Metal-plastic gear pairs, due to their combination of the advantages of both materials, have been widely promoted and applied in many industries. However, research on their transmission performance ...is not yet complete, especially regarding the tribological properties of metal-plastic gear pairs. The study focus on ADC12-POM gear pairs. Based on the principle of potential energy, the study considers significant elastic deformation during POM meshing, resulting in obvious off-line meshing. Consequently, the study establishes a stiffness model for ADC12-POM gear pairs with off-line meshing. Using this stiffness model and a load distribution model, to calculate the tooth surface load distribution coefficient for the gear pairs. Building upon previous research on friction coefficient models, the study develop a friction coefficient model that accounts for off-line meshing and compare it with the friction coefficient model that does not consider off-line meshing. To validate the accuracy of the friction coefficient model, the study design and create an efficiency test rig for ADC12-POM gear pairs, conducting theoretical and experimental studies on gear mesh efficiency. The study analyzes the distribution of mesh efficiency along the meshing line and its relationship with the friction coefficient. By comparing experimental measurements with theoretical calculations, the study verifies the proposed friction coefficient model, providing a theoretical basis for the study of metal-plastic gears.
•Realistic spalling geometries are obtained from fatigue experiments.•The mesh stiffness and contact stress are verified by the finite element method.•Dynamic behaviors of the single and multiple ...teeth spallings are discussed.•Simulated fault features are verified by that obtained from the experiment.
Considering the realistic spalling morphology obtained from the fatigue experiment, a novel dynamic model for spalled gear pairs is established in this paper. Loaded tooth contact analysis method is utilized to evaluate the meshing characteristics of spalled gear pairs. In order to verify the proposed method, the mesh stiffness and contact stress obtained from the proposed method are compared with those obtained from the finite element method and the method in published literature. The mesh stiffness and the non-loaded static transmission error are imported into the geared rotor dynamic model to acquire the dynamic responses. The spectrum characteristics and statistical indicators under different spalling patterns are acquired by the proposed model. A comparison between simulation and experiment is performed to verify the proposed dynamic model. The results show that the simulated fault features agree well with that obtained from the experiment, which indicates that the proposed model is a promising tool for the fault mechanism study of gears with realistic spalling patterns.
We present a new fully automatic block-decomposition algorithm for feature-preserving, strongly hex-dominant meshing, that yields results with a drastically larger percentage of hex elements than ...prior art. Our method is guided by a surface field that conforms to both surface curvature and feature lines, and exploits an ordered set of cutting loops that evenly cover the input surface, defining an arrangement of loops suitable for hex-element generation. We decompose the solid into coarse blocks by iteratively cutting it with surfaces bounded by these loops. The vast majority of the obtained blocks can be turned into hexahedral cells via simple midpoint subdivision. Our method produces pure hexahedral meshes in approximately 80% of the cases, and hex-dominant meshes with less than 2% non-hexahedral cells in the remaining cases. We demonstrate the robustness of our method on 70+ models, including CAD objects with features of various complexity, organic and synthetic shapes, and provide extensive comparisons to prior art, demonstrating its superiority.
The aim of this investigation is to study the effect of selection of mesh distribution on efficacy of natural frequency of Timoshenko beam. The harmonic differential quadrature (HDQ) method is used ...to compute the natural frequency of Timoshenko beam. In this regards, three different types of meshing are used namely uniform meshing, normalized meshing and non-uniform. The results obtained using these meshing are compared with results obtained in previous published work under different types of boundary conditions. It is found that non-uniform meshing gives better convergence as well as good results as compare to results using uniform and normalized meshing under all boundary conditions.
Abstract
Aiming at the limitations of the existing hydraulic pumps, a new type of bidirectional water-hydraulic internal ball gear pump using concave-convex ball teeth meshing to transfer power is ...proposed. In this paper, the principle of internal gear pump is utilized to establish the model of internal ball gear pump, and its mechanical properties and dynamic meshing characteristics are numerically investigated by using the finite element method. The results show that (a) the concave-convex ball gears run smoothly without any interference, and (b) increasing the number of gear rows can effectively reduce the maximum stress and meshing impact under a given load and speed. This study provides a basis for the development of high-performance ball gear pumps.
Hexahedral meshes are a ubiquitous domain for the numerical resolution of partial differential equations. Computing a pure hexahedral mesh from an adaptively refined grid is a prominent approach to ...automatic hexmeshing, and requires the ability to restore the all hex property around the hanging nodes that arise at the interface between cells having different size. The most advanced tools to accomplish this task are based on mesh dualization. These approaches use topological schemes to regularize the valence of inner vertices and edges, such that dualizing the grid yields a pure hexahedral mesh. In this article, we study in detail the dual approach, and propose four main contributions to it: (i) We enumerate all the possible transitions that dual methods must be able to handle, showing that prior schemes do not natively cover all of them; (ii) We show that schemes are internally asymmetric, therefore not only their construction is ambiguous, but different implementative choices lead to hexahedral meshes with different singular structure; (iii) We explore the combinatorial space of dual schemes, selecting the minimum set that covers all the possible configurations and also yields the simplest singular structure in the output hexmesh; (iv) We enlarge the class of adaptive grids that can be transformed into pure hexahedral meshes, relaxing one of the tight topological requirements imposed by previous approaches. Our extensive experiments show that our transition schemes consistently outperform prior art in terms of ability to converge to a valid solution, amount and distribution of singular mesh edges, and element count. Last but not least, we publicly release our code and reveal a conspicuous amount of technical details that were overlooked in previous literature, lowering an entry barrier that was hard to overcome for practitioners in the field.
Identifying the bearing fault-induced impulsive components in the frequency domain is a key step in the corresponding fault detection. However, gearbox vibration signals often significant interrupt ...the rolling bearing fault diagnosis, particularly in the detection of planet bearing faults under the background noise of the planetary gearbox. Except in the case of a high amplitude, a gear meshing-related vibration may also affect the identification of the planet bearing fault-induced resonance frequency band. To solve this problem, a meshing frequency modulation index (indexMFM)-based kurtogram utilizing a particular gearbox related phenomenon is proposed. The underlying mechanism is such that although the gear meshing-related spectral components are always more prominent in relatively higher-frequency band than the planet bearing-induced resonance frequency band in impulsiveness, the gear meshing-related impulsive components modulate the gear meshing frequency, yet the faulty bearing-induced one does not. Exploiting this difference, the planet bearing fault-induced impulsive components can be directly identified from the strong gear vibration interruption by determining the bearing fault-related resonance frequency band in the indexMFM-based kurtogram. The effectiveness of the proposed method is separately verified using simulated and experimental data.
This work describes an advanced model for the analysis of contact forces and deformations in spur gear transmissions. The deformation at each gear contact point is formulated as a combination of a ...global and a local term. The former is obtained by means of a finite element model and the latter is described by an analytical approach which is derived from Hertzian contact theory. Then the compatibility and complementary conditions are imposed, leading to a nonlinear system of equations subjected to inequality restrictions that should be solved once the position of each gear centre is known. A numerical example is presented where the quasi-static behaviour of a single stage spur gear transmission is discussed, showing the capabilities of the methodology to obtain the Loaded Transmission Error under several load levels as well as some other related measures such as load ratio or meshing stiffness.
► A model for study contact forces and deformations in external spur gear transmissions. ► Local and global deformation considered separately, reducing computational effort. ► Transmitted torque, friction and working distance affects LTE, meshing stiffness and Load Ratio. ► Meshing stiffness in double contact period is calculated considering the coupled deflection of adjacent contacting pairs. ► Gear body deflection has a great influence on the values of the meshing stiffness.
Gearboxes are at the heart of most rotating machines and they are considered as one of the main sources of vibration. As a key element in rotating machines, it is important to extract the gearbox ...vibration part from the mechanical system signal to assess the health state of the gearbox. In general, the gear meshing frequency part contains rich information which reflects its health state. In this paper, the authors find that in some cases when gearboxes work under heavy load, the meshing frequency part cannot be detected easily from the frequency spectrum. We think that the meshing frequency part may be modulated to the higher frequency band as the meshing impacts. To prove this point, a Multi-Input Single-Output (MISO) model is proposed to identify the local resonance excited by gear meshing impacts. In our method, a Meshing Impact Energy Distribution (MIED) graph is obtained through iteration to determine the demodulated frequency band. Experimental vibration data acquired form a healthy gearbox are illustrated to validate the performance of the proposed method. The forklift is taken as an example in the paper. Forklifts usually work in heavy load condition, and the gearbox vibration of a forklift is generally mixed with the ignition impacts of the diesel engine. The experiment result shows that for forklift machine system working in heavy load condition, its meshing frequency part of gearbox vibration signal is modulated into high frequency band. Further, the result shows that the proposed method is good at extracting the meshing frequency component when it is modulated into high frequency band especially when it is in heavy load condition.
Gear transmission system is widely used in many mechanical equipment to achieve power transmission and rotational speed changes. Meshing power loss is one key index to assess the performance of a ...gear system, which directly influences heat generation and lubrication, etc. Over the past decades, many computational models of gear meshing power loss have been proposed to support gear design and optimization. However, the coupling effect between the gear friction and dynamic characteristics are usually ignored, including time-varying meshing stiffness (TVMS) and dynamic meshing force (DMF), which are not conducive to accurate calculation and improvement of meshing power loss. Therefore, an improved gear meshing power loss calculation method is proposed to settle this problem in this paper. With the proposed method, the friction calculation model is established considering the effect of DMF and surface roughness based on mixed elastohydrodynamic lubrication (EHL). Then the TVMS is obtained with the friction force along the meshing line and DMF was taken into consideration. On the basis of modelling of friction and TVMS, a six degrees-of-freedom (DOF) gear dynamic model, as well as a power loss iteration calculation process are established and studied. The effects of gear surface manufacturing quality and loads on power loss are analyzed. Furthermore, a gear meshing power loss experimental setup is constructed to verify the effectiveness of the proposed method. The results show that this method is in better agreement with the experimental results than the traditional method which does not consider the coupling effects.
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