Continued Developments in the Modeling of Complex Dimension and Orientation Variation in Split D Differential Eddy Current Probes

Over the past few years, the complexity of models for split D differential eddy current probes has increased significantly. Moving from rather simplistic models where coils and cores were modeled symmetrically to the current state where validation can be done using very asymmetric coils [1, 2, 3]. Last year results showing a large amount of modeling error for variation in the orientation of the various components of a split D probe were presented. As a follow-on to this effort, additional modeling work has been performed looking into alleviating this error. One of the major factors being investigated this year is increasing mesh resolution. Convergence and statistical analysis will be performed on the data to determine the appropriate mesh resolution necessary for future modeling efforts involving orientation variation is needed. Recent work has addressed a model validation study using a large split D probe scanned over a notch at various orientations. Data from the previously described simulations will be compared to the experimental data collected. By running the simulations at various mesh resolutions, it is anticipated that a pattern will emerge detailing how the mesh resolution needs to changes to achieve comparable levels of accuracy as the probe orientation varies

Gradient Enhanced Surrogate Modeling Methods for NDE Applications

Over the past 15 years, there has been significant interest in the NDE community in surrogate modeling applied to both uncertainty propagation (UP) as well as inverse uncertainty quantification (UQ). There has been a general acceptance in the value of surrogates due to the quick model evaluations that can be made during an inverse problem or for fast Monte Carlo sampling, evidenced by the fact that surrogate modeling techniques now appear in multiple commercial NDE simulation tools. Many techniques have been explored such as regular grid methods, polynomial chaos, sparse grids, response surfaces, and Kriging models, among others. While these techniques all offer reduced computational burden for UP and inverse applications, they are still somewhat computationally expensive and require a significant amount of model evaluations. To overcome this, many other communities have adopted a gradient-enhanced approach to surrogate modeling. In many cases, when sensitivities (i.e. gradients with respect to parameters) are included in building a surrogatemodel, convergence of the surrogate can be greatly enhanced. In this presentation, several different gradient-enhanced methods will be presented as applied to NDE models. The convergence of the surrogates will be shown relative to the non- gradient-enhanced surrogate models, and the surrogates will be applied to both UP and inverse problems

Models in the Design and Validation of Eddy Current Inspection for Cracking in the Shuttle Reaction Control System Thruster

A case study is presented for using models in eddy current NDE design for crack detection in Shuttle Reaction Control System thruster components. Numerical methods were used to address the complex geometry of the part and perform parametric studies of potential transducer designs. Simulations were found to show agreement with experimental results. Accurate representation of the coherent noise associated with the measurement and part geometry was found to be critical to properly evaluate the best probe designs

Paperless Publication: Surveying the Shifting Shape of Campus Journalism

The traditional procedures of campus journalism have been greatly affected by the current situation brought by the pandemic. Thus, the goal of the present study is to explore the changes in campus journalism from traditional to digital publication. It specifically intends to determine the adjustments and modifications adapted; the effect   of   certain   changes   in   the   quality, efficiency, and relevance of the campus paper; and   the   significant   shift   on   the   student readership. Moreover, the study aims to explore the themes that emerged from the findings. To meet the objectives of the study, qualitative descriptive (QD) approach was used to describe the experiences, challenges, and perspectives of the participants. Interviews were conducted to gather the needed data from the participants who were selected using purposive sampling technique. After the data were analyzed, findings reveal that student journalists find working from home more convenient and manageable. There have also been a lot of improvements in the articles in terms of grammar and structures, layout designs, topics and issues. Readers can also access various news and information through online media platforms. Furthermore, six themes have emerged in the study: Changes in editing and submission of reports in the New Normal; Distribution of workloads among members of the Editorial Board through online; The quality of outputs in online vs. printed publication; Work-from-Home (WFH) arrangements of journalists; Identifying new and trending topics; and Comparing student feedbacks and engagements

Model Benchmarking and Reference Signals for Angled-beam Shear Wave Ultrasonic NDE Inspections

NDE modeling and simulation are important tools to support the development and validation of enhanced localization and characterization techniques. Previously, important achievements were made by the USAF to address crack detection in aircraft structures using angled-beam shear wave inspection techniques. However, new work on model benchmarking is needed to move beyond detection and achieve reliable crack characterization. To achieve this goal, simulated studies are needed to verify that models can accurately represent all of the key variables with the inspection of multilayer structures with fastener sites and varying crack conditions. Often with model benchmark studies, the accuracy of the model is evaluated based on the change in response relative to a selected reference signal. During recent simulated and experimental studies, some challenges were discovered concerning the creation and/or selection of a reference signal in a plate with a vertical hole and crack. The focus of this paper is on key findings concerning model benchmarking using CIVA-UT for angled-beam shear wave inspections. The use of a side drilled hole (SDH) in a plate was found to be somewhat problematic as a reference signal for angled beam shear wave inspection. Previously, only a limited number of studies have looked at model benchmarking for angled beam shear wave inspections. Systematic studies were performed with varying SDH depth and size, and varying the ultrasonic probe frequency, focal depth, and probe height. Care must be taken in understanding the precise beam properties with these experiments. One issue is that there is some increased error with the simulation of angled shear wave beams, especially in the near-field. Even more significant, asymmetry in real probes and the inherent sensitivity of signals in the near-field to subtle test conditions were found to provide a greater challenge with achieving model agreement. Through these studies, conditions of good and poor agreement were observed. For some inspection conditions, the skip signal off of the far wall from the side drilled hole can provide a better reference than the direct reflected signal. All in all, these seemingly mundane studies were found to be important with providing guidance on reference signal selection for model benchmarking work on the inspection of fastener sites with cracks

Process Compensated Resonance Testing Modeling for Damage Evolution and Uncertainty Quantification

Process Compensated Resonance Testing (PCRT) is a nondestructive evaluation method that measures and analyzes the resonance frequencies of a component for material state characterization, defect detection and process monitoring. PCRT inspections of gas turbine engine components have demonstrated the sensitivity of resonance frequencies to manufacturing defects and in-service thermal and mechanical damage. Prior work on PCRT modeling has developed forward modeling and model inversion techniques that simulate the effects of geometry variation, material property variation, and damage on Mar-M-247 nickel-based superalloy samples. Finite element method (FEM) forward model simulations predicted the effects of variation in geometry, material properties and damage on resonance frequencies. Model inversion used measured resonance frequencies to characterize the material state of components. Parallel work developed a process for uncertainty quantification (UQ) in PCRT models and measurements. The UQ process evaluated the propagation of uncertainty from various sources, identified the most significant uncertainty sources, and enabled uncertainty mitigation to improve model and measurement accuracy. Current efforts have expanded on those developments in several areas. One-factor-at-a-time (OFAT) forward model simulations were conducted on cylindrical dog bone coupons made from Mar-M-247. The simulations predicted the resonance frequency response to variation in geometry, elastic properties, crystallographic orientation, creep strain and cracking. The OFAT studies were followed by forward model Monte Carlo simulations that predicted the effects of multiple, concurrent sources of variation and damage on resonance frequencies, allowing characterization of virtual populations and quantification of uncertainty propagation. The Monte Carlo simulation design points were used to demonstrate the generation of a virtual database of components for training PCRT inspection applications, or “sorting modules.” Virtual database training sets can potentially overcome the limitations imposed by the availability of components and material states for training sets based on physical examples. Forward modeling tools and techniques were applied to titanium to simulate the effects of material variation, damage, and crystallographic texture. Forward modeling was also applied to more complex geometries, including a notional turbine blade, to demonstrate the application of modeling tools to shapes representative of gas turbine engine components. Model inversion tools and techniques have also advanced under the current effort. Prior inversion methods relied on iterative fitting to polynomial expressions for simple geometries and bulk material properties. Current efforts have demonstrated FEM-based model inversion which allows characterization of complex shapes and material states. FEM-based design spaces were generated, model inversion was carried out for surrogate modeled resonance spectra, and inversion performance was evaluated. Analysis of PCRT modeling results led to the development of automated resonance mode matching tools based on the calculation of modal assurance criteria (MAC) values, mode shape displacement metrics and Hungarian Algorithm sorting methods

Model-based Probe State Estimation and Crack Inverse Methods Addressing Eddy Current Probe Variability

Recent work on model-based inverse methods with eddy current inspections of surface breaking discontinuities has shown some sizing error due to variability in probes with the same design specifications [1]. This is an important challenge for model-based inversion crack sizing techniques, to be robust to the varying characteristics of eddy current probes found in the field [1-2]. In this paper, a model-based calibration process is introduced that estimates the state of the probe. First, a carefully designed surrogate model was built using VIC-3D® simulations covering the critical range of probe rotation angles, tilt in two directions, and probe offset (liftoff) for both tangential and longitudinal flaw orientations. Some approximations and numerical compromises in the model were made to represent tilt in two directions and reduce simulation time; however, this surrogate model was found to represent the key trends in the eddy current response for each of the four probe properties in experimental verification studies well. Next, this model was incorporated into an iterative inversion scheme during the calibration process, to estimate the probe state while also addressing the gain/phase fit and centering the calibration notch indication. Results are presented showing several examples of the blind estimation of tilt and rotation angle for known experimental cases with good agreement within +/- 2.5 degrees. The RMS error was found to be significantly reduced by fitting the probe state and, in many instances, probe state estimation addresses the previously un-modelled characteristics (model error) with real probe inversion studies. Additional studies are presented comparing the size of the calibration notch and the quality of the calibration fit, where calibrating with too small or too large a notch can produce poorer inversion results. Once the probe state is estimated, the final step is to transform the base crack inversion surrogate model and apply it for crack characterization. Because of the dimensionality of this problem, simulations were made at a limited set of select flaw sizes with varying length, depth and width, and an interpolation scheme was used to address the effect of the probe state at intermediate solution points. Using this process, results are presented demonstrating improved crack inversion performance for extreme probe states

The PREDICTS database: a global database of how local terrestrial biodiversity responds to human impacts

Biodiversity continues to decline in the face of increasing anthropogenic pressures such as habitat destruction, exploitation, pollution and introduction of alien species. Existing global databases of species’ threat status or population time series are dominated by charismatic species. The collation of datasets with broad taxonomic and biogeographic extents, and that support computation of a range of biodiversity indicators, is necessary to enable better understanding of historical declines and to project – and avert – future declines. We describe and assess a new database of more than 1.6 million samples from 78 countries representing over 28,000 species, collated from existing spatial comparisons of local-scale biodiversity exposed to different intensities and types of anthropogenic pressures, from terrestrial sites around the world. The database contains measurements taken in 208 (of 814) ecoregions, 13 (of 14) biomes, 25 (of 35) biodiversity hotspots and 16 (of 17) megadiverse countries. The database contains more than 1% of the total number of all species described, and more than 1% of the described species within many taxonomic groups – including flowering plants, gymnosperms, birds, mammals, reptiles, amphibians, beetles, lepidopterans and hymenopterans. The dataset, which is still being added to, is therefore already considerably larger and more representative than those used by previous quantitative models of biodiversity trends and responses. The database is being assembled as part of the PREDICTS project (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems – www.predicts.org.uk). We make site-level summary data available alongside this article. The full database will be publicly available in 2015