Stress forces

Dynamic properties are measured by continuous cycles of varying deformation (strain) and/or stress (force required to secure a given strain), at varying frequencies which can be set close to those a component would experience in a tire. These properties are more correlative to many tire performance parameters. 

Because strain is dimensionless, the moduli have the same dimensions as those of stress force per unit area (N m ). In those units, the moduli are enormous, so they are usually reported instead in units of GPa. 

Also called yield stress force necessary to initiate flow in a plastic. 

There are two possible kinds of force acting on a fluid cell internal stresses, by which an element of fluid is acted on by forces across its surface by the rest of the fluid, and external forces, such as gravity, that exert a force per unit volume on the entire volume of fluid. We define an ideal fluid to be a fluid such that for any motion of the fluid there exists a pressure p(x, t) such that if 5 is a surface in the fluid with unit normal vector n, the stress force that is exerted across S per unit area at x at time t is equal to —p x,t)h. An ideal fluid is therefore one for which the only forces are internal ones, and are orthogonal to 5 i.e. there are no tangential forces. ... 

While the general form of the generalized Euler s equation (equation 9.9) allows for dissipation (through the term Hifc) expression for the momentum flux density as yet contains no explicit terms describing dissipation. Viscous stress forces may be added to our system of equations by appending to a (momentarily unspecified) tensor [Pg.467]

The use of stress terminology has been discussed in Chapter 1, where it was pointed out that the value of the term stress in indicating some adverse force or influence lies in its extreme generality, without the need for a precise quantification. Nevertheless it is appropriate that a scientific discipline should be concerned with definable quantities. This will be the starting point for this paper, which will follow the example of Levitt (1972) who applied the concepts and terminology of mechanical stress (force per unit area) and strain (a definable dimension change) to the study of plant responses to the environment. This approach will be developed here in an attempt to incorporate the philosophies behind stress effects into a general treatment of the responses of ecosystems to adverse environmental conditions. 

T is the stress (force per swollen, unstressed cross-sectional area)... 

Oxidized LDL are considered to be one of the major factors associated with the development of atherosclerosis. The earliest event is the transport of LDL into the arterial wall where LDL, being trapped in subendothelial space, are oxidized by oxygen radicals produced by endothelial and arterial smooth muscle cells. The oxidation of LDL in the arterial wall is affected by various factors including hemodynamic forces such as shear stress and stretch force. Thus, it has been shown [177] that stress force imposed on vascular smooth muscle cells incubated with native LDL increased the MDA formation by about 150% concomitantly with the enhancement of superoxide production. It was suggested that oxidation was initiated by NADPH oxidase-produced superoxide and depended on the presence of metal ions. 

Nominal tensile stress, force/initial cross sectional area. 

Stress - Force per unit of original cross sectional area that is applied to a part or specimen. 

Newtonian Substance. Fundamentally, liquids or suspensions in liquids when subjected to a shear stress behave in two ways (1) A Newtonian substance undergoes deformation, the ratio of shear rate (flow) to shear stress (force.) is constant, Se.e Fig. 1. 

Where no linear region is discemable from a force/deformation or a stress/strain curve, use a secant modulus. Construct a secant line from a desired stress (force) point and extend it to the zero strain (deformation) point. Use the slope of this secant line to give the secant modulus. 

Quantitative evaluation of a force-distance curve in the non-contact range represents a serious experimental problem, since most of the SFM systems give deflection of the cantilever versus the displacement of the sample, while the experimentalists wants to obtain the surface stress (force per unit contact area) versus tip-sample separation. A few prerequisites have to be met in order to convert deflection into stress and displacement into tip-sample separation. First, the point of primary tip-sample contact has to be determined to derive the separation from the measured deflection of the cantilever tip and the displacement of the cantilever base [382]. Second, the deflection can be converted into the force under assumption that the cantilever is a harmonic oscillator with a certain spring constant. Several methods have been developed for calibration of the spring constant [383,384]. Third, the shape of the probe apex as well as its chemical structure has to be characterised. Spherical colloidal particles of known radius (ca. 10 pm) and composition can be used as force probes because they provide more reliable and reproducible data compared to poorly defined SFM tips [385]. 

The functioning of a spring valve is based on a pre-stressed spring. When the pre-stress force is reached, the disc starts to move and the valve opens. With lifting equipment attached to the valve spindle, the valve is opened and the pre-stress force measured, taking into account the above factors (seat area and operating pressure). 

Viscoelastic materials are those which exhibit both viscous and elastic characterists. Viscoelasticity is also known as anelasticity, which is present in systems when undergoing deformation. Viscous materials, like honey, polymer melt etc, resist shear flow (shear flow is in a solid body, the gradient of a shear stress force through the body) and strain, i.e. the deformation of materials caused by stress, is linearly with time when a stress is applied [1-4]. Shear stress is a stress state where the stress is parallel or tangencial to a face of the material, as opposed to normal stress when the stress is perpendicular to the face. The variable used to denote shear stress is r which is defined as ... 

Stress Force per unit area on any imaginary plane in an object. Stresses perpendicular to the plane are compressive or tensile stresses parallel with the plane are shear stresses. Up to the elastic limit, stresses produce... 

Modulus—The ratio of stress (force) to strain (elongation) for a given polymer. 

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