Ultrasonic A-scan

AIR-1 and PS-4 are used on-site for recording of A-scan data during the on-site inspection. UltraSIM is used for initial ultrasonic simulation, scan path generation and robot simulation (together with the ROBCAD robot simulation software), online control and monitoring of the real AIR-1 robot and finally for 3D reconstruction of ultrasonic A-scan data. 

Finally, the standard draft provides a detailed model of the acquisition data, which intends to describe all the possible shapes which can be taken by NDE data OD (scalar or complex), ID (sampled - cf ultrasonics A-scans - or unsampled - ef ultrasonics time/amplitude data), 2D (images) or 3D (volumes). 

Figure 11 Schematic ultrasonic A-scan of a pulse-echo inspection.

A novel approach for suppression of grain noise in ultrasonic signals, based on noncoherent detector statistics and signal entropy, is presented. The performance of the technique is demonstrated using ultrasonic B-scans from samples with coarse material structure. 

Homogeneity of data. Homogeneous data will be uniform in structure and composition, usually possible to describe with a fixed number of parameters. Homogeneous data is encountered in simple NDT inspection, e.g. quality control in production. Inhomogeneous data will contain various combinations of indications from construction elements, defects and noise sources. An example of inhomogenous data are ultrasonic B-scan images as described in [Hopgood, 1993] or as encountered in the ultrasonic rail-inspection system described later in this paper. 

The data are transmitted from the front end processor to the computer in digital form over an ethemet link. The data consist of ultrasonic data, either raw RF A-scans or data processed by the digital signal processor in the PSP-4. In addition to the ultrasonic data, scanner coordinates are transmitted over the ethemet link. 

The scan mode display is divided into a number of windows, that display the data recorded from the active inspections. In addition, the A-scan data from the ultrasonic probes can be displayed in probe monitor windows, for monitoring the signal quality. Figure 7 shows the scan mode display for simultaneous recording of two P-scan inspections (displayed in the same presentation window) and a T-scan inspection together with 3 probe monitor windows. 

We are confident that any user of this combined evaluation technique, as well as the development of future test standards for manual ultrasonic testing will benefit from this result, because it allows a greater flexibility in the applicable method without loosing reliability. Often an expensive production of a reference block can be avoided and therefore testing costs are reduced. Since all calculations are performed by a PC, the operator can fully concentrate on his most important duty scanning the workpiece and observing the A-scan. Additional time will be saved for the test documentation, since all testing results are stored in the instrument s memory (the PC s hard drive) with full link to the Software World (Microsoft Word, Excel, etc.). 

The HILL-SCAN 30XX boards enable ultrasonic inspections from 50 kHz (concrete inspections) to 35 MHz (inspection of thin layers) with a signal to noise ratio up to 60 dB. The gain setting range of the receiver is 106 dB. High- and low pass filters in the receiver can be combined to band-passes, so that optimal A-scans are displayed. 

The PS-4 ultrasonic examination system provides many new features, which allows the operator to perform several inspections simultaneously. Both pulse-echo and time-of-flight-diffraction technique can be applied together with storage of digital A-scan data at the same time. 

Two types of ultrasonic systems are available that can be used for predictive maintenance structural and airborne. Both provide fast, accurate diagnosis of abnormal operation and leaks. Airborne ultrasonic detectors can be used in either a scanning or contact mode. As scanners, they are most often used to detect gas pressure leaks. Because these instruments are sensitive only to ultrasound, they are not limited to specific gases as are most other gas leak detectors. In addition, they are often used to locate various forms of vacuum leaks. 

Suhtnicion nickel powders luive been synthesized successfully from aqueous NiCh at various tempmatuTKi and times with ethanol-water solvent by using the conventional and ultrasonic chemical reduction method. The reductive condition was prepared by flie dissolution of hydrazine hydrate into basic solution. The samples synthesized in various conditions weae claractsiz by the m ins of an X-ray diffractometry (XRD), a scanning electron microscopy (SEM), a thermo-gravimetry (TG) and an X-ray photoelectron spectroscopy (XPS). It was found that the samples obtained by the ultrasonic method were more smoothly spherical in shape, smaller in size and narrower in particle size distribution, compared to the conventional one. 

Fig. 8.12. (a) X-ray radiograph and (b) ultrasonic C-scan image, showing edge delamination in the [ 30°/ 90 ]s laminate of T300 carbon 5208 epoxy matrix. system which has been subjected to axial tension. Reprinted from Kim (1989). with kind permission from FIsevier Science-NI.. Sara Burgerhart straat 25,... 

The ultrasonic C-scan technique is the most widely used nondestructive method of locating defects in the composite microstructure. The through transmission C-scan is easy to implement and a large composite panel can be scanned in a matter of minutes. The problem with this technique is that a C-scan cannot reveal the type of defect present. Hence, there is no way to determine if a flaw detected by the C-scan is due to incomplete contact of an interply interface or some other type of defect in the composite microstructure. 

Okawai, H., Tanaka, M., Chubachi, N., and Kushibiki, J. (1987). Non-contact simultaneous measurement of thickness and acoustic properties of biological tissue using focused wave in a scanning acoustic microscope. Proc 7th Symp. Ultrasonic Electronics, Kyoto. Jap. J. Appl. Phys. 26 (Suppl. 26-1), 52-4. [164]... 

Zieniuk, J. K. and Latuszek, A. (1986). Ultrasonic pin scanning microscope a new approach to ultrasonic microscopy. IEEE 1986 Ultrasonics Symposium, pp. 1037-9. IEEE, New York, [xi, 290, 291]... 

There was, however, one topic which was not included in the first edition, which has undergone substantial development in the intervening years. It could have been foreseen in 1986 a paper was presented at the IEEE Ultrasonics Symposium entitled Ultrasonic pin scanning microscope a new approach to ultrasonic microscopy (Zieniuk and Latuszek 1986,1987). With the advent of atomic force microscopy, it proved possible to combine the nanometre-scale spatial resolution of scanning probe microscopy with the sensitivity to mechanical properties of acoustic microscopy. The technique became known as ultrasonic force microscopy, and has been joined by cognate techniques such as atomic force acoustic microscopy, scanning local-acceleration microscopy, and heterodyne force microscopy. 

Fig. 4.2. Differential pulse voltEunmetric determination of purine Euid P5rrimidine bases guanine (2 X 10 M), adenine (3 X 10 M), thymine (3 X 10 M) and cytosine (3 X 10 M) in borate buffer (pH 10.02), (a) with ultrasonic pretreatment (power intensity, 72 W cm horn tip-electrode separation, 5 mm), (b) successive scan without ultrasonic pretreatment. Scan rate, 5 mV s amplitude, 50 mV. (Reproduced from Ref. [80] with permission from Elsevier.)...

The composite, metal substrate, and braze foils (two layers, -100 pm total thickness) were sliced into 2.54 cm x 1.25 cm x 0.25 cm pieces and ultrasonically cleaned in acetone for 15 min. The braze foil was sandwiched between metal and composite, and a normal pressure of 1.2-4.7 kPa (0.38-1.5 N) was applied to the assembly. The assembly was heated in a furnace to -15-20 °C above the braze liquidus under vacuum (10 torr), soaked for 5 min., and slowly cooled to room temperature. The brazed joints were prepared for metallography and examined with a Scanning Electron Microscope (SEM) coupled with energy dispersive x-ray spectroscope (EDS) on a JEOL-840 A unit. Microhardness scans were made with a Knoop micro-indenter on a Struers Duramin A-300 machine under a load of 200 g and loading time of 10 s. 

The resin content in both composites is about 37% by weight. The porosity of the composites was characterized by ultrasonic C-scans. The test specimens of no measurable porosity were used. The resin specimens and the composite laminates were cured in a hydraulic press at 250 F and 75 psl for one hour, and subsequently postcured at the same temperature in the absence of pressure for another two hours. Additional curing for up to 16 hours in the case of HX-205 and F-185 resins showed no measurable changes in dynamic mechanical properties. 

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