Cylindrical Joints Research Articles

Biaxial shaking table tests on a full-scale single-storey traditional Greek stone masonry and timber-framed composite structure

Biaxial shaking table tests were carried out on a full-scale, single-story specimen of a traditional Ottoman-period Greek structure, comprising a stone masonry wall with timber ties and three timber-framed masonry walls with fired clay brick infill. Timber posts and beams were connected with cylindrical mortise-tenon joints. The dynamic characteristics before and after seismic testing were determined with sine sweep tests. The specimen proved capable of withstanding peak ground accelerations equal to the highest seismic zone of Greece. Most damage concentrated in the stone wall, while rocking behavior at the post-sill-beam joints was observed for the timber-framed ones, which only showed minor damages. Finally, interventions are suggested based on the experimental results.

Calculation of the maximum functional clearance of a cylindrical joint between a steel shaft and a cast iron sprocket

Calculation of the maximum functional clearance of a cylindrical joint between a steel shaft and a cast iron sprocket

Determination of the fit of a chain coupling on the gearbox shaft

A calculation of the limit technological interferences in the fit of cylindrical joints with a drive key is developed to ensure their disassembly using a puller in the field conditions. The method is tested on the driven shaft of the Н 090.20 gearbox, which is installed on domestic agricultural machinery. Keywords:gearbox, joint, fit, interference, tolerance, dismountability Pupkova D.A.

Accelerated aging procedure of epoxy structural adhesive for marine offshore applications

Knowledge of the long-term performance of adhesive connections is undoubtedly of paramount importance to enable their deployment in civil, mechanical, and other engineering applications. Over time, adverse environmental conditions can strongly influence the performance of adhesive joints leading to a progressive deterioration of their initial mechanical properties. The use of adhesive connections for secondary structures in offshore applications is a technology that allows for the rapid creation of structural members that, however, cannot ignore the influence of hydrothermal effects on mechanical performance due to environmental conditions. In this context, the investigation of the hygrothermal durability of adhesive connections was undertaken through an extensive experimental programme. More specifically, 130 cylindrical steel joints bonded with a commercially epoxy resin for structural applications were tested in Mode I using an Arcan-modified device. Prior to test, the specimens were placed in climatic ovens capable of combining the effects of temperature and humidity for approximately 320 days. In addition, the glass transition temperature, Tg, was assessed by employing the differential scanning calorimeter (DSC) technique to correctly define the experimental ageing conditions. The experimental results show how ageing conditions influence the mechanical properties of the epoxy resin investigated. Finally, some predictive formulations are proposed to calculate the loss of strength of adhesive joints over time.

A nonsmooth dynamics framework for simulating frictionless spatial joints with clearances

AbstractReal-world multibody systems do not have ideal joints; most joints have some clearance. The clearance allows the connected bodies to undergo a misalignment, and the resulting dynamics is governed by the contacts thus formed. Two approaches are typically taken to deal with contacts: the commonly used continuous dynamics approaches assume the Hertzian nature of the contact modeled by nonlinear unilateral spring-damper elements; while the nonsmooth dynamics approach results in a complementarity problem. This paper employs a nonsmooth dynamics approach to develop a coherent framework for the simulation of multibody systems having frictionless joints with clearances. Because clearances are of small magnitude relative to the dimensions of the mechanical components, the nature of the contact in the joints is assumed to be inelastic. Using this assumption and the general nonsmooth dynamics framework, the parametric formulations for cylindrical, prismatic, and revolute joints with clearances are derived. The equations of motion are formulated, and their time-discretized counterparts are cast as a nonlinear programming problem. The proposed scheme also enforces normalization constraint on Euler parameters in contrast to state-of-the-art methods that is conducive to stability of the solution for a suitable range of step sizes. In addition, a variable time-stepping scheme that includes the step size as an extra variable in the optimization is introduced and its stability properties are discussed. The versatility of the proposed framework is demonstrated through numerical experiments.

A Novel Method for Spatial Structural Kinematic Analysis

Kinematic analysis is the first task that needs to be solved for further real-life problems such as machine dynamics and durability, machine balancing, and optimization, chemistry, etc. Currently, there are many methods to analyze the kinematic problem, for instance: vector graphics method, vector-analytic method, or Dennavit-Hartenberg-Craig matrix method. Although each method has its advantages, they have mostly encountered difficulties in establishing equations associated with complicated spatial structures. This research proposed a novel method, entitled “'perpendicular projection method” to solve the problem of spatial structural kinematic analysis. This is an approximate solution method that combines the use of generalized coordinates and direction cosine matrices. With this method, the problem of kinematic analysis of spatial structures will be solved simply and easily by establishing connection equations as well as simulating the motion of spatial structures. This method was then applied in conducting the kinematic analysis of a spatial mechanism with 1 rotating joint (R), 1 ball joint (S), 1 translational joint (P), and one cylindrical joint (C). The calculated results, including the velocity, acceleration of generalized coordinates, angular velocity, angular acceleration of the links, velocity, and acceleration of the center of mass of the links, showed the efficiency of the proposed method.

An Enhanced Circumferential Winkler Contact Force Model for Cylindrical Clearance Joints

In deployable space structures, the clearance size of joints is small, and the contact between the journal and bearing should sometimes be treated as a conformal contact, resulting in the imprecision of the contact force models in evaluating contact forces. This study proposes an enhanced hybrid theoretical and numerical contact force model to calculate the clearance joints’ contact force. Firstly, a basic formula of a dimensionless contact force is proposed, and an optimized surrogate function of the shape correction coefficient is obtained using finite element method (FEM) and response surface method (RSM). Then, the proposed model is validated by comparing it with various contact force models. Finally, this paper discussed the applicability of the proposed model in detail. These results indicate that the dimensionless expression of the proposed model is reasonable and can reasonably describe the relationship between contact force and penetration depth. The proposed model has been proven to have an excellent correlation with FEM and a minor relative error. The application scope of the proposed model is unlimited to the clearance size and the joint size. The proposed model provides a foundation for accurate impact models and is vital for the structural dynamic problems of high-precision space structures.

სხვადასხვა სიმრუდის ზედაპირზე აგებული ტრანსფორმირებადი, პანტოგრაფული სტრუქტურები

The possibilities to design expandable-foldable structures on various curvature surfaces are considered in the given paper. The presented geometrical layouts are unfolding structures with closed and open contours. The transformable designs are made by an interconnected set of elementary pantographic structure. The elementary transformable structure consists of two levers connected by a transverse cylindrical joint. The considered designs of transformable structures can be effectively used in space structures, in particular deployable space reflectors, also in ground-based transformable structures.

Numerical and experimental study of the conical connection of the blade of a rotary machine

The paper presents an experimental and numerical study of the tapered socket of the aluminum blade root of the mine main ventilation fan, which is based on the tests of a simplified full-scale model with a discarded airfoil and its subsequent finite element analysis. The calculation model takes into account elastoplastic properties of materials and non-linear contacts with friction. The proposed joint consists of an aluminum tapered blade root, two steel retainers with similar tapered surfaces, and two steel bolts that join the retainers around the root. Pre-tightening the bolts allows fixing the blade in an unloaded state in the socket and prevents its unwanted turns. Such a tightening is taken into account in the finite element analysis by means of determining, in compliance with special rules, the axial force of the pretension of the bolts. With the help of a hydraulic press acting on the lower surface of the airfoil root, the effect of the centrifugal load on the conical joint from the side of the blade airfoil is simulated. Nonlinear static analysis of the elastoplastic behavior of the structure allows determining the destructive loads that cause the bolts to break with the subsequent disconnection of the fasteners and the blade to fly out of the seat. The graphs of the equivalent von Mises stresses indicate that the maximum stresses are reached in the working part of the bolts, which fully corresponds to the nature of the destruction of the structure upon reaching the maximum equivalent load on it. The experimental study confirms the correctness of the determination of contact stresses at the tapered socket location. Correspondence of the results of the static analysis with the results of the full-scale experiment makes it possible to draw a conclusion about the correctness of the conducted finite element modelling. This allows using the developed formulation of the problem to determine the strength of rotor structures with conical connections of blades without performing preliminary experimental studies. In addition, the developed technique can be extended to a larger range of conical and cylindrical joints due to the simplicity of the approach and the versatility of the formulation of the nonlinear finite-element problem which models structures with preloaded or tensioned elements.

Shaking table tests on single-bay timber-framed wall specimens with fired brick and adobe block infills and mortise-tenon joints

In-plane uniaxial shaking table tests were carried out on full-scale single-bay timber-framed masonry wall specimens characteristic of Ottoman-period mansions in mainland Greece. The posts were connected to the sill-beam with cylindrical mortise-tenon joints. Two infills were investigated: solid fired clay bricks with lime-cement mortar and adobe blocks with earth mortar. Both specimens proved able to withstand significant base accelerations up to 1.0 g with little damage, exhibiting rocking behavior, with the post tenons lifting up from the mortises due to exceedance of friction at the contact surfaces. The earth material specimen presented higher uplift, top displacement and acceleration. A short comparison with static monotonic and cyclic tests is also presented.

A parametric study on the mechanical properties of MIG and TIG welded dissimilar steel joints

In the present day, the joining of dissimilar metals used in the same industry applications is of great interest. MIG and TIG welding processes are among the most common methods used to join dissimilar metals with high strength and reliability. Due to the different mechanical properties of dissimilar metals to be joined by these welding methods and welding parameters, they must be carefully selected. In this study, the effects of Total Accumulated Weld Volumes (TAWV) and different groove angles (45°, 60°, 75° and 90°) on the mechanical properties of AISI 1040 and AISI 8620 cylindrical steel joints were investigated experimentally. In addition, the fracture surfaces of the samples were examined by scanning electron microscopy (SEM) and energy dispersive X-ray (EDAX). In the process with MIG and TIG welding, only current and voltage changes were made in order to measure the effects of parameters on the mechanical properties of the joints more clearly. As a result of the studies, the highest average Ultimate Tensile Strength (UTS) was 579.611 MPa and the lowest average UTS value was 424.611 MPa. Based on TAWVs, the highest average UTS value was obtained in TIG welded joints, and the lowest average UTS value was obtained in MIG welded joints. It was observed that the UTS values of the joints were positively affected by the increase in TAWV. The UTS value of the 90° groove angled joint was found to be 40.25% higher than the UTS value of the 45° groove angled joint.

The discretization method and multi-contact force model on 3D cylindrical clearance joint for multibody dynamics of spatial mechanical system

The discretization method and multi-contact force model on 3D cylindrical clearance joint for multibody dynamics of spatial mechanical system

Kinematic Investigations of a Novel Flapping Actuation Design with Mutually Perpendicular 3 Cylindrical Joint Approach for FW-Drones

The transmission mechanism of artificial flapping-wing drones generally needs low weight and the fewest interconnecting components, making their development challenging. The four-bar Linkage mechanism for flapping actuation has generally been used till now with complex and heavy connecting designs, but our proposed novel perpendicularly organized 3-cylindrical joint mechanism is designed to be unique and lighter weight with smooth functioning performance. The proposed prototype transforms the rotary motion of the motor into a specific angle of flapping movement, where the dimensions and specifications of the design components are proportional to the obtained flapping angle. Power consumption and flapping actuation can be monitored by adjusting the motor's rotational speed to control the individual wing in this mechanism. The proposed mechanism consists of a crank with three slightly slidable cylindrical joints perpendicularly arranged to each other with a specified distance in a well-organized pattern to produce a flapping movement at the other end. In order to examine the kinematic attributes, a mathematical process approach is formulated, and kinematic simulations are performed using SIMSCAPE multibody MATLAB, PYTHON programming and COMPMECH GIM software. The proposed invention's real-time test bench prototype model is designed, tested and analyzed for flapping validation.

The effect of pin thread on material flow and mechanical properties in friction stir welding of AA6068 and pure copper

This study investigated the effects of friction stir welding thread on the quality of dissimilar joints between AA6068 aluminum alloy and copper. The developed computational fluid dynamic (CFD) method was employed to simulate the tool's heat generation and thermo-mechanical action. The materials flow, microstructure, mechanical properties, and hardness of joints were assessed. The results indicated that the threaded pin increased heat generation during welding. The maximum temperature recorded on the aluminum side was 780 K for the cylindrical joint and 820 K for the threaded pin joint. The size of the stir zone in the threaded pin joint was bigger than the cylindrical pin. On the other hand, mechanical interlocking between AA6068 aluminum alloy and copper increased in the threaded pin joint. The material's velocity and strain rate increased by the higher stirring action of the threaded tool. Higher strain rate and materials velocity decreased microstructure size in the stir zone. The experimental result shows that the ultimate tensile strength of the cylindrical pin joint was 272 MPa, and the threaded pin joint was 345 MPa. The average microhardness of the cylindrical pin joint was near 104 H V, and for the threaded pin was 109 H V. The results show that the ultimate tensile strength and hardness of threaded pin joint increases by 25% and 5% in comparing cylindrical pin joint.

A butt shear joint (BSJ) specimen for high throughput testing of adhesive bonds

ABSTRACT Machine learning is extensively used in material research and development, including adhesion technology. However, it requires a large dataset to train the models for optimizing, developing, and designing new adhesives. This study proposes a novel testing machine that enables quick high-throughput measurements of the shear strength of adhesively bonded joints. A small cylindrical butt shear joint (BSJ) specimen placed in a holder was pushed by a metal specimen pusher until failure; during this process, the force and displacement were recorded. This testing machine can be used to quickly conduct the measurement by simply placing the specimen in a holder and pushing it. A comparison of the average shear strength measured by this method and that measured by single-lap shear tests, coupled with stress analysis using finite element simulation suggested that the proposed method can measure the shear strength more accurately, where a higher level of pure shear can be achieved in the adhesive layers with a lower degree of stress concentration and smaller peeling stress at the extremities of the adhesives. This indicates that the shear strength of adhesively bonded joints can be measured quickly using the proposed testing method, thereby facilitating the development of new adhesives using machine learning.

On the impact strength of adhesive bonded pin-and-collar joints

Nowadays, the adhesive technology is gaining relevance in industrial sectors where impact operating conditions are very common. At the same time, tests on cylindrical joints represent a well-established method for determining the static strength of structural adhesives. This work aims at assessing the impact properties of structural adhesives by means of cylindrical joints. The investigation involved two adhesive formulations (an epoxy resin and an anaerobic) and has been carried out under static, quasi-static and low-velocity impact conditions. The main outcomes of the work are: (i) the pin-collar specimen is well suited to analyzing the impact properties of adhesives; (ii) both adhesives showed a dependence of the strength and stiffness properties on the strain rate; (iii) the epoxy product showed a greater impact toughness than the anaerobic. In appendix, the authors report the tuning procedure of a CZM numerical model in a commercial FE package, based on the experimental results.

Robosample: A software using constrained molecular dynamics coupled with Gibbs sampling to investigate macromolecules.

An ongoing challenge for the simulation of macromolecules is their complex potential energy surface which is a result of high dimensionality and chemical complexity. The surface contains high energy barriers usually difficult to overcome by existing simulation methods. We present here Robosample, a software combining the advantages of robot mechanics for fast constrained simulations and of Gibbs sampling for achieving ergodicity. While energy calculation is the main computational bottleneck for macromolecule simulations, a big part of the work can be short-circuited by increasing the trajectory integration timestep. Usually this is achieved by modifying the system's mass matrix. The way this is implemented in Robosample is by using constraints in the framework of reduced coordinates. A good example is torsional dynamics, which transforms the system in Bond-Angle-Torsion coordinates and then ignores the motion of the bonds and the angles. Robosample sampling method is Hamiltonian Monte Carlo coupled with Gibbs sampling (GCHMC), with random variables divided among molecular degrees of freedom. With GCHMC, certain molecule segments are considered rigid and sub-sampled, while focusing on soft degrees of freedom as Gibbs blocks. Ergodicity is achieved by interleaving fully flexible Cartesian dynamics Monte Carlo proposals. The validity of the method was first proven on small systems correctly reproducing alanine dipeptide free energy landscape and showed to increase sampling efficiency of macrocycle containing small molecules which are notoriously difficult to simulate. The software was subsequently extended to include spherical and cylindrical robotic joints and proved to be efficient on medium sized biological molecules, such as glycans. Now we have reached a stage where we can successfully sample big macromolecules such as antibodies on graphical processing units.

Comparison of microstructure, texture, and mechanical properties of the SQ and thread pin profile FSW joint of AA6061-T6 with Al2O3 particle reinforcement

The paper presents the effect of flat and thread pin profiles on friction stir welding (FSW) of 6061-T6 aluminium alloy with particle reinforcement. The thread geometry on the tool pin enhances the material mixing and improves the material flow in the plastic state. However, in the flat tool pin, the plasticized material was stuck to the side faces of the tool pin surface. The microstructural analysis of the weld specimen revealed that the powder particles were agglomerated in the stir zone (SZ) region in the square tool pin case. However, the powder particles were homogeneously dispersed in the SZ region when the welding was done with the threaded tool pin profile tool. The tensile and hardness tests were also conducted to check the flat and threaded cylindrical pin weld specimen's joint strength and hardness variation. The Electron backscattered diffraction (EBSD) analysis revealed that the average (Av.) grain size of the SZ region of the TCT and SQ pin are 3.74 µm and 5.64 µm, and the fraction of high angle grain boundaries are 0.560 and 0.368, respectively. The texture analysis of the SZ region revealed that the major availability of the shear texture component B/ B ̅ and C in the TCT pin weld specimen.

Improvement of tribological characteristics of coupling parts "shaft-sleeve" with polymer and polymer-composite materials

The article provides an analytical justification of the flow of tribological processes of coupling of "shaft-sleeve" parts, which simulates the functioning of sliding bearings and cylindrical joints of machines. The main attention is paid to such characteristics as contact pressure, static and dynamic forces, the criterion of the product of the total pressure on the sliding speed, the work of friction forces and its transition into thermal energy in the friction zone for polymer (based on polyamide P-68) and polymer-composite coatings (based on P-68 with kaolin filler) on the working surfaces of the parts. A comparative analysis of the functioning and tribological characteristics of the couplings of parts without coatings is presented.
 Experimentally, on the basis of tests of samples on the MИ-1M friction machine, a significant reduction in wear and an increase in the relative wear resistance of samples with polymer-composite coatings in the modes of friction without lubrication (by 1.3...1.4 times) and marginal friction (in 1.2...1.3 times), as well as a decrease in the temperature in the friction zone (365 K and 347 K) compared to the polymer coating.

Analysis of a Stress-Strain State of a Cylindrical Tank Wall Vertical Field Joint Zone

In the study, experimental and theoretical studies were carried out to assess the influence of the vertical mounting joint zone of the tank on the stress-strain state of the defect zone. Thus, experimental tests of models of a tank wall fragment with an imperfection of the mounting joint evaluated the stress-strain state of the mounting joint zone and established the dependence of the stress concentration in the joint zone on the deflection, the width of the zone and the thickness of the tank wall. It is shown that with a 50 mm bending boom, the annular stresses increase by 1.3 times than with a 30 mm bending boom and the meridional stresses increase by 1.16 times. The same nature of the increase is observed with the stress concentration indicator. By numerical analysis of the stress-strain state of tanks with joint imperfections in the ANSYS medium, the stress-strain state of the tank is estimated for various values of the joint bending parameters ς and ξ. The dependences of the stress concentration coefficient on the geometric dimensions of the imperfection, radius and thickness of the tank wall are also obtained. From the results of calculating the stress concentration coefficient, with an increase in the dimensionless parameters ς and ξ, the values of the stress concentration coefficient Kσ increase by 1.35 times. As a result of the calculations, an interpolation polynomial (5), approximating the stress concentration coefficient Kσ, is obtained, which can be used to estimate the strength, durability and residual resource of the tank. In addition, the obtained results can be used to normalize the limiting dimensions of the imperfection of the joint and to establish the values of the coefficient, taking into account the peculiarities of the work of structures at stress concentrations.