Mechanical Properties Characterization of Welded Automotive Steels

Among the various welding technologies, resistance spot welding (RSW) and laser beam welding (LBW) play a significant role as joining methods for the automobile industry. The application of RSW and LBW for the automotive body alters the microstructure in the welded areas. It is necessary to identify the mechanical properties of the welded material to be able to make a reliable statement about the material behavior and the strength of welded components. This study develops a method by which to determine the mechanical properties for the weldment of RSW and LBW for two dual phase (DP) steels, DP600 and DP1000, which are commonly used for the automotive bodies. The mechanical properties of the resistance spot weldment were obtained by performing tensile tests on the notched tensile specimen to cause an elongation of the notched and welded area in order to investigate its properties. In order to determine the mechanical properties of the laser beam weldment, indentation tests were performed on the welded material to calculate its force-penetration depth-curve. Inverse numerical simulation was used to simulate the indentation tests to determine and verify the parameters of a nonlinear isotropic material model for the weldment of LBW. Furthermore, using this method, the parameters for the material model of RSW were verified. The material parameters and microstructure of the weldment of RSW and LBW are compared and discussed. The results show that the novel method introduced in this work is a valid approach to determine the mechanical properties of welded high-strength steel structures. In addition, it can be seen that LBW and RSW lead to a reduction in ductility and an increase in the amount of yield and tensile strength of both DP600 and DP1000

The Impact of Continuous Glucose Monitoring in the Management of Type II Diabetes

According to the American Diabetes Association (ADA), approximately 36 million Americans have a diagnosis of type II diabetes (T2D). Among these patients with T2D, nearly forty percent have glycated hemoglobin A1c (Hgb A1c) values above the target goal of 7%. Many patients with T2D utilize self-monitoring blood glucose (SMBG) systems to monitor day-to-day fluctuations in blood glucose values. However, SMBG systems can be cumbersome and may result in lower patient compliance. With many patients struggling to achieve their target Hgb A1c, methods to improve glycemic control are needed to prevent long-term diabetes-related complications. This literature review aims to investigate the benefits of initiating continuous glucose monitoring (CGM) in patients with T2D receiving various treatment regimens. A literature review was performed using electronic search databases PubMed, CINAHL, and Embase from May 5 to September 15, 2021. Keywords were diabetes mellitus, type 2, type 2 diabetes, cgm, continuous blood glucose monitoring, Freestyle Libre, and Dexcom. The search yielded around 387 articles. Exclusion criteria consisted of specific articles which focused on specific patient populations including type I diabetes (T1D) rather than T2D, along with pregnant, hemodialyzed, inpatient, and elderly patients with T2D. A total of 13 research articles were reviewed. Current literature suggests that initiating CGM in patients with T2D results in significant reductions in Hgb A1c, regardless of treatment regimen. Given the prevalence of T2D, applying this research with clinical application could help patients achieve their target Hgb A1c and subsequently reduce the risk of long-term diabetes-related complications

Deep Denoising for Hearing Aid Applications

Reduction of unwanted environmental noises is an important feature of today's hearing aids (HA), which is why noise reduction is nowadays included in almost every commercially available device. The majority of these algorithms, however, is restricted to the reduction of stationary noises. In this work, we propose a denoising approach based on a three hidden layer fully connected deep learning network that aims to predict a Wiener filtering gain with an asymmetric input context, enabling real-time applications with high constraints on signal delay. The approach is employing a hearing instrument-grade filter bank and complies with typical hearing aid demands, such as low latency and on-line processing. It can further be well integrated with other algorithms in an existing HA signal processing chain. We can show on a database of real world noise signals that our algorithm is able to outperform a state of the art baseline approach, both using objective metrics and subject tests.Comment: submitted to IWAENC 201

Quantifying Mechanical Properties of Automotive Steels with Deep Learning Based Computer Vision Algorithms

This paper demonstrates that the instrumented indentation test (IIT), together with a trained artificial neural network (ANN), has the capability to characterize the mechanical properties of the local parts of a welded steel structure such as a weld nugget or heat affected zone. Aside from force-indentation depth curves generated from the IIT, the profile of the indented surface deformed after the indentation test also has a strong correlation with the materials’ plastic behavior. The profile of the indented surface was used as the training dataset to design an ANN to determine the material parameters of the welded zones. The deformation of the indented surface in three dimensions shown in images were analyzed with the computer vision algorithms and the obtained data were employed to train the ANN for the characterization of the mechanical properties. Moreover, this method was applied to the images taken with a simple light microscope from the surface of a specimen. Therefore, it is possible to quantify the mechanical properties of the automotive steels with the four independent methods: (1) force-indentation depth curve; (2) profile of the indented surface; (3) analyzing of the 3D-measurement image; and (4) evaluation of the images taken by a simple light microscope. The results show that there is a very good agreement between the material parameters obtained from the trained ANN and the experimental uniaxial tensile test. The results present that the mechanical properties of an unknown steel can be determined by only analyzing the images taken from its surface after pushing a simple indenter into its surface

Reflective Assessment: Opportunities and Challenges

Purpose: Librarians engage in assessment for several purposes, such as to improve teaching and learning, or to report institutional value. In turn, these assessments shape our perspectives and priorities. How can we participate critically in the assessment of information literacy instruction and library programming while broadening our view and making room for questions about what we do? This paper explores self-reflection as a method for building on existing assessment practices with a critical consciousness. Design/Methodology/Approach: In tracing the trajectory of assessment and reflective practice in library literature, the authors conducted a selective literature review and analyzed the potential impact of incorporating librarian self-reflection into assessment practices, particularly for instructional services. The authors’ experiences with strategies informed by these conversations were also described. Findings: Self-reflection has typically been employed to improve teaching or as a method of assessing student learning. However, it can also be used to develop a critical awareness of what we accomplish through the act of assessing. The authors develop and present self-reflective strategies and discuss their benefits and limitations. Practical Implications: An extensive list of strategies was developed to illustrate practical examples of a reflective approach to assessment. Originality/Value: Although librarians have used reflection as a type of assessment strategy, we have not viewed self-reflection as a method for evaluating other assessment techniques. Librarians interested in exploring reflective practice and thinking critically about assessment will find strategies and suggestions for doing so

Bedeutung des intrinsischen apoptotischen Signaltransduktionsweges für den Phagozytose-induzierten Zelltod von adulten und neonatalen Monozyten

Neugeborene zeigen eine verlängerte Inflammationsdauer nach bakterieller Infektion, was mit Folgeerkrankungen wie Periventrikulärer Leukomalazie oder Bronchopulmonaler Dysplasie assoziiert ist. Der Phagozytose-induzierte Zelltod (PICD) von Monozyten ist von entscheidender Bedeutung für die Beendigung einer Immunreaktion und frühere Studien zeigten, dass der PICD in neonatalen Monozyten vermindert ist, wobei die genauen Mechanismen bisher nicht geklärt sind. In der vorliegenden Arbeit sollte der Einfluss der Apoptose-regulierenden Bcl-2-Proteine auf den PICD von Monozyten untersucht werden. Dazu wurde die mRNA- und Proteinexpression mittels Realtime-PCR und Durchflusszytometrie der Bcl-2-Proteine in mit E. coli infizierten neonatalen und adulten Monozyten bestimmt. Die mRNA-Expression des anti-apoptotischen Bcl-xL wurde hochreguliert in neonatalen Monozyten und das pro-apoptotische Bax wurde in infizierten adulten Monozyten mehr exprimiert als in neonatalen Monozyten. Das Gleichgewicht zwischen pro- und anti-apoptotischen Proteinen war in neonatalen Monozyten zugunsten des Überlebens der Zellen verschoben. Die Ergebnisse zeigen den Einfluss der Bcl-2-Proteine auf den Zelltod in Monozyten und stellen einen weiteren Schritt zum Verständnis der verlängerten Inflammation von Neugeborenen dar

Is the soil moisture precipitation feedback enhanced by heterogeneity and dry soils? A comparative study

The interaction between the land surface and the atmosphere is a crucial driver of atmospheric processes. Soil moisture and precipitation are key components in this feedback. Both variables are intertwined in a cycle, that is, the soil moisture – precipitation feedback for which involved processes and interactions are still discussed. In this study the soil moisture – precipitation feedback is compared for the sempiternal humid Ammer catchment in Southern Germany and for the semiarid to subhumid Sissili catchment in West Africa during the warm season, using precipitation datasets from the Climate Hazards Group InfraRed Precipitation with Station data (CHIRPS), from the German Weather Service (REGNIE) and simulation datasets from the Weather Research and Forecasting (WRF) model and the hydrologically enhanced WRF-Hydro model. WRF and WRF-Hydro differ by their representation of terrestrial water flow. With this setup we want to investigate the strength, sign and variables involved in the soil moisture – precipitation feedback for these two regions. The normalized model spread between the two simulation results shows linkages between precipitation variability and diagnostic variables surface fluxes, moisture flux convergence above the surface and convective available potential energy in both study regions. The soil moisture – precipitation feedback is evaluated with a classification of soil moisture spatial heterogeneity based on the strength of the soil moisture gradients. This allows us to assess the impact of soil moisture anomalies on surface fluxes, moisture flux convergence, convective available potential energy and precipitation. In both regions the amount of precipitation generally increases with soil moisture spatial heterogeneity. For the Ammer region the soil moisture – precipitation feedback has a weak negative sign with more rain near drier patches while it has a positive signal for the Sissili region with more rain over wetter patches. At least for the observed moderate soil moisture values and the spatial scale of the Ammer region, the spatial variability of soil moisture is more important for surface-atmosphere interactions than the actual soil moisture content. Overall, we found that soil moisture heterogeneity can greatly affect the soil moisture – precipitation feedback

Finite element analysis of in-situ distortion and bulging for an arbitrarily curved additive manufacturing directed energy deposition geometry

With the recent rise in the demand for additive manufacturing (AM), the need for reliable simulation tools to support experimental efforts grows steadily. Computational welding mechanics approaches can simulate the AM processes but are generally not validated for AM-specific effects originating from multiple heating and cooling cycles. To increase confidence in the outcomes and to use numerical simulation reliably, the result quality needs to be validated against experiments for in-situ and post-process cases. In this article, a validation is demonstrated for a structural thermomechanical simulation model on an arbitrarily curved Directed Energy Deposition (DED) part: at first, the validity of the heat input is ensured and subsequently, the model’s predictive quality for in-situ deformation and the bulging behaviour is investigated. For the in-situ deformations, 3D-Digital Image Correlation measurements are conducted that quantify periodic expansion and shrinkage as they occur. The results show a strong dependency of the local stiffness of the surrounding geometry. The numerical simulation model is set up in accordance with the experiment and can reproduce the measured 3-dimensional in-situ displacements. Furthermore, the deformations due to removal from the substrate are quantified via 3D-scanning, exhibiting considerable distortions due to stress relaxation. Finally, the prediction of the deformed shape is discussed in regards to bulging simulation: to improve the accuracy of the calculated final shape, a novel extension of the model relying on the modified stiffness of inactive upper layers is proposed and the experimentally observed bulging could be reproduced in the finite element model

Seebeck coefficients of half-metallic ferromagnets

In this report the Co2 based Heusler compounds are discussed as potential materials for spin voltage generation. The compounds were synthesized by arcmelting and consequent annealing. Band structure calculations were performed and revealed the compounds to be half-metallic ferromagnets. Magnetometry was performed on the samples and the Curie temperatures and the magnetic moments were determined. The Seebeck coefficients were measured from low to ambient temperatures for all compounds. For selected compounds high temperature measurements up to 900 K were performed.Comment: accepted contribution o the Special Issue "Spin Caloritronics" of Solid State Communication

Build-up strategies for additive manufacturing of three dimensional Ti-6Al-4V-parts produced by laser metal deposition

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Journal of Laser Applications 30, 022001 (2018) and may be found at https://doi.org/10.2351/1.4997852.Laser metal deposition (LMD) has been applied as a coating technology for many years. Today, the technologies capacity to produce 3D depositions leads to a new field of application as additive manufacturing method. In this paper, 3D laser metal deposition of titanium alloy Ti-6Al-4 V is studied with special regard to the demands of additive manufacturing. Therefore, only the coaxial LMD powder nozzle is used to create the shielding gas atmosphere, which ensures high geometric flexibility. Furthermore, specimen with high aspect ratio and hundreds of layers are manufactured, which represent typical features in additive manufacturing. The presented study contains the following steps: First, cylindrical specimens are manufactured with a standard shell-core build-up strategy and mechanical properties as well as fracture mechanisms are determined. Based on the results, experiments are conducted to improve the build-up strategy and new tensile test specimens are built with the improved strategy. The improved strategy incorporates variable track overlap ratios to achieve a constant growth in the shell and core area. As blanks, lean cylinders comprising more than 240 layers and a height of more than 120 mm are manufactured. The specimens are analyzed by X-ray inspection for material defects. Fractured surfaces are observed via scanning electron microscopy and the composition of the surfaces is determined using energy dispersive X-ray spectroscopy. The tensile test results prove mechanical properties close to ASTM F1108 specification for wrought material