Breaking force

Ea = Arrhenius activation energy Es = excess stress energy AEr = potential barrier for bond rotation Eel = molecular elastic energy F = mean force potential f = average force on the chain fb = bond breaking force H0 = Hookean spring constant kB = Boltzmann constant... 

If the surface of a liquid is regarded as an elastic membrane, then the surface tension is the breaking force of this membrane. Water has one of the highest surface tensions of all liquids. For example, the surface tension of ethanol at 20°C is 22 mN/m, while that of water is 72.75 mN/m. The surface tension of water decreases with temperature. 

Estimates of the ultimate shear strength r0 can be obtained from molecular mechanics calculations that are applied to perfect polymer crystals, employing accurate force fields for the secondary bonds between the chains. When the crystal structure of the polymer is known, the increase in the energy can be calculated as a function of the shear displacement of a chain. The derivative of this function is the attracting force between the chains. Its maximum value represents the breaking force, and the corresponding displacement allows the calculation of the maximum allowable shear strain. In Sect. 4 we will present a model for the dependence of the strength on time and temperature. In this model a constant shear modulus g is used, thus r0=gyb. 

ISO 3341 2000 Textile glass - Yarns - Determination of breaking force and breaking elongation... 

ISO 3342 1995 Textile glass - Mats - Determination of tensile breaking force ISO 3343 1984 Textile glass - Yarns - Determination of twist balance index ISO 3374 2000 Reinforcement products - Mats and fabrics - Determination of mass per unit area... 

ISO 4606 1995 Textile glass - Woven fabric - Determination of tensile breaking force and elongation at break by the strip method... 

Breaking Force in Detonation. See under Breaking Theory of Detonation in Vol 2 of Encycl, p B362 and in this section under (. Detonation (and Explosion), Breaking Theory of Carlf>... 

Figure 8-31 Examples of Compression Curves of Shortenings. (1) and (2) soy-palm (3) soy-canola-palm (4) soy only (5) tallow-lard (6) lard (7) palm-vegetable (8), palm-palm kernel, a = elastic non-recoverable deformation b = viscous flow B = breaking force P = plateau force distance between B and P is an indication of brittleness.

It is worthwhile to derive the second term a different way using a force argument since F is also a force per unit length. On the advancing interface there will be a certain number of network strands, stretched almost to their breaking force f which is approximately... 

We can now compute the surface tension for a molecule which can partially disentangle depending on the value of x, which we take to be randomly distributed over the interval 0 to 1/2. The molecules with x > x contribute their breaking force U/2a and the fraction of these molecules is (l-2x ). The molecules with x < x, contribute their initial force f at which they begin to disentangle. The result on averaging over all strands is... 

Here F is the breaking force, W is the width, and t is the thickness of the coupon, a is the notch depth and Kx is the fracture toughness. W is 43mm aidf(a/W) was obtained from J. G. Williams [6], (Table 6.1 was used, and values were obtained by interpolation.) Note that the subscript for K indicates the direction, and is the same as that adopted in a recent text on fibre composites [7]. 

Ceramic glazes are used in ampuls to introduce a controlled-break site. A band of paint is applied at the constriction of the ampule where controlled breakage is desired, so the contents can be withdrawn. The band is used to make Colorbreak ampuls, and its function is to act as a stress concentrator when bending stress is applied to the ampul to break off the stem for product withdrawal. Very consistent ampul break forces are achieved by the use of ceramic bands. 

To determine the modulus of rupture (breaking force in pounds per square inch) of petroleum wax (ASTM D-2004), a wax slab, 8 x 4 x 0.15 in., is cast over hot water. Small strips, about 3x1 in., are cut from the center of the slab. The strips are placed lengthwise on the support beams of the apparatus, and a breaking beam is placed across the specimen parallel to the support beams. A steadily increasing load is applied by water delivered to a bucket suspended from the breaking beam. The modulus of rupture is calculated from an equation relating the thickness and width of the test specimen to the total weight required to break it. 

The mechanical strength of a hair is determined by measuring its tensile properties using a Diastron or Instron tensile tester. The slope of the post-yield and the breaking force obtained from a typical stress-strain curve have been found to relate to the loss of mechanical strength of the hair and to the percent f reduction of disulfide bonds [79,82,196],... 

In this test, a strip of separator (25 x 150mm) is clamped in a tensile testing machine. The rate of jaw separation is set at 25 5 mm per min and the breaking force is recorded. 

The above estimates are about two hundred times the observed breaking stress. This Is a fairly common type of finding, and the usual conclusion Is that, for various reasons, such as local stress concentrations, the practical adhesion Is far smaller than the Ideal. A more specific picture Is that shown In Figure 11. Remembering the SEM photographs. If the actual Ice-polymer boundary is wavy In contour, the local force, to break the interface Is reduced by the slope of the interface relative to the general plane. If this slope Is about 0.005 breaking forces of the order found would be predicted. 

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