mechanical Power ◽  
Transient Pressure ◽  
Gear Mesh ◽  
Proposed Model ◽  
Time Variations ◽  
Contact Parameters

A physics-based model is proposed to predict load dependent (mechanical) power loss of spur gear pairs by using a specialized gear elastohydrodynamic lubrication (EHL) model. The EHL model includes time variations of all key contact parameters such as surface velocities, radii of curvature and normal load in their continuous forms such that a continuous analysis of a tooth contact from its root to tip can be performed. The EHL model has the capability to simulate any gear contacts represented by condition ranging from full EHL to mixed or boundary EHL conditions. Predicted transient pressure and film thickness distributions are used to determine the instantaneous as well as the overall mechanical power loss of the gear mesh. Correction factors are introduced to account for thermal effects. At the end, capabilities and accuracy of the proposed model are demonstrated by comparing its predictions to experimental data.

Molecular Dynamics Simulation of Crack Initiation of Aluminum under Tensile Deformation

2011 ◽  
Vol 378-379 ◽  
pp. 7-10
Author(s):  
Gui Xue Bian ◽  
Yue Liang Chen ◽  
Jian Jun Hu ◽  
Li Xu
Keyword(s):  
Mechanical Properties ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Elastic Constants ◽  
Tensile Deformation ◽  
Crack Nucleation ◽  
Tensile Load ◽  
Dynamics Simulation ◽  
Metal Aluminum ◽  
Impurity Metal

Molecular dynamics simulation was used to simulate the tension process of purity and containing impurity metal aluminum. Elastic constants of purity and containing impurity metal aluminum were calculated, and the effects of impurity on the elastic constants were also studied. The results show that O-Al bond and Al-Al bond near oxygen atoms could be the sites of crack nucleation or growth under tensile load, the method can be extended to research mechanical properties of other metals and alloys structures.

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