Nominal strain

Values and units For ductile materials Stress at yield (MPa) Strain at yield (%) Stress at 50% strain (MPa) Nominal strain at break (%) TfensUe modulus (MPa) If the material does not yield before 50% strain, report stress at 50% strain. Nominal strain at break based on initial and final grip separations, if rupture occurs above 50% nominal strain. One can either report the strain at break or simply >50%. For ductile materials Stress at yield (MPa) Strain at yield (%) Stress at break (MPa) Strain at break (%) Tangent modulus (MPa) Secant modulus (MPa)... 

Fig. 4.23 Examples of stress-strain curves obtained in the 3-cycle load-unload tensile tests of Phase 1. Arrows indicate the direction of straining. Nominal strain-rate = 0.03 s" [135]...

Strain, nominal The strain at a point calculated in the net eross section by simple elastic theory without taking into aceount the effeet on strain produced by geometric discontinuities sueh as holes, grooves, filters, etc. 

Measurement of Residual Stress and Strain. The displacement of the 2 -value of a particular line in a diffraction pattern from its nominal, nonstressed position gives a measure of the amount of stress retained in the crystaUites during the crystallization process. Thus metals prepared in certain ways (eg, cold rolling) have stress in their polycrystalline form. Strain is a function of peak width, but the peak shape is different than that due to crystaUite size. Usually the two properties, crystaUite size and strain, are deterrnined together by a computer program. 

In this case the shear stress (in the plastic deformation region) depends on how much plastic strain y that has accumulated and the current rate of deformation y. For example, in shock compression the shear stress t behind the shock front (where y is nominally zero) is a function of y only, as given by the implicit relationship... 

Lastly, assuming that the rod fragments into pieces of nominal length given by (8.48), a dynamic fracture strain criterion, Sf = e , depending on the prob-... 

There are few problems of praetleal interest that ean be adequately approximated by one-dimensional simulations. As an example of sueh, eertain explosive blast problems are eoneerned with shoek attenuation and residual material stresses in nominally homogeneous media, and these ean be modeled as one-dimensional spherieally symmetrie problems. Simulations of planar impaet experiments, designed to produee uniaxial strain loading eonditions on a material sample, are also appropriately modeled with one-dimensional analysis teehniques. In faet, the prineipal use of one-dimensional eodes for the eomputational analyst is in the simulation of planar Impaet experiments for... 

The kind of stress that we called a tensile stress induces a tensile strain. If the stressed cube of side /, shown in Fig. 3.3(a) extends by an amount u parallel to the tensile stress, the nominal tensile strain is... 

We can now define the elastic moduli. They are defined through Hooke s Law, which is merely a description of the experimental observation that, when strams are small, the strain is very nearly proportional to the stress that is, they are linear-elastic. The nominal tensile strain, for example, is proportional to the tensile stress for simple tension... 

How is it that the modulus can be less Suppose we had loaded the composite in the opposite way, at right angles to the fibres (as in Fig. 6.3(b)) It now becomes much more reasonable to assume that the stresses, not the strains, in the two components are equal. If this is so, then the total nominal strain e is the weighted sum of the individual strains ... 

The plastic behaviour of a material is usually measured by conducting a tensile test. Tensile testing equipment is standard in all engineering laboratories. Such equipment produces a load/displacement (F/u) curve for the material, which is then converted to a nominal stress/nominal strain, or cT l , curve (Fig. 8.10), where... 

The nominal stress at yielding. In many materials this is difficult to spot on the stress-strain curve and in such cases it is better to use a proof stress. 

This equation is given in terms of true stress and true strain. As we said in Chapter 8, tensile data are usually given in terms of nominal stress and strain. From Chapter 8 ... 

In other words, on the point of instability, the nominal stress-strain curve is at its maximum as we know experimentally from Chapter 8. 

Assuming that a diamond-pyramid hardness test creates a further nominal strain, on average, of 0.08, and that the hardness value is 3.0 times the true stress with this extra strain, construct the curve of nominal stress against nominal strain, and find ... 

Sketch curves of the nominal stress against nominal strain obtained from tensile tests on (a) a typical ductile material, (b) a typical non-ductile material. The following data were obtained in a tensile test on a specimen with 50 mm gauge length and a cross-sectional area of 160 mm. ... 

F(FG = normal (shear) component of force A = area u(w) = normal (shear) component of displacement o-(e ) = true tensile stress (nominal tensile strain) t(7) = true shear stress (true engineering shear strain) p(A) = external pressure (dilatation) v = Poisson s ratio = Young s modulus G = shear modulus K = bulk modulus. 

Chapter 8 Nominal and True Stress and Strain, Energy of Deformation... 

Ej (nominal) strain after fracture tensile ductility (dimensionless)... 

It appears that the observed breakdown must be explained in terms of the transient behavior of stress-induced defects even though the stresses are well within the nominal elastic range. In lithium niobate [77G06] and aluminum oxide [68G05] the extent of the breakdown appears to be strongly influenced by residual strains. In the vicinity of the threshold stress, dielectric relaxation associated with defects may have a significant effect on current observed in the short interval preceding breakdown. 

Hydrogen effect on the mechanical properties discussed below was studied on several a and a+fi alloys with the following nominal composition of metallic components (Russian trade marks given in parentheses) commercial titanium of nominal purity 99.3% (VTl-0), Ti-6Al-2Zr-1.5V-lMo (VT20), Ti-6A1-4.5V (VT6), Ti-6Al-2.5Mo-2Cr (VT3-1), Ti-4Al-1.5Mn (OT4), Ti-6.5Al-4Mo-2Sn-0.6W-0.2Si (VT25u) and others. The main features of their stress-strain behavior due to hydrogenation were much similar, but some individuality was characteristic of each alloy. 

Nominal composition in weight % and characteristics 0-2% proof stress (min) (MPa) Tensile strength (MPa) Elongation (min) m Young s modulus (typical) (GPa) Fatigue limit % of T.S.) Bend radius on 2 mm Density (g/cm ) Stress for O 1% total plastic strain in 100 h (MPa) Production range... 

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