We present the Feature Tracking Kit (FTK), a framework that simplifies, scales, and delivers various feature-tracking algorithms for scientific data. The key of FTK is our simplicial spacetime ...meshing scheme that generalizes both regular and unstructured spatial meshes to spacetime while tessellating spacetime mesh elements into simplices. The benefits of using simplicial spacetime meshes include (1) reducing ambiguity cases for feature extraction and tracking, (2) simplifying the handling of degeneracies using symbolic perturbations, and (3) enabling scalable and parallel processing. The use of simplicial spacetime meshing simplifies and improves the implementation of several feature-tracking algorithms for critical points, quantum vortices, and isosurfaces. As a software framework, FTK provides end users with VTK/ParaView filters, Python bindings, a command line interface, and programming interfaces for feature-tracking applications. We demonstrate use cases as well as scalability studies through both synthetic data and scientific applications including tokamak, fluid dynamics, and superconductivity simulations. We also conduct end-to-end performance studies on the Summit supercomputer. FTK is open sourced under the MIT license: https://github.com/hguo/ftk .
Abstract A lot of work is needed to investigate the design method of planar internal gear enveloping drum worm (PIGEDW). Firstly, based on the gear meshing theory, the meshing equation is deduced. ...Secondly, the PIGEDW mathematical model is established by MATLAB. Finally, the influence of the inclination angle of the generating plane on the meshing performance of PIGEDW is analyzed. The results show that appropriate changes in geometric parameters are beneficial in enhancing the performance of PIGEDW, which provides a way to optimize its design.
With the construction of periodic functions relative to the meshing frequency, rotating frequency, and the faulty frequency, etc., the phenomenological model provides a simple and effective way of ...representing the vibration signal of the planetary gearbox. However, due to that the meshing vibration is simplified, the traditional model can only reflect the modulation characteristic of the signal, but not the impact characteristic. Therefore, an improved phenomenological model is proposed, which can satisfy these two characteristics of the vibration signal at the same time. To consider the meshing vibration correctly, two key points should be determined: occurring moment of impact signals, and their relative amplitudes. In order to calculate the occurring time, this paper proposes modifying the reference point of the meshing phase and using the modified phases to represent it. Then two experiments are designed to verify the correctness of the modified phases and the occurring moment. Fortunately, these experimental results also provide a factual basis for determining the relative amplitudes of these impact signals. Subsequently, signal model of the gearbox in the healthy state is established based on the meshing vibration characteristics. The simulation results show that the new model can satisfy the modulation and impact characteristics. In addition, combined with the time-varying meshing stiffness of the gear pair, the paper theoretically analyzes the influence of fault type, location, and size on the impact frequency in a fault meshing period. Finally, the correctness of the new phenomenological model is verified by experiments.
Signed distance fields (SDFs), as a powerful surface representation, draw more and more attention in recent years, especially with the innovation of geometric deep learning techniques. In fact, many ...kinds of popular surface representations, whether explicit forms (point cloud, mesh, or S(u,v)=x(u,v),y(u,v),z(u,v)) or implicit forms (f(x,y,z)=0), can be easily transformed into the SDF representation. It is an interesting research direction to accomplish some important operations directly on the SDF representation. Considering that restricted Voronoi diagrams (RVDs), as a fundamental geometric tool, are central to sampling, meshing and many other geometry processing tasks, we focus on how to define and compute RVDs based SDF, named SDF-RVD. Given a set of samples {xi}i=1m lying on the surface, the key idea is to define RVD based on analyzing how the 3D Voronoi diagram w.r.t. {xi}i=1m passes through the implicit surface, without rigorously decomposing the watertight surface into a set of curved surface patches. We further observe that SDF-RVD works well on an arbitrary surface representation as long as it is equipped with the projection operation. Even for the mesh input, the timing cost spent in computing SDF-RVD is nearly independent of the original mesh resolution, which distinguishes itself from the traditional RVD based meshing approaches. We further show that SDF-RVD is able to naturally work with centroidal Voronoi tessellation (CVT) and report a well triangulated mesh as the output. Finally, we link SDF-RVD plus CVT up with those continuous SDF based neural networks (e.g., DeepSDF) for directly transforming a point cloud into a high-quality triangle mesh, which does not include a step of extracting a poor-quality mesh using marching cubes.
•We propose SDF-RVD to extend RVD from a polygonal mesh to SDF representation.•SDF-RVD works well as long as the projection operation is equipped.•We give a strategy to assign each site a single RVD patch.•Our algorithm operates on SDF, yielding a good triangle mesh without marching cubes.
Hexahedral (hex) meshes can be generated for CAD models of complex thin-walled components by isolating thin-sheet and long-slender regions, quad meshing one of the bounding faces, and sweeping the ...quad mesh through the volume to create hex elements. Continuing the work in Sun et al. (Proc Eng 163:225–237,
2016
), where an improved approach to thin-sheet identification was presented, an enhanced automatic method for long-slender region identification is proposed in this paper. The objective is to improve the efficiency and decomposition quality compared to existing long-slender region identification processes. Geometric measures such as the edge length and the face width are employed to generate sizing measures, which are in turn used to identify candidate long-slender regions. Careful consideration is given to the generation and positioning of the cutting faces required to isolate the long-slender regions by assessing a
priori
quad mesh quality on the wall faces. It is shown that a significant reduction in the number of degrees of freedom (DOF) can be achieved by applying anisotropic hex elements on the identified regions.
•A SADS’s dynamics model was proposed and verified by a test in the laboratory.•Disturbances occur when the rotation or structural vibration acceleration is not zero.•Three factors such as the ...current subdivision directly cause disturbances.•Disturbances vary periodically and occur near harmonic excitation frequencies.•Four factors such as the closed-loop control do not cause but affact disturbances.
An electromechanical dynamic model of the solar array drive system (SADS) was proposed to analyze the disturbance characteristics, and verified by the experiment study in the laboratory. The factors which directly cause the SADS’s disturbance were differentiated based on the idea of reductionism, and corresponding disturbance characteristics were investigated. The other kinds of factors which do not cause disturbances but affect the disturbance characteristics of SADS, as well as their influence rules, were also analyzed. The results of the proposed model agree well with the experimental data, with an error of less than 10%. Disturbances of SADS occur when the rotational-motion acceleration and structural-vibration acceleration are not both equal to zero. The current subdivision of the drive controller, nonlinear magnetic field of the stepping motor, and the varying meshing parameters of the gear reducer can directly cause disturbances, which vary periodically and occur near excitation frequencies and high-order harmonic frequencies. The amplitude of the disturbance increases with a decrease in the number of current subdivisions, an increase in electromagnetic excitation and the fluctuation margin of gear-meshing parameters. The closed-loop current control, nonlinear friction between the brush and slip ring, the bending-torsional coupling of the solar array, and the gear clearance of the gear reducer do not cause the SADS’s disturbances but can affect their profile and spectrum distribution from different aspects, even introducing disturbance components in the non-driving directions.
•Models for load sharing ratio (LSR) and quasi-static transmission error (QSTE) of spur gears are presented.•Contact along additional intervals due to teeth deflections are studied.•Equations for the ...LSR and QSTE considering extra contact intervals are provided.•Influence of profile modification in LSR and QSTE is considered.•Required profile modifications for predesigned functions of LSR or QSTE are developed.
The meshing stiffness, load sharing ratio, and quasi-static transmission error of spur gear pairs are related to each other and are dependent on tooth geometry. In addition, profile modifications influence the contact conditions, because modified profile points may only contact under load conditions and owing to load-induced elastic deflections. However, this is not the case under no-load conditions, wherein a gap would exist between the teeth owing to the contact of other tooth pairs at unmodified points. In this paper, the contact conditions of modified teeth under load have been studied, and the influence of the amount, length, and shape of the profile modification on the load sharing and transmission error has been described. A simple, analytic formulation of all these relations is provided, based on a previously developed approximate equation for the meshing stiffness, which provides accurate results. The simplicity of the obtained equations facilitates the study of the influence of the profile modification on the load sharing and transmission error, and the required profile modification for predesigned functions of load sharing ratio or quasi-static transmission error was also obtained.
Premature wear, fatigue and other failures caused by non-linear vibration are one of the key problems of aerodynamic power transmission in spline coupling which maybe suffer from abnormal meshing ...effects due to misalignment between internal spline and external spline. A non-linear dynamic model of the misaligned spline coupling is established, which involves the calculation of dynamic meshing behavior of misaligned tooth pairs. The movement state of spline coupling can change from a periodic state to a chaotic state with the increase of speed. Under light load, the main resonance speed of system may be modified due to changes in the load. The existence of misalignment promotes the vibration intensity, advances the main resonance speed and increases the instability of spline coupling. In addition, a test bench for the misalignment spline coupling was developed to measure the vibration acceleration signal, and the effect of the misalignment on the dynamic behavior of spline coupling was discussed.
Hex-dominant meshing: Mind the gap Ray, Nicolas; Sokolov, Dmitry; Reberol, Maxence ...
Computer aided design,
September 2018, 2018-09-00, 20180901, Letnik:
102
Journal Article
Recenzirano
Odprti dostop
We propose a robust pipeline that can generate hex-dominant meshes from any global parameterization of a tetrahedral mesh. We focus on robustness in order to be able to benchmark different ...parameterizations on a large database. Our main contribution is a new method that integrates the hexahedra (extracted from the parameterization) into the original object. The main difficulty is to produce the boundary of the result, composed of both faces of hexahedra and tetrahedra. Obviously, this surface must be a good approximation of the original object but, more importantly, it must be possible to remesh the volume bounded by this surface minus the extracted hexahedra (called void). We enforce these properties by carefully tracking and eliminating all possibilities of failure at each step of our pipeline.
We tested our method on a large collection of objects (200+) with different settings. In most cases, we obtained results of very good quality as compared to the state-of-the-art solutions. To ease reproducing our results and benchmarks, we provide a C++ implementation of the pipeline in the supplemental materials.
Display omitted
•We present a robust method of generating hex-dominant meshes free of degenerate or flipped elements.•It allows to plug in specialized algorithms for meshing particular geometries, such as fillets or tubular structures.•We publish an open source implementation.
In this paper, a novel cutter section is designed, which adds a linear transition section between the fillet and the major cutting edge for the three-faced cutter plate. By deriving the relative ...motion coupling relationship with the cutter plate, machine and gear blank, the tooth surface point set is solved by using the meshing equation and the mapping relationship with the discretized point set of the blank section. The mathematical model and the meshing model of hypoid gear are established with different cutter parameters. The influences of the multi-segment cutter section on the meshing characteristics of the hypoid gear are researched. The results show that the effect of contact pattern is not obvious of with linear segment. Besides, the peak to peak value of transmission error and meshing stiffness are reduced compared with the traditional cutter section. With the increase of the length of the linear segment, the tooth root bending stress increases and the transmission error and meshing stiffness decrease. The tooth root bending stress decreases and the transmission error and the meshing stiffness are not obvious with the increased of the radius of fillet. Therefore, the proper length of the linear segment and the radius of fillet can reduce the vibration by decreasing the transmission error with guaranteed strength.
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