Non-contact Non-destructive Testing Research Articles

Visualization of slit defect by scanning nonlinear airborne ultrasound source technique using compressed sensing

A high-speed, non-contact non-destructive testing method using a scanning airborne ultrasound source and a nonlinear harmonic method has been developed for plate-like structures. The testing time depends on the scanning speed and the number of measurement points. To solve this problem, we propose using compressed sensing with this method. In this paper, we investigated visualizing Lamb wave propagation using the proposed compressed sensing method. In addition, we detected a slit defect by using the Lamb wave propagation image. Our results demonstrated that compressed sensing could be used to reduce the testing time.

High-resolution induction thermography for detection of micro-cracks in Ti-6Al-4V alloys

ABSTRACT This study focuses on establishing a non-contact Non-Destructive Testing (NDT) method for detecting micro-cracks in Ti-6Al-4 V sample using the Eddy Current Thermography (ECT) technique. The study employs an induction coil for heating the sample and a thermal camera equipped with magnifying lenses to monitor surface temperature distribution. The variations in the thermal image signify the presence of defects. The efficacy of the proposed method is demonstrated through the examination of four samples featuring artificially created short notches, representing micro-cracks. These notches vary in dimensions, with notch openings approximately 20 µm, notch depths ranging from 1–10 µm, and notch lengths varying from 5 to 150 µm. The investigation explores the influence of the length and depth of short cracks on defect detection, revealing an increase in thermal contrast with both the length and width of the cracks. All notches are successfully detected using the proposed method, showcasing its applicability for real crack detection. The study concludes with the successful application of the method on a sample with actual cracks measuring less than 10 µm in width, 2 µm in depth, and a length of 100 µm.

Progress and comparison in nondestructive detection, imaging and recognition technology for defects of wafers, chips and solder joints

ABSTRACT As an essential part of integrated circuit, chip manufacturing has increasingly demanding requirements for quality, cost and others. Some technical limitations and the development direction of miniaturisation and high density have led to defects in the manufacturing process, which affect the performance and life of the chip. Therefore, the detection, identification and classification of defects are very important to improve the chip reliability. Based on the orderly and concise literature research, this paper focuses on a comprehensive review of the main research results in the field of non-contact non-destructive testing imaging methods for chip defects. Firstly, various defects that may occur in the chip design and packaging process are introduced. Then the contact detection methods including manual and probe method are clarified, and the principles, properties and development applications of NDT methods are introduced in detail, also the defect identification methods after imaging are briefly introduced. Moreover, the advantages and limitations of NDT technologies are summarised through comparative studies. Finally, the future development trend of non-destructive testing methods is predicted. This work hopes to provide some reference for the non-destructive testing of chips, which is of great significance for the health testing of chips in the electronics manufacturing industry.

Changes in the Optical Properties of Rubber Exposed to High-Pressure Hydrogen Using Pulsed Terahertz Waves.

In this study, we investigated how high-temperature, high-pressure hydrogen affects the optical properties of three kinds of sealing rubber (chloroprene rubber, ethylene propylene diene monomer, and acrylonitrile butadiene rubber) using pulsed terahertz waves. The optical properties of the rubber samples were analyzed before and after exposure to hydrogen (80 °C and 200 bar) for 72 h. The results showed that the terahertz waves had a shorter time delay and a lower signal intensity for all rubber types. The exposure response intensity, refractive index, and absorption rate also changed in the frequency domain. Raman and Fourier transform infrared spectroscopy were used for comparison, and a few peak shifts were observed. However, the Raman spectra had low signal quality, and the laser damaged the specimen. The study demonstrates that terahertz waves can be used as a non-contact non-destructive testing technique to evaluate the changes in sealing rubbers after hydrogen exposure.

Evaluation Method for the UV Aging State of Composite Insulators Based on Hyperspectral Characteristic

Strong ultraviolet (UV) radiation is one of the main factors that lead to the aging of composite insulators of transmission lines in high altitude areas, which has brought security risks to the operation of power systems. The aging status information obtained by traditional insulation surface aging detection methods is indirect and limited, or time-consuming and labor-intensive. In this paper, a non-contact nondestructive testing evaluation method based on hyperspectral technology is proposed to quickly detect the UV aging state of composite insulator surface. Firstly, the hyperspectral imaging platform is used to image a number of continuous bands on the insulator surface. Combining the aging calibration data, a locally reserved projection-convolutional neural network (LPP-CNN) model is established to to extract the characteristic bands of aging surface and provide a way to accurately evaluate surface UV aging degree of insulators. The model has a high resolution of aging degree, which provides a new idea and theoretical basis for realizing non-contact non-destructive online detection of surface aging under ultraviolet light.

Concrete Multi-Type Defect Classification Algorithm Based on MSSMA-SVM.

In order to realize the automatic classification of internal defects for non-contact nondestructive testing of concrete, a concrete multi-type defect classification algorithm based on the mixed strategy slime mold algorithm support vector machine (MSSMA-SVM) was proposed. The concrete surface's vibration signal was obtained using a laser Doppler vibrometer (LDV) for four classification targets for no defect, segregation, cavity, and foreign matter concrete classification targets. The wavelet packet transform (WPT) decomposes the detected signals to get information on different frequency bands. The energy ratio change rate, energy ratio, and wavelet packet singular entropy of each node after the WPT were used as the feature input of MSSMA-SVM. The experimental results show that the designed MSSMA-SVM classifier can accurately detect the type, which provides a practical algorithm for classifying concrete defects by laser vibration measurement.

Self-reference Lock-in Thermography for Detecting Defects in Metal Bridge Spans

Introduction. Incipient fatigue damage in the metal superstructures of bridges creates certain threats to the safety of operation. Various methods of non-destructive testing are used for their timely detection and diagnosis. A modern and popular on-the-day solution is the method of infrared (IR) thermography. Due to the specifics of the operation of IR cameras, additional processing of recordings received from these cameras is required to obtain an accurate result. This work aims at presenting a method for processing thermofilms and describing the possibilities of its application under real conditions.Materials and Methods. A method for processing thermographic films was described. It provided detecting temperature anomalies using only information from the camera. The results of its application on the elements of existing metal bridge spans are presented.Results. It is shown that there are temperature anomalies for existing defects. This means that the defects continue to develop, which was confirmed by subsequent observations of their condition. In addition, a case of temperature anomaly in the defect-free external region was identified. This might be a sign of an incipient defect that could not be diagnosed by other methods. If the presence of this defect is confirmed during repeated examinations, it will be possible to diagnose hidden defects that have not yet come to the surface, and/or detect potentially collapsing places.Discussion and Conclusions. The IR thermography performance as a method of non-contact non-destructive testing is shown, as well as its operability on real objects under random load.

Terahertz Non-Destructive Testing and Imaging of High-Voltage Cables

The evaluation of the internal defects in high-voltage cross-linked polyethylene cables is highly crucial for the security and reliability of power transmission. Here, a terahertz (THz) frequency-modulated-continuous-wave non-destructive testing (NDT) imaging system is used to demonstrate the non-contact detection of a high-voltage cable (35 KV). Combined with linear scanning and axial rotation, the three-dimensional (3D) data of the columnar target is acquired, and a 3D perspective image is reconstructed. The correspondence between the target in the real space and image space is determined to accurately show the internal spiral structure and strand number of metal wires. The results indicate that prefabricated air and water holes in the polyethylene insulation layer can be displayed. Furthermore, feature defect signals are automatically classified and recognised by combining the principal component analysis dimension reduction method and the support vector machine classification method, which can predict abnormal defects more efficiently in mass data. These results provide technical guidance for the non-contact NDT and visual evaluation of the internal state of detected cable targets.

Автоматизована система безконтактного ультразвукового неруйнівного контролю якості корпусів ракетних двигунів твердого палива з композиційних матеріалів

Currently, in various industries (engineering, aircraft, energy, etc.) the issue of product quality assurance and control is particularly acute. This is due primarily to the ever-increasing requirements for increasing reliability with increasing loads on products, which entails the strengthening of technical standards. The issue of quality control for rocket and space technology products is especially relevant. Modern power structures of rocket and spacecraft made of polymer composite materials, and especially the body of solid fuel rocket engines (SFRЕ), are multilayer packages of various polymer-composite materials (PKM), obtained and interconnected in the process of manufacturing the body. The efficiency of SFRЕ depends on the quality of the formation of PKM in production conditions. The most important issues are the implementation of production quality control of composite structures, the reliability of control results and the ability to automate the control process. The article presents an automated system of non-contact ultrasonic non-destructive testing, which allows to control the stability of the technological process of forming the composite material of the wall of the SFRЕ body and, if necessary, to adjust it. The probability of detecting zones of anomalous violation of the integrity of the wall material of the SFRЕ housing is carried out due to adaptive algorithms, digital systems of multilevel matrix processing and optimal filtering of the received signals. The automated system of contactless ultrasonic non-destructive quality control of SFRЕ cases allows to register conditions of scanning and control for more visual representation of the defectogram in the expanded look of the case of a product in the course of control and at documentation of its results. The presented results of work on the development of an automated system of non-destructive testing of the integrity of the buildings of the SFRЕ type "cocoon" confirm the possibilities of practical implementation in production.

Non-contact harmonic magnetic field detection for parallel steel pipeline localization and defects recognition

A novel detection method and targets signal extraction algorithm for parallel steel pipeline localization and defects recognition based on harmonic magnetic field are proposed. An orthogonal vector differential focusing array detector was designed, which radiates high-frequency (HF) and ultra-low-frequency (ULF) electromagnetic waves to pipeline based on the principle of Frequency Modulated Continuous Wave (FMCW), and records the signals in parallel using high-sensitivity Tunnel Magneto Resistance (TMR) array sensors. The joint signal pre-processing algorithm of Combination Morphological Pulse Elimination (CMPE) and Quantum Genetic Gaussian Potential Stochastic Resonance (QGGPSR) is proposed to improve signal quality by adaptively eliminating random pulse and noise. The time–frequency analysis algorithm Complementary Ensemble Local Mean Decomposition (CELMD) is used to decompose the pipeline defects signal in detail, and the appropriate components are selected and fused into a correlation array signal cluster. Finally, the targets signal are separated by Limited-memory BFGS Independent Component Analysis (L-BFGS-ICA) based on machine learning optimization to enhance their legibility. The magnetic dipole harmonic simulation model and the 20# steel parallel pipeline experimental platform are established, and compared with the passive detection method to verify the effectiveness and practicality of the proposed method. The results show that this method can accurately locate parallel pipelines and detect different kinds of defects in noisy environment, which is of great significance for the application of non-contact Non-Destructive Testing (NDT) in practical engineering.

Лабораторный стенд для разработки метода и системы непрерывного бесконтактного неразрушающего контроля технического состояния изоляционного оборудования

Measurement of partial discharges (PD) is a generally accepted method of diagnosing the insulation of electrical equipment worldwide. Today, the trend is to move from conventional offline testing to online monitoring to predict the service life of insulation. For testing and calibration of the developed new methods with the contact method, a laboratory stand has been developed in accordance with GOST R 55191-2012 (IEC 60270:2000). The article suggests the use of acoustic and electromagnetic methods for a system of continuous non-contact non-destructive testing of the technical condition of insulation equipment, which will allow monitoring insulation equipment online and predicting its residual life. On their basis, a system of «on-line» diagnostics of high-voltage insulators has been developed.

Narrow band photoacoustic lamb wave generation for nondestructive testing using candle soot nanoparticle patches

The generation of ultrasonic surface waves with a photoacoustic-laser-source has become useful for the noncontact nondestructive testing and evaluation (NDT&E) of materials and structures. In this work, a hybrid ultrasound based NDT&E method is proposed based on the photoacoustic-laser-source as a noncontact Lamb wave generator by incorporating a line-arrayed patterned candle soot nanoparticle-polydimethylsiloxane (CSNPs-PDMS) patch as the signal amplifier and with a narrow bandwidth. The CSNP-PDMS composite has been investigated as the functional patch for its laser energy absorption efficiency, fast thermal diffusion, and large thermoelastic expansion capabilities. The signal amplitude (in mW) from the CSNP-PDMS patch exhibits 2.3 times higher amplitude than the no patch condition and a narrower bandwidth than other conditions. Furthermore, improvement in the sensitivity is also achieved through the selection of the aluminum nitride sensing system. The overall combination of the Lamb wave generation and receiver-sensing system in this study is found to be very promising for a broad range of noncontact NDT&E applications.

Investigating vibration characteristics of magnetostrictive transducers for air-coupled ultrasonic NDT of composites

In this study, high-power ultrasonics has been used for non-contact nondestructive testing of composites. Air-coupled magnetostrictive ultrasonic transducers provide reasonable amplitudes of horn oscillations even if this type of ultrasonic stimulation is close to the idle mode. Four types of ultrasonic horns have been designed and manufactured in order to choose an optimal horn configuration. For each horn, the dependence of vibration amplitude on ultrasonic unit power has been found to exhibit a good match between the theoretical and experimental results. The resonance frequencies and amplitudes of oscillatory velocity were experimentally evaluated by using the technique of scanning laser vibrometry and modeled by means of the Autodesk Inventor software. An air-coupled magnetostrictive transducer, in conjunction with an optimized horn, has been used in the evaluation of impact damage in a graphite epoxy composite and detection of water and excessive epoxy adhesive in an aviation honeycomb panel. It is expected that the technique of air-coupled ultrasonics may be useful for inspecting thin, fragile and hydrophilic materials.

Impact damage assessment in biocomposites by micro-CT and innovative air-coupled detection of laser-generated ultrasound

The increasing use of natural fibre composites in at least semi-structural applications along with a demand for a fast and accurate damage detection for quality purpose and in-service reliability promote a need for non-contact non-destructive testing techniques. To this purpose, ultrasound is probably one of the most widely used testing techniques but the need of a coupling fluid like water limits its use with natural fibre composites. In this work, a novel non-contact set-up based on laser excitation of ultrasound and detection with a broadband, air-coupled optical microphone is presented and tested on flax/PLA laminates. This material system has been characterized in terms of quasi-static mechanical properties and low velocity impact response. The outcomes of this study demonstrate the potential of this non-contact and nondestructive system for quality and damage inspection purposes of natural fibre composites.

A Temperature Drift Compensation Method for Pulsed Eddy Current Technology.

Pulsed eddy current (PEC) technology is another important non-contact nondestructive testing technology for defect detection. However, the temperature drift of the exciting coil has a considerable influence on the precision of PEC testing. The objective of this study is to investigate the temperature drift effect and reduce its impact. The temperature drift effect is analyzed theoretically and experimentally. The temperature drift effect on the peak-to-peak values of the output signal is investigated, and a temperature compensation method is proposed to reduce the effect of temperature variation. The results show that temperature drift has a negative impact on PEC testing and the temperature compensation method can effectively reduce the effect of temperature drift.

Research advances in eddy current testing for maintenance of carbon fiber reinforced plastic composites

This paper presents the overview of previous studies on the eddy current testing of Carbon Fiber Reinforced Plastic (CFRP) composites. CFRP is composed of many unidirectional carbon fiber/epoxy plies stacked together, thus it has laminated structure and inhomogeneous nature. Eddy Current Testing (E CT) is an efficient and non-contact Nondestructive Testing (NDT) technique for conductive materials. The electrical conductivity of carbon fibers can be utilized by ECT system for fiber texture mapping and detection of defects that can cause the conductivity change. Recently a lot of attention has been paid to the electromagnetic properties characterization of CFRP material, fiber texture and defect detection, as well as the ECT technique enhancement. In this paper we will give the detailed information and results of these research works. In addition this paper also summarizes the available numerical simulation methods for the electromagnetic modeling of CFRP materials, and the calculation of eddy currents and ECT signals.

FINITE ELEMENT ANALYSIS OF THERMOGRAPHY TECHNIQUE FOR DEFECT IDENTIFICATION IN CONCRETE SLAB

Non-destructive evaluation is an area of focussed research around the world. Through non-destructive evaluation it is aimed at evaluating the integrity of concrete and identify the location of defects like voids and honeycombs. While most of these methods rely on wave propagation, the infrared thermography technique uses heat conduction principles to identify defects at shallow depth. The infrared thermography technique is a non-contact non-destructive testing technique which makes it possible to evaluate the test medium independent of its surface characteristics. Also, the ability of the infrared thermography camera to capture and assess a surface area at every time instant makes it an interesting technique to pursue research on. In the present work, it is proposed to examine the possibility of defect identification using the infrared thermography technique by employing the finite element analysis. For this study, two case studies have been carried out. For the analysis a standard commercial FEM package has been used and the heat transfer analysis is carried out using ten node tetrahedron elements by incorporating the thermal properties. Heat is applied from one surface and the evaluation is carried out from the same surface. Encouraging results have been obtained on the application of the thermography method. In the present study, it has been observed that the thermography method could be effectively applied for large defect identification up to a depth of 90mm from the investigating surface.

Design and Simulation of 100 kHz and 200 kHz Tri-Phasic PZT Piezoelectric Transducers

This work reports the simulation and measurements results of Tri-Phase piezoelectric transducers unprecedented geometries composed of PZT-5H rods surrounded by hexagonal polymer walls in a vacuum ambient. The electrical and mechanical characteristics of these transducers are simulated, predicted and compared to that of physical design. The measured piezoelectric properties of the 100 kHz and 200 kHz fabricated transducer are found to be very much in agreement with those of the physical design. The simulation of the designed transducer was expected to have acoustic energy channeled in the d33 mode at resonance, with weak or no shear mode cross talk behavior from the other modes. The mechanical displacements measured were large and highly aligned along d33 mode. Transducer resonance behavior was measured, compared and in agreement to that of simulation. This implies that Tri-Phasic piezoelectric transducers model perform as a finite tool to design single device transducers with improved mechanical and electrical response. Such designed transducers can be highly useful for the noncontact Non-Destructive Evaluation (NDE) and Non-Destructive Testing (NDT) with high resolution and greater depth profile of various types of material studies. Thus using several design parameters variables new transducers with desirable features can be produced for wide range of applications.

A method based on SVD for detecting the defect using the magnetostrictive guided wave technique

Magnetostrictive guided wave testing is a useful non-contact nondestructive testing method. However the signal to noise ratio (SNR) of its testing signal is low due to the lift-off. In this paper, a novel index called singular decreasing index (SDI) is proposed to distinguish the defect signal, which is based on a new matrix form improved from the Hankel matrix and the singular value decomposition (SVD). Further, an SDI spectrum is proposed to locate defects. Simulation signals with different SNR are employed to evaluate the performance of this method, and results show that the SDI spectrum can locate the defect at a very low SNR. Experimental results also show the excellent performance of the SDI spectrum in defect location. Hence, it is believed that this method can effectively detect defects at low SNR.

Characterisation of inclusions and disbonds in honeycomb composites using non-contact non-destructive testing techniques

Characterisation of inclusions and disbonds in honeycomb composites using non-contact non-destructive testing techniques