Evaluation of Discontinuity Stresses

Nondestmctive evaluation, also termed nondestmctive testing or nondestmctive inspection, is extensively used in weld testing (14). Nondestmctive tests do no impair the serviceabiUty of the material or component under stress. The most widely used tests for evaluation of welds are Hquid penetrant, magnetic particle, ultrasonics, and radiography. Acoustic-emission tests are increasingly used. Nondestmctive tests detect and characterize, in terms of size, shape, and location, the various types of weld discontinuities that can occur. 

ABSTRACT Type of collapsibility of site is an important content in evaluation of loess collapsibility, the results calculated according to indoor test is often contradict with field test results. In order to solve the contradiction, the paper analyzes the factors that brings about difference in indoor and field test results based on the in-situ immersion test results in loess site completed in recent years, makes a study of the influence of discontinuous distribution of collapsible loess on collapse settlement, and presents the improved empirical formula for collapse settlement calculation under overburden pressure. The results show that indoor collapsibility test succeeds but impairs the correlation between factors such as loess property, stratum configuration, stress history, buried depth and settlement by immersion, during collapse settlement calculation, the correction of these influential factors shall be taken into consideration the standard used for judgment of loess as to whether it is collapsible may be properly heightened, in case of discontinuous distribution of collapsible loess, stress redistribution effect shall be taken into account. 

In Chapter 5 we showed how stresses are evaluated at different locations due to thermal and mechanical conditions. The magnitude of these stresses must be kept below a given allowable stress. This allowable stress is established in the ASME Code, VIII-2. The designer has to establish first whether the stress is at a local or a gross structural discontinuity, as defined in Fig. 8.1. Next the stress... 

The data in Fig. 12 actually collapse onto a master curve when the wall stress o is rescaled by temperature T and the nominal shear rate y is normalized by a WLF factor aT [29]. Thus Eq. (6) for the critical stress oc is supported by the data in Fig. 12, where V does not change with T. Another feature of the transition is that the amplitude of the flow discontinuity does not vary with T. In other words, the extrapolation length bc, which is evaluated according to Eq. (4a) at the transition, is a constant with respect to T. Thus for a given surface, bc is more than just a material property such as the melt viscosity r. It essentially depends only... 

Abstract The Ratio of Crack Opening Dependency (RCOD) was proposed as a new index to simultaneously evaluate the mechanical and hydraulic properties of cracked structure which contains many open cracks within. The RCOD is an index which is defined as the ratio of total amount of crack opening and the total deformation of cracked structure. The efficiency of RCOD as an index to evaluate the coupled problem was numerically analyzed by applying SCDDM (stress compensation-displacement discontinuity method) to the two dimensional multi crack model. It was shown that RCOD is an useful index which can directly evaluate the deformability and the permeability of the cracked structure without any parameters such as stresses or crack size. The possibility of application of RCOD to the field measurements was also discussed. 

Guideline 4 establishes the global locations for assessment of stresses, and states that the general primary membrane stress intensity, should be evaluated remote from a discontinuity whereas the primary membrane plus bending stress intensity, Pl + Pb, and primary plus secondary stress intensity, P + Q, should be evaluated at a discontinuity. 

The fatigue evaluation procedure is outlined in Chapter 8 in which it was mentioned how the alternating stress intensity is calculated for the general multiaxial stress state in a pressure vessel component. In addition, the effects of the so-called local structural discontinuities must be evaluated using stress concentration factors determined from theoretical, numerical or numerical techniques. These are referred to as the fatigue strength reduction factors, which generally should not exceed a value of 5. 

Another popular approach to evaluate the design of snap fits is to calculate their strain rather tlian their stress. Then compare this value with the allowable dynamic strain limits for the particular plastics. In designing the beams it is important to avoid having sharp comers or structural discontinuities that can cause stress risers. Tapered finger provides a more uniform stress distribution, which makes it advisable to use where possible. 

The function 0(Zy t) is evaluated in the lower half-plane so that as z approaches the real axis from within the material, 0(z, t) and 0(z, 0 approach 0 x, t) and 0 Xyt), respectively, which are the limits of this complex function from above and below. We see from (3.1.3b), that, at points on the real axis where the boundary stresses are zero, 0(z, t) has no discontinuity. This is the essential reason for the choice of (3.1.1), that it gives this property. For contact problems, it means that the discontinuities in 0(Zy t) are confined to the regions of contact. 

Polyethylene fibres have been evaluated using either short, dispersed fibres mixed with concrete at volumes up to about 4% [84], or a continuous network of fibrillated fibres (polyethylene in pulp form) to produce a composite with about 10% by volume of fibres. In pulp form, they are intended for use as asbestos replacement. The effect of short, discontinuous fibres (load-deflection of concrete is shown in Figure 10.20. At a volume content of 2% the fibres led to a marked post-cracking load-bearing capacity, while at 4% the maximum load in the post-cracking range exceeded the first crack stress. Thus, these fibres seem to be very effective for crack control. The fibrillated continuous polyethylene fibres appeared to be more effective than similar polypropylene fibres, probably because of the higher elastic modulus of the polyethylene. 

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