Application of Silicon Carbide Chills in Controlling the Solidification Process of Casts Made of IN-713C Nickel Superalloy

The paper presents the method of manufacturing casts made of the IN-713C nickel superalloy using the wax lost investment castingprocess and silicon carbide chills. The authors designed experimental casts, the gating system and selected the chills material. Wax pattern,ceramic shell mould and experimental casts were prepared for the purposes of research. On the basis of the temperature distributionmeasurements, the kinetics of the solidification process was determined in the thickened part of the plate cast. This allowed to establish thequantity of phase transitions which occurred during cast cooling process and the approximate values of liquidus, eutectic, solidus andsolvus temperatures as well as the solidification time and the average value of cast cooling rate. Non-destructive testing and macroscopicanalysis were applied to determine the location and size of shrinkage defects. The authors present the mechanism of solidification andformation of shrinkage defects in casts with and without chills. It was found that the applied chills influence significantly the hot spots andthe remaining part of the cast. Their presence allows to create conditions for solidification of IN-713C nickel superalloy cast withoutshrinkage defects

Real-time Monitoring of Tectonic Displacements in the Pacific Northwest through an Array of GPS Receivers

The Pacific Northwest Geodesic Array at Central Washington University collects telemetered streaming data from 450 GPS stations. These real-time data are used to monitor and mitigate natural hazards arising from earthquakes, volcanic eruptions, landslides, and coastal sea-level hazards in the Pacific Northwest. The displacement measurements are performed at millimeter-scale, and require stringent analysis and parameter estimation techniques. Recent improvements in both accuracy of positioning measurements and latency of terrestrial data communication have led to the ability to collect data with higher sampling rates, of up to 1 Hz. For seismic monitoring applications, this means 1350 separate position streams from stations located across 1200 km along the West Coast of North America must be able to be both visually observed and analyzed automatically. We aim to make the real-time information from GPS sensors easily available, including public access via interfaces for all intelligent devices with a connection to the Internet. Our contribution is a dashboard application that monitors the real-time status of the network of GPS sensors. We are able to visualize individual and multiple sensors using similar time series scales. We are also able to visualize groups of sensors based on time-dependent statistical similarity, such as sensors with the the highest variance, in real-time. In addition to raw positioning data, users can also display derived quantities, such as the Allan variance or the second derivative of a data stream

Noise Characteristics of Operational Real‐Time High‐Rate GNSS Positions in a Large Aperture Network

Large earthquakes are difficult to model in real‐time with traditional inertial seismic measurements. Several algorithms that leverage high‐rate real‐time Global Navigation Satellite Systems (HR‐GNSS) positions have been proposed, and it has been shown that they can supplement the earthquake monitoring effort. However, analyses of the long‐term noise behavior of high‐rate real‐time GNSS positions, which are important to understand how the data can be used operationally by monitoring agencies, have been limited to just a few sites and to short time spans. Here, we show results from an analysis of the noise characteristics of 1 year of positions at 213 GNSS sites spanning a large geographic region from Southern California to Alaska. We characterize the behavior of noise and propose several references noise models which can be used as baselines to compare against as technological improvements allow for higher precision solutions. We also show how to use the reference noise models to generate realistic synthetic noise that can be used in simulations of HR‐GNSS waveforms. We discuss spatiotemporal variations in the noise and their potential sources and significance. We also detail how noise analysis can be used in a dynamic quality control to determine which sites should or should not contribute positions to an earthquake modeling algorithm at a particular moment in time. We posit that while there remain important improvements yet to be made, such as reducing the number of outliers in the time series, the present quality of real‐time HR‐GNSS waveforms is more than sufficient for monitoring large earthquakes

Determination of crystal orientation by Ω-scan method in nickel-based single-crystal turbine blades

The article presents an assessment of the crystal perfection of single-crystal turbine blades based on the crystal orientation and lattice parameter distribution on their surface. Crystal orientation analysis was conducted by the X-ray diffraction method Ω-scan and the X-ray diffractometer provided by the EFG Company. The Ω-scan method was successfully used for evaluation of the crystal orientation and lattice parameters in semiconductors. A description of the Ω-scan method and an example of measurement of crystal orientation compared to the Laue and EBSD methods are presented.This work was supported by the National Science Centre Poland (NCN) under Grant No. Preludium-UMO-2016/21/N/ST8/00240

GPS constraints on 34 slow slip events within the Cascadia subduction zone, 1997–2005

Refinements to GPS analyses in which we factor geodetic time series to better estimate both reference frames and transient deformation resolve 34 slow slip events located throughout the Cascadia subduction zone from 1997 through 2005. Timing of transient onset is determined with wavelet transformation of geodetic time series. Thirty continuous stations are included in this study, ranging from northern California to southwestern British Columbia. Our improvements in analysis better resolve the largest creep events and also identify many smaller events. At 48.5 degrees N latitude, a 14-month average recurrence interval has been observed over eight events since 1997. Farther north along Vancouver Island a host of smaller events with a distinct 14-month periodicity also occurs. In southern Washington State, some of the largest transient displacements are observed but lack any obvious periodicity in their recurrence. Along central Oregon, an 18-month recurrence is evident, while in northern California an 11-month periodicity continues through 2005. We invert GPS offsets of the 12 best recorded events for thrust slip along the plate interface using a cross-validation scheme to derive optimal smoothing parameters. These 12 events have equivalent moment magnitudes between 6.3 and 6.8 and have 2–3 cm of slip. Unlike other subduction zones, no long-duration events are observed, and cumulative surface deformation is consistently less than 0.6 cm. The many newly resolved smaller transient events in Cascadia show that slow slip events occur frequently with GPS best capturing only the largest events. It is likely that slow slip events occur more frequently at levels not detectable with GPS

Plate Boundary Observatory and related networks: GPS data analysis methods and geodetic products

The Geodesy Advancing Geosciences and EarthScope (GAGE) Facility Global Positioning System (GPS) Data Analysis Centers produce position time series, velocities, and other parameters for approximately 2000 continuously operating GPS receivers spanning a quadrant of Earth’s surface encompassing the high Arctic, North America, and Caribbean. The purpose of this review is to document the methodology for generating station positions and their evolution over time and to describe the requisite trade-offs involved with combination of results. GAGE GPS analysis involves formal merging within a Kalman filter of two independent, loosely constrained solutions: one is based on precise point positioning produced with the GIPSY/OASIS software at Central Washington University and the other is a network solution based on phase and range double-differencing produced with the GAMIT software at New Mexico Institute of Mining and Technology. The primary products generated are the position time series that show motions relative to a North America reference frame and secular motions of the stations represented in the velocity field. The position time series themselves contain a multitude of signals in addition to the secular motions. Coseismic and postseismic signals, seasonal signals from hydrology, and transient events, some understood and others not yet fully explained, are all evident in the time series and ready for further analysis and interpretation. We explore the impact of analysis assumptions on the reference frame realization and on the final solutions, and we compare within the GAGE solutions and with others

Influence of Heat Treatment on Defect Structures in Single-Crystalline Blade Roots Studied by X-ray Topography and Positron Annihilation Lifetime Spectroscopy

Single-crystalline superalloy CMSX-4 is studied in the as-cast state and after heat treatment, with material being taken from turbine blade castings. The effect of the heat treatment on the defect structure of the root area near the selector/root connection is emphasized. Multiscale analysis is performed to correlate results obtained by X-ray topography and positron annihilation lifetime spectroscopy (PALS). Electron microscopy observations were also carried out to characterize the inhomogeneity in dendritic structure. The X-ray topography was used to compare defects of the misorientation nature, occurring in as-cast and treated states. The type and concentration of defects before and after heat treatment in different root areas were determined using the PALS method, which enables voids, mono-vacancies, and dislocations to be taken into account. In this way, differences in the concentration of defects caused by heat treatment are rationalized