scholarly journals NUMERICAL MODEL OF A LOCAL CONTACT OF A POLYMER NANOCOMPOSITE AND ITS EXPERIMENTAL VALIDATION

2021 ◽  
Vol 19 (1) ◽  
pp. 079
Author(s):  
Andrey I. Dmitriev
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Friction Coefficient ◽  
Experimental Validation ◽  
Polymer Nanocomposite ◽  
Characteristic Size ◽  
Dry Sliding ◽  
Sliding Velocity ◽  
Low Friction ◽  
Local Contact

In the paper a model of a local contact of a polymer-based nanocomposite was developed within the method of a movable cellular automaton. The features of mechanical behavior of nanocomposite at the mesoscale level under dry sliding were studied with explicit account for the microprofile of the counterbody surface and the characteristic sizes of nanofiller. Factors that contribute to the conditions for the formation of a stable tribofilm of silica nanoparticles are analyzed. Two other parameters like sample geometry and the value of relative sliding velocity are also examined. It is shown that the thickness of tribofilm depends on stress conditions at the contact, and the friction coefficient decreases with increasing sliding velocity similar to one observed experimentally. To ensure the low friction properties of polymer nanocomposite, particles whose sizes are comparable with the characteristic size of the substrate microprofile are preferred. Results of numerical simulation are in good correlation with available experimental data.

Global Analysis of Polymer Pads in a Bearing Element for a Large-Span Movable Sluice

2013 ◽  
Vol 834-836 ◽  
pp. 772-775
Author(s):  
Pin Gou ◽  
Xu Peng ◽  
Lin Ren
Keyword(s):  
Friction Coefficient ◽  
Contact Stress ◽  
Load Transfer ◽  
Global Analysis ◽  
Dry Sliding ◽  
Low Friction ◽  
Reinforced Polymer ◽  
Contact Surfaces ◽  
Polymer Bearing ◽  
Lubrication Conditions

The contact surface of a hinge suffers huge pressure in particularly bad lubrication conditions. Reinforced polymer bearing pads offers low friction under dry sliding conditions. Load transfer between contact surfaces was studied, showing that the pressure and positions are related to the power output of the loco. The friction coefficient of concave bearings with polymer pads was low, and would not totally failed in a high contact stress. Performances of polymer pads on loads were simulated, and provided a global analysis for the design of the pads.

scholarly journals Modeling and Analysis for Wear Performance in Dry Sliding of Epoxy/Glass/PTW Composites Using Full Factorial Techniques

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
M. Sudheer ◽  
Ravikantha Prabhu ◽  
K. Raju ◽  
Thirumaleshwara Bhat
Keyword(s):  
Friction Coefficient ◽  
Wear Rate ◽  
Hybrid Composites ◽  
Normal Load ◽  
Glass Fibers ◽  
Dry Sliding Wear ◽  
Dry Sliding ◽  
Sliding Velocity ◽  
Wear Performance ◽  
Full Factorial

The dry sliding friction and wear behavior of epoxy hybrid composites reinforced with glass fibers and a varying amount of potassium titanate whiskers (PTWs) fabricated by vacuum hand layup method were studied. The influence of normal load, sliding velocity, and whisker content on both friction coefficient and specific wear rate was investigated on a pin-on-disc machine. The tests were conducted at ambient conditions based on the 3 × 3 (3 factors at 3 levels) full factorial design. Analysis of variance (ANOVA) was performed to obtain the contribution of control parameters on friction coefficient and wear rate. The density and hardness of the composites were found to be enhanced with the PTW loading. The friction coefficient and wear resistance of the hybrid composites were found to be improved with the whisker content and were also greatly influenced by normal load and sliding velocity. A correlation between dry sliding wear behaviors of composites with wear parameters was obtained by multiple regressions. The worn out surface of selected samples was observed under scanning electron microscope (SEM) to identify wear mechanisms. This study revealed that the addition of the ceramic microfillers such as PTW improves the wear performance of the epoxy/glass polymer composites significantly.

Impact of Mistuned Underplatform Dampers On the Nonlinear Vibration of Bladed Disks

2021 ◽  
Author(s):  
Samuel Quaegebeur ◽  
Benjamin Chouvion ◽  
Fabrice Thouverez
Keyword(s):  
Numerical Simulation ◽  
Friction Coefficient ◽  
Experimental Validation ◽  
Cyclic Structure ◽  
Practical Solution ◽  
Vibratory Response ◽  
Symmetric Structure ◽  
Cyclic Symmetric ◽  
Underplatform Damper ◽  
Symmetric Systems

Abstract Before the final experimental validation and certification of a turboengine, designers perform a numerical simulation of its vibratory properties, among other things, in order to estimate its lifespan and adjust the design in an optimization process. One possible practical solution to decrease the vibratory response is to add underplatform dampers to the system. These components dissipate energy by friction and are widely employed in turbomachinery. However, a specific underplatform damper is usually efficient only for a specific mode. The purpose of this work is to investigate the possibility of adding different kinds of underplatform dampers to the cyclic structure in order to decrease the vibratory energy over a larger panel of modes. Different methods exist to determine the vibrations of nonlinear cyclic symmetric systems, but creating a robust methodology to account for the additional effect of mistuning remains a big challenge in the community. In this paper, the structure is mistuned through the friction coefficient of the dampers and not by altering its geometry, as is usually done in the literature. First, assuming a cyclic symmetric structure, the performance of the dampers is assessed for specific modes. Then, employing a method recently developed, the efficiency of an intentional mistuning pattern of underplatform dampers is studied and an optimal pattern proposed.

On the Modeling of Quasi-Steady and Unsteady Dynamic Friction in Sliding Lubricated Line Contact

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
H. Sojoudi ◽  
M. M. Khonsari
Keyword(s):  
Experimental Data ◽  
Friction Coefficient ◽  
Reynolds Equation ◽  
Friction Model ◽  
Sliding Contact ◽  
Dynamic Friction ◽  
Line Contact ◽  
Sliding Velocity ◽  
Friction Behavior ◽  
Lubricated Sliding

A simple but realistic dynamic friction model for the lubricated sliding contact is developed based on decoupling the steady and unsteady terms in Reynolds equation. The model realistically captures the physics of friction behavior both when speed is increased unidirectionally or when operating under oscillating condition. The model can simulate the transition from boundary to mixed to full film regimes as the speed is increased. Two different classes of simulations are performed to show the utility of the model: the so-called quasisteady, where the sliding velocity is varied very slowly, and the oscillating sliding velocity, where the friction coefficient exhibits a hysteresis type behavior. Both categories of simulation are verified by comparing the results with published experimental data.

Model Validation of a Magnetic Ball Levitation System

2008 ◽  
Author(s):  
Aravind Hanasoge ◽  
Ashraf Omran ◽  
Thomas Alberts
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Electromagnetic Force ◽  
Pid Controller ◽  
Experimental Validation ◽  
Gain Scheduling ◽  
Modeling Simulation ◽  
Levitation System ◽  
Simulation Results ◽  
Linearized Model

In this paper, modeling, simulation and experimental validation of a magnetic ball suspension system are presented. Non-linear empirical expressions for inductance and electromagnetic force are determined using experimental data. A simple PID controller and a Gain scheduling PID controller are designed based on the linearized model. The controllers are used in real time levitation and tracking of a steel ball. Numerical simulation is carried out using Simulink. The derived model is verified by comparing the simulation results with experimental results.

scholarly journals Numerical simulation of shallow square boxes with flanges based on Dynaform

2018 ◽  
Vol 232 ◽  
pp. 03021
Author(s):  
cunping Liu ◽  
yong Liu ◽  
sheng Guo
Keyword(s):  
Numerical Simulation ◽  
Finite Element Method ◽  
Finite Element ◽  
Friction Coefficient ◽  
Important Process ◽  
Blank Holder Force ◽  
Low Friction ◽  
Blank Holder ◽  
Aa5182 Alloy ◽  
Thinning Rate

In this work, Numerical simulations based on finite element method have been carried out to study the effect of important process parameters on formability of AA5182 alloy sheets. The blank holder force between 0.5KN and 3KN and friction coefficient(μ) between 0.05 and 0.20, which resulted in successful drawing, was evaluated. Maximum percentage thinning has always been obtained at the conjunction of corner and bottom. The maximum thinning rate was nearly 20% for a maximum holder force of 3KN. Friction coefficient simulations are shown that as friction coefficient increasing, the thinning rate becomes larger and low friction coefficient is beneficial to the sheet forming.

Impact of Mistuned Underplatform Dampers on the Nonlinear Vibration of Bladed Disks

2021 ◽  
Author(s):  
Samuel Quaegebeur ◽  
Benjamin Chouvion ◽  
Fabrice Thouverez
Keyword(s):  
Numerical Simulation ◽  
Friction Coefficient ◽  
Experimental Validation ◽  
Cyclic Structure ◽  
Practical Solution ◽  
Vibratory Response ◽  
Symmetric Structure ◽  
Cyclic Symmetric ◽  
Underplatform Damper ◽  
Symmetric Systems

Abstract Before the final experimental validation and certification of a turboengine, designers perform a numerical simulation of its vibratory properties, among other things, in order to estimate its lifespan and adjust the design in an optimization process. One possible practical solution to decrease the vibratory response is to add underplatform dampers to the system. These components dissipate energy by friction and are widely employed in turbomachinery. However, a specific underplatform damper is usually efficient only for a specific mode. The purpose of this work is to investigate the possibility of adding different kinds of underplatform dampers to the cyclic structure in order to decrease the vibratory energy over a larger panel of modes. Different methods exist to determine the vibrations of nonlinear cyclic symmetric systems, but creating a robust methodology to account for the additional effect of mistuning remains a big challenge in the community. In this paper, the structure is mistuned through the friction coefficient of the dampers and not by altering its geometry, as is usually done in the literature. First, assuming a cyclic symmetric structure, the performance of the dampers is assessed for specific modes. Then, employing a method recently developed, the efficiency of an intentional mistuning pattern of underplatform dampers is studied and an optimal pattern proposed.

Evolutional Friction Law in the Numerical Simulation of the Deep Drawing of a Rail

2006 ◽  
Vol 514-516 ◽  
pp. 1443-1447
Author(s):  
Marta C. Oliveira ◽  
J. Luís Alves ◽  
Luís Filipe Menezes
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Friction Coefficient ◽  
Deep Drawing ◽  
Kinematic Hardening ◽  
Friction Forces ◽  
Friction Law ◽  
Entire Process ◽  
Constant Friction ◽  
Blank Sheet

One of the most relevant technological parameters for the accurate numerical simulation of the deep drawing process is friction, since the contact between the blank sheet and tools develops friction forces that act as supplementary boundary conditions that determine the final part shape. Most applications reported in literature are still restricted to Coulomb’s law with a constant friction coefficient over the entire process. Although it is consensual that state conditions of contact surfaces and consequently the friction behaviour are influenced by a large number of parameters, there is no agreement about a wide-ranging law to accurately describe the friction evolution. One possibility is to use phenomenological laws that accurately fit experimental data. A Voce type law is used in this work to describe the evolution of the friction coefficient over the entire process as function of the contact pressure. This type of law guarantees a good correlation with experimental data and also numerical stability. The Voce type law was implemented in the static implicit code DD3IMP. The analysis of the relevance of considering the evolutional friction law in the numerical simulation is performed for a U-rail. This shape was selected for this study due to the simple deformation mechanisms that are involved, but also because it is a rail specially conceived to emphasize 2-D springback defects. The blank sheet material selected is a 6016-T4 aluminium alloy. The plastic behaviour is modelled using the 1948 Hill’s criterion with isotropic and kinematic hardening. The numerical results obtained considering the evolutional friction law are compared with two other results obtained with: (i) a constant friction value of 0.10, normally used for this material in industrial practice and (ii) three constant friction coefficients for each contact zone (flat, die radius and punch radius).

Numerical simulation and experimental validation of angular distortion and residual stresses in a T-joint

2015 ◽  
Vol 57 (7-8) ◽  
pp. 628-634
Author(s):  
Jing Chen ◽  
Liying Wang ◽  
Zhendong Shi ◽  
Zhen Dai ◽  
Meiqing Guo
Keyword(s):  
Numerical Simulation ◽  
Residual Stresses ◽  
Experimental Validation ◽  
Angular Distortion
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