Rupture envelope

The uniaxial failure envelope developed by Smith (95) is one of the most useful devices for the simple failure characterization of many viscoelastic materials. This envelope normally consists of a log-log plot of temperature-reduced failure stress vs. the strain at break. Figure 22 is a schematic of the Smith failure envelope. Such curves may be generated by plotting the rupture stress and strain values from tests conducted over a range of temperatures and strain rates. The rupture locus moves counterclockwise around the envelope as the temperature is lowered or the strain rate is increased. Constant strain, constant strain rate, and constant load tests on amorphous unfilled polymers (96) have shown the general path independence of the failure envelope. Studies by Smith (97) and Fishman (29) have shown a path dependence of the rupture envelope, however, for solid propellants. 

The lines OA and OB are tangent to all the stress circles for any value of Py provided the material is noncohesive. They form the Mohr rupture envelope. With cohesive solids or solid masses the tangents forming the envelope do not pass through the origin but intercept the vertical axis at points above and below the horizontal axis. ... 

Equation (13.6) was used to develop a set of creep rupture envelopes to predict attainable creep rupture time at given load L for three mega-coupled composites at 80°C as shown in Fig. 13.18. With measured data only at creep rupture times <100 hr for accelerated tensile creep determinations, we can make estimates for anticipated service lifetime as a function of applied stress load that is indicated by the weight L. 

The closeness in creep rupture envelopes of stress-temperature for 1000-hr duration for the two sets of data shown in Fig. 13.19 provide additional verification for the perfect coupling behavior of mega-coupled composites described in Chapter 12. 

A set of creep experiments at different load levels can be used to build creep-strength time curves indicating at which time- and load-related limits a failure under static load condition is to be expected for a certain adhesive-substrate combination. The construction of a so called creep rupture envelope by connecting the points of the onset of the tertiary creep stage is shown in Fig. 34.12. 

The creep rupture envelope in O Fig. 34.12 was obtained at a temperature of 60°C. Creep rupture envelopes for the same type of adhesive joint at different temperatures may show different characteristics if, for example, the failure mode is changed by the influence of heat. 

The presence of nanopartides suspended within the starch matrix would ensure continuous release of ions into the nutrient media. Copper ions released by the nanopartides may attach to the negatively charged bacterial cell wall and rupture it, thereby leading to protein denaturation and cell death [31]. The attachment of both ions and nanopartides to the cell wall caused accumulation of envelope protein precursors, which resulted in dissipation of... 

As shown in Sect. 2, the fracture envelope of polymer fibres can be explained not only by assuming a critical shear stress as a failure criterion, but also by a critical shear strain. In this section, a simple model for the creep failure is presented that is based on the logarithmic creep curve and on a critical shear strain as the failure criterion. In order to investigate the temperature dependence of the strength, a kinetic model for the formation and rupture of secondary bonds during the extension of the fibre is proposed. This so-called Eyring reduced time (ERT) model yields a relationship between the strength and the load rate as well as an improved lifetime equation. 

Mechanical Methods Static or rotating breaker bars or slowly revolving paddles are sometimes successful. Their application in conjunction with other methods is frequently better. As indicated in the theory of foams, they will work better if installed at a level at which the foam has had some time to age and drain. A rotating breaker works by deforming the foam, which causes rupture of the lamella walls. Rapidly moving slingers will throw the foam against the vessel wall and may cause impact on other foam outside the envelope of the... 

The object is to obtain greater accuracy and range than arc attainable by the case or canister shot, discharged from cannon. These are contained in an envelope which is ruptured either by a bursting charge within or by the force of projection, and have consequently a tendency to scatter over a considerable area. The mitrailleur, or machine-gun, on the contrary, send.s a large number of small projectiles independently, and with precision, to a considerable distance. 

Between photosystem II submembrane fractions which must be isolated and whole cells which must be cultivated, many immobilization works (28 on 45 references cited) employed chloroplasts and thylakoids intact chloroplasts, mixtures of chloroplasts and photosynthetic membranes, or specially, thylakoids alone. To obtain these photosynthetic membranes, the chloroplasts were subjected to osmotic shock by briefly placing them in a hypotonic medium. This procedure ruptures the chloroplast envelope and releases the stroma. The stripped chloroplasts were then returned to an isotonic medium. The interest of this photosynthetic material is justified by a direct contact between the reaction sites and the operation medium. The photosyntheric preparations were often obtained from spinach leaves. 

Digestion of cell envelopes is a more selective technique for the release of intracellular compounds. Contrary to mechanical methods, cell rupture is not required and in most cases cells are merely pemeabilized. The system of choice should be dictated by the chemical composition of the cell envelopes. Among cell permeabi-lization methods, those involving alkali (Wiseman 1995) or organic solvent treatment (Decleire et al. 1987 Bachhawat et al. 1996 Panesar et al. 2007) are usually too harmful, costly and non-specific, so that their use is limited. 

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