Primary stress general

Primary general stress. These stresses act over a full cross section of the vessel. They are produced by mechanical loads (load induced) and are the most hazardous of all types of stress. The basic characteristic of a primary stress is that it... 

Column 4 describes the failure modes of the component. One row is typically used for each component failure mode. Examples of component failure modes include fail short, fail open, drift, stuck at one, stuck at zero, etc., for electronic components. Mechanical switch failure modes might include stuck open, stuck closed, contact weld, ground short, etc. Column 5 describes the cause of the failure mode of column four. Generally this is used to list the primary "stress" causing the failure. For example, heat, chemical corrosion, dust, electrical overload, RFI, human operational error, etc. 

Start-up and load variations in LMR cause sodium level variations in the hot plenum which load shells emerging in the free level area. Shell loadings are mainly due to the axial thermal gradient, since primary stress loading are generally low or insignificant, the same for wall thermal gradient. 

This hypothetical problem serves to illustrate how categories and types of loadings are related to the stresses they produce. The stresses which are required for equilibrium of the vessel are primary stresses. The stresses due to pressure and wind are primary general membrane stresses since even if yielding occurred, redistribution of stresses would not be possible. These stresses should be limited to the Code allowable stress values, where increases for occasional loading may be allowed for certain sections of the Code. 

On the other hand, the stresses from the inward radial load could be either a primary stress or secondary stress. It is a primary stress if it is produced from an unrelenting load or a secondary stress if produced by a relenting load. A general primary membrane stress will not redistribute upon yielding, whereas a primary local membrane stress will, and for a secondary stress the load will relax once slight deformation occurs. 

Primary general membrane stress, This stress is the average primary stress across a solid section, is produced hy pressure or mechanical loads, and is remote from discontinuities such as head-shell intersections, cone-cylinder intersections, nozzles, and supports. Examples are ... 

The bending stresses associated with a local loading are almost always classified as secondary stresses. Therefore, the membrane stresses from a WRC-107-type analysis must be broken out separately and combined with general primary stresses due to internal pressure, for example. 

Stresses are generally characterized as (a) primary stress, (b) secondary stress, or (c) peak stress. In the following discussion, the primary stresses will be denoted by P, the secondary stress by Q and the peak stress by F. These nomenclatures also apply to the ASME Boiler and Pressure Vessel Code. We will now define each of the three categories of stress. 

In extensional flow, the diagonal components of are non-zero (i.e. T,y = 0 for i j). In the case of uniaxial extension, Th is the primary stress that can be measured, while T22 and T33 are generally equal to the pressiure of the environment. Thus, the uniaxial extensional viscosity rj is defined by. 

Whereas service related primary stresses and secondary stresses for RPVIs during normal operation are generally lower than weld residual stresses. 

Primary stresses, including general primary membrane stress, local primary membrane stress, and primary bending stress Secondary stresses Peak stresses... 

Material parameters defined by Equations (1.11) and (1.12) arise from anisotropy (i.e. direction dependency) of the microstructure of long-chain polymers subjected to liigh shear deformations. Generalized Newtonian constitutive equations cannot predict any normal stress acting along the direction perpendicular to the shearing surface in a viscometric flow. Thus the primary and secondary normal stress coefficients are only used in conjunction with viscoelastic constitutive models. 

Secondary bonds are considerably weaker than the primary covalent bonds. When a linear or branched polymer is heated, the dissociation energies of the secondary bonds are exceeded long before the primary covalent bonds are broken, freeing up the individual chains to flow under stress. When the material is cooled, the secondary bonds reform. Thus, linear and branched polymers are generally thermoplastic. On the other hand, cross-links contain primary covalent bonds like those that bond the atoms in the main chains. When a cross-linked polymer is heated sufficiently, these primary covalent bonds fail randomly, and the material degrades. Therefore, cross-linked polymers are thermosets. There are a few exceptions such as cellulose and polyacrylonitrile. Though linear, these polymers are not thermoplastic because the extensive secondary bonds make up for in quantity what they lack in quahty. 

For the deformation of NiAl in a soft orientation our calculations give by far the lowest Peierls barriers for the (100) 011 glide system. This glide system is also found in many experimental observations and generally accepted as the primary slip system in NiAl [18], Compared to previous atomistic modelling [6], we obtain Peierls stresses which are markedly lower. The calculated Peierls stresses (see table 1) are in the range of 40-150 MPa which is clearly at the lower end of the experimental low temperature deformation data [18]. This may either be attributed to an insufficiency of the interaction model used here or one may speculate that the low temperature deformation of NiAl is not limited by the Peierls stresses but by the interaction of the dislocations with other obstacles (possibly point defects and impurities). 

Creep rupture. Creep-rupture data are obtained in the same way as creep data except that higher stresses are used and the time is measured to failure (Figs. 2-28 and 29). The strains are sometimes recorded, but this is not necessary for creep rupture. The results are generally plotted as the log stress versus log time to failure (110). In creep-rupture tests it is the material s behavior just prior to the rupture that is of primary interest. In these tests a number of samples are subjected to different levels of constant stress, with the time to failure being determined for each stress level. General technical literature and product data sheets seldom provide a complete description of a material s behavior prior to rupture. It should include the development of any crazing and stress whitening, its strain-time... 

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