Contact Curves Research Articles

A new discrete element method for small adhesive non-spherical particles

Small adhesive particles with non-spherical shapes are common in natural and industrial processes. However, it is challenging to accurately simulate the dynamic behaviors of non-spherical particulate systems, not only due to the complex local geometry at the contact region but also to the non-linear coupling between the van der Waals adhesion and the elastic deformation. In this paper, we develop a discrete element method (DEM) framework for small non-spherical particles. Particularly, we present a simple algorithm for solving the implicit equations of the dimensionless generalized JKR model, to accurately resolve the local surface geometry at the contact region and the strong coupling between the elastic deformation and the surface adhesion. New explicit expressions are established for the pull-off force, overlap and minor-to-major ratio of the contact ellipse, to naturally capture the pull-off point upon collision. Then the actual contact parameters including the contact radius, curvatures and overlap are used to modify the interparticle interactions, including the normal elastic-adhesive-dissipative force and sliding-rolling-twisting resistances. Finally, the framework is quantitatively validated by four random packing problems, including adhesive spheres, ellipsoids, spherocylinders and dimers, and the representative non-adhesive ellipsoids. Both the microscopic and macroscopic properties of packings agree well with a large number of classic theories, experiments and simulations, showing the satisfactory accuracy and effectiveness. The newly developed adhesive DEM framework has the full capability to dynamically simulate the collision-related behaviors of complex shaped particles in the presence of van der Waals adhesion and frictional forces.

Performance analysis of LaFeO3 perovskite solar cells: A theoretical and experimental study

Lanthanum ferrite (LaFeO3) is a potential candidate for Perovskite Solar Cell (PSC) application. The transition metal oxide has strong electron-electron correlation which results in an increase in quantum efficiency (QE) of PSC. In this investigation, we reported synthesis of LaFeO3 perovskite material, simulation of LaFeO3-based PSC followed by experimental validation. The sol-gel method was employed to prepare nanoparticles of LaFeO3 for PSC application. The prepared perovskite material is analyzed by XRD, SEM, EDS, UV–Vis and FTIR. The photovoltaic (PV) application of synthesized LaFeO3 material is studied by SCAPS-1D. The LaFeO3-based PSC is simulated with various ETLs such as TiO2, PCBM, IGZO, In2O3, C60, ZnO, SnO2, WS2 and HTLs of Cu2O, CuInSe2, Spiro-OMeTAD, P3HT, D-PBTTT-14, V2O5, CFTS, CBTS. The simulation outcomes of 64 distinct configurations deduced the eight-best performing PSCs. For these eight PSCs, impact of thickness of perovskite absorber layer, operating temperature, defect density, series and shunt resistance, work function of back contact, J-V characteristics and QE curve has been studied. We have achieved theoretical maximum efficiency of 13.03 % for the configuration of FTO/WS2/LaFeO3/CBTS/Au. The optimized structure has experimentally obtained maximum efficiency of 0.79 %. This shows that it is promising material for future PV application.

Methodology for Circuit Breaker Contact Diagnosis through Dynamic Resistance Measurements and Fuzzy-Logic-Based Analysis

This paper presents a methodology capable of measuring, processing, and extracting contact resistance parameters that enable the identification of the contact degradation level inside arc extinction chambers in medium- and high-voltage circuit breakers (CB). To determine the contact degradation level, an algorithm was developed to extract the characteristic parameters from the results of dynamic resistance measurement (DRM). To analyze the dataset parameters, this work employs the combination of different statistical tools, such as boxplots and fuzzy logic, enabling the evaluation to be conducted without the subjectivity inherent in human decision. Therefore, a more objective and reliable diagnosis could be achieved. The DRM tests were performed on two types of minimum-oil CB (MOCB), 800 A/15 kV/12.5 kA (CB-A) and 2000 A/72.5 kV/31.5 kA (CB-B and CB-C). For CB-A and CB-B, three contacts were utilized for each CB, with significant contact degradation. For CB-C, a single contact was employed without significant degradation. The DRM curves of the CB-C contact were used as the reference for evaluation of the CB-B contacts. For this purpose, a new DRM system was developed. The proposed methodology can be defined as a complement for other diagnostic techniques, serving as a non-subjective asset management tool, supporting decisions regarding equipment interventions.

Detection of Contact Binary Candidates Observed By TESS Using the Autoencoder Neural Network

A contact binary may be the progenitor of a red nova that eventually produces a merger event and have a cut-off period of around 0.2 days. Therefore, a large number of contact binaries is needed to search for the progenitor of red novae and to study the characteristics of short-period contact binaries. In this paper, we employ the Phoebe program to generate a large number of light curves based on the fundamental parameters of contact binaries. Using these light curves as samples, an autoencoder model is trained, which can reconstruct the light curves of contact binaries very well. When the error between the output light curve from the model and the input light curve is large, it may be due to other types of variable stars. The goodness of fit (R 2) between the output light curve from the model and the input light curve is calculated. Based on the thresholds for global goodness of fit (R 2), period, range magnitude, and local goodness of fit (R 2), a total of 1322 target candidates were obtained.

Relation of the stress state in the contact zone and the forces acting in the roller mechanisms

Mathematical models were developed to study the distribution pattern of shear and friction stresses in the roll contact zone. These models establish a relationship between the stress state in the contact zone, the forces acting on the roller mechanisms, and the shape of the roll contact curve in driven and free rollers. The distribution of normal stresses determines the distribution of shear stresses along the contact curve, the compliance of the material strip and the roller coating, and the forces acting on the roller mechanism.

Periodic Variation Studies of the Two Short Period W UMa-type Eclipsing Binaries: LX Lyn and V0853 Aur

In this paper, new light curves (LCs) of contact eclipsing binary (CEB) systems LX Lyn and V0853 Aur are presented and analyzed by using the 2015 version of the Wilson–Devinney (W-D) code. In order to explain their asymmetric LCs, cool starspots on the components were employed. It is suggested that their fill-out degrees are f = 12.0% (LX Lyn) and f = 26.3% (V0853 Aur). At the same time, we found that LX Lyn is a W-type eclipsing binary (EB) with an orbital inclination of i = 84.°88 and a mass ratio of q = 2.31. V0853 Aur is also a W-type CEB with a mass ratio of q = 2.77 and an orbital inclination of i = 79.°26. Based on all available times of light minimum, their orbital period changes are studied by using the O − C method. The O − C diagram of LX Lyn reveals a cyclic oscillation with a period of about 14.84 yr and an amplitude of 0.0019 days, which can be explained by the light-travel time effect (LTTE) due to the presence of a third body with a minimum mass of 0.06M ⊙. For V0853 Aur, it is discovered that the O − C diagram of the system also shows a cyclic oscillation with a period of 9.64 yr and an amplitude of 0.03365 days. The cyclic oscillation of V0853 Aur can be attributed to the LTTE by means of a third body with a mass no less than 3.77M ⊙. The third body may play an important role in the formation and evolution of these systems.

Calculation formulas for contact curves of technological machine

The problem of describing the contact curves of technological machines has been solved. At the same time, contact interaction was studied taking into account changes in the technological parameter and deformation of the materials of the contacting bodies. The obtained dependencies make it possible to find rational parameters of the technological process with sufficient accuracy. The obtained models indicate that the shape of the contact is influenced by such parameters as strip thickness, roll radii, external forces, as well as parameters characterizing the deformations of the contacting bodies.

Parameters of technological machine roll contact curves

The main parameters of the contact curve of each roll are its shape and length, and the extent of the slip and no-slip zones. Analytical dependencies were obtained that determine the parameters of the contact curves of the rolls of technological machines. It was revealed that at the beginning of the contact zone the skin points are distant from the roll covering point, in the zone at the end of the contact zone it is ahead of it. At the end of the contact zone, the angle between the corresponding points of the skin layer and the roller coating is equal to the modulus of the difference between the lag and advance angles.

Study on modeling of contact interaction in roll modules

The main problem of the mechanics of contact interaction in roll modules is to determine the stress-strain state in the technological zone. The article presents mathematical models of the laws of distribution of contact stresses and analytical dependencies of their main indices, which make it possible to calculate the power parameters of roll modules of technological machines. When developing mathematical models, empirical formulas for the laws of distribution of normal stresses along roll contact curves and a friction stress model were used, considering the effect of external forces, roll drive, and compliance of the roll coating on the distribution of shear stresses. It is shown that normal stresses in the compression zone increase from zero to the maximum value by the harmonic law, and in the recovery zone, they decrease from the maximum value to zero by the parabolic law. It was revealed that in the driven roll, the neutral point is located on the left side of the point of maximum normal stress, and the points that determine the maximum normal stress and compression of the interacting bodies coincide and are shifted from the line of centers towards the supply of the processed material into the contact zone.

On some special ruled surfaces

In this paper, regarding α and β, we examine some special ruled surfaces in (α,β)-type normal almost contact metric (briefly a.c.m.) manifolds whose base curves are almost contact curves which are not geodesic. By selecting the base curve and the ruling of these ruled surfaces, we obtain important theorems and corollaries.

Influence of contact curvature on frictional energy dissipation under varying tangential loads

This study investigates the effect of contact surface curvatures on the friction response under varying tangential loadings using a finite element (FE) model. The results showed that the geometry of the surface influences the contact force at the interface and reduces the friction effect through an unsteady distribution of the contact force. The relationship between the friction effect, excitation, and contact surface shape was also examined, revealing a linear inverse relationship between the friction and curvature. The findings provide a comprehensive understanding of the frictional interactions between elastic bodies and highlight the role of curvature as a design parameter for regulating the friction effect.

Enumeration of Rational Contact Curves via Torus Actions

We prove that some Gromov–Witten numbers associated to rational contact (Legendrian) curves in any contact complex projective space with arbitrary incidence conditions are enumerative. Also, we use the Bott formula on the Kontsevich space to find the exact value of those numbers. As an example, the numbers of rational contact curves of low degree in P3 and P5 are computed. The results are consistent with existing results.

Geometry of cascade feedback linearizable control systems

Cascade feedback linearization provides geometric insights on explicit integrability of nonlinear control systems with symmetry. A central piece of the theory requires that the partial contact curve reduction of the contact sub-connection be static feedback linearizable. This work establishes new necessary conditions on the equations of Lie type - in the abelian case - that arise in a contact sub-connection with the desired static feedback linearizability property via families of codimension one partial contact curves. Furthermore, an explicit class of contact sub-connections admitting static feedback linearizable contact curve reductions is presented, hinting at a possible classification of all such contact sub-connections. Key tools in proving, and stating, the main results of this paper are truncated versions of the total derivative and Euler operators. Additionally, the Battilotti-Califano system with three inputs is used as a clarifying example of both cascade feedback linearization and the new necessary conditions.

Robust Multilegged Walking Robots for Interactions With Different Terrains

Abstract This paper explores the kinematic synthesis, design, and pilot experimental testing of a six-legged walking robotic platform able to traverse through different terrains. We aim to develop a structured approach to designing the limb morphology using a relaxed kinematic task with incorporated conditions on foot-environments interaction, specifically contact force direction and curvature constraints, related to maintaining contact. The design approach builds up incrementally starting with studying the basic human leg walking trajectory and then defining a “relaxed” kinematic task. The “relaxed” kinematic task consists only of two contact locations (toe-off and heel-strike) with higher-order motion task specifications compatible with foot-terrain(s) contact and curvature constraints in the vicinity of the two contacts. As the next step, an eight-bar leg image is created based on the “relaxed” kinematic task and incorporated within a six-legged walking robot. Pilot experimental tests explore if the proposed approach results in an adaptable behavior which allows the platform to incorporate different walking foot trajectories and gait styles coupled to each environment. The results suggest that the proposed “relaxed” higher-order motion task combined with the leg morphological properties and feet material allowed the platform to walk stably on the different terrains. Here we would like to note that one of the main advantages of the proposed method in comparison with other existing walking platforms is that the proposed robotic platform has carefully designed limb morphology with incorporated conditions on foot-environment interaction. Additionally, while most of the existing multilegged platforms incorporate one actuator per leg, or per joint, our goal is to explore the possibility of using a single actuator to drive all six legs of the platform. This is a critical step which opens the door for the development of future transformative technology that is largely independent of human control and able to learn about the environment through their own sensory systems.

Irreducible contact curves via graph stratification

We prove that the moduli space of contact stable maps to P2n+1 of degree d admits a stratification parameterized by graphs. We use it to determine the number of irreducible rational contact curves in P2n+1 with any Schubert condition. We give explicitely some of these invariants for P3 and P5. We give another proof of the formula for the number of plane contact curves in P3 meeting the appropriate number of lines.

Simulation and neural network analysis of spreading the oblique fuel jet impinging onto concave walls

A series of numerical simulations of oblique-jet impinging onto concave walls are carried out to gain insight into the formation process of the liquid fuel film in a liquid film cooling thrust chamber. Moreover, the influence of jet and wall surface parameters on spreading the fuel film is investigated. The volume-of-fluid method is employed to capture the spreading process of liquid film formation after an oblique jet impacts the curved surface. Furthermore, the neural network model is developed to analyze the effects of jet diameter (0.2 mm ≤ d ≤ 0.6 mm), jet velocity (15 m/s ≤ v ≤ 20 m/s), impingement angle (15°≤β ≤ 30°), equilibrium contact angle (45°≤θe≤75°), curvature radius (22.5 mm ≤ R ≤ 67.5 mm), and surface roughness (3.2 μm ≤ Ra ≤ 16μm) on the fuel film's spreading length and maximum width based on Radial Basis Function. The results show that the liquid fuel film gradually stabilizes from upstream to downstream during spreading and the circumferential spreading of the liquid film is at its greatest when all the forces in the circumferential direction are in equilibrium. The jet diameter has the most significant effect on film spreading among jet parameters. Doubling the jet diameter at least doubles the film width and length. The effect of jet angle and velocity on film spreading is also magnified at larger jet diameters. Compared to other surface parameters, a change in the wall contact angle has the most marked effect on the spreading of the film. Lastly, the wall radius of curvature between 40 mm and 50 mm is more favorable for obtaining larger film lengths.

Sextactic points on the Fermat cubic curve and arrangements of conics

The purpose of this note is to report, in narrative rather than rigorous style, about the nice geometry of 6-division points on the Fermat cubic F and various conics naturally attached to them. Most facts presented here were derived by symbolic algebra programs and the idea of the note is to propose a research direction in the search of conceptual proofs of facts stated here and their generalisations. Extensions in several directions seem possible (taking curves of higher degree and contact to F, studying higher degree curves passing through higher order division points on F, studying curves passing through intersection points of already constructed curves, taking the duals etc.) and we hope some younger colleagues might find pleasure in following proposed paths as well as finding their own.

Theoretical model and simulation of a twin-Screw multiphase pump with novel smooth screw rotors for gas-Oil mixed transportation

A pair of screw rotors, the core components of twin-screw multiphase pumps, primarily determine the pump performance. The conventional screw rotor contains unsmooth edges caused by unsmooth points in the cross-sectional profiles, which will lead to the abrasion, wear and fatigue near the unsmooth edges of the screw rotors during operation. For solving this problem, a novel pair of fully smooth screw rotors without unsmooth edges were proposed, and their cross-sectional profiles composed of the elliptical arcs and their conjugate curves were put forward. Parametric equations of the proposed screw rotor profiles were also derived, and then the effects of geometric parameters on the pump performance of the proposed screw rotors were discussed. Furthermore, the transient flow of the twin-screw multiphase pump with the proposed screw rotors were carried out by numerical simulations. The distributions of pressure and velocity in the proposed pump were obtained. The gap leakage and backflow velocity at each gap varying with time and location in the working process were also analyzed. The results indicate that the carryover of the proposed screw rotors is reduced by 90.49%, while its area utilization ratio is increased by 0.8%, and the length of the spatial contact curve is reduced by 25.71% in comparison with the conventional screw rotors. Thus, the superiority and feasibility of the proposed screw rotors are validated.

Semi-analytical loaded tooth contact analysis method for spiral bevel gears

Loaded tooth contact analysis (LTCA) is an important tool for analyzing the meshing of spiral bevel gears. This paper presents a semi-analytical LTCA method, where the analytical formulas are used to calculate the tooth deformation and contact force, with partial coefficients corrected by finite element analysis (FEA) results. Based on Tredgold's Approximation, the tooth is sliced, of which the flank is determined by simulating the manufacturing process. In order to calculated the potential contact curves of a real gear pair, an optimization model is established to find the points more likely to be in contact within the range of contact curves obtained by the help of roll angle surfaces. The compliance of tooth is modeled as a combination of two contributions, where the deformation of cantilever beam under load is used to determine the global deformation, and the local contact deformation is obtained by Hertz line contact assumption. A contact judgement strategy is proposed to detect the contact of the slices at ends of contact curves, and the correction coefficients are introduced in the tooth deformation to consider the coupling effect among slices. In the end, a numerical instance of LTCA under different load torques is provided, which demonstrates the accuracy and efficiency of the presented LTCA method by comparisons with results of FEA. This method can be easily modified to analyze other gear pairs and has the ability to be extended to simulate the gears with local defects or cracks.

Automatic Generation of Interference-Free and Posture-Smooth Toolpath for Robotic Belt Grinding of Complex Workpieces

Robotic belt grinding has shown great potential to achieve automatic machining of high-precision parts. However, its productivity in machining complex parts has been greatly limited by the problem that interference-free and posture-smooth toolpath planning is still a time-consuming and labor-intensive job. Therefore, this work presents a fully automatic and practical approach to facilitate interference-free and posture-smooth toolpath planning for robotic belt grinding of complex parts. With this approach, the interference correction spaces in two common belt grinding modes, namely, wheel face grinding and wheel edge grinding, are first established, where various types of interferences and their corresponding correction strategies are modeled. Then, two B-spline posture curves, which represent the rotational motion and translational motion of the workpiece for correcting interference throughout the entire cutter contact curve, are presented. With the two B-spline curves, a toolpath planning algorithm for robotic belt grinding of complex parts is further developed based on surface partitioning and iteratively correcting interference and smoothing grinding postures. The effectiveness and practicability of the proposed approach are validated by simulations and experimental studies, which demonstrates that the authors’ approach can significantly improve the toolpath planning efficiency and ground surface quality for complex parts as compared with the leading commercial computer-aided manufacturing (CAM) software.