Polymer gears are increasingly popular for a variety of applications due to their improved performance, light weight, ease of manufacture and low cost. However, the design of polymer gears and ...predictions of their useful operating lifetimes require refinements based on a better understanding of all the influential parameters. For example, do dry and lubricated running polymer gears operating with the same tooth-root temperature and under the same load/torque experience different fatigue lifetimes? To investigate this question, the fatigue lifetimes of dry and oil-lubricated polymer/steel gear pairs were experimentally evaluated under three different loads (0.8, 1.0 and 1.2 Nm) and two different tooth-root temperatures (25 and 80 °C). For all the experimental conditions, the finite-element method was employed to gain a better insight into the observed differences. Finally, the decomposition of the loads acting on the gears was used to understand the effect of friction, which is different for dry and lubricated conditions, and changes direction before and after the pitch point. The lower friction in the lubricated conditions results in up to 13% less maximum stress in the tooth-root, which can have a non-linear effect on the polymer’s lifetime, resulting in a 2–5.2-times-longer fatigue life compared to dry-running gears under the same load/torque and temperature.
The mechanical properties of polymer gear transmissions are dependent on the operating temperature. Therefore, the prediction of the temperature of polymer gears is an important step during the ...design process. In this regard, analytical methods provide simple equations to predict the bulk temperature, but its applicability is limited by the underlying theory.
In this work, a detailed background of the theoretical models that affect the temperature rise phenomena of polymer gears is provided. The methods suggested by Hachmann (and its implementation on VDI 2736 standard), Takanashi and Mao are derived from this common theoretical background. The common points, strengths and limitations of the methods are provided.
The methods are illustrated with a variety of numerical examples and compared to reference experimental results. This comparison allowed us to draw some conclusions, to provide recommendations for the application of these methods, and identify potential measures of improving their results.
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•Review of theoretical models that rule the temperature rise phenomena of polymer gears.•Hachmann, Takanashi and Mao methods are explained.•The common points, strengths and limitations of these methods are identified.•The methods are compared to reference experimental results.
This article presents the results of experiments and finite element analysis on a hybrid polymer gear concept. The study aimed to investigate the effectiveness of the hybrid gear concept by using a ...rack tooth geometry.
The results of the experiments have shown that the hybrid gear concept improves the heat evacuation from the flank and root regions, potentially increasing the load-carrying capacity. Additionally, the results of the experiments were compared with those obtained from the finite element analysis to validate the numerical model. The results showed that the hybrid polymer gear rack exhibited good thermal performance, and the finite element analysis accurately predicted the behaviour of the gear rack specimens. The study also analyses the influence of the interference fit on the contact pressure and thermal contact conductance in a hybrid polymer gear concept, taking into account surface roughness and temperature. It provides insights for optimizing the press fit to ensure efficient heat dissipation in practical applications.
Overall, the study provides valuable insights into the potential use of hybrid polymer–metal materials in gear applications and supports the validity of the hybrid gear concept.
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Polymer gears have long been used on power transmissions with the fundamental durability data, including fatigue S‐N curves, yielding important data informing reliable and compact designs. This paper ...proposed a prediction method for polyformaldehyde (POM) gear fatigue life based on the innovative WGAN‐XGBoost algorithm. The findings generated herein revealed that the proposed method performs well in terms of prediction accuracy. The predicted fatigue lives, analyzed under different loading conditions, were within 1.5 times dispersion band compared with experimental results. Furthermore, based upon the enhanced fatigue dataset, a thermo‐mechanical coupled prediction formula for POM gear contact fatigue life was proposed. These findings offered a new approach for high‐power density design of polymer gears.
Highlights
A prediction method for POM gear fatigue life based on the WGAN‐XGBoost is proposed.
A thermo‐mechanical coupled fatigue life prediction formula for POM gears is proposed.
The method could shorten the sample size by 25% with the error band within 1.5.
Polymer gears are light and corrosion resistant， which can reduce noise and improve economic benefits. Correspondingly， polymer gear teeth are weaker than metal ones， so asymmetric design is adopted ...to improve the strength of polymer gear. In order to investigate the elastohydrodynamic characteristics of asymmetric polymer gears， analysis of transient elastohydrodynamic lubrication of asymmetric polymer gears is carried out under water lubrication by using the multi-grid method. The water film pressure and thickness of asymmetric gear are compared with that of traditional symmetric gear. The influence of changing gear operating condition and considering gear tooth surface roughness on gear elastohydrodynamic lubrication analysis is studied. The results show that the elastohydrodynamic performance of gears can be effectively improved by asymmetric design. The pressure and film thickness of the lubrication film are greatly affected by rotational velocity and load. The roughness has a negative effect on elastohy
The interaction of a polymer-steel spur gear pair is naturally prone to cause wear of the softer polymer material. Experimental equipment was therefore designed and constructed to run a polymer-steel ...spur gear pair with sufficiently accurate instrumentation such that the load and speed could be measured under a range of operating conditions. Plastic deformation features on the polymer teeth surface were observed through scanning electron microscopy and these are considered to be the primary sources of polymer gear wear during service. The wear mechanism is discussed and models are presented to describe the process by which it is created. This is due to the sliding/rolling under conforming contact conditions that are intrinsic to the involute spur gear pair. An iterative model based on the nonlinear properties of the polymer is presented, which shows how the material is deformed permanently and progressively under each load cycle. A second model also shows how the wear deformation features are created. Worn gear teeth were inspected and the quantity of material worn correlates well with the predicted wear volume.
•A previously unidentified wear mechanism on the tooth flank surface of Polyoxymethylene spur gears is presented.•The process by which the wear mechanism is initiated and develops is discussed by way of mathematical models.•A wear model is presented that predicts the volume of worn material by this wear mechanism.
Polyamide (PA6) polymer gear tremendously expanded its usage in power transmission applications. PA6 gear were engaged with different combinations of gear pairs (STEEL – PA6, PA6 – STEEL, and PA6 – ...PA6) were utilized in those applications. Normally gears are subjected to Hertzian contact stress due to their non-conformal contact and ANSYS is one of the widely used Finite Element Analysis (FEA) tool to determine the contact stress behaviour of those gears. Even though numerous 2D and 3D FEA investigation were performed to determine the gear contact stress behaviour, the occurrence of surface and subsurface stresses for different combination of gear pair was not explored especially for PA6 gears. Thus, the work attempted to study the surface and subsurface contact stress behaviour of three combination of gear pairs (STEEL – PA6, PA6 – STEEL, and PA6 – PA6) using 2D (plane stress with thickness condition) and 3D FE analysis (ANSYS APDL). The optimum mesh sizes were selected from the convergence study and further simulations were performed. From the analysis, the stress was observed maximum at the contact pitch point for 2D analysis, whereas, 3D analysis showed the maximum stress at a depth below the contact surface (subsurface stress) for all the combinations of gear pairs. Different trend pattern was obtained between the stress plot of 2D (surface stress) and 3D (subsurface stress) analysis for all the gear pairs. The variation in depth occurrence of maximum stress was observed for Steel-PA6 (0.16 mm depth), PA6-Steel (0.16 mm depth) and PA6-PA6 (0.25 mm depth) gear pairs. And, the Polymer – Polymer (PA6-PA6) gear pair exhibited higher depth occurrence compared to Steel – PA6 and PA6 – Steel gear pairs.
Asymmetric polymer gears are used in planetary gear transmission system to cater for the design requirements of compact and lightweight mechanical structure. In order to study the transient ...elastohydrodynamic lubrication characteristics of the internal meshing teeth of the asymmetric polymer planetary gear transmission, a lubrication model of internal meshing gear transmission of asymmetric polymer planetary gear is established; numerical solution and simulation analysis is completed by the multi-grid method. The similarities and differences between the internal and external meshing geometric parameters of planetary gears are compared and analyzed. The influence of gear operating conditions and different materials of asymmetric polymer planetary gear on transient elastohydrodynamic lubrication is studied. Considering the influence of thermal effect, the temperature distribution of the highest temperature rise and three special instantaneous meshing points in the asymmetric polymer planetary gear was investiga
A new methodology to predict the transient operational temperature of a polymer–steel gear pair under loaded running is presented. For the involute gear form, rolling and sliding leads to a loss of ...gear efficiency and generation of heat in the contact zone. The power dissipated is used to set the conditions for a series of rod on disc experiments. The rod-on-disc data are processed in a time averaging procedure, which allows prediction of the complete gear temperature. This is assessed with analytical and finite element models to validate the predicted temperature rise against the experimental data. The significance is that the experimental procedures may be used to assess gear thermal performance without testing full gear pairs.
•To predict transient temperatures in polymer–steel gears due to variable roll-slip.•Methodology to measure transient temperatures in polymer–steel gears.•Experiments to measure transient temperatures from steel rod on polymer disc.•Methodology to correlate measured temperatures with predicted temperatures.
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