Showing papers on "Ultrasonic testing published in 2016"

A review of non-destructive testing methods of composite materials

Abstract: A review provided about non-destructive testing (NDT) methods for the evaluation of composites. The review considers the capabilities of most common methods in composite NDT applications such as Visual Testing (VT or VI), Ultrasonic Testing (UT), Thermography, Radiographic Testing (RT), Electromagnetic Testing (ET), Acoustic Emission (AE), and Shearography Testing with respect to advantages and disadvantages of these methods. Then, methods categorized based on their intrinsic characteristics and their applications.

Recent developments in ultrasonic fatigue

Abstract: The recently increased interest in very high cycle fatigue properties of materials has led to extended use and further development of the ultrasonic fatigue testing technique. Specimens are stimulated to resonance vibrations at ultrasonic frequency, where the high frequency allows collecting lifetime data of up to 1010 cycles and measuring crack propagation rates down to 10−12 m per cycle within reasonable testing times. New capabilities and methods of ultrasonic testing and outstanding results obtained since the year 1999 are reviewed. Ultrasonic tests at load ratios other than R = −1, variable amplitude tests, cyclic torsion tests and methods for in situ observation of fatigue damage are described. Advances in testing at very high temperatures or in corrosive environments and experiments with other than bulk metallic materials are summarized. Fundamental studies with copper and duplex steel became possible and allowed new insights into the process of very high cycle fatigue damage. Higher cyclic strength of mild steels measured at ultrasonic frequency because of plastic strain rate effects are described. High-strength steels and high-alloy steels are less prone to frequency influences. Environmental effects that can lead to prolonged lifetimes in some aluminium alloys and possible frequency effects in titanium and nickel and their alloys are reviewed.

Literature Review: Theory and Application of In-Line Inspection Technologies for Oil and Gas Pipeline Girth Weld Defection

Abstract: Girth weld cracking is one of the main failure modes in oil and gas pipelines; girth weld cracking inspection has great economic and social significance for the intrinsic safety of pipelines. This paper introduces the typical girth weld defects of oil and gas pipelines and the common nondestructive testing methods, and systematically generalizes the progress in the studies on technical principles, signal analysis, defect sizing method and inspection reliability, etc., of magnetic flux leakage (MFL) inspection, liquid ultrasonic inspection, electromagnetic acoustic transducer (EMAT) inspection and remote field eddy current (RFDC) inspection for oil and gas pipeline girth weld defects. Additionally, it introduces the new technologies for composite ultrasonic, laser ultrasonic, and magnetostriction inspection, and provides reference for development and application of oil and gas pipeline girth weld defect in-line inspection technology.

Ultrasonic analysis and lock-in thermography for debonding evaluation of composite adhesive joints

Abstract: Glass-fiber reinforced thermosetting plastic adhesive joints were characterized through ultrasonic imaging and lock-in thermographic analysis for assessing the adhesion quality before being subjected to static tensile mechanical tests and to accelerated aging cycles. The mapping of each sample has been obtained. Visual testing were performed on all specimens after the mechanical tests in order to obtain a comparison with ultrasonic and lock-in thermography technique. A quantitative analysis has been carried out to evaluate the ability of lock-in thermography in investigating inadequate bonding and obtaining the validation of the technique by the consistency of the results with the well-established ultrasonic testing.

Diffuse ultrasound monitoring of stress and damage development on a 15-ton concrete beam

Abstract: This paper describes the use of an ultrasonic imaging technique (Locadiff) for the Non-Destructive Testing & Evaluation of a concrete structure. By combining coda wave interferometry and a sensitivity kernel for diffuse waves, Locadiff can monitor the elastic and structural properties of a heterogeneous material with a high sensitivity, and can map changes of these properties over time when a perturbation occurs in the bulk of the material. The applicability of the technique to life-size concrete structures is demonstrated through the monitoring of a 15-ton reinforced concrete beam subject to a four-point bending test causing cracking. The experimental results show that Locadiff achieved to (1) detect and locate the cracking zones in the core of the concrete beam at an early stage by mapping the changes in the concrete's micro-structure; (2) monitor the internal stress level in both temporal and spatial domains by mapping the variation in velocity caused by the acousto-elastic effect. The mechanical behavior of the concrete structure is also studied using conventional techniques such as acoustic emission, vibrating wire extensometers, and digital image correlation. The performances of the Locadiff technique in the detection of early stage cracking are assessed and discussed.

Non-destructive ultrasonic examination of root defects in friction stir welded butt-joints

Abstract: As a solid-state welding process, Friction Stir Welding (FSW) offers a variety of advantages over traditional welding processes. Problems that are typically occurring due to the cooling of the liquid phase, such as solidification cracking and formation of porosity, generally do not occur in FSW. Nevertheless, as a result of suboptimal settings of the welding process parameters and certain uncontrollable conditions, FSWs are still associated with a number of specific flaws, e.g. root flaws and wormholes. Ultrasonic non-destructive testing and evaluation techniques (NDT&E) can be used for quality assessment of friction stir welded joints. In this paper, a novel approach for the detection of root flaws is proposed using an immersion ultrasonic testing method in oblique incidence and backscatter mode. The backscattered energy C-scan images obtained after an empirical positioning and proper time gating can be straightforwardly interpreted by direct comparison with typical ‘flaw’ patterns, allowing for identification and localization of the root flaws in the weld. The method is illustrated for FSW butt joints of the AlZnMgCu (7XXX series) alloy.

Longitudinal mode magnetostrictive patch transducer array employing a multi-splitting meander coil for pipe inspection

Abstract: Recently, a magnetostrictive patch transducer (MPT) by means of the highly magnetostrictive (such as nickel or iron–cobalt alloy) patch attached on the specimen has been applied in nondestructive ultrasonic testing in waveguides. In the study, we proposed a new MPTs array employing a multi-splitting meander coil (MSMC) for generating and receiving longitudinal guided waves in pipes. In the suggested configuration, the directions of the static magnetic field produced by the permanent magnets and the dynamic magnetic field produced by the MSMC are in the axial direction of the pipe. Two finite element models were established to simulate the distribution of the static and dynamic magnetic fields in the patch, respectively. The proposed MSMC was made of flexible printed circuit (FPC), so it could be easily installed on pipe surface. The performance of the proposed MPTs array was experimentally studied. Firstly, it was experimentally verified that the axisymmetric longitudinal guided wave mode, L(0,2), could be effectively generated and received in pipes with the developed MSMC-MPTs array. Secondly, the frequency response characteristics of the developed MSMC-MPTs array were related to D (the distance between adjacent belts of the MSMC). Thirdly, we demonstrated the ability of the developed MSMC-MPTs array for the identification and location of a crack defect in pipes. Finally, we compared the performances of the MSMC-MPTs array and conventional meander coil-MPTs and proved that the signals of the longitudinal guided wave mode could be enhanced by using the developed MSMC-MPTs array.

Non-destructive investigation of thermoplastic reinforced composites

Abstract: This paper studies various manufacturing defects in glass fiber/Polypropylene (PP) composite parts and their methods of detection. Foreign Object Inclusion (FOI) of different shapes, sizes, and materials were placed in a glass fiber/PP panel made by compression molding. The paper aims to characterize the fiber orientation and fiber related defects such as fiber waviness in the composite specimen. Comprehensive investigation for different Non Destructive Evaluation (NDE) techniques, namely X-ray radiography and Ultrasonic Testing (UT) techniques to trace and characterize the embedded defects and the composite texture are presented. Conventional X-ray radiography successfully identified the fiber orientation in two dimension (2-D) plane; however, information for the sample depth was not captured. The radiography techniques showed low relative errors for the defect size measurements (maximum error was below 9.5%) when compared to the ultrasonic techniques. Ultrasonic techniques were able to map all the embedded artificial defects. Phase Array (PA) ultrasonic technique was able to precisely locate the FOI in the glass fiber/PP specimen. Nerveless, the shape and size of the defects were not accurately determined due to the high signal attenuation and distortion characteristics of the E-glass fiber.

Review on transit time ultrasonic flowmeter

Abstract: Ultrasonic technology is evolving rapidly due to the significant improvements of the flow measurement in continuous industrial process. It is a widely used technology among the non-contact type of flow measurement for its high resolution, low pressure loss, less interference of noise on output. Ultrasonic flowmeters gained the debate, mainly due to measurement ability in custody transfer of natural gas, accurate measurement of the flow of slurries and impurity liquids, works for wide range of nominal diameters. This paper contains review on some important developments of transit time ultrasonic flowmeters particularly to improve the accuracy.

Nondestructive testing and characterization of residual stress field using an ultrasonic method

Abstract: To address the difficulty in testing and calibrating the stress gradient in the depth direction of mechanical components, a new technology of nondestructive testing and characterization of the residual stress gradient field by ultrasonic method is proposed based on acoustoelasticity theory. By carrying out theoretical analysis, the sensitivity coefficients of different types of ultrasonic are obtained by taking the low carbon steel(12%C) as a research object. By fixing the interval distance between sending and receiving transducers, the mathematical expressions of the change of stress and the variation of time are established. To design one sending-one receiving and oblique incidence ultrasonic detection probes, according to Snell law, the critically refracted longitudinal wave (LCR wave) is excited at a certain depth of the fixed distance of the tested components. Then, the relationship between the depth of LCR wave detection and the center frequency of the probe in Q235 steel is obtained through experimental study. To detect the stress gradient in the depth direction, a stress gradient LCR wave detection model is established, through which the stress gradient formula is derived by the relationship between center frequency and detecting depth. A C-shaped stress specimen of Q235 steel is designed to conduct stress loading tests, and the stress is measured with the five group probes at different center frequencies. The accuracy of ultrasonic testing is verified by X-ray stress analyzer. The stress value of each specific depth is calculated using the stress gradient formula. Accordingly, the ultrasonic characterization of residual stress field is realized. Characterization results show that the stress gradient distribution is consistent with the simulation in ANSYS. The new technology can be widely applied in the detection of the residual stress gradient field caused by mechanical processing, such as welding and shot peening.

Non-destructive testing of cementitiously stabilized materials using ultrasonic pulse velocity test

Abstract: In this paper, non-destructive testing of cementitiously stabilized materials (CSMs) was studied using ultrasonic pulse velocity instrumentation. Flexural strength and flexural modulus tests were conducted on CSMs and their constrained modulus were recorded. The effect of compaction, curing time, and binder content was evaluated. The results indicate that the P-wave velocity decreases with decrease in density, whereas P-wave velocity increases with increase in curing time and binder content. A strong relationship (R2 = 0.89) was observed between flexural strength and constrained modulus, while the relationship between flexural modulus and constrained modulus at 30% stress level was also high (R2 = 0.70). Non-destructive testing is thus proposed as a convenient and expedient method for determining the flexural properties of CSMs in comparison to destructive methods such as third-point bending beam tests.

Fatigue Crack Growth Monitoring in Composite Bonded Lap Joints by a Distributed Fibre Optic Sensing System and Comparison with Ultrasonic Testing

Abstract: In this paper, the back-face technique is exploited to monitor fatigue crack growth (FCG) in a composite, single lap adhesive bonded joint, using distributed sensing by Optical Backscatter Reflectometry (OBR). Some preliminary results are presented, indicating that, by measuring accurately the strain profile in the overlap region, the correlation between the minimum peak of the strain profile and the position of the crack tip can be exploited for monitoring the structural health of joints. The proposed structural health monitoring technique was validated on the basis of the results obtained by a non-destructive technique using phased array ultrasonic testing (PAUT). The comparison between the two methods yielded encouraging results, suggesting that, thanks to its distributed sensing capabilities, the OBR technology could allow for improving the back face (BF) technique, as well as any other strain field-based measurement technique, for the health monitoring of adhesive joints.

Analytical modeling and experimental validation of a V-shape piezoelectric ultrasonic transducer

Abstract: In this paper, an analytical model of a V-shape piezoelectric ultrasonic transducer is presented. The V-shape piezoelectric ultrasonic transducer has been widely applied to the piezoelectric actuator (ultrasonic motor), ultrasonic aided fabrication, sensor, and energy harvesting device. The V-shape piezoelectric ultrasonic transducer consists of two Langevin-type transducers connected together through a coupling point with a certain coupling angle. Considering the longitudinal and lateral movements of a single beam, the symmetrical and asymmetrical modals of the V-shape piezoelectric ultrasonic transducer are calculated. By using Hamilton–Lagrange equations, the electromechanical coupling model of the V-shape piezoelectric ultrasonic transducer is proposed. The influence of the coupling angle and cross-section on modal characteristics and electromechanical coupling coefficient are analyzed by the analytical model. A prototype of the V-shape piezoelectric ultrasonic transducer is fabricated, and the results of the experiments are in good agreement with the analytical model.

Ultrasonic tracking of ply drops in composite laminates

Abstract: As the shapes of composite components become more adventurous, tracking internal locations of ply drops and detecting any tape gaps or overlaps will be crucial to assure conformance to design. The true potential of ultrasound has yet to be exploited for this objective due to the apparent complexity of the ultrasonic response and the assumption that interference between signals from plies is random, confusing and of little use. As a result, most ultrasonic inspection of composites targets defects that either attenuate or reflect ultrasound, regarding ply reflections as undesirable ‘noise’. The work presented here extends the ply-orientation mapping of the last two decades by introducing a systematic approach to optimizing the ultrasonic response from the plies, minimizing interference between plies and demonstrating that accurate maps of plies through ply-drop regions can be produced. The key to this method is understanding the ultrasonic analytic signal and how it interacts with plies and the resin-rich layers between them. In certain circumstances of frequency and bandwidth, the instantaneous phase locks onto the resin-rich layers and the instantaneous amplitude indicates the validity of this condition. Analytical modelling is used to explain the interaction between ultrasound and composite plies in various ply-drop scenarios, with reference to experimental results. Optimization of ultrasonic data acquisition is also discussed and demonstrated experimentally.

Study of ultrasonic thermometry based on ultrasonic time-of-flight measurement

Abstract: Ultrasonic thermometry is a kind of acoustic pyrometry and it has been evolving as a new temperature measurement technology for various environment. However, the accurate measurement of the ultrasonic time-of-flight is the key for ultrasonic thermometry. In this paper, we study the ultrasonic thermometry technique based on ultrasonic time-of-flight measurement with a pair of ultrasonic transducers for transmitting and receiving signal. The ultrasonic transducers are installed in a single path which ultrasonic travels. In order to validate the performance of ultrasonic thermometry, we make a contrast about the absolute error between the measured temperature value and the practical one. With and without heater source, the experimental results indicate ultrasonic thermometry has high precision of temperature measurement.

Ultrasonic Array Imaging Through an Anisotropic Austenitic Steel Weld Using an Efficient Ray-tracing Algorithm

Abstract: Ultrasonic inspection of austenitic welds is challenging due to their highly anisotropic and heterogeneous microstructure. The weld anisotropy causes a steering of the ultrasonic beam leading to a number of adverse effects upon ultrasonic array imagery, including defect mislocation and aberration of the defect response. A semi-analytical model to simulate degraded ultrasonic images due to propagation through an anisotropic austenitic weld is developed. Ray-tracing is performed using the A⁎ path-finding algorithm and integrated into a semi-analytical beam-simulation and imaging routine to observe the impact of weld anisotropy on ultrasonic imaging. Representative anisotropy weld-maps are supplied by the MINA model of the welding process. A number of parametric studies are considered, including the magnitude and behaviour of defect mislocation and amplitude as the position of a fusion-face defect and the anisotropy distribution of a weld is varied, respectively. Furthermore, the use of the model to efficiently simulate and evaluate ultrasonic image degradation due to anisotropic austenitic welds during an inspection development process is discussed.

In-Process Ultrasonic Inspection of Additive Manufactured Parts

Abstract: This project introduces an in-situ application of ultrasonic inspection techniques to fused deposition modeling (FDM) in order to detect defects as they are produced in a 3D printed plastic part. The growth of additive manufacturing into performance critical applications has revealed the need for precise quantitative evaluation of printed parts. Ultrasonic testing has been extensively demonstrated as a means of detecting small geometric defects in materials, but has not previously been applied in-process to thermoplastic FDM. This experiment used four piezoelectric transducers bonded to the build plate of an FDM machine printing Acrylonitrile Butadiene Styrene (ABS) to ultrasonically inspect parts periodically during the printing process. Every 30 s, the partially formed model is interrogated with an ultrasonic chirp signal and the response recorded. The normalized frequency response is then compared to an experimentally determined ideal response in order to detect faults in the most recently deposited layers. This analysis is based on the hypothesis that the frequency response of the part will be substantially altered if unexpected (defective) geometries are present. Due to the complexity added by low-density internal structures, this work investigates only parts with a solid fill and simple external geometries. However, with sufficient signal processing capabilities, it is feasible to extend this technique to more complicated part shapes and low-density fill patterns, as might be expected in a manufacturing setting.

Multimode Interference-Based Fiber-Optic Ultrasonic Sensor for Non-Contact Displacement Measurement

Abstract: In this paper, ultrasonic sensor based on multimode interference in single-mode–multimode–single-mode optic fiber structure for non-contact displacement measurement is presented and investigated. By experimentally testing and optimizing the sensor structure, an ultrasonic wave with a frequency of 25 kHz can be sensitively detected with a 7 m non-contact detection distance. Displacement measurement by employing phase shift detection is conducted and the experimental results verify that a resolution 0.1 mm within the measurement range of 6 mm can be achieved for 7-m non-contact distance based on the proposed system.

Determination of the material properties of polymers using laser-generated broadband ultrasound

Abstract: . In the non-destructive determination of material properties, the utilization of ultrasound has proven to be a viable tool. In the presented paper, a laser is used to create broadband acoustic waves in plate-shaped specimens by applying the photoacoustic effect. The waves are detected using a purpose-built ultrasonic transducer that is based on piezoceramics instead of the commonly used piezoelectric polymer films. This new transducer concept allows for detection of ultrasonic waves up to 10 MHz with high sensitivity, thereby allowing the characterization of highly damping materials such as polymers. The recorded data are analysed using different methods to obtain information on the propagation modes transmitted along the specimen. In an inverse procedure, the gained results are compared to simulations, yielding approximations for the specimen's material properties.

Strength and Ultrasonic Characteristics of Alkali-Activated Fly Ash-Slag Geopolymer Concrete after Exposure to Elevated Temperatures

Abstract: Geopolymer concrete is an environment-friendly building material which has attracted increasing interest in many fields as a replacement for conventional concrete. The main objective of this paper is to study the residual behaviors of the alkali-activated fly ash–slag geopolymer concrete (FSGC) under different heating temperatures and cooling regimes. Changes in weight, compressive strength and ultrasonic pulse velocity were firstly investigated. Then the wavelet packet technique was adopted to further analyze the measured ultrasonic signals in frequency domain. Finally, the microstructures were investigated by scanning electron microscopy. The results indicate that an increase in temperature makes the weight, compressive strength, and ultrasonic pulse velocity value of FSGC decrease, especially under extreme heat conditions. The deterioration of specimens cooled by watering is more obvious than that of specimens cooled naturally. Based on the experimental results, it can be concluded that the crit...

Laser-Ultrasonic Testing of the Structure and Properties of Concrete and Carbon Fiber-Reinforced Plastics

Abstract: This paper discusses the possibility of studying composite materials by non-destructive laser-ultrasonic testing technique. Concrete samples and carbon-epoxy composites were examined, defects located and elastic wave velocities measured. The internal structure of the samples was visualized in 2D images.