Definition of the microtopography of surfaces in thermal contact (2023)

Quoted by (24)

  • A thermal creep model for nominally flat surface contact: Jeffrey's linear viscoelastic model

    2011, International Journal of Mechanical Sciences

    Quote excerpt:

    A slightly improved version of the GW model presented in [3] still treats the rough surface asperities as spherical shells, but there the curvature of the spheres is not constant and instead depends on the height of the asperity [6]. Other studies [7,8] have shown that the statistical parameters are ambiguous and depend on the length of the sample examined and the resolution of the measuring device. Due to this fact, using these parameters represents an oversimplification of real surfaces containing different roughness scales.

    This thesis deals with the contact mechanics of thermoviscoelastic materials. In particular, the creep behavior of a nominally flat rough surface in contact with a rigid half-space is studied. The rough surface is modeled using fractal geometry. A synthesized profile, a Cantor structure, is used to model the surface. Such a profile has two scale parameters and different heights for each generation of bumps. The influence of temperature is accounted for by the concept of activation energy using the Arrhenius equation.

    The aim of this model is to study the normal onset of creep of the surface (stamp) as a function of the applied creep load, time and temperature. The stamp material is assumed to behave according to the Jeffreys model. Such a model is an arrangement of springs and dampers in parallel and/or in series.

    The creep approach of linear viscoelastic materials is investigated using an elastic-viscoelastic correspondence analysis. An asymptotic power law is obtained relating the global force and temperature acting on the stamp to its approximation. This model is only valid if the approach between the punch and the half-gap is in the range of the roughness size. The proposed model allows an analytical solution in case the deformation is linear thermoviscoelastic. The obtained model shows a good agreement in comparison with the experimental results from the literature.

  • Evaluation of technical surfaces using a combined method of fractal modeling and wavelet analysis

    2001, International Journal of Machine Tools and Manufacturing.

    A new approach based on the combination of wavelet and fractal theories is proposed. The purpose is to provide a mechanism to more accurately and completely evaluate the properties of engineered surfaces. Wavelet transformation models and fractal representations of technical surfaces are presented and the combination of wavelet models and fractal representations is examined. With the proposed approach, experimental samples of the workpiece surface obtained by grinding are examined. The results show that the proposed approach is correct and complete.

    (Video) Straumann SLActive®
  • Surface Roughness Modeling for Piston Ring Lubrication: Solving the Problems

    1996, Tribology Series

    Friction models for piston rings and other machine elements often include the Greenwood and Tripp contact model and the Patir and Cheng average flow model for the mixed lubrication mode. However, problems arise from the non-Gaussian roughness height distributions of cylinder liners and from the unsteadiness of the surface roughness parameters used in these models. This article shows how to solve these problems. From this it is concluded that the upper part of the coating roughness height profile has a Gaussian distribution and this is used to determine the appropriate roughness height for use in the friction model. The non-stationarity is solved using the plasticity criterion proposed by T R Thomas. This idea has not received much attention in the literature and experimental support is still lacking. In this work, an experimental validation is provided and it is concluded that both the use of the proposed solution for the non-Gaussian liner roughness and the application of the Thomas plasticity criterion allow an accurate prediction of the piston ring friction.

  • Fractal characterization and simulation of rough surfaces

    1990, wear and tear

    Roughness measurements on various machined steel surfaces and a structured thin-film magnetic disk have shown that their topographies are multiscale and random. The power spectrum of each of these surfaces follows a power law within the considered length scales. This spectral behavior implies that as the surface is repeatedly magnified, statistically similar images of the surface continue to appear. In this paper, the fractal dimension is identified as an intrinsic property of such a multiscale structure and the Weierstrass-Mandelbrot (W-M) fractal function is used to introduce a new and simple method for roughness characterization.

    The power spectra of the stainless steel surface profiles coincide at high frequencies and correspond to a fractal dimension of 1.5. It is hypothesized that this coincidence occurs on small length scales, since the surface remains rough on such scales. Surface processing such as grinding or lapping reduces power at lower frequencies up to a certain corner frequency, above which all surfaces behave like raw surfaces.

    The W-M function is also used for deterministic simulation of rough Brownian and non-Brownian surfaces that show statistical similarity to real surfaces.

  • references

    1990, Tribology series

    (Video) Straumann SLActive Surface

  • Electrical Contacts: Fundamentals, Applications and Technology

    2017, Electrical Contacts: Fundamentals, Applications and Technology

View all articles citing in Scopus

Featured Articles (6)

  • investigative article

    A mathematical model for simulating and manufacturing ball end mills

    Computer Aided Design, Band 50, 2014, S. 16-26

    The performance of ball end mills in cutting operations is affected by the configuration of the rake and flank faces on the spherical component. From the mathematical design of a cutting edge curve, the rake face can be defined by the rake angle and rake width at each cross-section along the cutting edge. We propose the basic conditions that should govern the coupling between the grinding wheel and the release surface in order to avoid interference during the processing of a ball mill. As a result, a new mathematical model for determining the position of the wheel and a software program for simulating the generation of the contact surface of a ball mill are proposed. In addition, methods for grinding the flank in both concave and planar forms are presented. The groove area created by a disc during the grinding process is determined using a tangent condition. The results of the experiment and the simulation are compared to validate the proposed model.

  • investigative article

    Determination of friction in metal cutting with tool wear and flank effects

    Wear, Vol. 317, Numbers 1–2, 2014, pp. 8-16

    (Video) GTC2018_Session2-Anderson

    This article examines the friction of bevel cutting in bevel Si turning.3norte4Ceramic tools with a large negative rake angle. The flank friction in particular is included in the tribological equilibrium. The values ​​of the force components recorded during the tool wear tests at different cutting speeds served as input data. The usual force components were transformed into the coordinate system of the tool used in order to be able to calculate the normal and frictional forces acting on the rake and flank surfaces and finally the corresponding friction coefficients. It was found that both friction coefficients change significantly with progressive tool wear and deviate from those determined for the orthogonal friction model. The new friction pattern was tested for machining ductile iron (SCI) with coated nitride ceramic inserts and further validated by tribo testing using cylinder-on-disk methods.

  • investigative article

    Modeling and analysis of a novel approach to machining and structuring flat surfaces through the milling process

    International Magazine of Machine Tools and Manufacturing, Band 105, 2016, S. 32-44

    In this article, a new and innovative method for regular structuring and special modeling of the workpiece surface using face milling is presented. The patterns were created on the surface by specific positioning of the workpiece and tool, milling passes in different directions, and the specific angular position of the spindle on a typical vertical milling machine. First, the model for the geometry of the cutting tool was developed and then a new simulation model for the surface pattern was created through the face milling process. Mathematical models are presented to describe the geometry and position of the cutting tool (including orientation and position) in space. Calculation and simulation programs (MATLAB and CAD programming software) are developed to verify this method. This study provides a basic understanding of the pattern milling process. Based on this, the influence of various milling process parameters on the pattern geometry (including the lead-in angle and radius) is analyzed. The simulation results could be used to optimize the traditional milling and pattern milling processes, as well as to improve the surface quality of the workpiece or to predict the surface pattern based on given face milling parameters.

  • investigative article

    Optimization of process parameters during temperature rise during CNC milling of Al 7068 using hybrid techniques

    Materials Today: Proceedings, Band 5, Nummer 2, Teil 2, 2018, S. 7037-7046

    Temperature measurement and estimation of heat distribution in metal cutting is important as it controls the contribution to tool deflection, tool life, cutting force and vibration, and the quality of the machined part. In this paper, a statistical model was developed to estimate the temperature rise using design parameters such as helix angle, radial inclination angle of the cutting tool, and machining parameters such as cutting speed, cutting speed, etc., feed and axial depth of cut in dry conditions. Reaction surface methodology and experimental design were used to conduct the experiments. The workpiece material was 7068 Al aluminum and the tool was a high speed steel end mill with a different tool geometry. The temperature rise was evaluated with a pyrometer. The second-order mathematical model related to machining parameters was developed to estimate temperature rise. The competence of the model was calculated using ANOVA. The direct and interacting effect of the process parameter on the temperature rise was analysed, which helped to select the process parameter to keep the temperature rise to a minimum, indicating the immobility of the final milling process. The prediction models in this study are believed to produce temperature rise values ​​that are close to the experimentally recorded readings with a 95% confidence interval. A Matlab genetic algorithm solver was used to perform the optimization.

    (Video) IAAC Lecture Series 2013 - George Jeronimidis
  • investigative article

    Strategy to optimize energy consumption in D2 steel ball micro milling by TLBO together with 3D FEM simulation

    Measure, Band 132, 2019, S. 68-78

    The current challenge in the manufacturing industry is to improve the efficiency of production activities while reducing wasteful energy consumption. Previous research has focused on optimizing multiple responses of process parameters to improve process performance. The present study proposed an optimization-based strategy to reduce energy consumption in end milling with D2 steel microspheres. Since power consumption is directly proportional to cutting forces, process parameters such as cutting speed, feed rate and depth of cut were optimized to reduce cutting forces using the Gauge-Based Optimization Technique (TLBO) along with 3D Finite Element Method (FEM) simulation. During the optimization, limit values ​​of 60 µm (ISO 10816) and 2 µm (ISO 1302) were assumed for the vibration amplitude of the milling cutter and the surface roughness. The three best combinations of cutting speed, feed and depth of cut for minimum cutting force were determined. Among other things, the combination of a cutting speed of 15 m/min, a feed of 112.5 µm/tooth and a cutting depth of 85.25 µm has a low power consumption of 67 W with a tool vibration of 36.5 µm. However, the remaining two combinations were also considered to be the next best optimal cutting conditions. For the three best solutions, a numerical simulation was carried out and the cutting forces and the amplitude of the vibration of the milling cutter were predicted. There was good agreement between the simulation results and the experimental results, confirming the acceptability of the simulation. It was also found that the three best candidate solutions had the same cutting speed of 15 m/min (minimum cutting speed). Therefore, it was found that the induced stresses in the workpiece have low values ​​around 350 MPa.

  • investigative article

    Modeling of chip geometry in spherical milling of superalloys using the Deformed Chip Deformation (SDC) approach

    International Magazine of Machine Tools and Manufacturing, Bände 130–131, 2018, S. 49-64

    Since it is known that chip geometry helps to predict machining forces, energy and thus the quality of the machined surface, several models have been developed in the past to predict deformed and undeformed chip geometries in spherical milling. It can be observed that most models use the volume constancy (VC) between the undeformed and deformed chip geometry to evaluate the deformed chip thickness. This work presents a new approach to assess deformed chip geometry, which includes considering deformations in deformed chips (SDC). In the strains developed using the deformed chip (SDC) approach, bending, compression/shear, and thermal strains were modeled using a simplified shape of a conical overhang of the undeformed chip. When developing the model, the interactions between the cutting edge and machining on horizontal work surfaces and those inclined at different angles were taken into account. As the slope of the workpiece increases from 0° (horizontal) to 60°°, deformed chip thickness increases by 63% due to greater effective feed per tooth. However, it was found that the instantaneous shear angle is constant at 50°°along the cut for a typical parametric machining combination. A comparison of the SDC and VC approaches shows that the magnitudes of deformed chip thickness, rake angle and resulting cutting forces obtained from SDC models are the closest (within 90%) in agreement with experimental data. It is expected that such models, when integrated with shear force models, would help predict shear forces more accurately.

Copyright © 1982 Published by Elsevier B.V.


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