Πλοήγηση ανά Συγγραφέα "David, C."
Τώρα δείχνει 1 - 5 από 5
- Αποτελέσματα ανά σελίδα
- Επιλογές ταξινόμησης
Τεκμήριο Current injection phase thermography for low-velocity impact damage identification in composite laminates(2014-03) Grammatikos, S. A.; Kordatos, E. Z.; Matikas, T. E.; David, C.; Paipetis, A. S.An innovative non-destructive evaluation (NDE) technique is presented based on current stimulated thermography. Modulated electric current is injected to Carbon Fibre Reinforced Plastics (CFRP) laminates as an external source of thermal excitation. Pulsed Phase Thermography (PPT) is concurrently employed to identify low velocity impact induced (LVI) damage. The efficiency of the proposed method is demonstrated for both plain and with Carbon Nanotubes (CNTs) modified laminates, which are subjected to low-velocity impact damaged composite laminates at different energy levels. The presence of the nano reinforcing phase is important in achieving a uniform current flow along the laminate, as it improves the through thickness conductivity. The acquired thermographs are compared with optical PPT, C-scan images and Computer Tomography (CT) representations. The typical energy input for successful damage identification with current injection is three to four orders of magnitude less compared to the energy required for optical PPT.Τεκμήριο Evaluation of the fatigue behavior of Aluminide Coating Steel Substrate Compounds by means of the Impact Testing Method(2011-03) Anthymidis, K. G.; David, C.; Tsipas, D. N.The impact testing is an efficient experimental method that enables the quantitative and qualitative evaluation of the fatigue resistance of mono- and multilayer coatings deposited on various substrates, which was not possible with the common testing methods previously available. In this article the experimental assessment of the fatigue resistance of aluminide slurry coatings working under cyclic loading conditions by means of the dynamic impact testing method is presented. The fatigue failure mode, such cohesive or adhesive, of the investigated coatings is determined using scanning electron and optical microscopy, as well as Energy Dispersive X-ray (EDX) analysis. Critical values of impact load responsible for distinctive fatigue failure modes of the coating substrate system are obtained.Τεκμήριο Experimental and computational investigation of end-milling and development of a simulation model describing the machining process(2011-08) David, C.; Antoniadis, A.; Friderikos, O.; Sagris, D.Modern requirements in manufacturing industry for mechanical products of better quality and higher accuracy machined by material removal, and the pursuit of minimization of the production costs, in conjunction with the growing complexity of the product geometry, led to further development of the computer numerically controlled (CNC) machine tools, and of the respective CAD/CAM systems. However not enough progress is occurred with emphasis on the development of computational systems, which can determine the most efficient cutting conditions, taking also into account the dynamic behavior of the machine tool system and the tool path planning. This paper is proposing an experimental-computational method in terms of appropriate simulation model, which allows the selection of optimum cutting conditions in end-milling processes, taking into consideration the workpiece surface quality, the developed cutting forces, the vibration deflections in the cutting zone, as well as the strategy of the tool path planning. Finally, the objective of the paper is to deliver an innovative methodology capable to be exploited in manufacturing industry with following benefits: • Increase of the material removal rate • Improvement of the workpiece surface • Increase of the cutting tool life • Restriction of faulty products • Reduction of costs and machining time with increase of productivityΤεκμήριο Interregional technology transfer on advanced materials and renewable energy systems(2008) Agrianidis, P.; David, C.; Anthymidis, K.; Ekhrawat, M.Advanced materials are used in most industrial sectors and human activities and all developing and developed countries as well as international organizations eg. United Nations have established work groups, which survey the national and global state and developments in the area of advanced materials trying to establish strategies on that crucial technology sector. These strategies are focused on research and technology activities including education and vocation training, as well as stimulus for the starting up of new industrial applications. To introduce such a concept in Greece and especially in Northern Greece, the Technological Education Institute of Serres has initiated an Interregional technology transfer project in this scientific field. This project includes mod topics of advanced materials technology with emphasison specific industrial applications (renewable energy systems). The project demonstrates the development of a prototype photovoltaic thermal system in terms of a new industrial product. The product development procedure consists of steps such as initial product design, materials selection and processing, prototype design and manufacturing, quality control, performance optimization, but also control of materials ecocompatibility according to the national trends of life cycle design and recycling techniques. Keywords: Interregional technology transfer, materials, renewable energy systemsΤεκμήριο Investigation of shear instability in orthogonal machining of TI6AL4V alloy using the finite element method(2011-06) Friderikos, O.; Korlos, A.; David, C.; Tsiafis, I.During orthogonal cutting of Ti6Al4V alloy the chip is segmented, suggesting the emergence of some kind of instability during plastic deformation of the material. The segmented chip formation occurs from low cutting speeds and persists even at very high speeds, but with a notable change of the chip morphology. Considerable research efforts have been conducted worldwide to explain the underlying physical mechanisms of the segmented chip formation, and several theoretical models have been proposed. Theoretical models based on thermally aided shear instability which results to adiabatic shear bands formation proposed to explain the plastic instability of the material at high deformation rate s. Unfortunately, these models cannot provide answers at low deformation rates. On the other hand, fracture models which consider machining as a mechanism of ductile or brittle fracture explain the segmented chip formation as a periodic crack generation mechanism . Despite the above theoretical approaches, the phenomenon is still not well understood. The objective of this work is to investigate the mechanisms of catastrophic shear instability during orthogonal cutting of Ti6Al4V alloy based on coupled thermomechanical rigid viscoplastic finite element simulations in a wide range of cutting speeds