Smooth Cylindrical Surface Research Articles

ANALYTICAL MODELLING OF THREAD TENSION ON A SYSTEM OF SURFACES

The paper deals with the determination of the tension of a flexible thread using numerical methods. The equilibrium of a homogeneous inextensible heavy thread, when statically interacting with a system of surfaces of various shapes, has been simulated. The paper presents the results of analytical modelling of thread tension. The formulas for calculating the tension at any point of thread by characteristic sections and the normal pressure at critical points have been derived. An example of calculation of thread tension on two smooth cylindrical surfaces and a rough surface of a cone simulating some working bodies of textile machines has been given. The normal pressure on the thread sections at the points dangerous, with respect to contact disturbance, has been determined. After solving all the equations and determining their components, a mathematical model of heavy thread tension at static equilibrium has been constructed using the points found.

Thick-panel origami-based parabolic cylindrical antenna

This paper proposes a novel parabolic cylindrical antenna with great folding efficiency based on two symmetrically arranged Miura-ori thick-panel origami patterns and the removal of partial material from each panel. A design rule for the transition from the given parabolic equation to the geometric parameters of the thick-panel origami is defined. To ensure that the deployable structure has one degree of freedom (DOF), specific connectors between the two thick-panel origami patterns are designed from spherical 4R linkages and Bennett linkages, which are verified by kinematic analysis based on the assembly of linkages corresponding to the thick-panel origami pattern. Two joint-removing techniques based on the kinematic equivalence of linkages are constructed to obtain the continuous and smooth parabolic cylindrical surface and maintain the one-DOF property. The deployed/folded ratio influencing factors are fully studied, finding that a small panel thickness and a large origami pattern sector angle are necessary to obtain a high deployed/folded ratio. Finally, a prototype of the deployable structure is manufactured to verify and demonstrate its excellent performance.

Developing an effective deflector for duct natural ventilation

Information is given on increasing the available gravitational pressure of natural duct ventilation by increasing the use of wind flow energy. The scheme and operation of the developed deflector with a vertical finned cylindrical surface based on the CAI deflector are described. The laboratory bench scheme developed and patented for evaluating the efficiency of various types of deflectors is presented. Thermo-anemometer was used in experimental studies as instrumentation TKA-PKM (52), as well as a wing type anemometer. The effectiveness of the developed deflector was evaluated using the mathematical method of planning and processing of experiments. Scientific and experimental investigations were carried out on the basis of an orthogonal composite plan of the first order. A complete factorial experiment was carried out in CFE 23. A regression equation adequately describes the influence of the design and process parameters on the air velocity in the natural ventilation duct at the significance level = 0.05. Experimental studies have confirmed that it is possible to increase the degree of utilization of wind stream energy when it flows over a vertical finned cylindrical surface in comparison with a smooth cylindrical surface. It is shown that air velocity in exhaust duct can be increased up to values of 3.35 m/s. α

Thermo-hydrodynamics of multiple drops impinging simultaneously on the grooved tubular surface and smooth cylindrical surface with different wettabilities

This study used the VOF method to present the intrinsic thermo-hydrodynamics of multiple drops impinging on the grooved tubular surface and smooth cylindrical surface at the same time. Furthermore, the wall surface wettability was investigated for its influence on dynamics and heat transfer. The results show that for the hydrophilic surfaces, the non-dimensional liquid film contact area on the smooth cylindrical surface is approximately-four times as large as that on the grooved tubular surface. The height of the central uprising sheet on the smooth cylindrical surface outweighs that on the grooved tubular surface due to the corrugations’ inhibition and anisotropy of tubular surfaces. Moreover, the latter exhibits a significantly higher convective heat transfer coefficient, nearly-four times that of the smooth cylindrical surface initially. Compared with a stable liquid film on the grooved tubular surface, the variable liquid film on the smooth cylindrical surface affects the temperature distribution significantly. When the surface becomes hydrophobic, the corrugations’ inhibition is highlighted. As surface hydrophobicity increases, the difference in the liquid film contact area and global heat flow is smaller between two surfaces. In the stable stage, the enhancement of the convective heat transfer coefficient on the hydrophobic grooved tubular surface is strengthened.

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The proposed scientific work considers and substantiates an effective method for selecting interference fit on smooth cylindrical surfaces of parts, which can be successfully applied in automated design of fit. Based on the analysis of numerical and analytical research of the results of calculation and design of the considered joints, a flat image of a mathematical model of the area of existence of geometric parameter values in a two-dimensional coordinate system (diameter and working length of the fit) was first obtained. At the next stage of modeling many alternative i-th standard interference fits were built. Within each i-th object centers of grouping rational values of geometric parameters were defined. They are formed by crossing the largest segments of allowable ranges of changing values of diameter and working length in each of the models of sets. The position of such centers is analytically described using the mathematical apparatus of the theory of R-functions. On the considered specific example of this research, the criterion for choosing a rational standard interference fit is formulated depending on the values of geometric parameters. The meaning of this criterion is that within the flat geometric image of the model, the shortest distance is analytically determined - the segment between the points of the grouping centers of the model of set of the �-th fit and the model of the area of existence of values. The effectiveness and advisability of the formulated criterion is illustrated by comparison with other criterions obtained in previous researches of the authors. As a result of the research, it was revealed that the task of choosing a single rational design solution is significantly simplified if several criterions of one of the alternative fits coincide.

О разработке электромеханического привода с шарико-винтовой передачей, защищенной от заклинивания

At present, one of the most pressing issues is the problem of improving electromechanical drive reliability, specifically, eliminating the possibility of jamming in the ball screw. The paper proposes an engineering solution designed to replace expensive imported ball screws. We analysed alternative designs intended to improve electromechanical drive reliability. We proposed and patented a ball screw design featuring a separator, in which the nut acts as a piston. The structure consists of a smooth cylindrical body and a slotted separator, its slots positioned along a helical line with a step equal to the thread lead. The body and the separator are coaxial and rigidly fixed together at the separator end faces so that the rolling elements remain in contact with the screw thread surfaces, the internal smooth cylindrical surface of the nut body and the surfaces of the separator slots. The ball screw design proposed, which features a nut with no internal threading, significantly simplifies the structure and its manufacturing technology. We built a model of an electromechanical drive equipped with a recirculating ball screw in order to determine static and dynamic properties of an electromechanical drive containing a ball screw featuring a separator. We compared the strength of the ball screw designs considered. As the ball screw featuring a separator is simpler and more reliable, the results of our analysis and the properties of an electromechanical drive equipped with the design proposed show that it is a promising solution to the import substitution problem concerning recirculating ball screws

КРИТЕРІЙ ВИБОРУ РАЦІОНАЛЬНИХ ЗНАЧЕНЬ ПАРАМЕТРІВ ПОСАДКИ З НАТЯГОМ ПРИ АВТОМАТИЗОВАНОМУ ПРОЕКТУВАННІ

The proposed scientific work considers and substantiates a new approach to selection of rational values of basic geometrical parameters of interference fit at their automated design – a fitting diameter and working length. A geometric and analytical model of the area was constructed, in which there are values of the basic parameters of fit. Then, numerical and analytical researches of this model were carried out. Based on the results of this research, an analytical criterion for choosing rational values of geometric parameters is formulated. The proposed method is based on the definition of the center of intersection of the largest segments of the permissible ranges of changes in the values of diameter and working length. This center is represented as some coordinate point within the model in the two-dimensional coordinate system. The coordinate axes of this model use the fitting diameter and the fitting length. The position of this point is analytically described using the mathematical apparatus of the theory of R -functions. These parameters are used in the automated design of the interference fits on the smooth cylindrical surface for jointed components of the direct engagement mechanical gears, for example, for the bandage joint of the ring gear to the wheel hub. This does have a keyless joint, the torque is fully transmitted by the friction forces in the fit. Such joints are used in the units and mechanisms used in small arms and artillery and military equipment, as well as other technical products of general-engineering purpose at various methods of assembly by a method of full interchangeability. The effectiveness of the method is shown in a specific example of numerical calculation, the results of which are obtained using the software developed by the team of authors of this work

Study of aerodynamics of the jet spreading over cylindrical surface

The purpose of this work is to study the fields of average values of velocity in a turbulent air jet propagating along a smooth cylindrical surface with an adjustable nozzle width being b, the curvature parameter SR and Re number on both convex and concave surfaces. To identify basic patterns of physical phenomena occurring in the boundary layer, it has been established that in universal coordinates, the wall velocity profiles have a universal nature in the region of a change in the curvature parameter 0 ⩽ SR ⩽ |±0.12|, and virtually coincide with the velocity profiles of a turbulent boundary layer on a flat plate in a uniform flow past, except for the velocity peak region. This is due to the fact that the longitudinal pressure gradient is 104 ÷ 105 times lower than transverse pressure gradient. According to our data, it has been established that the excess static pressure near the streamlined surface with a distance from the nozzle and an increase in jet thickness can reach up to 30–40% of the velocity head.

Effect of wedge coupling in smooth cylindrical surfaces contact

The possibility of obtaining the wedge coupling effect in the contact of smooth cylindrical surfaces is considered in the article. Theoretical dependences are obtained to determine the magnitude of the reduced friction coefficient, realized in coupling of unrun and run-in cylindrical surfaces. The correctness of choice of the pressure law on cylindrical surfaces and the proposed theoretical dependencies is experimentally confirmed. Empirical values of the reduced friction coefficient for a “steel-steel” friction pair under oil lubrication conditions are obtained. It is shown that the value of the reduced friction coefficient in the proposed type of coupling of cylindrical surfaces increases 2.6…5.7 times in comparison with the actual friction coefficient.

An elastoplastic fractal model for cylinder in contact with a smooth plane

A mechanical model of which a cylinder-based fractal body in contact with a rigid plat surface presented based on fractal theory. The generalized Weierstrass-Mandelbrot function is employed to derive the formulae of fractal surface asperities formed a smooth cylindrical surface. The existing conditions of which a single asperity is in elastic, elastoplastic or full plastic deformation are derived. When the cylinder-based fractal rough is uniformly divided into N subdivisions, a relation between the N subdivisions and the asperity geometric dimensioning is obtained. A modified size distribution function is adopted to obtain the relation between the dimensionless contact load and the real contact area. The results show: the critical areas of a single asperity are scale dependent. With an increase in the contact load and contact area, a transition from elastic, elastoplastic to full plastic deformation takes place in this order. The mechanical properties of the cylindrical rough surface are related to the range of the asperity frequency indexes. When the first six asperity frequency indexes are less than critical elastic frequency index n ec, the rough surface appears to be elastic property under contact load. When the first six asperity frequency indexes are between the critical elastic frequency index n ec and critical plastic frequency index n pc, the rough surface appears to be elastic property and elastoplastic property, otherwise the rough surface appears to be of inelastic property.

Light source optimization for automatic visual inspection of piston surface defects

This paper focused on the light source optimization for visual inspection of piston surface defects. A novel structured lighting system was developed to overcome the difficulties in the well-qualified imaging of tiny and random defects on the cylindrical smooth surface of components such as pistons. A polarized light-filtering based method was proposed to enhance the defect image contrast, enlarge the detection range, and suppress the noise of flawless area. It was both experimentally proven and theoretically proven effective by mathematical modeling of light intensity loss during light propagation. To analyze the influence of the pose and position of light sources on defect imaging quality, the system model for camera, light source, and workpiece was established, and the structure parameters of the lighting system were optimized to improve the brightness uniformity over the entire inspection region and lighting efficiency. Moreover, a soft lighting method was introduced as a subsidiary means of removing the surface noise at two ends of a piston. This method was found to be more effective compared with conventional software filtering algorithm. Finally, a case was examined. The defects on the automotive brake master piston surface were captured using the optimized light source system. A random sampling experiment with 600 specimens revealed that the false-positive rate was about 2.3%, and with no leak detection. The findings have been applied in the production, and it is expected to be referred in inspecting defects on other smooth cylindrical surfaces.

TUNNEL POINT CLOUD FILTERING METHOD BASED ON ELLIPTIC CYLINDRICAL MODEL

The large number of bolts and screws that attached to the subway shield ring plates, along with the great amount of accessories of metal stents and electrical equipments mounted on the tunnel walls, make the laser point cloud data include lots of non-tunnel section points (hereinafter referred to as non-points), therefore affecting the accuracy for modeling and deformation monitoring. This paper proposed a filtering method for the point cloud based on the elliptic cylindrical model. The original laser point cloud data was firstly projected onto a horizontal plane, and a searching algorithm was given to extract the edging points of both sides, which were used further to fit the tunnel central axis. Along the axis the point cloud was segmented regionally, and then fitted as smooth elliptic cylindrical surface by means of iteration. This processing enabled the automatic filtering of those inner wall non-points. Experiments of two groups showed coincident results, that the elliptic cylindrical model based method could effectively filter out the non-points, and meet the accuracy requirements for subway deformation monitoring. The method provides a new mode for the periodic monitoring of tunnel sections all-around deformation in subways routine operation and maintenance.

TUNNEL POINT CLOUD FILTERING METHOD BASED ON ELLIPTIC CYLINDRICAL MODEL

Abstract. The large number of bolts and screws that attached to the subway shield ring plates, along with the great amount of accessories of metal stents and electrical equipments mounted on the tunnel walls, make the laser point cloud data include lots of non-tunnel section points (hereinafter referred to as non-points), therefore affecting the accuracy for modeling and deformation monitoring. This paper proposed a filtering method for the point cloud based on the elliptic cylindrical model. The original laser point cloud data was firstly projected onto a horizontal plane, and a searching algorithm was given to extract the edging points of both sides, which were used further to fit the tunnel central axis. Along the axis the point cloud was segmented regionally, and then fitted as smooth elliptic cylindrical surface by means of iteration. This processing enabled the automatic filtering of those inner wall non-points. Experiments of two groups showed coincident results, that the elliptic cylindrical model based method could effectively filter out the non-points, and meet the accuracy requirements for subway deformation monitoring. The method provides a new mode for the periodic monitoring of tunnel sections all-around deformation in subways routine operation and maintenance.

Evaluation of the maximum axial force on a cylindrical shell structure in terms of stability and strength using fuzzy quantities of chosen geometric parameters

The paper deals with the application of the fuzzy sets theory for determining the maximum axial load of a pin-supported smooth cylindrical shell surface. It takes into account the stability and strength criteria, using fuzzy shell radius and plate thickness data. The formulated optimisation problems relate to fuzzy chance-constrained programming (CCP) models. A Monte-Carlo simulation modelling algorithm is proposed. Computational experiments were performed as part of the study. The proposed method can be used for designing and assessing the load-bearing capacity of structures such as bridges and railroads when faced with incomplete or time-varying input data.

A Novel Method for Smooth Blending Cylindrical Surfaces Whose Axes are Non-Coplanar with Intersecting Line of Two Tapered Surfaces

A novel method is proposed by constructing the intersecting line of two tapered surfaces to smooth blending non-coplanar axes. Necessary and sufficient conditions for smooth blending two non-coplanar cylindrical surfaces are achieved. Specific example is also provided.

The problem of mechanical compatibility of natural building stones in the restoration of monuments. Part II: Specimens with modified boundaries

AbstractIt was pointed out in Part I of this short two-paper series, that the mechanical incompatibility between the authentic building stone of ancient monuments and the stones used as substitute ones during restoration projects, may be the reason of violation of basic restoration principles concerning the protection of the ancient material. In this context certain geometrical configurations of the boundaries of the specimens are examined in this Part II as a possible means of modifying the mechanical behaviour of the substitute stones, in order to make them as compatible as possible with the authentic material. Modifications of both the contact surfaces (in order to change the friction conditions) of the specimens as well as of the free ones (in order to quantify the influence of transforming the smooth cylindrical surface to a fluted one) are examined experimentally. This approach is based on existing observations and numerical studies indicating that the behaviour of a stone specimen in the post-peak region is affected by the geometrical configuration of its boundaries. Taking advantage of the experimental results an alternative compatibility criterion is introduced for situations where the “required” quality of the building stone is its ability to withstand deformation without failing structurally, a characteristic pertinent to statically indeterminate structures, whose design is based on deformation control. This criterion combines both peak stress and maximum failure strain providing a better insight into the problem of mechanical incompatibility of natural building stones.

A microcontact model developed for sphere- and cylinder-based fractal bodies in contact with a rigid flat surface

The present study examines sphere- and cylinder-based fractal bodies in contact with a smooth and rigid flat surface. The generalized Weierstrass–Mandelbrot function (the W–M function) is employed in combination with the radius–vector function method (the (r, θ) method) to derive the formulae of fractal surface asperities formed on a smooth spherical surface and a smooth cylindrical surface. The size distribution functions used to calculate the contact load and the real contact area of an apparent area were derived for the three deformation regimes of microcontacts. The non-Gaussian probability density functions for two contact forms (cylindrical and spherical) were developed by combining the probability density functions developed for all small elements in the contact area using the superposition technique. In the present model, the deformation behavior demonstrated in the elastic, elastoplastic, and fully plastic deformation regimes is consistent with that described by classical (statistical) theories. Both the contact load and the real contact area results predicted by the present fractal model at various minimum separations show very good agreement with the results obtained using the statistical method. However, the results also exhibited properties very different from the results predicted by the unmodified fractal model, which showed the microcontact behavior demonstrated in the three deformation regimes to be exactly opposite to that predicted by the classical theories.

The influence of substrate curvature on neurite outgrowth is cell type dependent

Damage to axonal tracts of the central nervous system results in costly and permanent disability. The observations of aborted neurite outgrowth and disorganized scarring in injured central nervous system tissue have motivated the hypothesis that engineered bridging devices might facilitate regeneration. It is thought that both the shape and surface chemistry are important design parameters, however, their relative importance is poorly understood. Previously, we utilized smooth cylindrical surfaces to demonstrate that surfaces designed with directionally varying curvature bias in a stereotyped way postnatal dorsal root ganglion axonal regeneration in the direction of minimum curvature independent of surface chemistry. In the present study, we extend this analysis to include adult dorsal root ganglion neurons and cerebellar granule cells, cell types more representative of the challenge faced clinically. We found that axonal outgrowth of both the adult neuron and the central neuron was less sensitive to substrate curvature than the outgrowth of the postnatal neurons. These differences were quantified by constructing distributions describing the probability of outgrowth for a defined range of surface curvatures. Both the adult neuron and the central neuron exhibited a higher probability of extension in high-curvature directions compared to the postnatal neuron implying that surface geometry may not be as potent a cue in directing the regeneration of these neurons. A microtubule-stabilizing agent enhanced the sensitivity to curvature of the adult neuron, partially reversing the increased probability of growing in a high-curvature direction. The results suggest novel methods to enhance directed neuron regeneration using bridging substrates.

Conformational behavior of polymers adsorbed on nanotubes

The importance of hydrophobic interactions in determining polymer adsorption and wrapping of carbon nanotubes is still under debate. In this work, we concentrate on the effect of short-ranged weakly attractive hydrophobic interactions between polymers and nanotubes (modeled as an infinitely long and smooth cylindrical surface), neglecting all other interactions apart for chain flexibility. Using coarse-grained Monte Carlo simulation of such simplified systems, we find that uniform adsorption and wrapping of the nanotube occur for all degrees of chain flexibility for tubes with sufficiently large outer radii. However, the adsorbed conformations depend on chain stiffness, ranging from randomly adsorbed conformations of the flexible chain to perfect helical or multihelical conformations (in the case of more concentrated solutions) of the rigid chains. Adsorption appears to occur in a sequential manner, wrapping the nanotube nearly one monomer at a time from the point of contact. Once adsorbed, the chains travel on the surface of the cylinder, retaining their helical conformations for the semiflexible and rigid chains. Our findings may provide additional insight to experimentally observed ordered polymer wrapping of carbon nanotubes.

Lubrication and Wear of Artificial Knee Joint Materials in a Rolling∕Sliding Tribotester

This paper describes the influence of lubrication on wear during testing of materials for artificial knee joints in a rolling∕sliding tribotester built to simulate contact conditions in a total knee replacement. The test configuration consists of parallel cylinders (pucks) of ultrahigh molecular weight polyethylene (UHMWPE) and polished cobalt-chrome alloy in oscillatory rolling∕sliding contact in a bath of dilute (25%) bovine serum. Wear tests of three different UHMWPE materials were run under constant load at 40% sliding for 1.5 million oscillation cycles at 1.5cycles∕s. Wear of the UHMWPE was determined by measuring the profile of the cylindrical contact surface of the puck before and after each test. Profile measurements were repeated after at least 53days to eliminate the contribution from creep. Differences between initial and final profiles were attributed to wear of the UHMWPE. It was found that the largest wear depth in the lubricated tests occurred near the ends of the oscillatory contact area, while dry (unlubricated) tests of the same materials showed a peak wear depth near the center of the contact area. In the lubricated tests, the worn depth was lowest for the most heavily irradiated material. Analysis of the elastohydrodynamic lubrication in the rolling∕sliding contact was carried out assuming a line-contact situation with smooth cylindrical surfaces. The time-dependent modified Reynolds equation and the elasticity equation with initial conditions were solved numerically using a multigrid technique with full approximation scheme, and using a Newton Raphson method to solve the highly nonlinear system of equations. The thickness of the lubricating film of bovine serum was determined for points along the length of the wear track. It was found that the smallest film thickness (hmin) occurs very close to the location in the oscillating contact where the greatest wear occurs, owing to the very low entraining velocity near the ends of the oscillation cycle. The coefficient (K) for wear of the UHMWPE was found to be relatively constant over the central section of the oscillatory motion, but increased to a higher value where hmin decreased to near zero. Thus, the important influence of lubrication on wear of artificial knee bearings was demonstrated.