Parameters Of Joint Surface Research Articles

Experimental Study on the Wear Characteristics of Textured Joint Surfaces under Bionic Lubrication

Ti15Mo7Zr15Ta1.00Si titanium alloy contained higher concentration of silicon and better elastic properties, excellent biocompatibility and lower processing cost. To investigate the influence of texture shapes and parameters of joint surfaces on the friction and wear properties under bionic lubrication conditions, three types of texture morphologies (circular, elliptical, and equal-width grating) with the same pit depth and surface coating rate were processed on a Ti15Mo7Zr15Ta1.00Si titanium alloy using a picosecond laser processing system in this study. Then, the "ceramic–metal" friction and wear tests of textured and smooth samples under lubrication with bovine serum protein were performed using a UMT-3 multifunctional friction and wear testing machine. The results showed that the surface micro-texture morphology could improve the anti-friction properties of titanium alloy artificial joint materials. The wear resistance of the circular micro-dimples improved with an increase in the circular diameter. In the elliptical micro-dimple texture morphology, the vertical arrangement of the ellipses could provide the maximum bearing capacity and best friction reduction effect, followed by the elliptical morphology and the transverse ellipse arrangement. The denser the arrangement of the equal-width bars, the better the friction reduction effect was.

Analysis of the Creeping Phenomenon of Linear Feed System Based on the Rigid-Flexible Coupling Model

A mathematical model of the creeping phenomenon based on the mechanical model of the linear feed system was established. The dynamic characteristic parameters of each fixed joint were obtained by Yoshimura’s integral. Using the method, only the dynamic characteristic parameters of the joint surface per unit area with simple structure need to be studied, and then, the dynamic characteristic parameters of the whole joint surface can be obtained by integration. Based on the principle of the half-power bandwidth method and the frequency response function identification, the dynamic parameters of each moving joint were solved by the method of experimental modal analysis. Through the parameters of the fixed and moving joints, a rigid body model of the feed system and a flexible body model including the power transmission parts (ball screw pair) and the motion guide parts (guide slide pair and rolling bearing) were, respectively, established. And then, a rigid-flexible coupling dynamic model of the feed system was obtained through the constraint relationships between joints. The influence of both the external load and the feed rate on the fluctuation of motion speed of the system was analyzed from this model. The difference between the experimental results and the simulation results on a feed system platform is not greater than 10%, which verifies the creeping phenomenon. This conclusion can provide a basis for the optimization of the dynamic performance of the ball screw linear-feeding workbench.

Corrections applied to direct shear results and development of modified Barton’s shear strength criterion for rock joints

In present study, 144 direct shear tests are performed on mated rock joint replicas under constant normal load condition (CNL). For these tests, three natural roughness of joint surface are transferred to the RTV silicon rubber molds. On these molds, mixture of cement, sand, and water in the ratio of 1:1.5:0.45 by weight is poured and joint replicas are made. In this study, the experimental shear strength is corrected with gross contact area (Ac) and incremental dilation angle (i). Further, the peak dilation angle is determined by Barton’s and incremental dilation (dv/dh) approaches and compared. The results showed that Barton’s approach underestimates the peak dilation angle. The roughness quantification of joint surface is done using 3D noncontact type profiler, and morphological parameters of joint surface are determined in each shearing direction as described by Grasselli and Egger (Int J Rock Mech Min Sci 40:25–40, 2003). A new predictive model for joint roughness coefficient (JRC) is developed and Barton’s model is modified. It is observed that modified Barton’s model provides good approximation of shear strength in desired shear direction. Moreover, modified Barton peak shear strength (τPre) is compared with Barton and Grasselli’s experimental peak shear strength, and it is observed that τPre matches closely with Barton’s peak shear strength.

Computation of direction dependent joint surface parameters through the algorithm of triangular prism surface area method: A theoretical and experimental study

Grasselli’s (2001) methodology on the quantification of the “shear-induced potential contact zones” is fundamentally very strong at properly dealing with the physics of the shear phenomenon. However, the high precision measurement system and the triangulation algorithm he used may not be easily accessible for everyone due to its industrial characteristics. Therefore, a simple technique called “the modified shear-induced potential contact zones” is introduced in the present work. By executing this technique on the surface coordinates of a large number of rock joints digitized through a specially developed mechatronic surface scanning device, “maximum possible and total potential contact areas” (A0 and Aθ*) and “directional surface parameters” (θ*max: maximum apparent dip angle, c2 : shape parameter, θ*max/c2 : change of angularity) are calculated in a specified direction. Ratio A0/c2 is proposed for a new directional roughness parameter. Surface roughness is also characterized by fractal dimension (Dtp), alternatively. Using a specially developed shear box, shear tests are performed in the direction of parameter calculation. Then, by a series of quantitative comparisons between the directional surface parameters and both the fractal dimensions and the shear strengths, the ability of the parameters to relate with the surface roughness and the shear strength is examined. In general, the results are satisfactory for the reliability of the modified technique. The main advantage of the introduced technique is its algorithmic simplicity facilitating direct applicability for basic 2D data sets, [z = f (x, y)], which can be practically acquired via easily accessible and cost-effective surface measurement systems. Additionally, another simple recipe is also introduced predicting contact zones visually prior to shearing. Then, total potential contact areas predicted in the shear direction are visually compared with the actual images of contacts observed in the tests. The best match is obtained when the threshold apparent inclination (θ*cr) is chosen equal to the experimental dilation angle (id) unique for the applied normal load. This clearly proves the validity of Grasselli’s (2001) “threshold apparent dip angle” concept.

Characteristic analysis on the compression-bending capacity of segmental joint based on the investigated joint parameters

The compression-bending capacity, also known as compressive membrane action, is an important mechanical property of segmental joints. However, owing to a lack of validated calculation methods and quantitative analysis of joint parameters, it has not been applied in the design of segmental joints. Thus, based on a method for calculating the compression-bending capacity of segmental joints proposed previously and joint parameters investigated from a number of practical engineering projects, the characteristic shapes and points of the compression-bending capacity curve are obtained, and the influence of joint parameters on the bearing capacity of segmental joints are quantitatively analyzed. The results show that the compression-bending capacity curve for a segmental joint is a parabolic curve, which can be divided into two parts (parts I and II), where the demarcation point between parts I and II represents that bolt yielding and concrete failure happen at the same time. There are five characteristic points on the curve, based on which four different stress states of the bolt are defined, different characteristic points have different sensitivity to the changes in the joint surface parameters, but the largest changes are all more than double. The influence of segment width and concrete strength on the compression-bending capacity of segmental joints is integral and varies widely, while the influence of the bolt parameters is mainly reflected in small changes at lower axial pressures. The results of this study can provide support and guidance for the design and bearing capacity evaluation of segmental joints.

Research on the micro and dynamic characteristics of combination surface based on fractal theory

Abstract. The dynamic characteristics of the mechanical joint surface are important aspects of the dynamic theoretical analysis and optimization design of the machine tool. In this paper, the typical mechanical joint surface is taken as the research object. Through the combination of theoretical analysis and experimental analysis, the dynamic characteristics of typical joint surface parameters with different surface textures and the influence of texture parameters on the dynamic characteristics of the joint surface are studied. Based on the Hertz elastic contact theory and the contact fractal theory, the normal and tangential contact fractal models of the joint surface are derived, and then a mathematical model of the joint surface normal and tangential contact stiffness considering the domain expansion factor is established. The influence of surface texture parameters on the dynamic characteristics of the surface is further studied according to the model. In addition, the design of the experimental device and experimental scheme design are completed by the contact resonance method and the ERA algorithm, and the joint surface parameter identification experiment with texture is conducted. The normal and tangential frequency response functions of the joint surface, the dynamic characteristic parameters of the joint surface and the influence law of the joint surface parameters on the contact characteristics are obtained through the dynamic test analysis technology.

Optimized Analysis Method for Evaluating the Shear Strength Parameters of Rock Joint Surfaces

The results obtained from the mechanical test of rock samples inevitably suffer dispersion owing to discrepancies between test specimens. In view of these deficiencies, the present study proposes a method based on the empirical equation of shear strength developed by Barton to determine the shear strength parameters of joint surfaces using a single test specimen. This approach is then applied to optimize the analysis of multiple specimens. An analysis of experimental results verifies that the shear strength parameters of joint surfaces obtained by the proposed method can more accurately reflect the shear mechanics of multiple specimens than conventional multiple sample analyses; meanwhile, the results are reasonable and reliable. More importantly, the optimized method ensures the shear strength parameters are no longer affected by the sequence of specimens employed during shear test. The optimized analysis method eliminates the effect of differences between specimens and the influence of subjective factors on test results and therefore provides more realistic evaluations of shear strength parameters.

Creep modeling of asperities on joint surface and its effect on joint surface stiffness

Creep of the asperities on joint surface will change the stiffness characteristics of joint surface. Based on creep mechanics, a novel creep model of asperities between two rough surfaces is established from a microscopic point of view in this paper. The change of joint stiffness caused by creep of asperities under constant pre-tightening force is analyzed. The results show that the creep of the asperities leads to the increase of the stiffness of the joint surface with the increase of time when the joint force is constant. Moreover, the influence of key parameters of joint surface on creep of asperities is further studied. It is found that the change rate of joint stiffness increases with the increase of initial contact distance and contact area. According to the proposed creep model and the findings in this paper, more accurate stiffness characteristics of joint surface can be achieved for analysis of dynamic and static characteristics of structures with time.

TPA and RCSA based frequency response function modelling for cutting forces compensation

In machining process, cutting forces are difficult to measure accurately due to the dynamic characteristic of measurement system. The cutting forces compensation requires the frequency response function (FRF), which cannot be measured in actual production. This paper proposes an effective method for FRF modelling and calculating based on transfer path analysis (TPA) and receptance coupling substructure analysis (RCSA). The measurement system is divided into three substructures: workpiece, table dynamometer with screws, joint surface between two previous substructures. The joint surface is simplified as a spring-damping model with contact stiffness and damping. The FRF of workpiece is obtained by finite element method (FEM), which is adjustable for different workpieces and tool positions. The FRF of dynamometer can be measured only by single impact test. The contact parameters can be identified by a few impact tests, which can be applied to other cutting conditions. The FRF between tool tip and dynamometer output is first derived based on TPA and RCSA. Second, a joint surface parameters identification algorithm as well as its simplified algorithm is presented through a few impact tests. Finally, impact tests and milling tests are implemented for parameters identification, algorithm verification and cutting forces compensation. The experimental results show that the proposed method has sufficient accuracy for the assembly FRF prediction.

Research on static friction coefficient of joint surfaces considering elastic-plastic deformation based on fractal model

In order to study the influence of the microscopic morphology on joint surfaces, it is necessary to consider the elastic-plastic deformation of micro-bulge. Based on the M-B fractal model, the contact fractal models of static friction coefficient with the elastic-plastic deformation considered and not considered are established respectively. Then the models are analysed by changing different characteristic parameters, and the nonlinear relationships between static friction coefficient and characteristic parameters of joint surfaces are revealed. The results show that the static friction coefficient is increased with the normal load and material parameters increase and decreased with the fractal scale parameter increases. And the static friction coefficient is first increased and then decreased with the fractal dimension increase. The static friction coefficients considering elastic-plastic deformation and not are compared. The comparison result reveals that the elastic-plastic deformation has influence on static friction coefficient.

Research on static friction coefficient of joint surfaces considering elastic-plastic deformation based on fractal model

In order to study the influence of the microscopic morphology on joint surfaces, it is necessary to consider the elastic-plastic deformation of micro-bulge. Based on the M-B fractal model, the contact fractal models of static friction coefficient with the elastic-plastic deformation considered and not considered are established respectively. Then the models are analysed by changing different characteristic parameters, and the nonlinear relationships between static friction coefficient and characteristic parameters of joint surfaces are revealed. The results show that the static friction coefficient is increased with the normal load and material parameters increase and decreased with the fractal scale parameter increases. And the static friction coefficient is first increased and then decreased with the fractal dimension increase. The static friction coefficients considering elastic-plastic deformation and not are compared. The comparison result reveals that the elastic-plastic deformation has influence on static friction coefficient.

Bearing deformation of heavy-duty machine tool-foundation systems and deformation detection methods

Because of the characteristics of heavy-duty machine tools such as large self-weight and heavy load, the working precision and service life of their lathe beds, columns, and other large structural parts are all directly influenced by the foundation. In view of the considerable influence of joint surfaces on system characteristics, this study involved obtaining joint surface parameter values from a microscopic perspective, deriving a static joint surface parameter model from Reynolds equation, adopting fractal theory to develop a bolted joint surface parameter model, and thus completing the embedding of joint surface parameters under uneven loads; a simulation model for a heavy-duty machine tool-foundation system was also devised considering the influence of joint surfaces. To identify the structural micro-deformation status of heavy-duty numerical control machine tool-foundation systems, the authors constructed a fiber grating technology-based experimental platform for detecting the deformation of structural parts, verified the correctness of the above simulation model via experiments, and proposed a method for detecting the deformation of heavy-duty machine tool-foundation systems using fiber grating technology. Based on the above simulation model, the influence of reinforced layer position, foundation outline specifications and soil properties around the foundation on the bearing deformation of heavy-duty machine tool-foundation systems were studied, and some guidelines on the construction of concrete foundations were formulated. This model and the related detection method laid a theoretical foundation for guiding the design and optimization of heavy-duty machine tool structure and foundation.

Degradation of joint surface morphology, shear behavior and closure characteristics during cyclic loading

In order to investigate the failure mechanism of rock joint, a series of laboratory tests including cyclic direct shear tests under constant normal load(CNL) conditions were conducted. Morphology parameters of the rock joint surface were precisely calculated by means of a three-dimensional laser scanning machine. All test results were analyzed to investigate the shear behavior and normal displacement behavior of rock joints under CNL conditions. Degradation of rock joint surface during cyclic shear tests was also analyzed. The comparison results of the height parameters and the hybrid parameters of the joint surface during cyclic tests show that the degradation of the surface mostly happens in the first shear and the constant normal loads imposed on the joints have significant promotion effects on the morphology degradation. During cyclic shear tests, joints surfaces evolve from rough state to smooth state but keep an overall undulation. Dilatancy of rock joints degrades with the degradation of joint surface and the increase of normal loads. The closure deformation of joint is larger than that of the intact rock, and the normal stiffness increases with the increase of shearing times.

A Modelling Method of Bolt Joints Based on Basic Characteristic Parameters of Joint Surfaces

Bolt joints are common in machine tools and have a direct impact on the overall performance of the tools. Therefore, the understanding of bolt joint characteristics is essential for improving machine design and assembly. Firstly, According to the experimental data obtained from the experiment, the stiffness curve formula was fitted. Secondly, a finite element model of unit bolt joints such as bolt flange joints, bolt head joints, and thread joints was constructed, and lastly the stiffness parameters of joint surfaces were implemented in the model by the secondary development of ABAQUS. The finite element model of the bolt joint established by this method can simulate the contact state very well.

Experimental Study on Relationship Between Mechanical, Seepage Characteristics and 3D Morphology Parameters of Marble Joint

In order to investigate the influence of 3D morphology parameters of marble joint surface on its mechanical and seepage characteristics, artificial joints of coarse-grained marbles were scanned by Tianyuan OKIO-typed 3D laser scanner; and then, the professional software was used to obtain the 3D morphology parameters of marble joint surface. Tests of water flowing through a single joint were conducted under different normal stress and feeding water head by using self-developed radial flowing system, and the exponential function between flow rate per head and normal stress, the linear relation between equivalent hydraulic aperture and mechanical aperture, and the linear relation between joint closure and normal stress were obtained. The relationships between regression parameters in above three formulas and 3D morphology parameters of joint surface were also studied by fitting method. All in all, the results may provide a reference to understand the mechanical and seepage characteristics of rough rock joint.

Macro and meso characteristics evolution on shear behavior of rock joints

Direct shear tests were conducted on the rock joints under constant normal load (CNL), while the acoustic emission (AE) signals generated during shear tests were monitored with PAC Micro-II system. Before and after shearing, the surfaces of rock joints were measured by the Talysurf CLI 2000. By correlating the AE events with the shear stress-shear displacement curve, one can observe four periods of the whole course of shearing of rock joints. By the contrast of AE location and actual damage zone, it is elucidated that the AE event is related to the morphology of the joint. With the increase of shearing times, the shear behavior of rock joints gradually presents from the response of brittle behavior to that of ductile behavior. By combining the results of topography measurement, four morphological parameters of joint surface, Sp (the maximum height of joint surface), N (number of islands), A (projection area) and V (volume of joint) were introduced, which decrease with shearing. Both the joint roughness coefficient (JRC) and joint matching coefficient (JMC) drop with shearing, and the shear strength of rock joints can be predicted by the JRC-JMC model. It establishes the relationship between micro-topography and macroscopic strength, which have the same change rule with shearing.

A Method of Calculation and Optimization Concerning the Dynamic Parameters of Joint Surface

In this paper, we propose a method of calculation and optimization concerning the dynamic parameters including its normal stiffness and tangential stiffness. We establish a contact model and a dynamic model based on Hertz contact theory, deriving and calculating its normal stiffness and tangential stiffness. Based on the dynamic parameters obtained, we complete the finite element analysis (FEM) and make the modal experiment. verify the correctness and feasibility of the theory model and the FEM model through comparing the theoretical results with the experimental results. On this basis, we establish the dynamic parameters optimization model based on the ANSYS and MATLAB, and successfully obtain more accurate parameters which provide reliable data for the subsequent analysis.

Modal Analysis of High-Speed Face Milling System Based on Composite Structure System Analysis Method

This paper adopts composite structure system analysis method to perform modal analysis of high-speed face milling cutter which is mounted on the machine tool through FEM modal analysis. The key problem of this method is to obtain joint surface parameters between the machine tool spindle and face milling cutter through experimental modal analysis and MATLAB software. The joint surface parameters consist of linear stiffness, linear damping, rotation stiffness and rotation damping. After getting the frequency response function (FRF) at the tool tip of the face milling system through experimental modal analysis, the contact surface parameters can be used to eliminate the influence of the machine tool to get modal parameters of the face-milling cutter itself. Based on the finite element model of face milling cutter, composite structure system analysis method can be used easily to acquire the dynamic performance of the face milling system through FEM modal analysis, greatly to improve the reliability of modal analysis, and is helpful to the dynamic design and the structure improvement of high speed face milling cutter.

Experimental Research on Tangential Dynamic Characteristics of Joint Surface in Motor Frame

Characteristic parameters of joint surfaces are needed in kinetic modeling of the motor frame while analyzing its vibration behavior. In this paper, research on tangential dynamic characteristics of mechanical joint surfaces in the motor frame is executed. In order to get the tangential contact stiffness and contact damping of interfaces in the motor frame under different joint conditions, an experimental method is proposed according to the structure feature and running condition of motors. A test platform is specially designed and set up. The kinetic model of test specimens (including the test joint surfaces) is derived. The experimental system is developed. The tangential dynamic contact stiffness and contact damping are identified by the experimental system. The variation rules of the contact stiffness and contact damping with changing of pre-load, exciting frequency and surface roughness are got and summarized. And the rules are consistent with the physical essence of joint surfaces.

A Vibration and Movement Coupled Modeling Approach of 3 DOF Flexible Joint Manipulators

In order to identify joint contact dynamic parameters of 3 DOF flexible joint manipulators, a vibration and movement coupled modeling approach of the manipulators was proposed. Combining the traveling wave approach of structure and the rotation transformation matrix of joint, the waveguide equations of mechanism were established. Considering the conditions of the general force balance and displacement boundary of each joint, vibration excitation of the system in moving states were obtained. Vibration equations were achieved according to the derived vibration torques and torsional vibration angles. The contact dynamic parameters of joint surface can be identified by using the vibration and movement coupled equation derived in this paper.