Pressure stress-strain curve

Confining pressure is 10 MPa in Fig. 1. The unloading point is elastic stage, in the increasing process of axial pressure, stress-strain curve is almost linear, the slope of axial strain is less than circumferential strain, that is, the rate of increase of axial strain of specimens is more that circumferential strain. 

If the material is to be used in vessels to operate under external pressure, stress-strain curves (tension or compression) shall be furnished for a range of design temperature desired. 

Little error is introduced using the idealized stress—strain diagram (Eig. 4a) to estimate the stresses and strains in partiady plastic cylinders since many steels used in the constmction of pressure vessels have a flat top to their stress—strain curve in the region where the plastic strain is relatively smad. However, this is not tme for large deformations, particularly if the material work hardens, when the pressure can usuady be increased above that corresponding to the codapse pressure before the cylinder bursts. 

Figure 7.10. Reload stress-strain curves for recovered OFE copper subject to shock compression of 10 GPa peak pressure and pulse durations of 0.1 /rs, 1.0 /rs, and 2.0 /rs.

Stress-strain curves and microstructure from specimens of pipeline steels precharged with high-pressure gaseous hydrogen at 20,000 psi and 100°C for 8 days (a) API X70, (b) API X70/X80 type, and (c) API X70/X80 type. 

The isochronous stress-strain curves for the creep of PP bead foams (254) were analysed to determine the effective cell gas pressure po and initial yield stress do as a function of time under load (Figure 11). po falls below atmospheric pressure after 100 second, and majority of the cell air is lost between 100 and 10,000 s. Air loss is more rapid than in extruded PP foams, because of the small bead size and the open channels at the bead boundaries, do reduces rapidly at short yield times <1 second, due to proximity of the glass transition, and continues to fall at long times. 

Fig.69 Tensile stress-strain curves for BPA-PC at various pressures (From [54])...

Figure 7.8. Total, elastic, and viscous stress-strain curves for crosslinked self-assembled collagen fibers. Total (open squares), elastic (filled diamonds) and viscous (filled squares) stress-strain curves for self-assembled collagen fibers obtained from incremental stress-strain measurements at a strain rate of 10%/min.The fibers were tested after aging for three months at room temperature and pressure. Note that the viscous stress-strain curve is below the elastic curve suggesting that elastic deformation is the predominant energy-absorbing mechanism for crosslinked collagen fibers.

FIG. 13.72 Shear stress-strain curves for PMMA at 22 °C under different pressures at a strain rate of approximately 4 x 10-4 s. The filled circles connect all fracture points in a fracture envelope. 

A detailed atomistic approach was used to investigate the molecular segment kinematics of a glassy, atactic polypropylene system dilated by 30%. ° The microstructural stress—dilation response consists of smooth, reversible portions bounded by sudden, irreversible stress jumps. But compared to the micro-structural stress—strain curve of the shear simulation, the overall trend more closely resembles macroscopic stress—strain curves. The peak negative pressure was in the neighborhood of 12% dilatation, with a corresponding secondary maximum in the von Mises shear stress. The peak negative pressure was re-... 

Figure 9.4. Stress-strain curves observed by Morrison-Smith et al. (1976) at the temperatures shown with specimens cut from the z-growth region of a single crystal of synthetic quartz (W2 with a water content of l,600-200H/10 Si). Stress normal to (lOTl) confining pressure 300 MPa strain-rate 10 s .

Figure 9.19. Stress-strain curves for single crystals of natural quartz deformed in buffered assemblies at 1.64 GPa confining pressure, 800°C, and strain-rate of 10 s after 20 hours preconditioning. (From Ord and Hobbs 1986.)...

Figure 14.8 shows stress-strain curves for polycarbonate at 77 K obtained in tension and in uniaxial compression (12), where it can be seen that the yield stress differs in these two tests. In general, for polymers the compressive yield stress is higher than the tensile yield stress, as Figure 14.8 shows for polycarbonate. Also, yield stress increases significantly with hydrostatic pressure on polymers, though the Tresca and von Mises criteria predict that the yield stress measured in uniaxial tension is the same as that measured in compression. The differences observed between the behavior of polymers in uniaxial compression and in uniaxial tension are due to the fact that these materials are mostly van der Waals solids. Therefore it is not surprising that their mechanical properties are subject to hydrostatic pressure effects. It is possible to modify the yield criteria described in the previous section to take into account the pressure dependence. Thus, Xy in Eq. (14.10) can be expressed as a function of hydrostatic pressure P as... 

Figure 2. Stress-Strain curves obtained by triaxial compression test. Confining pressure is lOOMPa and pore pressure is 25MPa.

Figure 5. Stress-strain curve of SII hydrate-bearing coal under confining pressure 1 MPa and 3 MPa.

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