Tooth Root Bending Research Articles

Effect of Mezzo-Heterogeneous Microstructure and Rolling on the Tooth Root Bending Fatigue Properties of Sintered Ni Alloy Steel Gears

This study aims at reducing costs of high load gear manufacturing, and substituting P/M gears for conventional wrought steel gears. In order to improve the fatigue strength of P/M gears, we focused on the rolling and the high performance sintered and heat treated 4600 series alloy steels with mezzo-heterogeneous microstructure which were made from the mixed elemental powders. The fatigue strength was determined by single tooth root bending fatigue test machine, and the effect of mezzo-heterogeneous microstructure and rolling on the fatigue strength was mainly investigated. The endurance limit at N=3.0×106 of the 500 μm rolled 6 % Ni alloy steel gear compact showed 950 MPa which value is about 2/3 of the case hardened wrought steel (SCM415) gears. However, the endurance limit of rolled and heat treated gear compact showed lower value (630 MPa) as compared to as-rolled gear compact. This seems to be due to the decreasing the compressive residual stress by heat treatment and unfavorable mezzo-heterogeneous microstructures.

Optimization Design of the Composite Hub Connection Structure Based on ANSYS Software Technology

This article through analysing coupler's structure, involute spline's stress situation, the tooth face contact intensity, the tooth root bending strength, the tooth root shearing strength, tooth face wear ability and the external spline reverse and curving bearing capacity carry on the precise computation and the examination, simultaneously a multianalysis bulge tight joint set of structure and the correlation computation examination, has established the shaft bossing compound coupler main spare part structure type. In this article based on the shaft bossing composite construction optimization design is targeted mainly flexibility swelling ring shape to optimize the design, change that flexibility swelling ring cone-cone angle, which makes flexible swelling ring Auxiliary T-twisting greater. In the analysis, it is necessary to use the software ANSYS, through the creation of the shaft bossing composite construction of the parametrization model, a flexible swelling ring cone-cone angle of the design variables and flexibility swelling ring allowable material stress as binding conditions, bulging with flexible support ring-twisting as the objective function of T,right propeller shaft coupler hub composite structure axisymmetric analysis, contact analysis and design optimization, inflation reached a flexible support ring largest T-twisting, work stress does not exceed the allowable material stress, elastic swelling ring-cone angle of the optimal solution.

鉄系焼結合金歯車の歯元曲げ疲労強度に及ぼす転造の影響

Sintered ferrous alloy gears are used in wide engineering fields. However, it is difficult for them to be applied to the parts loading at high stress levels, because their strength is poorer than that of the wrought materials. In this study, sintered ferrous alloy gears were rolled and their tooth root bending fatigue strengths were investigated. The effect of rolling conditions on the porosity distribution and hardness at tooth root, and the tooth root bending fatigue strength were determined. As the amount of stock rolled was increased, the porosity of the vicinity of the surface was decreased and the hardness was increased, and also the tooth root bending fatigue strength was increased to certain level, and then the fatigue strength was decreased. This seemed to be due to the shaving when the gear was rolled.

Effect of addendum on contact strength, bending strength and basic performance parameters of a pair of spur gears

Abstract This paper investigates effect of addendum on tooth contact strength, bending strength and basic performance parameters of spur gears. Face-contact model of teeth, mathematical programming method (MPM) and three-dimensional (3D), finite element method (FEM) are used together to conduct loaded tooth contact analyses (LTCA), deformation and stress calculations of spur gears with different addendums and contact ratios. Tooth load, load-sharing rate, contact stress, root bending stress, transmission error and mesh stiffness of the spur gears are analyzed. Effects of addendum and contact ratio on gear strength and basic performance parameters are also discussed. It is found that contact stress distributed on tooth surface along the profile is asymmetrical around the geometrical contact point of the gears when the geometrical contact point is far away from the pitch point, especially at the tip or root contacts. The maximum contact stress is also not exactly at the geometrical contact point. Hertz formula can only calculate the tooth contact stress approximately. FEM can be used to conduct precise analysis of the tooth contact stress. It is also found that increment of addendum can increase number of contact teeth, then this increment can reduce tooth contact stress and root bending stress, generally speaking. But this increment also makes the tooth depth long and lets the tooth be deformed easily. So, this increment can reduce tooth contact stress, but there is no guarantee that this increment can certainly reduce tooth root bending stress. Also, increment of the addendum makes the values of “T” and “V” in the so-called value of “PVT” great. So, scoring strength calculations of the tooth tip and root becomes more important when to use high contact ratio gears (HCRG) with long addendum. Finally, strength calculations of HCRG with misalignment error, lead crowning and thin-walled thickness are discussed simply in this paper.

916 浸炭焼入れ平歯車の歯元曲げ強度に及ぼすボス幅の影響(機素潤滑設計III)

916 浸炭焼入れ平歯車の歯元曲げ強度に及ぼすボス幅の影響(機素潤滑設計III)

Effects of machining errors, assembly errors and tooth modifications on loading capacity, load-sharing ratio and transmission error of a pair of spur gears

Abstract This paper quantitatively investigates effects of machining errors (ME), assembly errors (AE) and tooth modifications (TM) on loading capacity, load-sharing ratio (LSR) and transmission error (TE) of a pair of spur gears by using special-developed finite element method (FEM) software in a personal computer. Tooth surface contact stress (TSCS) and tooth root bending stress (TRBS) of a pair of spur gears with ME, AE and TM are analyzed by the FEM software. Effects of ME, AE and TM on TSCS and TRBS are also defined as “Influence factors” and the influence factors of ME, AE and TM on TSCS and TRBS are calculated quantitatively. It is found that misalignment error of gear shafts on the plane of action of the spur gears exerts great effects on TSCS and TRBS while misalignment error of gear shafts on the vertical plane of the plane of action almost exerts no effects on TSCS and TRBS. It is also found that ME and lead crowning have greater effects on TSCS and TRBS. When the maximum tooth surface machining error is 40 μm, influence factor of ME on TSCS and TRBS are about 2.2 and 1.5. When quantity of lead crowning is 40 μm, influence factor of lead crowning on TSCS and TRBS are about 2.0 and 1.4. These influence factors can be used as references when ISO standards are used for tooth surface contact strength and root bending strength calculations of a pair of spur gears with ME, AE and TM. Methods for LSR calculation of a pair of spur gears with ME, AE and TM are also presented in this paper. Effects of ME, AE and TM on LSR are analyzed quantitatively. It is found that ME has greater effect on LSR. When the maximum tooth surface machining error is greater than 10 μm, double pair tooth-contact shall become single pair tooth-contact for sake of the effect of ME. This means that when ME on tooth surface is large, outer limit of the single pair tooth-contact area can not be used as the so-called “worst load position”. It is safe and reasonable to use tooth tip as the “worst load position” when to perform tooth bending strength calculation. Methods for TE calculation of a pair of spur gears with ME, AE and TM are also presented in this paper. Effects of ME, AE and TM on TE of the gears are analyzed quantitatively. It is found that ME not only changes waveform of TE easily, but also makes TE greater and greater when ME is increased. AE and TM also make TE greater and greater when they are increased, but do not change waveform of TE.

Bending Load Capacity Enhancement Using an Asymmetric Tooth Profile

This research is to develop a new method to enhance the bending load capacity of gear tooth using asymmetric tooth profiles. For many power transmission devices operate in one direction, only one side of the tooth surfaces (the front of tooth) is in mesh. So the tooth is not necessary to be a symmetric form. The dimensions of the front and back profiles of the tooth could be designed individually. The back profile of the tooth that does not contact in running could be decided to decrease the maximum tensile stress at the root of tooth. Different standard pressure angles are used in the front and back profiles of an asymmetric tooth. Tooth root stress and bending stiffness of the asymmetrical tooth for several combinations of standard pressure angles were calculated by the use of finite element method. Based on the results of calculations, it is clarified that a larger standard pressure angle in the back profile of tooth makes the tooth root stress decrease remarkably and bending stiffness of tooth increase, but dose not change the load sharing ratio.

Bending Capacity Enhancement Using an Asymmetric Tooth Profile : 1st Report, Influences of Pressure Angle on Tooth Root Stress and Bending Stiffness

This study is to develop a new method to enhance the bending capacity of gear tooth by the use of asymmetric tooth profile. Considering that many power transmission devices operate in one direction, where only one tooth surface (the front of tooth) is practically used. Therefore, it is not necessary to make tooth profile symmetrically, the back profile of tooth, which does not mesh in operation, can be designed to decrease tooth root stress. Different standard pressure angles are used to the front and back tooth profiles. Finite element method was used to calculate the tooth root stress and the bending stiffness of the asymmetrical tooth in several standard pressure angle combinations. Based on the results of calculations, it is clarified that tooth root stress decreases and bending stiffness increases remarkably by the use of a large standard pressure angle in the back profile of tooth, but no clear change in load sharing ratio appears during meshing period.

A study on the dynamic behavior of a skew bevel gear (1st report, On root stress ratio, torsional vibration, bending vibration of gear shaft, and vibrating displacements in three right-angled directions)

A skew bevel gear, whose contact ratio is larger than a straight bevel gear, can be expected to be superior to a straight bevel gear on strength, vibration and noise. And the characteristics of a skew bevel gear. In the present paper, the dynamic behavior of a skew bevel gear was investigated under various gear operating conditions, using a power circulating type bevel gear testing machine, and by measuring the tooth root stresses, the torsional and bending vibrations of the gear shaft, and the vibrating displacements in three directions perpendicularly intersecting each other on a skew bevel gear. In comparison with these measured data, the dynamic characteristic of a skew bevel gear became clear.

Fatigue Strength of RDK401 Nitrocarburized at Low Temperature

In order to examine the application limit of gears made of RDK401 which has a deep case depth by a low temperature gas nitrocarburizing treatment, the Ono-type rotating beam fatigue test, the Nishihara-type rolling contact fatigue test and gear test were carried out, then the underwritten results were obtained.(1) The rotating beam fatigue strength is 42kgf/mm2, when the stress concentration factor is 1.84.(2) The rolling contact fatigue strength is 180kgf/mm2, when the effective case depth is 0.19mm.(3) According to the gear tests, the allowable tooth root bending stress is 41kgf/mm2 and its value is near to that of the carburized gears. Then the allowable tooth surface stress is over 145kgf/mm2 in Hertz pressure.