Frictional Characteristics of Apparel Fabrics

1988 ◽  
Vol 58 (3) ◽  
pp. 129-136 ◽  
Author(s):  
W. W. Carr ◽  
J. E. Posey ◽  
W. C. Tincher
Keyword(s):  
Frictional Force ◽  
Normal Force ◽  
Unit Area ◽  
Dynamic Friction ◽  
Apparent Area

A study has been conducted to determine the frictional characteristics of several fabrics used in apparel. The objective was to generate fabric frictional data to help in developing automated assemblies for fabrics. The results revealed that the coefficients of static and dynamic friction between fabrics decreased as the normal force per unit area increased. Wilson's model relating frictional force to normal force and the apparent area of contact closely correlated the data.

PREDICATION FOR RELATIVE MOTION OF THE COLONOSCOPE IN COLONOSCOPY

2013 ◽  
Vol 13 (03) ◽  
pp. 1350023 ◽  
Author(s):  
WU BIN CHENG ◽  
MICHAEL A. J. MOSER ◽  
SIVARUBAN KANAGARATNAM ◽  
WEN JUN ZHANG
Keyword(s):  
Frictional Force ◽  
Frictional Contact ◽  
Linear Complementarity ◽  
Intestinal Wall ◽  
Deformable Objects ◽  
Dynamic Friction ◽  
Unilateral Constraints ◽  
Common Procedure ◽  
Mechanical Compliance ◽  
Signorini's Problem

Colonoscopy is common procedure frequently carried out. It is not without its problems, which include looping formation. Looping formation prevents the tip of the colonoscope itself from advancing, thus further probing induces a risk of perforation, significant patient discomfort, and failure of colonoscopy. During colonoscopy, the manipulated colonoscope for intubation in the colon goes through the friction between the colonoscope and the colon. Due to major frictional force, the sigmoidal colon forms looping with the scope during intubation. The interactive frictional force between the colon and the colonoscope is highly complex because of frictional contact between two deformable objects. In this paper, contact force computation was formulated into a linear complementarity problem (LCP) by linearizing Signorini's problem, which was adapted into non-interpenetration with unilateral constraints. Frictional force was computed by the mechanical compliance of finite element method (FEM) models with the consideration of dynamic friction between the colonoscope and the intestinal wall. Furthermore, we presented a mathematical model of the elongation of the colon that predicts the motion of scope relative to the intestinal wall in colonoscopy.

Coefficients of Friction: Static Versus Dynamic

2020 ◽  
Author(s):  
Jack Youqin Huang
Keyword(s):  
Coefficient Of Friction ◽  
Frictional Force ◽  
Inertial Force ◽  
Static Friction ◽  
Theory And Practice ◽  
Dynamic Friction ◽  
Kinetic Friction ◽  
The Coefficient Of Friction ◽  
Static Versus Dynamic ◽  
New Discovery

Abstract This paper deals with the problem of static and dynamic (or kinetic) friction, namely the coefficients of friction for the two states. The coefficient of static friction is well known, and its theory and practice are commonly accepted by the academia and the industry. The coefficient of kinetic friction, however, has not fully been understood. The popular theory for the kinetic friction is that the coefficient of dynamic friction is smaller than the coefficient of static friction, by comparison of the forces applied in the two states. After studying the characteristics of the coefficient of friction, it is found that the comparison is not appropriate, because the inertial force was excluded. The new discovery in the paper is that coefficients of static friction and dynamic friction are identical. Wheel “locked” in wheel braking is further used to prove the conclusion. The key to cause confusions between the two coefficients of friction is the inertial force. In the measurement of the coefficient of static friction, the inertial force is initiated as soon as the testing object starts to move. Therefore, there are two forces acting against the movement of the object, the frictional force and the inertial force. But in the measurement of the coefficient of kinetic friction, no inertial force is involved because velocity must be kept constant.

Comparison of Multiscale Analytical Model of Friction and Wear of Viscoelastic Materials With Experiments

2017 ◽  
Author(s):  
Anahita Emami ◽  
Seyedmeysam Khaleghian ◽  
Chuang Su ◽  
Saied Taheri
Keyword(s):  
Friction Coefficient ◽  
Rough Surface ◽  
Analytical Model ◽  
Dynamic Modulus ◽  
Friction And Wear ◽  
Normal Force ◽  
Rough Surfaces ◽  
Dynamic Friction ◽  
Viscoelastic Materials ◽  
Fractal Properties

Friction and wear of viscoelastic materials like rubbers are topics of extreme practical importance such as the construction of tires, shoe heels and soles, rubber O-ring seals, and wiper blades. Friction of viscoelastic materials differs from the frictional properties of the elastic solids as friction is directly related to energy dissipation via the internal damping of such materials while purely elastic materials do not dissipate energy. Based on hysteresis properties of viscoelastic materials, physics based multiscale models were developed by Persson for fiction [1, 2] and powdery wear [3] of rubbers sliding on rough surfaces. In this research, these theories were studied and the theoretical results were compared with experimental results obtained from a dynamic friction/wear tester. The inputs to the theoretical models were the fractal properties of the rough surface, the dynamic modulus, and the fatigue behavior of the viscoelastic material. The fractal properties of the rough surface was obtained from the 3D profile of the surface measured using an optical profilometer. The dynamic modulus of the rubber samples was characterized via dynamic mechanical analysis at different frequencies and temperatures. The fatigue crack growth behavior of the samples were found from experimental results of crack propagation versus tearing energy obtained from the fatigue test. Then, the friction coefficient between different rubber samples and rough surfaces was calculated as a function of sliding velocity using both analytical model and experimental approach. In the dynamic friction/wear tester, normal force was adjusted and measured accurately, in addition, the frictional force was measured using a load cell in longitudinal direction along the sliding axis. The experimental sliding friction coefficient was calculated as the ratio of longitudinal force at a constant velocity to the normal force. The mass loss of rubber sample was measured by weighting the sample before and after each test to obtain the wear rate. The comparison between experimental and analytical results showed that the friction model could predict the friction coefficient accurately while the theory of powdery wear is unable to capture all the physics involved in rubber wear on rough surfaces.

The Effect of Abrading Surfaces on the Wear of Rubber Tread Compounds

1995 ◽  
Vol 68 (4) ◽  
pp. 609-622 ◽  
Author(s):  
R. Ramakrishnan ◽  
J. A. Donovan ◽  
A. I. Medalia
Keyword(s):  
Wear Rate ◽  
Frictional Force ◽  
Unit Area ◽  
Normal Load ◽  
Grit Size ◽  
Rubber Compounds ◽  
Preliminary Model

Abstract The wear rate, produced by a modified Lambourn abrader, of rubber tread compounds, depends on the normal load, frictional force, the grit size and the number of grits per unit area of the grindstone. A preliminary model for the wear rate incorporating the grindstone characteristics, the normal and frictional force, and the fatigue exponent of the compound has been developed. The model needs further refinement but predicted the wear rate of SBR and EXXPRO™ rubber compounds well enough to be developed further. The current major limitation is accurate characterization of the grindstone.

Report 23: Considerations in the Design of Plain Sliding Test Rigs

1967 ◽  
Vol 182 (7) ◽  
pp. 118-121
Author(s):  
S. W. E. Earles ◽  
D. G. Powell
Keyword(s):  
Frictional Force ◽  
Normal Force ◽  
Testing Machine ◽  
Wear Rates ◽  
Sliding Test ◽  
Experimental Rig ◽  
Realistic Appraisal ◽  
Subsequent Incorporation

After outlining the relative merits of rig-testing of materials compared with testing in situ the fundamental considerations in the design of the testing machine are discussed. Of basic importance is a realistic appraisal of the conditions under which the material is to be used and the subsequent incorporation of accurately simulated conditions in the experimental rig. In particular the thermal resistances in the rig should be approximately proportional to those existing in the proposed application. The paper outlines ways of measuring normal force, frictional force and wear rates and emphasizes the need to record some variables continuously.

Frictional properties of plastics

1952 ◽  
Vol 212 (1111) ◽  
pp. 488-491 ◽  
Keyword(s):  
Shear Strength ◽  
Frictional Force ◽  
Unit Area ◽  
Linear Polymers ◽  
Frictional Properties ◽  
Strong Adhesion ◽  
Important Exception ◽  
Heavy Loads

The frictional properties of a group of linear polymers have been investigated over a range of loads from 0-04 to 10000 g. Deviations from Amontons’s law occur at light loads. At heavy loads the frictional force is proportional to the area of contact. The force per unit area of contact resisting sliding can be calculated from the frictional force, and is found to be roughly equal to the specific shear strength of the plastic itself. This suggests that strong adhesion occurs over the region of contact, and that, during sliding, shearing occurs within the bulk of the plastic rather than at the interface. The corollary to this, the transfer of material between the two surfaces, has been demonstrated. The frictional properties of plastics can thus be explained by the theory developed by Bowden and his co-workers for the friction of metals. An important exception to these conclusions is polytetrafluorethylene. The force per unit area of contact resisting sliding is much less than the shear strength of the plastic itself.

Radiation Damage, Contrast and Statistics in High Resolution Biological Electron Microscopy

1970 ◽  
Vol 28 ◽  
pp. 260-261
Author(s):  
Robert M. Glaeser
Keyword(s):  
High Resolution ◽  
Particle Flux ◽  
Unit Area ◽  
Signal To Noise ◽  
Resolution Image ◽  
High Resolution Image ◽  
Pass Through ◽  
Counting Statistics ◽  
The Relationship ◽  
Picture Element

It is well known that a large flux of electrons must pass through a specimen in order to obtain a high resolution image while a smaller particle flux is satisfactory for a low resolution image. The minimum particle flux that is required depends upon the contrast in the image and the signal-to-noise (S/N) ratio at which the data are considered acceptable. For a given S/N associated with statistical fluxtuations, the relationship between contrast and “counting statistics” is s131_eqn1, where C = contrast; r2 is the area of a picture element corresponding to the resolution, r; N is the number of electrons incident per unit area of the specimen; f is the fraction of electrons that contribute to formation of the image, relative to the total number of electrons incident upon the object.

Reconstruction of Objects from their Projections Using Orthogonal Functions

1973 ◽  
Vol 31 ◽  
pp. 268-269
Author(s):  
Elrnar Zeitler
Keyword(s):  
Unit Area ◽  
Three Dimensional ◽  
One Dimension ◽  
Spatial Density ◽  
Dimensional Representation ◽  
Orthogonal Functions ◽  
Object A ◽  
Plane Normal ◽  
Dimensional Object ◽  
Spatial Density Distribution

Considering any finite three-dimensional object, a “projection” is here defined as a two-dimensional representation of the object's mass per unit area on a plane normal to a given projection axis, here taken as they-axis. Since the object can be seen as being built from parallel, thin slices, the relation between object structure and its projection can be reduced by one dimension. It is assumed that an electron microscope equipped with a tilting stage records the projectionWhere the object has a spatial density distribution p(r,ϕ) within a limiting radius taken to be unity, and the stage is tilted by an angle 9 with respect to the x-axis of the recording plane.

Morphometric SEM study of the effects of ACTH on endothelial fenestrae in the rat adrenal cortex

1984 ◽  
Vol 42 ◽  
pp. 234-235
Author(s):  
J. Curtis ◽  
K. S. Schwartz ◽  
R. P. Apkarian
Keyword(s):  
Anterior Pituitary ◽  
Lipid Droplets ◽  
Adrenocorticotropic Hormone ◽  
Unit Area ◽  
High Density Lipoproteins ◽  
Capillary Endothelium ◽  
Zona Fasciculata ◽  
Sem Study ◽  
Saline Vehicle ◽  
Scanning Electron

A scanning electron microscope (SEM) study was made of the effect of adrenocorticotropic hormone (ACTH) on the size and numbers of fenestrae/unit area in the capillary endothelium of the zona fasciculata (ZF) of the rat adrenal. The stimulatory effect of ACTH on cholesterol uptake via high density lipoproteins in the rat and evidence for the secretion of glucocorticoids by exocytosis of lipid droplets described by Rhodin suggest that endothelial change may accompany these transport phenomena.Twelve rats received two Dexamethasone (DEX) ip injections (25 μg DEX/100 g body wt.), the first at 8 PM and the second at 8 AM the next day, to inhibit the release of endogenous ACTH by the anterior pituitary. The animals were then divided into two groups. Six animals received only saline vehicle and six rats received ACTH (100 ng/100 g body wt.).

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