Papers by Author: Bernd Wolter

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Authors: Christoph Sklarczyk, Felix Porsch, Bernd Wolter, Christian Boller, Jochen H. Kurz
Abstract: In order to detect defects and to increase the lifetime of timber structures nondestructive methods are developed to monitor and assess their condition. Timber and wood can be characterized nondestructively and in many cases contactless with diverse methods. This paper gives a short overview on some nondestructive methods based on electromagnetic effects: microwave/radar, nuclear magnetic resonance and X-ray techniques. To monitor the stress condition of the joints in timber structures some other techniques like micromagnetic methods, acoustic resonance analysis and ultrasonic stress analysis are to be considered.
Authors: Benjamin Strass, Guntram Wagner, Christian Conrad, Bernd Wolter, Sigrid Benfer, Wolfram Fürbeth
Abstract: Fusion welding of dissimilar metals is in the most cases difficult or even impossible as a result of different melting points and the development of undesirable brittle intermetallic phases. This often leads to joint strengths considerable below the tensile strength of the base materials. By using Friction Stir Welding (FSW) it is possible to reduce the development of the intermetallic phases of Al/Mg-joints significantly but not to avoid them completely. Hence a hybrid welding system at the WKK of the University of Kaiserslautern was developed called “Ultrasound Supported Friction Stir Welding (US-FSW)” with the aim to shatter the brittle interlayer lines and to scatter fragments in the welding area during the FSW process. Pre-investigations have shown that for Al/Mg-US-FSW-joints the strength can be increased up to 30% in comparison to conventional FSW. Moreover for the reliable detection of nonconformities in the weld during a post-process inspection by suitable non-destructive testing (NDT) methods is necessary. Also there is a strong need for better process monitoring and control by in-process NDT methods. Furthermore the corrosion behavior of the basic materials and hybrid-joints was investigated by electrochemical methods indicating an increased corrosion of the Mg alloy in the area of the Al/Mg-butt weld.
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