Research Articles

Journal article

Egerton JS, Lowe MJS, Huthwaite P, Halai HVet al., 2017,

Ultrasonic attenuation and phase velocity of high-density polyethylene pipe material

, JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA, Vol: 141, Pages: 1535-1545, ISSN: 0001-4966

Knowledge of acoustic properties is crucial for ultrasonic or sonic imaging and signal detection in nondestructive evaluation (NDE), medical imaging, and seismology. Accurately and reliably obtaining these is particularly challenging for the NDE of high-density polyethylene (HDPE), such as is used in many water or gas pipes, because the properties vary greatly with frequency, temperature, direction and spatial location. Therefore the work reported here was undertaken in order to establish a basis for such a multiparameter description. The approach is general but the study specifically addresses HDPE and includes measured data values. Applicable to any such multiparameter acoustic properties dataset is a devised regression method that uses a neural network algorithm. This algorithm includes constraints to respect the Kramers-Kronig causality relationship between speed and attenuation of waves in a viscoelastic medium. These constrained acoustic properties are fully described in a multidimensional parameter space to vary with frequency, depth, temperature, and direction. The resulting uncertainties in acoustic properties dependence on the above variables are better than 4% and 2%, respectively, for attenuation and phase velocity and therefore can prevent major defect imaging errors.

Conference paper

Huthwaite P, 2017,

Ultrasonic finite element simulations on GPUs with Pogo

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Journal article

Haith MI, Huthwaite P, Lowe MJS, 2016,

Defect characterisation from limited view pipeline radiography

, NDT & E INTERNATIONAL, Vol: 86, Pages: 186-198, ISSN: 0963-8695

This work presents a method of characterising pipeline defects using a small number of radiographs taken at different angles around the pipe. The method relies on knowledge of the setup geometry and use of multiple images, and does not require calibration objects to be included in the setup. It is aimed at use in situations where access is difficult such as in subsea pipeline inspections. Given a set of radiographs, a background subtraction method is used to extract defects in the images. Using a ray tracing algorithm and knowledge of the experimental setup, the range of possible locations of the defect in 3D space is then calculated. Constraints are applied on potential defect shapes and positions to further refine the defect range. The method is tested on simulated and experimental flat bottomed hole defects and simulated corrosion patch defects with lateral and axial sizes ranging from 12.5 to 33.8 mm and thickness between 3 mm and 16 mm. Results demonstrate a good, consistent ability to calculate lateral and axial defect dimensions to within ±3 mm of the true size. Defect thickness calculations are more difficult and as such errors are more significant. In most cases defect thickness is calculated to within 4 mm of the actual value, often closer. Errors in thickness are due to overestimation, meaning the calculation could be used to place a maximum limit on potential defect size rather than as an actual estimate of the thickness. This would still be useful, for example in deciding whether a defect requires further investigation.

Journal article

Huthwaite P, 2016,

Eliminating incident subtraction in diffraction tomography

, Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, Vol: 472, Pages: 1-25, ISSN: 1364-5021

Diffraction tomography is a powerful algorithm for producing high-resolution quantitative reconstructions across a wide range of applications. A major drawback of the method is that it operates on the scattered field, which cannot generally be directly measured, but must instead be calculated by subtracting the incident field, i.e. the equivalent field with no scatterer present. Unfortunately, often the incident field is not measurable and hence must be estimated, causing errors. This paper highlights an important, but not widely recognized, result: for particular widely used formulations of the algorithm, the subtraction of the incident field is unnecessary, and the algorithm can actually be applied directly to measured signals. The theory behind this is derived, showing that the incident field will vanish under far-field conditions, and the result is demonstrated in practice. Tests with subsampled arrays show that aliasing artefacts can appear, but can be removed with a filter at the expense of resolution. The incident field also has no effect for a variety of array configurations tested. Finally, the performance in the presence of both correlated and uncorrelated errors is confirmed, in all cases demonstrating that the incident field has a negligible effect on the final reconstruction.

Journal article

Huthwaite P, 2016,

Guided wave tomography with an improved scattering model

, Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, Vol: 472, Pages: 1-24, ISSN: 1364-5021

Producing accurate thickness maps of corrosion damage is of great importance for assessing life in the petrochemical industry. Guided wave tomography provides a solution for this, by sending guided waves through the region of interest, then using tomographic imaging techniques to reconstruct the thickness map, importantly eliminating the need to take measurements at all points across the surface. However, to achieve accurate maps, the imaging algorithm must account for the way in which the guided waves interact with corrosion defects, and the complex scattering which occurs. Traditional approaches have exploited the dispersive nature of guided waves: a velocity map is produced from a dataset, then converted to thickness using the dispersion relationship. However, these relationships are derived for plates of constant thickness, which is not the case in the majority of defects, causing significant inaccuracies to exist in the images. This paper develops a more sophisticated inversion solution which accounts for the full-guided wave scattering, enabling more accurate images with resolution better than a wavelength, compared with two wavelengths previously. This is demonstrated with simulated and experimental data. The speed and stability of the algorithm in the presence of random noise and systematic errors is also demonstrated.

Journal article

Haith MI, Ewert U, Hohendorf S, Bellon C, Deresch A, Huthwaite P, Lowe MJS, Zscherpel Uet al., 2016,

Radiographic modelling for NDE of subsea pipelines

, NDT & E INTERNATIONAL, Vol: 86, Pages: 113-122, ISSN: 0963-8695

This work presents an investigation of the accuracy of a radiographic simulation model applied to subsea pipeline inspections. Experimental measurements of a sample in a water tank are used to develop a set of calibrated simulation parameters for the modelling software aRTist. Image quality parameters such as signal-to-noise ratio, contrast and basic spatial resolution are compared with the aim of matching simulated values to experimental results. With this method signal-to-noise ratio was successfully matched while differences were still found in contrast-to-noise ratio comparisons. This means that measurements depending on absolute intensity are not accurate enough, however wall thickness measurements in tangential images, which are not based on absolute intensity, were found to produce similar results in simulated and experimental cases. The differences in contrast and intensity are thought to be due to detector backscatter and additional scatter from out-of-setup objects within the exposure bay, due to a lack of source collimation. These would affect the experimental results but were not included in the simulated setup. This was investigated by including different proportions of peripheral water and other objects in the modelled setup and examining the effect on image quality parameters. Results show that this additional scatter has a significant impact on the radiograph, particularly on image contrast, and is therefore the likely cause of differences between experimental and simulated images. This implies that it will be very difficult to completely match simulated to experimental results, as including all possible scattering objects in the model would be very complex. An improvement could be made by using real subsea data to estimate this additional scattering, which could then be used to calibrate the model. However there would still be significant uncertainty in the ability of the model to accurately produce realistic intensity and contrast.

Journal article

Corcoran J, Nagy PB, 2016,

Compensation of the skin effect in low-frequency potential drop measurements

, Journal of Nondestructive Evaluation, Vol: 35, ISSN: 1573-4862

Potential drop measurements are routinely used in the non-destructive evaluation of component integrity. Potential drop measurements use either direct current (DC) or alternating current (AC), the latter will have superior noise performance due to the ability to perform phase sensitive detection and the reduction of flicker noise. AC measurements are however subject to the skin effect where the current is electromagnetically constricted to the surface of the component. Unfortunately, the skin effect is a function of magnetic permeability, which in ferromagnetic materials is sensitive to a number of parameters including stress and temperature, and consequently in-situ impedance measurements are likely to be unstable. It has been proposed that quasi-DC measurements, which benefit from superior noise performance, but also tend to the skin-effect independent DC measurement, be adopted for in-situ creep measurements for power station components. Unfortunately, the quasi-DC measurement will only tend to the DC distribution and therefore some remnant sensitivity to the skin effect will remain. This paper will present a correction for situations where the remnant sensitivity to the skin effect is not adequately suppressed by using sufficiently low frequency; the application of particular interest being the in-situ monitoring of the creep strain of power station components. The correction uses the measured phase angle to approximate the influence of the skin effect and allow recovery of the DC-asymptotic value of the resistance. The basis of the correction, that potential drop measurements are minimum phase is presented and illustrated on two cases; the creep strain sensor of practical interest and a conducting rod as another common case to illustrate generality. The correction is demonstrated experimentally on a component where the skin effect is manipulated by application of a range of elastic stresses.

Journal article

Seher M, Huthwaite P, Lowe MJS, 2016,

Experimental Studies of the Inspection of Areas With Restricted Access Using A0 Lamb Wave Tomography

, IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, Vol: 63, Pages: 1455-1467, ISSN: 0885-3010

Corrosion damage in inaccessible regions presents a significant challenge to the petrochemical industry, and determining the remaining wall thickness is important to establish the remaining service life. Guided wave tomography is one solution to this and involves transmitting Lamb waves through the area of interest and, subsequently, using the received signals to reconstruct a thickness map of the remaining wall thickness. This avoids the need to access all points on the surface, making the technique well suited to inspection for areas with restricted access. The influence of these areas onto the ability to detect and size surface conditions, such as corrosion damage, using guided wave tomography is assessed. For that, a guided wave tomography system is employed, which is based on low-frequency A0 Lamb waves that are excited and detected with two arrays of electromagnetic acoustic transducers. Two different defect depths are considered with different contrasts relative to the nominal wall thickness, both of which are smoothly varying and well-defined. The influence of areas with restricted surface access, support locations, pipe clamps, and STOPAQ(R) coatings is experimentally tested, and their influence assessed through comparison to a baseline reconstruction without the respective restriction in place, demonstrating only a small influence on the detected value of the remaining wall thickness.

Journal article

Corcoran J, Hooper P, Davies C, Nagy PB, Cawley Pet al., 2016,

Creep strain measurement using a potential drop technique

, International Journal of Mechanical Sciences, Vol: 110, Pages: 190-200, ISSN: 0020-7403

This paper will demonstrate the use of a potential drop sensor to monitor strain. In particular, the suitability of the technique to high temperature or harsh environment applications presents an opportunity for monitoring strain in components operating under creep conditions. Monitoring creep damage in power station components is a long standing technological challenge to the non-destructive evaluation community. It is well established in the literature that strain rate serves as an excellent indicator of the progress of creep damage and can be used for remnant life calculations. To facilitate the use of such strain rate based evaluation methods, a permanently installed, strain sensitive, potential drop technique has been developed. The technique has very simple and robust hardware lending itself to use at high temperatures or in harsh environments. Strain inversions are presented and demonstrated experimentally; a room temperature, plastic deformation experiment is used for validation and additionally an accelerated creep test demonstrates operation at high temperature (600 °C+). Excellent agreement is shown between potential drop inverted strain and control measurements.

Journal article

Van Pamel A, Huthwaite P, Brett CR, Lowe MJSet al., 2016,

Numerical simulations of ultrasonic array imaging of highly scattering materials

, NDT & E International, Vol: 81, Pages: 9-19, ISSN: 0963-8695

Journal article

Huthwaite P, 2016,

Improving accuracy through density correction in guided wave tomography

, Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, Vol: 472, Pages: 1-25, ISSN: 1364-5021

The accurate quantification of wall loss caused by corrosion is critical to the reliable life estimation of pipes and pressure vessels. Traditional thickness gauging by scanning a probe is slow and requires access to all points on the surface; this is impractical in many cases as corrosion often occurs where access is restricted, such as beneath supports where water collects. Guided wave tomography presents a solution to this; by transmitting guided waves through the region of interest and exploiting their dispersive nature, it is possible to build up a map of thickness. While the best results have been seen when using the fundamental modes A0 and S0 at low frequency, the complex scattering of the waves causes errors within the reconstruction. It is demonstrated that these lead to an underestimate in wall loss for A0 but an overestimate for S0. Further analysis showed that this error was related to density variation, which was proportional to thickness. It was demonstrated how this could be corrected for in the reconstructions, in many cases resulting in the near-elimination of the error across a range of defects, and greatly improving the accuracy of life estimates from guided wave tomography.

Journal article

Leinov E, Lowe MJS, Cawley P, 2016,

Ultrasonic isolation of buried pipes

, Journal of Sound and Vibration, Vol: 363, Pages: 225-239, ISSN: 0022-460X

Long-range guided wave testing (GWT) is used routinely for the monitoring and detection of corrosion defects in above ground pipelines. The GWT test range in buried, coated pipelines is greatly reduced compared to above ground configurations due to energy leakage into the embedding soil. In this paper, the effect of pipe coatings on the guided wave attenuation is investigated with the aim of increasing test ranges for buried pipelines. The attenuation of the T(0,1) and L(0,2) guided wave modes is measured using a full-scale experimental apparatus in a fusion-bonded epoxy (FBE)-coated 8 in. pipe, buried in loose and compacted sand. Tests are performed over a frequency range typically used in GWT of 10–35 kHz and compared with model predictions. It is shown that the application of a low impedance coating between the FBE layer and the sand effectively decouples the influence of the sand on the ultrasound leakage from the buried pipe. Ultrasonic isolation of a buried pipe is demonstrated by coating the pipe with a Polyethylene (PE)-foam layer that has a smaller impedance than both the pipe and sand, and has the ability to withstand the overburden load from the sand. The measured attenuation in the buried PE-foam-FBE-coated pipe is found to be substantially reduced, in the range of 0.3–1.2 dB m⁻¹ for loose and compacted sand conditions, compared to measured attenuation of 1.7–4.7 dB m⁻¹ in the buried FBE-coated pipe without the PE-foam. The acoustic properties of the PE-foam are measured independently using ultrasonic interferometry and incorporated into model predictions of guided wave propagation in buried coated pipe. Good agreement is found between the experimental measurements and model predictions. The attenuation exhibits periodic peaks in the frequency domain corresponding to the through-thickness resonance frequencies of the coating layer. The large reduction in guided wave attenuation for PE-coated pipes would lead to greatly increas

Journal article

Hernando Quintanilla F, Lowe MJS, Craster RV, 2015,

Full 3D dispersion curve solutions for guided waves in generally anisotropic media

, Journal of Sound and Vibration, Vol: 363, Pages: 545-559, ISSN: 1095-8568

Dispersion curves of guided waves provide valuable information about the physical and elastic properties of waves propagating within a given waveguide structure. Algorithms to accurately compute these curves are an essential tool for engineers working in non-destructive evaluation and for scientists studying wave phenomena. Dispersion curves are typically computed for low or zero attenuation and presented in two or three dimensional plots. The former do not always provide a clear and complete picture of the dispersion loci and the latter are very difficult to obtain when high values of attenuation are involved and arbitrary anisotropy is considered in single or multi-layered systems. As a consequence, drawing correct and reliable conclusions is a challenging task in the modern applications that often utilize multi-layered anisotropic viscoelastic materials.These challenges are overcome here by using a spectral collocation method (SCM) to robustly find dispersion curves in the most complicated cases of high attenuation and arbitrary anisotropy. Solutions are then plotted in three-dimensional frequency-complex wavenumber space, thus gaining much deeper insight into the nature of these problems. The cases studied range from classical examples, which validate this approach, to new ones involving materials up to the most general triclinic class for both flat and cylindrical geometry in multi-layered systems. The apparent crossing of modes within the same symmetry family in viscoelastic media is also explained and clarified by the results. Finally, the consequences of the centre of symmetry, present in every crystal class, on the solutions are discussed.

Journal article

Quintanilla FH, Fan Z, Lowe MJS, Craster RVet al., 2015,

Guided waves' dispersion curves in anisotropic viscoelastic single- and multi-layered media

, Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, Vol: 471, Pages: 1-23, ISSN: 1364-5021

Guided waves propagating in lossy media are encountered in many problems across different areas of physics such as electromagnetism, elasticity and solid-state physics. They also constitute essential tools in several branches of engineering, aerospace and aircraft engineering, and structural health monitoring for instance. Waveguides also play a central role in many non-destructive evaluation applications. It is of paramount importance to accurately represent the material of the waveguide to obtain reliable and robust information about the guided waves that might be excited in the structure. A reasonable approximation to real solids is the perfectly elastic approach where the frictional losses within the solid are ignored. However, a more realistic approach is to represent the solid as a viscoelastic medium with attenuation for which the dispersion curves of the modes are, in general, different from their elastic counterparts. Existing methods are capable of calculating dispersion curves for attenuated modes but they can be troublesome to find and the solutions are not as reliable as in the perfectly elastic case. In this paper, in order to achieve robust and accurate results for viscoelasticity a spectral collocation method is developed to compute the dispersion curves in generally anisotropic viscoelastic media in flat and cylindrical geometry. Two of the most popular models to account for material damping, Kelvin–Voigt and Hysteretic, are used in various cases of interest. These include orthorhombic and triclinic materials in single- or multi-layered arrays. Also, and due to its importance in industry, a section is devoted to pipes filled with viscous fluids. The results are validated by comparison with those from semi-analytical finite-element simulations.

Journal article

Van Pamel A, Brett CR, Huthwaite P, Lowe MJSet al., 2015,

Finite element modelling of elastic wave scattering within a polycrystalline material in two and three dimensions

, Journal of the Acoustical Society of America, Vol: 138, Pages: 2326-2336, ISSN: 0001-4966

Finite element modelling is a promising tool for further progressing the development of ultrasonic non-destructive evaluation of polycrystalline materials. Yet its widespread adoption has been held back due to a high computational cost, which has restricted current works to relatively small models and to two dimensions. However, the emergence of sufficiently powerful computing, such as highly efficient solutions on graphics processors, is enabling a step improvement in possibilities. This article aims to realise those capabilities to simulate ultrasonic scattering of longitudinal waves in an equiaxed polycrystalline material in both two (2D) and three dimensions (3D). The modelling relies on an established Voronoi approach to randomly generate a representative grain morphology. It is shown that both 2D and 3D numerical data show good agreement across a range of scattering regimes in comparison to well-established theoretical predictions for attenuation and phase velocity. In addition, 2D parametric studies illustrate the mesh sampling requirements for two different types of mesh to ensure modelling accuracy and present useful guidelines for future works. Modelling limitations are also shown. It is found that 2D models reduce the scattering mechanism in the Rayleigh regime.

Journal article

Pettit JR, Walker AE, Lowe MJS, 2015,

Improved Detection of Rough Defects for Ultrasonic Nondestructive Evaluation Inspections Based on Finite Element Modeling of Elastic Wave Scattering

, IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, Vol: 62, Pages: 1797-1808, ISSN: 0885-3010

Defects which possess rough surfaces greatly affectultrasonic wave scattering behaviour, usually reducing the magnitudeof reflected signals. Understanding and accurately predictingthe influence of roughness on signal amplitudes is crucial,especially in Non-Destructive Evaluation (NDE) for the inspectionof safety-critical components. An extension of Kirchhoff theoryhas formed the basis for many practical applications; however, itis widely recognised that these predictions are pessimistic owingto analytical approximations. A numerical full field modellingapproach does not fall victim to such limitations. Here, a FiniteElement (FE) modelling approach is used to develop a realisticmethodology for the prediction of expected back-scattering fromrough defects. The ultrasonic backscatter from multiple roughsurfaces defined by the same statistical class is calculated fornormal and oblique incidence. Results from FE models arecompared with Kirchhoff theory predictions and experimentalmeasurements in order to establish confidence in the newapproach. At lower levels of roughness excellent agreement isobserved between Kirchhoff theory, FE and experimental data,whilst at higher values the pessimism of Kirchhoff theory isconfirmed. An important distinction is made between the total,coherent and diffuse signals and it is observed, significantly, thatthe total signal amplitude is representative of the informationobtained during an inspection. This analysis provides a robustbasis for a less sensitive, yet safe, threshold for inspection ofrough defects.

Journal article

Lan B, Lowe M, DUNNE F, 2015,

A spherical harmonic approach for the determination of HCP texture from ultrasound: a solution to the inverse problem

, Journal of the Mechanics and Physics of Solids, Vol: 83, Pages: 179-198, ISSN: 0022-5096

A new spherical convolution approach has been presented which couples HCP single crystal wave speed (the kernel function) with polycrystal c-axis pole distribution function to give the resultant polycrystal wave speed response. The three functions have been expressed as spherical harmonic expansions thus enabling application of the de-convolution technique to enable any one of the three to be determined from knowledge of the other two. Hence, the forward problem of determination of polycrystal wave speed from knowledge of single crystal wave speed response and the polycrystal pole distribution has been solved for a broad range of experimentally representative HCP polycrystal textures. The technique provides near-perfect representation of the sensitivity of wave speed to polycrystal texture as well as quantitative prediction of polycrystal wave speed. More importantly, a solution to the inverse problem is presented in which texture, as a c-axis distribution function, is determined from knowledge of the kernel function and the polycrystal wave speed response. It has also been explained why it has been widely reported in the literature that only texture coefficients up to 4th degree may be obtained from ultrasonic measurements. Finally, the de-convolution approach presented provides the potential for the measurement of polycrystal texture from ultrasonic wave speed measurements.

Journal article

Fan Z, Mark AF, Lowe MJS, Withers PJet al., 2015,

Nonintrusive estimation of anisotropic stiffness maps of heterogeneous steel welds for the improvement of ultrasonic array inspection

, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, Vol: 62, Pages: 1530-1543, ISSN: 0885-3010

It is challenging to inspect austenitic welds nondestructively using ultrasonic waves because the spatially varying elastic anisotropy of weld microstructures can lead to the deviation of ultrasound. Models have been developed to predict the propagation of ultrasound in such welds once the weld stiffness heterogeneity is known. Consequently, it is desirable to have a means of measuring the variation in elastic anisotropy experimentally so as to be able to correct for deviations in ultrasonic pathways for the improvement of weld inspection. This paper investigates the use of external nonintrusive ultrasonic array measurements to construct such weld stiffness maps, representing the orientation of the stiffness tensor according to location in the weld cross section. An inverse model based on a genetic algorithm has been developed to recover a small number of key parameters in an approximate model of the weld map, making use of ultrasonic array measurements. The approximate model of the weld map uses the Modeling of anIsotropy based on Notebook of Arcwelding (MINA) formulation, which is one of the representations that has been proposed by other researchers to provide a simple, yet physically based, description of the overall variations of orientations of the stiffness tensors over the weld cross section. The choice of sensitive ultrasonic modes as well as the best monitoring positions have been discussed to achieve a robust inversion. Experiments have been carried out on a 60-mm-thick multipass tungsten inert gas (TIG) weld to validate the findings of the modeling, showing very good agreement. This work shows that ultrasonic array measurements can be used on a single side of a butt-welded plate, such that there is no need to access the remote side, to construct an approximate but useful weld map of the spatial variations in anisotropic stiffness orientation that occur within the weld.

Conference paper

Egerton JS, Lowe MJS, Halai HV, Huthwaite Pet al., 2015,

Improved FE Simulation of Ultrasound in Plastics

, 42nd Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE), Publisher: American Institute of Physics (AIP), ISSN: 1551-7616

Some UK and US nuclear power stations have begun introducing high-density polyethylene (HDPE) pipes to certain cooling water circuits. HDPE offers improved performance over existing pipe materials, such as cast iron, by not corroding in-ternally or externally, yet occasional defects form in HDPE pipe fusion joints at the production stage. This necessitates suitable volumetric NDE to safely and reliably assess joint integrity. Ultrasonic NDE is the most viable current technique, but improved inspection capability is needed, given that the challenges of NDE of plastics differ significantly from those of metals. This also necessitates an accurate and reliable wave propagation simulation technique, such as finite-element (FE) modelling. Accurate FE modelling of ultrasound in high-density polyethylene (HDPE) must account for frequency-dependent behaviour but, the most ap-parent way to do so – frequency domain FE modelling – is prohibitively computationally expensive and potentially impossible to solve for all but the smallest models. Here we present a multiband time domain FE simulation technique to address this. The proposed multiband technique is a computationally efficient and accurate approach to time domain FE modelling of ultrasonic wave propagation. It could, for example, be used to validate the NDE of a large range of candidate fusion joint defects in HDPE. The proposed model uses a small number of time domain FE simulations at individual frequency bands that together cover the bandwidth of interest. The frequency dependence of acoustic properties of ultrasound is accurately represented for HDPE and could readily be applied to other media.

Conference paper

Corcoran J, Nagy PB, Cawley P, 2015,

Potential Drop Monitoring of Creep Damage at a Weld

, 42nd Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE), Publisher: American Institute of Physics (AIP), ISSN: 1551-7616

Creep failure at welds will often be the life limiting factor for pressurised power station components, offering a site for local damage accumulation. Monitoring the creep state of welds will be of great value to power station management and potential drop monitoring may provide a useful tool. This paper provides a preliminary study of potential drop monitoring of creep damage at a weldment, suggesting a measurement arrangement for a previously documented quasi-DC technique that is well suited to the application. The industrial context of the problem of creep damage at a weldment is explored, together with a numerical simulation of the effect of cracking, finally, a cross-weld accelerated creep test demonstrating the promise of the technique is presented.

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Ultrasonic finite element simulations on GPUs with Pogo