Study of Pressure Distribution in Compliant Coated Abrasive Tools for Robotic Polishing

2012 ◽  
Author(s):  
Muhammed Umer ◽  
Kushendarsyah Saptaji ◽  
Sathyan Subbiah
Keyword(s):  
Finite Element ◽  
Pressure Distribution ◽  
Contact Area ◽  
Force Control ◽  
Applied Load ◽  
Element Model ◽  
Curved Surfaces ◽  
Abrasive Tool ◽  
Abrasive Grains ◽  
Abrasive Tools

Robotic polishing applications involve the use of coated abrasive tools along with a compliant backing pad. The compliance helps in conforming to curved surfaces and also in blending with unpolished areas. This compliance and its effect are currently controlled only by empirical choice of various backing pad designs and materials. A better understanding of this important characteristic of these tools will lead to better process control. One of the effects of the compliance or stiffness of the backing pad under a certain applied load (robotic force control) is on the contact area and pressure distribution applied on the abrasive grains in that area. This pressure distribution in turn dictates how material is removed in the area of contact. Here, we report preliminary results of the pressure distribution exerted by an abrasive tool mounted on a robot using pressure film sensors and compare results with a simple finite element model.

A Fundamental Study of the Interaction of Residual Stress and Applied Loading on Fracture

2010 ◽  
Author(s):  
C. J. Aird ◽  
M. J. Pavier ◽  
D. J. Smith
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Stress Field ◽  
Crack Closure ◽  
Applied Load ◽  
Element Model ◽  
Residual Stress Field ◽  
Fundamental Study ◽  
Analytical Expression ◽  
Applied Loading

This paper presents the results of a fundamental finite-element based study of the crack-closure effects associated with combined residual and applied loading. First, an analytical expression for a representative two-dimensional residual stress field is derived. This residual stress field contains a central compressive region surrounded by an equilibrating tensile region. The analytical expression allows the size and shape of the field to be varied along with the magnitude of the residual stress. The residual stress field is then used as a prescribed initial stress field in a finite element model, in addition to a far field applied load. By introducing cracks of increasing length into these models, charts of stress-intensity-factor versus crack length are produced for different relative magnitudes of residual stress and applied load and for different sizes and shape of the residual stress field. These charts provide insight into the way in which crack-tip conditions evolve with crack growth under conditions of combined residual and applied loading and also enable conditions of crack closure and partial closure to be identified.

Contact Stress and Linearized Modal Predictions of As-Built Preloaded Assembly

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Adam R. Brink ◽  
Robert J. Kuether ◽  
Matthew D. Fronk ◽  
Bryan L. Witt ◽  
Brendan L. Nation
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Contact Area ◽  
Element Model ◽  
High Fidelity ◽  
Vibration Modes ◽  
Low Level ◽  
Pressure Sensitive ◽  
Sensitive Film ◽  
Pressure Sensitive Film

Abstract The member stiffness and pressure distribution in a bolted joint is significantly influenced by the contact area of the mechanical interface under a prescribed preload force. This research explores the influence of as-built surface profiles for nominally flat interfaces of a C-Beam assembly with two well-defined contact regions. A high-fidelity finite element model is created such that the model uncertainty is minimized by updating and calibrating the piece parts prior to the preload assembly procedure. The model is then assembled and preloaded to evaluate the contact stresses and contact area for both nominally flat and perturbed non-flat surfaces based on three-dimensional surface topography measurements. The predicted pressures are validated with digitized pressure-sensitive film measurements. The high-fidelity modeling reveals how the compliance and thickness of the pressure-sensitive film alter the measured pressures, leading to incorrect evaluations of the stresses and contact area in the joint. The resulting low-level dynamic behavior of the preloaded assembly is shown to be sensitive to the true contact area by linearizing the nonlinear finite element model about the preloaded equilibrium and performing a computational modal analysis. The resonant frequencies are validated with experimental measurements to demonstrate the effect of the contact area on the modal characteristics of the bolted assembly. Vibration modes and loading patterns exhibit varying levels of sensitivity to the contact area in the joint, leading to an improved physical understanding of the influence of contact mechanics on the low-level linear vibration modes of jointed assemblies.

Elastic-Plastic Contact Analysis of a Sphere and a Rigid Flat

2002 ◽  
Vol 69 (5) ◽  
pp. 657-662 ◽  
Author(s):  
L. Kogut ◽  
I. Etsion
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Contact Pressure ◽  
Contact Zone ◽  
Contact Area ◽  
Large Range ◽  
Element Model ◽  
Contact Interface ◽  
Frictionless Contact ◽  
Elastic Plastic

An elastic-plastic finite element model for the frictionless contact of a deformable sphere pressed by a rigid flat is presented. The evolution of the elastic-plastic contact with increasing interference is analyzed revealing three distinct stages that range from fully elastic through elastic-plastic to fully plastic contact interface. The model provides dimensionless expressions for the contact load, contact area, and mean contact pressure, covering a large range of interference values from yielding inception to fully plastic regime of the spherical contact zone. Comparison with previous elastic-plastic models that were based on some arbitrary assumptions is made showing large differences.

scholarly journals A Finite Element-Based Elastic-Plastic Model for the Contact of Rough Surfaces

2011 ◽  
Vol 2011 ◽  
pp. 1-11 ◽  
Author(s):  
Ali Sepehri ◽  
Kambiz Farhang
Keyword(s):  
Finite Element ◽  
Contact Force ◽  
Contact Area ◽  
Rough Surfaces ◽  
Constitutive Relations ◽  
Element Model ◽  
Tangential Component ◽  
Asperity Contact ◽  
Elastic Plastic ◽  
Force Components

Three-dimensional elastic-plastic contact of two nominally flat rough surfaces is considered. Equations governing the shoulder-shoulder contact of asperities are derived based on the asperity constitutive relations from a finite element model of the elastic-plastic interaction proposed by Kogut and Etsion (2002), in which asperity scale constitutive relations are derived using piecewise approximate functions. An analytical fusion technique is developed to combine the piecewise asperity level constitutive relations. Shoulder-shoulder asperity contact yields a slanted contact force consisting of two components, one in the normal direction and a half-plane tangential component. Statistical summation of the asperity level contact force components and asperity level contact area results in the total contact force and total contact area formulae between two rough surfaces. Approximate equations are developed in closed form for contact force components and contact area.

Finite Element Analysis on Real Contact Area Based on Fractal Characterization

2013 ◽  
Vol 579-580 ◽  
pp. 517-522 ◽  
Author(s):  
Jia Chun Wang ◽  
Bo Qiang Xing ◽  
Teng Zhao
Keyword(s):  
Finite Element ◽  
Rough Surface ◽  
Contact Area ◽  
Smooth Surface ◽  
Thermal Conductance ◽  
Element Model ◽  
Real Contact Area ◽  
Process Data ◽  
Element Analysis ◽  
Real Contact

No surface in engineering is absolutely smooth. It is important to analyze and calculate the real contact area for a better understanding of friction, wear, lubrication and thermal conductance. To obtain the accurate real contact area between rough surface and smooth surface, a rough-non-rigid-smooth surface contact finite element model is proposed in which the rough surface is characterized by fracture theory. In finite element modeling and analyzing process, MATLABEXCEL and AutoCAD are used to process data, and the smooth surface is considered to be non-rigid body. Compared with the traditional modeling, this method can obtain data quickly and is closer to the actual situation.

scholarly journals MODERN APPROACHES TO SOLVING THE CONTACT PROBLEM OF PRESSING A DOUBLESTAMP STAMP INTO AN ELASTIC HALF-SPACE

2021 ◽  
pp. 74-79
Author(s):  
Tetyana Zaytseva ◽  
Ivan Shmelov
Keyword(s):  
Finite Element ◽  
Half Space ◽  
Contact Area ◽  
Software Package ◽  
Complex Shape ◽  
Element Model ◽  
Circular Ring ◽  
Elastic Half Space ◽  
Ansys Software ◽  
Java Language

The work is devoted to solving indentation problems into an elastic half-space of a cylindrical punch with a flat base by the vertical force. The force is aimed through the center of the base. The cross-section of the stamp is a doubly connected area bounded by two concentric lines. A concise review of methods for solving problems of analyzing the contact interaction of cylindrical dies with an elastic half-space is given. The solution of the problem in the form of decomposition by a small parameter is used when the equation of the edge curves depends on the same small parameter. To achieve it, in each approximation, the problem of indentation of a stamp with a doubly connected contact area in the form of a non-circular ring is reduced to a similar problem of indentation of a stamp with a contact area in the form of a circular ring. The software in the Java language has been developed for processing the analytical solution according to the obtained calculation formulas. With the help of the ANSYS software package, a finite element model of the contact interaction of an absolutely rigid stamp with an elastic half-space has been created. Numerical modeling was carried out using a licensed version of the program, free of charge. Several problems have been solved for square rings of different widths. The distribution of pressure under the stamp over different sections and the deepening of the stamp have been obtained. The pressure distribution graphs are plotted. When considering several test problems to assess the adequacy of the finite element model, the numerical results are compared with the results obtained analytically. The resulting model can analyze and predict loads, wear, and fracture of the contact area. The research prospects can include the solution of several problems of analysis of the stress-strain state of the interaction of dies of a complex shape with an elastic half-space, as well as groups of stamps of a complex shape, and the analysis of behavior models depending on the properties and characteristics of an elastic half-space. Keywords: contact problem, stamp, stress-strain state, modeling, JAVA language, finite element analysis, ANSYS software package.

Overview of methods to identify the static normal wheel-rail contact

2021 ◽  
pp. 095440972110424
Author(s):  
Ina Stratmann ◽  
Jannik Goersch ◽  
Christian Schindler
Keyword(s):  
Finite Element ◽  
Contact Area ◽  
High Pressures ◽  
Contact Point ◽  
Element Model ◽  
Carbon Paper ◽  
The Finite Element Method ◽  
Element Analysis ◽  
Detailed Assessment ◽  
Shape And Size

Determining the shape and size of a wheel-rail contact area is required to calculate fatigue and wear of wheel and rail. Fatigue and wear are influenced by high pressures of up to 1000 MPa that act on the small contact area of approximately 1 cm². One problem in identifying the contact patch is the inaccessibility of the contact point. Therefore, numerical and experimental methods have been applied to identify the shape and size of the contact area in the static wheel-rail contact. Here, we summarize and compare methods to identify the static wheel-rail contact area, in particular the Hertzian calculation, the use of carbon paper, the use of pressure measurement film, the finite element method, the use of ultrasonic testing, and a semi-Hertzian method called STRIPES. Our review revealed that several methods exist to determine the static wheel-rail contact, which were introduced as well as results of some research projects. However, the partly incomplete description of methods studied impeded a detailed assessment of the results. Furthermore, due to the non-comparable parameters applied in the different studies, it was impossible to contrast the results and methods presented in the different publications. Hence, it is recommended that future results in the field of static wheel-rail contact should be directly contrasted with a detailed finite element model. This proceeding will allow to directly compare different methods on the bases of finite element analysis and thus the identification of a method for each situation.

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