The Effect of Notches at the Tooth Root Fillet on the Endurance Strength of Gears

1978 ◽  
Vol 100 (3) ◽  
pp. 417-422
Author(s):  
H. Winter ◽  
X. Wirth
Keyword(s):  
Shot Peening ◽  
Calculation Procedure ◽  
Special Importance ◽  
Spur Gears ◽  
Tooth Root ◽  
Characteristic Parameters ◽  
Uniform Heat ◽  
Endurance Strength

Notches at the tooth root fillet can be caused by shaving or grinding. The influence of different notches at the root fillet on the endurance strength of case hardened spur gears was investigated in back-to-back tests and pulsator tests. Data of the test gears: MnCr and CrNi Steels, module 3 (8 DP) and module 8 (3 DP). Besides the a.m. tests photo elastic investigations were performed. On the basis of some characteristic parameters, it was possible, to find a calculation procedure, to determine the loss of endurance strength due to the effect of various kinds of notches. Moreover it was investigated to what extent the endurance strength of notched gears could be increased by regrinding or shot peening the root fillet. It is known that notches at the tooth root fillet can essentially reduce the endurance strength of gears. This is of special importance for case hardened gears. It is desirable that such notches should be avoided, but sometimes notches are produced by shaving or grinding due to inadequacy of tooling or non-uniform heat distortion. Therefore the influence of geometry and position of notches at the root fillet on the endurance of case hardened spur gears was investigated in back-to-back and pulsator tests. Additionally the extent the endurance strength of notched gears could be increased by regrinding or shot peening the root fillets was studied.

scholarly journals Tooth Root Bending Fatigue Strength of High-Density Sintered Small-Module Spur Gears: The Effect of Porosity and Microstructure

Metals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 599 ◽  
Author(s):  
Vigilio Fontanari ◽  
Alberto Molinari ◽  
Michelangelo Marini ◽  
Wolfgang Pahl ◽  
Matteo Benedetti
Keyword(s):  
Fatigue Strength ◽  
Surface Defect ◽  
Detrimental Effect ◽  
Case Hardening ◽  
Spur Gears ◽  
Tooth Root ◽  
Near Surface ◽  
Bending Fatigue ◽  
Microstructural Constituent ◽  
Bending Fatigue Strength

The present paper is aimed at investigating the effect of porosity and microstructure on tooth root bending fatigue of small-module spur gears produced by powder metallurgy (P/M). Specifically, three steel variants differing in powder composition and alloying route were subjected either to case-hardening or sinter-hardening. The obtained results were interpreted in light of microstructural and fractographic inspections. On the basis of the Murakami a r e a method, it was found that fatigue strength is mainly dictated by the largest near-surface defect and by the hardness of the softest microstructural constituent. Owing to the very complicated shape of the critical pore, it was found that its maximum Feret diameter is the geometrical parameter that best captures the detrimental effect on fatigue.

Stress Analysis of Cylindrical Webbed Spur Gears: Parametric Study

1998 ◽  
Vol 120 (2) ◽  
pp. 349-357 ◽  
Author(s):  
H. C. Kim ◽  
J. P. de Vaujany ◽  
M. Guingand ◽  
D. Play
Keyword(s):  
Simple Formula ◽  
Computer Software ◽  
Web Design ◽  
Maximum Principal Stress ◽  
Design Parameters ◽  
Preliminary Design ◽  
Spur Gears ◽  
Tooth Root ◽  
Detailed Design ◽  
Meshing Stiffness

In this paper, a numerical computer software based on the Finite Prism Method, is proposed in order to design external cylindrical spur gears with a web. It enables computing load sharing, pressure distribution, meshing stiffness and 3D tooth fillet stresses. The software is generally used during the detailed design for optimizing gear meshing. The software is also used to quantify the influences of web design parameters. The process is based on a statistical method: experimental design, that permits studying the influence of parameters. Thus, a simple formula was found in order to estimate the maximum principal stress in the tooth root. The results of the formula were compared with those found in the bibliography. The formula can be useful during the preliminary design for predimensioning webbed spur gears in design department.

scholarly journals Fast tooth root load capacity optimization based on improved design of hob geometry

2019 ◽  
Vol 287 ◽  
pp. 01011 ◽  
Author(s):  
Ray Uelpenich ◽  
Peter Tenberge
Keyword(s):  
Load Capacity ◽  
Optimization Methods ◽  
Spur Gears ◽  
Tooth Root ◽  
Manufacturing Costs ◽  
Root Fracture ◽  
Computational Speed ◽  
Performance Ability ◽  
Improved Design ◽  
Root Stress

The competitiveness of gearboxes is significantly influenced by their performance ability. Increasing the tooth root load capacity has always been in focus of current research because in case of a failure of the gearwheel due to a tooth root fracture, the complete gearbox fails. This paper presents a new calculation method that enables the optimization of hob geometries within a few minutes so that they lead to reduced stresses in the tooth root fillet of spur gears. This results in reductions of the maximum tooth root stress of 10% and more for most gearwheels. The manufacturing costs for the optimized hob are only influenced slightly. In order to increase the computational speed compared to purely FE-based optimization methods, the present paper shows a method in which the decisive part of the optimization process is based on an analytical equation which are derived by a small number of FE-calculations.

Further Evaluation of Spur Gear Tooth Profile Designs Used in Heavily Loaded Transmissions

2011 ◽  
Author(s):  
Nihat Yıldırım ◽  
Hakan I˙s¸c¸i ◽  
Abdullah Akpolat
Keyword(s):  
Gear Tooth ◽  
Transmission Error ◽  
Spur Gear ◽  
Tooth Profile ◽  
Design Parameters ◽  
Preference Order ◽  
Spur Gears ◽  
Tooth Root ◽  
Contact Ratio ◽  
Practical Applications

Aerospace applications require special procedures for component design and manufacturing. Spur gears of different designs, because of their simpler geometries, are used in vital units-transmissions of helicopters and alike aerospace vehicles. In this study, performances of various profile designs of previously researched low and high contact ratio spur gears with some realistic design parameters are studied. Effects of the realistic parameters of variable tooth pair stiffness, relief shape, and adjacent pitch error on Transmission Error (TE), tooth loads and root stresses are presented; composition of these parameters determines the efficiency of the gearbox assembly. Detail of minimization of tooth root stress through optimized/proper design of relief is described. More comprehensive comparison of the gear tooth profile design cases is done to be able to guide aerospace transmission designers for practical applications with realistic parameters for each of the design cases. A preference order is done among the design cases, depending on effect of some design parameters on the results such as tooth loads, tooth root stresses, TE curves and peak-to-peak TE values.

scholarly journals Study on the Influence Coefficient of Residual Stress used to Estimate the Stress Life Curve of Gears

2020 ◽  
Author(s):  
Zhen Wang ◽  
Long Chen ◽  
Zhong-Ming Liu ◽  
Jun-Wei Cheng
Keyword(s):  
Residual Stress ◽  
Crack Propagation ◽  
Fatigue Test ◽  
Shot Peening ◽  
Calculated Data ◽  
Labor Cost ◽  
Step Function ◽  
Influence Coefficient ◽  
Tooth Root ◽  
Crack Propagation Process

Abstract This study aims to estimate the gear S-N curve by the influence coefficient m of the residual stress at the root of the gear for providing theoretical basis and experimental support for the study of the bending fatigue performance of the gear. Based on the crack propagation theory and the linear damage accumulation theory, according to the Goodman relation, the residual stress is treated as the average stress. The spatial distribution of the residual stress is considered, and the residual stress is treated as a step function about depth, so the crack propagation process is divided into several stages. Through the fatigue test, the S-N curve of the gear is obtained. In order to avoid the influence of gear material and shape on the coefficient m, the S-N curve after heat treatment is used as the initial S-N curve, and the S-N curve after shot peening is used as the result curve. Through S-N curve, the influence coefficient m of tooth root residual stress is calculated, and the S-N curve of gears after shot peening is deduced by m value, which is compared with the S-N curve obtained by experiment. The influence coefficient m of residual stress calculated by S-N curve is 0.2132. The S-N curve of shot peening derived from m value is lnS=7.6963-0.0821lnN, which is consistent with the trend of S-N curve obtained by experiment, and the calculated data are more secure in the case of high cycle fatigue. The huge capital and labor cost of gear fatigue test can be saved by estimating gear S-N curve more accurately by m value. It provides a theoretical and experimental basis for the study of the influence coefficient of tooth root residual stress, and provides a solution for estimating the gear S-N curve.

scholarly journals On the evaluation of the meshing stiffness of external spur gears

2020 ◽  
Vol 317 ◽  
pp. 01002
Author(s):  
Miguel Pleguezuelos ◽  
Miryam B. Sánchez ◽  
José I. Pedrero
Keyword(s):  
Load Sharing ◽  
Contact Stresses ◽  
Spur Gears ◽  
Tooth Root ◽  
Meshing Stiffness

A comparison among different approaches of the meshing stiffness of spur gears has been carried out. The influence of each one on the load sharing, and subsequently on the determinant tooth-root and contact stresses, has also been studied. Equations for the evolution of the meshing stiffness along the path of contact according to all these formulations are also provided.

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