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München, Germany

Langrieger H.,BMW AG | Krafft F.,Hochschule Munich | Mensinger M.,Lehrstuhl fur Metallbau | Oefele F.,BMW AG
Journal of Laser Applications | Year: 2016

Remote laser welding of high strength aluminum alloys is still a field of extensive research due to the hot cracking phenomena. Recent research activities have been focused on center-line hot cracks in welds that are located close to the edge of the material. To avoid this type of crack from occurring, a fillet weld joint design could be utilized. However, within the fillet welds there are still transverse hot cracks present on a microscopic scale. This paper presents a thermomechanical analysis of the formation of transverse hot cracks in EN AW-6082 alloy fillet welds. In order to calculate the local deformation near the mush zone, a welding simulation based on the finite element method was created. The simulation was able to depict different settings for the welding speed, laser power, beam position, protruding length of the lower sheet, and the sheet thickness. For this purpose, an automated method for heat source calibration was developed based on image processing of polish of cross sections of different weld seams. As a result, it was possible to investigate the influencing factors on the formation of local strain and strain rate during the hot crack sensitive temperature range. It was found that the welding speed and laser power significantly increased the strain rate, but had no effect on the strain. In addition, it was determined that the position of the laser beam caused a major difference in the formation of strain and strain rate if weld seams changed from partial penetration to full penetration. Full penetration welds had lower strain and strain rate. The protruding length of the lower sheet and the sheet thickness had a minor impact on strain and strain rate. By linking the computerized results of strain and strain rate with data obtained from experiments on the hot crack susceptibility, a hot cracking criteria based on strain rate was found. © 2016 Laser Institute of America. Source

Durr A.,Hochschule Munich | Brendel C.,Hochtief Group | Borsutzky R.,Hochtief Group | Giesa I.,Hochtief Group
Bautechnik | Year: 2016

Design-and-Build Project: Design and construction of a control room with laboratory Design and build contracts are of particular interest for clients if tight schedule requirements for the completion and commissioning of buildings have to be considered and the projects have a high level of complexity. With these preconditions clients rather decide to award separate planning, procurement and construction processes with all necessary interface coordination to one contractor for reasons of efficiency. BASF SE has awarded a design and build contract to HOCHTIEF Building GmbH for a three-storey control room building with laboratory for a new production plant of toluoldiisocyanat (TDI) at the main BASF site in Ludwighafen, Germany. The planning was performed by the department Consult IKS Energy of the HOCHTIEF Engineering GmbH in Frankfurt. The scope of planning included partially the design engineering and the approval planning as well as the full detail planning for all disciplines (architectural planning, structural and façade engineering, building physics, HVAC engineering and laboratory planning). Furthermore, the reinforced concrete structure built on a pile foundation had to be designed blast wave resistant. In addition the requirement for gas tightness had to be considered in the building design, including the execution of an internal air supply in the case of emergency. © 2016 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin. Source

Petermann C.,Osnabruck University of Applied Sciences | Letzner V.,Hochschule Munich
Natur und Landschaft | Year: 2011

The paper addresses the question of how and in what context the effects of nature conservation on employment have been investigated to date. It first of all outlines in what context knowledge of the effects on employment is significant (nature conservation policy, acceptance of nature conservation measures). To illustrate which aspects, in addition to the number of jobs alone, are relevant to regional development, several regional development theories are presented briefly. This allows classification of existing studies and reveals where further research is required. Source

Rapp S.,Hochschule Munich | Rapp S.,Friedrich - Alexander - University, Erlangen - Nuremberg | Heinrich G.,TU Ilmenau | Domke M.,Vorarlberg University of Applied Sciences | Huber H.P.,Hochschule Munich
Physics Procedia | Year: 2014

In the production process of microelectronic devices and high efficiency solar cells, local openings in thin dielectric layers are required. Instead of photolithographic, laser based processing enables to open these dielectric layers locally in a low-cost mass production step. In this work, thin silicon nitride layers deposited on planar silicon wafers are processed by single infrared Gaussian shaped 660 fs laser pulses. The transparent silicon nitride layer, becoming absorptive at fluences higher than 0.3 J/cm2, is selectively removed by confined ablation at fluences below that value. At pulse peak fluences exceeding 1.0 J/cm2 a "SiNx island" is created by direct ablation in the spot center. In this article, the selective SiNx ablation by a combination of confined and direct laser ablation at the medium pulse peak fluence of 0.5 J/cm2 is investigated. To clarify the influence of the nonlinear absorption in the pulse center, the ablation behavior is investigated by time-and space-resolved pump-probe microscopy experiments. The results show phase changes in the silicon and in the silicon nitride in the first picoseconds after excitation, the ablation onset at around 10 ps and the subsequent mechanical material motion after a few nanoseconds. The actual silicon nitride layer removal starts after around 10 ns, whereas confined ablation processes are the driving mechanisms even in the nonlinearly absorbing spot center. A comparison of the energetic ablation efficiency of the SiNx layer system to further dielectric thin films shows no detrimental influence of the nonlinear absorbance. © 2014 The Authors. Published by Elsevier B.V. Source

Bucak O.,Labor fur Stahl und Leichtmetallbau GmbH | Rodic S.,Hochschule Munich | Ehard H.,Hochschule Munich | Strohbach H.,Kranbau Kothen GmbH
Stahlbau | Year: 2015

Welded rail clamps are usually used to fix the rail at the compression area of crane girders. Especially for single span beams, the stress ratios of crane runway girders are similar. For this notch detail, a clear classification in the standards is not available, so experimental investigations with the aim of a notch classification of this detail were executed. A comparison to similar notch details like the welded lamellas on beam belts shows, that welded rail clamps have an improved fatigue behavior, especially for clamps at the compression area of the girders. © 2015 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin. Source

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