Tensile test stress-strain diagram

As a result of the tensile test, stress-strain diagrams of the samples investigated are shown in Fig. 6. 

O3, h). .. etc. from this family of curves, which form the relaxation curve. Furthermore, by determining the stress which belongs to a specified strain in the relaxation test after a long test time, one can experimentally verify the only calculated tensile test stress-strain-curves for very small deformation rates. The isochronous stress-strain diagram also directly indicates the non-linearity of the visco-elastic behaviour otherwise the curves would be straight lines. 

Figure 5.123 Schematic tensile stress-strain diagram for a symmetric (0, 90°) cross-plied laminate tested at 2 = 0°. Reprinted, by permission, from P. K. Mallick, Fiber-Reinforced Composites, p. 187. Copyright 1988 by Marcel Dekker, Inc.

For practical applications empirically determined creep data are being used, such as D(t) or, more often, E(t) curves at various levels of stress and temperature. The most often used way of representing creep data is, however, the bundle of creep isochrones, derived from actual creep curves by intersecting them with lines of constant (log) time (see Figure 7.7). These cr-e-curves should be carefully distinguished from the stress-strain diagram discussed before, as generated in a simple tensile test ... 

The result of an impact test is basically no more than one point on the general curve of studying strength properties as a function of speed of testing. One advantage an impact test can offer is a ready measure of the actual energy required to break a test piece, which information can also be calculated from stress-strain diagrams in tensile or flexural tests with some effort. 

Young s modulus, also referred to as elastic modulus, tensile modulus, or modulus of elasticity in tension is the ratio of stress-to-strain and is equal to the slope of a stress-strain diagram for the material. In the standard test method, ASTM D412, a force is apphed to a dog-bone-shaped sample of the cured adhesive. The force at elongation (strain) is measured. Most often, the elongation is 25-30% although for elastomeric materials it may be 100% or greater. 

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). 

Quasi-static tensile test - tensile properties without yield point - data Polymer Solids and Polymer Melts C. Bierdgel, W. Grellmann The following Table 4.2 shows a summary of available tensile properties of thermoplastics according to stress-strain diagrams of type a and d ( Fig. 4.3). Table 4.2 Tensile properties of thermoplastics without yield point. ... 

Rgure 2 Load-elongation (stress-strain) diagram with typical cunres of a tensile test (A) with, and (B) without a maximum point (maximum tensile strength). 

Fig. 4.4. Isochronous stress-strain diagram of HDPE material for uniaxial deformation. Continuous line calculated from tensile test, dashed line data measured in creep tests. In an uniaxial deformation force is applied along one direction and only stress and strain components along this direction are considered, e.g. as in the tensile test (Sect 3.2.8). Source (Schmachtenberg 1985)...

The tensile properties of the GM were tested according to EN ISO 527-3. Figure 5.24 shows t5 ical stress-strain diagrams from the tensile test. Using these data, the relative value of the elongation at break, (0... 

If we approximate the stress state at the notch root as uniaxial, the material state must lie on the stress-strain curve measured in tensile tests. This provides another relation between Cmax and max, which are therefore uniquely determined. Graphically, equation (4.5) corresponds to a hyperbola in the a-e space of the stress-strain diagram, since the right side is constant for a given load case. The stresses and strains at the notch root can be found as the intersection of the hyperbola and the stress-strain curve as shown in figure 4.6. 

If we perform cyclic experiments at different strain amplitudes and plot the stabilised values of the stress amplitude, we arrive at the cyclic stress-strain diagram sketched in figure 10.29. Usually, it does not coincide with the result of a monotonous tensile or compressive test. If cyclic hardening occurs,... 

Figure 3-17. Examples of the influence of different test rates and temperatures on basic stress-strain behaviors of plastics, a) Different testing rates, per ASTM D 638, as shown for a polycarbonate b) effects of tensile testing speeds on the shapes of stress-strain diagrams c) a simplified version of the effects on curves of changes in test rates and temperatures.

Tensile stress-strain tests with amorphous rubbers over a range of strain rates and temperatures have shown that for a given rubber the failure point lay along an envelope of the stress-strain diagram (Smith, 1962) (Fig. 4.8) and that the data could be superimposed by a WLF-type shift operation (Fig. 4.9). 

Representative engineering stress-strain diagrams of (a) as-spun and (b) heat-treated PEEK-CNF nanocomposite fibres as a function of nanofibre content. (Tensile tests were based on a constant force ramp. ... 

Tensile test at different temperatures (23°C, 40°C, 60°C, 80°C) and strain rates (1 %/h to 100 %/h) as well as creep and relaxation experiments were accomplished according to DIN EN ISO 53455 and DIN 53444 respectively. Based on creep experiments isochronous stress-strain-diagrams were constructed to describe the relation between stress and strain at defined times. 

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