Cracks depth profiling

In order to provide measuring of cracks depth on complicated profile areas there is a special function in the device. The function makes it possible to perform measurements by studying on a samples with defects of the measured depth. 

The reason for these results is that the intensity of the leakage field and the RMS error used depend strongly on the parameter c and the crack width, and to a lesser extent on the depth profile of the crack. Also, the distribution of the density of the leakage field is measured over the centre of the crack and correspondingly changes more by varying of dj and dj rather than of d, dj, dj and d . 

Table 2. Relative errors made in the computation of the depth profile, the width, and the parameter c for the cracks from Fig.4a, Fig.4b, and Fig.4c and orientation angles C>=0°, =30 and 0=45°.

Mass Spectra. Whereas In the depth profiling mode the mass spectrometer Is used as a filter to obtain only one or a few masses for detection In the mass spectral mode the mass spectrometer Is used for the Identification and comparison of a wide range of masses. A survey mass spectrum Is often performed as the first step In any SIMS analysis and determines the presence of various elements and species on or near the surface and the relative Intensity of their respective signals. Further work would be required to relate signal Intensities to absolute or even relative concentrations. However the relative Intensities observed In Isotopic distributions for elements or In cracking patterns for molecules are useful In species Identification. 

Hot-pressed alumina-30 vol. % SiC particles composite was crack-healed, via a high-temperature oxidation treatment in air at 1573 K for 1 h. Then, the specimens passed through an electron beam curtain to homogeneously irradiate the crack-healed specimens. The total dose of irradiation was controlled by repeating the procedure. Depth profiles of hardness were measured using Vickers indentation with several indented loads. 

Figure 1 shows the Vickers hardness, of the hybrid surface reinforced specimen (D = 0.432 MGy) as a function of the penetration depth of the indenter, Dw, thereby giving a hardness depth profile. The closed and open triangles indicate the measured Vickers hardness for the hybrid surface reinforced specimens (D = 0.432 MGy) and crack-healed specimens, respectively. The points demonstrate the data for each measurement. Moreover, it was found that the measured hardness of the crack-healed specimens is independent of the penetration depth, and the indented force, P. ... 

A semicircular crack profile appears up to a load of 100 N. As the load increases beyond 200 N, the crack depth is approximately 20% less than the surface crack length. Large lateral cracks are clearly masking crack growth at greater depths. Other crack paths develop in relatively tough materials (for example, carbide metals such as WC-Co) at relatively low loads. This crack system, known as Palmqvist cracks , is shown in Fig. 150. The surface exhibits radial cracks that do not extend deep into the material. 

Figure 151. Dimensions of a Knoop crack. Crack profile a = crack depth, 2c = crack length, Zo = zone of deformation.

FIGURE 16. Sputter depth-profiles of both sides of propagated crack in a titanium adhesive system. The depth profiles allow the locus of failure to be fixed at or near the oxide-metal interface. (From Reference 86.)... 

The above AES results can be correlated to bond performance. Hsu et found that the DQSK adherends, containing the higher concentration of silicon, showed interfacial failure, while only cohesive failure was observed for CRS adherends. The chromium-to-iron ratios, determined from the depth-profile study of pretreated steel surfaces,correlated with the wedge test performance as shown in Figure 24, with minimal crack extension in samples with high Cr/Fe ratios. 

The constant B is a dimensionless modiflcation factor accounting for free surface effects and stress gradients along the crack depth as the compressive surface stress diminishes into the bulk. For the depths of compressed zones encountered in toughened glass, B is approximately unity, but it must be emphasized that this is not true for chemically tempered glass where the stress profile is very steep. ... 

The failure surfaces of the typical specimen selected are shown in Fig. 22. The T-stress in the specimen was 36 MPa and the crack trajectory alternated between the two interfaces, which can be observed in the side-view photograph. To further identify the locus of failure, both the XPS and Auger depth profile analyses were conducted on representative areas of both sides of the specimen as schematically... 

Figure 18 Theoretical and observed crack depth vs. operational time relationships for 28-inch-diameter schedule 80 type 304 stainless steel piping for two BWRs operating at different mean coolant conductivities. Note the bracketing of the maximum crack depth in the lower-puiity plant by the predicted curve that is based on the maximum residual stress profile and the predicted absence of observable cracking in the higher-purity plant (in 240 operating months).

Figure 25. Depth profiles through the oxide at two points on the crack shown in Fig. 24.

There is a range in observed crack depths adjacent to the horizontal welds due to the uncertainty in NDE measurements. It is also apparent that there is a range in predicted crack depths due to the uncertainty in defining the residual stress profile both around the circumference of the weld as well as through the 2 in. thickness of the shroud. 

A diagnosis of possible damage should be made before beginning repairs with other construction measures [48,49]. There should be a checklist [48] of the important corrosion parameters and the types of corrosion effects to be expected. Of special importance are investigations of the quality of the concrete (strength, type of cement, water/cement ratio, cement content), the depth of carbonization, concentration profile of chloride ions, moisture distribution, and the situation regarding cracks and displacements. The extent of corrosion attack is determined visually. Later the likelihood of corrosion can be assessed using the above data. 

Evidence for the two-phase model came from measurements of the gas concentration profile in a commercial catalytic cracking regenerator 40 ft in diameter with a 15-ft bed [8]. The exit gas had 1% O2, but samples drawn from different bed depths had only 0.1-0.4% O2. The bed samples also showed 12-14% CO2, compared to 10% CO2 in the exit gas. Although most of the gas flow was in the bubbles, the probe saw mainly dense-phase gas, where the conversion was higher than in the bubbles. Samples taken very rapidly showed wide fluctuations in oxygen content, since the probe was sometimes in a bubble and sometimes in the dense bed. 

Figure 19. Residual surface stress profiles expected from different ion exchange (IE) methods conventional extended (one-step) IE two-step IE and paste method (short IE treatment). Vertical dotted lines represent the depths of small and large surface crack. Data from [71]...

Irregularities of surfaces or profiles can be decomposed into form, waviness, and roughness according to the ratio of the distance between irregularities (deviations, waves, peaks, cracks, etc.) to their depth. A form error is the overall parameter describing the maximum of the local deviations of the real form of a line or surface from the nominal — geometrically ideal — feature. The parameter has to be evaluated according to the specification (see below). 

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