Curve Fitting for Mechanical and Tribological Problems

2021 ◽  
pp. 249-276
Keyword(s):  
Friction Coefficient ◽  
Yield Strength ◽  
Curve Fitting ◽  
Fuel Efficiency ◽  
Diagnostic Parameter ◽  
Mathematical Expressions ◽  
Grain Diameter

This chapter devoted to matching the data with mathematical expressions. Here the functions using fitting by polynomial and non-polynomial expressions is represented by examples from the mechanics and tribology (M&T) fields. The Basic Fitting tool and examples of its use are described. Single and multivariate fitting through optimization are discussed. Application examples are demonstrate the curve fitting for the following data: fuel efficiency-velocity, yield strength-grain diameter, friction coefficient-time, and machine diagnostic parameter.

scholarly journals Effect of Low Hydroxyapatite Loading Fraction on the Mechanical and Tribological Characteristics of Poly(Methyl Methacrylate) Nanocomposites for Dentures

Polymers ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 857
Author(s):  
Ahmed Fouly ◽  
Ahmed Mohamed Mahmoud Ibrahim ◽  
El-Sayed M. Sherif ◽  
Ahmed M.R. FathEl-Bab ◽  
A.H. Badran
Keyword(s):  
Friction Coefficient ◽  
Yield Strength ◽  
Methyl Methacrylate ◽  
Weight Fraction ◽  
Tribological Characteristics ◽  
Compressive Yield Strength ◽  
Wear Loss ◽  
Mechanical Mixing ◽  
Poly Methyl Methacrylate ◽  
Mechanical And Tribological Characteristics

Denture base materials need appropriate mechanical and tribological characteristics to endure different stresses inside the mouth. This study investigates the properties of poly(methyl methacrylate) (PMMA) reinforced with different low loading fractions (0, 0.2, 0.4, 0.6, and 0.8 wt.%) of hydroxyapatite (HA) nanoparticles. HA nanoparticles with different loading fractions are homogenously dispersed in the PMMA matrix through mechanical mixing. The resulting density, Compressive Young’s modulus, compressive yield strength, ductility, fracture toughness, and hardness were evaluated experimentally; the friction coefficient and wear were estimated by rubbing the PMMA/HA nanocomposites against stainless steel and PMMA counterparts. A finite element model was built to determine the wear layer thickness and the stress distribution along the nanocomposite surfaces during the friction process. In addition, the wear mechanisms were elucidated via scanning electron microscopy. The results indicate that increasing the concentration of HA nanoparticles increases the stiffness, compressive yield strength, toughness, ductility, and hardness of the PMMA nanocomposite. Moreover, tribological tests show that increasing the nanoparticle weight fraction considerably decreases the friction coefficient and wear loss.

scholarly journals Microstructure, and Mechanical and Wear Properties of Grp/AZ91 Magnesium Matrix Composites

Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1190 ◽  
Author(s):  
Chang-rui Wang ◽  
Kun-kun Deng ◽  
Yan Bai
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Tensile Strength ◽  
Friction Coefficient ◽  
Wear Rate ◽  
Yield Strength ◽  
Wear Mechanism ◽  
Thermal Deformation ◽  
Volume Fraction ◽  
Az91 Alloy

Based on semi-solid mixing technology, two kinds of as-cast Grp (Graphite particles)/AZ91 composites with different Grp volume fractions (5 vol %, 10 vol %) were prepared; these are called 5 vol % Grp/AZ91 composites and 10 vol % Grp/AZ91 composites, respectively. In order to eliminate casting defects, refine grains, and improve mechanical properties, thermal deformation analysis of these composites was conducted. The effect of the addition of Grp and thermal deformation on the microstructure, mechanical properties, and wear resistance of AZ91 composite was explored. The results showed that after 5 vol % Grp was added into the as-cast AZ91 alloy, Mg17Al12 phases were no longer precipitated reticularly along the grain boundary, and Al4C3 phases were formed inside the composite. With the increase in the volume fraction of Grp, the grains of the AZ91 composites were steadily refined. With the increase of forging pass, the grain size of 5% Grp/AZ91 composites decreased first, and then increased. Additionally, the Grp size decreased gradually. There was little change in the yield strength, and the tensile strength and elongation were improved to a certain extent. After forging and extrusion of 5% Grp/AZ91 composites once, the grain size and Grp size were further reduced, and the yield strength, tensile strength, and elongation were increased by 23%, 30%, and 65%, respectively, compared with the composite after forging. With the increase of the number of forging passes before extrusion, the grain size decreased little by little, while the Grp size remained unchanged. The average yield strength, tensile strength, and elongation of the composites after forging and extrusion six times were increased by 3%, 3%, and 23%, respectively, compared with the composite after forging and extrusion once. The wear rate and friction coefficient of the 5% Grp/AZ91 composites decreased after forging once, and the wear mechanism was mainly due to ploughing wear. By comparison, the wear rate and friction coefficient of the 5% Grp/AZ91 composites increased in the extrusion state, and the main wear mechanism was from wedge formation and micro-cutting wear.

scholarly journals Study of a-C:H thin films deposited by Plasma Immersion Ion Implantation for mechanical and tribological applications

2019 ◽  
Vol 2 (3) ◽  
pp. 24-32
Author(s):  
Péricles Lopes SantAna ◽  
Santos R. J. ◽  
Bortoleto J. R. R. ◽  
Cruz N. C. ◽  
Rangel E. C. ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Raman Spectroscopy ◽  
Friction Coefficient ◽  
Co2 Emission ◽  
Fuel Efficiency ◽  
Excitation Power ◽  
Steel Alloy ◽  
Raman Analysis ◽  
Nanoindentation Hardness ◽  
Plasma Immersion Ion Implantation

The tribological and mechanical properties of DLC films deposited on the surface of 16MnCr5 steel alloy were investigated. The major concerning of using DLC layers on engine parts are: (i) to reduce friction; (ii) to increase fuel efficiency and to reduce CO2 emission; (iii) to increase hardness of alloy steel. After polished and ultrasonicated, 16MnCr5 substrates were submitted to PIIID procedures in radiofrequency plasmas (13.56 MHz) generated from atmospheres of methane and argon. Excitation power and total gas pressure were kept constant. It was investigated the effect of methane proportion on the microstructure and mechanical properties of the films using the follow techniques: Raman Spectroscopy (for Hydrogen content and microstructure analysis), Ultra Micro-Tribometer (for friction coefficient) and Nanoindentation (hardness evaluation). Raman analysis confirmed DLC character of the films produced, and the proportion of 80% methane and 20% argon resulted to the best performance of mechanical properties of the films owing to the increase of hardness in until ten times, and reducing the friction coefficient to about 0.2. In addition, thickness for these films varied from 165 nm to 206 nm.

Torque capacity of the multilayer interference fit based on a friction coefficient prediction model

2021 ◽  
pp. 135065012110397
Author(s):  
Ke Ning ◽  
Jianmei Wang ◽  
Dan Xiang ◽  
Dingbang Hou
Keyword(s):  
Finite Element ◽  
Theoretical Model ◽  
Friction Coefficient ◽  
Prediction Model ◽  
Three Dimensional ◽  
Element Model ◽  
Maximum Relative Error ◽  
Interference Fit ◽  
Mathematical Expressions ◽  
Torque Capacity

This paper proposes the theoretical model of a multilayer interference fit and gives out the relational expression between radial interference and friction coefficient. Taking the typical wind turbine's shrink disk of a three-layer interference fit structure as an example, special experimental equipment is developed to test the torque capacity. Based on experimental results and the theoretical model, the mathematical expressions of radial interference and assembly stroke for friction coefficient are obtained by polynomial fitting, and the prediction model of friction coefficient is established. The three-dimensional finite element model of a shrink disk is constructed by applying the friction coefficient prediction model. With the mathematical expressions of radial interference and assembly stroke for the torque capacity, the rules of main dimension parameters and torque capacity are analyzed. The maximum relative error between experiment and simulation is 8.2%, which shows the feasibility of finite element simulation. The results of our study have certain guidance for the prediction of friction coefficient and the manufacture of the multilayer interference fit.

scholarly journals A Unified Model for the Prediction of Yield Strength in Particulate-Reinforced Metal Matrix Nanocomposites

2021 ◽  
Author(s):  
F. A. Mirza ◽  
Daolun Chen
Keyword(s):  
Experimental Data ◽  
Yield Strength ◽  
Metal Matrix ◽  
Fuel Efficiency ◽  
Unified Model ◽  
Transportation Industry ◽  
Metal Matrix Nanocomposites ◽  
Structural Applications ◽  
The Matrix ◽  
Matrix Nanocomposites

Lightweighting in the transportation industry is today recognized as one of the most important strategies to improve fuel efficiency and reduce anthropogenic climate-changing, environment-damaging, and human death-causing emissions. However, the structural applications of lightweight alloys are often limited by some inherent deficiencies such as low stiffness, high wear rate and inferior strength. These properties could be effectively enhanced by the addition of stronger and stiffer reinforcements, especially nano-sized particles, into metal matrix to form composites. In most cases three common strengthening mechanisms (load-bearing effect, mismatch of coefficients of thermal expansion, and Orowan strengthening) have been considered to predict the yield strength of metal matrix nanocomposites (MMNCs). This study was aimed at developing a unified model by taking into account the matrix grain size and porosity (which is unavoidable in the materials processing such as casting and powder metallurgy) in the prediction of the yield strength of MMNCs. The Zener pinning effect of grain boundaries by the nano-sized particles has also been integrated. The model was validated using the experimental data of magnesium- and titanium-based nanocomposites containing different types of nano-sized particles (namely, Al2O3, Y2O3, and carbon nanotubes). The predicted results were observed to be in good agreement with the experimental data reported in the literature.

scholarly journals Hematite Suspension based Absorbent Pad Inclined Slider Influenced by Slip and Squeeze Velocity with Altering Film Ratio

2021 ◽  
Vol 71 (2) ◽  
pp. 185-191
Author(s):  
Paras Ram ◽  
Anil Kumar
Keyword(s):  
Friction Coefficient ◽  
Fluid Dynamic ◽  
Load Capacity ◽  
Maximum Load ◽  
Physical Parameters ◽  
Centre Of Pressure ◽  
Governing Equations ◽  
Material Parameters ◽  
Lifting Force ◽  
Mathematical Expressions

The effects of various entities like slip and squeeze velocities, inlet-outlet film ratio, and the material parameter have been fairly explored in a hematite suspension based absorbent (porous) pad inclined slider. Mathematical expressions for pressure, load capacity (lifting force), friction, friction coefficient, and position of centre of pressure (COP) in terms of the above physical parameters have been acquired. Jenkins model has been employed as a mathematical set of governing equations. It has been found that an increase in the squeeze velocity has enhanced the load capacity and diminished the friction coefficient whereas the escalating values of slip velocity and material properties have reversed the trends. Besides, the optimum value of the inlet-outlet film ratio for maximum load capacity has reduced with a rise in the squeeze velocity. Improvement in material parameters shifted the position of COP slightly towards the inlet while an enhancement in the squeeze velocity and film ratio shifted the same slightly towards the outlet. The results acquired in the present paper will be helpful in designing and modifying the various types of fluid dynamic slider bearings.

A Computational Chemistry Approach for Investigation of Low Friction Mechanisms Based on FEP Film with Functionalized SiO2 Nanoparticles

2015 ◽  
Vol 1119 ◽  
pp. 142-150
Author(s):  
Yusuke Morita ◽  
Marleen de Weser ◽  
Gerhard Schottner
Keyword(s):  
Friction Coefficient ◽  
Internal Combustion Engines ◽  
Fuel Efficiency ◽  
Friction Reduction ◽  
Dynamics Simulation ◽  
Chemical Calculation ◽  
Combustion Engines ◽  
Low Friction ◽  
Reduction Mechanisms ◽  
Friction Measurements

To improve the fuel efficiency of automobile internal combustion engines, we investigated the fundamental mechanism of friction reduction within engine moving parts. A new coating was designed by introducing SiO2nanoparticles in FEP film. The SiO2nanoparticles were functionalized with hydrophobic fluoroalkyl units on their surface to create additional low friction property. Universal Surface Tester friction measurements revealed a significant reduction of the friction coefficient with increasing number of hydrophobic fluoroalkyl units for SiO2surface functionalization. To clarify the friction reduction mechanisms by the functionalization of SiO2nanoparticles, a quantum chemical calculation was carried out. The result indicates that an attractive force occurs between nanoparticle Si atoms and polymer F atoms, while by adding fluoroalkyl units on the SiO2nanoparticle surface, this force changes to repulsive. By performing a molecular dynamics simulation of a shear model between FEP film and SiO2nanoparticles, we observed a decrease of friction force with increasing fluoroalkyl units which lead smooth rolling motion of nanoparticles, thus confirming the repulsive effect of nanoparticle functionalization. We conclude that fluoroalkyl units on the SiO2surface play an important role in creating a repulsive force between nanoparticle and FEP film which lead to low friction coefficient.

scholarly journals A Unified Model for the Prediction of Yield Strength in Particulate-Reinforced Metal Matrix Nanocomposites

2021 ◽  
Author(s):  
F. A. Mirza ◽  
Daolun Chen
Keyword(s):  
Experimental Data ◽  
Yield Strength ◽  
Metal Matrix ◽  
Fuel Efficiency ◽  
Unified Model ◽  
Transportation Industry ◽  
Metal Matrix Nanocomposites ◽  
Structural Applications ◽  
The Matrix ◽  
Matrix Nanocomposites

Lightweighting in the transportation industry is today recognized as one of the most important strategies to improve fuel efficiency and reduce anthropogenic climate-changing, environment-damaging, and human death-causing emissions. However, the structural applications of lightweight alloys are often limited by some inherent deficiencies such as low stiffness, high wear rate and inferior strength. These properties could be effectively enhanced by the addition of stronger and stiffer reinforcements, especially nano-sized particles, into metal matrix to form composites. In most cases three common strengthening mechanisms (load-bearing effect, mismatch of coefficients of thermal expansion, and Orowan strengthening) have been considered to predict the yield strength of metal matrix nanocomposites (MMNCs). This study was aimed at developing a unified model by taking into account the matrix grain size and porosity (which is unavoidable in the materials processing such as casting and powder metallurgy) in the prediction of the yield strength of MMNCs. The Zener pinning effect of grain boundaries by the nano-sized particles has also been integrated. The model was validated using the experimental data of magnesium- and titanium-based nanocomposites containing different types of nano-sized particles (namely, Al2O3, Y2O3, and carbon nanotubes). The predicted results were observed to be in good agreement with the experimental data reported in the literature.

scholarly journals Effect of Graphene Nanoplatelets Content on the Mechanical and Wear Properties of AZ31 Alloy

Metals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1265
Author(s):  
Tianhui Lu ◽  
Mingyang Zhou ◽  
Lingbao Ren ◽  
Lingling Fan ◽  
Yangyang Guo ◽  
...  
Keyword(s):  
Friction Coefficient ◽  
Yield Strength ◽  
Abrasive Wear ◽  
Mass Loss ◽  
Vickers Hardness ◽  
Base Alloy ◽  
Az31 Alloy ◽  
Graphene Nanoplatelets ◽  
Tensile Yield Strength ◽  
Wear Properties

Graphene, as a rising-star materials, has attracted interest in fabricating lightweight self-lubricating metal matrix composites with superior mechanical and wear properties. In this work, graphene nanoplatelets (GNPs) reinforced AZ31 alloy composites were fabricated by a powder metallurgy technique and then a hot extrusion. The effects of GNPs content (0.5, 1.0, and 2.0 wt.%) on the microstructures, mechanical properties, and wear performance of the extruded GNPs/AZ31 composites were studied. It was found that the addition of GNPs resulted in a weakened basal plane texture and grain refinement of the AZ31 matrix metal. Less than 1.0 wt.% GNPs in GNPs/AZ31 composites resulted in the enhancement in both Vickers hardness and tensile yield strength with acceptable elongation. The Vickers hardness and tensile yield strength of 1.0GNPs/AZ31 composite increased by 4.9% and 9.5% respectively, compared with the unreinforced AZ31. Moreover, the elongation of the composites was about the same as the AZ31 base alloy. Both the friction coefficient and the wear mass loss continuously decreased with the increasing GNPs content, which exhibited a self-lubricating effect. The relationship of the friction coefficient and wear mass loss with the GNPs content could be modeled in terms of the Holliday model and the exponential decay model, respectively. The worn surface morphology revealed that adhesive wear and abrasive wear simultaneously acted in AZ31 alloy. Nevertheless, abrasive wear became the dominant wear mechanism in the GNPs/AZ31 composites.

MULTIDIMENSIONAL TECHNOLOGICAL OPTIMIZATION OF ТHERMOHYDROCHEMICAL TREATMENT OF HARD ALLOY IN THE HYDROSOL OF SILVER GRAPHITE

2021 ◽  
pp. 17-25
Author(s):  
A.A. Shmatov ◽  
◽  
Lubomir Soos ◽  
Zdenko Krajny ◽  
Keyword(s):  
Friction Coefficient ◽  
Hard Alloy ◽  
Solid Lubricant ◽  
Medium Composition ◽  
Optimal Regime ◽  
Mathematical Expressions ◽  
Lubricant Films ◽  
Time Parameters ◽  
Solid Lubricant Films ◽  
Temperature Time

The results examination of the tribotechnical properties for solid lubricant coatings, obtained on hard alloy ВК6 (94 %WC+6 %Co) by thermo-hydrochemical treatment (THCT) in a hydrosol based on silver graphite, are presented. The multidimensional technological optimization of the medium composition and the temperature-time parameters of the process was performed for the friction coefficient of the obtained solid lubricant films. The diagrams “property vs. process parameters” were plotted using the obtained mathematical expressions. Treatment with optimal regime permits decreasing the friction coefficient of the hard alloy surface in 3,5 as compared with untreated.

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