C-scan

A Scan at 7mm depth B Scan at 10mm depth C Scan at 13mm depth Fig. 11 Tomography scans of an internal shrinkage at different depths (A B C)... 

To evaluate the VIGRAL method, we scanned steel blocks with simulated flaws using a Flexilrak and a upi-50 instrument. This system allows for rapid and accurate acquisition of the desired data, including the A-scan, B-scan, and C-scan data, and serves to evaluate, offline, the V-scan image (Figure 8). 

In this paper, discontinuities in cylindrical specimens were studied by ultrasonic reflection tomography. The aim was threefold. First, to localize discontinuities from circular C-scan images. Second, to reconstruct quantitative cross-sectional images from circular B-scan profiles (i.e., reflection tomograms). Finally, to obtain three-dimensional information (i.e., discontinuity location, dimension and type) by stacking these reflection tomograms in multiple planes, in the third dimension. 

Some discontinuities may be identified by a conventional two-dimensional ultrasonic technique, from which the well-known C-scan image is the most popular. The C-scan technique is relatively easy to implement and the results from several NDE studies have been very encouraging [1]. In the case of cylindrical specimens, a circular C-scan image is convenient to show discontinuity information. The circular C-scan image shows the peak amplitude of a back-scattered pulse received in the circular array. The axial scan direction is shown as a function of transducer position in the circular array. The circular C-scan image serves also as an initial step for choosing circular B-scan profiles. The latter provides a mapping between distance to the discontinuity and transducer position in the circular array. 

Fig. 3. Circular C-scan image of A/Si-alloy cylinder showing six discontinuity types. Grey scale in [dB] of echo from discontinuity (gate 2).

Although the discontinuities may be seen clearly in the circular C-scan image, the image represents only a projection of discontinuities in a specific direction (i.e., a shadow of overlapping discontinuities). More information of the discontinuities according to location, dimension and type may be achieved by ultrasonic computed tomography (UCT) imaging. 

More recently, the circular array was proposed to assess the reflectivity of cylindrical specimens [3]. First, a circular C-scan image was obtained. The total scan time was about 25 min., which does not include a relatively time consuming alignment of the specimen. From the circular C-scan image, circular B-scan profiles were chosen in specific planes. The transducer was a focused high frequency transducer with a center frequency of 25 MHz of the transducer bandwidth. This frequency corresponds to a wavelength of 0.11 mm and 0.25 mm in the Plexiglas specimen and the AlSi-alloy, respectively. Additional experimental parameters are presented in Table 1. 

First, by circular array imaging A synthetic circular aperture array was used to obtain circular C-scan images. These images displayed the location of different discontinuity types, although only shadow images were obtained. 

The benefit of such a model is that better understanding of the wave propagation process may be gained. Also, it is possible to make controlled parameter studies in order to understand the influence of e.g. defect orientation, probe angle and frequency on the test results. Results may be presented as A-, B- or C-scans. 

The results are illustrated by figure 5 B-Scan, C-Scan and D-Scan representations show that there are two types of defects. On the left part of the weld, we remark a lack of fusion, while on the right part, we observe a nest of blow hole. 

The sizing defect method consists in selecting a defect in C-Scan image and framing it by an adjustable window in length and in width. Then, results are printed on the screen of the computer. 

Depending on the requirements, C-scan or a cascading display are used. These types of display facilitate tests for internal damage below the surface with low-frequency eddy currents in addition to high-frequency tests for surface cracks. 

In addition to the distortions caused by the probes, there were also distortions caused by filtering the signals within the eddy-current test instruments. To achieve the highest possible dynamics with the test instruments, high-pass filters with a high rate of rise, but also a long reverberation time were used. Thus, the recorded C-scan pictures sometimes shows strong echo effects. 

Additional assistance is provided by secondary modification options that allow among others for a depiction of the original signal, the reconstruction of the depiction of the impedance plane of the eddy-current signals or for modifications of phase, amplification or zero point virtually in real time. That way, once C-scan images have been recorded, they can now be evaluated as needed without having to repeat the test. 

A.K Jain M P Debuisson. Segmentation of X-ray and C-scan Images of Fiber Reinforced Composite Materials. Pattern Recognition, vol 25, N°.3, pp 257-270, 1992... 

Mephisto is devoted to predict the ultrasonic scans (A,B or C-scans) for a priori knowledge of the piece and the defects within. In the present version Mephisto only deals with homogeneous isotropic materials. The piece under test can be planar, cylindrical or have a more complex geometry. The defects can be either planar (one or several facets), or volumetric (spherical voids, side drilled holes, flat or round bottom holes). 

The principle of the acquisition system is to translate the probe into a tube (including hemispherical drilled holes) step by step, every 0.04 mm, after a forwards and backwards 360 rotation of the tube trigging every 0.2° angular step a 360° electronic scanning of tube with the 160 acoustic apertures. During the electronic scanning the tube is assumed to stay at the same place. The acquisition lasts about 30 minutes for a C-scan acquisition with a 14 kHz recurrence frequency. 

The analysis software rebuild a C-scan of every three reflectors and for every 160 acoustic apertures, and plots (see figure 5) ... 

Fig. 2 shows the CFRP-sandwich specimen and the transducer mounted on the scanner. Fig. 23 presents a C-scan of the specimen as first interesting result. Only the defects visible from the outside are indicated. The distance between transducer and specimen was smaller than the focal length, so that the angle of incidence at the edge of the sound beam converts the longitudinal waves to Rayleigh-waves in the specimen. These waves provide a very sharp image of the surface. This method opens the possibility for a non-contact acoustic microscope. 

For ultrasonic imaging systems (B-, C- and C-scans) single-shot measurements, fast data recordings, and fast data transfer must be performed. 

In the evaluation post processing software the stored UT-data can be presented as A-,B- and C-scans. The C-scan can be presented with Top-, End- and Side views. 

The software contains features such as TCG- compensation, information on probe rotation, compensations for object geometry and can provide a choice of A-, B- and C-scan images while scanning. 

Figure 5 Approximation results. Measured 18 MHz attenuation presented as a C-scan (left) and corresponding estimated attenuation based on PE-data (right)...

Fig. 17. Cyclic voltammogram of the water-soluble Rieske fragment from the bci complex of Paracoccus denitrificans (ISFpd) at the nitric acid modified glassy carbon electrode. Protein concentration, 1 mg/ml in 50 mM NaCl, 10 mM MOPS, 5 mM EPPS, pH 7.3 T, 25°C scan rate, 10 mV/s. The cathodic (reducing branch, 7 < 0) and anodic (oxidizing branch, 7 > 0) peak potentisds Emd the resulting midpoint potential are indicated. SHE, standEU d hydrogen electrode.

FIGURE 3.14 Transmission electron microscopic (TEM) pictures of (a) acrylic rubber (ACM)-silica hybrid prepared from 1 1 tetraethoxysilane (TEOS)/water (H2O) and (b) 1 2 TEOS/H2O mole ratios and (c) scanning electron microscopic (SEM) picture of ACM-silica hybrid composite synthesized from 1 6 TEOS/H2O mole ratio. The concentration of TEOS has been kept constant at 45 wt% and the samples have been gelled at room temperature. (From Bandyopadhyay, A., De Sarkar, M., and Bhowmick, A.K., J. Appl. Polym. Sci., 95, 1418, 2005. Courtesy of Wiley InterScience.)... 

Figure 11.13 Linear cyclic voltammograms of different carbon-supported catalysts recorded in an 02-saturated electrolyte (0.5 M H2SO4) (1) Pt/C catalyst (2) Pt/C catalyst in the presence of 1.0 M methanol (3) FePc/C catalyst (4) FePc/C catalyst in the presence of 1.0 M methanol (temperature 20 °C, scan rate 5 mV s rotation speed 2500 rev min ).

Crystal structure modification, in smart materials, 22 707 CS (riot control agent), 5 823-824 CS2, formation in the Claus furnace, 23 605. See also Carbon disulfide C-scan images, 17 424, 429 Cs isotopes, decay of, 21 303-304. 

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