Frictional Contact Stress Analysis of Spur Gear by Using Finite Element Method

Spur gears are widely used in the power transmission mechanism of several machines. Due to the transmitted torque, spur gears experience high stresses which could cause gear tooth failure by surface pitting or root fracture. Tip relief and other gear profile modification have been considered for reducing the induced stresses in the gear tooth. In this work, the influence of tip relief on stresses on a pair of identical spur gear was analyzed using commercial FEA software ANSYS, and formulae for estimating contact and bending stresses were derived. Three cases of gear sets were analyzed; a non-modified pair and another two sets with linear and parabolic tip relief profiles. The non-modified gear set frictionless contact stress was validated against the calculated AGMA pitting resistance, Hertzian contact stress and a reported contact stress value in the literature. The four methods agreed well with each other. Similarly, bending stress was also compared with the AGMA bending strength and Lewis bending stress for validation. Then, friction coefficient was varied from 0.0 to 0.3 with increment of 0.1. The gear contact stress increased up to 11% relative to the frictionless case, whereas bending stress decreased by 6%. Linear tip relief modification was carried out for increasing normalised tip relief values of 0.25 to 1.0 with increment of 0.25. The gear frictionless contact and bending stresses decreased by a maximum of 4% and 2%, respectively. Frictional contact stress increased by up to 7.1% and the bending stress is almost identical with the frictionless case. Parabolic tip relief was also carried out with similar normalised tip relief values. Frictionless contact stress decreased by 5% while frictional contact stress increased by up to 11.5% and the bending stress is also almost identical with the frictionless case. Finally, four formulae were introduced for estimating the contact and bending stresses for a tip modified spur gear.

The damage that occurs on the teeth flank of cylindrical gears is a complex phenomenon and depends on many factors. The most common cause for these damages is the high contact stress of the meshing gears. Although this contact pressure, by itself, cannot be a criterion for determining the durability of the gears, a good correlation has been found between the contact or Hertz pressure and the damage that occurs on the tooth flank. This paper analyzes the influence of the pressure angle α on the contact stress. Analytical calculation according to the ISO 6336-2:2006 and finite element method (FEM) was used for the analysis. Four cases were analyzed with a change in the pressure angle, i.e., cylindrical spur gears and pressure angles of 17.5°, 20°, 22.5° and 25°. In the results, it was noted that by increasing the pressure angle, the contact stress decreases. It can also be concluded that by increasing the pressure angle, the difference in the results between the analytical and FEM analysis, also increases.

7 - Detailed Gear Stressing

Loaded tooth contact analysis (LTCA), deformation, and stress calculations of three types of thin-rimmed spur gears with inclined webs at the left side, the center, and the right side of the tooth are conducted in this paper with finite element methods (FEM) combined with a mathematical programming method when these gears are engaged with a solid mating gear. The contact stresses on the tooth surfaces, the bending stresses at the tooth roots, and the joint stresses of the rim and the web are analyzed as the web position and the web angle are changed. It was found that the web position and the web angle of the thin-rimmed gears have a significant effect on the tooth contact stresses, the root bending stresses, and the joint stresses. The maximum contact stress of the right web gear becomes very small when the web is inclined from 0 to 30 deg, and it increases again when the web angles are changed from 45 to 60 deg. This interesting relationship between the web angle and the tooth contact stresses of thin-rimmed right inclined web gears is used to absorb the misalignment errors in the gears and improve the partial tooth contact pattern resulting from the misalignment errors. A calculation example is provided to illustrate how to improve the partial tooth contact patterns in gears with misalignment errors.

<h2>ABSTRACT</h2> <p><strong>Objectives:</strong> To carry out dynamic state analysis of asymmetrical helical gears for contact stresses using photo stress technique and suitable finite element software.<strong> Methods:</strong> Currently the Hertz contact stress equation is used to calculate the contact stress which is based on certain speculations. The value of load transmitted by a gear may be known but whether it is taken by a single or more pairs of teeth are based on some assumptions and stresses thus calculated may not be true stresses. To get precise evaluation of stress field in gear tooth it is decided to carry out experimental work on asymmetric helical gear in actual working condition. The photo stress method not only provide magnitude of stress but also gives idea about stress distribution in gear. Finite element method is used for asymmetrical helical gear to validate experimental results. <strong>Findings:</strong> The stress values obtained by photostress method and FEA method has minimum error of 2.17% and maximum of 8.89% respectively. The error values are less than 10% and within the limit. We can observe close agreement between these two methods.<strong> Novelty:</strong> This study has provided a more accurate result than theoretical method of stress calculation. Photostress analysis method is one of the best test methods for evaluation of contact stress of asymmetric helical gear with different torque condition in actual working that is dynamic condition. Maximum error of 8.89% has been found with photostress method.</p>

This article used ANSYS, the software of finite element analysis, to analyze the contact stress between the wheel gear and the rack the two locking devices, which called in the switch. While through adding the necessary conditions, such as restrain methods, element types, coefficient of friction, Poisson ratio, damping ratio, contact conditions etc, We are also testing the simulation meshing run of contact between gears. Then according to load the rated power to make calculations, we can get cloud map of prototype gear's contact stress. Finally, on the preliminary study basis, we build the reliability model of the gear lever transformation locks up, which use the Weibull distribution.

Design an e-drive transmi ssion gear , it is very crucial, to understand the failure modes since gears should be sized correctly to withstand loads that will expect to act on the gear teeth and make sure that still be within reasonable load-carrying capacity, compact and light weight. Fatigue failure can happen on gears under repeated loading due to fatigue such as tooth root bend ing and contact stress of gear. M aterials used in this study were two candidate alloy steels of Cr-Mo and Cr-Mo-Ni and methods employed to design the e-drive transmission gear were by iteration through KISSsoft gear simulation software as well as AGMA of Matlab script, it approaches various parameters such as helix angle, face- width , and input torque . Investigations on safety factors of root bending and contact , stresses of contact and bending , weight, compactness, qui e t and smooth functioning have been done by altering the variable design parameters . To conclude that by increasing face width and helix angle both safety factors were increased uniformly regardless of the in put torque as we calculated by both approaches. Similarly , the results showed that by increasing the helix angle and face width it brings to reduce the contact and bending stress es of transmission gear . As we comparing the results , the KISSsoft values are a little higher than the analytical (AGMA) values as proven in all fatigue of safety factors versus variable gear design parameter. Based on the sa fety factor, compactness, light weight and quiet for smooth function of the designed e-drive mating gears are proven as the face width is 24.5 mm and the helix angle is 25 o .

This paper shows a new method for calculating the load distribution ratios and stress in spur gears by using the finite element models with many gear teeth. The results about the ratios of load taken by meshing gear tooth to the full load and the stress distribution show a noticeable difference between the analysis assuming that the load is shared between 2 pairs of teeth and the one assuming that it is carried by a single pair of teeth. This method makes it possible to clarify the effects of the ratio of contact and the addendum modification coefficience upon the load distribution ratio, stress distribution in gears and the stress concentration in the fillet at the base of the tooth.

Planetary gear trains are widely applied in various transmission units. Whether strengths of all gears are accurately calculated or not can affect reliability of the entire system significantly. Strength calculation method for planetary gear trains usually follows the method for cylindrical gears, in which the worst meshing positions for both contact stress and bending stress cannot be determined precisely, and calculation results tend to be conservative. To overcome these shortcomings, a kinematics analysis for a planetary gear train is firstly performed, in which the influence of relative speed is investigated. Then the finite element strength analysis of a planetary gear train based on its transient meshing properties is carried out in ANSYS. Time–history curves of contact and bending stresses of sun gear, planetary gears and ring gear are respectively obtained. Also the accurate moment and its corresponding position of the maximum stress are precisely determined. Finally, calculation results of finite element method (FEM) and traditional method are compared in order to verify the effectiveness. Simulation and comparison show the stability of the proposed method in this paper. Researches in this paper establish the foundations for fatigue analysis and optimization for a planetary gear train.

This work is an analysis of gear slippage and contact stresses in toothed gears of a six-shaft power shift gearing. Gear meshing contains 5 characteristic contact points located within the active surface of a tooth. The contact points are as follows: A – beginning of a tooth involute profile located within double-tooth engagement area; B – the end-point of double-tooth engagement constituting the beginning of single-tooth engagement area; C – pitch point, referred to also as the central contact point; D – the last point of the single-tooth engagement being at the same time the starting point of the double-tooth engagement area, which is a part of the tooth tip; and, E – point at the tooth tip that closes the double-tooth engagement area. The location of individual contact points and the resulting slippage and contact stress values depend on the geometrical parameters of cooperating gear wheels. The inter-relationship suggests that, in power shift gearings, the contact points have as many positions within the active surface as there are cooperating gear wheels.

In this paper the problem of the failure of gear in speed reduction gearbox developed by Laxmi Hydraulic Pump (LHP) Pvt Ltd, Solapur is resolved by replacing the existing material by a material SAE8620. The Gear and Pinion using AGMA and FEM analysis Method. In the gear design, the bending stress and surface strength of the gear tooth are considered to be one of the main factors to the failure of the gear. In this paper bending and contact stresses are calculated by using analytical method as well as Finite Element Method. To estimate bending stress modified Lewis beam strength method is used as well as AGMA method. Software is used to generate the 3-D solid model of helical gear. Ansys software package is used to analyze the bending stress. Contact stresses are calculated using modified AGMA contact stress method. Ansys software package is used to analyze the contact stress and bending stress. The main objective of this study has to investigate the stresses induced by gear tooth profile. Finally, the results obtained by theoretical analysis and Finite Element Analysis are compared to check the correctness. Estimated stress is used to calculate module of gear which can withstand easily at given loading conditions. A conclusion has arrived on the material which is best suited for helical gear based on the results.

This work centers on the development of a three-dimensional tire– pavement interaction model in order to study the distribution of contact stresses, for future use in mechanistic analysis of pavement behavior. Using the finite element method within the Abaqus code, a longitudinal tread tire and an elastic asphalt pavement were modeled. The contact area and stress distribution were simulated under steady-state, rolling, and braking conditions, incorporating dynamic traffic loads. Pavement roughness was analyzed by considering different friction coefficients, and a parametric study was conducted on tire inflation pressure and rolling speed. Moreover, the study examined the effect of pavement geometry by considering different road camber and rut depth. The findings indicate that both inflation pressure and tire friction coefficient significantly influence the 3D contact stress distribution as well as the road camber and rut depth.

Most steel gears are carburized and quenched prior to service to obtain the desired specific strength (σ/ρ) and hardness requirements. Use of carburization and quenching of steel gears creates a compressive residual stress on the carburized surface, which is beneficial for improving both bending and contact fatigue performance. Also, higher carbon content in the carburized surface decreases the starting temperature for formation of the martensitic phase and delaying the martensitic transformation at the part surface during the quenching hardening process. During the martensite phase formation, the material volume expands. The delayed martensitic transformation, coupled with the associated delayed volume expansion, induces residual compressive stress on the surface of the quenched part. The carburized case depth and distribution of carbon affect both the magnitude and the depth of the resulting residual compressive stress. In this article, the effect of carbon distribution on the residual stress in a spur gear is presented and discussed using finite element modeling to understand the intrinsic material mechanics contributing to the presence of internal stress. Influence of the joint on thermal gradient and the influence of phase transformation on the development of internal stresses are discussed using results obtained from modeling. The residual stress arising due to heat treatment is imported into single-tooth bending and dynamic contact stress analysis models to investigate the intrinsic interplay among carbon case depth, residual stress, bending load, and torsional load on potential fatigue life. Three carburization processes, followed by oil quenching, are examined. A method for designing minimum case depth so as to achieve beneficial residual stresses in gears subjected to bending and contact stresses is suggested.

Misalignment of gear shafts, due to manufacturing and assembly errors, has an adverse influence on gear tooth stresses, load sharing and smooth transmission. In practice, gear tooth modifications, such as crowning, are often resorted to. In this work, investigations of simultaneous effect of both misalignment and crowning on transmission error and mesh stiffness variation have been carried out. Necessary three-dimensional model is created using in-house developed code for generation of involute and trochoidal profiles. The three-dimensional stress analysis is carried out using general purpose FEM software ANSYS 12 for contact stresses. The effect of misalignment on the contact stress for different angular rotations during meshing cycle is analysed. A method to obtain contact stress pattern on the basis of a threshold value is proposed in this work. Mesh stiffness, load sharing ratio and transmission error are also evaluated over a complete mesh cycle. The results for uncrowned and crowned spur gear with misalignment errors are compared and discussed in this paper.

This paper reports a method to modify the gear tooth profile of a wind turbine gearbox to reduce the noise caused by the impact of the gear teeth. The major causes of tooth impact are the elastic deformation of the gear teeth, shafts, and case of the gearbox under loading, and the fabrication tolerances in gear manufacturing. In this study, the tooth profile was modified considering the elastic deformation of the gear tooth and the tooth lead modification to compensate for tooth interference in the lead direction as a result of shaft deformations. The method was applied to the gearbox of a 2.5MW wind turbine, and the transmission error was characterized before and after modifying the gear teeth. For the modified gear teeth, the transmission error (67.6%) was lower by 17.8%. Additionally, the gear contact stress was reduced by 6.3%, to 22.3%.