Tooth Modification Research Articles

Nonlinear dynamic modeling and analysis of spur gear based on gear compatibility conditions

In the traditional gear dynamic model, the mesh stiffness is obtained under static load. When the mesh stiffness changes greatly with the change of load, the traditional dynamic model is not accurate enough to analyze the gear system. Therefore, this paper proposes a new dynamic model with a more realistic dynamic mesh force based on gear compatibility conditions. The proposed dynamic mesh force model is applicable to the gear system with and without tooth modification and verified by the finite element method. Afterward, the paper compares the differences in the dynamic responses between the proposed model and the traditional model. The results indicate the dynamic responses of the proposed model are generally consistent with those of the traditional model for the standard involute gear system. For the lead crown gear system, compared with the proposed model, the traditional model will lose important nonlinear characteristics in the high-speed area. At most speeds, the amplitudes of vibration and dynamic mesh force of the proposed model are greater than that of the traditional model, especially in the bifurcation, quasi-periodic and chaotic regions.

Effect of Different Surface Modifications of Acrylic Teeth and Thermocycling on Shear Bond Strength to Polycarbonate Denture Base Material.

During prosthodontic clinical practice, the most commonly reported type of failure is the debonding of teeth to the denture base. Incompatible surface conditions at the tooth/denture base interface result in a lack of bonding. This study aimed to study the influence of different surface modifications of acrylic teeth and thermocycling on shear bond strength to polycarbonate denture base material. Eighty cylinder-shaped samples were fabricated. The tested samples were divided into 4 groups (n = 20). Group A represents the control group, group B represents the mechanical modification of the tooth, while group C and group D represent the chemical treatment of the tooth with ethyl acetate and bonding agent, respectively. Each group was further subdivided into 2 categories depending on the thermocycling procedure (N = 10). All samples were tested for shear bond strength tests. A computer-controlled universal testing machine performed the shear bond test at a 0.5 mm/min crosshead speed. Three-way ANOVA (P=0.05) was used for the statistical analysis of the data. Results show that shear bond strength was significantly affected by the surface treatment, whether it is mechanical or chemical (P ≤ 0.01) (B > D > C) compared with a control group (A). However, thermocycling has a nonsignificant decrease in the bond strength values in all experimental groups (P > 0.05) (B > D > C > A). The mechanical treatment by creating retentive holes (B) provides better results than the chemical surface treatment with a bonding agent and ethyl acetate (D and C, respectively). This study concluded that various surface conditioning methods affect the bonding strength of acrylic teeth and polycarbonate denture base material with no effect of thermocycling.

Calculation method of mesh stiffness for helical gear pair with manufacturing errors, assembly errors and tooth modifications

Calculation method of mesh stiffness for helical gear pair with manufacturing errors, assembly errors and tooth modifications

A Novel Cutting Method for Face-Hobbed Spiral Bevel Gears Based on Tool Path Modification

A novel tooth surface design method of face-hobbed spiral bevel gears is proposed, which utilizes a solid cutter without axis tilting through tool path control combining with optimized cutter blade profile to control tooth contact patterns and realize tooth lengthwise chamfering. Firstly, a gear tooth surface generating plan of tool path controlling actively is developed, the mathematical model of the tool path is built, and the equations are given in detail, the determination method of all control parameters is also described. Next, the tooth surface functions of generating gear and machined gear are established based on a mathematic model of the traditional cradle machine tool. Then, the machine setting is also given in concise equations. Finally, the tooth contact analysis is also conducted for a specific gear pair to validate the validity and the reasonability of the new tooth modification method.

Suitable Design of Tooth Profile Modification for Noise Reduction in Spur Gear Pump

This study has carried out for noise reduction of spur gear pump. The previous report was published at JSME 2021 annual conference, which reported the noise source analyses result of test gear pump. According to the report, it was concluded that the most effective way to reduce noise was to reduce the meshing vibration of gears. Therefore, the authors aimed to reduce gear meshing vibration by modifying the tooth profile. For this purpose, the effect of tooth profile modification on the tooth root stress form was investigated. Then, the appropriate tooth modification amount was decided by the tooth root stress calculation. Furthermore, several kind of function which determines the shape of tooth profile modification has applied to the calculation to make clear the most effective shape of tooth profile modification for noise reduction. The major conclusions of this research are as follows; (1) The most effective value to tooth root stress waveform was depth of tooth profile modification. (2)The type of functions which determine the shape of tooth profile modification was less effective to tooth root stress waveform.

Increasing the load capacity of a gear transmission under skew conditions by reducing contact stresses by means of longitudinal modification of the teeth

A method was developed and dependencies were obtained for determining the parameters of the longitudinal modification of the gear wheels teeth. Longitudinal modification is an effective way to reduce contact stresses in case of misalignment of axes in gear mechanisms, increases the load capacity of the gear transmission. Examples of calculation are given. Keywords: gear transmission, contact spot, axle misalignment, uneven load distribution, longitudinal modification, barrel shape. filnahat7@mail.ru

A vectorial modification methodology based on an efficient and accurate cycloid tooth profile model

A cycloid gear is the central component of a rotate vector reducer, and cycloid profile design has served as the basis for manufacturing modification research. The previous cycloid tooth profile equations are complicated to derive and not efficient to calculate. Moreover, the current tooth modification method only allows for uniform correction of the overall profile. This work presents an efficient calculation and high accuracy model of the cycloid profile which is designed in dual quaternion space by introducing assembly and machining error parameters. Moreover, we propose a vectorial modification method to achieve a single-point partial modification instead of simultaneous modification of all tooth profile points. With the meshing characteristics as the optimization objective, the optimal solution of the error term is obtained by means of the response surface method, which is the maximum error tolerance in the design process. Finally, verification is carried out by the finite-element method. The new cycloid tooth profile model provides the basis for a modification vector calculation of large-scale scatter points. The synchronization of the design error tolerance maximum and tooth profile design will also effectively improve the manufacturing accuracy of the whole machine and shorten the design cycle.

Experimental investigation on the effect of misalignment on the wear failure for spline couplings

The teeth of misaligned spline couplings used in power transmission parts of helicopter and aero-engine often suffer serious abnormal wear faults during service. Through the self-made spline coupling test rig, the mechanism of misalignment on the spline coupling wear was explored. The tooth contact domain of the spline coupling with shaft misalignment is close to the addendum, and the tooth contact domain of the spline coupling with angle misalignment is mainly concentrated on the side of the tooth end. The edge contact effect becomes more serious as the amount of misalignment increases, resulting in abnormal wear at specific positions on the tooth surface. The presence of misalignment increases the vibration intensity of the spline coupling based vibration signal monitoring, which will increase the wear of the teeth. In addition, the difference in system vibration response of different misalignment types can be used to identify the misalignment failure mode of the spline coupling. It can be inferred from the characterization of wear debris that fretting wear is the cause of the failure of the misaligned spline coupling. Tooth modification, surface strengthening modification and lubrication design are necessary as potential solutions to improve the wear resistance of misaligned spline couplings.

Effects of the interval geometric deviation and crowning parameters on the automotive differential dynamics

A differential mechanism is an essential component in the majority of automotive applications. Its vitality stems from the fact that it allows a wheel-drive vehicle to take a curve safely. On the other hand, it can ratchet up the vibration in the wheel-drive vehicle due to the excessive gear tooth deflection from applied torque. Some gear tooth modifications can increase or decrease the level of vibration in the mechanism. So far, very little attention has been paid to the effects of the uncertain geometric deviation of the tooth profile and uncertain crowning parameters on the dynamic performance of the mechanism. This study aims to investigate the impacts of these uncertain parameters on the gear systems’ dynamic performance. To this end, the nonlinear interval model of the differential mechanism is proposed. The mesh stiffness for straight bevel gear is modelled through the potential energy method and slice theory, while bearing stiffness elements are calculated at each time step. A refined computational algorithm is proposed to deal with any gear system with multiple interval variables. The scanning method is used as a reference method in this paper. The main outcomes of this study are that the crowning design can slightly reduce the vibration in the mechanism, and the profile errors can increase its vibration level excessively. Besides, the results derived from the refined algorithm show similarities to those determined by the scanning method, and the study shows that the refined algorithm can handle any gear system with uncertain static or time-varying parameters.

Tooth surface modification of double-helical gears for compensation of shaft deflections

Abstract. Based on gear meshing theory, the tooth surface equation with tooth profile modification parameters is deduced, the tooth surfaces of unmodified and modified gears are constructed, the three-dimensional model of unmodified and modified double helical gear-shaft-bearing system is established and then the three-dimensional contact finite element model of double helical gear-shaft-bearing system is established and the load-bearing contact analysis of the tooth surface is carried out. The actual contact state of the tooth surfaces of double helical gears under different shaft stiffness and power transmission paths is investigated, and the influence of tooth modification parameters on the load distribution of the tooth surfaces of double helical gear pairs is studied. The results show that the tooth surface bearing the contact of the herringbone gear system has the phenomenon of partial load due to the supporting deformation, and the unmodified herringbone gear has obvious contact stress concentration. However, the phenomenon of partial load and stress concentration can be effectively improved by gear tooth modification.

MODIFICATIONS OF GEAR WHEEL TEETH OF AVIATION GEARBOXES TO INCREASE THEIR OPERATIONAL RELIABILITY AND TECHNOLOGY

The types and methods of modifications of teeth and gear wheels, which have found application in gearboxes of aircraft and helicopters, are presented. Features of geometry, parameters of different types of initial produced contours, their modifications, application and influence of various factors on improving the operational characteristics of gear drives of aviation gearboxes are considered.
 Arcuate (short and long) and short linear options for modifying the tooth profiles of aircraft gearboxes are best suited to absorb the errors of spur gears.
 There was no significant difference in the use of short and long correction for a relative decrease in temperature in the contact zone of the wheel teeth, therefore, the use of any correction of the tooth profile, with rare exceptions, turns out to be useful.
 The advantages of using increased profile angles in comparison with the standard ones used in general mechanical engineering are considered.
 Development of designs of teeth and gear wheels in aircraft gearboxes, the use of gears with teeth of an asymmetric profile, which can be considered as a cardinal modification of the tooth profiles. The use of such gears increases the strength of the teeth due to the increase in the thickness of the teeth. Unsymmetrical teeth have a large thickness at the tip, which reduces teeth chipping and due to their greater height, greater smoothness of engagement is achieved, bending and contact stresses are reduced.
 The most radical type of modification is the use of asymmetric profiles of the teeth of the wheels of aircraft gearboxes.

Dynamic loading of spur gears with linear tooth profile modification: modelling and experimental comparisons

A dynamic model of a gear pair has been developed to investigate methods of decreasing dynamic loads and analysing dynamic stresses of gears in aviation engine drives. The effect of tooth profile modification on dynamic stresses in the system, as well as the effect of main gear parameters is analysed. It is shown that high level of dynamic stresses and vibrations in gears may be caused by using standard parameters of tooth profile modification. An experimental study of the dynamics of gears with various profile modification parameters has been carried out. The paper shows the necessity of changing the approach to calculating parameters of tooth profile modification of teeth.

Designing gears with minimal effective transmission error by optimizing the parameters of tooth modification

This paper is dedicated to the development of a method for optimizing the parameters of modification of gears. An experimental study of the effectiveness of the modification, calculated according to the current standard, has been carried out. Within the framework of the project, a software has been developed that implements an algorithm for designing three-dimensional models of gears with a modified topology of contacting side surfaces, which are used for the subsequent modeling by the finite element method of the process of teeth meshing. The results obtained were used to solve the one-criterion optimization problem. As an example of using the method, the optimization of the parameters of the modification of the teeth was carried out in order to minimize the amplitude of the transmission error harmonics.

Experimental and Theoretical Investigation of Quasi-Static System Level Behavior of Planetary Gear Sets

Abstract This study presents a unique experimental methodology that synchronously measures various quasi-static responses of a simple four-planet planetary gear set, namely, planet load sharing, overall transmission error (OTE), and floating sun gear orbits. Strain gauges mounted directly on the planet pins were used to monitor the load shared among the planets, which is a crucial design criterion for durability and performance. High-precision optical encoders were used to measure the OTE of the gear set to explore its diagnostic value in identifying system errors. Radial motions of the floating sun gear, which are critical to the self-centering and load sharing behavior of the gear set, were monitored using magnetic proximity probes. The influence of various design parameters and operating conditions such as planet mesh phasing, carrier pin position errors, gear tooth modifications, and input torque on the system’s response will be investigated by performing an extensive set of experiments in a repeatable and accurate manner. Finally, these experimental results will be recreated theoretically using the static planetary load distribution model of Hu et al. (2018, “A Load Distribution Model for Planetary Gear Sets,” ASME J. Mech. Des., 140(5), p. 53302) to not only validate the model but also comprehend the measured behavior.

Lubrication characteristics of cycloid pin wheel transmission of RV reducer

In order to analyze the lubricating characteristics at different meshing points in the cycloid pin wheel transmission process, the cycloid gear teeth were discretized, combined with the kinematic analysis of the cycloid pin gear transmission and the contact analysis of the gear teeth. The progressive mesh densification method (PMD) was used to numerically solve the film thickness. The influence of the design parameters and process parameters on the lubrication characteristics was analyzed. The elastohydrodynamic lubrication and mixed lubrication characteristics at different contact points were obtained. The optimal meshing area of the cycloid gear tooth was determined, and the film thickness ratio, contact load ratio, maximum contact pressure at different points, average film thickness and roughness after contact deformation were analyzed. The conclusion of this study provides effective guidance for the research on the modification of cycloid gear teeth.

A dynamic load distribution model of planetary gear sets

This study presents, a three-dimensional dynamic load distribution model of planetary gear sets, which can capture the influence of several component and system level design variations. A numerical integration scheme is used in conjunction with an iterative elastic contact algorithm to solve the multibody dynamics problem. This approach inherently captures the mesh stiffness fluctuation, without the need for an empirical mesh stiffness formulation or transmission error excitation of the system. The unique dynamic response of the parametrically excited system under various gear mesh phasing conditions is studied using the proposed model. Influence of gear tooth modifications and carrier pin position errors on the dynamics of the gearset is explored, also a brief study to demonstrate the model's capability to capture contact non-linearities in the case of low contact ratio gear sets is included. Discussed results not only illustrate the validity and potential of the proposed dynamic model but also reinforce the need for such computationally efficient models for design purposes.

Numerical analysis of Modified tooth in Spur Gear for increasing the performance using fool proofing technology

In this work, design and analysis of spur gear tooth modification to increase the performance by using fool proofing technology. A modification has made in the tooth gear to analyse slippage, efficiency and misalignment. The CATIA software is used to create the 3D model of spur gear and ANSYS is used for numerical simulation. A fool proofing technology has been tried in this spur gear to reduce the assembly errors and misalignment in an axial direction of the shaft. One degree of freedom has been arrested in an axial direction of the shaft. A new slot has been created between the addendum circle and the pitch circle, as well as a grooved cut in the bottomland for both the driver and the driven gear, reducing gear slippage in the axial direction during dynamic loading. In the end, the spur gear’s output is improved.

Gear tolerancing for simultaneous optimization of transmission error and contact pressure

With electrification of vehicles comes an increasing demand on low noise, which for gears translates to transmission error. In this paper, static transmission error, STE, is found for a large number of manufacturing error combinations belonging to different tolerance classes, with focus on those typically used in the automotive industry. There is a lack of studies found in the scientific literature which investigate the link between STE, contact pressure, and manufacturing error tolerances. Therefore, the aim of the present study is to investigate this link. This is done by utilizing a novel simulation tool, developed by the authors, to compute STE for gear sets with pitch and profile slope errors combinations. The model uses a parametric description of the reference profile, includes tooth modifications, uses a hybrid method for compliance, and finds contact from equilibrium. The model handles contact outside the nominal line of action, including tip contact.A simplified method, with predictions based on simulated values, is shown to be accurate and suitable for estimations. Finally, STE is linked to contact pressure for better understanding of how STE and contact pressure interact as a consequence of manufacturing errors. It is shown how this can be used to optimize the gear set with respect to both STE and contact pressure simultaneously.

Increased papilla between implant and tooth with TEH use of hyaluronic acid injection: A case report

The lack of dental papilla in the anterior maxila leaves unsightly smile and the dissatisfied patient. Several surgical techniques can be performed to gain interdental papilla, but few of them are predictable. This case report shows a multidisciplinary treatment alternative to increase disabled papillae in single-tooth implant in an aesthetic region with the use of injectable hyaluronic acid. Monitoring and evaluation of results was made by clinical and photographic monitoring of the progressive increase of the papilla in millimeter measurements through computer software. After 8 applications in 5 months, prosthetic emergence profile of adjacent tooth modification, papillary inflammatory process induction, we can observe 1,0 mm papilla gain. It can be concluded that the use of injectable hyaluronic acid in association with gingival prosthetic conditioning led to increased gingival papilla between tooth and dental implant and can be considered a treatment alternative for correction of minor defects papilla. Keywords: Implant, Aesthetic area, Papilla reconstruction, Hyaluronic acid.

Tooth flank modification to reduce transmission error and mesh-in impact force in consideration of contact ratio for helical gears

In this paper, a new tooth modification method considering the contact ratio of gears and a new method for calculating the mesh-in impact force of modified helical gears are proposed. The new method for calculating the mesh-in impact force is based on tooth contact analysis and loaded tooth contact analysis. The mesh-in impact position can be calculated accurately via the new method. First, the procedures for creating the new tooth modification and the details of calculation method of the mesh-in impact force are exhibited. Second, the optimal modification of the tooth flank is achieved by solving the optimization problem. Third, a dynamic model of the gear system considering the loaded transmission error and the mesh-in impact force is used to study the dynamic characteristics. Ultimately, numerical examples are presented and the simulation results suggest that the amplitude of the loaded transmission error and the mesh-in impact force can be reduced more effectively based on the introduced new tooth modification method. And the mesh-in impact effects should not be neglected in gear dynamic analysis, regardless of whether the tooth modified or not, especially for high-speed gears.