Tensile strength, solid

Fig. 4. Tensile strength (solid lines) of 9% Ni steel welds and the impact strength (dashed lines) of welds with different alloying systems depending on temperature. 1, weld electrode Inconel 625 2, O.OIC, 12Ni, 2Mo, 3Mn, 0.2Ti 3, O.OIC, 19Cr, 15Ni, 6Mn, 2Mo, 0.2N.

Fig. 3.1-93 Irradiation effects on mechanical properties of a ztrcaloy [1.68]. YS - 5deld stress UTS - ultimate tensile strength. Solid lines-, irradiation in the annealed state. Dashed lines irradiation in the 10% cold worked state...

Most solid surfaces are marred by small cracks, and it appears clear that it is often because of the presence of such surface imperfections that observed tensile strengths fall below the theoretical ones. For sodium chloride, the theoretical tensile strength is about 200 kg/mm [136], while that calculated from the work of cohesion would be 40 kg/mm [137], and actual breaking stresses are a hundreth or a thousandth of this, depending on the surface condition and crystal size. Coating the salt crystals with a saturated solution, causing surface deposition of small crystals to occur, resulted in a much lower tensile strength but not if the solution contained some urea. 

The most direct test of the tensile strength hypothesis would be to compare the value of Tq calculated from the closure point of the isotherm by Equation (3.61) with the tensile strength of the bulk liquid determined directly. Unfortunately, experimental measurement of the tensile strength is extremely difficult because of the part played by adventitious factors such as the presence of solid particles and dissolved gases, so that the values in the literature vary widely (between 9 and 270 bar for water at 298 K, for example). 

Orowan (1949) suggested a method for estimating the theoretical tensile fracture strength based on a simple model for the intermolecular potential of a solid. These calculations indicate that the theoretical tensile strength of solids is an appreciable fraction of the elastic modulus of the material. Following these ideas, a theoretical spall strength of Bq/ti, where Bq is the bulk modulus of the material, is derived through an application of the Orowan approach based on a sinusoidal representation of the cohesive force (Lawn and Wilshaw, 1975). 

The importance of inherent flaws as sites of weakness for the nucleation of internal fracture seems almost intuitive. There is no need to dwell on theories of the strength of solids to recognize that material tensile strengths are orders of magnitude below theoretical limits. The Griffith theory of fracture in brittle material (Griflfith, 1920) is now a well-accepted part of linear-elastic fracture mechanics, and these concepts are readily extended to other material response laws. 

The ability to produce very soft solid rubbers but which still retain a good tensile strength. (For example, a vulcanisate with a hardness as low as 18 Shore A is claimed to have a tensile strength as high as 10 MPa). 

Fig. 12. Tensile strength a, vs. number of backbone bonds per monomer 1 /a, reported for a range of polymers by Vincent [75]. The solid line is the theoretical line for vector percolation analysis of strength discussed herein.

The melt flow index describes the viscosity of a solid plastic. It is the weight in grams of a polymer extruded through a defined orifice at a specified time. The melt viscosity and the melt flow index can measure the extent of polymerization. A polymer with a high melt flow index has a low melt viscosity, a lower molecular weight, and usually a lower impact tensile strength. 

For fibres and filaments such orientation is desirable, but for solid objects where impact strength is often more important than tensile strength such orientation is usually unwelcome. It can also have further unwanted effects. This arises from the fact that oriented molecules are basically unstable and will at the first opportunity try to coil up. Thus on heating samples up to temperatures near severe distortion can occur leading to warped mouldings. 

The state of the surface of a brittle solid has been found to exert a considerable influence on the mechanical behaviour observed it is at least as important as the underlying molecular constitution in this regard. The presence of microscopic scratches, voids, or other imperfections will seriously weaken the tensile strength of specimens of glassy polymer, such as poly(methyl methacrylate) at ambient temperatures. 

Fig. 12 Tensile strength of calcium sulfate tablets as a function of magnesium stearate concentration (solid fraction = 0.57). (From Ref. 29.)...

Consider two equal spheres held together by a liquid bridge, as shown in Fig. 4. Two forces contribute to the tensile strength of the bond in an additive fashion the pull due to surface tension at solid-liquid-gas contact line directed along the liquid surface and the negative capillary pressure or the... 

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