Structure discontinuity

With nondestructive ultrasonic test back and forth scanning of a specimen is accomplished with ultrasonics. This NDT can be used to find voids, delaminations, defects in fiber distribution, etc. In ultrasonic testing the sound waves from a high frequency ultrasonic transducer are beamed into a material. Discontinuities in the material interrupt the sound beam and reflect the energy back to the transducer, providing data that can be used to detect and characterize flaws. It can locate internal flaws or structural discontinuities by the use of high frequency reflection or attenuation (ultrasonic beam). 

The discontinuity of the interface leads to two contributions to the second order nonlinear polarizability, the electric dipole effect due to the structural discontinuity and the quadrupole type contribution arising from the large electric field gradient at the surface. Under the electric dipole approximation, the nonlinear susceptibility of the centrosymmetric bulk medium 2 is zero. If the higher order magnetic dipole... 

The Tyrrhenian Sea is an extensional basin developed behind the Apen-nine-Maghrebide collisional chain. It started to open at about 15 Ma and is still expanding at present. The rate of opening has been much stronger in the south than in the north. This has resulted in a triangular shape for the Tyrrhenian basin and produced a major lithospheric structural discontinu-... 

Due to the composite nature of boron fibers, complex internal stresses and defects such as voids and structural discontinuities result from the presence of a... 

The fats used in pastry and biscuit confectionery have different functions, which are determined by their rheological properties (plasticity and texture). In pastry, these principal functions are (1) an increase in the plasticity of the pastry (e.g., hard pastry with a low level of hydration) and (2) a break in the body of the pastry (i.e., the fat makes the gluten structure discontinuous, which gives the desired cmmbliness in, for instance, biscuits) (121). 

Fig. 7 (A) Carbon nanotube exposed at the breakage edge of a VGCF as (A) grown and (B) heat-treated at 3000 C. The sample is fractured by pulverization and the core diameter is 50 A. (B) These photos suggest a structural discontinuity between the nanotube core of the fiber and the CVD deposited carbon layers. The images show the strong mechanical properties of the nanotube core, which maintains its form after breakage of the periphery. (From Ref...

On many jobs it may be necessary to know if the grout to be pumped through a specific hole will reach ground surface or some structural discontinuity such as a tunnel face or wall. It may also be desirable to measure the flow rate for establishing gel times. Colored water may be pumped into the grout hole for this purpose. 

A more defective form of sp carbon fibers, carbon nanotubules (CNTbs), grown by pyrolytic deposition of carbon into anodized aluminum oxide (AAO) nanochannels, are also used as nanoelectrode arrays for electrochemical sensors. Small graphitic crystallites are deposited on the inner surface of the nanochannels. Since the crystallites do not extend very long (less than micrometers) and are structurally discontinued, the resistance is orders of magnitude higher than CNFs... 

A further restriction on secondary stresses is that they may not be closer to another gross structural discontinuity than a distance of 2.5VHmt. This restriction is to eliminate the additive effects of edge moments and forces. 

The part of the crust constituted from consolidated rocks is referred to as the bedrock. These rocks are also referred to as intact rocks. The physical properties of fresh (unweathered) rock depend on their constituent minerals and texture and the presence of structural discontinuities like fractures, joints and bedding. 

Table 14-1 shows a summary of some available statistics for both destructive events and nondestructive breaks, the latter include all the cases of fractures discovered in time or which could become destructive and all those minor fractures, probably not potentially destructive, that required intervention because of their size. The principal causes of the reported fractures are fatigue (mechanical, thermal or corrosion assisted) associated with pre-existing fabrication defects, generally corresponding to structural discontinuities such as appendages, penetrations, etc. 

Nucleation may occur spontaneously and homogeneously throughout the amorphous phase (most likely at low temperatures) or be seeded by foreign surfaces or structural discontinuities. The type and density of nucleation are likely to strongly influence the character of subsequent crystal growth. Above the critical size, nuclei become stable, permitting crystal growth to occur. 

A new creep-fatigue method, which is based on the concept of a general elastic follow-up model, is being developed. The elastic follow-up equations to predict strain magnification and creep relaxation for structural discontinuities are established. 

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