Strain static

Results of uniaxial strain static and gas gun compression tests on syntactic foam have been conducted. The foam was buoyant and composed of hollow glass microspheres (average diameter 100 microns) embedded in an epoxy plastic. Static testing consists of compressing a 0.25 cm x 2.5 cm dia. wafer between carefully aligned 2.5 cm dia. steel pistons. Lateral expansion of the wafer is... 

The absolute values of the reductions in moduli, or increases in Mj, can be Interpreted in terms of small, inelastic loops. The small-strain, static moduli measured are consistent with affine chain behaviour, showing, on the basis of one-membered loops, that between about 10 and 20% of groups react to form inelastic loops by the end of a polymerisation. For the more concentrated systems a significant proportion of this comes from post-gel intramolecular reaction (Pr,e Pr,c) ... 

Bending Strain Static elastic modulus (Young s Modulus, i.e., the slope of the stress-strain curve in the elastic region) Crystalline morphological transitions... 

Grow 5-mL overnight cultures of the wild-type and mutant GAS strains statically at 37 °C with 5% CO2 in THY broth. 

The smaU-strain, static shear modulus, G, is defined as... 

Ethylene-acrylic elastomers are highly resistant to the damaging aspects of weather, ie, sun, water, oxygen, and ozone. Vulcanizates have shown little change in tensile properties and no visible signs of surface deterioration after exposure to the elements in Florida for 10 years. Samples imder 20% tensile strain (static) displayed no cracks after one week s exposnre to 100 ppm ozone in air, a concentration 100 times greater than is usually specified in qualifying tests. 

Spring No. Strain static component, mm Strain variable component, mm Stress variable component, MPa Number of cycles before rupture Note... 

Young s modulus can be deterrnined by measuring the stress—strain response (static modulus), by measuring the resonant frequency of the body... 

Shock loading in most metals and alloys produces greater hardening than quasi-static deformation to the same total strain, particularly if the metal undergoes a polymorphic phase transition, such as is observed in pure iron [1]-[10]. Figure 6.1 compares the stress-strain response of an annealed... 

Figure 6.1. Stress-strain behavior of shock-loaded copper compared to the annealed starting condition illustrating an enhanced flow stress following shock-wave deformation compared to quasi-static deformation (based on an equivalent strain basis).

This phenomena has been attributed to the very high strain rates associated with shock loading and the subsonic restriction on dislocation velocity requiring the generation and storage of a larger dislocation density during the shock process than for quasi-static processes [1], [2], [12],... 

To illustrate the effect of radial release interactions on the structure/ property relationships in shock-loaded materials, experiments were conducted on copper shock loaded using several shock-recovery designs that yielded differences in es but all having been subjected to a 10 GPa, 1 fis pulse duration, shock process [13]. Compression specimens were sectioned from these soft recovery samples to measure the reload yield behavior, and examined in the transmission electron microscope (TEM) to study the substructure evolution. The substructure and yield strength of the bulk shock-loaded copper samples were found to depend on the amount of e, in the shock-recovered sample at a constant peak pressure and pulse duration. In Fig. 6.8 the quasi-static reload yield strength of the 10 GPa shock-loaded copper is observed to increase with increasing residual sample strain. 

Figure 6.8. Plot of the quasi-static reloaded yield stress of shock-loaded copper versus the natural logarithm of residual strain for a 10 GPa symmetric shock with 1 /is pulse duration.

Gray and Follansbee [44] quasi-statically tested OFE copper samples that had been shock loaded to 10 GPa and pulse durations of 0.1 fis, 1 /rs, and 2 fus. The quasi-static stress-strain curves are shown in Fig. 7.10 with the response of annealed starting copper included for comparison. The yield strength of shock-loaded copper is observed to increase with pulse duration, as the work-hardening rate is seen to systematically decrease. 

Creep Rupture. When a plastic is subjected to a constant tensile stress its strain increases until a point is reached where the material fractures. This is called creep rupture or, occasionally, static fatigue. It is important for designers... 

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