Potential Difference Method Research Articles

The use of a swept frequency alternating current potential difference method for identifying local geometric features within prismatic conductors

Potential difference methods are widely accepted as means to detect and monitor cracks in safety critical components. This paper investigates the capability of the potential difference method that uses a swept frequency alternating current excitation (i.e. skin effect with varying current penetration depths) in identifying conductor shapes and features through experiments and finite element analysis. The study focused on samples with the size of 55 mm × 100 mm2 and surface features with opening widths vary from 11% to 42% to the sample size. The method has been investigated by finite element analysis with the capability to distinguish cross-sectional shapes of non-magnetic conductors due to prominent current crowding on surfaces, in which the potential differences measured from a SS316 conductor of triangular cross-sectional shape are higher to those of a circular shape by 77% at 300 kHz. The detection capability of the method has also be confirmed, which is attributed to the impact of feature openings on skin effect. At 50 kHz, potential differences measured across features with the same cross-sectional area of 9 mm2 on EN1A samples rise by 130% as the opening width increase from 11% to 42% to the sample size.

Hydrocarbon migration and accumulation in member 3 of the Palaeogene Shahejie formation in the Nangong sag, Southern Bohai Bay basin, Eastern China: Insights from the fluid potential change rate and finite difference method

By integrating the fluid potential change rate analysis and finite difference method, the hydrocarbon migration and accumulation (HMA) pattern of Member 3 of the Palaeogene Shahejie Formation (Es3) in the Nangong Sag, southern Bohai Bay Basin, were quantitatively identified. The maximum and minimum points of the cross-sectional fluid potential configuration define the intersections between HMA unit boundaries and the corresponding cross-sectional view, the intersections between the preferential migration conduits and the corresponding cross-sectional view, respectively. The finite difference centred approximations for the fluid potential change rates derived from 8 sets of sections with different azimuths and the impact of the HMA unit boundaries on the HMA indicate the HMA pattern during the key reservoir-forming period. Nine HMA units and 4 favourable accumulation regions have been identified. The boundaries of the HMA units to which the Juanzizhen and Qijizhen anticline structural belts belong have the most significant impact on HMA. The 4 dominant hydrocarbon accumulation regions are mainly located in the eastern subsag belt, and there are also significant accumulation regions in the north-central part of the western slope. Integrated analysis of hydrocarbon migration directions at different structural positions indicates that hydrocarbon migration is highly heterogeneous within different HMA units and structural units. However, hydrocarbon migration within the Juanzizhen and Qijizhen anticline structural belts is oriented S ∼ SE and SSW ∼ ESE and WSW ∼ NW in the northeast and south-central regions of the sag, respectively. The new methods and results in this study will provide important insights for establishing HMA models and for accurately identifying hydrocarbon enrichment regions and hydrocarbon sources in oil-rich basins.

Interactions between adsorbed hydrogen and water molecules on a polycrystalline Pt electrode studied by in-situ ATR-FTIR spectroscopy

In order to gain further insight into the interactions between hydrogen adsorbed on platinum and water in an acid electrolyte, in situ infrared spectra were examined in detail. A polycrystalline Pt electrode/sulfuric acid solution interphase was observed by in-situ attenuated total reflectance (ATR) FTIR spectroscopy in the potential region between the double layer and hydrogen evolution by use of the potential difference method. The background potential in the measurements was chosen first at 0.7 V vs. RHE to examine the effect of underpotentially deposited hydrogen (HUPD) adsorption on the interfacial water spectra. Analysis of the spectra revealed two well-defined HOH bending bands, a sharp one at 1620 cm−1 and a broad one at 1700 cm−1. The intensity of the 1620 cm−1 band was found to increase linearly with increasing coverage of HUPD determined by the cyclic voltammogram (CV) corrected for the HER current. This led to an assignment to water molecules co-adsorbed with HUPD with only weak interactions with the latter and between each other. The broad band at 1700 cm−1 was assigned to the HOH bending mode of water associated with hydronium ions. Its intensity was found to increase at lower potentials due to its electrostatic attraction to the increasingly negative surface charge. An intense, broad, negative-going band around 2970 cm−1 was found to develop below 0.4 V, which is assigned to water dimers adsorbed at on-top Pt sites in the double layer potential region and desorbed upon adsorption of HUPD. A new choice of the reference potential at 0.2 V was successful in detecting a distinct OH stretching band around 3580 cm−1, which developed in close correlation with the band assigned to overpotentially deposited hydrogen (HOPD) at ca. 2080 cm−1. The band was assigned to the asymmetric OH stretching mode of water molecules hydrogen-bonded with HOPD. Its band intensity was found to increase linearly with that of HOPD with a slope close to 1.0, which suggests a highly polar nature of the Pt-HOPD bond.

Atomic structure and electronic properties of Ce + O films co-adsorbed on Mo(112)

The atomic structure, stoichiometry and electron work function of Ce + O films co-adsorbed on Mo(112) were studied by low-energy electron diffraction (LEED), Auger electron spectroscopy (AES) and contact potential difference (CPD) methods. The films with a significant predominance of one major species show the structure characteristic of the main component, which remains stable up to 15−50% of the minor species content. We report the c(4 × 4) and c(2 × 6) superstructures for Ce + O films with single layer Ce coverage as well as c(4 × 6) and (2 × 2) for double layer Ce coverage. They are exclusively specific to the (Ce + O)/Mo(112) system and have not been previously observed neither for cerium oxides nor pure cerium/pure oxygen adfilms. No noticeable electron work function change was detected due to oxygen addition to the Ce/Mo(112) films. Both oxygen-enriched and oxygen-depleted (Ce + O) films show similar typical electropositive properties.

Intercomparison of the Averaged Induced Electric Field in Learning-Based Human Head Models Exposed to Low-Frequency Magnetic Fields

Anatomical human models have been widely used in the assessment of induced field strength for low-frequency (LF) electromagnetic field exposure. One bottleneck is the assignment of a single electrical conductivity to all the voxels of the corresponding tissue. This simplification is known to cause computational artifact; therefore, a large reduction factor was considered in international guidelines and standards. Recently, head models with nonuniform conductivities generated using deep learning networks were proposed, and the effect on the reduction of staircasing artifacts was demonstrated. If the effectiveness of the models is confirmed for different models and codes, it would be useful to derive the relationship between the internal and external field strengths needed for setting the exposure limit. The Subcommittee 6 of the IEEE International Committee on Electromagnetic Safety Technical Committee 95 launched a working group to conduct the first intercomparison study of the induced electric field in learning-based head models exposed to LF magnetic fields. Seven international research groups have cooperated in this joint study. The highest relative difference (RD) in averaged electric fields was 23%, which is attributable to the difference caused the by scalar potential finite difference (SPFD) method and finite element method. Except for one group, the RDs in the 100 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> and 99 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> percentile values of the averaged electric field using the SPFD method with different solvers and codes were below 1%, indicating that the uncertainty due to different codes is sufficiently small under the same exposure scenarios. The findings would be informative for future revision of exposure limits and reduction factors in the exposure standard, which is closely related to computational uncertainty.

Evaluation Method of Spot Welding by Direct Current Potential Difference Method

Evaluation Method of Spot Welding by Direct Current Potential Difference Method

Fatigue crack monitoring of steel bridge with coating sensor based on potential difference method

• A coating sensor for fatigue crack monitoring using the potential difference method is proposed. • The theoretical model for crack monitoring using coating sensor is established. • The accuracy and applicability of coating sensor are validated by the fatigue tests and crack monitoring. Fatigue cracks are common in steel bridges. For the real-time monitoring of fatigue cracks during the service of steel bridges, this study proposes a coating sensor for fatigue crack monitoring of steel bridges based on the potential difference method. First, the coating sensor was designed with three components including driving, sensing, and protective layers, and the characteristics of each part were measured. The equation for the spatial potential distribution of the coating sensor was derived and subsequently solved using a numerical simulation method. A theoretical model for crack growth prediction was proposed, and the parameters of the theoretical model were fitted using regression analysis associated with the simulated results. Six samples with artificial cracks were used to validate the accuracy of the theoretical model for crack-growth monitoring. Finally, the accuracy and applicability of the coating sensor for monitoring fatigue crack growth were verified using fatigue tests. The results indicate that the coating sensor can easily crack as fatigue cracks grow in steel plates. The predicted and actual crack lengths in both the artificial crack growth tests and real fatigue crack growth experiments demonstrate good consistency. Moreover, comparing crack monitoring by coated sensors with image recognition crack monitoring using high-definition cameras shows that the fatigue crack monitoring of them matches well, demonstrating the accuracy and applicability of the coating sensor and corresponding theoretical model for fatigue crack monitoring.

A study on evaluation method of local pipe wall thinning based on DC potential difference measurement

In this study, a simple method to evaluate the local pipe wall thinning by using the DC potential difference method was examined. The pipe has outer diameter D and thickness t0. The local inner-wall thinning is modeled as a back wall slot having arc-shape cross section of width 2w and depth b. The constant DC current is applied to the pipe through two probes, and the distribution of potential difference between current input and output probes is measured. The potential differences measured before and after thinning are represented as V0 and V1, respectively. The thinning depth b/t0 is evaluated from the maximum value of V1/V0. Three-dimensional finite element method was used to analyze the relation between thinning size and potential difference for various cases. As a result, it was shown that the relation between b/t0 and V1/V0 is affected by w/D. The calibration equation between b/t0 and V1/V0 was obtained by approximating FEM results, and its validity was shown by numerical experiments.

Fatigue Damage Evaluation of Quasi-Isotropic CFRP Laminates Based on Electrical Resistance Change and Cross-Sectional Observation

In recent years, the demand for CFRP is steadily growing because of its high specific strength. Since CFRP laminates show complex fracture modes, an accurate damage detection technique is anticipated to be developed. In this study, we aimed to detect the micro damage of CFRP laminates in the early stage of fatigue. We focused on the DC potential difference method because it is a convenient measurement one using the conductivity of CFRP. The potential difference decreased in the early stage of fatigue test and turned to increase at the very end of fatigue test. The cross-sectional observations on fatigued specimens confirmed that transverse crackings and interlaminar delaminations occurred during the descending process of the potential difference. The results of this study indicated the need to focus on the decrease of potential difference to detect the early stage of fatigue damage in CFRP laminates.

Evaluation of Early Fatigue Damage of CFRP Laminates by DC Potential Difference Method

Evaluation of Early Fatigue Damage of CFRP Laminates by DC Potential Difference Method

Calculation of Internal Electric Fields Induced by Power Frequency Magnetic Fields During Live-Line Working Using Human Models With Realistic Postures

Worker exposure to high-intensity magnetic fields encountered during bare-handed live-line working on a conductor of an overhead transmission line is a major safety concern. In this article, internal ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ</i> ) electric fields in a live-line worker induced by power frequency magnetic fields were numerically calculated considering realistic exposure conditions, i.e., different working postures on a conductor bundle of an overhead transmission line. The scalar potential finite difference (SPFD) method was adopted to voxel-based human models with realistic postures to calculate internal electric fields inside the models. The results showed that the internal electric fields were far below the basic restriction for occupational exposure stipulated in the International Commission on Nonionizing Radiation Protection guidelines even when the maximum magnetic field exceeded the reference level in the guidelines.

Electrochemical Methods for the Study of Liquid Metals: Highlights from Metallurgical Transactions

Metallurgical Transactions—and its subsequent MMTA and MMTB—has been a home for numerous contributions related to electrochemistry as it applies to solid, but also liquid materials. Herein, a perspective is presented to highlight the utility of electrochemical methods as applied to the study of liquid metals. The review of a subset of papers shows the diversity of experimental options available to investigate the thermodynamic properties of liquid metals, as well as certain limitations. A specific set of results covering the entire range of two liquid binary systems is reviewed as an illustration of the static electrochemical potential difference method. More recent developments offered by dynamic electrochemical potential methods, using direct and alternating currents or containerless configurations, are reviewed. Advances in electrochemical studies of liquid metals bring the prospect of simultaneous thermodynamic and transport properties measurements closer to reality.

Comparison of the Values of Solar Cell Contact Resistivity Measured with the Transmission Line Method (TLM) and the Potential Difference (PD).

This work presents a comparison of values of the contact resistivity of silicon solar cells obtained using the following methods: the transmission line model method (TLM) and the potential difference method (PD). Investigations were performed with two independent scientific units. The samples were manufactured with silver front electrodes. The co-firing process was performed in an infrared belt furnace in a temperature range of 840 to 960 °C. The electrical properties of a batch of solar cells fabricated in two cycles were investigated. This work focuses on the different metallisation temperatures of co-firing solar cells and measurements were carried out using the methods mentioned. In the TLM and PD methods, the same calculation formulae were used. Moreover, solar cell parameters measured with these methods had the same, similar, or sometimes different but strongly correlated values. Based on an analysis of the selected databases, this article diagnoses the recent and current state of knowledge regarding the employment of the TLM and PD methods and the available hardware base. These methods are of interest to various research centres, groups of specialists dealing with the optimisation of the electrical properties of silicon photovoltaic cells, and designers of measuring instruments.

ИСПОЛЬЗОВАНИЕ МОНОМОЛЕКУЛЯРНОЙ ЗАЩИТНОЙ ПЛЕНКИ НА ПОВЕРХНОСТИ УЗЛОВ ТРЕНИЯ ДЛЯ ПОВЫШЕНИЯ НАДЕЖНОСТИ СЕЛЬСКОХОЗЯЙСТВЕННОЙ ТЕХНИКИ

One of the factors limiting the reliability of machines and mechanisms is the wear of the contacting surfaces of friction units, which affects their service life. To prevent it, the friction units are treated with lubricants. Surfactants containing fluorinated hydrocarbon radicals are of the greatest interest as an additive to lubricants. (Research purpose) The research purpose is in studying the effect of a protective monomolecular film of fluorinated surfactants on the processes of friction and wear occurring on the surfaces of friction units under conditions of boundary and hydrodynamic friction. (Materials and methods) The structure of the metal was studied before and after the application of a monomolecular protective film, the contact potential difference and the hardness of the samples were determined. The influence of surface energy on the oil absorption of materials was evaluated. (Results and discussion) It was revealed using the contact potential difference method, the process of applying a monomolecular protective film ends after 1.5-3.0 minutes and further exposure in the composition does not lead to a change in the contact potential difference. The values of the adhesion action and wetting energy for surfaces with this coating indicate that the surface energy does not depend on the material, but is determined by the coating of the monomolecular protective film of the test sample. The compositions of 0.05 percent of solutions of fluorinated surfactants form a more porous coating compared to the concentration of 0.5 percent. (Conclusions) Fluorinated surfactants have a high tribotechnical efficiency as antifriction and anti-wear nanomaterials. Their use makes it possible to protect the contact surfaces with a film 3-6 nm thick both under boundary and under hydrodynamic friction. The specified protective film performs the function of a "compensator" for various lubrication modes.

Study on discharge point distribution of finishing in high-speed wire electrical discharge machine based on potential difference method

Study on discharge point distribution of finishing in high-speed wire electrical discharge machine based on potential difference method

An Evaluation on Fracture Toughness in SUS304 at High Strain Rate Considering Process Zone

Some research works report the relationships between transformation toughening and process zone. In SUS304, the reduction of transformation toughening at high strain rate is expected from the result of a small punch test. Currently, the process zone in SUS304 is fuzzily defined. Therefore, a consideration of damaging process is necessary in order to understand a fracture mechanism associated with transformation toughening and process zone. In this study, at first, tensile tests of pre-cracked sheet specimens made of SUS304 are conducted by the split Hopkinson pressure bar in order to understand the fracture mechanism phenomenologically at high deformation rate. During the test, a DC potential difference method is introduced to capture onset time of fracture.

A customized electrical potential difference method for in situ monitoring of propagating cracks using a stochastic algorithm

In this paper, a modified direct current potential drop (DCPD) method for real-time measurement of the length, the inclination and the position of cracks is presented. Based on the proposed configuration, it is possible to process the data acquired by continuously measuring the change in the electrical resistance (potential drop) between specific points on the specimen in real time and correlate them with the propagation of the crack and thus identifying its crucial characteristics. Furthermore, many aspects that affect the electromagnetic field inside materials have been identified. In that way the influence of unwanted factors can be significantly reduced which has led to a better understanding of the relation between the implemented voltage values and the fracture itself. Therefore, conclusions are drawn about the structural integrity of any given specimen through a risk assessment after the crack characteristics have been calculated. In order to achieve this, a variety of techniques were implemented including the development of a stochastic algorithm along with a customized experimental layout so as to accomplish high accuracy for the prediction model as well as robustness towards other influencing parameters such as temperature and humidity.

The Effect of Environmental Parameters on Nondestructive Control of Metal Machine Parts by the Contact Potential Difference Method

This article is devoted to improvement of a nondestructive control of metal machine parts by the contact potential difference method. The results of experimental studies of the effect of environmental parameters on the contact potential difference measurements with a Kelvin probe on the surface of metal samples from Al, Ti, and Ni are presented. The measured dependence of the contact potential difference on the surface of metals on the environmental parameters has been explained. Practical recommendations for measuring the contact potential difference on the surface of parts have been given. The results can be used in production, operation, and repair of metal machine parts.

Dynamic crack propagation in specimens with a surface irregularity

Initiation of cracks and their propagation in prescribed orientations on tubular specimens has been made possible on a dynamic fatigue testing rig developed at the University of Aberdeen. This rig was originally designed to perform experiments on single edge notched beams (SENB) [1,2]. Modifications have recently been made so as to accommodate experimental tests on tubular specimens with a range of sizes and other cross sections. Crack initiation at grooves on such specimens has been followed by crack growth. At the same time, lateral oscillations of cracked specimen have been measured, as well as accelerations of base excitation, masses above and below cracked specimen. Forces on these two masses have been observed by two load cells attached at positions close to specimen. These load cells facilitated the measurement of stresses in experiment. Crack length time histories have also been constructed by applying an alternating current potential difference (ACPD) method. Fatigue cracks were initiated at the pre-cut grooves in aluminium tubular specimens. Three specimens with different groove sizes were tested in fifteen individual experiments. A three-dimensional Finite Element model was established for each specimen so as to calculate the stress concentration factor (SCF). This formed the basis of determining the amplitude of forcing input made possible by an electromechanical shaker. The phase shifts of acquired time histories has provided some indication of energy transfer mechanism during fatigue and system dynamic response. Observations of cracked specimen displacement during experiments was compared against calculated displacement from elastic theory. Nonlinear responses were observed, suggesting nonlinear stiffness characteristics of the specimen due to discontinuities introduced by crack growth and plasticity effects. Comparison of damage combinations in experimental observation was made with predictions from BS EN 1999-1-3. All experimental observations of total damage combination were higher than predicted values by the latter code.

Results of the application of the contact potential difference method to monitor NPP process equipment

The paper presents the results of nondestructive testing of process equipment of nuclear power plants a welding unit for the collector of steam generators PGV 1000M, the hull penetration and surfacing of the process pipe performed in the factory. The purpose of the study was to justify the possible use of contact potential difference at the stage of technological assembly and control of welded joints of steam generators in the factory, as well as to determine the prospects for using this method in operating conditions of process equipment.