Nondestructive Testing Of Materials Research Articles

Radio wave phase method for polymer materials testing

The problems of the radio wave phase method for non-destructive testing of polymer composite materials (PCM) using a semi-confocal resonator in laboratory conditions are considered. The essence of the method is the accumulation of calibration dependencies on reference samples to detect any defect.

Identification of defect type in non-destructive testing of polymer composite structures

The paper describes non-destructive testing of composite honeycomb materials, to identify the type of defect, such as delamination, non-adhesion, inclusion, etc. Practical recommendations on testing monolithic, combined, multilayer and reinforced structures and defect identification have been given.

Probability of defect detection in pulse compression favourable thermal excitation schemes for infra‐red non‐destructive testing

InfraRed non-destructive testing and evaluation (IRNDT&E) has emerged as a promising approach for non-destructive testing and evaluation (NDT&E) of various materials because of its inherent merits such as remote, non-invasive, qualitative as well as quantitative inspection capabilities. Among the various IRNDT&E techniques, recently proposed modulated pulse compression favourable thermal wave imaging (PCTWI) techniques, especially frequency modulated thermal wave imaging (FMTWI) and its digitised version digitised FMTWI (DFMTWI) have gained popularity over the conventional sinusoidal modulated [lock-in thermography (LT)] and pulse-based thermographic techniques [pulse thermography (PT) and pulse phase thermography (PPT)] by providing better depth resolution, in less experimentation time, using low peak power excitation heat sources. The present work highlights a comparative study on highly depth resolved continuous depth scanning PCTWI techniques, with single frequency thermal excited LT, on the basis of defect detection probability. The proposed study has been carried out on a glass fibre reinforced polymer test sample with Teflon inserts as defects by considering peak side lobe ratio as a figure of merit. The experimental results clearly show that the probability of detection of defects for DFMTWI is far superior as compared to FMTWI and LT.

Guest Editorial: Non‐Destructive Testing

Guest Editorial: Non‐Destructive Testing

Complementary physicochemical analysis by ellipsometry and Auger spectroscopy of nano-sized protective coating layers

Protective SiC-rich nano layer was created by ion beam mixing of Si/C multilayers. The transformation of the Si and C layers into a homogeneous SiC layer was analyzed using complementary depth profiling by spectroscopic ellipsometry (SE) and Auger electron spectroscopy (AES). The distribution of elements and their chemical states was revealed by AES, whereas SE measured the accurate thicknesses, density, crystallinity, and the distribution of different phases. The optical properties of the created SiC layer determined by SE were almost identical to that of ion implantation-amorphized SiC. Amorphous Si and void formations were revealed by SE. The void profile determined by SE correlated well with the Xe distribution measured by AES. The complementary capabilities of SE and AES for a detailed chemical investigation were pointed out, such as the atomic (AES), structural (AES and SE) and non-destructive depth profiling (SE) features. It was shown that besides the synergism that the two methods reveal, SE is capable of a quick, sensitive and non-destructive testing of such layer structures and materials.

Influence of Aggregates in Concrete on Fiber-Optic Based Thermal Integrity Profiling Analysis of Concrete Structures

Fiber-optic sensor has drawn wide attention in the nondestructive testing and evaluation of civil engineering materials due to its high accuracy and resolution as well as cost-efficiency. Currently, using optical fiber as the temperature sensor is proposed to conduct the thermal integrity profiling (TIP) of concrete structures. However, concrete is not a thermally homogeneous material as assumed in current studies of concrete TIP. Its essential components, such as aggregates may cause thermal inhomogeneity problems when implementing fiber-optic sensors for TIP. In this paper, we use the concrete structures with different grades of aggregates to conduct numerical simulation for nondestructive thermal testing. The goal is to investigate how the thermal inhomogeneity caused by aggregates would influence the testing result. Firstly, we establish three concrete structure models with three different grades of aggregates based on the scenarios where these concrete structures will be used. Then, we numerically simulate the thermal process on these models and extract the temperature at the location where optical fiber would be installed. The influence caused by the inhomogeneity of aggregate size and distribution as well as the possible method to minimize the effect are evaluated in the paper. Overall, aggregates of concrete have a significant influence on the accuracy of TIP analysis, and defects could be veiled if no proper treatment to the data is implemented for TIP analysis.

Technical Note: The Anti-plane Scattering of SH Waves by the Non-circular Cavity in an Infinite Strip

ABSTRACT In this paper, the problem of dynamic stress concentration in the process of anti-plane motion caused by a single circular cavity in a strip medium and the non-circular cavity in a porous strip medium is studied. In the case of only a single circular cavity, a numerical calculating example is presented to solve scattering around a circular cavity with a given SH guided wave and describe dynamic stress distribution at the edge of a circular cavity. Then, the results of the finite element method and analytical method are used to verify each other. Firstly, a compatible guided wave is constructed in the elastic strip, which satisfies stress-free conditions in upper and lower boundaries. Secondly, the scattering of waves around a circular cavity is expressed as series form by the employed wave function expansion method, and compatible scattering guided waves resulting from the reflection of waves off the boundaries of the elastic strip is constructed by repeated image superposition. Lastly, the coefficients of the wave function expansion are determined based on the stress-free condition of circular boundaries with pre-given incident guided waves. In the case of the non-circular cavity in the medium, the scattering of guided waves from the cavity is solved by finite element analysis, the dynamic stress distribution factor around the edge of the cavity is given, and to discuss influences of wave frequency and cavity position. The conclusions of this paper are of great reference value to the selection and ultrasonic non-destructive testing of anti-seismic materials.

Spectral imaging using compressive sensing‐based single‐pixel modality

Spectral imaging technique plays a very vital role in the field of chemical detection and identification. Conventional spectroscopic imaging techniques suffer from massive acquisition time. This limitation sometimes restricts it from many practical applications. The acquisition of a full spectral image requires huge acquisition time. In this Letter, a compressive sensing-based single-pixel camera architecture has been realised to acquire spectral images that can be used for non-destructive testing and classification of explosive materials. The compressive measurements for all the spectral images are done simultaneously thus reducing the acquisition time significantly. The spectro-spatial images were reconstructed using the basis pursuit algorithm and compared with least square solutions, which resulted in fast acquisition and improved image quality. The maximum compression rate achieved was 95.84%.

A Monte Carlo evaluation of neutron images quality in a research reactor based neutron radiography facility

Neutron radiography is a useful tool for non-destructive testing of materials for research and industrial applications. Image quality assessment is an important factor that contributes to the improvement of radiographic parameters and is essential for the confirmation of the neutron radiography accuracy. The Image quality indicators (IQIs) are used for determination of the quality and sensitivity of the neutron radiographic images. In present study, the quality of the images in a neutron radiography system based on research reactor has been investigated via MCNPX Monte Carlo simulation code. Also, an experimental validation has been carried out based on using standard IQIs. The simulation results of beam purity indicator image investigation showed that the effective thermal neutron content of designed system is about 88.32% and the other malicious parameters have been obtained below 1%. The visual inspection of gaps and shims on the sensitivity indicator image determined the value of smallest gap and the value of largest visible hole. The obtained factors for IQI designation of quality level demonstrated that the neutron radiographic category of our designed and optimized system is a Category I facility.

Quantitative Evaluation of Crack Depths on Thin Aluminum Plate Using Eddy Current Pulse-Compression Thermography

Eddy current stimulated thermography is an emerging technique for non-destructive testing and evaluation of conductive materials. However, quantitative estimation of the depth of subsurface defects in metallic materials by thermography techniques remains challenging due to significant lateral thermal diffusion. This work presents the application of eddy current pulse compression thermography to detect surface and subsurface defects with various depths in an aluminum sample. Kernel Principal Component analysis and Low Rank Sparse modelling were used to enhance the defective area, and cross point feature was exploited to quantitatively evaluate the defects depth. Based on experimental results, it is shown that the crossing point feature has a monotonic relationship with surface and subsurface defects depth, and it can also indicate whether the defect is within or beyond the eddy current skin depth. In addition, the comparison study between aluminum and composites in terms of impulse response and proposed features are also presented.

Applicability of microwave non destructive diagnostics for composite materials used in the aerospace industry

The paper offers an analysis of some of the peculiarities associated with the application of the microwaves (MW) for non-destructive testing (NDT) of composite materials used in the aerospace industry. Special attention is paid to the influence of the compound of the materials of which are made composites, their shape and structure on reflection, refraction and attenuation of electromagnetic waves.

Radiowave Methods of Polymer Composite Defect Diagnostics under Nonsteady Temperatures

The paper deals with the issues of the combined radio wave and thermal test methods for nondestructive testing of polymer composite materials (PCM) in laboratory and factory conditions.

Nondestructive Internal Defect Detection Using a CW–THz Imaging System in XLPE for Power Cable Insulation

The demand for internal nondestructive testing and inspection techniques is rapidly increasing. Using a continuous wave (CW) terahertz (THz) imaging system, we demonstrate that the internal defects in cross-linked polyethylene (XLPE) plates for power cable insulation can be detected. In a coherent detection scheme based on photomixers, which serve as the THz emitters and receivers, the change of phase occurring with the defects inside the XLPE plates is distinctly measured by the change in the amplitude of the transmitted THz waves. According to the two-dimensional images of THz waves transmitted through the XLPE plates, defects of up to 0.5 mm size located inside the XLPE plates can be detected by the internal nondestructive examination method based on CW–THz waves. This technique will be useful for internal nondestructive testing and inspection of insulation materials that require high resolution in various industries, including the automobiles, electronics, and electrical power industries.

Multi-scale gapped smoothing algorithm for robust baseline-free damage detection in optical infrared thermography

Flash thermography is a promising technique to perform rapid non-destructive testing of composite materials. However, it is well known that several difficulties are inherently paired with this approach, such as non-uniform heating, measurement noise and lateral heat diffusion effects. Hence, advanced signal-processing techniques are indispensable in order to analyze the recorded dataset. One such processing technique is Gapped Smoothing Algorithm, which predicts a gapped pixel's value in its sound state from a measurement in the defected state by evaluating only its neighboring pixels. However, the standard Gapped Smoothing Algorithm uses a fixed spatial gap size, which induces issues to detect variable defect sizes in a noisy dataset.In this paper, a Multi-Scale Gapped Smoothing Algorithm (MSGSA) is introduced as a baseline-free image processing technique and an extension to the standard Gapped Smoothing Algorithm. The MSGSA makes use of the evaluation of a wide range of spatial gap sizes so that defects of highly different dimensions are identified. Moreover, it is shown that a weighted combination of all assessed spatial gap sizes significantly improves the detectability of defects and results in an (almost) zero-reference background. The technique thus effectively suppresses the measurement noise and excitation non-uniformity. The efficiency of the MSGSA technique is evaluated and confirmed through numerical simulation and an experimental procedure of flash thermography on carbon fiber reinforced polymers with various defect sizes.

Heat flow thermography for non-destructive testing of composites and natural materials – An application-oriented overview

Abstract Heat flow thermography is a non-destructive testing method that offers a number of advantages. These include the relatively quick inspection of larger areas, the ease of interpretation of the results and the absence of potential hazards such as ionizing radiation. The disadvantage is, depending on the application, its limited penetration depth. The present article explains the physical principles of the process and provides examples of concrete realizations, mainly in the field of composites and natural materials. One focus is on the evaluation of the acquired thermal images and image series, since they often contain more information than is visible at first glance, and a suitable post-processing of the data is the key to a successful application.

Synthesis and Characterization of CNT Composites for Laser‐Generated Ultrasonic Waves

AbstractIn the last few years, extensive progress in ultrasonic wave generation by using multiwalled carbon nanotubes (MWCNTs) in combination with polydimethylsiloxane (PDMS), functional composites, has been achieved. Due to high optical absorption of MWCNTs as perfect absorbers for laser beams and the high thermal expansion coefficient of PDMS, a compact transducer for ultrasonic wave generation at higher frequency can be realized. This study reports a novel method to synthesize MWCNT–PDMS composites deposited on a glass substrate by spray coating, which is done in a short time of 2 h. The layers (0.9–32.2 µm) show low optical transmission properties of 13.9–0.0% at a wavelength of 1047 nm. Apart from using a 1% Triton‐X‐100 stock solution and then diluted to a 0.1% relatively nonhazardous solution, no toxic chemicals are used. The Triton‐X‐100 solution is not hazardous for lab handling and is a commonly used lab detergent for the treatment of biological cells. The achieved sound pressure level is 3.4 MPa with a frequency bandwidth of 9.7 MHz. These results show the potential for a fast and nontoxic production of laser‐generated ultrasonic transducers, which can be used well in the field of nondestructive material testing of layered materials or in medicine with an appropriate frequency range.

Selected Magnetic Resonance applications for non-destructive material testing

Abstract Magnetic resonance’s potential is already proven in the clinical sector and for non-destructive testing also in the laboratory environment. With recent developments in technology today’s small and midsized often portable MR systems are also able to work in an industrial setup and in the field. Therefore, the number of MR applications is rapidly increasing as is the acceptance of MR as technique for non-destructive testing. Selected examples for magnetic resonance in polymers, in porous media and in food samples are shown here.

Non-destructive testing of carbon-fiber-reinforced plastics with a PCB-based T-R probe

Circular coils are widely used in non-destructive testing of traditional isotropic materials. However, from the perspective of anisotropy and low conductivity of carbon-fiber-reinforced plastics (CFRPs), square coils which can effectively improve the electromagnetic coupling between carbon fibers and coil wires, are more suitable for CFRPs. Concerning this issue, a method using PCB-based transmitter–receiver (T-R) probe with square spiral coils for non-destructive testing of CFRPs was proposed in this paper. The proposed probe consists two square spiral coils manufactured on printed circuit board. Rotation experiments on unidirectional laminates, orthogonal woven laminates, four-directional angle-ply laminates were carried out. Results show that the characterization of fiber orientations can be realized. Scanning experiments show that the proposed method can be used to detect cracks, in-plane waviness and abnormal fiber distribution. The length of cracks can be estimated from the scanning images. By comparison of scanning image obtained along different fiber orientations, anisotropic of CFRPs can be reflected. It also shows that the proposed method can selectively detect defects in specific direction.

The dynamic stress analysis of an infinite piezoelectric material strip with a circular cavity

The scattering of SH guided wave by a circular cavity in an infinite piezoelectric material strip is analyzed by using “mirror image method” and guided wave theory, and the analytical expressions of guided wave function satisfying stress free and electric insulation conditions on the upper and lower horizontal boundaries of the strip domain are obtained. The analytical expression of the scattered wave around a circular cavity is constructed by using the method of multiple mirror superposition and wave function expansion. The integral equations are established and solved by the boundary conditions of the circular cavity, and the analytical expressions of the dynamic stress concentration factor and the electric field intensity factor are obtained. The effects of incident wave frequency, dielectric parameters and circular cavity position on electric field intensity concentration factor (EFICF) and dynamic stress concentration factor (DSCF) are analyzed by numerical examples. Besides, the analytical solutions obtained in this article are compared with the finite element solutions and the analytical solutions in previous literature to verify the correctness and accuracy of the conclusions in this article. And the conclusions in this article are of great reference value to the selection and ultrasonic nondestructive testing of anti-seismic materials.

Analysis of measurement conditions influence on the magnetic Barkhausen noise phenomenon


 
 
 The effectiveness of the magnetic Barkhausen noise method (MBN), used for non-destructive testing of ferromagnetic materials, depends to a large extent on a number of factors determining the measurement conditions. The use of conditions allowing the highest possible level of discrimination between the various states of the materials state is of highest importance. Therefore, this paper presents an analysis of the impact of measurement conditions on Barkhausen noise signals observed for various states of the material conditions. Taking into consideration the stochastic nature of MBN and the complex characterization of its changes, the analysis was based on the time-frequency representation of the MBN signal. The paper presents selected distributions achieved using two transformation methods. In addi- tion, the extraction methods of features allowing the quantification of complex information were given. Finally, the discrimination ability for a number of parameters and features of MBN signals were deter- mined and the obtained results were discussed.