Papers by Keyword: SSM

Abstract: This work focuses on diagnostic methodologies for composite repair patch based on structural health monitoring (SHM) technology. Methodologies based on ultrasonic guided waves (GW) are developed and assessed for monitoring composite scarf repair with piezoelectric transducers. The effectiveness of the RAPID (reconstruction algorithm for probabilistic inspection of defects) algorithm was investigated for adhesively bonded composite patch repair. A composite scarf repair has been weakened by 4-point bending fatigue test and impacted after to generate a Barely Visible Damage (BVID). Both conventional RAPID technique, which requires baseline signals, and the Scaling Subtraction Method (SSM) were applied to detect damage in the bondline. The conventional method showed good performance for defect detection and localization whereas the SSM gives encouraging results for non-linear baseline-free RAPID.

Abstract: Aluminium Rheinfelden has improved the competitiveness of semi solid processing by developing a casting process & alloy combination that is capable of ultra thin, ultra light parts having attractive engineering properties without need for full heat treatment. The THINCASTTM rheocasting process, together with Rheinfeldens Magsimal-59 alloy has been demonstrated capable of producing moderate sized castings with only 1-2 mm wall sections, thus providing a 30-50% reduction in traditional-process part weight. THINCASTTM can be adapted to a variety of die casting machines and will enable competitively improving the quality of conventional high pressure die castings as well as creating entirely new applications.

Abstract: Semi solid metal processing has numerous technical and economic advantages, such as viscous, non-turbulent flow (thus no air entrapment during casting), ability to fill ultra-thin sections (thus reduced part weight), little solidification shrinkage in the die (thus little or no porosity), minimum heat imparted to tooling (thus long tool life) and good response to T-5 aging (thus reduced heat treating costs). Still, SSM has never achieved a prominent position in the field of light metals casting Why Perhaps the reason was largely the down economy of recent years and SSM will yet emerge with the prominence once expected of it.

Abstract: Abstract. Variation modeling is one of the most significant tools for assembly variation analysis. Considering dimension and geometric errors, and part situation errors, the error source that affects assembly accuracy is classified into two types: error of geometric location and orientation, error of geometric form. And unify these different types of error or deviation by the concept of Virtual Fixture. So a rigid assembly state space model is developed for stream of variation analysis in multi-station assembly processes. And an aeroplane-cabin-assembly process is analyzed in this model. The developed methodology outperforms the current simulation based techniques in computation efficiency, the model is validated using Monte Carlo series Simulations.

Abstract: The history of semi-solid metal forming and in particular rheo-high pressure die casting at the Council for Scientific and Industrial Research in South Africa is discussed. Processing flexibility is demonstrated on the Al-Si-Mg, Al-Mg-Si, Al-Cu-Mg and Al-Zn-Mg-Cu casting and wrought alloy systems as well as on high purity aluminium, unmodified Al-Si binary eutectic, metal matrix composites and magnesium alloys. Material properties are highlighted.

Abstract: EN AC-46500 aluminium components are formed by Semi-Solid Rheocasting (SSR) in an industrial plant using a 700 tons high pressure machine. The dies wear was designed by the PLCO model of the ProCast simulation software. The components have had a good structural integrity and the mechanical properties after T6 treatment have been equivalent to that obtained by the same alloy by die cast. The present work describes the SSR forming process, the resulting microstructure as well as the optimization of the ageing heat treatment by hardness evolution. The results of the tensile tests make these clear.

Abstract: The birth of Semi-Solid Metal Forming (SSM) or as it has now come to be widely known, Thixoforming, is a typical case of development of a technological innovation. Serendipity, stroke of luck, call it what you may, the beginning of SSM is based on an almost accidental discovery by a student carrying out a series of meticulous experiments. On the one hand, some technological failures have contributed to the lack of success across the board for SSM technologies. On the other hand, the ‘long childhood’ of the resulting technology or the process of moving from ‘Innovative Idea to Market' has been largely the result of difficult and in hindsight sometimes wrong managerial decisions, occasional personality clashes, patent rights and at times unavoidable all out business 'warfare'. Of course, hindsight is beautiful but unfortunately it always comes after the event. However, if one looks carefully at some of the notable successes of SSM forming one can discern that the problems were more on the human scale; people failures rather than technology failures. This paper aims to bring out some of these points by outlining the historical development of Thixoforming.

Abstract: This paper deals with the examination of the steel grade X210CrW12 and its suitability for Thixoforming. In the semi-solid state, the microstructure of this steel consists of a homogeneous distribution of globular particles surrounded by liquid. Additionally, carbides are stabile up to fraction liquid contents of approximately 40%. After quenching, this steel reveals a globular austenitic microstructure with eutectic (former liquid phase) at the grain boundaries. Compression tests permit to determine the influence of different process parameters on the properties and the material behaviour in the semi-solid state. Their influence on the microstructure was investigated but not yet highlighted. Further investigations on this steel allow a fine-tuning to establish optimal process windows of the different thixoforming- and rheoforming- routes.

Abstract: The present work studies the effect the solution heat treatment, during artificial ageing and re-aging, has on the mechanical properties of an A357 aluminium alloy component formed by New Rheocasting. The effect that the evolution of silicon, during the solution treatment at various times, has on the mechanical properties was also examined. The mechanical properties were evaluated performing tensile tests, fractographical analysis and hardness tests. The microstructural characterization was made using optical and electronic microscopy.

Abstract: The globular microstructure required for semi solid metal (SSM) processing was initially developed by agitating melt to fragment dendrites during alpha-phase solidification. More recently, it was learned that a suitable structure was also achievable through copious nucleation of fine grains at a temperature close to the liquidus coupled with controlled cooling to prevent dendrite growth; a technique that can be applied to liquid casting processes but that is especially useful for semi solid Rheocasting (the slurry version of SSM). Rheocasting experiments were conducted to test the interactions of microstructure developed by the copious nucleation route, fractions of solid up to 0.5 during casting and slurry flow velocities up to 5 meters per second. Their combined effects on casting defects and tensile properties will be presented and discussed.