Nominal tensile stress

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. 

Tensile strength (nominal) Tensile stress (nominal)... 

The maximum tensile stress (nominal) sustained by a test piece during a tension test. 

Tensile stress (nominal) The tensile force per unit area of the original... 

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... 

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 ultimate tensile strength (UTS) of a material refers to the maximum nominal stress that can be sustained by it and corresponds to the maximum load in a tension test. It is given by the stress associated with the highest point in a nominal stress-nominal stress plot. The ultimate tensile strengths of a ductile and of a brittle material are schematically illustrated in Figure 1.11. In the case of the ductile material the nominal stress decreases after reaching its maximum value because of necking. For such materials the UTS defines the onset of plastic instability. 

This result indicates that the stress necessary to cause brittle fracture is lower, the longer the existing crack and the smaller the energy, P, expended in plastic deformation. The quantity Of represents the smallest tensile stress that would be able to propagate the crack of length 2 L. The term Of (tt L)°5 is generally denoted by the symbol K and is known as the stress-intensity factor (for a sharp elastic crack in an infinitely wide plate). Fracture occurs when the product of the nominal applied stress and the stress concentration factor of a flaw attains a value equal to that of the cohesive stress. 

Most testing of the theory has been done with tensile deformations. According to Eqs. (7.1) and (7.2) the nominal tensile stress /, the tensile force per unit unstretched area, is related to a, the ratio of stretched to unstretched length, by ... 

Nominal tensile stress, force/initial cross sectional area. 

It is usual in rubber testing to calculate tensile stresses, including that at break, on the initial cross-sectional area of the test piece. Strictly, the stress should be the force per unit area of the actual deformed section but this is rather more difficult to calculate and in any case, it is the force that a given piece of rubber will withstand which is of interest. The stress calculated on initial cross-section is sometimes called nominal stress. ... 

Figure 2. Cyclic tensile stress-strain behavior of TR-41-1649 and its blend with polystyrene (M 20,400) at room temperature at a constant rate of tensile strain, 50%/min. Curves (1) and (2) refer to the first and second stretching half-cycles, respectively, and the tensile stress is expressed in terms of nominal stress (29).

Key factors of SCC. The stress applied on a metal is nominally static or slowly increasing tensile stress. The stresses can be applied externally, but residual stresses often cause SCC failures. Internal stresses in a metal can be due to cold work or a heat treatment. In fact, all manufacturing processes create some internal stresses. Stresses introduced by cold work arise from processes such as lamination, bending, machining, rectification, drawing, drift, and riveting. Stresses introduced by thermal treatments are due to the dilation and contraction of metal or indirectly by the modification of the microstructure of the material. Welded steels contain residual stresses near the yield point. Corrosion products have been shown to be another source of stress and can cause a wedging action. 

The distinction between elastomers, fibers, and plastics is most easily made in terms of the characteristics of tensile stress-strain curves of representative samples. The parameters of such curves are nominal stress (force on Ihe specimen divided by the original cross-sectional area), the corresponding nominal strain (increase in length divided by original length), and the modulus (slope of the stress-strain curve). We refer below to the initial modulus, which is this slope near zero strain. 

When a material is subjected to small deformations, the cross-sectional area of the unstrained sample, Aq, coincides with the cross-sectional area of the strained sample, A. However, in the case of elastomers, in which the deformations can be extremely high, account has to be taken of the change in the cross section of the sample. Consequently, the value of the stress a, calculated by using Eq. (3,33) and called nominal stress, does not coincide with the true tensile stress (A (Fig. 3.10). 

The nominal tensile stress (tensile force/initial area) is tr = dW/dA, so... 

Conversely, the intensity of tensile stresses decreased and the rock mass does not risk any more a damage by rupture in traction. With regards to the model with the wide apart wells and galleries, behavior in compression is unchanged compared to the nominal case and the rupture zone in traction is a little more developed. 

It is usual in rubber testing to calculate tensile stresses, including those at break, on the initial cross-sectional area of the test piece, and these stresses are sometimes called nominal stresses. 

Tensile stress at v% strain the stress at which the strain reaches the specified value. v expressed in percentage. It may be measured, for example, if the stress-strain curve does not exhibit a yield point. In this case. v must be defined either in the relevant product standard or agreed upon by the interested parties Tensile strain the increase in length per unit original length of the gauge. It is used for strains up to the yield point for strains beyond this limit see nominal tensile strain below... 

Nominal tensile strain at break the nominal tensile strain at the tensile stress at break, if... 

HSC involves the brittle fracture of a nominally ductile alloy under a sustained load at tensile stresses below the yield strength. For HSC to occur, hydrogen must be absorbed into the alloy and then transported through it, along either a concentration gradient or a stress gradient. Some time is therefore required for cracks to nucleate. HSC is normally associated with steels but has been observed to a limited extent in other materials when hydrogen is concentrated near the surface. 

If yielding is to occur by sliding parallel to any plane, it seems reasonable to suppose that there must be a critical shear stress r parallel to that plane. It is also physically reasonable to assume that this critical stress x will be increased if the compressive stress —mean normal stress, as just defined, not nominal stress. Remember also that the usual convention for stress makes - -a the tensile stress.) The simplest assumption is that x depends linearly on Coulomb yield criterion ... 

The nominal tensile stress is given by the tensile force divided by the unstrained cross-sectional area of the specimen. It has been commonly used in the literature dealing with deformation and fracture of elastomers.) This reduction scheme is clearly quite successful in dealing with a wide range of crosslinking (see Figure 10.25) (Smith, 1969). 

Based on the stress-strain diagram the values tensile stress at yield cXy and tensile strength at maximum (7m as well as the associated normative yield strain and nominal strain 8tM or normative strain 8m at tensile strength as well as strain at break 8b can be calculated (Eqs. 4.6. 11). For completely recorded diagrams the nominal strain at break 8tB can be determined additionally (Eq. 4.12). Because of the dependence on software and test equipment, especially sampling rate, the tensile stress at break (Tb should not be used (Eq. 4.13). Due to the viscoelastic behaviour of the plastics modulus of elasticity in tension is determined as secant modulus between the strain limits of 0.05 % and 0.25 % (Eq. 4.14). If the transverse strain is recorded simultaneously using strain gauges Poisson ratio jl can be calculated (Eq. 4.15). 

High temperature crack growth behavior under creep conditions was studied in SiC whisker-reinforced mullite. Four-point flexumral specimens were prepared for crack growth experiments by introducing Vickers indentation-induced cracks on the tensile surface. Samples were tested in creep in air at a nominal smface tensile stress at 150 MPa and a temperature of 1400°C. Crack growth and nucleation, and extent of creep-strain were... 

Continue Problem 3.4 to show that, in the case of an ideal rubber of density p and specific heat capacity c under a nominal tensile stress temperature rises with extension ratio A during adiabatic stretching according to... 

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