Tip Relief Research Articles

A quasi-static FEM for estimating gear load capacity

Measurement of time-varying load capacity of gears is a vital process prior to manufacturing. There are two ways to evaluate the strength of gears, the analytical method proposed in AGMA and ISO standards and the finite element method (FEM). However, owing to the complex geometries and the use of empirical values, analytical model is not precise to perform the exact calculation. The current dynamic FEM and static FEM also have some disadvantages may cause the analysis of time-vary load capacity difficult. Therefore, the first aim of this study is to develop a new quasi-static FEM based on ANSYS Workbench to conduct the analysis of time-varying load capacity of gear system. The second aim is to compare results of the traditional method based on AGMA equations and quasi-static FEM. The effects of tip relief are also analysed using this new method.

Experimental and analytical study of gear micropitting initiation and propagation under varying loading conditions

Micropitting damage is one of the failure modes commonly observed in gears leading to destructive failures, which in turn results in unplanned shutdown and expensive replacement, such as those observed in wind turbine gearboxes. This study investigates gear micropitting initiation and propagation when subjected to varying torque loads under a constant rotational speed. The study employs both experimental gear testing and analytical evaluation based on the ISO Technical Report of Gear Micropitting, ISO/TR 15144-1:2010 and the recently revised ISO/TR 15144-1:2014. Initiation and propagation of micropitting are assessed in testing by quantifying the development of micropits and their progressive rate after specific numbers of running cycles at step-up torque levels. The analytical study is conducted to validate the prediction of micropitting using the ISO/TR recommended procedures by comparing the results with the occurrence of micropits in the tested gears.The gear test results show that micropitting initiates at the pinion dedendum but escalates at the addendum, because of the greater severity of progressive micropitting at the dedendum of the mating wheel where the tip relief area first comes into mesh. The analytical results, based on varying surface roughness measurements obtained from the tested gears, confirm that the maximum contact stresses and minimum specific lubricant film thicknesses occur in these regions. The specific lubricant film thickness varies considerably because of changes of surface roughness after gears are subjected to various running cycles under varying torque levels. It has found that the excessive loading, gear tooth micro-geometry, surface roughness and lubricant film thickness are the main factors affecting micropitting.

Commentary on effects of tip relief on vibration responses of a geared rotor system

The purpose of the present work is to revise the model of Ma et al. ( Proc IMechE, Part C: J Mechanical Engineering Science 2014; 228(7): 1132–1154 ). In that work, emphasis is given to the effects of tip relief on the lateral-torsional coupling vibration responses of the system, in which the time-varying mesh stiffness (TVMS) is calculated without considering the extension of the meshing period of a teeth pair due to dynamic overloads. Moreover, the dynamic model of the geared rotor system does not take into account no-loaded static transmission error (NLSTE) caused by tooth profile modification. In the present paper, the effect of the extended tooth contact on TVMS is considered and the dynamic model of the geared rotor system is revised by introducing the NLSTE. Based on the revised model, TVMS, loaded static transmission error (LSTE), NLSTE, and vibration responses are determined. Finally, comparisons of TVMS, LSTE, and vibration responses between the original model and the revised model are performed. The results show that there are some differences for the vibration responses between the original model and the revised model, and the vibration amplitude of the latter is smaller than that of the former. Furthermore, the conclusion in the original paper that the tip relief is not effective in reducing the vibration at higher mesh frequency range is not consistent with the results in current work any more.

Effects of pressure angle and tip relief on the life of speed increasing gearbox: a case study.

This paper examines failure of helical gear in speed increasing gearbox used in the wind turbine generator (WTG). In addition, an attempt has been made to get suitable gear micro-geometry such as pressure angle and tip relief to minimize the gear failure in the wind turbines. As the gear trains in the wind turbine gearbox is prearranged with higher speed ratio and the gearboxes experience shock load due to atmospheric turbulence, gust wind speed, non-synchronization of pitching, frequent grid drops and failure of braking, the gear failure occurs either in the intermediate or high speed stage pinion. KISS soft gear calculation software was used to determine the gear specifications and analysis is carried out in ANSYS software version.11.0 for the existing and the proposed gear to evaluate the performance of bending stress tooth deflection and stiffness. The main objective of this research study is to propose suitable gear micro-geometry that is tip relief and pressure angle blend for increasing tooth strength of the helical gear used in the wind turbine for trouble free operation.Electronic supplementary materialThe online version of this article (doi:10.1186/2193-1801-3-746) contains supplementary material, which is available to authorized users.

Vibration behavior optimization of planetary gear sets

This paper presents a global optimization method focused on planetary gear vibration reduction by means of tip relief profile modifications. A nonlinear dynamic model is used to study the vibration behavior. In order to investigate the optimal radius and amplitude, Brute Force method optimization is used. One approach in optimization is straightforward and requires considerable computation power: brute force methods try to calculate all possible solutions and decide afterwards which one is the best. Results show the influence of optimal profile on planetary gear vibrations.

Dynamic Analysis of Face-Gear Drive with and without Pinion Tip Relief

A nonlinear dynamic contrastive analysis of face-gear drive with and without pinion tip relief is studied. Firstly, a 2-DOF lumped parameter dynamic model of face-gear drive, considering contact characteristics, backlash, time-varying mesh stiffness, is developed and the dynamic equations are deduced. Secondly, the mesh characteristics along the line of action are obtained by applying tooth contact analysis, and the time-varying mesh stiffness is calculated by using the FEA method. Finally, the dynamic equations are solved by using Runge-Kutta numerical integral method. By comparison of three cases of pinion tip relief on dynamic response, it is found that under the condition of pinion tip relief, the vibration amplitude is reduced.

The Transient Effects of Profile Modification on Elastohydrodynamic Oil Films in Helical Gears

This article presents the results of a transient elastohydrodynamic analysis of the conditions at the contact of two pairs of helical gears operating with different gear ratios. The effects of the variation in contact geometry, kinematics, and tooth loading during the meshing cycle are taken into account together with both tip relief and axial crowning profile modifications. The results are compared with analyses under corresponding steady-state conditions for both point contact and equivalent line contact models. The comparisons show that, away from the ends of the contact lines, steady-state conditions can be used effectively to assess the film-forming capabilities of the gears. Conditions at the end of the contact lines are found to be more adverse with significant transient squeeze film effects. The form of tip relief profile adopted is shown to be highly influential in determining the peak contact pressures and thinnest oil films within the contacts. These conditions are experienced at all axial positions on the tooth flanks at the locations of the start of tip relief profile modifications. If the tip relief profile introduces a slope discontinuity to the gear profile, this can cause a significant stress concentration and very poor film-forming behavior.

Adaptive grid-size finite element modeling of helical gear pairs

A method for solving the contact problem for generic helical gear pairs (either external or internal) is described. Gear profiles are obtained by means of numerical simulation of the cutting process and an accurate description is provided in terms of NURBS curves or surfaces. A new method for finding the enveloping profiles for a generic tool (e.g. from a measured topography) is proposed. The minimum number of parameters needed to describe the profile in the presence of tip and root reliefs, helix modification and crowning is discussed. A reference structured grid is defined on the tooth, then refinement criteria are applied in order to obtain accurate solutions in terms of tooth deflection, contact pressure and fillet stress. The method allows to automatically perform a Loaded Tooth Contact Analysis (LTCA) starting from the design data of a gear pair. Results from the LTCA include contact pressure and contact pattern maps, as well as maximum fillet stress and fatigue strength. Combining several analyses within a mesh cycle, information about the Static Transmission Error (STE) and mesh stiffness is provided. The whole procedure has been implemented in a software called helical pair. A comparison with other approaches is given.

An investigation of contact stresses and crack initiation in spur gears based on finite element dynamics analysis

Contact fatigue, one of the main failure modes of gear tooth flanks, is caused by repeated compression and shear stress cycles. In this study, the surface and subsurface stresses of gear teeth are investigated using Hertzian theory and the finite element method . The number of loading cycles required for fatigue crack initiation is predicted using the Smith–Watson–Topper method based on the multiaxial fatigue mechanism. The effects of friction and speed on stress cycles and fatigue life are studied. Friction is found to shift the distributions of von Mises stress, change the extreme values of the shear stress cycle, and results in low fatigue life. The stresses near the engagement and recess areas are also found to be greater than the static contact conditions and thus result in low fatigue life, particularly at high speeds. The tip relief of the teeth is introduced to decrease the stresses on these points and improve their initiation fatigue life. • The surface and subsurface stresses of gear teeth are investigated using Hertzian theory and finite element method. • Finite element dynamics analysis is used to obtain the realistic description of a stress cyclic loading of a material point in meshing gears. • The effects of friction and speeds on stress cycles and fatigue lives of gears are studied.

Vibration Response Analysis of a Geared Rotor System Considering the Tip Relief

Considering the tip relief, a finite element model(FEM) of a spur gear pair in mesh is built by ANSYS software. Time-varying mesh stiffness and static transmission error with different amounts of tip relief are calculated based on the FEM. Then a finite element model of a geared rotor system is developed by considering the effects of the time-varying mesh stiffness and static transmission error, and the effect of the tip relief on the system vibration response is analyzed. The results show that as the amount of the tip relief on the gear increases, the saltation of the time-varying mesh stiffness and static transmission error decreases at the position of approach action and transition mesh region from the single-tooth to the double-tooth. The vibration amplitude significantly decreases at certain speeds, but it has an increase tendency in the vicinity of some critical speeds. A resonance peak appears when the gear mesh frequency is equal to the natural frequency or its fractional frequency; however, some resonance peaks corresponding to some fractional frequencies disappear at some amounts of the tip relief.

Effects of tip relief on vibration responses of a geared rotor system

Considering tip relief, a finite element model of a spur gear pair in mesh is established by ANSYS software. Time-varying mesh stiffness under different amounts of tip relief is calculated based on the finite element model. Then, a finite element model of a geared rotor system is developed by MATLAB software considering the effects of time-varying mesh stiffness and constant load torque. Emphasis is given to the effects of tip relief on the lateral–torsional coupling vibration responses of the system. The results show that as the amount of tip relief increases, the saltation of time-varying mesh stiffness reduces at the position of approach action and transition mesh region from the single tooth to double tooth. A number of primary resonances and some super-harmonic of gears 1 and 2 are excited by time-varying mesh stiffness in amplitude frequency responses. As the amount of tip relief increases, some super-harmonic responses change due to the variation in the higher frequency components of time-varying mesh stiffness. After tip relief, the vibration and meshing force decrease obviously at lower mesh frequency range except at some resonance frequencies; however, tip relief is not effective in reducing the vibration at higher mesh frequency range. The amplitude fluctuation of the vibration acceleration reduces evidently after considering tip relief, which is not remarkable with the increase of meshing frequency.

Authors’ Closure to “Discussion of ‘Modeling and Analysis of the Meshing Losses of Involute Spur Gears in High-Speed and High-Load Conditions’” (2013, ASME J. Tribol., 135, p. 011504)

Authors’ Closure to “Discussion of ‘Modeling and Analysis of the Meshing Losses of Involute Spur Gears in High-Speed and High-Load Conditions’” (2013, ASME J. Tribol., 135, p. 011504)

A Finite Element Approach to Dynamic Stresses of Helical Gear Pairs Considering Tip Relief and Crowning Modifications

A dynamic finite element (FE) approach to contact and fillet bending stresses of helical gear pairs (HGPs) is presented. Using derived tooth profiles, high quality elements of HGPs can be efficiently constructed. The resulted maximum stresses of elements on teeth are 3D illustrated. Design of relief and profile modifications is also condisered. The effect of tooth modifications on HGP dynamic responses including misalignment errors is discussed. It shows adequate modification of tip relief and crowning can reduce dynamic stress peaks of HGPs.

The Design on the Improvement of the Electric Scooptram’s Cable Arrangement Device

Proceeding with eliminating or reducing the faults occurring during the operation of the cable arrangement device for electric scooptrams, this article analyses the fault causes, makes analysis and calculations on the tip relief radius of the screw thread, the shape and abrasive resistance of the spindle shaped block, puts forward the measures on improving the abrasive resistance of the spindle shaped block and meets the operational need of the cable arrangement device.

Improvement and Experimental Research on High-Pressure Gear Pump Based on Volumetric Efficiency

Based on the basic structure of typical high-pressure gear pump, a new kind of high-pressure gear pump was designed and applied in water hydraulic transmission system. In this design, the floating plate of typical gear pump is ceramiclized to improve its wear-resisting property; the balance chamber was used to brace and lubricate the axle. Furthermore, the radial unbalanced force induced by the pressure difference of input and output is balanced by the structure of balance chamber. The dynamic characteristic of gear pump is improved and the axel wear is reduced. By using tip relief of tooth flank profile modification, the leakage rate of gear flank is effectively reduced, and the volume efficiency is improved.

Aeroelastic Analysis of a Hingeless Rotor Using a Dynamic Wake Model

Aeroelastic Analysis of a Hingeless Rotor Using a Dynamic Wake Model

An investigation on the wear behaviour of dissimilar polymer gear engagements

Following an interesting observation reported in the Wear of Materials 2009 by the present authors [1], the current paper will present an extensive investigation of dissimilar polymer gear contact, friction and wear behaviour. The unique polymer gear test rig employed will be briefly introduced. The most interesting observation from the experimental work is the significantly different wear behaviour when running acetal against nylon gears, especially the low wear rate when the acetal gear is the driver. To understand the interesting behaviour, detailed modelling work has been carried out to investigate the mechanisms of dissimilar gear engagements as well as which one is the driver. The advanced non-linear finite element method has been employed to simulate the gear tooth contact. It has been found that the gear contact force during the access process is higher than that in the recess process. Further work has been carried out on the high performance PEEK gear contacts, i.e. PEEK against steel, steel against PEEK and PEEK against PEEK. To improve the high friction and wear of the gear tip, a micron geometry modification method, tip relief, has been employed and significant frictional contact force reduction has been achieved.

Effects of flank deviation on load distributions for helical gear

Flank deviation is one of the important factors that greatly affect helical gear strength. A qualitative analysis is performed using finite element method (FEM) for the effects of flank deviation on load distributions for helical gear based on ANSI/AGMA ISO 1328-1 (standard for cylindrical gears — ISO System of Accuracy — Part 1: Definitions and Allowable Values of Deviations Relevant to Corresponding Flanks of Gear Teeth). To analyze the effects of flank deviation, tooth contact analysis (TCA) is developed and load distributions of helical gears with flank deviation are presented. Load distributions in contact lines are derived and compared to each other under grade 5 and 7 after taking five types of flank deviation, including single pitch deviation, profile form deviation, profile slope deviation and helix form deviation as well as helix slope deviation, into account. It is found that the effects of individual flank deviation on load distribution have the superposition property. Flank crowning and tip relief corrections must be carefully regarded in the design process because of the effects of flank deviation on load distributions.

Particle Swarm Optimization as an Efficient Computational Method in order to Minimize Vibrations of Multimesh Gears Transmission

The aim of this work is to present the great performance of the numerical algorithm of Particle Swarm Optimization applied to find the best teeth modifications for multimesh helical gears, which are crucial for the static transmission error (STE). Indeed, STE fluctuation is the main source of vibrations and noise radiated by the geared transmission system. The microgeometrical parameters studied for each toothed wheel are the crowning, tip reliefs and start diameters for these reliefs. Minimization of added up STE amplitudes on the idler gear of a three‐gear cascade is then performed using the Particle Swarm Optimization. Finally, robustness of the solutions towards manufacturing errors and applied torque is analyzed by the Particle Swarm algorithm to access to the deterioration capacity of the tested solution.

Prevention of helical gear tooth damage in wind turbine generator: A case study

The transmission error between the driving and driven gears originating because of manufacturing error or misalignment in the gearbox assembly causes noise and vibrations during the functioning of the gearbox. This research article discusses a novel method to prevent tooth damage in the helical gear due to transmission error by providing tip relief on the gear tooth and introducing a combination of epi-cycloid and involute profiles called composite profile for the gear tooth. Analysis is carried out using finite-element analysis package for the existing involute as well as the modified composite helical gear pair to evaluate the performance. The study reveals that the modified design (tip relief with composite profile) is superior to the existing involute gear for windmill applications because the wind turbine generators are subjected to fluctuating wind force, sudden grid drops, failure of pitching, braking, etc.