26 research outputs found
Thermo-Mechanical Modeling of Thin Wall Builds using Powder Fed Directed Energy Deposition ✶ ✶Portions of this text are reproduced from Heigel, Michaleris, Reutzel, 2015, “Thermo-mechanical model development and validation of directed energy deposition additive manufacturing of Ti-6Al-4V,” Additive Manufacturing, V5. with permission from Elsevier.
No full textLA-ICP-MS detrital zircon standards results
No full textThis dataset contains isotope ratios, ages, weighted averages and trace element concentrations for standards used during LA-ICP-MS analysis of detrital zircons from the Adelaide Superbasin as part of a PhD project undertaken by Jarred C Lloyd at the University of Adelaide. Full methodology is available in the linked pre-prints/publications.V2 corrected error with an author name.</div
The Effects of Integration Time and Size-of-Source on the Temperature Measurement of Segmented Chip Formation Using Infrared Thermography
No full textThis paper illustrates the errors due to integration time and size-of-source effects when measuring the temperature of segmented chip formation using infrared (IR) thermography. Segmented chip formation involves narrow periodic shear bands that experience rapid heating and move at high velocities and accelerations. As a result, the values of the measured temperatures depend strongly on the temporal and spatial measurement window used. In this study, an ideal infrared camera is simulated to understand the effects of integration time and size-of-source on the measurement. This analysis does not consider the temporal and spatial transfer functions of the camera system, thus simplifying the analysis to be applicable to all IR thermography users. Incorporating appropriate transfer functions would make the analysis specific to a given camera system. Finite element analysis (FEA) simulation results provide a reference cutting process which is manipulated to mimic motion blur and size-of-source effects. For this purpose, the FEA results adequately represent the cutting process with rapid heating and high chip velocities. For the studied cases, size-of-source has relatively little impact on the measurement results when compared to the effects of integration time. Results show integration times from 1 μs to 90 μs significantly affect the measurement results. The maximum temperature measured by the simulated IR camera decreases from an FEA maximum of 735 °C to 668 °C at 90 μs integration time. Integration time significantly affects temperature measurement in the periodic shear band but does not significantly affect the simulated measurement error of the chip temperature near the tool rake face.</jats:p
The Effects of Emissivity and Camera Point Spread Function on the Temperature Measurement of Segmented Chip Formation Using Infrared Thermography
No full textThis paper uses simulation to investigate measurement errors resulting from the camera point spread function (PSF) when measuring the temperature of segmented chip formation using infrared (IR) thermography. The PSF of the IR camera effectively filters the results which can cause significant errors due to the large temperature gradients and abrupt transitions between features and their corresponding emissivity values. The different emissivity values of the tool, workpiece, chip body, and shear band affect the apparent difference in the emitted energy of these different features. This decreases the measured temperature in the regions of most interest: along the tool-chip interface and the periodic shear zone. The method in this study creates an appropriate emissivity map from post-process measurements and applies it to results from the temperature distribution of the cutting zone predicted by commercial finite element analysis (FEA) software. Comparisons between the simulation results and experiment results show that the emissivity values obtained form the post process chip analysis lead to good agreement. The resulting radiant intensity distribution becomes the input for an IR camera simulation module developed by the authors and presented in earlier work [1]. The earlier work used the true temperature distribution predicted by the FEA as the simulation module input, and did not incorporate the IR camera’s PSF. Implementation of the actual IR camera’s PSF allows the simulation module to more accurately represent the measurements of the IR camera and ultimately allow the comparison of the simulation results to the measurement results. Simulation results show that the PSF accounts for 45% of the 42 °C radiance temperature error at the tool-chip contact along the rake face. The PSF accounts for approximately 15% of the 46 °C radiance temperature measurement error at a point in the center of the catastrophic shear band. These errors consider the effects of motion blur (integration time) and magnification (size-of-source), as described in the earlier work [1].</jats:p
In Situ Thermography During Laser Powder Bed Fusion of a Nickel Superalloy 625 Artifact with Various Overhangs and Supports
No full text
Topographic Measurement of Individual Laser Tracks in Alloy 625 Bare Plates
No full textdditive manufacturing (AM) combines all of the complexities of materials processing and manufacturing into a single process. The digital revolution made this combination possible, but the commercial viability of these technologies for critical parts may depend on digital process simulations to guide process development, product design, and part qualification. For laser powder bed fusion, one must be able to model the behavior of a melt pool produced by a laser moving at a constant velocity over a smooth bare metal surface before taking on the additional complexities of this process. To provide data on this behavior for model evaluations, samples of a single-phase nickel-based alloy were polished smooth and exposed to a laser beam at three different power and speed settings in the National Institute of Standards and Technology Additive Manufacturing Metrology Testbed and a commercial AM machine. The solidified track remaining in the metal surface after the passing of the laser is a physical record of the position of the air-liquid-solid interface of the melt pool trailing behind the laser. The surface topography of these tracks was measured and quantified using confocal laser scanning microscopy for use as benchmarks in AM model development and validation. These measurements are part of the Additive Manufacturing Benchmark Test Series.</p
Quality and Safety Aspects of Infant Nutrition
Full text linkQuality and safety aspects of infant nutrition are of key importance for child health, but oftentimes they do not get much attention by health care professionals whose interest tends to focus on functional benefits of early nutrition. Unbalanced diets and harmful food components induce particularly high risks for untoward effects in infants because of their rapid growth, high nutrient needs, and their typical dependence on only one or few foods during the first months of life. The concepts, standards and practices that relate to infant food quality and safety were discussed at a scientific workshop organized by the Child Health Foundation and the Early Nutrition Academy jointly with the European Society for Paediatric Gastroenterology, Hepatology and Nutrition, and a summary is provided here. The participants reviewed past and current issues on quality and safety, the role of different stakeholders, and recommendations to avert future issues. It was concluded that a high level of quality and safety is currently achieved, but this is no reason for complacency. The food industry carries the primary responsibility for the safety and suitability of their products, including the quality of composition, raw materials and production processes. Introduction of new or modified products should be preceded by a thorough science based review of suitability and safety by an independent authority. Food safety events should be managed on an international basis. Global collaboration of food producers, food-safety authorities, paediatricians and scientists is needed to efficiently exchange information and to best protect public health. Copyright (C) 2012 S. Karger AG, Base
Infrared measurement of the temperature at the tool–chip interface while machining Ti–6Al–4V
No full textClick on the DOI link to access the article (may not be free).The challenges associated with machining titanium alloys (e.g.,Ti-6Al-4V) are directly related to high cutting tool temperatures due to the low thermal conductivity of these alloys and the heat generated in the primary shear zone and at the tool-chip interface. Transparent yittrium aluminum garnet (YAG) tools are used in the current study to orthogonally machine a Ti-6Al-4V disk. Although YAG tools are not industrially relevant, they permit the temperature on the tool-chip interface to be measured. These measurements are relevant because they can be used to validate cutting models, which are in-turn used by industry to improve cutting processes. An infrared camera, using a high frame rate (700 Hz) and a large field of view (20 mm(2)), observes the tool-chip interface through these tools and measures the temperature distribution and records the chip curl and breakage while cutting with a feed rate of 50 mu m/rev and cutting speeds between 20 m/min and 100 m/min. In addition to the temperature measureirlents, cutting forces are recorded and the chip formation is documented using a high-speed (3 kHz) visible-light camera. Results show that radiant temperature increases with speed while the cutting and thrust fortes show no significant trend. Analysis of the temperature distribution from one edge of the chip to the other reveals differences from 6 % to 21 %, indicating that caution must be used when performing thermographic measurements of chip temperatures from the side of the cutting zone. Finally, post process measurements are performed using a scanning white-light interferometer to investigate any correlation between the tool condition and cutting temperature. Although the qualitative analysis of some cases appears to reveal a correlation between the condition of the YAG tool and the measured temperature distribution, further work work is required to understand this relationship.Department of Energy contract number DE-EE0006396
