Shear Deformation under Hydrostatic Pressure of Polytetrafluoroethylene and Polycarbonate

Pae, K. D.; Sauer, J. A.; Silano, A. A.

doi:10.1007/978-1-4684-7470-1_192

Cited by 5 publications

(8 citation statements)

References 9 publications

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“…A more detailed modeling may be needed in order to obtain a unified description. Note that similar dependencies of the yield criterion on the hydrostatic pressure have been observed also in other polymers as well as in quasibrittle and frictional materials [5]. The regularities of the pressing out of thin layers may be therefore applicable also to other types of media.…”

Section: Discussionsupporting

confidence: 70%

“…Earlier experimental studies show that the stress-strain curve of many polymers including PTFE starts with a linear Hook's behavior and is followed by linear strain hardening [5]. The yield stress shows strong pressure dependence: for example, in polymehylmethacrylate (PMMA) it is approximately linear with respect to pressure [6], so that Coulombs yield criterion [7] of the type 0 t p can be used, where t is shear modulus at pressure p and is the internal coefficient of friction.…”

Section: Plastic and Tribological Properties Of Polytetrafluoroethylementioning

confidence: 99%

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Plastic and tribological properties of polytetrafluoroethylene (PTFE) under conditions of high pressure and shear

Starcevic

Pohrt²,

Popov

2014

AIP Conference Proceedings

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We investigate experimentally the behavior of a thin sheet of polytetrafluoroethylene between a steel plate and a cylindrical steel indenter under combined action of high normal force and torsion. Under these actions, the polytetrafluoroethylene layer is partially squeezed out of the contact area. The thickness of the remaining layer is studied as function of the applied normal force, the torsion angle, and the radius of the indenter. We suggest a simple semi-empirical material model which describes both the process of squeezing out of the layer and the force of friction produced by the layer

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Section: Discussionsupporting

confidence: 70%

Section: Plastic and Tribological Properties Of Polytetrafluoroethylementioning

confidence: 99%

Plastic and tribological properties of polytetrafluoroethylene (PTFE) under conditions of high pressure and shear

Starcevic

Pohrt²,

Popov

2014

AIP Conference Proceedings

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“…Thus we can approximate the above equation as Thus if we measure A at a fixed load W with a tip of radius of curvature R, we can determine E 1*. Since all the above polymers have Poisson ratios in a similar range, 37 we are mainly measuring differences in E1, the elastic modulus of the polymer. Also it should be noted from eq 6 that the effect of an error in the measurement of R does not have a very pronounced effect on the value of E*.…”

Section: Methodsmentioning

confidence: 99%

Continuum Force Microscopy Study of the Elastic Modulus, Hardness and Friction of Polyethylene and Polypropylene Surfaces

1998

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The atomic force microscope (AFM) has been modified to a continuum force microscope (CFM) by using a tip of a large radius of curvature (1000 nm), in an attempt to reduce the pressure in the contact region. The elastic modulus, hardness, and friction of the surfaces of low density polyethylene, high density polyethylene, isotactic polypropylene, and atactic polypropylene have been quantitatively measured at low loads (10 -8 -10 -6 N) with the CFM. The effect of pressure applied by the tip has been observed in the measurements, resulting in an increase in the elastic modulus and the shear strength of the polymer surface with increasing pressure. The effect of pressure increases with decreasing density of the polymer. The higher values of elastic modulus and hardness of the polymer surface correlate well with the higher crystallinity of the polymers. Frictional properties of the polymers show characteristics that can be explained by the JKR model; the relative frictional behavior of the polyolefin surfaces however is controlled by the deformation component of the friction, i.e., the yield strength, the elastic modulus and the pressure dependence of the shear strength.

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“…Role of hydrostatic pressure in conversion of hardness to flow stress Hydrostatic pressure is known to affect yielding in polymers, [55][56][57] which, for instance, is often modeled using Drucker-Prager or Mohr-Coulomb-type laws. A number of empirical and theoretical studies suggest that for materials that are sensitive to hydrostatic pressure, the ratio H/r is increased.…”

Section: A Conversion Of Hardness To Flow Stressmentioning

confidence: 99%

Broadband nanoindentation of glassy polymers: Part II. Viscoplasticity

2011

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The relationship between hardness and flow stress in glassy polymers is examined. Materials studied include poly(methylmethacrylate), polystyrene, and polycarbonate. Properties are strongly rate dependent, so broadband nanoindentation creep (BNC) is used to measure hardness across a broad range of indentation strain rates (10 À4 to 10 s À1 ). Molybdenum (Mo) is also studied to serve as a "control" whose rate-dependent hardness properties have been measured previously and whose flow stress, unlike the polymers, is pressure insensitive. The BNC hardness data are converted to uniaxial flow stress using two methods based on the usual Tabor-Marsh-Johnson correlation. With both methods the resulting BNC-derived uniaxial flow stress data agree closely with literature compression uniaxial flow stress data for all materials. For the polymers, the BNC hardness data depend on initial rate of loading, indicating that the measured properties are path dependent. Path dependence is not detected in Mo.

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Shear Deformation under Hydrostatic Pressure of Polytetrafluoroethylene and Polycarbonate

Cited by 5 publications

References 9 publications

Plastic and tribological properties of polytetrafluoroethylene (PTFE) under conditions of high pressure and shear

Plastic and tribological properties of polytetrafluoroethylene (PTFE) under conditions of high pressure and shear

Continuum Force Microscopy Study of the Elastic Modulus, Hardness and Friction of Polyethylene and Polypropylene Surfaces

Broadband nanoindentation of glassy polymers: Part II. Viscoplasticity

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