Ultrasonic testing

Ultrasonic testing (UT) uses mechanical waves to test objects for their quality. The ultrasound wave is generated by a mechanical vibration from a transducer that converts an electrical signal into mechanical motion and vice versa. By inputting a short pulse of electrical energy or a tone burst to the transducer, a pressure pulse will be 

In practice, ultrasound attenuation is measured in decibel (dB) units, and hence UT attenuation in dB = 201ogjo Aq/A) (15.4) 

A change of signal strength by a factor of 2 is 6 dB and by a factor of 10 is 20 dB. The attenuation of the ultrasound depends on frequency for example, at 5 MHz in a composite laminate, the attenuation could be in the range of 1.5—2dB/mm, whereas at 1 MHz the values could be half of that. The values are subject to the specifics of the fibers, resin, fiber-to-resin ratio, ply type, and layup. They are also subject to the specifics of the ultrasonic inspection equipment. Because consolidation is compromised by porosity, the attenuation will increase. The measurement of porosity level by ultrasonic attenuation is used for acceptance of the composite product. Calibration curves must be developed for the specific equipment, and the level of dB loss as a function of porosity for each thickness of composite established. A typical criterion is that less than 2% porosity is acceptable for manufacturing processes. Greater than 4% porosity can result in a significant knockdown in performance. 

The detection of features in composite laminate, such as delamination or inclusions, is a function of the transmission or reflection of the ultrasound across the material. 

This is dependent on the acoustic impedance difference between the materials at the feature interface. The acoustic impedance Z is defined as 

To quantify the results a combination of the signal amplitude of the interfacial echo (IE) in a C-scan, expressed through a colour code, and the adhesion strength obtained destructively by an ASTM C633-13 (2013) tensile test can be used. Echo-impulse techniques with an auxiliary reflector, for example by using water as an immersion medium allow measuring reliably the adhesion of very thin coatings 

To obtain the most efficient coupling, it is necessary to immerse in a water bath, but this is not always practical and jet-probes have been developed where water is propelled in laminar flow. Alternatively, hand held probes can be used with a grease coupling medium. 

To examine a laminate sheet, it is most convenient to measure the attenuation of the ultrasonic beam passing through it and there are three techniques which can be used  

Use a single probe positioning a glass plate on the other side to reflect the beam (pulse-echo) 

More conveniently, use the back surface pulse echo 

There are three ways to undertake these ultrasonic scans termed A-, B- and C- scans. 

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The ultrasonic testing of anisotropic austenitic steel welds is a commonly used method in nondestructive testing. Nevertheless, it is often a problem to analyze the received signals in a satisfactory way. Computer simulation of ultrasonics has turned out to be a very helpful tool to gather information and to improve the physical understanding of complicated wave phenomena inside the samples. 

In this paper, 2D simulations of the ultrasonic testing of different types of (transversely isotropic) austenitic V-butt welds are presented they have been obtained with an EFIT-code developed by Marklein [5]. 

Figure 1 shows the ultrasonic testing configuration used for detecting OSD. The ultrasonic focused probe is placed at an angle (18.9°) such that OSD are insonified by mode converted 45° shear waves. 

Nondestructive testing techniques for welded joints usually include visual, radiographic, magnetic particle, liquid penetrant, and ultrasonic testing methods. Of interest in this paper is the radiographic testing (RT) technique. 

Signal Processing Algorithms in Mechanised Ultrasonic Testing. 

Figure I represents a two-dimensional damage distribution of an impact in a 0/90° CFRP laminate of 3 mm thickness. Unlike in ultrasonic testing, which is usually the standard method for this problem, there is no shadowing effect on the successive layers by delamination echos. With the method of X-ray refraction the exact concentration of debonded fibers can be calculated for each position averaged over the wall thickness. Additionally the refraction allows the selection of the fiber orientation. The presented X-ray refraction topograph detects selectively debonded fibers of the 90° direction.

Ultrasonic Testing of Concrete with Fast Imaging Pulse-Echo-Technique. 

The second example concerns a thickness measurement problem. Normally this is an easy task for ultrasonic testing However,... 

Manual ultrasonic testing offers the advantages of low equipment cost combined with the flexibility of the human operator to provide good access and complex scanning capability. However, a total reliance on the capabilities of the ultrasonic technician to visualise the physical situation leads to a number of drawbacks, including lack of accuracy and consistency of defect size and location measurements, lack of verification that the required scan coverage has been fully achieved, and lack of consistency in flaw classification. A further disadvantage is that the ultrasonic data is not permanently recorded there is therefore no opportunity for the data to be re-examined at a later date if required. 

The new ultrasonic test system ISONIC minimizes the influence of human factors and allows even higher reliability compared with most of the automatic scanners. 

The new test system was developed in order to largely eliminate the human factors for manual ultrasonic testing as described above. The system consists of three components ... 

The ultrasonic instrument will be set up according to the test specification in the common way. Connection of the instrument to the ISONIC extends the flaw detector performance instrument to a reliable ultrasonic testing system which provides full documentation of the scan. 

Computerised Ultrasonic Testing of Constructions which are Past their Service Life, Based on P-SCAN System. 

A Technique of Ultrasonic Testing without Dead Zone for Coarse-Grained TC4 Extrusion Pipe. - The Development of Single Crystal Creeping Wave Prohe. 

KEYWORDS ultrasonic testing coares grain pipe single crystal creeping wave probe... 

Because these pipes are key components used for airplanes, their ultrasonic testing quality must be guranteed. Therefore, the author has conducted studies about the flaw detection methods for coarse-grained TC4P extrusion pipes. 

In this paper, the following aspects have been studied (A) Flaw detection can be made directly on the surface of the pipes, (B) The defects within the range of wall thickness can be tested out, that is to say, the ultrasonic testing without dead zone for the pipe wall can be realized and (C) Testing the defects of FBH as our testing. Objects, we may make the testing... 

Up to now the Reference Block Method and the DGS-Method are world wide the most important techniques for evaluating defect signals in manual Ultrasonic Testing. Even today, individual national standards refer to either one of these two echo evaluation techniques. However, both reflected echo signals from natural defects are compared with an echo from a known reference reflector at the same distance. The result of the evaluation is either... 

With the reference block method the distance law of a model reflector is established experimentally prior to each ultrasonic test. The reference reflectors, mostly bore holes, are drilled into the reference block at different distances, e.g. ASME block. Prior to the test, the reference reflectors are scanned, and their maximised echo amplitudes are marked on the screen of the flaw detector. Finally all amplitude points are connected by a curve. This Distance Amplitude Curve (DAC) serves as the registration level and exactly shows the amplitude-over-distance behaviour" of the reference reflector for the probe in use. Also the individual characteristics of the material are automatically considered. However, this curve may only be applied for defect evaluation, in case the reference block and the test object are made of the same material and have undergone the same heat treatment. As with the DGS-Method, the value of any defect evaluation does not consider the shape and orientation of the defect. The reference block method is safe and easy to apply, and the operator need not to have a deep understanding about the theory of distance laws. 

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.). 

Defect Evaluation in Diffusion Bonding Interface of Dissimilar Metals Using Ultrasonic Testing Method. 

This study detects the defect of the void and the exfoliation in the solid phase diffusion bonding interface of ductile cast iron and stainless steel with a nickel insert metal using ultrasonic testing method, and examine the influence of mutual interference of the reflectional wave both the defect and the interface. 

Therefore, the ultrasonic testing method in the diffusion joint of the dissimiler materials shall considered the influence of the interference with the reflective wave. 

Evaluation of Bonding Process in Diffusion Bonding Joints of Dissimilar Metals using Ultrasonic Testing Method. 

This study was in real time measured that the reflective echo height of the bonding interface in the solid phase diffused bonding process of carbon steel and titanium using ultrasonic testing method. As a result, the following were made discernment. 

The HILL-SCAN 30XX boards can be used in different PCs. Desktop- and tower-PCs as well suited for laboratory uses. For in-field inspections rugged notebooks and portable PCs are advantageous. A typical portable system is shown in Fig. 2 (USPC 3010), used in MUSE (Mobile Ultrasonic Equipment). This portable PC not only contains the boards for ultrasonic testing but also a controller with power supply for stepper motors, so that a manipulator can be connected directly. The MUSE system is enlarged with a water circulation system which enables a local immersion technique" for in-field inspections. A typical result is shown in Fig. 3, which presents a D-scan of a CFRP- component in RTM-techniques. The defect area caused by an impact is clearly indicated. The manipulator is described in [3]. 

MAPPscan - Acoustic Positioning system for Manual Ultrasonic Testing of Pipes and Components. 

MAPPscan is a manual ultrasonic testing system connected to an acoustic positioning system.. The system is developed as a consequence of the increased radiation doses in nuclear plants The system has the same flexibility as manual scanning with the same accuracy and the possibilties to collect, store and evaluate the UT data as with mechanised Ultrasonic systems The positioning system is based on spatial acoustic triangulation and have an accuracy of better than 1.0 mm within its recommended range. 

Another advantage with the system is that the quality of the scanning, in terms of the angle towards the weld and track partition is increased compared to manual ultrasonic testing due to the fact that the scanning technician is able to concentrate on the object rather than on the oscilloscope while scanning. 

Prokhorenko P.P., Baev A.R., Grintsevich E.M. Physical Principles and Application of Magnetic Fluids to Ultrasonic Testing -. Journal of Magnetism and Magnetic Materials. -... 

Installation for Ultrasonic Testing AKV-S is designed for testing of diesel motors pistons. Particularly, this device identifies the areas with cracks and lowered adhesion on interfacial boundary between niresist ring and base material. 

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