Cylindrical Pair Research Articles

Optimization of and experimentation with a bifurcated swing tube strip fertilizer spreading device based on MBD-DEM coupling.

To improve the utilization rate of fertilizers, realize the precise spreading of fertilizers in controllable strips, and ensure the uniformity of fertilizer spreading in both longitudinal and transversal directions, a bifurcated swing tube fertilizer spreading device driven by a spatial hammer pendulum crank mechanism was designed. First, the drive mechanism was designed based on the cylindrical pair of the mechanism. A mathematical model pendulum equation was used to design the swing tube, and the equation of motion of fertilizer particles was established by analyzing the motion and force of fertilizer particles in fertilizer spreading. The dynamic parameters of the fertilizer spreading device (nozzle height, forward velocity, and swing frequency) were identified as the test factors affecting the uniformity of fertilizer spreading. Second, the coupling model based on MBD-DEM was established, and the coupling simulation analysis of the fertilizer spreading process was carried out using EDEM-RecurDyn software. Taking the nozzle height, forward velocity, and swing frequency as test factors and the uniformity coefficient of longitudinal and transversal fertilizer spreading as evaluation indexes of the fertilizer discharging effect, we analyzed the influence of a single factor on the indexes. Moreover, the ternary quadratic generalized rotating combination response surface test established the regression equations of three factors and two evaluation indexes. Finally, the simulation and bench test were verified under the optimal combination of parameters and compared with the single swing tube bench test with the same parameter conditions. The results of the single-factor test showed that the fertilizer discharge effect was better when the nozzle height was 350.0-450.0 mm, the forward velocity was 0.5-1.5 m/s, and the swing frequency was 1.40-2.00 Hz. The results of the response surface test proved that the nozzle height, forward velocity, and swing frequency all had a highly significant effect on the uniformity coefficient of fertilizer spreading in the longitudinal and transversal directions (P<0.01). Moreover, the optimization concluded that when the nozzle height is 450.0 mm, the forward velocity is 0.5-0.8 m/s, and when the swing frequency is within the range of 1.40-2.00 Hz, the uniformity coefficient of longitudinal fertilizer spreading is ≤25% and the uniformity coefficient of transversal fertilizer spreading is ≤45%. The results of bench validation showed that the errors of longitudinal and transversal fertilizer spreading uniformity coefficients in the bench test were 3.46% and 1.44%, respectively, and the simulation agreed with the bench test. The results of comparative tests showed that the uniformity coefficient of the longitudinal and transversal of the fertilizer spreading device was reduced by 50.33% and 14.95%, respectively, for the bifurcated swing tube compared with that of the single swing tube. It is proved that the bifurcated swing tube strip fertilizer spreading device can achieve the purpose of uniform fertilizer spreading and performs better than the single swing tube in fertilizer spreading. The results and methods of this study can provide a reference for the design of swing tube strip fertilizer spreading devices and related fertilizer spreading performance tests.

Deployable structure based on double-layer Miura-ori pattern

With the requirements for improvement of earth observation range and accuracy, large-scale two-dimensional deployable antennas are urgently needed. In this paper, a deployable structure for a planar antenna with one degree of freedom and a flat reflection surface that can realize two-dimensional deployment with a compatible back frame is proposed based on a double-layer Miura-ori pattern. First, an antenna folding scheme with rectangular facets is proposed with the Miura-ori pattern. Through the method for hinge removal and replacement, a deployable antenna mechanism with a flat reflection surface is accomplished. Then, a kinematic model of the deployable structure is established to analyze its kinematic characteristics and prove the equivalence of motion before and after changing the hinges. By converting the rotating pairs between the two layers of origami into cylindrical pairs, a thick-panel form of double-layer origami is constructed. On this basis, a compatible back frame for the planar antenna mechanism is designed and a corresponding prototype is fabricated. The work paves the way to design deployable structures.

In Silico Interactome of a Room-Temperature Ferroelectric Nematic Material

The ferroelectric nematic (NF) phase, characterised by the combination of orientational and polar order, offers unique properties that are challenging to replicate in other systems. Understanding the molecular structure requirements for generating the NF phase is crucial for the design of new materials with enhanced properties. This study investigates UUQU-4-N, a room-temperature NF material, using fully atomistic molecular dynamics simulations. UUQU-4-N does not spontaneously form an apolar nematic phase in silico, but exhibits a stable polar nematic configuration akin to the NF phase. The polar order remains significant and near saturation throughout the simulations. The study also examines the cylindrical pair correlation functions, providing insights into the preferred pairing modes and intermolecular interactions which we can then attribute to specific molecular features. We then simulate structural variants of UUQU-4-N, highlighting the potential for developing further examples of near-room-temperature ferroelectric nematic materials via the manipulation of the fluorination pattern, variations in terminal chain length, and replacement of the difluoromethyleneoxy linker.

Solution for the Kinematics of Non-H-D Couplings Applied to RPCR Mechanism

The paper presents a proposed mechanism, RPCR, for the coupling of two shafts with crossed axes. For the analytical kinematics, the Hartenberg–Denavit methodology cannot be applied due to the planar pair occurrence. To apply the screw theory, the planar pair should be replaced by an assembly of cylindrical pairs, but this is also cumbersome. This work proposes an analytical solution obtained from the structural condition of planar joint based on the formulated expressions with respect to adequately chosen reference frames. A system of trigonometrical equations is obtained, but confusions may occur from classical solving; then, this paper presents the methodology with the correct approach. With the analytical solution for the displacements from the joints found, the conditions required for the constructive parameters of a realistic mechanism are found. The kinematical calculus of the mechanism is presented, and analytical relations are obtained for all relative motions from the pairs of the mechanism. The correctness of the analytical solutions is validated by the results of a numerical simulation.

The Influence of Time, Atmosphere and Surface Roughness on the Interface Strength and Microstructure of AA6061–AA1050 Diffusion Bonded Components

Diffusion bonding experiments followed by tensile testing were conducted on cylindrical pairs of AA6061-AA1050 aluminum alloys. The influence of bonding time, atmosphere and surface roughness on the resulting interface strength was studied. Metallurgical characterization was performed to study the quality of the bonded interface for different process conditions, and also to investigate the process of oxide formation on the specimen surface. Finite element analysis of the bonding experiments was used to study the thermo-mechanical fields during the bonding process. Using a cohesive zone approach for modelling the bonded interface, the bond strength for the different process parameters was quantified. The results demonstrate that high bond strength can be obtained even for specimens bonded in an air furnace, provided the surface roughness is low. When the surface roughness increases, specimens bonded in air show a reduction in interface strength, which is not observed for specimens bonded in vacuum. Inspection of the bonded interface suggests that this reduction in interface strength can be attributed to oxidation and pockets of air trapped between the asperities of the contact surface, which hinder diffusion and plastic flow.

Underconstrained Cable-Driven Parallel Suspension System of Virtual Flight Test Model in Wind Tunnel

An underconstrained cable-driven parallel robot (CDPR) suspension system was designed for a virtual flight testing (VFT) model. This mechanism includes two identical upper and lower kinematic chains, each of which comprises a cylindrical pair, rotating pair, and cable parallelogram. The model is pulled via two cables at the top and bottom and fixed by a yaw turntable, which can realize free coupling and decoupling with three rotational degrees of freedom of the model. First, the underconstrained CDPR suspension system of the VFT model was designed according to the mechanics theory, the degrees of freedom were verified, and the support platform was optimized to realize the coincidence between the model’s center of mass and the rotation center of the mechanism during the motion to ensure the stability of the support system. Finally, kinematic and dynamical modeling of the underconstrained CDPR suspension system was conducted; the system stiffness and stability criteria were deduced. Thus, the modeling of an underconstrained, reconfigurable, passively driven CDPR was understood comprehensively. Furthermore, dynamic simulations and experiments were used to verify that the proposed system meets the support requirements of the wind tunnel-based VFT model. This study serves as the foundation for subsequent wind tunnel test research on identifying the aerodynamic parameters of aircraft models, and also provides new avenues for the development of novel support methods for the wind tunnel test model.

The Kinematics of a Bipod R2RR Coupling between Two Non-Coplanar Shafts

The paper presents a new solution for motion transmission between two shafts with non-intersecting axes. The structural considerations fundament the existence in the structure of the mechanism of three revolute pairs and a bipod contact. Compared to classical solutions, where linkages with cylindrical pairs are used, our solution proposes a kinematical chain also containing higher pairs. Due to the presence of a higher pair, the transmission is much simpler, the number of elements decreases, and as a consequence, the kinematical study is straightforward. Regardless, the classical analysis of linkages cannot be applied because of the presence of the higher pair. For the proposed spatial coupling, the transmission ratio is expressed as a function of constructive parameters. The positional analysis of the mechanism cannot be performed using the Hartenberg–Denavit method due to the presence of a bipod contact, and instead, the geometrical conditions of existence for the bipod contact are applied. The Hartenberg–Denavit method requires the replacement of the bipodic coupling with a kinematic linkage with cylindrical (revolute and prismatic) pairs, resulting in complicated analytical calculus. To avoid this aspect, the geometrical conditions required by the bipod coupling were expressed in vector form, and thus, the calculus is significantly reduced. The kinematical solution for the proposed transmission can be obtained in two ways: first, by considering the equivalent transmission containing only cylindrical pairs and applying the classical analysis methods; second, by directly expressing the condition of definition for the higher pairs (bipodic pair) in vector form. The last method arrives at a simpler solution for which analytical relations for the positional parameters are obtained, with one exception where numerical calculus is needed (but the precision of this parameter is controlled). The analytical kinematics results show two possibilities of building the actual mechanism with the same constructive parameters. The rotation motions from the revolute pairs, internal and driven, and the motions from the bipod joint were obtained through numerical methods since the equations are very intricate and cannot be solved analytically. The excellent agreement validates the theoretical solutions obtained and the possibility of applying such mechanisms in technical applications. The constructive solution exemplified here is simple and robust.

Boundary load distribution of simultaneously meshed gear teeth pairs

The load distribution of simultaneously meshed gear teeth pairs has a significant influence in determining the relevant stress for the working capacity calculation of cylindrical gear pairs with respect to surface and volume strength. According to conventional calculation procedures, the influence of the boundary-ideally uniform load distribution, when all simultaneously meshed teeth pairs are equally engaged in the load transfer, on the teeth flanks stress state is taken into account by approximate expressions for contact ratio factor $$Z_{\varepsilon }$$ . In addition, this factor is not defined, no assumptions were given on the basis of which approximate expressions were determined, and no procedure for determining these expressions was disclosed. This paper defines a factor on the basis of which an analysis of the boundary-ideally uniform load distribution can be carried out. By observing the contact lines in the meshing area, when one and two or two and three meshed gear teeth pairs are alternating during the meshing period, a set of analytical expressions is developed to describe the boundary-ideally uniform load distribution of simultaneously meshed gear teeth pairs. Based on the developed analytical expressions, the limiting values of the gear teeth flank stresses can be determined more precisely and the degree of accuracy of the approximate expressions for the contact ratio factor which are given in conventional calculation procedures can be tested. The analysis carried out in this paper can be used for more accurate considerations of all cylindrical gear pairs occurrences which depend on load distribution, such as: load capacity, mesh stiffness, vibration, noise, energy efficiency, etc.

Meshing Characteristic of Arc-Toothed Cylindrical Worm Pair and Cutting Geometric Condition of Its Worm

Abstract The arc-toothed cylindrical worm has an arc tooth profile in a section, which may be the axial section, the normal section, or an offsetting plane of the worm helical surface. The meshing principle for a gearing containing such a worm is established. The normal vector of instantaneous contact line is determined in the natural frame and the meshing performance parameters are obtained without the help of the curvature parameters of the worm helical surface to ensure the established meshing principle is concise and practical. The numerical results show that the worm working length can be beyond half of the thread length and the meshing zone of the worm pair can cover most of the worm gear tooth surface. The instantaneous contact lines are uniformly distributed and the worm pair forms double-line contact. The numerical outcomes of the induced principal curvature show that the contact stress level between the teeth is higher in the middle of the worm gear tooth surface and near its dedendum. The forming condition of the lubricating oil film is poorer in the middle of the worm gear tooth surface and from addendum to dedendum as demonstrated by the numerical results of the sliding angle. The normal arc-toothed worm lathed by an offsetting cutter is recommended to apply in industry after various researches and analyses. The cutting geometric condition of the worm is investigated quantitatively. It is discovered that the rule of the cutter working relief angle changes along the cutting edge during lathing the worm.

Analysis of the Influence of Parallelism Error on the Meshing Performance of Circular-Arc-Tooth-Trace Cylindrical Gears

In this paper, two types of point contact and line contact of spiral cylindrical gear transmission pair are studied and analyzed. The influences of the axis parallelism error and the center distance error on the contact area are analyzed. The numerical example shows that the line-contact transmission pair has larger contact area if the installation error is not considered. By using MATLAB software and simulation example, the influence of axis parallelism on contact area and meshing performance of spiral cylindrical gears under different error conditions are obtained.

Analytical kinematics for direct coupled shafts using a point-surface contact

The purpose of the paper is to accomplish the kinematics study of a direct coupling between two shafts with a high pair joint, of point-surface type. Due to Hartenberg and Denavit, the kinematics analysis of spatial mechanisms can be made by a well-known method, named the “homogenous operators method”. This manner is applicable only for spatial mechanisms containing cylindrical pairs with particular solutions: prismatic pair and revolute pair. In order to apply the Hartenberg-Denavit procedure for the two shafts, the contact between the two shafts must be previously replaced by a succession of 5 prismatic and revolute pairs. It results a system of six trigonometric equations with six unknowns that requires a numerical methodology for solving it. The paper aims to obtain an analytical dependency between the motions of the two shafts. To this end, the geometrical condition that defines the connection between the two shafts is directly used. Thus, after all positional parameters are expressed in the same frame of reference an equation between the positional parameters of the two shafts is obtained.

Problems of Friction Force Measurement between Cylindrical Outdoor and Internal Slide Parts

Abstract The article presents the determination of an exemplary measure in the assessment of the technical state of sets of mechanical objects at the stage of manufacture, use and maintenance. The technical state of the assemblies is influenced by the quality of the friction-cooperating elements, the quality of basic functions, the surroundings and the diameter clearance of kinematic node components. Energy wasted to overcome the frictional resistance is a significant part of the energy supplied, which is why current friction losses are minimized. The article includes analysis of the phenomena occurring in the cylindrical pairs in the presence of static and kinetic friction. The many factors affecting the course and values of friction force between cylindrical elements performing relative reciprocating motion have been indicated. The subject of the article is the method of measuring the friction force between a fixed and movable cylindrical element of the mechanical object. The gradual increase of the friction force component takes place by means of easily accessible force. The results of experimental tests of the friction force in different laboratory conditions under are also included. The effect on the measured friction force was investigated: of friction elements geometry and the surface condition after manufacture and/or operation. Scatter results of static friction force depending on the geometry and surface state can be significant. Examples of surface state images are shown. A friction force model was also developed depending on factors affecting its value.

Comparison between the AFNOR Method and the Imposition of Balanced Maximum Specific Sliding in the Imposed Centre Distance Problem

Successive editions of Henriot’s treatise on gears, and an AFNOR document, present an approximate procedure for the choice of profile shift values for the pinion and wheel when a center distance value is imposed in a cylindrical gear pair. That procedure aims at achieving an approximate balancing of the maximum specific sliding values of the pinion and of the wheel. The method involves a loosely defined choice of an auxiliary parameter, but no information is available relating this choice with the level of attainment of the intended balancing of maximum specific sliding values. This assessment, if needed, requires a subsequent analysis for verification.Since no information is available evaluating the procedure, the purpose of this work is to provide a thorough rigorous analysis of the method, highlighting its qualities but also its shortcomings.

Design and Fabrication of Mechanically Controlled Pedorthosis to Treat Congenital Talipes Equino Varus (CTEV)

Objectives: Clubfoot scientifically coined as Congenital Talipes Equino Varus (CTEV) is a deformity in which the afflicted foot appears to be rotated internally at the ankle and shape the subject to walk on the sides of their foot. To diagnose clubfoot deformity non-surgical technique such as serial casting and implementing an Ankle Foot Orthosis (AFO) is preferred over surgical method. This paper aims at developing a mechanically governed non-surgical corrective mechanism that rectifies clubfoot deformity in infants. Methodology: To design the supportive device, following three parameters, are to be considered: Foot Bi-Malleolar angle (FBM), Angle of Plantar Flexion (PF), Angle of Dorsi Flexion (DF). The FBM, PF and DF angle for a healthy infant ranges from 85 - 90˚, 0 - 40˚ and 0 - 22˚ but for a child with clubfoot it is constrained within 50 - 65˚, 0 - 22˚, 0 - 12˚. This deformation can be corrected with the help of mechanically controlled hinge joint and sliding pair mechanism. The orthosis predominantly consists of two main parts sole and cylindrical pair joint. The sole part which is connected to the lower link using a hexagonal nut and bolt creates a hinge joint and thus providing movement along PF. The bottom link in-turn is connected with the cylindrical pair joint and thus allowing 360˚ movement along FBM. Thus hinge joint provides the counter force on the forefoot. Similarly, cylindrical pair joint provides the counter force on mid and hind foot thus directing the bone growth to its pristine. Findings: The initial wearable prototype of the pedorthosis has been proposed, designed and fabricated using thermoforming process. Applications: This wearable orthosis can be fitted to a subject and the growth pattern can be studied. Feasibility of the concept can be understood by virtually evaluating using finite element analysis.

Метрологическое обеспечение и некоторые результаты исследований цилиндрических пар трения

Proposed metrological support of the research of cylindrical pairs on friction and wear al-lows obtaining reliable data about real wear processes. Analysis of the types of wear and pre-sented studies results of specific linear wear of friction pairs with self-lubricating anti-friction plastics showed that an increase in the sliding speed and load - linear wear is reduced. The analy-sis on the influence of the static forces of friction coefficient shows that with load and sliding velocity increasing friction coefficient decreases in all the three cases

Vertical Darboux motion and its parallel mechanical generators

Vertical Darboux motion termed VDM is a special kind of general Darboux motion, in which all the trajectories of the points belonging to the moving body are planar ellipses. The self-conjugation of a VDM in a cylindrical displacement is introduced. The properties and metric constraint of the amplitude of VDM are derived in an intrinsic frame-free vector calculation. For utilizations, single-loop one-degree-of-freedom (1-DoF) primitive VDM generators including isoconstrained and overconstrained realizations are briefly recalled. The main purpose of our article is to synthesize new two-, three- or multi-loop parallel mechanical generators of a VDM. Interestingly, the removal of the fixed cylindrical pair leads to an additional new family of VDM generators with a trivial, exceptional, or paradoxical mobility. The detection of the possible failure actuation of a fully parallel manipulator via the VDM parallel generators is revealed too.

Investigation of Stress State and Contact Pressures in Contact Area of Journal Bearing by Numerical Simulation

Goal of the paper was to investigate stress state and contact pressures in contact pair of tribological assembly by numerical simulation. This paper deals with simulation of cylindrical contact pair. One part has convex (shaft) and other one concave (hole) surface of the body. This assembly represents friction state of the plain cylindrical journal bearing. The paper includes results of stress state and contact pressures from two loading states. The first loading state includes only radial loading without effect of the torque moment and the second one includes radial loading with torque moment. If we want to know more about tribological processes we will have to know stress state in the materials loaded through contact interaction between two bodies to the last detail. This level of knowledge can be achieved just by numerical simulation. The simulation was made by CAE system ANSYS.

Profile Modification of Involute Spur Cylindrical Gear Pair Used in Timing Transmission System of Automobile and its Dynamic Simulation

According to the FEA simulation results of tooth deformations in the mesh process, the profile modification of the involute spur cylindrical gear pairs used in timing transmission system of an automobile are designed based on the methods and theories proposed by domestic and oversea scholars and experts. The dynamic simulations of the gear pairs with straight line modification profile and involute modification profile under different values of modification amounts are done using dynamic analysis software ADAMS. Then it is testified by simulation results that (i)the mesh impact between the gear pairs with involute correction profile is obviously smaller than those between the gear pairs with straight line correction profile and without correction, (ii) optimized value of modification amounts of the gear pairs with involute correction profile is different that of the gear pairs with straight line correction profile under the same work condition.

Investigation on the radial micro-motion about piston of axial piston pump

The limit working parameters and service life of axial piston pump are determined by the carrying ability and lubrication characteristic of its key friction pairs. Therefore, the design and optimization of the key friction pairs are always a key and difficult problem in the research on axial piston pump. In the traditional research on piston/cylinder pair, the assembly relationship of piston and cylinder bore is simplified into ideal cylindrical pair, which can not be used to analyze the influences of radial micro-motion of piston on the distribution characteristics of oil-film thickness and pressure in details. In this paper, based on the lubrication theory of the oil film, a numerical simulation model is built, taking the influences of roughness, elastic deformation of piston and pressure-viscosity effect into consideration. With the simulation model, the dynamic characteristics of the radial micro-motion and pressure distribution are analyzed, and the relationships between radial micro-motion and carrying ability, lubrication condition, and abrasion are discussed. Furthermore, a model pump for pressure distribution measurement of oil film between piston and cylinder bore is designed. The comparison of simulation and experimental results of pressure distribution shows that the simulation model has high accuracy. The experiment and simulation results demonstrate that the pressure distribution has peak values that are much higher than the boundary pressure in the piston chamber due to the radial micro-motion, and the abrasion of piston takes place mainly on the hand close to piston ball. In addition, improvement of manufacturing roundness and straightness of piston and cylinder bore is helpful to improve the carrying ability of piston/cylinder pair. The proposed research provides references for designing piston/cylinder pair, and helps to prolong the service life of axial piston pump.

Contact Fatigue Analysis of Mine Helical Cylindrical Gear Based on ANSYS Workbench

A general method for calculating contact fatigue strength of Mine helical cylindrical gear was studied in this paper. Both the Solid model and finite element model were created in ANSYS. Based on the fatigue analysis module of the ANSYS Workbench, The contact fatigue strengths of the helical cylindrical gear pair were calculated, and corresponding contact fatigue lives and safety factors of two gears in any meshing position were obtained and shown in contour map. A simulation calculation for a pair of mine helical cylindrical gears was carried out. Simulation results show that calculation of the contact fatigue strength of helical cylindrical gear by this method is more scientific and reasonable than traditional empirical method.