The Influence of Frictional Heating on the Sliding Friction of Elastomers and Polymers

1988 ◽  
Vol 61 (1) ◽  
pp. 119-136 ◽  
Author(s):  
C. M. McC. Ettles ◽  
Jui Hsieh Shen
Keyword(s):  
Sliding Friction ◽  
Frictional Heating ◽  
Surface Friction ◽  
Convincing Evidence ◽  
Phase Lag ◽  
Stick Slip ◽  
Factors Affecting ◽  
Practical Applications ◽  
Tan Δ ◽  
Approach Zero

Abstract The friction of polymers and elastomers has been widely researched, both in practical applications and in fundamental experiments. Although some of the basic mechanisms of elastomer friction have been well explored, the effect of frictional heating has not received much attention. This is surprising since the low thermal conductivity of elastomers can result in quite high temperatures being generated at the interface. This paper is concerned specifically with the influence of heat generation on the level of friction at the interface. Some present theories of elastomer friction are well established. The important factors that govern friction are considered to be the strength of interface bonds and the loss tangent, tan δ, where δ is the phase lag between harmonically applied strain and the stress response. On a rough surface, friction is considered to occur from hysteretic losses. On a smooth surface, friction is considered to occur from the formation of bonds across the interface, the extension of the bonds and their eventual fracture. In several quantitative models of elastomer friction summarized by Moore and Geyer, the result for friction is directly proportional to tan δ, thus for a perfectly elastic material, the friction (according to these models) tends to approach zero. Factors affecting the interface bond strength are somewhat better understood, Schallamach proposed that the bonds were molecular. This allowed an Eyring-type rate process theory to be applied, as illustrated with great clarity by Grosch. Grosch showed that the Williams-Landel-Ferry transformation could be applied to condense the friction-speed characteristics measured at various temperatures to a single “master curve.” These experiments gave convincing evidence that rubber friction is a thermally activated, molecular kinetic, stick-slip process. Grosch's experiments were later confirmed by Ludema and Tabor.

scholarly journals Hydroxyurea—The Good, the Bad and the Ugly

Genes ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 1096
Author(s):  
Marcelina W. Musiałek ◽  
Dorota Rybaczek
Keyword(s):  
Cancer Progression ◽  
Specific Interaction ◽  
Interaction Mechanism ◽  
Myeloproliferative Disorders ◽  
Prolonged Treatment ◽  
Actual State ◽  
Cytotoxic Effects ◽  
Factors Affecting ◽  
Cell Cycles ◽  
Practical Applications

Hydroxyurea (HU) is mostly referred to as an inhibitor of ribonucleotide reductase (RNR) and as the agent that is commonly used to arrest cells in the S-phase of the cycle by inducing replication stress. It is a well-known and widely used drug, one which has proved to be effective in treating chronic myeloproliferative disorders and which is considered a staple agent in sickle anemia therapy and—recently—a promising factor in preventing cognitive decline in Alzheimer’s disease. The reversibility of HU-induced replication inhibition also makes it a common laboratory ingredient used to synchronize cell cycles. On the other hand, prolonged treatment or higher dosage of hydroxyurea causes cell death due to accumulation of DNA damage and oxidative stress. Hydroxyurea treatments are also still far from perfect and it has been suggested that it facilitates skin cancer progression. Also, recent studies have shown that hydroxyurea may affect a larger number of enzymes due to its less specific interaction mechanism, which may contribute to further as-yet unspecified factors affecting cell response. In this review, we examine the actual state of knowledge about hydroxyurea and the mechanisms behind its cytotoxic effects. The practical applications of the recent findings may prove to enhance the already existing use of the drug in new and promising ways.

Research on the Friction Performance of Bionic Surface Based on the Clamber Animal Foot Pad

2013 ◽  
Vol 427-429 ◽  
pp. 298-301
Author(s):  
Chun Jian Su ◽  
Zhou Yu Fu ◽  
Hui Sun ◽  
Xiao Shen
Keyword(s):  
Sliding Friction ◽  
External Surface ◽  
Surface Friction ◽  
Friction Mechanism ◽  
Micro Particles ◽  
Bionic Surface ◽  
Friction Performance ◽  
Foot Pad ◽  
The Mathematical Model ◽  
Center Distance

The clamber animal foot pads were researched by the Super Depth of Field3D Microscopic System marked VHX-600 and the flexible non-smooth surface friction mechanism of clamber animal foot pad was analysed through bionic tribology. The total friction includes two aspects: a) The sliding friction caused by the adsorbability between clamber animal foot pad and external surface. b) The embedding resistance caused by the external surface micro particles embedded into clamber animal foot pad. The mathematical model of single convex hull was built and the different center distance bionic surfaces were designed, the friction contact simulation of bionic surface was done by ANSYS and the friction performance of bionic surface was verified through the plane friction testbed.

Frictional Behavior of Textile Fabrics Part I: Sliding Phenomena of Fabrics on Metallic and Polymeric Solid Surfaces

1997 ◽  
Vol 67 (11) ◽  
pp. 793-802 ◽  
Author(s):  
Luis Virto ◽  
Arun Naik
Keyword(s):  
Sliding Friction ◽  
Solid Material ◽  
Solid Surfaces ◽  
Friction Behavior ◽  
Stick Slip ◽  
Compression Load ◽  
Physical Description ◽  
Frictional Behavior ◽  
Textile Fabrics ◽  
Polymeric Solid

This paper presents experimental results on the sliding of fabrics on metallic and polymeric solid surfaces, showing the influence of the compression load at the solid-fabric interface and the nature of the solid material, and the effect of sliding speed on the sliding friction coefficient. At the same time, a physical description of the sliding phenomenon is given. On the basis of these observations, a theoretical approach is developed to explain the sliding friction behavior of fabrics on solid surfaces. Part II will deal with the waving and stick-slip phenomena, which are evident in the sliding process under certain conditions.

A finite element study on effect of frictional heating in the taylor rod impact problem

2014 ◽  
Vol 11 (6) ◽  
pp. 529-542 ◽  
Author(s):  
Sachin Gautam ◽  
Ravindra Saxena
Keyword(s):  
Plastic Deformation ◽  
Finite Element ◽  
High Strain ◽  
Frictional Heating ◽  
Equivalent Plastic Strain ◽  
Surface Friction ◽  
Effect Of Temperature ◽  
Element Formulation ◽  
Strain Rates ◽  
High Strain Rates

In an impact phenomenon the material is subjected to very short duration high force levels resulting large plastic deformations and rise in temperature at high strain rates. A circular rod impacting against a rigid surface called as Taylor rod impact test is widely used for determining the mechanical behaviour of materials subjected to high strain rates with associated increase in temperature. A three-dimensional large deformation, thermo-elasto-plastic, dynamic, contact, finite element formulation is developed to study the effect of temperature rise due to plastic deformation and surface friction on the deformation and stress fields. It is found that the predicted equivalent plastic strain values are influenced by temperature generated due to plastic deformation and surface friction. The values of the coefficient of friction have a profound effect on the location of fracture initiation on the impacting face in a circular rod.

Effects of a stylus on the surface roughness determination in a contact method for paper and paperboard

2019 ◽  
Vol 34 (4) ◽  
pp. 442-452 ◽  
Author(s):  
Hyun Seok Jeong ◽  
Young Chan Ko ◽  
Hyoung-Jin Kim
Keyword(s):  
Surface Roughness ◽  
Surface Characterization ◽  
Paper Industry ◽  
Surface Friction ◽  
Thickness Measurement ◽  
Mean Deviation ◽  
Contact Method ◽  
Average Roughness ◽  
Practical Applications ◽  
Type Contact

Abstract Surface characterization is important and has many applications in the paper industry. It includes both surface roughness and surface friction. In determining the surface roughness of paper and paperboard, non-contact methods such as air-leak methods In characterizing the surface roughness of paper and paperboard, it has been a common practice that the average roughness with the coefficient of variation (COV) has been conventionally determined. This practice, however, this runs the risk of drawing wrong conclusions since two different surfaces having the same average roughness and COV can exhibit totally different properties. To avoid such mistake, a stylus-type contact method has been developed to determine surface roughness of paper and paperboard such as printing & writing (P&W), kraft and liners. In this method, surface roughness profile has been generated to determine its variability which has been defined as the mean deviation from the roughness average, referred to as MDRA. In determining the MDRA, it is noted that thickness measurement is not required. In this method, stylus shape and size, contact force of the stylus to the surface, scan speed and resolution have been identified as the key parameters of generating stable surface roughness profiles. It has been further identified that the optimal conditions on these parameters should depend on paper grade. It is suggested that a stylus-type contact method should be used to determine surface roughness of paper and paperboard to help determine their practical applications such as printing, coating and embossing.

scholarly journals Assessment of Language and Literacy in Children Who Are d/Deaf and Hard of Hearing

2019 ◽  
Vol 9 (3) ◽  
pp. 223 ◽  
Author(s):  
Lianna Pizzo ◽  
Amanda Chilvers
Keyword(s):  
Hard Of Hearing ◽  
Language And Literacy ◽  
Theoretical Orientations ◽  
Factors Affecting ◽  
Research And Practice ◽  
Practical Applications ◽  
Children’S Participation ◽  
Children's Participation ◽  
The Relationship

This article presents theoretical orientations and practical applications for the assessment of d/Deaf and hard of hearing (d/Dhh) children. It discusses current approaches to assessment and the factors affecting d/Dhh children’s participation in assessments using those approaches. Gaps in the field around access to appropriate assessments are discussed. This review also shares information on the relationship between the purpose of the assessment and the approach selected. Basic considerations for both d/Deaf and hard of hearing multilingual learners (d/DMLs) and d/Dhh children with additional disabilities will be addressed. Finally, general recommendations are made for research and practice.

Thermal Instability of Sliding and Oscillations Due to Frictional Heating Effect

1988 ◽  
Vol 110 (1) ◽  
pp. 69-72 ◽  
Author(s):  
I. L. Maksimov
Keyword(s):  
Thermal Instability ◽  
Initial Conditions ◽  
Frictional Heating ◽  
Interface Temperature ◽  
Heating Effect ◽  
Stick Slip ◽  
Instability Development ◽  
The Stability ◽  
Sliding Dynamics ◽  
Sliding Instability

The stability of sliding has been studied, taking into account frictional heating effect and friction coefficient dependence upon the interface temperature and sliding velocity. The collective—thermal and mechanical—sliding instability has been found to exist; instability emergence conditions and dynamics (both in linear and nonlinear stages) have been determined. It is shown that both the threshold and the dynamics of thermofrictional instability differ qualitatively from the analogous characteristics of “stick-slip” phenomenon. Namely, the oscillational instability behavior due to the energy exchange between thermal and mechanical modes has been found to occur under certain initial conditions; the velocities range has been determined for which collective sliding instability may occur whereas the stick-slips would be not possible. The nonlinear analysis of instability evolution has been carried out for pairs with the negative thermal-frictional sliding characteristics, the final stage of sliding dynamics has been described. It is found that stable thermofrictional oscillations can occur on the nonlinear stage of sliding instability development; the oscillations frequency and amplitude have been determined. The possibility has been discussed of the experimental observation of new dynamical sliding phenomena at low temperatures.

scholarly journals Effect of TeO2 addition on the dielectric properties of CaCu3Ti4O12 ceramics derived from the oxalate precursor route

2013 ◽  
Vol 03 (04) ◽  
pp. 1350028 ◽  
Author(s):  
P. Thomas ◽  
K. B. R. Varma
Keyword(s):  
Dielectric Properties ◽  
Dielectric Loss ◽  
Room Temperature ◽  
X Ray Diffraction ◽  
Oxalate Precursor ◽  
X Ray ◽  
Practical Applications ◽  
Low Dielectric ◽  
Precursor Route ◽  
Tan Δ

CaCu 3 Ti 4 O 12 (CCTO) ceramics which has perovskite structure gained considerable attention due to its giant permittivity. But it has high tan δ (0.1 at 1 kHz) at room temperature, which needs to be minimized to the level of practical applications. Hence, TeO 2 which is a good glass former has been deliberately added to CCTO nanoceramic (derived from the oxalate precursor route) to explore the possibility of reducing the dielectric loss while maintaining the high permittivity. The structural, morphological and dielectric properties of the pure CCTO and TeO 2 added ceramics were studied using X-ray diffraction, Scanning Electron Microscope along with Energy Dispersive X-ray Analysis (EDX), spectroscopy and Impedance analyzer. For the 2.0 wt.% TeO 2 added ceramics, there is a remarkable difference in the microstructural features as compared to that of pure CCTO ceramics. This sample exhibited permittivity values as high as 7387 at 10 KHz and low dielectric loss value of 0.037 at 10 kHz, which can be exploited for the high frequency capacitors application.

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