Gear Unit Research Articles

Nonlinear behavior and energy harvesting performance of a new tunable quasi-zero stiffness system.

Energy harvesting from vibrations is a popular research topic. However, it is difficult to change the values of its dynamic stiffness characteristics during the operation of device. This paper analyzes the nonlinear dynamical behavior and energy harvesting performance of an energy harvesting device with a gear unit and an inertial amplifier. The Melnikov method is used to discriminate the chaos behavior of the system and is illustrated by numerical simulations. Chaotic dynamics analysis provides a simplified analytical idea that offers more insight into the performance of this energy harvesting device. In addition, the basins of attraction of the coexistence solution of the system are plotted, and the trajectory and energy harvesting efficiency of the system are analyzed for changes in the initial value. The results show that the device has the convenience to change the form and efficiency of system energy harvesting. The theory of Melnikov functions recognizes the presence of chaos and can provide solutions for the parameterization of the system. The choice of initial value greatly affects the energy harvesting efficiency.

Predictive residual stress analysis in gear units: an artificial intelligence approach based on finite element data

Determining residual stresses is essential for ensuring the safety and longevity of gear components. Traditional methods, such as analytical, numerical, and experimental approaches, are often costly, time-consuming, and sometimes destructive. This study proposes a new method to predict residual stresses in gear units using artificial intelligence based on data from finite element analysis. To achieve this, a commercial finite element tool models the heat treatment and carburization processes, grounded in thermomechanical metallurgical physics. The residual stresses obtained from finite element analysis are then compared to the ones from experiment using deep hole drilling approach. This is followed by a sensitivity analysis. Next, a specific class of gearbox component geometries and the computed stress fields are utilized to train artificial neural networks. The performance of the artificial neural networks approach is compared to that of two different machine learning regression methods. It has been concluded that this technique successfully anticipates residual stresses in components with scaled geometries and similar heat treatment steps, outperforming the two regression models in accuracy and efficiency. Importantly, it achieves this with incomparable, significantly less computation time compared to standard finite element analysis.

A method to develop a high-fidelity gearbox thermal model based on limited temperature measurements

This paper presents a method to create a high-fidelity gearbox thermal model. A hybrid analytical-empirical model is presented, it is based on the thermal network approach and experiments are used to determine some unknown parameters of the model. A test campaign was led on a four stages helical gear unit and consisted of cooling measurements, no-load tests and loaded tests. These experiments were performed under different rotational speeds and loads. The results show that the developed thermal model provides an accurate prediction of the thermal behavior of different components of the gearbox (namely rolling element bearings and oil) by only using few thermal sensors. These results are corroborated by power losses measurements which demonstrate that the model can estimate the gear unit efficiency.

Enhanced Dendrite Resistance in Reversible Electrochemical Pneumatic Batteries with Nanoimprinted Nanowire Anodes for Jamming Robots

Traditional electric robots often rely on heavy gear units or expensive force–torque sensors, whereas pneumatic robots offer a cost-effective and simple alternative. However, their dependence on noisy and bulky pneumatic systems, such as compressed air technology, limits their portability and adaptability. To overcome these challenges, we have developed a reversible electrochemical pneumatic battery (REPB) that is compact, noise-free, energy-efficient, and portable. This innovative REPB, principled by the electrochemical redox reactions of zinc–air batteries, can simultaneously supply both electric and pneumatic power, either positive or negative pressure. Its modular, multi-stack structure allows for the easy customization of power output and capacity to suit various applications. We demonstrate the utility of REPB through its application in jamming robots, such as a novel soft yet robust gripper that merges the strengths of hard and soft grippers, enabling universal robotic gripping. This work presents a groundbreaking approach to powering devices that require pneumatic support.

Influence of Gear Eccentricity with Non-Parallel Axis on the Dynamic Behaviour of a Gear Unit Using a Gear Slice Model with 26 Degrees of Freedom

Influence of Gear Eccentricity with Non-Parallel Axis on the Dynamic Behaviour of a Gear Unit Using a Gear Slice Model with 26 Degrees of Freedom

Spike Device with Worm Gear Unit for Driving Wheels to Improve the Traction Performance of Compact Tractors on Grass Plots

In general, energy loss reduction via the interaction of tires with the ground improves tractor traction performance when a drawbar pull is generated. This paper is examines the driving wheels with steel spikes for a tractor equipped with modern radial tires. An improved design of the spike device that allows for the change between an active and inactive position of the spikes is presented. The traction performance of a compact articulated tractor with the spike device was tested on a grass plot with two soil moisture contents (SMC). The highest difference in the drawbar pull in the range from 14.2% to 40.5% and from 17.1% to 36.8% was reached by the spikes in the active position in comparison with the tires without spikes, which were at the slip range from 45% to 5% in the case of the low SMC when the test tractor was in the 3rd and 1st gear. The motion resistance difference between the spikes in the active position and the tires without spikes was 11.8% and 2.5% at the low and medium SMC, respectively. At the low and medium SMC, the highest tractive efficiency of 0.765 (0.721) and 0.757 (0.731) was reached by the spikes in the active position when the test tractor was in the 1st (3rd) gear in comparison with 0.736 (0.7) and 0.723 (0.708) in the case of the tires without spikes. The results indicated that the spike device allowed for the improvement of tractor tractive performance.

Face gear drives: Nominal contact stress calculation for flank load carrying capacity evaluation

Face gear drives are angular gear units in which an involute pinion meshes with a face gear wheel. Spur and helical face gear drives are possible with or without center offset. Face gear drives can be manufactured on conventional gear cutting machines. Furthermore, the pinion is free to move axially and such displacements have no effect on the contact pattern. This makes them a promising gearing for various applications. Due to the lack of established calculation standards, the design of face gear drives is a challenge and often results in oversizing or early failures. This may also be why face gear drives have not yet established themselves in power transmissions. Instead, the main application can be found in kinematic/auxiliary drives. In this paper, two methods for contact stress calculation for face gear drives with any configuration between helix angle and center offset are developed. Calculation examples compare the two methods and confirm the applicability. Overall, this study provides a new standard-capable easy-to-program calculation method for the contact stress based on existing standards for cylindrical gears.

Optimization of energy efficiency and NVH behaviour of a helical gear unit

The goal of this study is to perform a multi-objective optimization of a gear unit in order to improve its performance in terms of mechanical power losses, gear dynamics and equivalent sound power radiated by the housing. All these key performance indicators are closely related to the gear macro- and micro-geometry parameters. Decision variables chosen are the helix and pressure angles as macro-geometry parameters, and the amount and dimensionless roll length of tip relief as micro-geometry parameters corresponding to gear profile modifications. The multi-objective optimization is carried out under geometric and load capacity constraints using the evolutionary NSGA-II algorithm. Various results, observed in the form of 3D Pareto front confirm that improvements in energy efficiency and vibroacoustic performance are antagonistic. Nevertheless, a significant decrease of mechanical power losses is possible without degrading the vibroacoustic performance much. Otherwise, the correlation between the gear dynamic response and the equivalent radiated sound power (ERP) is partial. The minimization of the equivalent sound power radiated by the housing is not equivalent to the minimization of the gear transmission error fluctuation. These results underline the interest of modelling the whole gear unit to optimize its efficiency and NVH behaviour.

Jig-less Assembly of a Gear Unit with a Versatile Hand Equipped with Functions for Reorientation and Alignment of a Shaft-shaped Part

Jig-less Assembly of a Gear Unit with a Versatile Hand Equipped with Functions for Reorientation and Alignment of a Shaft-shaped Part

Comparison of performance between tapered and cylindrical roller bearings for pinion of gear unit subjected to rotation test

Tapered roller bearings are often used to support pinions in gear units of electric trains. On the other hand, recently, the application of cylindrical roller bearings with ribs has also been proposed, in which the internal clearance changes little depending on the operating conditions. This study aims to elucidate the effect of differences in just these two types of pinion bearings on the performance of gear units and thereby verify the applicability of cylindrical roller bearings with ribs to railway gear units. Tapered roller bearings and cylindrical roller bearings with ribs of the same dimensions were subjected to rotational tests in the same gear unit. The results showed that the effects of the atmospheric temperature on the maximum temperature, the maximum rate of temperature rise, and the torque of the bearings were not significantly different between the tapered roller bearings and the cylindrical roller bearings with ribs. As the atmospheric temperature decreases, the maximum temperature decreases, and the maximum rate of temperature rise and the torque increase. On the other hand, the endplay values had a significant effect on these values in the tapered roller bearings, while they had little effect on the cylindrical roller bearings with ribs.

Features of Wear of Gears of Agricultural Machinery

Abstract The paper presents data on the resource and wear of the gears of agricultural tractor transmissions, on the basis of which the research problem and the novelty of the proposed methodology are formulated, based on the development and application of the stress state model of the gear, taking into account surface hardening. The methodology and calculation scheme for determining the power parameters of gearing are described in detail. In this case, the dependences and results of previous studies in the field of increasing the durability and reducing the wear of gears of transmission elements of vehicles of various functional purposes were used. To achieve this goal, the mathematical models of the stress state of gears are constructed without the presence of an external diffusion hardening coating and with a coating. Based on the simulation of the process of interaction of rubbing pairs of gears, the distribution of stresses in the contact zone over the surface layer of non-hardened and cemented to a depth of 1 mm gears, as well as the dependence of deflection on the thickness of the cemented layer and the deformation of the cemented layer during operation was established. Considering the research results given in literature, as well as those obtained on the basis of our own research, it should be noted that the analysis of gear stress state is an important direction in the study of the durability of gear units, the entire gearbox, and other gears of tractor transmissions and automotive technology at the present time. At the same time, the actual task is to establish the ratios of the allowable wear of gears and the limiting value of displacement of the centre distance, taking into account changes in the stress state scheme when using various types of coatings.

Features of hydrodynamic calculation of highly loaded plain bearings of heavy ship’s gears

Despite the high level of modern vessel engineering development, there are a number of unresolved design and technological problems, the most urgent of which is the issue of unification of the main components and assemblies of the vessel. At the same time, an important and unresolved task is to create a unified image of the ship’s reverse gear for the needs of the domestic civilian fleet and navy. The object of study is highly loaded bimetallic plain bearings, which are elements of the “heavy” marine reverse gears of a new generation. As part of the work, a hydrodynamic calculation that refines the parameters of the plain bearings of a highly loaded marine transmission at the stage of a prototype production is performed. The applicability of the State Standard ISO 7902 methodology to the products under consideration is assessed, as well as the approximation of the performance characteristics of bearings using interpolation of two variables function is performed. The rationale for the coverage angle and the location of the pockets for supplying lubrication of bearings taking into account the thermal and viscous properties of the oil is presented. Calculations of the parameters of the critical thickness of the lubricating layer, the maximum allowable specific load and the maximum allowable temperature of bearings are performed. Based on the results of the calculations, an additional assessment for the compliance of bearings with the requirements of State Standard ISO 7902 in terms of bearing capacity and stability parameters is carried out. The comparison of the obtained results with the data of the preliminary calculation performed at the stage of the technical project is given. It is revealed that when calculating dynamically loaded plain bearings, it is necessary to take into account a number of additional factors, namely the magnitude of the relative eccentricity and relative clearance. The risks of bearings failure in the process of dynamic loading are determined. The result of the work is the correction of the geometric parameters of the plain bearings of the marine reverse gear unit in order to increase its reliability and the overhaul interval.

Design and Analysis of a Novel Wave Energy Harvester

A novel wave energy harvester (WEH) that can recover energy in the direction of heave, sway, and surge is designed under the background of low recovery efficiency and complex installation of the existing wave energy harvester. The harvester consisted of four main components: energy input module, energy transfer module, energy conversion module, and energy store module. In the paper, to convert more wave energy into electrical energy and improve the energy conversion efficiency of WEH, the motion transfer module is divided into vertical and horizontal motion transfer modules, which are used to harvest vertical and horizontal wave energy, respectively. The vertical motion transfer module combined with the ball screw structure, planetary gear structure, and one-way gear units ensure the generator has high speed. The horizontal motion transfer module is mainly composed of three uniformly distributed one-way gear units, ensuring collect the wave energy in all horizontal directions. The dynamic model of the harvester is established, and the simulation experiment is carried out under wave conditions with periods of 2 s, 2.5 s, and 3 s, respectively. The simulation results show that when the wave period is 2[Formula: see text]s, 2.5 s, and 3 s, the corresponding energy conversion efficiency of the WEH is 66.7%, 60.9%, and 57.1%, respectively. The proposed study provides a theoretical reference for modeling similar WEHs and can effectively balance energy supply and demand and further support the global agenda of UN-2030 for sustainable development, especially SDG-7.

Impact of Hermodice carunculata (Pallas, 1766) (Polychaeta: Amphinomidae) on artisanal fishery: A case study from the Mediterranean sea

Invasive species can cause severe economic damages, ecosystem alterations, and can even threat human health. In the global warming scenario, which can act as a driving force for the expansion of thermophilic species, we investigated for the first time the economic damage caused by the invasive bearded fireworm, Hermodice carunculata, to artisanal longline fishery in the Mediterranean Sea. We focused on bottom longline fishery targeting the highly prized white seabream Diplodus sargus, investigating catch composition of the fishing gear and Catch Per Unit Effort (CPUE) of species caught, with particular emphasis on the economic damage caused by the bearded fireworm, H. carunculata, in relation to water temperature. Our results clearly indicated direct and indirect economic damage to fishing activities practiced in the southeastern coast of Sicily (Ionian Sea). Type and extent of the damage caused by the invasive worm (H. carunculata) were discussed in relation to temporal scale and overall yields obtained by this traditional artisanal fishery, and some solutions are proposed. However, the actual situation requires special attention because it is expected to worsen in the context of the global warming future scenarios, such that further studies are urgently needed.

A New Experimental Methodology to Study Convective Heat Transfer in Oil Jet Lubricated Gear Units

The purpose of this study is to generate some experimental data associated with the thermal heat exchange between an oil jet flow and a rotating gear. To this end, a specific test bench was designed. The principle of this test bench is to inject oil heated to a temperature of about 80 °C onto a rotating test sample at ambient temperature. Temperature measurements of the oil via injection nozzles and the rotating component allow the determination of the heat flow between these elements using a numerical method developed to this end. This test rig enables the study of the parameters that may affect heat exchange, such as oil flow rate and injection temperature, nozzle geometry and position, gear rotational speed and tooth geometry, or oil characteristics. In this study, three of these parameters were investigated, namely the test sample rotational speed, the oil flow rate, and the oil jet velocity. The experiments were conducted on an aluminum disc and spur gear. Subsequently, the experimental results were compared with existing models that represent the convective exchanges between oil and a gear. Some discrepancies between existing models and experimental results appear at high rotational speeds, underlining that the convective heat transfer does not always increase with this parameter.

The model and design of a Spring-Embedded Planetary Dual-Motor Actuator to reduce energy losses

The electrification of many mobile applications such as wearable robots has led to the need for carrying batteries to store electrical energy. However, low-efficient actuators require larger batteries that have to be carried along, which limits the range and performance of such devices. In addition, collaborating with robots require safe cobots and actuators. To address this challenge, parallel and series elastic actuators have been adopted in many applications to increase safety and energy efficiency. Meanwhile, some industries, including the automotive industry, have put much research effort into dual motor actuation to decrease the energy consumption of the overall drivetrain.In this paper, we introduce a Spring-Embedded Planetary Dual-Motor Actuator (SEP-DMA) which combines both technologies using a planetary gear unit and a spring. We derive and validate a dynamic model for all possible configurations and discuss their operating modes, including active and passive actuation. To demonstrate the potential of the actuator, we compare it with a traditional stiff actuator consisting of a gearbox and electric motor. The former shows a 40% decrease in the overall energy consumption for a standard task of lifting and oscillating a mass.

Crossed helical gears—simulative studies and experimental results on non-involute geometries

Crossed helical gear units generally consist of a steel worm and a plastic helical gear with an axis crossing angle. Due to the high transmission ratio in a small installation space, they are used in auxiliary and actuating gears such as in window regulators, assembly lines, household appliances and positioning tasks. This paper deals with a calculation approach for crossed helical gears to include non-involute flank geometries for new and optimized gearboxes. The geometry derivation for general flank contours based on a polynomial and extends the geometric possibilities beyond the special case of the involute form. The use of principal curvatures and principal curvature directions to describe freely curved surface geometries enables the calculation of flank pressures, efficiency and sliding paths in the entire contact area. Previous studies confirmed the advantages in the mentioned load characteristics for geometries deviating from the involute. Furthermore, parameter studies show the influences of the individual design parameters and demonstrate the effects on operating behavior, with those a design recommendation for crossed helical gear units with general flank geometries can be created. ZC and ZC‑S geometries are used as calculation examples. With regard to the use of these new geometries in applications, manufacturing is a crucial aspect. Grinding disc parameters as well as a three-roll size to control the worm manufacturing for general flank geometries are necessary and described below. In addition to the theoretical calculation, a ZC crossed helical gear geometry was designed, manufactured and compared to a ZI reference gear in test rigs. This confirmed the advantages in load-carrying capacity and efficiency increase resulting from the calculation and proved the benefits.

Experimental Investigation on Churning Power Loss of Splash Lubricated Worm Gear

Churning power losses are a complex phenomenon that produces critical power losses when considering the splash lubrication of gear units. This article describes the method to investigate the churning power loss in a worm gearbox. A particular test rig was designed and fabricated to experiment on single start worm gear incompletely submerged in an oil bath. The direct torque measurement technique was used to determine the churning power losses. Experiments have been conducted to determine the impact of a variety of operating conditions on churning power losses, including worm speeds, gear immersion depth, lubricant temperatures, and lubricant type (mineral and synthetic). It was found that the churning losses were significantly affected by the worm shaft orientation, speed of gear, and the depth of immersion (static head). The lubricant's temperature is more essential than the type of lubricant in terms of churning power loss.

Simulation Study on the Tribological Characteristics in the Meshing Contact in the Context of the Load Carrying Capacity Calculation of Internal Gears with Unbalanced Sliding Conditions

Planetary gearboxes are characterized by a high power density and a compact design with coaxial in- and output. Consequently, planetary gear units are frequently used in many practical applications, e.g. in wind energy and industrial transmission systems as well as in automotive applications such as automatic transmissions. As a result of the scaling-up of the required system power, the risk of flank damages increased during the last decade. Certain damage types, such as pitting and micropitting, occur predominantly in contact areas of negative specific sliding on the tooth flank surface. Unlike external gears, internal gears offer the possibility of positioning the pitch point C outside of the active profile. Depending on the gear design, this allows a complete avoidance of negative specific sliding either on the planet or on the ring gear. In contrast, the corresponding gear is subjected to negative specific sliding only. It can be assumed that the lifetime regarding flank damages of each meshing partner can be affected by different positions of the pitch point and the resulting differences in the specific sliding, which allows an optimization of the full gear system, taking into account e.g. the load carrying capacity reserves for different material pairings. It is to be noted that such gear designs are already part of some practical applications.However, the existing analytical approaches within standardized load carrying capacity calculation methods are typically based on investigations considering external gears with balanced sliding conditions. Systematic results on internal gear designs with pitch point positioned outside of the active profile are not available.Within this paper, extended theoretical studies on the tribological characteristics of different internal gear designs are presented. Therefore, a reference geometry with balanced sliding conditions is compared to internal gears with pitch point below respectively above the active profile. The focus of the studies is the analysis of the lubricant film thickness and the contact temperature in the meshing contact. Referring to this, a high-order TEHL contact simulation model was used. The results of the numerical analysis with the FZG calculation software TriboMesh are compared to different analytical approaches in the context of the calculation of load carrying capacity to derive recommendations for the design of internal gears.

Analysis of the Gear Pump’s Acoustic Properties Taking into Account the Classification of Induction Trees

This paper presents an analysis of selected acoustic properties of gear pumps. For this purpose, the characteristics of selected types of displacement pumps—gear pumps—are discussed, as well as discrete methods of identification and classification of acoustic signals. The basic assumptions of noise analysis in reverberation chambers are discussed, and an analysis of the distribution of measurement points using decision trees and statistical analysis of measured noise levels was conducted. The object for the conducted research was a gear pump with a undercut tooth profile developed by Wytwórnia Pomp Zębatych Sp. z o.o. in Wrocław. Our own research indicates that the acoustic performance of gear units depends on a number of factors, including, in particular, the technology and quality of manufacture and the geometric parameters of the toothing. The aim of the analyses presented in this paper was to determine which of the microphones has the most important impact on the level of determined measured noise generated in the acoustic chamber. The paper presents an analysis aimed at ranking the importance of eight measurement points in which the microphones are located. To this end, induction trees were developed, and a statistical analysis of the measurement results obtained for selected frequency and sound pressure ranges was prepared. The analysis made it possible to optimize the arrangement of microphones in the chamber without unnecessary analysis of each of the microphones separately.