Excitation and Detection of Shear Horizontal Waves with Electromagnetic Acoustic Transducers for Nondestructive Testing of Plates

The fundamental shear horizontal（SH0） wave has several unique features that are attractive for long-range nondestructive testing（NDT）. By a careful design of the geometric configuration, electromagnetic acoustic transducers（EMATs） have the capability to generate a wide range of guided wave modes, such as Lamb waves and shear-horizontal（SH） waves in plates. However, the performance of EMATs is influenced by their parameters. To evaluate the performance of periodic permanent magnet（PPM） EMATs, a distributed-line-source model is developed to calculate the angular acoustic field cross-section in the far-field. Numerical analysis is conducted to investigate the performance of such EMATs with different geometric parameters, such as period and number of magnet arrays, and inner and outer coil widths. Such parameters have a great influence on the directivity of the generated SH0 waves that arises mainly in the amplitude and width of both main and side lobes. According to the numerical analysis, these parameters are optimized to obtain better directivity. Optimized PPM EMATs are designed and used for NDT of strip plates. Experimental results show that the lateral boundary of the strip plate has no perceivable influence on SHO-wave propagation, thus validating their used in NDT. The proposed model predicts the radiation pattern ofPPM EMATs, and can be used for their parameter optimization.

Nondestructive Testing and Characterization of Residual Stress Field Using an Ultrasonic Method

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.

Statistical analysis of nondestructive testing results of cast steel joints in civil engineering structures

To study the distribution law and random characteristics of casting defects in steel castings,24 civil engineering structural cast steel joints were divided into two groups:simple cast steel joints and complex cast steel joints.Three kinds of nondestructive testing(NDT)methods,namely,visual,magnetic particle,and ultrasonic inspections,were used to detect the macroscopic defects in joints.The NDT results were then statistically analyzed.The results show that the unfused core support is a common defect of complex cast steel joints,and the defect can be seen visually,so excavation and repair welding should be carried out before castings leave factories.Casting cracks are extremely likely to occur in the intersection area of tubes,which is called the ultrasonic inspection blind zone.The occurrence probability of gas pores on simple cast steel joints is the largest,and the occurrence probability of core support incomplete fusions on complex cast steel joints is the largest.However,when cast steel joints are counted as a whole sample,the occurrence probability of gas pores is larger than that of core support incomplete fusions.Therefore,it is the most common defect in cast steel joints.

Nondestructive testing method of wood moisture content based on a planar capacitance sensor model

For our research, a new hybrid experimental-computational method is presented. We applied a least squares fitting method （LSFM） to reconstruct the wood moisture content （WMC） from the data measured with a planar capacitance sensor. A boundary element method （BEM） was used to compute the relationship between capacitance and the dielectric constant. A functional relationship between MC and the dielectric constant was identified by LSFM. The agreement of this final computation result with the experimental data indicates that this method can be used to estimate the WMC quickly and effectively with engineering analysis. Compared with popular statistical methods, a large number of experiments are avoided, some costs of testing are reduced and the efficiency of testing is enhanced.

Recent developments in photoacoustic imaging and sensing for nondestructive testing and evaluation

Photoacoustic(PA)imaging has been widely used in biomedical research and preclinical studies during the past two decades.It has also been explored for nondestructive testing and evaluation(NDT/E)and for industrial applications.This paper describes the basic principles of PA technology for NDT/E and its applications in recent years.PA technology for NDT/E includes the use of a modulated continuous-wave laser and a pulsed laser for PA wave excitation,PA-generated ultrasonic waves,and all-optical PA wave excitation and detection.PA technology for NDT/E has demonstrated broad applications,including the imaging of railway cracks and defects,the imaging of Li metal batteries,the measurements of the porosity and Young’s modulus,the detection of defects and damage in silicon wafers,and a visualization of underdrawings in paintings.

RAPID NONDESTRUCTIVE TESTING OF HEAT-TREATMENT QUALITY OF 2014 ALUMINIUM ALLOY

１ＩＮＴＲＯＤＵＣＴＩＯＮＳｉｎｃｅｔｈｅｐａｐｅｒ“Ｒａｐｉｄ，ＮｏｎｄｅｓｔｒｕｃｔｉｖｅＡｎｄＱｕａｎｔｉｔａｔｉｖｅＴｅｓｔｉｎｇｏｆＨａｒｄｎｅｓｏｆＡｌｕｍｉｎｉｕｍａｌｏｙｓ”ｗａｓｐｕｂｌｉｓｈｅｄ［１］，ｍａｎｙｒｅａｄｅｒｓｈａ...

Ultrasonic Nondestructive Testing of Superplastic Solid-State Welding Joint for Different Steels

Based on quantitative microscopic examinations of welds and welding rate for different steels(40Cr and T10A) joint,which possess the ultra-fine microstructure after high frequency hardening(HFH) and salt-bath cyclic quenching(SCQ),the suitable defect grey scale threshold value was determined,and the welding rate of superplastic solid-state welding of different steels(40Cr and T10 A steel) was systematically inspected and analyzed by means of self-made ultrasonic imaging inspection system.The experimental results showed that the superplastic solid-state weld of different steels can be inspected more accurately,reliably and quickly by this system,and the results were in good accordance with that of metallographic observation.The welding rate of superplastic welding is in linear relation with tensile strength of joint.

Nondestructive testing for crack of tunnel lining using GPR

Lining craze, as a common engineering damage, affects the bearing capacity and the safety of tunnels.To improve the capabilities of the surface crack detection in the tunnel lining, ground penetrating radar(GPR) was employed. The principle and method of GPR for cracks investigation of tunnel lining were expounded. As an application example, some field measurements in order to detect the depth of cracks for the tunnel lining were achieved in a new tunnel. All GPR investigations were made with the antennae of 1 GHz. The cracks of concrete structure were located, and the distributing and depth of cracks are inspected and estimated by GPR. The results of investigation show GPR is accurate and efficient to detect cracks of tunnel lining.

Investigation of Eddy Current Nondestructive Testing for Carbon Fiber-Reinforced Plastic （CFRP） Based on Electromagnetic Field Analysis

CFRP （carbon fiber reinforced plastic） is used extensively in aircraft and spacecraft structures, because of its excellent mechanical properties. Ultrasonic testing, which is used as a non-destructive testing technique for CFRP, requires a contact medium. In contrast, eddy current testing does not require a contact medium, and when used for CFRP testing it has advantages not available with other techniques. CFRP is a laminate, with each layer being anisotropically conductive, and the distribution of the induced eddy current is yet to be determined. Here, to determine the eddy current distribution in the detection of flaws in cross-ply CFRP （0°/90°） by using a cross-point probe, we performed an FEM （finite element method） analysis of electromagnetic fields. We investigated the nature of the flaw signals and the differences in eddy current distributions between materials with and without flaws.

Correction to: Recent developments in photoacoustic imaging and sensing for nondestructive testing and evaluation

Following publication of the original article[1],the authors identified an error in the article title.The first word ‘Review’ is added mistakenly by the typesetter.

Development and application of WGQ type micro-computer-based electromagnetic nondestructive testing instrument for quality of metal material

The WGQ type micro computer based electromagnetic nondestructive testing instrument for quality of metal material was developed on the principle of electromagnetic induction. The invention and marketing of the WGQ instrument has solved the world wide tough problem of the "N" shape relation between the indicated values of testing instruments and the hardness of most metal parts, particularly steel and iron parts. It has also greatly improved the hardness testing precision of aluminium alloy. Consequently the instrument can accurately perform either the quantitative testing of aluminium alloy, steel and iron parts hardness or the qualitative testing of their internal and external defects such as cracks, over burnt and so on. Its hardness testing precision is HRB±0.7, HRC±1 and HB±10. The testing speed can reach 1 500 parts per hour. The instrument has already been successfully applied to the spot of lots of factories.

Rolling contact fatigue nondestructive testing system for a bearing inner ring based on initial permeability

Due to the fact that rolling contact fatigue is not easily detected, and residual life is not easily evaluated in the early stage of bearing life, a nondestructive testing method based on initial permeability is proposed. By analyzing the crack propagation mechanism, a fatigue state detection system based on differential signals is designed. A simulation model of the detection of the inner ring of the pulse signal is established by using the electromagnetic field simulation software. The effects of the height of the coil, the inner and outer diameter, the number of coil turns, the diameter and the height of the ferrite core of the probe on the differential value of the detection signal are simulated. The parameter combination of the maximum difference value of the signal is used as the structural size of the sensor, and the detection sensor is designed and fabricated. Moreover, the bearing fatigue test system is designed, and the bearing is tested. The results show that the system has good detection ability for rolling contact fatigue and verifies the mechanism and trend of crack propagation in the inner ring of the bearing.

Monitoring of polymeric membrane fouling in hollow fiber module using ultrasonic nondestructive testing

This study describes the development of novel protocols extending the real-time ultrasonic reflectometry(UTDR) for the detection of membrane fouling in hollow fiber module during ultrafiltration(UF) of oily water treatment. A specially designed acoustic sensor with a frequency of 2.5 MHz was used. The hollow fiber membranes used were polysulphone(PSf) UF membranes with MWCO 40 kDa. The wastewaters with three different oily concentrations of 100, 500 and 1 000 mg/L were investigated. Diesel oil was utilized as the primary foulant. The results show that the permeate flux declines with operation time and its value becomes lower with the increase of the oily concentration in wastewater. It is found that ultrasonic measurement can detect the fouling and cleaning processes. A new signal analysis protocol-ultrasonic reflected energy was developed. Ultrasonic reflected energy obtained indicates the deposition of oily layer as a function of operation time and its removal after cleaning. The overall flux decline is reasonably correlated with the changes in ultrasonic reflected energy. This research provides the evidence that the ultrasonic reflectometry technique is capable of monitoring membrane fouling and cleaning in hollow fiber modules.

NUMERICAL SIMULATION OF ULTRASONIC NONDESTRUCTIVE TESTING FOR WELDS

A computer simulation technique for ultrasonic propagation is utilized for the simulation of ultrasonic nondestructive testing (NDT). In this paper, one goal of the simulation is to compute ultrasonic field radiated by arbitrary transducers into pieces under examination. The other simulates a testing experiment. The simulation approach is based on the model for the computation of the ultrasonic field in isotropic media radiated from actual NDT transducers. After the field is known, remaining to be modeled is the interaction between this field and the scatters (defect) and the echo structure. The model of beam-defect interaction is based on the Kirchhoff’s diffraction approximations theory applied to elastodynamics. We assumed that the incident wave fronts on the defect are plane in the case of a focused immersed transducer and material is isotropic and homogeneous. The simulating results demonstrate that the model in ultrasonic NDT of welds is practical in further research and useful in optimizing testi

Nondestructive testing and assessment of consolidation effects of earthen sites

Earthen sites are widely distributed throughout China, and most of them belong to archaeological sites with significant values, which not only directly witness the origin, formation and development of Chinese civilization, but also possess important values for conservation and exhibition. Many researches and practices on their conservation and consolidation have been carried out; however, the consolidation effect is mainly judged by visual observation and expert evaluation. Scientific assessment of conservation and consolidation effects is a challenging issue. Many instruments in other fields cannot be directly applied to the conservation of cultural relics due to their peculiarity. In order to assess the effects of field conservation experiments, this paper tries to understand the consolidation effects at Liangzhu site using nondestructive or micro-damage methods, including thermo-physical parameters testing, infrared thermal imaging, high-density microelectrode resistivity testing, portable microscope observation, and hydrophilic and hydrophobic testing, and thereby explores the practicable methods for evaluating the properties of consolidation materials for earthen sites treatment.

Failure characterization of fully grouted rock bolts under triaxial testing

Confining stresses serve as a pivotal determinant in shaping the behavior of grouted rock bolts.Nonetheless,prior investigations have oversimplified the three-dimensional stress state,primarily assuming hydrostatic stress conditions.Under these conditions,it is assumed that the intermediate principal stress(σ_(2))equals the minimum principal stress(σ_(3)).This assumption overlooks the potential variations in magnitudes of in situ stress conditions along all three directions near an underground opening where a rock bolt is installed.In this study,a series of push tests was meticulously conducted under triaxial conditions.These tests involved applying non-uniform confining stresses(σ_(2)≠σ_(3))to cubic specimens,aiming to unveil the previously overlooked influence of intermediate principal stresses on the strength properties of rock bolts.The results show that as the confining stresses increase from zero to higher levels,the pre-failure behavior changes from linear to nonlinear forms,resulting in an increase in initial stiffness from 2.08 kN/mm to 32.51 kN/mm.The load-displacement curves further illuminate distinct post-failure behavior at elevated levels of confining stresses,characterized by enhanced stiffness.Notably,the peak load capacity ranged from 27.9 kN to 46.5 kN as confining stresses advanced from σ_(2)=σ_(3)=0 to σ_(2)=20 MPa and σ_(3)=10 MPa.Additionally,the outcomes highlight an influence of confining stress on the lateral deformation of samples.Lower levels of confinement prompt overall dilation in lateral deformation,while higher confinements maintain a state of shrinkage.Furthermore,diverse failure modes have been identified,intricately tied to the arrangement of confining stresses.Lower confinements tend to induce a splitting mode of failure,whereas higher loads bring about a shift towards a pure interfacial shear-off and shear-crushed failure mechanism.

Unbound^(28)O,the heaviest oxygen isotope observed:a cutting-edge probe for testing nuclear models

The beyond-dripline oxygen isotopes^(27,28)O were recently observed at RIKEN,and were found to be unbound decaying into^(24)O by emitting neutrons.The unbound feature of the heaviest oxygen isotope,^(28)O,provides an excellent test for stateof-the-art nuclear models.The atomic nucleus is a self-organized quantum manybody system comprising specific numbers of protons Z and neutrons N.

A Kind of Potential Practical Sensors of Metamaterial in Electromagnetic Flaw Nondestructive Testing

We present a new kind of method of electromagnetic flaw nondestructive testing with coating of metamaterials and simulation near electromagnetic field property for test crack. The simulation of improving a Nondestructive testing (NDT) probe electromagnetic radiant property by Metamatrials (MMs) covering a tiny current element is investigated and analyzed using Ansoft HFSS based on finite element method (FEM), which permittivity and permeability are negative. Electromagnetic model: Ideal MMs ball shell with inner radius of 1 mm and outer radius variation, and the shell’s relative permittivity and relative permeability are all –3.0, dielectric loss tangent and magnetic loss tangent are all 0.1;and exciting current element length is with 0.3 mm, diameter 0.2 mm, value 1 mA at frequency 10 GHz;and simulation is with radiation boundary conditions. The simulating near electromagnetic field variety with ratio of inner radius and out radius, and so near or local field of MMs sensor on a surface crack, as well as comparing near field value of sensor with coating common material are finished. Results can be seen that MMs film sensor near electromagnetic field and radiation properties are obviously better than other two kinds of structures without coating medium and coating with common medium, and Metamaterial may be opened out some new kinds of sensors in electromagnetic flaw nondestructive testing for potential practical applications in future.

Electrochemical biosensors for point-of-care testing

Point-of-care testing(POCT)is the practice of diagnosing and monitoring diseases where the patient is located,as opposed to traditional treatment conducted solely in a medical laboratory or other clinical setting.POCT has been less common in the recent past due to a lack of portable medical devices capable of facilitating effective medical testing.However,recent growth has occurred in this field due to advances in diagnostic technologies,device miniaturization,and progress in wearable electronics.Among these developments,electrochemical sensors have attracted interest in the POCT field due to their high sensitivity,compact size,and affordability.They are used in various applications,from disease diagnosis to health status monitoring.In this paper we explore recent advancements in electrochemical sensors,the methods of fabricating them,and the various types of sensing mechanisms that can be used.Furthermore,we delve into methods for immobilizing specific biorecognition elements,including enzymes,antibodies,and aptamers,onto electrode surfaces and how these sensors are used in real-world POCT settings.