Fast synchrotron X-ray tomographic quantification of dendrite evolution during the solidification of Mg-Sn alloys

The evolution of dendritic microstructures during the solidification of a Mg-15 wt%Sn alloy was investigated in situ via fast synchrotron X-ray microtomography. To enable these in situ observations a novel encapsulation method was developed and integrated into a fast, pink beam, imaging beamline at Diamond Light Source. The dendritic growth was quantified with time using: solid volume fraction, tip velocity, interface specific surface area, and surface curvature. The influence of cooling rate upon these quantities and primary phase nucleation was investigated. The primary dendrites grew with an 18-branch, 6-fold symmetry structure, accompanied by coarsening. The coarsening process was assessed by the specific surface area and was compared with the existing models. These results provide the first quantification of dendritic growth during the solidification of Mg alloys, confirming existing analytic models and providing experimental data to inform and validate more complex numeric models

Analytical modelling of in-situ layer-wise defect detection in 3D Printed parts: Additive Manufacturing

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.This study analyses a software algorithm developed on MATLAB, which can be used to examine fused filament fabrication-based 3D printed materials for porosity and other defects that might affect the mechanical property of the final component under manufacture or the general aesthetic quality of a product. An in-depth literature review into the 3D printed materials reveals a rapidly increasing trend in its application in the industrial sector. Hence the quality of manufactured products cannot be compromised. Despite much research found to be done on this subject, there is still little or no work reported on porosity or defect detection in 3D printed components during (real-time) or after manufacturing operation. The algorithm developed in this study is tested for two different 3-D object geometry and the same filament color. The results showed that the algorithm effectively detected the presence or absence of defects in a 3D printed part geometry and filament colors. Hence, this technique can be generalized to a considerable range of 3-D printer geometries, which solve material wastages by spotting defects during the workpieces layer-wise manufacturing process, thereby improving the economic advantages of additive manufacturing

GTTC Future of Ground Testing Meta-Analysis of 20 Documents

National research, development, test, and evaluation ground testing capabilities in the United States are at risk. There is a lack of vision and consensus on what is and will be needed, contributing to a significant threat that ground test capabilities may not be able to meet the national security and industrial needs of the future. To support future decisions, the AIAA Ground Testing Technical Committees (GTTC) Future of Ground Test (FoGT) Working Group selected and reviewed 20 seminal documents related to the application and direction of ground testing. Each document was reviewed, with the content main points collected and organized into sections in the form of a gap analysis current state, future state, major challenges/gaps, and recommendations. This paper includes key findings and selected commentary by an editing team

-ilities Tradespace and Affordability Project – Phase 3

One of the key elements of the SERC’s research strategy is transforming the practice of systems engineering and associated management practices – “SE and Management Transformation (SEMT).” The Grand Challenge goal for SEMT is to transform the DoD community’s current systems engineering and management methods, processes, and tools (MPTs) and practices away from sequential, single stovepipe system, hardware-first, document-driven, point- solution, acquisition-oriented approaches; and toward concurrent, portfolio and enterprise- oriented, hardware-software-human engineered, model-driven, set-based, full life cycle approaches.This material is based upon work supported, in whole or in part, by the U.S. Department of Defense through the Office of the Assistant Secretary of Defense for Research and Engineering (ASD(R&E)) under Contract H98230-08- D-0171 (Task Order 0031, RT 046).This material is based upon work supported, in whole or in part, by the U.S. Department of Defense through the Office of the Assistant Secretary of Defense for Research and Engineering (ASD(R&E)) under Contract H98230-08- D-0171 (Task Order 0031, RT 046)

Defect related radiative recombination in mono-like crystalline silicon wafers

The aim of this work was to investigate defect related luminescence emission in four mono-like silicon wafers. The seed-assisted silicon ingot is built by six Czochralski silicon slabs, with nine seed junctions. The discovered emission signals are due to Shockley-Read-Hall recombination. Each wafer originates from a mono-like silicon ingot grown at the Norwegian University of Science and Technology (NTNU), Trondheim. The master thesis work was conducted at the Norwegian University of Life Sciences (NMBU), Ås. Hyperspectral imaging has been used in multiple branches like medicine, industry and military purposes. In this investigation hyperspectral imaging is conducted on mono-like silicon wafers. Seed-assisted grown mono-like silicon are produced with the goal of increasing wafer efficiency at lesser cost. Spectrally resolved photoluminescence (SPL) has been used together with multivariate data analysis. This is a non-destructive method to examine defect related luminescence in each mono-like wafers. Each wafer was cooled to 88 ± 2 K before illuminated with an 810 nm laser. The photoluminescence emission from each wafer was captured by an HgCdTe hyperspectral camera. The individual D1-D4 and band to band PL emission signals were extracted with Multivariate Curve Resolution (MCR) algorithm and found in the seed junctions. It has also been found three other PL emission signals, either in the seed junctions, or from parasitic crystals penetrating into the main wafer ingot. The D07 PL emission signal is restricted to the parasitic crystals and can be related to interstitial iron Fei. A signal at 0.846 ± 0.01 eV, known as D5, has been found as a shoulder of D1 and D2 PL emission signals. These three PL signals have been related to dislocations with oxygen impurities in other studies. A new signal denoted D09 with the energy 0.904 ± 0.01 eV is discovered and is growing in intensity with increased height of the ingot. The signal seems to be centered in the seed junctions and has not been mentioned before. The D1 PL signal is strong in the A-108 wafer, then decreasing in strength with increasing height. This seems to strengthen the theory of the D1 PL emission signal related to oxygen. The D2 PL signal on the other hand increases in intensity with increased ingot height, and contradicts the oxygen theory. D3/D4 PL emission signals are found in the seed junctions and can be related to the same spatial position. The PL emission signals increases with ingot height and strengthen the suggestion that D3/D4 PL signals originates from iron-boron (FeB) complexes. The high intensity PL emission signal known as VID3 has not been found in this work. A tail on the D1 PL signal found at 0.95 eV and 1.00 eV have been discussed in other studies and can be explained by hydrogen-silicon (H-Si) bond. One parasitic crystal has been found with multiple impurities. That crystal may have another grain boundary and dislocation number than the parasitic crystals with only the D07 PL signal. Comparing this work with the work done by Ekstrøm et al. [1] has discovered some similarities. It mentions different tilt and misorientation angles in each seed junction. The investigation concluded that misorientation angles in the seed crystal junctions produced tilt around one or several axis, and would play a major part in the bulk lifetime. Comparing to the current work has found that low misorientation angle around the X-axis seems to produce none or weak defect related PL emission signals. Misorientation around Z-axis seems to produce more defect related luminescence. While misorientation around multiple axis seems to create chaotic junctions with high defect related luminescence. The explanation can be the number of vacancies ready for impurities are higher in multiple axis tilts than one single axis tilt. The conclusion is that the combined strength of SPL and MCR as a method to investigate mono-like silicon wafers has been used with success. The known D1-D4, D5 and D07 PL emission signals was found alongside a new PL emission signal at 0.904 ± 0.01 eV. The PL emission signals are not clearer than the emission signals found in mc-Si wafers, however, the D07 signal has been found separated from the rest of the other DRL signals and this can be a helpful in further experiments. The different PL emission signals are found to vary greatly throughout the ingot and logic answers can be made to explain the results based on known literature. Hyperspectral imaging and Multivariate curve resolution can strengthen and contribute to an increased quality of seed assisted mono-like wafers.I denne masteroppgaven har fire "as cut" skiver fra en mono-lik silisiumkrystall blitt undersøkt. Frø assistert mono-lik silisium ingot er en produksjonsmetode for å skape høyeffektivitetsskiver med den rimlige multikrystallinske størkningsprosessen. Prosessen er under utvikling, med mål om å kunne forbedre solcellene i et sluttprodukt. Denne masteroppgaven går ut på å avdekke defekter i disse skivene både i romlig og spektral posisjon. For å kunne finne defekter i silisiumskivene registreres fotonutslippet til eksiterte elektroner som rekombinerer etter Shockley-Read-Hall metoden. I dette eksperimentet skjer dette ved å la en 810 nm laser belyse hver av de nedkjølte skivene. Skivene er nedkjølt til 88 ± 2 K med flytende nitrogen. Fotonene fra de eksiterte elektronene registreres og fordeles til sine spektrale områder i et HgCdTe hyperspektralt kamera. For å kunne hente ut de interessante defektrelaterte spektrumene brukes Matlab og et statistisk verktøy som heter Multivariate curve resolution (MCR). I denne oppgaven har alle de fire kjente emisjonslinjene D1, D2, D3 og D4 blitt funnet sammen med bånd til bånd emisjonslinjen. Disse defektrelaterte emisjonslinjene er bare funnet i frø krystallgrensene, foruten ett sted: En parasittisk krystall nær en av sidekantene. I tillegg er det funnet tre andre emisjonslinjer. Den ene er kalt D5 som ser ut til å være en skulder av det sterkere D2 emisjonlinjen med energien 0.846 ± 0.01 eV. Det andre signalet er kalt D09 med 0.904 ± 0.01 eV og er funnet sentrert i krystallgrensene. Dette signalet ser ut til å utvikle seg fra D2 signalet i A-108 skiven og videre fram til et eget signal i A-45 skiven. Det tredje signalet er et signal nylig publisert som D07 og er bare funnet i parasittiske krystaller som virker å gro inn fra digelkantene. Denne emisjonslinjen kan stamme fra interstitielt jern Fei. D1 emisjonslinjen har høyest intensitet i nær bunn av ingoten og minsker gradvis i styrke med økende ingot høyde. D2 emisjonslinjen derimot ser ut til å styrke seg mot toppen av ingoten og er sterkest i A-45 skiven. Både D1, D2 og D5 er betegnet i litteraturen som å kunne relateres til oksygen. Ut i fra oppførselen til D2 emisjonslinjen, motsier resultatet oksygen teorien, mens D1 og D5 ser ut til å forsterke den samme teorien. D3/D4 emisjonslinjene er funnet i bare ett av frøkrystallgrensene i A-108 skiven. Derimot, i de resterende tre skivene er signalet tilstede i alle frø grensene. MCR algoritmen betrakter dette signalet som ett signal og styrker ideen om at D3/D4 har samme romlig opprinnelse. D4 emisjonslinjen er nevnt å oppstå fra jern utfellinger fra smeltediglen og ovnen, hvor D3 emisjonslinjen kan være en fononreplica av D4. I denne undersøkelsen øker D3/D4 emisjonslinjene i intensitet med økt ingot høyde. Metallutfellingsteorien ser ut til å holde og kan forklares med feller i båndgapet fra jern-bor (FeB) komplekser. Et signal som er diskutert i litteraturen er en emisjonslinje kalt VID3. Dette signalet er ikke funnet noen steder i noen av skivene undersøkt. I D1 emisjonslinjen er det funnet en hale som har to toppunkt i området 0.95 eV og 1.00 eV. Disse toppunktene er sett i andre studier av tynnfilm silisium og kan forklares med hydrogen-silisium feller i båndgapet. I en undersøkelse gjort av Ekstrøm et al. [1] på samme ingot ble det konkludert med at misorienteringsvinkler rundt en eller flere akser hadde stor innvirkning på antall dislokasjoner og levetid over frøkrystallgrensene. I denne undersøkelsen har den konklusjonen blitt undersøkt for å se om mulig korrelasjon kan bekreftes. Når det gjelder emisjonslinjene over frøkrystallgrenser er det funnet klar korrelasjon med misorienteringsvinkel om en eller flere akser. Der det er liten misorientering rundt X-aksen er det ingen eller lite defektrelaterte emisjonslinjer. Ved misorientering om Z-aksen er det mer defektrelaterte emisjonslinjer. Ved misorientering i flere akser er det funnet kaotiske frøkrystallgrenser med sterke defektrelaterte emisjonslinjer, selv om vinklene er små. En forklaring på dette er at det er flere ledige områder for urenheter å feste seg i ved misorientering i flere dimensjoner. Det konkluderes med at et samarbeid med SPL og MCR som en metode for å forbedre mono-lik silisium skiver har blitt brukt med suksess. De kjente D1-D4, D5 og D07 emisjonslinjene er funnet sammen med en ny emisjonslinje ved 0.904 ± 0.01 eV. Emisjonslinjene oppfattes ikke klarere enn emisjonslinjer i mc-Si, men D07 emisjonslinjen er funnet separert fra de andre emisjonslinjene. Dette kan være til god hjelp i framtidig forskning. Emisjonslinjene er funnet å variere mye mellom høyden til ingoten og logiske slutninger kan trekkes for å forklare hendelsene basert på kjent litteratur. Hyperspektral bildebehandling sammen med MCR kan styrke og bidra til en økt kvalitet på frø assistert mono-lik silisium skiver.M-M

A Study on Comparison of Classification Algorithms for Pump Failure Prediction

The reliability of pumps can be compromised by faults, impacting their functionality. Detecting these faults is crucial, and many studies have utilized motor current signals for this purpose. However, as pumps are rotational equipped, vibrations also play a vital role in fault identification. Rising pump failures have led to increased maintenance costs and unavailability, emphasizing the need for cost-effective and dependable machinery operation. This study addresses the imperative challenge of defect classification through the lens of predictive modeling. With a problem statement centered on achieving accurate and efficient identification of defects, this study’s objective is to evaluate the performance of five distinct algorithms: Fine Decision Tree, Medium Decision Tree, Bagged Trees (Ensemble), RUS-Boosted Trees, and Boosted Trees. Leveraging a comprehensive dataset, the study meticulously trained and tested each model, analyzing training accuracy, test accuracy, and Area Under the Curve (AUC) metrics. The results showcase the supremacy of the Fine Decision Tree (91.2% training accuracy, 74% test accuracy, AUC 0.80), the robustness of the Ensemble approach (Bagged Trees with 94.9% training accuracy, 99.9% test accuracy, and AUC 1.00), and the competitiveness of Boosted Trees (89.4% training accuracy, 72.2% test accuracy, AUC 0.79) in defect classification. Notably, Support Vector Machines (SVM), Artificial Neural Networks (ANN), and k-Nearest Neighbors (KNN) exhibited comparatively lower performance. Our study contributes valuable insights into the efficacy of these algorithms, guiding practitioners toward optimal model selection for defect classification scenarios. This research lays a foundation for enhanced decision-making in quality control and predictive maintenance, fostering advancements in the realm of defect prediction and classification

Modeling of Helium Bubble Nucleation and Growth in Neutron Irradiated RAFM Steels

Reduced Activation Ferritic/Martensitic (RAFM) steels are first candidate structural materials in future fusion technology. In this work a physically based model using Rate Theory is developed to describe nucleation and growth of helium bubbles in neutron irradiated RAFM steels. Several modifications of the basic diffusion limited model are presented allowing a comprehensive view of clustering effects and their influence on expected helium bubble size distributions

Agile Method Tailoring in a CMMI Level 5 Organization

We investigate the use and tailoring of agile methods in a highly disciplined CMMI Level 5 organization. We explore gaps between traditional agile practices and those required for enhanced levels of governance required by CMMI appraisal. We conducted a case study with recorded interviews from practitioners at NIIT Technology Ltd. The interviews were iteratively analysed and coded. Our findings show that agile methods must be supplemented with pre-sprint planning, evidence recording, project metrics, team self-organization, process standardization, and process base-lining to support the CMMI appraisal. There are challenges around Agile compliance with CMMI Level 4 processes and misconceptions about agile methods precluding documentation of the rationale for design decisions. This research contributes data to the tailoring of agile methods in a high-maturity CMMI context and will be useful for agile teams conducting level 5 appraisal