On the Significance of the Die Design for Electromagnetic Sheet Metal Forming

Electromagnetic Forming is a high speed forming process using a pulsed magnetic field to form metals with high electrical conductivity, such as copper or aluminium alloys. During the process, typical pressure peaks up to 200 MPa and velocities in the range of 300 m/s can be achieved. As significant process parameters the pressure maximum as well as the local and temporal varying pressure distribution have been identified. As of a certain drawing depth and distance between workpiece and tool coil, the pressure does not act any longer on the workpiece, but the deformation process is still driven by the inertia forces. It has been found out that the velocity distribution within the sheet metal during the forming stages as well as at the time of impact with a die significantly influences the forming result. Additionally, a special undesired effect is the rebound behaviour of flat workpiece areas being in contact with the die. To investigate the influence capability of the die concerning this effect, the parameters stiffness and damping properties have been varied by means of simulation using a mechanical substitute model

Remote Sensing and the Earth

A text book on remote sensing, as part of the earth resources Skylab programs, is presented. The fundamentals of remote sensing and its application to agriculture, land use, geology, water and marine resources, and environmental monitoring are summarized

Flows in the solar atmosphere due to the eruptions on the 15th July, 2002

<p>Which kind of flows are present during flares? Are they compatible with the present understanding of energy release and which model best describes the observations? We analyze successive flare events in order to answer these questions. The flares were observed in the magnetically complex NOAA active region (AR) 10030 on 15 July 2002. One of them is of GOES X-class. The description of these flares and how they relate to the break-out model is presented in Gary & Moore (2004). The Coronal Diagnostic Spectrometer on board SOHO observed this active region for around 14 h. The observed emission lines provided data from the transition region to the corona with a field of view covering more than half of the active region. In this paper we analyse the spatially resolved flows seen in the atmosphere from the preflare to the flare stages. We find evidence for evaporation occurring before the impulsive phase. During the main phase, the ongoing magnetic reconnection is demonstrated by upflows located at the edges of the flare loops (while downflows are found in the flare loops themselves). We also report the impact of a filament eruption on the atmosphere, with flows up to 300 km s<sup>-1</sup> observed at transition-region temperatures in regions well away from the location of the pre-eruptive filament. Our results are consistent with the predictions of the break out model before the impulsive phase of the flare; while, as the flare progresses, the directions of the flows are consistent with flare models invoking evaporation followed by cooling and downward plasma motions in the flare loops.</p&gt

Aspects of Die Design for the Electromagnetic Sheet Metal Forming Process

Within the electromagnetic sheet metal forming process, workpiece velocities of more than 300m/s can occur, causing typical effects when forming into a die, which will be described and discussed in the present paper. These effects make numerous demands regarding the die design. In order to analyze these requirements, experimental as well as numerical investigations have been carried out. Thereby, special focus is put on the possibilities to accomplish these requirements, which are discussed in the following

Design and Analysis of a Deep Drawing and Inprocess Electromagnetic Sheet Metal Forming Process

The design as well as the subsequent analysis of a deep drawing and in-process electromagnetic sheet metal forming calibration will be described in this paper. Due to the quite different forming processes concerning the occurred strain rates, an investigation on the microstructure of the formed workpieces will be pointed out. Furthermore, the design steps regarding the integrated tool coil will be presented and the resulting examples discussed. Finally, the setup of the integrated process as well as the feasibility will be shown on an exemplary semi-industrial workpiece

Gravity Effects on Fluid Front Dynamics during Mold Filling

The effect of gravity on free surface shape during the filling of a disk-shaped cavity is experimentally studied. A disk-shaped mold cavity is constructed to measure spreading of the fluid front due to gravity. Fluid front sensors are mounted on the top and bottom mold walls at three radial locations. The time the fluid front reaches these sensor locations is recorded. This data is used to calculate the radial distance between the top and bottom of the fluid front at each sensor location. The important parameters that govern the fluid front dynamics are identified as the Reynolds, Bond, and Capillary numbers. Spreading is found to be mainly dependent on the Bond number, such that a large change in spreading is observed due to a small change in Bond number. Spreading increases with decreasing Capillary number and remains nearly constant over the range of Reynolds numbers studied.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline

Process Investigation of Tube Expansion by Gas Detonation

The present paper deals with the expansion of tubes by direct application of gas detonation waves, i.e. the gas is both pressure medium and energy source. After an introduction to gas detonation forming, measurements of the motion process and the internal pressures are presented. Results of free expansion and of forming into a die are thoroughly studied and compared to the results of quasi-static burst tests and hydroforming. Using pure aluminum Al99.5 and a medium strength alloy AlMgSi1, expansions by 25 % and 20 % respectively are obtained. A simulation delivers details on the deformation process and specially prepared probes of high-speed tension tests give new insight into metallographic material behavior at different strain rates

Podocyte specific knock out of selenoproteins does not enhance nephropathy in streptozotocin diabetic C57BL/6 mice

Abstract Background Selenoproteins contain selenocysteine (Sec), commonly considered the 21st genetically encoded amino acid. Many selenoproteins, such as the glutathione peroxidases and thioredoxin reductases, protect cells against oxidative stress by functioning as antioxidants and/or through their roles in the maintenance of intracellular redox balance. Since oxidative stress has been implicated in the pathogenesis of diabetic nephropathy, we hypothesized that selenoproteins protect against this complication of diabetes. Methods C57BL/6 mice that have a podocyte-specific inability to incorporate Sec into proteins (denoted in this paper as PodoTrsp-/-) and control mice were made diabetic by intraperitoneal injection of streptozotocin, or were injected with vehicle. Blood glucose, body weight, microalbuminuria, glomerular mesangial matrix expansion, and immunohistochemical markers of oxidative stress were assessed. Results After 3 and 6 months of diabetes, control and PodoTrsp-/- mice had similar levels of blood glucose. There were no differences in urinary albumin/creatinine ratios. Periodic acid-Schiff staining to examine mesangial matrix expansion also demonstrated no difference between control and PodoTrsp-/- mice after 6 months of diabetes, and there were no differences in immunohistochemical stainings for nitrotyrosine or NAD(P)H dehydrogenase, quinone 1. Conclusion Loss of podocyte selenoproteins in streptozotocin diabetic C57BL/6 mice does not lead to increased oxidative stress as assessed by nitrotyrosine and NAD(P)H dehydrogenase, quinone 1 immunostaining, nor does it lead to worsening nephropathy.http://deepblue.lib.umich.edu/bitstream/2027.42/112674/1/12882_2008_Article_98.pd

Observation and Modeling of the Solar Transition Region: II. Solutions of the Quasi-Static Loop Model

In the present work we undertake a study of the quasi-static loop model and the observational consequences of the various solutions found. We obtain the most general solutions consistent with certain initial conditions. Great care is exercised in choosing these conditions to be physically plausible (motivated by observations). We show that the assumptions of previous quasi-static loop models, such as the models of Rosner, Tucker and Vaiana (1978) and Veseckey, Antiochos and Underwood (1979), are not necessarily valid for small loops at transition region temperatures. We find three general classes of solutions for the quasi-static loop model, which we denote, radiation dominated loops, conduction dominated loops and classical loops. These solutions are then compared with observations. Departures from the classical scaling law of RTV are found for the solutions obtained. It is shown that loops of the type that we model here can make a significant contribution to lower transition region emission via thermal conduction from the upper transition region.Comment: 30 pages, 3 figures, Submitted to ApJ, Microsoft Word File 6.0/9

Development of design principles for form-fit joints in lightweight frame structures

Based on fundamental technological investigations, alternative joining strategies using electromagnetic forming (EMF) for the flexible production of lightweight frame structures are developed in the collaborative research project SFB/TR10. The results of these investigations will also be used to create general design principles for the joining process itself as well as for the joining zone. The focus of this article will be on dominating form-fit joints of aluminum frame structures and the parameters which have a significant influence on the strength of those joints. For the development of design principles regarding the joining zone, the groove geometry of the connection elements was varied in terms of size and shape, and the influence of those variations was analyzed. In terms of the joining process itself the effect on the joint strength of different forming pressures for a given groove geometry was also investigated. In the first step these experiments were performed on solid mandrels. In order to reduce the weight of the structure, experiments were then performed with hollow connection elements and similar groove geometries to analyze how the reduced stiffness of those elements affected the strength of the joints