Non-destructive Measurement Technique Research Articles

Non-destructive thickness measurement of thermal barrier coatings using terahertz radiation

A non-destructive thickness measurement technique based on terahertz (THz) reflectivity was successfully deployed to interrogate 7 wt.% yttria-stabilised zirconia thermal barrier coatings (TBCs) produced by electron-beam physical vapour deposition (EB-PVD). The THz technique was shown to produce accurate thickness maps for different samples with a resolution of 1 × 1 mm over a surface of 65 × 20 mm that were compared with direct examination of key cross-sections. All thickness measurements on different samples were calculated using a single value of refractive index. Small defects characteristic of EB-PVD, such as “carrot growths” and variations on column inclination, were evaluated and did not produce significant variations in the refractive index of the TBC. Moreover, the thickness maps correctly display thickness variations that are a consequence of the point-source nature of EB-PVD evaporation. In summary, this paper demonstrates the technique can be successfully deployed on large surfaces, and across different coatings of the same material produced under the same deposition conditions. It is shown that a single n value is required to map the thickness distribution for all samples. This combination of qualities indicates the potential of the technique for in-line control of TBC manufacture.

Feasibility of Using Non-Destructive Ultrasound Measurement Technique to Evaluate Binder Content of Asphalt Mixtures

The non-destructive ultrasound technique is an easy and inexpensive technique widely used in industry to evaluate the properties of engineering materials. Despite its popularity in industrial applications, such as evaluating steel materials, the ultrasound technique has not been thoroughly investigated for the purpose of characterizing asphalt materials in general, nor specifically determining the asphalt binder content of asphalt mixtures. The purpose of this study was to explore the feasibility of utilizing measurements based on the non-destructive ultrasound technique to detect changes in the asphalt binder content in asphaltic mixture specimens. Two performance-grade binders, PG64-28 and PG76-22, and two rubber-modified binders were selected. The rubber-modified binders were produced by adding crumb rubber to the two performance-grade binders, PG64-28 and PG76-22, and were designated as PG64-28R and PG76-22R. The amount of crumb rubber added to these rubber-modified binders was 15% by weight of the PG64-28 and PG76-22 binders. The aggregate gradations for all of the asphalt mixtures were the same. The asphalt mixture specimens were used to obtain measurements for: (1) the ultrasound wave speed through the specimens; and (2) and the integrated response (IR) of the specimens. The results indicated that, generally, the ultrasound wave speed decreases with an increase in binder content. This is expected due to the binder’s attenuation and slowing effect on the wave speed. The results also indicated that, generally, the integrated response (IR) decreases with an increase in binder content. This can be explained by the fact that the increased binder content in asphalt mixture specimens increases their tendency to absorb more energy.

A novel non-destructive technique for qualitative and quantitative measurement of dental erosion in its entirety by porosity and bulk tissue-loss

ObjectiveTo explore the potential of combining non-contact profilometry (NCP) and confocal laser scanning microscopy (CLSM) data to measure the entire erosive process non-destructively and to validate findings using inductively coupled plasma-atomic emission spectroscopy (ICP-AES), scanning electron microscopy (SEM) and surface microhardness (SMH) using the same samples throughout. MethodsPolished bovine enamel samples (n = 35) were divided into groups (7/group) with similar SMH values. Samples underwent individual erosive challenges (1 % citric acid, pH3.8) for 1, 5, 10, 15 or 30 min under stirring and aliquot extracts were analysed for Ca and P by ICP-AES. SMH was used to measure erosive softening. Profilometry was used to assess bulk volume loss (BVL). Images were captured by SEM. Samples were stained with rhodamine-B (0.1 mM, 24 h) and images captured by CLSM. Image processing was used to determine changes in fluorescent volume for the first 10 μm (ΔFV10) for each enamel sample which were combined with BVL to calculate total lesion volume (TLV). ANOVA, linear regression and Pearson correlation analysis were used where applicable. ResultsSurface softening, [Ca], [P], BVL and ΔFV10μm increased with acid erosion duration which were significant by 10 min (P < .01). The Ca:P ratio increased to 1.57 then decreased after 5 min erosion suggesting a sub/surface phase change, which was observed by SEM and CLSM showing significant changes to the enamel surface and subsurface morphology with time. Combination of BVL and ΔFV10 as TLV strengthened the significant correlations with [Ca], [P], and SMH (P < .01). ConclusionThis novel combination of CLSM and NCP allows for concurrent non-destructive quantification of the entire erosive process by mineral loss, and qualitatively characterise microstructural changes during dental erosion.

Novel Nondestructive Biosensors for the Food Industry.

An increasing number of foodborne outbreaks, growing consumer desire for healthier products, and surging numbers of food allergy cases necessitate strict handling and screening of foods at every step of the food supply chain. Current standard procedures for detecting food toxins, contaminants, allergens, and pathogens require costly analytical devices, skilled technicians, and long sample preparation times. These challenges can be overcome with the use of biosensors because they provide accurate, rapid, selective, qualitative, and quantitative detection of analytes. Their ease of use, low-cost production, portability, and nondestructive measurement techniques also enable on-site detection of analytes. For this reason, biosensors find many applications in food safety and quality assessments. The detection mechanisms of biosensors can be varied with the use of different transducers, such as optical, electrochemical, or mechanical. These options provide a more appropriate selection of the biosensors for the intended use. In this review, recent studies focusing on the fabrication of biosensors for food safety or food quality purposes are summarized. To differentiate the detection mechanisms, the review is divided into sections based on the transducer type used.

Soil restraint on buried pipelines during oblique relative movements in sand

Soil restraints associated with relative soil-pipe movements is an important consideration for stability assessment of buried pipelines. This paper investigates the effects of pipe surface roughness, inclination angle within the horizontal-vertical plane and embedment ratio on the development of soil restraint on shallow pipes in sand. In total, 24 model tests were performed, using an image-based non-destructive soil deformation measurement technique. The failure and deformation mechanisms during oblique pipe movements were discussed based on image analysis results. The test results were then used to verify the Finite Element Limit Analysis (FELA) model, by which a parametric study on the peak soil restraint in a wider range of soil and pipe parameters was carried out. It is shown that the peak soil restraint increased with greater pipe embedment ratio, inclination angle of movements to the vertical and sand-pipe interface frictional strength because of a larger range of soil was mobilised, and the effects of these factors reduced at deeper depths. To account for the effects of oblique movements on the peak resistance received by pipelines in sand, an analytical relationship is presented and examined based on the test and simulation results.

Radiographic Visibility Limit of Pores in Metal Powder for Additive Manufacturing

The quality of additively manufactured (AM) parts is determined by the applied process parameters used and the properties of the feedstock powder. The influence of inner gas pores in feedstock particles on the final AM product is a phenomenon which is difficult to investigate since very few non-destructive measurement techniques are accurate enough to resolve the micropores. 3D X-ray computed tomography (XCT) is increasingly applied during the process chain of AM parts as a non-destructive monitoring and quality control tool and it is able to detect most of the pores. However, XCT is time-consuming and limited to small amounts of feedstock powder, typically a few milligrams. The aim of the presented approach is to investigate digital radiography of AM feedstock particles as a simple and fast quality check with high throughput. 2D digital radiographs were simulated in order to predict the visibility of pores inside metallic particles for different pore and particle diameters. An experimental validation was performed. It was demonstrated numerically and experimentally that typical gas pores above a certain size (here: 3 to 4.4 µm for the selected X-ray setup), which could be found in metallic microparticles, were reliably detected by digital radiography.

Nondestructive measurements of depth distribution of carrier lifetimes in 4H-SiC thick epitaxial layers using time-resolved free carrier absorption with intersectional lights.

To achieve low on-state and switching losses simultaneously in SiC bipolar devices, the depth distribution of the carrier lifetime within the voltage blocking layer and the techniques used for observing the carrier lifetime distribution are important considerations. We developed a measurement system of the time-resolved free carrier absorption with intersectional lights (IL-TRFCA) for the nondestructive measurements of the depth distribution of the carrier lifetime in 4H-SiC thick epilayers. To confirm the reliability of the measurement results, we also performed TRFCA measurements to the cross section of the samples. As a result, although the lifetimes are underestimated owing to an inevitable diffusion of the carriers from the measurement region, the system was able to observe a carrier lifetime distribution up to a depth of 250 μm. Our IL-TRFCA system demonstrated a depth resolution of ∼10 μm, which is the best resolution among previously reported nondestructive measurement techniques. We consider the proposed system to be useful for the development of SiC bipolar devices.

A Simple, Inexpensive, and Portable Image-Based Technique for Nondestructive Leaf Area Measurements

This new 6-page article, part of a series introducing various image-based measurements for horticultural research, introduces a simple, inexpensive, and portable image-based technique for nondestructive leaf area measurements. It uses an imaging apparatus made with ordinary office supplies to obtain leaf images in greenhouse or field environments. Leaf images are then processed and analyzed to measure leaf area using ImageJ, an open-source image processing program. Because both image capture and analysis are performed nondestructively, leaf area can be measured on the same leaf repeatedly, enabling the monitoring of leaf growth over time, as well as photosynthesis and transpiration. This technique is particularly useful to researchers and students studying leaf growth and physiology in greenhouse or field environments. Written by Shinsuke Agehara, Lillian Pride, Mariel Gallardo, and Jose Hernandez-Monterroza, and published by the UF/IFAS Horticultural Sciences Department.https://edis.ifas.ufl.edu/hs1395

Calibration-free real-time organic film thickness monitoring technique by reflected X-Ray fluorescence and compton scattering measurement

Most thickness measurement techniques using X-ray radiation are unsuitable in field processes involving fast-moving organic films. Herein, we propose a Compton scattering X-ray radiation method, which probes the light elements in organic materials, and a new simple, non-destructive, and non-contact calibration-free real-time film thickness measurement technique by setting up a bench-top X-ray thickness measurement system simulating a field process dealing with thin flexible organic films. The use of X-ray fluorescence and Compton scattering X-ray radiation reflectance signals from films in close contact with a roller produced accurate thickness measurements. In a high-thickness range, the contribution of X-ray fluorescence is negligible, whereas that of Compton scattering is negligible in a low-thickness range. X-ray fluorescence and Compton scattering show good correlations with the organic film thickness (R2 = 0.997 and 0.999 for X-ray fluorescence and Compton scattering, respectively, in the thickness range 0–0.5 mm). Although the sensitivity of X-ray fluorescence is approximately 4.6 times higher than that of Compton scattering, Compton scattering signals are useful for thick films (e.g., thicker than ca. 1–5 mm under our present experiment conditions). Thus, successful calibration-free thickness monitoring is possible for fast-moving films, as demonstrated in our experiments.

New in situ method for the determination of the crystallization kinetics of glass‐ceramics

AbstractAn in situ method for the characterization of the crystallization behavior of glass‐ceramics has been developed, which is based on an acoustic, nondestructive Young's modulus measurement technique according to ASTM E1876. The progression of the crystallization can be measured due to an increasing Young's modulus during the heat treatment, which is a result of the formation of solid precipitations in a viscous melt. The crystalline content can be deduced from the data using a superposition principle for elastic properties. The developed method was evaluated using bar‐shaped bulk glass samples from a lithium‐alumosilicate glass‐ceramic system. The sample geometry, with its low surface‐to‐volume ratio, allowed a detailed analysis of the volume crystallization, due to a reduced influence of the surface crystallization on the measured signal. The development of the crystalline content was confirmed, and variations in the surface and bulk crystallization were examined using a reference method based on X‐ray diffraction.

Enabling new exploration opportunities on planetary surfaces: In situ geochemical characterization in soils by dielectric spectroscopy onboard the AXEL rover system

In the work, we present dielectric spectroscopy (DS) is an analytical method capable of characterizing and quantifying electrochemically active materials (water/ice, ions, etc.) in planetary regoliths. Detection of these materials occurs when a small amount of energy is applied to an in situ sample, causing perturbation in the form of potential kinetic energy and inducing polarization and/or relaxation processes in materials of interest. The frequency dispersion on the electrical properties of impendences, relative permittivity, and conductivity spectra represents chemical and physical properties in association with inherent material properties. Therefore, measuring these energetic states can provide a unique fingerprint of the materials, depending on the frequencies that are scanned. In the case of water content in soils, the Debye equivalent circuit model can accurately predict its electrical properties and provide excellent quantification of the water content in soils.Use of DS is enabled by miniaturization of the key components and the low power requirements. DS is therefore capable of offering substantial scientific returns as an in situ sampling and non-destructive measurement technique, making it ideally suitable for deployment onboard many smaller space exploratory platforms. This work reports the first deployment use of DS from a field test for geochemical characterization of in situ soils, specifically on the quantification of water onboard the AXEL mobility system in the Mojave Desert.Laboratory testing has confirmed the sensitivity of DS with respect to particle size (fine vs coarse) determination as well as water content (down to 0.01 ​wt%) under a wide range of environmental conditions. Water content associated with bound and bulk water was uniquely identified in the soil mixture. We also describe a field demonstration using DS using two distinct insertion dielectric probes specifically design for sub-surface measurements, verifying their mechanical robustness and chemical stability. The field measurements are in good agreement with laboratory data and effectively quantified water content at about 3.0 ​wt% and 8.0 ​wt% for field test sites #1 and #2, respectively.

Determination of spent nuclear fuel parameters using modelled signatures from non-destructive assay and Random Forest regression

Verification of fuel parameters is a central undertaking for nuclear inspectors aiming at verifying the completeness and correctness of operator declarations. Traditionally, such verification is done analysing data from one instrument at a time. Here we present a study based on simulated data from various non-destructive assay measurement techniques applied on modelled PWR nuclear fuel assemblies. The data comprised multiple signatures and were analysed using machine learning algorithms. These signatures included activities from gamma-ray emitting fission product radionuclides, the parametrised early die-away time τ from the prototype Differential Die-away Self-Interrogation (DDSI) instrument, as well as the total Cherenkov light intensity which is directly measurable.The objective of the work is to systematically explore the capability to predict values of the fuel parameters initial enrichment (IE), burnup (BU) and cooling time (CT) independently of operator declarations, using Random Forest regression and modelled pressurised water reactor (PWR) fuel.The results show that passive gamma-ray activities alone can be used to predict IE, BU and CT for CT<20 years, and that by adding a feature proportional to the total gamma-ray activity, the errors in the predictions are significantly reduced. In this work, two measures proportional to total gamma activity have been studied: the sum of all considered gamma-ray intensities, and the total Cherenkov light intensity. From this work it was concluded that for fuels with CTs between 20 and 70 years, CT can be well determined by a multivariate analysis of the activities of 134Cs, 137Cs, 154Eu. For a BU determination, an additional feature corresponding to total gamma activity is required. This is, however, not sufficient to determine IE, which requires inclusion of the neutron signature τ as well.

Two-Dimensional Mapping of Interface Thermal Resistance by Transient Thermal Measurement

Bonded interfaces in power converters add thermal resistances to heat dissipation. Under cyclic power, temperature, or chemical loading, these interfaces degrade, raising the thermal resistances. Reliability of the thermal interfaces is especially problematic when the bonded area is large because the larger the area the more likely it is to have preexisting defects from processing. To help qualifying the development of a bonding process and quantifying the interface reliability, it would be desirable to have a simple, reliable, and nondestructive measurement technique to obtain a 2-D map of the interface thermal resistance across a large bonded area. Based on the transient thermal method of JEDEC standard 51-14, in this article, we develop a measurement technique that involves moving a thermal probe discretely across a large-area bonded substrate and acquiring the thermal interface resistance under the probe at each location. The probe is made by custom-packaging an insulated-gate bipolar transistor (IGBT) power device. An analytical thermal model is developed to gain insights into the effects of probe materials and structural parameters on the sensitivity of the measurement technique. To obtain a 2-D thermal resistance map of a bonded substrate, the probe is thermally coupled to the substrate at one location through a thermal pad or grease; the device is powered up to a steady-state junction temperature; the power is cutoff; and then the junction temperature during cool-down is recorded. The recorded temperature data are analyzed to derive a thermal structure function of the multilayer material stack. The process is repeated at other locations until a 2-D map of the interface thermal resistance across the entire substrate is completed. This technique is demonstrated on copper–copper bonded samples using either a thermal grease or sintered silver. The resolution of the 2-D mapping technique is evaluated by a copper–grease–copper stack with defects implanted at the bond line.

A Nondestructive Eggshell Thickness Measurement Technique Using Terahertz Waves

Eggshells play a number of important roles in the avian and reptile kingdom: protection of internal contents and as a major source of minerals for developing embryos. However, when researching these respective roles, eggshell thickness measurement remains a bottleneck due to the lack of a non-destructive measurement techniques. As a result, many avian and reptile research protocols omit consideration of eggshell thickness bias on egg or embryo growth and development. Here, we validate a non-destructive method to estimate eggshell thickness based on terahertz (THz) reflectance spectroscopy using chicken white coloured eggs. Since terahertz waves are reflected from outer air-eggshell interface, as well as the inner eggshell-membrane boundary, the resulting interference signals depend on eggshell thickness. Thus, it is possible to estimate shell thickness from the oscillation distance in frequency-domain. A linear regression-based prediction model for non-destructive eggshell thickness measurement was developed, which had a coefficient of determination (R2) of 0.93, RMSEP of 0.009, RPD of 3.45 and RER 13.67. This model can estimate eggshell thickness to a resolution of less than 10 μm. This method has the potential to expand the protocols in the field of avian and reptile research, as well as be applied to industrial grading of eggs.

MONITORING THE DIELECTRIC PROPERTIES AND PROPAGATION CONDITIONS OF MORTAR FOR MODERN WIRELESS MOBILE NETWORKS

Recently, modern wireless communication applications are extended to call high frequency bands including millimeter waves for 5G systems. Therefore, the propagation properties of such waves in different media have attracted many researchers. In this work, the results of the S-parameters measurements of mortar with four thicknesses are obtained using a nondestructive free space measurement technique for the frequency bands from 8 GHz up to 32 GHz. The obtained results of the dielectric properties and loss factors for the prepared mortar samples are realized. The variation in both the reflection and transmission coefficients and the dielectric properties with curing time conditions of mortar structure is examined. The dielectric properties of water are realized using the proposed method to subtract the effects of water contents from the prepared mortar samples. The effects of the sample thickness and relaxation frequency are considered. The obtained measurements are compared to the simulated results based on a full wave simulation software package of CSTMWS algorithms. Finally, excellent agreements are achieved between the simulated and measured results.

Effect of Residual Stress on Thermal Deformation Behavior.

This paper discusses a non-destructive measurement technique of residual stress through optical visualization. The least amount of deformation possible is applied to steel plates by heating the specimens +10 °C from room temperature for initial calibration, and the thermal expansion behavior is visualized with an electronic speckle pattern interferometer sensitive to two dimensional in-plane displacement. Displacement distribution with the thermal deformation and coefficient of thermal expansion are obtained through interferometric fringe analysis. The results suggest the change in the thermal deformation behavior is affected by the external stress initially applied to the steel specimen. Additionally, dissimilar joints of steel and cemented carbide plates are prepared by butt-brazing. The residual stress is estimated based on the stress dependence of thermal expansion coefficient.

Acoustic detection of apple mealiness based on support vector machine

Mealiness degrades the quality of apples and plays an important role in fruit market. Therefore, the use of reliable and rapid sensing techniques for nondestructive measurement and sorting of fruits is necessary. In this study, the potential of acoustic signals of rolling apples on an inclined plate as a new technique for nondestructive detection of Red Delicious apple mealiness was investigated. According to destructive confined compression tests, the mealiness of apples was evaluated by the hardness and juiciness measurements. In addition, support vector machine (SVM) models were developed to classify apples. The radial basis function (RBF) as the kernel was used in SVM models. According to exhaustive search method, the model with nine features combination was found to be the best model. Results indicated overall accuracy of 85.5 % to classify apples in mealy and healthy groups. The results indicated that this method is potentially useful for apple mealiness detection.

Analysis of carbon in sediments using fast neutron activation analysis (FNAA)

Purpose: Measurement of carbon in cores of undisturbed sediments may provide valuable information on historical trends in sea primary production and carbonate precipitation which can be related to climate changes. Since core sediments are usually subjected to a different analysis, it is important to preserve the sample. A non-destructive technique for carbon measurement in sediments based on fast neutron activation analysis (FNAA) has been developed, which might replace the loss-on-ignition (LOI) as a conventional method for carbon analysis.

Noninvasive Analysis of Tree Stems by Electrical Resistivity Tomography: Unraveling the Effects of Temperature, Water Status, and Electrode Installation.

The increasing demand for tree and forest health monitoring due to ongoing climate change requires new future-oriented and nondestructive measurement techniques. Electrical resistivity (ER) tomography represents a promising and innovative approach, as it allows insights into living trees based on ER levels and ER cross-sectional distribution patterns of stems. However, it is poorly understood how external factors, such as temperature, tree water status, and electrode installation affect ER tomograms. In this study, ER measurements were carried out on three angiosperms (Betula pendula, Fagus sylvatica, Populus nigra) and three conifers (Larix decidua, Picea abies, Pinus cembra) exposed to temperatures between −10 and 30°C and to continuous dehydration down to −6.3 MPa in a laboratory experiment. Additionally, effects of removal of peripheral tissues (periderm, phloem, cambium) and electrode installation were tested. Temperature changes above the freezing point did not affect ER distribution patterns but average ER levels, which increased exponentially and about 2.5-fold from 30 to 0°C in all species. In contrast, freezing of stems caused a pronounced raise of ER, especially in peripheral areas. With progressive tree dehydration, average ER increased in all species except in B. pendula, and measured resistivities in the peripheral stem areas of both angiosperms and conifers were clearly linearly related to the tree water status. Removal of the periderm resulted in a slight decrease of high ER peaks. Installation of electrodes for a short period of 32–72 h before conducting the tomography caused small distortions in tomograms. Distortions became serious after long-term installation for several months, while mean ER was only slightly affected. The present study confirms that ER tomography of tree stems is sensitive to temperature and water status. Results help to improve ER tomogram interpretation and suggest that ER analyses may be suitable to nondestructively determinate the hydraulic status of trees. They thus provide a solid basis for further technological developments to enable presymptomatic detection of physiological stress in standing trees.

A simple torque magnetometer for magnetic moment measurement of large samples: Application to permanent magnets and bulk superconductors.

The development of large size magnetic materials requires nondestructive measurement techniques to characterize their magnetic moment. In this work, we report the design and construction of a torque magnetometer able to accommodate sizable magnetic samples (>1 cm3) both at room temperature and cryogenic temperature. This device has an intermediate sensitivity between miniature torque magnetometers designed to work at cryogenic temperature and industrial torquemeters poorly adapted to extreme conditions. We show that torque sensing in the range 10-3-100 Nm can be achieved with piezoresistive metallic strain gages cemented on a cylindrical aluminum shaft with external temperature control. An absolute calibration of the device, carried out with a coil fed by a DC current, shows that magnetic moments down to 5 × 10-3 A m2 can be measured by this technique. The magnetometer is used to characterize a Nd-Fe-B permanent magnet and a permanently magnetized bulk, large grain superconductor at liquid nitrogen temperature (77 K). Results are in excellent agreement with data obtained with a flux extraction magnetometer for large samples. The device is able to measure magnetic moments in excess of 1.5 A m2, i.e., two orders of magnitude above the maximum magnetic moment of commercial magnetometers. The sample can be inserted in the air-gap of an electromagnet to measure the decrease in magnetic moment in the presence of a transverse applied field. The device was used to characterize the magnetic moment of "quasibulk" superconductors made of stacked coated conductor tapes (12 mm width) in such "crossed field" conditions.