Deformation specimen

Length of an elastically deformed specimen, and its relaxed length (Chap. XI). 

Values of stress and strain obtained from Figure 1 and from similar plots of data obtained on the other elastomers yield the plots of Xo vs. (X — 1) in Figure 2, where Xo is the true stress, i.e., the force per unit cross-sectional area of the deformed specimen. The data at strains up to 1.0 (100% elongation) give straight lines whose slopes equal the equilibrium tensile moduli, E values of 1 /3 are given in Table I. 

When the network junctions are entirely immobilized by the surrounding chains, h equals zero. Then the junctions in a deformed specimen are displaced in proportion to the macroscopic strain, i.e., the deformation is affine. Alternatively, h equals unity when junction fluctuations are not impeded, the defining characteristic of a phantom network (16, 17). The parameter h was introduced (13) to allow empirically for different degrees of fluctuations. For undiluted networks at small deformations, h should usually be small, though not necessarily zero. 

PPD effects on surface layers microstructure. The porosity is observed in the core of deformed specimens unlike non-deformed ones as a result of -and... 

Analyses of the results obtained depend on the shape of the specimen, whether or not the distribution of mass in the specimen is accounted for and the assumed model used to represent the linear viscoelastic properties of the material. The following terms relate to analyses which generally assume small deformations, specimens of uniform cross-section, non-distributed mass and a Voigt-Kelvin solid. These are the conventional assumptions. 

Resilience The rafio of energy oufput to energy input in a rapid (or instantaneous) full recovery of a deformed specimen. 

Further on, the true stress reaches a maximum, denoted as ay, corresponding to the yield point. At this stress value, the specimen no longer goes back to zero strain, a permanent deformation remains, which can be removed only by heating the deformed specimen above Ta. It is worth noting that the permanent deformation obtained when reaching ay is much smaller than the strain at the yield point, ey. 

This conclusion was only partly confirmed by scanning electron microscopy micrographs of RuC>4 stained surfaces taken at the crack tip of deformed specimens at 1ms-1, where the non-nucleated and /3-nucleated materials showed, respectively, a semi-brittle and semi-ductile fracture behavior. While some limited rubber cavitation was visible for both resins, crazes—and consequently matrix shearing—could not develop to a large extent whether in the PP or in the /1-PP matrix (although these structures were somewhat more pronounced in the latter case). Therefore, a question remains open was the rubber cavitation sufficient to boost the development of dissipative mechanisms in these resins ... 

Since then, TEM has been used to study dislocation microstructures in a wide range of naturally and experimentally deformed minerals and rocks. In general, the aim of the experimental studies is to determine the deformation mechanisms by relating the evolution of the observed mi-crostructures to the macroscopic deformational behavior observed under varying conditions of temperature, confining pressure, chemical environment, strain-rate, stress, and total strain, and then to use this knowledge to interpret the microstructures observed in naturally deformed specimens and hence to determine their deformational history. 

Because the microcrack-ladders are observed in the preheat and in the peak-loaded specimens as well as in the weakly deformed central regions of the deformed specimens, they are likely to contain much information about the initial stages of deformation. Such information is completely... 

Dislocations and faults in deformed monoclinic a-spodumene and diopside. Van Duysen and Doukhan (1984) examined the dislocations in both naturally and experimentally deformed single crystals of a-spodumene. The naturally deformed specimens were characterized by a heterogeneous distribution of dislocations (p 10 cm ). The dislocations are not dissociated and most have b = [001] and lie in the crystallo-graphically equivalent planes (110) and (iTO). Other dislocations, probably with b = [110] and [TlO], were also observed and commonly interact to form irregular networks according to the reaction... 

Initial moduli at room temperature were obtained with an Instron Model 4206 at a strain rate of 2/min ASTM D638 type V specimens were used. The Instron was also used in the creep experiments, in which deformation under a 1 NPa tensile load was continuously monitored for 10 sec, followed by measurement of the recovered length 48 h after load removal. Strain dependence of the elastic modulus was determined by deforming specimens to successively larger tensile strains and, at each strain level, measuring the stress after relaxation after it had become invariant for 30 min. 

The plastic strains are measured by means of point marking method. The markings with 1 mm interval in a direction of tensile axis were made by a micro-vickers hardness tester before tensile tests. Tensile tests were conducted at room temperature at a cross-head rate of 0.5 mm/min with an Instron-type testing machine. After the tensile deformation, the relative displacements between markings were measured under a precision machinery microscope, and the corresponding local strains in the direction of tensile axis were calculated. Then deformed specimens were cut into pieces of 1 mm width by a low speed cutter perpendicular to the tensile axis. The saturation magnetization of each piece was measured by magnetic balance at room temperature. 

In inhomogeneously deformed specimens, the x-axis is taken m a direction of tensile axis as shown in Fig. 6. When the specimens are separated into 50 elements along tensile axis, the cross-sectional area a(x) is given as a function ofx. 

The stress-strain relationships of elastomeric (rubbery) networks at low extension (or draw) ratios (k, which is the length of the deformed specimen divided by the length of the initial undeformed specimen) can be described in terms of Equation 11.37 [29], which is the simplest possible constitutive equation for the deformation of an isotropic incompressible medium. 

Figure 12-17. The observed dependence of degree of contact on load for the rough surface of a constrained deformable specimen against a rigid smooth flat, compared with the relations obtained by (a) assuming noninteraction of asperities (broken line) and (b) the asperity interaction model (solid line). Data by Pullen and Williamson [14].

The ASBs in deformed specimens normally appear as bands with altered microstructure running along directions of maximum resolved shear stress. These bands are seen as distinct, because they are surrounded by larger regions of unaltered nucrostructure. Note that no such bands of altered nucrostructure were observed in the stir zones of the welds examined here. The lack of clear evidence for ASBs in the stir zone during FSW of Ti-6A1-4V may be explained by one or more of the following ... 

Fis 14 4 (3) Comparison of flow curves in as-rolled and as-friction stir processed conditions, (b) Variation of flow stress with tem-" perature at a strain rate of lO- s-t and strain of 0.1. (c) Observation of exceptional ductility over a wide range of temperatures, (d) Photographs of deformed specimens show high uniform elongation, characteristic of superplastic flow. 

Spending elastic constants (often referred to as Frank constants) are K22 and A 33, respectively. The free-energy per unit volume of a deformed specimen relative to the undeformed one is given by [33, 34]. 

Several CPNCs were tested by Sammut [2007], who in addition to RER and RME (equipped with optical interferometry for simultaneous measuring of the width and thickness of deformed specimen, thus the true strain) also used the... 

Figure 8.12 Original and superplastically deformed silicon nitride specimens and their microstructures. In the deformed specimen, manyofthe fibrous grains are aligned alongthe...

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