Design of a low profile array transducer in d15 mode for high angled shear wave generation

Shear wave inspection is generated from mode conversion of longitudinal waves, using a selected, angled wedge positioned between the transducer and the test specimen. However, in certain scenarios where access is restricted the combination of the transducer and the wedge can be too cumbersome for in situ deployment. In this work, a low profile, linear ultrasound array transducer is proposed to generate shear waves via direct coupling to the component surface precluding the requirement for a wedge. The array transducer was designed using finite element modelling, and a prototyped array was manufactured with 32 elements and operating frequency at ~2MHz. Preliminary imaging results has shown the shear wave beam generated can be operated at high angles up to 80 degrees

A Model-based, Bayesian Solution for Characterization of Complex Damage Scenarios in AerospaceComposite Structures

Ultrasonic damage detection and characterization is commonly used in nondestructive evaluation (NDE) of aerospace composite components. In real materials and structures, the dispersive wavesresult in complicated behavior in the presence of complex damage scenarios. Model-based characterization methods utilize accurate three dimensional finite element models(FEMs), using PZFlex, of guided wave interaction with realistic damage scenariosto aid in defect identification & classification. This work builds on the results and methods in [1] and describes an inverse solution for realistic composite damage characterization by comparing the wavenumber- frequency spectra of experimental and simulated UT inspections. The FEM is parameterized with the damage model described in a companion presentation [2], capable of describing the complex damage typical of low impact strikesin composites (Figure 1). The damage is characterized through a stochastic solution, enabling uncertainty quantification surrounding the characterization. Typical Bayesian methods, such as Markov chain Monte Carlo (MCMC), are computationally costly and cannot be easily parallelized. In this work, we present a Sequential Monte Carlo (SMC) scheme in which the complex damage parameterization is formulated as a set of random variables, propagated using importance sampling and MCMC-based rejuvenation mechanismsto characterize the composite damage and quantify the uncertainty surrounding those estimates. SMC enables increasing FEM fidelity during the solution, allowing for fast optimal global localization and subsequent damage characterization refinement

A Parameterized Delamination Model for Use in Complex Damage Characterization of Composite Laminatesin Ultrasonic Inspections

Ultrasonic damage detection and characterization is commonly used in nondestructive evaluation (NDE) of aerospace composite components. However, in real materials and structures, the dispersive waves can result in complicated behavior, particularly in the presence of complex damage scenarios and structural components. Accurate three dimensional finite element models (FEMs), using PZFlex, of guided wave interactions with realistic damage scenarios can be used to study quantitative NDE ultrasonic damage detection techniques numerically, to supplement or replace expensive experimental testing. Novel data analysis techniques such as filter reconstruction imaging methods can be used to create practical comparisons between experimental and simulated data. To compare experimental and simulated data, however, the FEM must accurately simulate the physics of an ultrasonic inspection. This requires that information about the damage be known a priori (e.g. through CT scans of the laminates). While possible in a research setting, this is typically not the case for real inspections in which the goal is to characterize the unknown damage. This work will describe a means of parameterizing a FEM of a composite laminate for use in a damage characterization scheme. The FEM is parameterized with a multidimensional damage model capable of describing the complex amage typical of low impact strikes in composites. The damage under consideration in this work is described by the spiraling, multilayer delamination depicted in Figure 1. Experimental laser Doppler vibrometer (LDV) wavefield data and the FEM simulated vibration responses are postprocessed using the 3D Fourier transform so that the wavenumber-frequency spectra can be readily compared, building on the results and methodsin. The purpose of the parameterized damage model is for use in a probabilistic damage characterization methodology, discussed in a companion presentation. The composite laminate model and the ultrasonic inspection are simulated using PZFlex and allows for iterative refinement of the damage. The increasing model fidelity enablesfast localization ofthe damage followed by subsequent refined characterization

Finite element analysis of ultrasonic CFRP laminate inspection

Carbon Fibre Reinforced Polymer (CFRP) materials pose a challenge for NDE inspections due to their anisotropic material properties and often complex morphologies. Simulation is a vital tool in the design of ultrasonic inspections, improving setup and helping understand wave propagation in complex components. In this work, three different approaches of constructing accurate Finite Element Analysis (FEA) models of CFRP components are presented. The first approach generates a model of a flat CFRP laminate using the design specification to construct the idealised laminate geometry – essentially recreating the ‘as designed’ component in the model. The second approach utilises photomicrographs of the laminates’ cross-section to produce a more realistic ‘as built’ geometry within the model. Ultrasonic inspection simulations performed show a good correlation when comparing resulting A-scans with experiments. A final modelling approach of using an image of X-Ray CT data is then performed to develop an accurate model of a tapered composite structure. This paper presents the construction of the finite element models using PZFlex and the subsequent results highlighting the ability of the simulations to recreate experimental inspection performance

Hybrid simulation model of ultrasonic inspection of pressure tubes in nuclear industry

Pressure tube inspection within CANDU nuclear reactors is a critical maintenance operation to identify and track the growth of defects within the tube. Current inspection approaches utilising ultrasonic techniques are technically challenging, which cause the whole inspection process to be resource intensive and expensive to implement. This paper will describe the initial stages in the development of a simulation approach for the ultrasonic inspection methodology to research advanced solutions with the objective of improving the inspection accuracy. Zirconium tubes with a thickness of 4.3mm and a required measurement accuracy of defect depth of 0.1mm require the use of high frequency ultrasonic transducers. The finite element modelling of high frequencies is challenging due to the increased mesh requirements to resolve the small wavelengths and the large propagation distance which can cause numerical dispersion. Hence, a 2D finite element hybrid model is developed in PZFlex software to overcome this difficulty with five subsequent components containing both finite element models and analytical solutions: ultrasound transmission; transmission extrapolation (wave propagation); target interaction; echo wave extrapolation and ultrasonic reception. To test the capability of defect inspection using the hybrid model, a slot with a depth of 1mm is introduced in the model. The depth information was calculated from the time-of-flight between the reflections of the tube surface and the slot. The predicted modelled depth estimates produces errors of less than 20micron for both 10MHz and 20MHz probe configurations validating the hybrid modelling approach. Moreover, experimental validation of the hybrid modelling approach is demonstrated

Quantifying performance of ultrasonic immersion inspection using phased arrays for curvilinear disc forgings

Use of full-matrix capture (FMC), combined with the total focusing method (TFM), has been shown to provide improvements to flaw sensitivity within components of irregular geometry. Ultrasonic immersion inspection of aerospace discs requires strict specifications to ensure full coverage – one of which is that all surfaces should be machined flat. The ability to detect defects through curved surfaces, with an equivalent sensitivity to that obtained through flat surfaces could bring many advantages. In this work, the relationship between surface curvature and sensitivity to standard defects was quantified for various front wall radii. Phased array FMC immersion inspection of curved components was simulated using finite element modelling, then visualized using surface-compensated focusing techniques. This includes the use of BRAIN software developed at the University of Bristol for production of TFM images. Modelling results were compared to experimental data from a series of test blocks with a range of curvatures, containing standard defects. The sensitivity to defects is evaluated by comparing the performance to conventional methods. Results are used to highlight the benefits and limitations of these methods relating to the application area of aerospace engine disc forgings

Finite element analysis simulations for ultrasonic array NDE inspections

Advances in manufacturing techniques and materials have led to an increase in the demand for reliable and robust inspection techniques to maintain safety critical features. The application of modelling methods to develop and evaluate inspections is becoming an essential tool for the NDE community. Current analytical methods are inadequate for simulation of arbitrary components and heterogeneous materials, such as anisotropic welds or composite structures. Finite element analysis software (FEA), such as PZFlex, can provide the ability to simulate the inspection of these arrangements, providing the ability to economically prototype and evaluate improved NDE methods. FEA is often seen as computationally expensive for ultrasound problems however, advances in computing power have made it a more viable tool. This paper aims to illustrate the capability of appropriate FEA to produce accurate simulations of ultrasonic array inspections – minimizing the requirement for expensive test-piece fabrication. Validation is afforded via corroboration of the FE derived and experimentally generated data sets for a test-block comprising 1D and 2D defects. The modelling approach is extended to consider the more troublesome aspects of heterogeneous materials where defect dimensions can be of the same length scale as the grain structure. The model is used to facilitate the implementation of new ultrasonic array inspection methods for such materials. This is exemplified by considering the simulation of ultrasonic NDE in a weld structure in order to assess new approaches to imaging such structures

Global data on earthworm abundance, biomass, diversity and corresponding environmental properties

Publisher Copyright: © 2021, The Author(s).Earthworms are an important soil taxon as ecosystem engineers, providing a variety of crucial ecosystem functions and services. Little is known about their diversity and distribution at large spatial scales, despite the availability of considerable amounts of local-scale data. Earthworm diversity data, obtained from the primary literature or provided directly by authors, were collated with information on site locations, including coordinates, habitat cover, and soil properties. Datasets were required, at a minimum, to include abundance or biomass of earthworms at a site. Where possible, site-level species lists were included, as well as the abundance and biomass of individual species and ecological groups. This global dataset contains 10,840 sites, with 184 species, from 60 countries and all continents except Antarctica. The data were obtained from 182 published articles, published between 1973 and 2017, and 17 unpublished datasets. Amalgamating data into a single global database will assist researchers in investigating and answering a wide variety of pressing questions, for example, jointly assessing aboveground and belowground biodiversity distributions and drivers of biodiversity change.Peer reviewe

Global data on earthworm abundance, biomass, diversity and corresponding environmental properties

Earthworms are an important soil taxon as ecosystem engineers, providing a variety of crucial ecosystem functions and services. Little is known about their diversity and distribution at large spatial scales, despite the availability of considerable amounts of local-scale data. Earthworm diversity data, obtained from the primary literature or provided directly by authors, were collated with information on site locations, including coordinates, habitat cover, and soil properties. Datasets were required, at a minimum, to include abundance or biomass of earthworms at a site. Where possible, site-level species lists were included, as well as the abundance and biomass of individual species and ecological groups. This global dataset contains 10,840 sites, with 184 species, from 60 countries and all continents except Antarctica. The data were obtained from 182 published articles, published between 1973 and 2017, and 17 unpublished datasets. Amalgamating data into a single global database will assist researchers in investigating and answering a wide variety of pressing questions, for example, jointly assessing aboveground and belowground biodiversity distributions and drivers of biodiversity change