Nominalizations

At nominal body forces the same compressive stress of 100 -110 Mpa was calculated in all directions in the middle of the head of the examined bolts... 

Fig. 7 shows the torque necessary to obtain the specified body force under construction conditions and in tbe state when removed from the bridge. It can well be seen that the change of the friction coefficient causes a very big scattering, and the necessary torque is much bigger than specified. The distribution of the results of a measurement performed on 1,127 bolts is presented in Figure 8. An average of 80% of nominal body force was found by the new method. The traditional method found the nuts could be swivelled much further than specified on 42 bolts, these bolts were found to have 40 - 60 % body force by the new method. 

Calibration procedure bases on rope specimens and corresponds to the Standard Pratice ASTM 1574. It takes a piece of the rope under test having a nominal metallic cross-section area (LMA=0) to set zero point of the instrument. Rope section with the LMA value known is used to set the second point of LMA calibration charactiristics. It is possible to use the air point calibration when there is no rope in a magnetic head (LMA=100%). 

Of course, under the same operating conditions, the higher the thickness the lower the stress level. Further tests were carried out to map the surface thickness distribution using an ultrasonic precision thickness gauge. It was so verified a deviation of the thickness up to 10% of the nominal value. 

After this calibration step (the effective absorption coefficient is determined from a known wall thickness change and the corresponding variation of the optical film density) the evaluation of local wall thickness changes Aw (corresponding to De,o) from the nominal wall thickness w o , (corresponding to Dnom) can be done according to ... 

Note that this relationship is in conPadiction to the well known equation for the calculation of the thickness resolving power given by Halmshaw in 111. The relationship in 111 requires explicit knowledge about built-up factors for scatter correction and the film contrast factory (depending on D) and is only valid for very small wall thickness changes compared to the nominal wall thickness. 

Measure Wall Thickness This window is used for the dialog to calibrate the algorithm aceording formula (3) and for point wise measurements after calibration. The row Ideal indicates the nominal wall thickness used, IQI indicates the wall thickness values used for calibration and the detected optical density. Local can be used for noise reduction and compensation of geometric effects. 

Fig.3 User interfaee for wall thickness evaluation based on density variations on a step wedge, the nominal wall thickness was set to 15 mm...

In fig, 4 local corrosion by erosion is shown in a pipe with a bore of 100 mm behind a welding. In this case only the nominal wall thickness of the pipe is known (6.3 mm). To calibrate the obtained density changes into wall thickness changes a step wedge exposure with a nominal wall thickness of 13 mm (double wall penetration in the pipe exposure) and the same source / film system combination was used. From this a pcff = 1-30 1/cm can be expected which is used for the wall thickness estimation of the pipe image according to equation (4). 

The nominal visibility level VL om was determined from the viewing conditions of indications as decribed in 2.2 (Fig. 1). Assuming that this VL o , is equivalent to the VL with nominal inspection parameters, for the worst case of any inspection parameter the relative reduction R of the visibility of the indications was determined and summarized to the overall visibility level VLmin. Naturally the following data may be varied and/or completed. 

The nominal inclination of the surface against the horizontal was 15°. Experiments indicate a relatively constant contrast, because Li and Ls decreasing proprtionally with increasing inclination. RI = -0.1 The magnetic particle content was reduced from 0.5 g/l to 0.25 g/1 This reduction seems realistic resulting in RP = -0.1... 

Assuming C = 1.0 (Indication luminance a factor 2 higher than the background) we get the nominal values from Fig. 1 ... 

Composite transducers will replace conventional transducers in applications where the improvement of test sensitivity, signal to noise ratio and axial resolution are mandatory. It must nevertheless also be noted in connection with the broadband feature that though composite probes have a specified nominal frequency, the echo signals allow no echo amplitude... 

In several generating banks inspected, a number of tubes have been found with eccentricity exceeding 1,0 mm and in one extreme case 2,0 mm, or 40 % of the nominal wall thickness was noted. A conceptual diagram of tire cross section of a concentric tube and a simulated plot of the wall thickness scan is presented in figure 3. The scan presented in figure 2 is a relatively concentric tube less than 0,2 mm of wall variation. 

The wastage is 2,6 mm below the nominal wall thickness of 4.2 mm. On the rare occasion this type of wastage may also penetrate into the tube sheet for up to 6 mm. 

Wastage will also occur on that part of an eccentric tube that represents the nominal thickness of the tube. 

For existing ships the only NDE method nominated by classification for the detection of fatigue cracks is close-up visual inspection - although all Surveyors have the option of requesting additional NDE when warranted. The sensitivity of visual inspection is influenced by the degree of surface preparation and the level of lighting at the inspected surface - which may not always meet the level of 500 lux nominated by some NDE specifications. 

Under this programme 25% of the stiffeners and adjacent plate material in bulk carriers will be examined with thickness measurements being taken at upper, lower and mid points in both face and web plates of the stiffeners and associated end brackets. The extent of thickness measurement applied to transverse bulkheads has also been increased. In addition. Classification has revised the scantling requirements for new buildings to nominate thicker material in the bottom structure and at the transverse watertight bulkheads of the No 1 cargo holds. 

The results of corrosion surveys are received by the Surveyor in an agreed format using Forms TMl - TM8, preferably with the LR software freely issued to the approved firms. The report will highlight any areas where corrosion has gone beyond the permitted maximum diminution, which may be as low as 15% of the nominal thickness for a single item, and will also identify areas of "substantial corrosion T.e., any in excess of 75% of the permitted maximum. Corrosion in excess of that permitted means that the item has to be replaced. Any areas of corrosion deemed to be "substantial" are recorded for annual inspection. The Surveyor will review the completed report for verification and confirmation of the completeness of the thickness survey. 

Figure C2.3.5. Mesoscale stmctures deriving from surfactants nominally exhibiting shapes corresponding to various packing parameter ranges.

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