Showing papers on "Ultrasonic testing published in 2011"

Ultrasonic treatment device

Abstract: An ultrasonic treatment device (21) comprises an ultrasonic vibrator (28) which generates ultrasonic vibration, a vibration transmission section (29) which transmits the ultrasonic vibration generated by the ultrasonic vibrator (28), a treatment section (32) which is formed at the front end of the vibration transmission section (29) and transmits to living organism's tissue the ultrasonic vibration transmitted from the vibration transmission section (29), a grip member (33) which is provided so that the grip member (33) can be opened and closed relative to the treatment section (32), and a pad member (49) which is provided to the grip member (33) at a position facing the treatment section (32) and which makes contact with the treatment section (32) when the grip member (33) is in a closed state. The front end of the pad member (49) has a protrusion section (60) which, on the side thereof which faces the treatment section (32), protrudes toward the treatment section (32).

Automatic Defect Classification in Ultrasonic NDT Using Artificial Intelligence

Abstract: A methodology is developed to detect defects in NDT of materials using an Artificial Neural Network and signal processing technique. This technique is proposed to improve the sensibility of flaw detection and to classify defects in Ultrasonic testing. Wavelet transform is used to derive a feature vector which contains two-dimensional information on various types of defects. These vectors are then classified using an ANN trained with the back propagation algorithm. The inputs of the ANN are the features extracted from each ultrasonic oscillogram. Four different types of defect are considered namely porosity, lack of fusion, and tungsten inclusion and non defect. The training of the ANN uses supervised learning mechanism and therefore each input has the respective desired output. The available dataset is randomly split into a training subset (to update the weight values) and a validation subset. With the wavelet features and ANN, good classification at the rate of 94% is obtained. According to the results, the algorithms developed and applied to ultrasonic signals are highly reliable and precise for online quality monitoring.

High-temperature (>500°c) wall thickness monitoring using dry-coupled ultrasonic waveguide transducers

Abstract: Conventional ultrasonic transducers cannot withstand high temperatures for two main reasons: the piezoelectric elements within them depolarize, and differential thermal expansion of the different materials within a transducer causes them to fail. In this paper, the design of a high-temperature ultrasonic thickness gauge that bypasses these problems is described. The system uses a waveguide to isolate the vulnerable transducer and piezoelectric elements from the high-temperature measurement zone. Use of thin and long waveguides of rectangular cross section allows large temperature gradients to be sustained over short distances without the need for additional cooling equipment. The main problems that had to be addressed were the transmission and reception of ultrasonic waves into and from the testpiece that the waveguides are coupled to, and optimization of the wave propagation along the waveguide itself. It was found that anti-plane shear loading performs best at transmitting and receiving from the surface of a component that is to be inspected. Therefore, a nondispersive guided wave mode in large-aspect-ratio rectangular strips was employed to transmit the anti-plane shear loading from the transducer to the measurement zone. Different joining methods to attach the waveguides to the component were investigated and experiments showed that clamping the waveguides to the component surface gave the best results. The thickness of different plate samples was consistently measured to within less than 0.1 mm. Performance at high temperatures was tested in a furnace at 730°C for 4 weeks without signal degradation. Thicknesses in the range of 3 to 25 mm could be monitored using Hanning windowed tonebursts with 2 MHz center frequency.

Output Measurements for Medical Ultrasound

Abstract: Safety of diagnostic ultrasonic equipment and the relevance of acoustic output fundamentals of ultrasonic propagation overview of measurement techniques hydrophones ultrasonic power balances measurements on a specific acoustic pulse real-time scanning systems.

Application of Ultrasonic C-Scan Techniques for Tracing Defects in Laminated Composite Materials

Abstract: In this paper practical ultrasonic C-scan techniques for NDT of laminated composite materials are developed and applied, with an aim to trace specific artificial defects. Two types of materials are examined; an advanced carbon/epoxy system and a typical marine type glass/polyester system. Both were constructed with two manufacturing methods (Hand Lay-Up and Vacuum Infusion). Several artificial defects were embedded into the test plates, varying in shape, magnitude and through thickness position. Test plates were C-scanned using ULTRAPAC II ultrasonic system with ULTRAWIN software and typical examination techniques (layer to layer examination, full width examination, etc.) were used to determine and characterize defects. In addition, appropriate software tuning procedures and examination strategies were applied, which further developed and optimised tthe scanning procedure. These efforts resulted in effective C-scan images, allowing the determination of the position and even the shape of the defects in some cases. Finally, precise determination of specimens’ thickness was achieved.

Non-contact ultrasonic detection of angled surface defects

Abstract: Non-destructive testing is an important technique, and improvements are constantly needed. Surface defects in metals are not necessarily confined to orientations normal to the sample surface; however, much of the previous work investigating the interaction of ultrasonic surface waves with surface-breaking defects has assumed cracks inclined at 90° to the surface. This paper explores the interaction of Rayleigh waves with cracks which have a wide range of angles and depths relative to the surface, using a non-contact laser generation and detection system. Additional insight is acquired using a 3D model generated using finite element method software. A clear variation of the reflection and transmission coefficients with both crack angle and length is found, in both the out-of-plane and in-plane components. The 3D model is further used to understand the contributions of different wavemodes to B-Scans produced when scanning a sample, to enable understanding of the reflection and transmission behaviour, and help identify angled defects. Knowledge of these effects is essential to correctly gauge the severity of surface cracking.

Ultrasonic NDE Techniques for Impact Damage Inspection on CFRP Laminates

Abstract: This study investigates the different types of ultrasonic inspection, when applied to assess the impact damage in Carbon Fiber Reinforced Plastic CFRP laminates. The study surveys the two most used ultrasonic testing approaches first; namely the pulse-echo and the through-transmission modes. Then, the manuscript discusses and analyzes the enhanced ultrasonic testing methods that use the polar scattering, the thickness independent techniques, air-coupled, and the techniques based on the Ultrasonic Rayleigh and Lamb Waves. Additionally, presented study demonstrates some of these techniques to test a CFRP sample with embedded defects, along with the processing required for the acquired results such as the wavelet transformation.

Monitoring Corrosion in Oxide and Chloride Environments Using Ultrasonic Guided Waves

Abstract: Ultrasonic guided waves have been used for monitoring progression of rebar corrosion in concrete in chloride and oxide environments. The effect of rates of corrosion in the two environments on the ultrasonic signals is reported. Surface- and core-seeking guided wave modes were used to monitor beams undergoing accelerated impressed current corrosion in the presence (chloride corrosion) and absence of chlorides (oxide corrosion). Effective combination of guided wave modes could relate to the differences in corrosion mechanisms and rates in the two environments. Ultrasonic test results correlated well with that of the destructive tests.

Numerical and experimental study of guided waves for detection of defects in the rail head

Abstract: This paper gives insight to the ultrasonic wave propagation in arbitrary cross-section waveguides such as rails, with application to ultrasonic inspection. Due to the geometrical complexity of the rail cross-section, the analytical solution to the wave propagation in the rail is not feasible. A Semi Analytical Finite Element method is described as an alternative yet still robust approach to get the solution of the problem. The free-vibration solution and the forced solution to a laser excitation of the rail head are shown up to a frequency of 500 kHz. The effects of different loading patterns are discussed, and experimental results are provided. The analysis allows for the identification of certain wave modes potentially sensitive to specific types of rail head defects.

Airborne ultrasonic vortex generation using flexible ferroelectrets

Abstract: Cellular ferroelectrets exhibit interesting electromechanical- acoustical characteristics. Their recent appearance and remarkable properties open up new possibilities for the design and development of ultrasonic transducers. In particular, the feasibility of fabricating ultrasonic vortex generators using ferroelectret films is demonstrated in this work. To this end, a transducer prototype was built by gluing the material onto a tangential-helical surface (outer diameter: 40 mm, pitch: 3.45 mm). Experimental results agree well with the theoretical estimation of the pressure and phase of the acoustic field in the near field and far field, which corroborates the potential of ferroelectrets to customize special acoustic fields. Furthermore, the proposed fabrication procedure is inexpensive and represents a new alternative for exploring and analyzing the special characteristics of acoustical helical wavefronts.

A time-of-flight mapping method for laser ultrasound guided in a pipe and its application to wall thinning visualization

Abstract: Piping systems in nuclear power plants (NPPs) are susceptible to flow-accelerated corrosion (FAC) that results in local wall thinning of the piping system. FAC can cause severe piping failure such as leakage and rupture. In this study, a reliable ultrasonic time-of-flight (ToF) mapping system in the pipe is proposed with the goal of improving ultrasonic NPP pipe inspection. The system consists of a high-speed laser ultrasonic scanning system (50 mm/s at intervals of 0.5 mm) and two ultrasonic sensors. The ToF mapping algorithm uses mode identification based on wavelet transform, an automatic threshold setting method based on the statistics of the spatial noise map, and two-dimensional (2-D) ToF extraction based on the threshold crossing time method. The Lamb-like waves guided in the wall of a stainless steel (SUS) straight pipe were simultaneously interrogated by the proposed two-channel laser ultrasonic system. The proposed ToF mapping algorithm enabled the generation of a smooth ToF distribution within the beam incidence angle of ±60° in the curved surface of the pipe. Then a ToF mapping method was applied to a wall-thinned pipe, and an ultrasonic wave propagation movie was generated to help understand the complex ultrasonic propagation pattern. Based on an understanding of the ToF change in the wall-thinned region, and on the mode collapse and attenuation that occurred because of the ultrasonic bottleneck phenomenon, the wall-thinned region was evaluated. Since this method allows in-situ and automatic field inspection, it can contribute to NPP pipe health management.

A Noncontact Ultrasonic Platform for Structural Inspection

Abstract: Miniature robotic vehicles are receiving increasing attention for use in nondestructive testing (NDE) due to their attractiveness in terms of cost, safety, and their accessibility to areas where manual inspection is not practical. Conventional ultrasonic inspection requires the provision of a suitable coupling liquid between the probe and the structure under test. This necessitates either an on board reservoir or umbilical providing a constant flow of coupling fluid, neither of which are practical for a fleet of miniature robotic inspection vehicles. Air-coupled ultrasound offers the possibility of couplant-free ultrasonic inspection. This paper describes the sensing methodology, hardware platform and algorithms used to integrate an air-coupled ultrasonic inspection payload into a miniature robotic vehicle platform. The work takes account of the robot's inherent positional uncertainty when constructing an image of the test specimen from aggregated sensor measurements. This paper concludes with the results of an automatic inspection of a aluminium sample.

Application of signal processing techniques to ultrasonic testing of plates by S0 Lamb wave mode

Abstract: In recent years, much attention has been paid to the use of Lamb waves for structural health monitoring. This choice is prompted by the high speed of Lamb wave inspection, although their dispersive nature can complicate the interpretation of results, especially when dealing with closely-spaced reflectors. In this paper, the objective is to improve the time resolution and signal-to-noise ratio of signals obtained from inspection of plates by the S0 Lamb mode. The signal processing scheme used is based on deconvolution of the measured signal by Wiener filtering, followed by autoregressive spectral extrapolation. The deconvolution technique is applied to signals obtained from finite element models and also to experimentally measured signals; both sets of data are based on plates with various types of notch discontinuities. Using this technique, the separation distance between adjacent notches was estimated with high accuracy in both simulated and experimental ultrasonic signals.

Monitoring early age property of cement and concrete using piezoceramic bender elements

Abstract: Ultrasonic waves are commonly used for non-destructive evaluation of concrete structures. For fresh concrete, ultrasonic waves have also been used to monitor concrete setting and strength development at early ages. However, the conventional ultrasonic test set-up typically needs access to the two opposite sides of concrete structures, which is not always possible for in situ field testing. In this paper, embedded piezoceramic bender elements are proposed to measure ultrasonic shear (S) waves in fresh cement paste, mortar and concrete. The shear wave velocities are obtained from B-scan images of a collection of recorded signals over time. Experimental results indicate that the shear wave velocity is closely related to the setting time, and this relationship is independent of air void content and w/c of cement pastes. The low cost bender elements can also be of use to monitor the setting of fresh concrete and the long term evaluation of hardened concrete. (Some figures in this article are in colour only in the electronic version)

Mechanical Damage Detection in Polymer Tiles by THz Radiation

Abstract: Today the ultrasonic inspection technique is probably the most popular method for nondestructive evaluation and structural health monitoring. However, ultrasonic waves are not very effective in detecting internal defects in some materials such as ceramic foam tiles used in the thermal protection system (TPS) of the space shuttle, thick polymer composites, and polymer tiles used in various applications. Ultrasonic energy is attenuated very fast in these materials. On the other hand the electromagnetic radiation in THz (1000 GHz) frequency range can penetrate deep inside these materials. Its wavelength is small enough to detect internal defects. To understand the limits of structural damage detection capability of THz electromagnetic radiation or T-ray, mechanical damage in polymer tiles is introduced by drilling holes. Then T-ray is passed through the damaged and defect-free tiles. The received signal strength is found to be affected differently by the internal defect as the frequency changes. Experimental observations are justified from the model predictions. The model takes into account the interaction between the T-ray of finite width and the tile containing the internal defect.

Model-based simulation of focused beam fields produced by a phased array ultrasonic transducer in dissimilar metal welds

Abstract: Phased array ultrasound testing (PAUT) can produce steerable and tightly focused ultrasonic beams, so it is widely used for detecting flaws However, inspection of dissimilar metal welds (DMWs) using phased array ultrasound is not easy at all, since ultrasonic beams are skewed and distorted severely in the welds that are anisotropic and inhomogeneous elastic media So, to increase focusing efficiency and have optimized conditions for inspecting the welds, quantitative prediction of phased array ultrasonic beams is needed This paper proposes a modeling approach that includes modeling the grain orientation of the welds with buttering, calculating the ray path for the determination of focal laws, and applying the linear phasing multi-Gaussian beam model in order to focus the ultrasonic beams produced by a phased array transducer mounted on a wedge contacted to the interrogated DMW This paper also presents an example of the model-based simulation of the focused beam fields produced in the DMW The proposed model allows us to increase the focusing efficiency by accurately simulating the ultrasonic testing of welded components and to propose a new tool to associate welding design with the ultrasonic assessment of structural integrity

Ultrasonic probe deployment device for increased wave transmission and rapid area scan inspections

Abstract: An ultrasonic probe deployment device in which an ultrasound-transmitting liquid forms the portion of the ultrasonic wave path in contact with the surface being inspected (i.e., the inspection surface). A seal constrains flow of the liquid, for example preventing the liquid from surging out and flooding the inspection surface. The seal is not rigid and conforms to variations in the shape and unevenness of the inspection surface, thus forming a seal (although possibly a leaky seal) around the liquid. The probe preferably is held in place to produce optimum ultrasonic focus on the area of interest. Use of encoders can facilitate the production of C-scan area maps of the material being inspected.

Monitoring the early-age hydration of self-compacting concrete using ultrasonic p-wave transmission and isothermal calorimetry

Abstract: The early-age hydration (≤48 h) of a series of self-compacting concretes and corresponding mortars and one traditionally vibrated concrete and mortar is monitored in a continuous way using ultrasonic testing and isothermal calorimetry. The mixtures differ in type of mineral addition, superplasticizer, cement, cement-to-powder ratio and water-to-powder ratio. The influence of these different mixture compositions on the kinetics of the hydration during the first days of the hydration is characterized by the heat production rate q and the evolution of the p-wave velocity, which is a consequence of the microstructural changes. The variations in the acceleration caused by mineral additions and the deceleration caused by superplasticizers lead to a significantly different behavior. Separating the impact of each of the affecting factors is not always possible due to their combined actions. The nature of the acceleration due to limestone additions and the deceleration caused by polycarboxylate ether superplasticizers can be distinguished clearly, but cannot be quantified. The correlation between the ultrasonic and isothermal calorimetric results is investigated based on parameters related to the start and the end of the setting and reveals the meaningfulness of these parameters when assessing the hydration of self-compacting mixtures with continuous ultrasonic techniques.

A Comparison Study Between Acoustic Sensors for Bearing Fault Detection Under Different Speed and Load Using a Variety of Signal Processing Techniques

Abstract: The use of ultrasonic sensor technology to detect incipient and evolving defects in rotating components such as bearings and gears is more desirable due to their high resolution. In a previous study, the sensitivity of a variety of sensors including an air-coupled ultrasound transducer to bearing faults was analyzed and thoroughly discussed. This article investigates the effectiveness of two ultrasonic sensors, namely, air-coupled and piezoelectric ultrasound transducers for rolling element bearings damage diagnostics. The former is a noncontact sensor and the latter is a contact sensor. An accelerometer was also used as the baseline sensor for comparison purposes. A series of tests was carried out on a laboratory test rig running with defective and undamaged healthy bearings under variable shaft speeds and several radial loads. The data were analyzed using selected signal processing techniques covering time, frequency, and advanced joint time–frequency domains. The results showed that certain acoustic fe...

Measurement of elastic properties of materials by the ultrasonic through-transmission technique

Abstract: The elastic mechanical behavior of elastic materials is modeled by a pair of independent constants (Young’s modulus and Poisson’s coefficient). A precise measurement for both constants is necessary in some applications, such as the quality control of mechanical elements and standard materials used for the calibration of some equipment. Ultrasonic techniques have been used because wave velocity depends on the elastic properties of the propagation medium. The ultrasonic test shows better repeatability and accuracy than the tensile and indentation test. In this work, the theoretical and experimental aspects related to the ultrasonic through-transmission technique for the characterization of elastic solids is presented. Furthermore, an amorphous material and some polycrystalline materials were tested. Results have shown an excellent repeatability and numerical errors that are less than 3% in high-purity samples.

Interfacial defects detection in plasma-sprayed ceramic coating components using two stimulated infrared thermography techniques

Abstract: Two Lock-in InfraRed Thermography (LIRT) techniques were developed and applied to detect interfacial defects in a ceramic coated steel plate deposited by plasma spraying technology. Stimulations were performed either by electromagnetic waves (lamps) or by high power ultrasonic waves (sonotrode). The first one is based on remote optical heating of the area of interest; while the second technique is based on the mechanical loss angle effect, occurring locally and for particular defects such as cracks and delaminations. The potential of these two techniques was evaluated against artificial (calibrated holes) and real (disbonding) interfacial defects. The results show success and also some limitations of both LIRT techniques in function of sizes and depths of ceramic coating interfacial defects.

Combined ultrasonic elastic wave velocity and microtomography measurements at high pressures

Abstract: Combined ultrasonic and microtomographic measurements were conducted for simultaneous determination of elastic property and density of noncrystalline materials at high pressures. A Paris–Edinburgh anvil cell was placed in a rotation apparatus, which enabled us to take a series of x-ray radiography images under pressure over a 180° angle range and construct accurately the three-dimensional sample volume using microtomography. In addition, ultrasonic elastic wave velocity measurements were carried out simultaneously using the pulse reflection method with a 10° Y-cut LiNbO3 transducer attached to the end of the lower anvil. Combined ultrasonic and microtomographic measurements were carried out for SiO2 glass up to 2.6 GPa and room temperature. A decrease in elastic wave velocities of the SiO2 glass was observed with increasing pressure, in agreement with previous studies. The simultaneous measurements on elastic wave velocities and density allowed us to derive bulk (Ks) and shear (G) moduli as a function of ...

Ultrasonic flow rate measurement device

Abstract: An ultrasonic flow rate measurement device includes a measurement channel, through which a fluid to be measured flows; and a sensor fixing casing having openings formed in the measurement channel and sensor fixing cavities communicating with the openings Moreover, the ultrasonic flow rate measurement device includes a pair of ultrasonic sensors contained in the sensor fixing cavities, for measuring the flow rate of the fluid to be measured; and a flow rate measuring unit for detecting the flow rate based on an ultrasonic wave propagation time between the pair of ultrasonic sensors Furthermore, the ultrasonic flow rate measurement device includes a suppressing member formed at each of the openings, for suppressing the fluid to be measured from intruding into each of the sensor fixing cavities, wherein the suppressing member is molded integrally with the sensor fixing casing

Fundamental study of detecting internal defect in building materials using high-intensity aerial ultrasonic waves with finite amplitude (Special issue: Ultrasonic electronics)

Abstract: An impact acoustic method and an infrared method are often used to detect peeling in building materials such as concrete and tile. However, both of these methods are susceptible to human error and require long measurement times. In this study, we examine a new method that uses high-intensity aerial ultrasonic waves to detect peeling in building materials. Specifically, we have developed a noncontact method of detecting defects in building materials by analyzing the vibration of an object excited with high-intensity aerial ultrasonic waves of finite amplitude at a frequency of 26.8 kHz. We prepared artificial peeling samples consisting of tile and concrete plates. The results indicated that there is clearly a large difference in vibration velocity and distortion rate between the area with artificial peeling and the area without peeling. Therefore, it is possible to detect peeling of building materials by this method.