Tensile elastic limit

This is not a bad assumption, since the material under tension will fail somewhere in the region just beyond the end of the tensile elastic limit. Therefore, the elastic or longitudinal wave velocity is quite appropriate. 

It is usually desirable to run a simple bulk tensile test program and subsequently predict (calculate) shear properties from their tensile counterparts. This approach requires a clearly defined relationship between shear and tensile elastic limit and yield variables and material properties. The elastic limit and yield stress values can be related between tensile and shear conditions by using an appropriate failure criterion, such as maximum normal stress, maximum shear stress, and distortion energy criteria. A material parameter that needs to be converted in addition to the usual elastic properties is the viscosity coefficient. This can be done by using Tobolsky s (1960) assumption of equivalent relaxation times in shear and tension. Application of this assumption results in the relation ... 

Yield strength or tensile proof stress the maximum stress that can be applied without permanent deformation of the test specimen. For the materials that have an elastic limit (some materials may not have an elastic region) this may be expressed as the value of the stress on... 

In a tensile test, as the load increases, the specimen at first is strained elastically, that is reversibly. Above a limiting stress - the elastic limit - some of the strain is permanent this is plastic deformation. 

Designers of most structures specify material stresses and strains well within the pro-portional/elastic limit. Where required (with no or limited experience on a particular type product materialwise and/or process-wise) this practice builds in a margin of safety to accommodate the effects of improper material processing conditions and/or unforeseen loads and environmental factors. This practice also allows the designer to use design equations based on the assumptions of small deformation and purely elastic material behavior. Other properties derived from stress-strain data that are used include modulus of elasticity and tensile strength. 

For materials that deviate from the proportionality law even well below the elastic limit, the slope of the tangent to the stress-strain curve at a low stress level is taken as the tensile modulus. When the stress-strain curve displays no proportionality at any stress level, the secant modulus is employed instead of the tensile modulus (Fig. 2-2). The secant modulus is the ratio of stress to corresponding strain, usually at 1% strain or 85% from the initial tangent modulus. 

It may be pointed out that the term yield point is sometimes erroneously used as a synonym for elastic limit and proportional limit As it has been described in the paragraphs above it is actually a phenomenon that occurs in only a very small number of cases in tensile testing. As it has also been observed in the description that graphically and experimentally, it is an anomalous behaviour in which there is a strain occurring with no increase in stress. 

Uses of Vanadium, (a) Vanadium Steels.—By far the largest proportion of the world s production of vanadium is absorbed in the production of ferrovanadium alloy for the manufacture of vanadium steels, which usually contain up to 0-8 per cent, of vanadium. The effect of the addition of vanadium to a steel is to increase its tensile strength enormously, also its hardness, and its resistance to shock and fatigue.6 A good carbon steel containing about 1-10 per cent, of carbon has an elastic limit of about 30 tons per square inch and an ultimate... 

Three important properties can be inferred from the tensile test i.e. elastic limit (i.e. the point of maximum elastic elongation), tensile strength and E-modulus. In many cases the transition point between the elastic and plastic deformation is not visible in the graph. For that reason it has been determined that this point is situated at an value of 0.002 and the accompanying tensile stress is determined as represented in figure 10.9. 

A typical stress-strain diagram for a metal is shown in Fig. 11. This metal follows Hook s law up to a proportional limit ox yield strength) of 2 x 109 Pa. The elastic limit, above which the metal undergoes plastic deformation, which is not recoverable when the stress is removed, is close to the proportional limit. The maximum stress that the metal can support is the ultimate strength (or tensile strength) of the metal, which occurs at the maximum extension of the material. 

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... 

Alloys.1—The most important alloy of molybdenum is ferro-molybdenum, which is used as an addition to steel. The effect of molybdenum on steel is similar to that of tungsten, but is more marked the tensile strength is increased and the elastic limit raised. For highspeed tool-steels molybdenum is often used in conjunction with tungsten. It has been found that the addition of molybdenum in small quantities (up to 15 per cent.) to steel increases the liability to corrosion, especially in acid and salt solutions. An important use of steels containing 3 to 4 per cent, of molybdenum and 1-0 to 1-5 per cent, of carbon is for the manufacture of permanent magnets. ... 

Yield strengths correspond to the stresses causing permanent deformation of the metal (i.e., beyond the elastic limit). Tensile strengths correspond to stresses at the point of ultimate metal failure. 

The deformation of elastic solids occurs because of the stretching of intermo-lecular bonds to a point where internal stresses balance the externally applied stress (11,13). At this point, an equilibrium deformation is established. As there is little motion involved in the stretching of bonds, this occurs rapidly, and the equilibrium deformation is established infinitesimally. Deviations from ideal identity occur whenever the elastic limit of the solid material is exceeded and irreversible sample deformation results, i.e., breakage of chemical bonds (2,14). Irreversible sample deformation leading to fracture forms the basis of tensile testing (11). 

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