Non-destructive Measurement Technique Research Articles

The Scanning Kelvin Probe As a Non Destructive Evaluation Tool for Monitoring the Degradation of Urethane-Epoxy Coating Systems

Performance degradation of urethane and epoxy coatings on high performance aircraft due to chemical reversion, while not visible on the surface, can be the result of changes in physical and chemical composition, leading to premature coating failure. Standard lifetime predictions fail to estimate the functional lifetime of urethane coatings on operational aircraft due to the wide variety of environmental factors and combinations of factors that trigger degradation at different rates. To better understand the role that environmental conditions play in the overall lifetime performance of these coatings, a non-destructive technique is necessary to quantitatively assess the degree of degradation/reversion that can occur. The scanning Kelvin probe (SKP) has demonstrated itself to be sensitive enough to detect changes in the alkyl chain lengths of polymers and their terminal groups as well as determine the interfacial diffusion of water through epoxy coatings as a function of the chemical structure and functional groups present within the coating. It has also demonstrated its capability to detect corrosion under coatings at the coating-metal interface. These capabilities make the use of the scanning Kelvin probe technique a compelling approach to detecting and characterizing the degradation behavior of multi-layer urethane and epoxy coating systems as well as any corrosion occurring at the coating-metal substrate interface. The objective of this effort is to develop a non-destructive evaluation technique for measurement and analysis of a multi-layer polyurethane/epoxy coating system subjected to elevated temperature and relative humidity (100 C, 100%RH) degradation conditions. Measurements of changes in the work function of non-exposed and exposed rain erosion coating (REC) system for various times at the elevated conditions have been made to correlate the degree of degradation within the coating system as determined by Raman/FTIR spectroscopy.

Thermal conductivity of Li-ion batteries and their electrode configurations – A novel combination of modelling and experimental approach

A bottom-up approach to calculate the overall and averaged thermal properties of the jelly roll or electrode stack of Li-ion cells in a generally applicable way is introduced. The model is based on temperature-dependent material properties and is specifically applied to a prismatic hardcase cell. The geometrical properties, such as width, depth, height, porosity, tortuosity, and the saturation with electrolyte are considered. Most of the material properties are determined by own measurements within a wide temperature range and compared with literature data. Anisotropic unit cell properties for homogenised three-dimensional thermal models and the corresponding representative thermal conductivity for one- or two-dimensional models can be calculated. A non-destructive measurement technique to determine the thermal conductivity of prismatic hardcase cell geometries and validate the described model is presented.

Thermography and artificial intelligence in transformer fault detection

Dissolved gas analysis of insulating oil in refrigerated power transformer oil is a widespread technique for detecting incipient faults. However, this technique involves safety procedures for the collection of oil samples, laboratory response times and, in some cases, removing the transformer from operation. Removing a transformer from operation in certain situations can become very costly as there are production environments that must run uninterrupted so that stoppages such as this represent financial loss. Infrared thermography is a non-destructive temperature measurement technique commonly used to detect anomalies and predict possible faults without disrupting system operation. This paper presents studies based on the use of infrared temperature measurement to detect incipient faults in transformers through dissolved gas analysis of the insulating oil. This study’s methodology uses intelligent systems to analyse transformer face temperatures and detect incipient faults. The results obtained in this work present 86 and 83% of classification correctness using artificial neural networks and fuzzy logic, respectively.

Nondestructive Measurement of Hall Coefficient for Materials Characterization

The Hall effect is widely exploited in NDE for measuring unknown weak magnetic fields using a small piece of conducting material of known high Hall coefficient. The Hall effect could be also exploited in NDE for measuring the unknown weak Hall coefficient of conducting materials using a strong applied magnetic field, but such measurements are fraught with difficulties because of the need to cut the specimen into a small piece similar to a Hall sensor, which of course is inherently destructive. This paper tries to answer the question how the need for destructive cutting in order to produce a measurable Hall voltage could be avoided. The underlying problem is that the Hall effect produces a Hall current that is normal to the conduction current but does not directly perturb the electric potential distribution unless the Hall current is intercepted by the boundaries of the specimen. This study investigated the feasibility of using alternating current potential drop techniques for nondestructive Hall coefficient measurement in plates. Specifically, the directional four-point square-electrode configuration is investigated with superimposed external magnetic field. Two methods are suggested to make Hall coefficient measurements in large plates without destructive machining. At low frequencies constraining the bias magnetic field can replace destructively constraining the dimensions of the specimen. At sufficiently high inspection frequencies the magnetic field of the Hall current induces a strong enough Hall electric field that produces measurable potential differences between points lying on the path followed by the Hall current even when it is not intercepted by either the edge of the specimen or the edge of the magnetic field. Both techniques are investigated first analytically to illuminate the underlying physics and then by numerical simulations to make useful quantitative predictions.

Experimental study of the contribution of gear tooth finishing processes to friction noise

Micro geometry of a gear tooth influences the contact durability and wear performance. In this paper, different gear tooth flanks have been manufactured by different finishing processes, which were then characterized using multiscale surface analysis, based on wavelet transform. The friction noise was then measured before and after meshing in dry and lubricated conditions, to quantify the acoustic performance of the surfaces. To accomplish this objective, a new non-destructive sensory measurement technique was developed to characterize the friction noise generated by teeth flank surface. Results show the ability of the new method to discriminate functional behavior of different surfaces as well as give possible explanations as to the contribution of tooth flank asperities during the meshing on the gear in terms of gear noise performances.

Advanced Characterization Techniques for Turbine Blade Wear and Damage

This paper presents four complementary non-destructive measurement techniques for material characterization and damage detection of turbine blades. The techniques are macroscopic fringe projection with inverse fringe projection algorithms, robot guided microscale fringe projection, high frequency eddy current and pulsed high frequency induction thermography, both in the megahertz range. The specimen on which the measurements were carried out is a blade of the 1st stage high pressure turbine of a modern airplane jet engine. The turbine blade was characterized with regard to the macroscopic and microscopic geometry, cracks in the base material as well as the condition of the protective layer system.

Grain engineering: How nanoscale inhomogeneities can control charge collection in solar cells

Statistical and correlative analysis are increasingly important in the design and study of new materials, from semiconductors to metals. Non-destructive measurement techniques, with high spatial resolution, capable of correlating composition and/or structure with device properties, are few and far between. For the case of polycrystalline and inhomogeneous materials, the added challenge is that nanoscale resolution is in general not compatible with the large sampling areas necessary to have a statistical representation of the specimen under study. For the study of grain cores and grain boundaries in polycrystalline solar absorbers this is of particular importance since their dissimilar behavior and variability throughout the samples makes it difficult to draw conclusions and ultimately optimize the material. In this study, we present a nanoscale in-operando approach based on the multimodal utilization of synchrotron nano x-ray fluorescence and x-ray beam induced current collected for grain core and grain boundary areas and correlated pixel-by-pixel in fully operational Cu(In(1−x)Gax)Se2 solar cells. We observe that low gallium cells have grain boundaries that over perform compared to the grain cores and high gallium cells have boundaries that under perform. These results demonstrate how nanoscale correlative X-ray microscopy can guide research pathways towards grain engineering low cost, high efficiency solar cells.

Measuring Moisture Content of Wood Using a Transient Hot-Wire Technique

Wood easily acquires a large amount of moisture when it is exposed to high-humidity conditions. The high moisture content influences the service life of wood. Thus, there is a need for an accurate, rapid, nondestructive, and simple measurement technique for wood’s moisture content. This investigation proposes a method to measure the moisture content of wood by the wood volumetric heat capacity using a transient hot wire (THW) technique. The moisture content was inferred from the change of the volumetric heat capacity before and after the wood acquired moisture; the volumetric heat capacity is the ratio of the thermal conductivity to the thermal diffusivity. The results were validated by the gravimetric method, displaying good agreement, with discrepancies within 4%.

Assessment of seed quality using non-destructive measurement techniques: a review

AbstractSeed quality is of great importance in optimizing the cost of crop establishment. Rapid and non-destructive seed quality detection methods must therefore be developed for agriculture and the seed production industry. This review focuses primarily on non-destructive techniques, namely machine vision, spectroscopy, hyperspectral imaging, soft X-ray imaging, thermal imaging and electronic nose techniques, for assessing the quality of agricultural seeds. The fundamentals of these techniques are introduced. Seed quality, including chemical composition, variety identification and classification, insect damage and disease assessment as well as seed viability and germinability of various seeds are discussed. We conclude that non-destructive techniques are accurate detection methods with great potential for seed quality assessment.

Cure temperature influences composite electrical properties by carbon nanotube-rich domain formation

Carbon nanotube (CNT) nanocomposites are enticing materials that enable engineers to tailor structural and electrical properties for applications in the automotive and aerospace industries. CNT mass fraction and the matrix cure temperature are two ways to tune the direct and alternating current electrical properties of these nanocomposites; yet, how mass fraction and cure temperature affect electrical properties remains unclear. In many cases, nanofillers such as carbon nanotubes appear in concentrated domains within the nanocomposite. Recent insights into nanoparticle-rich domain formation and its influence on electrical properties raise questions about which processing variables might optimally tune a material's functionality. Utilizing recently developed, nondestructive measurement techniques such as scanning lithium ion microscopy and microwave cavity perturbation spectroscopy, new insights are presented into the role of mass fraction and cure temperature in multiwall carbon nanotube – bisphenol A diglycidyl ether epoxy composites. Here, it is found that both mass fraction and cure temperature affect the electrical properties. Specifically, beyond the electrical percolation threshold, the DC conductivity is an order of magnitude higher for composites prepared at elevated cure temperatures for a given CNT mass fraction. Direct observations of the microdomain morphology do not show substantial differences due to cure temperature. These findings suggest pathways to generate designer nanocomposites for advanced electrically-active applications.

Separation of surface, subsurface and volume fatigue damage effects in AISI 348 steel for power plant applications

Abstract A wide range of industries including energy, chemistry, pharmacy, textiles, food and drink, pulp and paper, etc. is using stainless steels. Metastable austenitic steels such as used in power plants and chemical industry are subjected to cyclic mechanical and thermal loading in air as well as under the influence of corrosive media. This paper provides an overview on different nondestructive and electrochemical measurement techniques, which allow differentiating fatigue damage effects in total strain controlled multiple and constant amplitude tests with respect to damage appearance on surface, in subsurface area as well as in volume of specimens or components microstructure. In addition to conventional mechanical stress-strain hysteresis curves, electrical resistance, magnetic and open circuit potential measurements have been applied to characterize the cyclic deformation behavior of the metastable austenitic steel AISI 348 (X10CrNiNb18-9) in laboratory air and in distilled water. Based on these results obtained, the paper provides an outlook on the possibility for an efficient (remaining) fatigue life evaluation approach, which is adapted to the needs of the application areas.

Nondestructive Measurement of the Evolution of Layer-Specific Mechanical Properties in Sub-10 nm Bilayer Films

We use short wavelength extreme ultraviolet light to independently measure the mechanical properties of disparate layers within a bilayer film for the first time, with single-monolayer sensitivity. We show that in Ni/Ta nanostructured systems, while their density ratio is not meaningfully changed from that expected in bulk, their elastic properties are significantly modified, where nickel softens while tantalum stiffens, relative to their bulk counterparts. In particular, the presence or absence of the Ta capping layer influences the mechanical properties of the Ni film. This nondestructive nanomechanical measurement technique represents the first approach to date able to distinguish the properties of composite materials well below 100 nm in thickness. This capability is critical for understanding and optimizing the strength, flexibility and reliability of materials in a host of nanostructured electronic, photovoltaic, and thermoelectric devices.

Kiwifruit firmness: Measurement by penetrometer and non-destructive devices

Kiwifruit texture or firmness is critical to the commercial handling and eating quality of the fruit, with fruit acceptability based on firmness thresholds. Two aspects of kiwifruit firmness measurement have been investigated: i) the effect of speed of penetrometer probe movement before (approach speed) and during firmness measurement (measurement speed) and ii) a comparison of firmness values derived from compression, impact and acoustic impulse non-destructive measurements compared with a standard penetrometer measurement. Both series of experiments were repeated on fruit from two commercially available cultivars (‘Hayward’ and ‘Zesy002’ – commonly called Gold3). It is concluded that the approach speed did not affect the firmness value obtained, whereas a faster measurement speed increased the firmness value obtained for ‘Hayward’ and Gold3 fruit at <40N firmness. The use of non-destructive firmness measurement techniques tended to give good overall relationships in line with penetrometer measurements of firmness. However, for any given penetrometer firmness value, it appears that the non-destructive value obtained may depend on when in storage the measurement was made. The cause of the storage-related variability in the relationship requires further investigation of both the biological and physical processes occurring.

Microstructural characterization of additively manufactured multi-directional preforms and composites via X-ray micro-computed tomography

Additive manufacturing features “direct” and “layer-by-layer” fabrication and has significantly facilitated the microstructural design and fabrication of a wide range of highly complex parts. To enable the application of additive manufacturing in major industries and composites, it is necessary to evaluate the microstructural features of additively manufactured parts. Among the various advanced characterization techniques, X-ray micro-computed tomography (μ-CT) showed unique advantages as a high resolution, nondestructive and 3D visualization and measurement technique for material characterization. In the research reported in this article, we have fabricated an array of multi-directional preforms and composites and have characterized their microstructural features via X-ray μ-CT. First, a solid specimen as well as 3D orthogonal and 3D braided preforms have been fabricated using fused filament fabrication (FFF) and inspected with X-ray μ-CT. Then, the fabricated preforms have been infused with silicone matrix and the multi-directional preforms and composites have been tested in compression at different strain levels, to reveal their damage evolution under compressive loading. The preliminary effort made in this research demonstrates the feasibility of characterizing microstructure of additively manufactured parts via X-ray μ-CT technique and enables an investigation of the microstructural features and damage evolution of multi-directional preforms and composites.

Quantitative Spatiotemporal Chemical Profiling of Individual Lipid Droplets by Hyperspectral CARS Microscopy in Living Human Adipose-Derived Stem Cells.

There is increasing evidence showing that cytosolic lipid droplets, present in all eukaryotic cells, play a key role in many cellular functions. Yet their composition at the individual droplet level and how it evolves over time in living cells is essentially unknown due to the lack of suitable quantitative nondestructive measurement techniques. In this work, we demonstrate the ability of label-free hyperspectral coherent anti-Stokes Raman scattering (CARS) microscopy, together with a quantitative image analysis algorithm developed by us, to quantify the lipid type and content in vol/vol concentration units of individual lipid droplets in living human adipose-derived stem cells during differentiation over 9 days in media supplemented with different fatty acids. Specifically, we investigated the addition of the polyunsaturated linoleic and alpha-linolenic fatty acids into the normal differentiation medium (mostly containing monounsaturated fatty acids). We observe a heterogeneous uptake which is droplet-size dependent, time dependent, and lipid dependent. Cells grown in linoleic-acid-supplemented medium show the largest distribution of lipid content across different droplets at all times during differentiation. When analyzing the average lipid content, we find that adding linoleic or alpha-linolenic fatty acids at day 0 results in uptake of the new lipid components with an exponential time constant of 22 ± 2 h. Conversely, switching lipids at day 3 results in an exponential time constant of 60 ± 5 h. These are unprecedented findings, exemplifying that the quantitative imaging method demonstrated here could open a radically new way of studying and understanding cytosolic lipid droplets in living cells.

An improved technique for non-destructive measurement of the stem volume of standing wood

An improved technique, cheaper and less time-consuming, to measure standing wood volume by using an electronic theodolite was tested, by which greater information from the forest could be acquired accurately and non-destructively. This was achieved by recording the diameter at breast height and ground-level diameter of a tree as well as the included angle between the electronic theodolite and the left and right tangents of the stem at any point. The standing wood volume then was computed precisely by section. In addition, the factors that influence the precision of the method (observable distance and number of segments) were also analysed. In the study, 175 Larix gmelinii (Rupr.) Kuzen. trees and 190 Populus tomentosa Carrière trees chosen randomly for sampling were measured with the electronic theodolite, and then were cut down for measurement of the average cross-section volume. Based on the data acquired from 100 sample trees, a standard volume table was compiled, and then the data for the remaining random 10 sample trees in each group were selected for a comparison test. The results indicated that the optimal distance for indirect observation should be as high as the sample tree, and the optimal visual distinguished section was about 2 m. The correlation coefficient between the value measured non-destructively and the value of the felled trees of L. gmelinii was 0.97, with an average relative error of 1.62%. With regard to P. tomentosa, the correlation coefficient between the two values obtained by the two methods was 0.905 with an average relative error of 8.40%. It was concluded that the standard volume model based on the non-destructive measurement technique meets the requirements for precision in forest surveys. The precision of the standard volume model for L. gmelinii (a coniferous tree) was superior to that of the model for P. tomentosa (a broad-leaved tree). The electronic theodolite method provides an alternative technique for measuring trees without destructive sampling and is widely applicable for forest surveys.

Nondestructive Testing of Residual Stress on the Welded Part of Butt-welded A36 Plates Using Electronic Speckle Pattern Interferometry

Most manufacturing processes, including welding, create residual stresses. Residual stresses can reduce material strength and cause fractures. For estimating the reliability and aging of a welded structure, residual stresses should be evaluated as precisely as possible. Optical techniques such as holographic interferometry, electronic speckle pattern interferometry (ESPI), Moire interferometry, and shearography are noncontact means of measuring residual stresses. Among optical techniques, ESPI is typically used as a nondestructive measurement technique of in-plane displacement, such as stress and strain, and out-of-plane displacement, such as vibration and bending. In this study, ESPI was used to measure the residual stress on the welded part of butt-welded American Society for Testing and Materials (ASTM) A36 specimens with CO₂ welding. Four types of specimens, base metal specimen (BSP), tensile specimen including welded part (TSP), compression specimen including welded part (CSP), and annealed tensile specimen including welded part (ATSP), were tested. BSP was used to obtain the elastic modulus of a base metal. TSP and CSP were used to compare residual stresses under tensile and compressive loading conditions. ATSP was used to confirm the effect of heat treatment. Residual stresses on the welded parts of specimens were obtained from the phase map images obtained by ESPI. The results confirmed that residual stresses of welded parts can be measured by ESPI.

Discrimination of Transgenic Rice Based on Near Infrared Reflectance Spectroscopy and Partial Least Squares Regression Discriminant Analysis

Near infrared reflectance spectroscopy (NIRS), a non-destructive measurement technique, was combined with partial least squares regression discrimiant analysis (PLS-DA) to discriminate the transgenic (TCTP and mi166) and wild type (Zhonghua 11) rice. Furthermore, rice lines transformed with protein gene (OsTCTP) and regulation gene (Osmi166) were also discriminated by the NIRS method. The performances of PLS-DA in spectral ranges of 4 000–8 000cm-1 and 4 000–10 000cm-1 were compared to obtain the optimal spectral range. As a result, the transgenic and wild type rice were distinguished from each other in the range of 4 000–10 000cm-1, and the correct classification rate was 100.0% in the validation test. The transgenic rice TCTP and mi166 were also distinguished from each other in the range of 4 000–10 000cm-1, and the correct classification rate was also 100.0%. In conclusion, NIRS combined with PLS-DA can be used for the discrimination of transgenic rice.

Model-based in-situ measurement of pakchoi leaf area

Leaf area measurement is of great significance in plant growth process monitoring. It poses challenges to perform an unattended in-situ measurement, arising from quantifying the 3-dimensional pakchoi leaf surface. Conventional non-destructive measurement techniques, which usually take its projection on the horizon plane of the leaf area, inevitably cause considerable measurement errors. In order to improve the measurement precision for leaf area, the exemplar pakchoi leaf was modeled as a complete or a piecewise spatial plane to approximate the actual leaf surface, and a machine-vision based ad hoc measuring platform was developed to conduct the in-situ measurement. First, the leaf image was captured by a stereo vision system and segmented via a semi-automatic process to obtain its projective area and spatial inclination angle. Second, pakchoi leaves were modeled as spatial surfaces regarding to their projected counterparts. Third, leaf areas were calculated according to the established planar spatial model, acquired inclination angles and projective areas. The experimental comparison among the lattice-based monotype method, projection method, and the model-based method, whose results are denoted as MA, PA, and EA respectively, showed that the proposed framework could simultaneously meet the accuracy and non-destructive measurement requirements. The constructed platform also provided a cost-effective semi-automatic measurement approach for continuously in-situ monitoring of pakchoi growth during its whole cultivation period. It is further suggested from the experimental results that the proposed methodology can offer a generic measurement solution to various kinds of plant physiological and ecological studies in future researches. Keywords: leaf area, in-situ measurement, non-destructive measurement, stereo vision, image processing DOI: 10.3965/j.ijabe.20150804.1442 Citation: Gong L, Chen R, Zhao Y S, Liu C L. Model-based in-situ measurement of pakchoi leaf area. Int J Agric & Biol Eng, 2015; 8(4): 35－42.

Quantification of Electroluminescence Measurements on Modules

A non-destructive measurement technique is presented which yields cell parameters of individual solar cells of a photovoltaic module. Our method is based on the quantitative analysis of voltage dependent electroluminescence images together with the current-voltage-characteristic of the complete module. As a result, we obtain the ideality factors n1,2 and loss current densities J01,02 of individual cells connected in series. The applicability of our approach is demonstrated on numerical and experimental data.