300% tensile stress

In some materials it is possible for an interior stress to be tensile. All the preceding algebraic relations persist and most of the diagrams persist with their characteristics unchanged only the representation by three ellipses and an ellipsoid no longer works out. 

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Fig. 1. Dependence of indications- Wirotest (a) on the tensile stress in a bar 33 mm made of steel 55...

Fig. 2. Etependence of Wirotest (a) indications as a function of tensile stress, when applying different lengths between the probe and the tested surface.

In Fig, 4. measurement results of a pin of dimensions 46/15,5 have been shown as a function of tensile and compressive stress using the Wirotest , where the course of the graph of these dependence on the load in the linear scope of indications is similar to the compressive as well as the tensile stress. 

Whereas in the scope of plastic deformations differences are observed Arc welding of pipes <6 32 mm, wall thickness 6,5 mm has caused own tensile stress of 260 MPa in the jont, relief at 720°C during 4 hours, has caused a lowering of stress to 60 MPa. 

The changing of welding method to the vibro-contact has caused a lowering of own tensile stress to 180 MPa, whereas in the joint the stress is close to zero After annealing the maximum value of stress has reached 20 MPa... 

Here is tire tensile stress and = lL-/L-, where is tire initial lengtli of tire sample and AL is tire sample elongation. In shear experiments, tire shear relaxation modulus G(t) is defined as where... 

Figure C2.1.16. Tensile stress as a Hmction of the extension ratio registered for a sample of natural mbber (circles). The broken curve is calculated from equation (C2.1.20). (Data from [79].)...

Under compression or shear most polymers show qualitatively similar behaviour. However, under the application of tensile stress, two different defonnation processes after the yield point are known. Ductile polymers elongate in an irreversible process similar to flow, while brittle systems whiten due the fonnation of microvoids. These voids rapidly grow and lead to sample failure [50, 51]- The reason for these conspicuously different defonnation mechanisms are thought to be related to the local dynamics of the polymer chains and to the entanglement network density. 

The separation of two surfaces in contact is resisted by adhesive forces. As the nonnal force is decreased, the contact regions pass from conditions of compressive to tensile stress. As revealed by JKR theory, surface tension alone is sufficient to ensure that there is a finite contact area between the two at zero nonnal force. One contribution to adhesion is the work that must be done to increase surface area during separation. If the surfaces have undergone plastic defonnation, the contact area will be even greater at zero nonnal force than predicted by JKR theory. In reality, continued plastic defonnation can occur during separation and also contributes to adhesive work. 

Elongation. The extension produced by a tensile stress appHed to an elastomer, ie, elongation, is almost always reduced by fillers. Regardless of what type of filler is used, elongation decreases with increased loading above approximately 5 vol % (13). 

Resistance in °C is the temperature differential the two surfaces of a tube or a constrained plate that will cause a tensile stress of 6.9 MPa (1000 psi) on the cooler surface. 

The state of stress in a cylinder subjected to an internal pressure has been shown to be equivalent to a simple shear stress, T, which varies across the wall thickness in accordance with equation 5 together with a superimposed uniform (triaxial) tensile stress (6). 

If it is assumed that uniform tensile stress, like uniform compressive stress (7), has no significant effect on yield, then the yield pressure of a cylinder subjected solely to an internal pressure may be calculated from... 

Division 2. With the advent of higher design pressures the ASME recognized the need for alternative rules permitting thinner walls with adequate safety factors. Division 2 provides for these alternative rules it is more restrictive in both materials and methods of analysis, but it makes use of higher allowable stresses than does Division 1. The maximum allowable stresses were increased from one-fourth to one-third of the ultimate tensile stress or two-thkds of the yield stress, whichever is least for materials at any temperature. Division 2 requkes an analysis of combined stress, stress concentration factors, fatigue stresses, and thermal stress. The same type of materials are covered as in Division 1. 

Mech nic lF tig ue. Some mechanical fatigue tests have been conducted on explosion-clad composites where the plane of maximum tensile stress is placed near the bond 2one (30). 

There are many characteristics of hard cases that make their development desirable. One is wear resistance. Usually, the process is designed to develop high compressive residual stresses in the surface which counteract tensile stresses induced by the loading condition during use of the component (1) (Fig. lb). 

Fig. 2. Schematic stress—strain diagram, where UTS = ultimate tensile stress and (-------------) represents the demarcation between elastic and plastic behavior.

Fig. 9. Variation of tensile properties and grain stmcture with cold working and annealing A, elongation B, yield stress and C, ultimate tensile stress.

Definitions of the commonly measured tensile properties are as follows Unear density (tex) is the weight in grams of 1000 m of yam. Tenacity is the tensile stress at break and is expressed in force-per-unit linear density of unstrained specimen, N /tex. Knot tenacity is the tensile stress required to mpture a single strand of yam with an overhand knot tied in the segment of sample between the testing clamps. It is expressed as force-per-unit linear density and is an approximate measure of the britdeness of the yam. Toop tenacity is the tensile stress required to mpture yam when one strand of yam is looped through... 

The effect of temperature on PSF tensile stress—strain behavior is depicted in Figure 4. The resin continues to exhibit useful mechanical properties at temperatures up to 160°C under prolonged or repeated thermal exposure. PES and PPSF extend this temperature limit to about 180°C. The dependence of flexural moduli on temperature for polysulfones is shown in Figure 5 with comparison to other engineering thermoplastics. 

Fig. 4. Tensile stress—strain curves for polysulfone showing yield behavior at A, 20°C B, 99°C and C, 149°C. To convert MPa to psi, multiply by 145.

Extensional Viscosity. In addition to the shear viscosity Tj, two other rheological constants can be defined for fluids the bulk viscosity, iC, and the extensional or elongational viscosity, Tj (34,49,100—107). The bulk viscosity relates the hydrostatic pressure to the rate of deformation of volume, whereas the extensional viscosity relates the tensile stress to the rate of extensional deformation of the fluid. Extensional viscosity is important in a number of industrial processes and problems (34,100,108—110). Shear properties alone are insufficient for the characterization of many fluids, particularly polymer melts (101,107,111,112). 

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