EFD Induction (Norway)

The primary objective of this study is to explore the impact of temperature and magnesium addition on the partial oxygen potential in lamellar, compacted, and spheroidal cast irons during the cooling process. The oxygen potential is assessed in large‐scale plant trials with a 1000 kg scale. Thermodynamic calculations are conducted, and the results are compared with the experimental values. There is a reasonable agreement between the experimental and calculated values, facilitating the prediction of oxygen potential in temperature ranges where measurements are challenging. According to the thermodynamic calculations, it is observed that varying amounts of added magnesium result in the formation of different types of inclusions during cooling. This, in turn, influences the temperature dependency of the oxygen potential in the molten metal.

PurposeAdditive manufacturing (AM) is a rapidly evolving manufacturing process, which refers to a set of technologies that add materials layer-by-layer to create functional components. AM technologies have received an enormous attention from both academia and industry, and they are being successfully used in various applications, such as rapid prototyping, tooling, direct manufacturing and repair, among others. AM does not necessarily imply building parts, as it also refers to innovation in materials, system and part designs, novel combination of properties and interplay between systems and materials. The most exciting features of AM are related to the development of radically new systems and materials that can be used in advanced products with the aim of reducing costs, manufacturing difficulties, weight, waste and energy consumption. It is essential to develop an advanced production system that assists the user through the process, from the computer-aided design model to functional components. The challenges faced in the research and development and operational phase of producing those parts include requiring the capacity to simulate and observe the building process and, more importantly, being able to introduce the production changes in a real-time fashion. This paper aims to review the role of robotics in various AM technologies to underline its importance, followed by an introduction of a novel and intelligent system for directed energy deposition (DED) technology.Design/methodology/approachAM presents intrinsic advantages when compared to the conventional processes. Nevertheless, its industrial integration remains as a challenge due to equipment and process complexities. DED technologies are among the most sophisticated concepts that have the potential of transforming the current material processing practices.FindingsThe objective of this paper is identifying the fundamental features of an intelligent DED platform, capable of handling the science and operational aspects of the advanced AM applications. Consequently, we introduce and discuss a novel robotic AM system, designed for processing metals and alloys such as aluminium alloys, high-strength steels, stainless steels, titanium alloys, magnesium alloys, nickel-based superalloys and other metallic alloys for various applications. A few demonstrators are presented and briefly discussed, to present the usefulness of the introduced system and underlying concept. The main design objective of the presented intelligent robotic AM system is to implement a design-and-produce strategy. This means that the system should allow the user to focus on the knowledge-based tasks, e.g. the tasks of designing the part, material selection, simulating the deposition process and anticipating the metallurgical properties of the final part, as the rest would be handled automatically.Research limitations/implicationsThis paper reviews a few AM technologies, where robotics is a central part of the process, such as vat photopolymerization, material jetting, binder jetting, material extrusion, powder bed fusion, DED and sheet lamination. This paper aims to influence the development of robot-based AM systems for industrial applications such as part production, automotive, medical, aerospace and defence sectors.Originality/valueThe presented intelligent system is an original development that is designed and built by the co-authors J. Norberto Pires, Amin S. Azar and Trayana Tankova.

ABSTRACTThis paper quantifies the soft switching loss of a 1.2 kV SiC MOSFET module via a calorimetric method in a 78 kW full-bridge resonant inverter switched at approximately 200 kHz. By switching the SiC MOSFET just before the zero crossing of the current during turn-off and at perfect zero voltage during turn-on, this converter yielded an efficiency of roughly 99 %. Then, a simplified laboratory setup, including only a half-bridge series resonant inverter topology with split DC-link capacitors and an LC load, was built such that a real inverter operation was emulated, and thereby, turn-off loss was measured via an electrical method. A discrepancy of approximately 10 % is found between the two loss measurement methods, and the possible source for this difference is discussed. Furthermore, a standard double pulse test was also performed in an inductive clamped buck converter for measuring the hard switching loss. Finally, a comparison of losses obtained from the hard versus resonant topologies at the same load current was accomplished, which verifies the substantial benefits of the latter over the former. Thus, the merits of SiC MOSFETs for high frequency soft switched converters are demonstrated, which is the main contribution of this paper.

This paper investigates the switching performance of a 1.2 kV half-bridge SiC MOSFET module from Sanrex. Unlike in a standard SiC MOSFET module, where the MOSFET and the anti-parallel diode chips are fabricated separately, in the chosen MOSFET module (FCA150XB120), both the MOSFET and the diode are fabricated on a single chip. The device is characterized under both hard and soft switching conditions. For the hard switching characterization, an inductive clamped buck converter is employed, whereas for the soft switching characterization, a resonant half-bridge converter with LC load is used. A comparison of the hard switching loss is performed with the soft switching loss at the same current. This comparison provides insight into the significance of employing an appropriate circuit topology, load and control scheme to reflect the waveforms as in a real application, in order to get a more accurate assessment of the switching losses that will occur. This insight is the main contribution of this paper.

ABSTRACTA seismic trace is assumed to consist of a known signal pulse convolved with a reflection coefficient series plus a moving average noise process (colored noise). Multiple reflections and reverberations are assumed to be removed from the trace by conventional means. The method of maximum likelihood (ML) is used to estimate the reflection coefficients and the unknown noise parameters. If the reflection coefficients are known from well logs, the seismic pulse and the noise parameters can be estimated.The maximum likelihood estimation problem is reduced to a nonlinear least‐squares problem. When the further assumption is made that the noise is white, the method of maximum likelihood is equivalent to the method of least squares (LS). In that case the sampling rate should be chosen approximately equal to the Nyquist rate of the trace. Statistical and numerical properties of the ML‐ and the LS‐estimates are discussed briefly. Synthetic data examples demonstrate that the ML‐method gives better resolution and improved numerical stability compared to the LS‐method.A real data example shows the ML‐ and LS‐method applied to stacked seismic data. The results are compared with reflection coefficients obtained from well log data.

Regional left ventricular function was studied serially by quantitative two-dimensional echocardiography (2-D echo) in 20 dogs after left anterior descending coronary artery ligation. Normal values for regional myocardial thickening were established in 20 healthy dogs and used as a standard to recognize abnormally contracting segments (ACS). In normal hearts, the mean percent thickening tended to increase from base (25.8%) to apex (34.0%), but showed considerable diversity from segment to segment (range 20.0-40.0%); nevertheless, at least some degree of thickening was seen in every segment. After coronary occlusion, myocardial segments either thinned or failed to thicken. At the papillary muscle level, there was an improvement in function between 2 and 48 hours, with thinning at 2 hours and thickening at 48 hours. Tissue infarct size (IS) determined at 48 hours was related to IS derived from a weighted summation of ACS at 2, 24 and 48 hours. At 2 hours, ACS considerably overpredicted and correlated poorly with tissue IS (25.3% vs 13.4%; r = 0.60); by 48 hours, IS predicted by ACS had decreased to 15.3% (p less than 0.05) and had an improved, but only fair correlation with tissue IS (r = 0.73, SEE = 4.9%). We conclude that there is considerable heterogeneity to myocardial thickening by 2-D-echo, but failure to thicken is not seen in the normal dog heart. In many dogs, the extent of myocardial dysfunction 2 hours after coronary ligation exceeds that seen later. Tissue IS is difficult to predict accurately from ACS. Since the amount of muscle dysfunction is not necessarily equivalent to the amount of tissue necrosis in acute myocardial infarction, ACS may be more appropriate used to tract the course of infarction rather than to predict IS.

Ved Mergel forstaar man - i videste Udstrækning - ethvert Jordlag, der udgør en Blanding af kulsur Kalk med Ler og (eller) Sand uden Hensyn til Blandingsdelenes indbyrdes Mængdeforhold. Betegnelsen kan saaledes bruges om Jordarter af meget forskellig Art. Det, der er fælles for dem alle, er det større eller mindre Indhold af kulsur Kalk.Imidlertid kan Begrebet begrænses fra forskellig Side, saaledes at ikke alle kalkholdige Aflejringer kommer ind under Betegnelsen Mergel. Dels vil saadanne Lag som Kridt og Kalk, der saa godt som udelukkende bestaar af kulsur Kalk, ikke høre ind under Begrebet Mergel, selv om de paaføres Jorden i samme Øjemed som Mergelen. Dels er der kalkholdige Sand- og Lerlag, hvor dog Indholdet af kulsur Kalk er saa ringe, at Karakteren af Mergel bortfalder. Grænsen for det Mindstemaal af Kalkindhold, der skal kræves, for at et Jordlag kan kaldes Mergel, er det imidlertid umuligt at fastsætte, - naar den ikke sættes ved Kalkholdighed lig Nul -, da denne Grænse altid i Praksis vil være betinget af hvert enkelt givet Steds Krav og Behov og Adgangsmuligheder. Et kalkholdigt Jordlag, der under visse Omstændigheder vil blive anset som brugbar Mergel, vil man paa andre Steder og under andre Forhold ikke regne med som saadan.