Stress orientation

Basically, with the higher pressures it is possible to develop tighter dimensional tolerances with higher mechanical performance, but there is also a tendency to develop undesirable stresses (orientations) if the processes... 

Figure 1.146, Stre.ss trajectory map.s of southern Northeast Honshu in the late Cenozoic period, after Tsunakawa and Takeuchi (1986) with a slight addition. oh, . trajectory is drawn by smoothing the inferred stress orientations from the selected dike-swarms with K-Ar dates. Selected major faults with age estimation are also shown for indicating types of stress fields. T Extensional stress field, where ay > a 2>cth , and normal or gravity faulting is preferable. P Compre.ssional, oh > ay, reverse or thrust faulting...

Figure 1.147. Jackson s curve and arc stress reorientations. Apparent swing motion of Pacific Plate (Jackson et al., 1975) and regional stress orientation at the Northeast Honshu convergent margin are illustrated in order to show their synchronous relationship. Dashed line represents the average trend of the Hawaiian volcanic chain. Pacific plate moves along the direction with fluctuation in reference to Hawaii Hot Spot. Vertically shaded parts of the graph indicate the climax phases of clockwise episodes . Lower part of the figure shows the phases and reversals in orientation of tectonic stress fields on the inner zone of Northeast Honshu Arc (Takeuchi, 1987).

Nakamura, K. (1977) Volcanoes as possible indicator of tectonic stress orientation — Principle and proposal. J. Volcano Geotherm. Res., 2, 1-16. 

A non-electrochemical technique which has been employed to alter the physical characteristics of a number of polymers is that of stress orientation [26, 27], in which the material is stressed whilst being converted to the desired form. This has the effect of aligning the polymer chains and increasing the degree of order in the material, and is obviously most applicable to materials which can be produced via a precursor polymer. With Durham polyacetylene (Section 4.2.1) increases in length in excess of a factor of twenty have been achieved, with concomitant increases in order, as shown by X-ray diffraction and by measurements of the anisotropy of the electrical conductivity perpendicular and parallel to the stretch direction. 

The reorientation of the B—H complex at 100 K complicates the analysis of the stress splitting data. The ratios of the intensities of the stress split components were extrapolated to zero stress to determine the site degeneracies for each stress orientation and hence to deduce the symmetry of the complex (Herrero and Stutzmann, 1988b). A unique configuration could not be found to fit the data for all stress directions it was suggested that the configuration of the complex must depend upon the applied stress. For the [110] stress direction it was proposed that the H is displaced from the trigonal axis in the direction away from the C site, while for [100] stress the H is supposed to be displaced toward the C site. 

Fig. 24. The H stretching band for the B—H complex measured at 10 K subsequent to a prestressing treatment with the stress orientation shown. A stress of 30 kg/mm2 was applied at room temperature and maintained while the sample was cooled to 10 K. The spectra were then recorded at 0 stress. The dashed spectra shown in (a) were recorded for an unstressed sample. [Reprinted with permission from the American Physical Society, Stavola, M., Bergman, K., Pearton, S.J., and Lopata, J. (1988). Phys. Rev. Lett. 61, 2786.]... 

FIGURE 2.23 Idealized structure illustrating crystalline (ordered) and amorphous (nonordered) regions of lightly branched polyethylene (PE) chains for a prestressed and stressed orientation. 

Instead of checking the second stress-optical relation, viz. eq. (1.6), Philippoff preferred to use eq. (1.3), assuming % = %. That this assumption is justified, can be seen in the same Fig. 1.4, In this figure also the extinction angle is plotted against the shear stress. Orientation angles calculated with the aid of eq. (1.3), fit rather well on the extinction angle curve. The normal stress difference (pn — p22) has been measured in the way explained in the previous section. Similar results were published later by the same author for solution of carboxy methyl celluose in water (33) and for S 111 in Aroclor (34) a chlorinated biphenyl. 

In crystalline polymers the relations between stress, orientation and birefringence are much more complicated than in amorphous materials. 

Stress-oriented hydrogen-induced cracking (SOHIC). 

Figure 7.84 Stress-oriented hydrogen-induced cracking in linepipe (x 50) (Courtesy of Malcolm Hay)...

W. Bruckhoff, O. Geier, K. Hofbauer, G. Schmitt, D. Steinmetz. Rupture of a Sour Gas Line Due to Stress Oriented Hydrogen Induced Cracking - Failure Analyses, Experimental Results and Corrosion Prevention. NACE Corrosion/85, Paper 389, Boston, USA, 1985-03-25/29. 

Carr, W. J., 1974, Summary of tectonic and structural evidence for stress orientation at the Nevada Test Site, U.S, Geol Survey Open-File Report 74-176. 

It is remarkable that several predictions about linear viscoelastic properties in the terminal region can be obtained without special assumptions about the stress- orientation relationship. Thus, for a simple shear strain y which is small enough to evoke only a linear response, the shear stress after the rapid equilibratin process can be written... 

A.N. Galybin and Sh.A. Mukhamediev, Determination of elastic stresses from discrete data on stress orientations, IJSS, 41 (18-19), 2004, 5125-5142. 

Sh.A. Mukhamediev, A.N. Galybin and B.H.G. Brady, Determination of stress fields in elastic lithosphere by methods based on stress orientations, INT J ROCK MECH MIN,43 (1), 2006, 66-88. 

Yale, D.P., Rodriguez, J.M. and Mercer, T.B. 1994. In-situ stress orientation and the effects of local structure - Scott Field, North Sea. EUROCK 94, Balkema, Rotterdam. 

Macroscopic and Intergranular StrainjStress. Similar to the case of texture we can call 8, g) = Oq, (P2) the strain/stress orientation distribution functions (SODF) (a,- is still a placeholder). In contrast to the texture case, the average of the SODF over all variables is not unity but is the macroscopic strain/stress ... 

Arguments for recent developments of the spherical harmonics approach for the analysis of the macroscopic strain and stress by diffraction were presented in Section 12.2.3. Resuming, the classical models describing the intergranular strains and stresses are too rough and in many cases cannot explain the strongly nonlinear dependence of the diffraction peak shift on sin even if the texture is accounted for. A possible solution to this problem is to renounce to any physical model to describe the crystallite interactions and to find the strain/ stress orientation distribution functions SODF by inverting the measured strain pole distributions ( h(y)). The SODF fully describe the strain and stress state of the sample. 

The diffraction pattern of CTAHF, shown In Figure 8, after drying (without stress). Orientation In the fiber Is clearly seen. 

Table 8.3. IRs of the site symmetry point groups of the sublevels of np donor states in silicon split by a uniaxial stress, deduced from the IRs of the valley group. The site symmetry group under stress is indicated close to the stress orientation. The magnitudes of the splitting, independent of the value of m, are given in Table 8.2 (after [2])...

Stress orientation m IRs of the valley group IRs of the Ta site group IRs of the new site group... 

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