Results 1 - 10 of 2430
Results 1 - 10 of 2430. Search took: 0.038 seconds
|Sort by: date | relevance|
[en] Earlier work showed how problems of plasticity in the plane can be studied by means of slip lines, and possibly with flow lines. In axisymmetric extrusion the construction of slipe lines becomes difficult and the whole study was finally carried out by flow lines. The chief methods using flow lines in axial symmetry are described and the construction of slip lines in the axisymmetric extrusion of a perfectly plastic rigid medium is given by way of example. The main properties of discontinuity lines in such a case are outlined
[fr]Les travaux anterieurs ont montre comment les problemes de plasticite dans le plan peuvent etre etudies au moyen des lignes de glissement, et eventuellement avec les lignes de courant. En symetrie axiale, la construction des lignes de glissement devient difficile, et l'on a ete finalement amene a effectuer l'etude complete par les lignes de courant. On presente les principales methodes utilisant les lignes de courant en symetrie axiale, et on donne en exemple la construction des lignes de glissement dans le filage en symetrie axiale d'un milieu rigide parfaitement plastique. On rappelle les principales proprietes des lignes de discontinuite dans ce cas
[en] Curvature extrusion process has several advantages in comparison to the conventional extrusion and bending process. In the curvature extrusion, the extruded part is directly bent during extrusion. Therefore, it does not need additional bending process after extrusion. In the curvature extrusion process, it is possible to produce curved extruded products that have a constant or various curvatures. It is essential that we predict the curvatures of the extruded product to meet the required curvatures. This paper proposed a theoretical model that can predict the curvature of extruded product produced by the curvature extrusion process. Using the proposed model the movement of guide tool that causes the bending of extruded product was controlled to produce the required curved automotive Al bumper back beam. The effectiveness of the proposed prediction model and the movement of guide tool were verified by the FE analysis and curved extrusion experiment
[en] An extensive review on extrusion processes is presented. The various applications, parameters and their influence on the process and on the quality of the products, were scanned. Special attention is given to the two main processes, conventional extrusion and hydrostatic extrusion. (author)
[en] The fabrication of seamless tungsten crucibles 127-mm ID x 265-mm high x 6.25-mm wall thickness (5 in. x 10 1/2 in. x 1/4 in.) involved three drawing operations and extrusion spinning. The success of the drawing operations came from a combination of low draw reduction percentage, generous draw radii, large punch-to-die clearance, and attention to drawing temperature. The extrusion spinning success related to good drawn-cup-to-spinning-mandrel fit prior to making the extrusion passes, removal of stress risers in the part prior to spinning, and special attention to part and mandrel temperature
[en] A mathematical procedure for finding the contact points of shaping arcs at the end of a punch is considered. Profiling of the conical upper section of a punch is discussed. A golden-section algorithm is proposed for determining an angle whose value cannot be determined analytically from the initial data.
[en] Hydrostatic extrusion is a drawing method in which a metal billet is forced through a draw-plate by means of a fluid under pressure. This process has the great advantage that friction of the billet on the machinery is completely eliminated, but a number of problems arise when it comes to building an industrial apparatus. One is the tightness problem since the equipment must be able to withstand high pressures, a factor which limits the use of the process. At present the method is chiefly used cold under high pressures: 15 to 20kb. Some attempts are being made to apply it warm or even hot. Various procedures are described in the text attached. Several firms such as Kobe-Steel, A.S.E.A. and Fielding and Platt have designed presses intended exclusively for hydrostatic extrusion. Hydrostatic extrusion has also been carried out hot at the French CEA by adaptation of a system onto a conventional vertical press
[fr]L'extrusion hydrostatique est une methode de filage qui consiste a forcer une billette de metal a travers une filiere a l'aide d'un fluide sous pression. Ce procede presente de nombreux avantages du fait que l'on elimine totalement le frottement de la billette sur les outillages. Cependant, de nombreux problemes se posent quant a la realisation d'appareillages industriels. L'un de ces problemes est l'etancheite, les outillages devant resister a de hautes pressions, d'ou la limite de l'utilisation de ce procede. Actuellement, c'est un procede essentiellement utilise a froid sous de hautes pressions: 15 a 20kb. Quelques tentatives sont faites par son utilisation a tiede ou meme a chaud. Les differentes facons de proceder sont decrites dans le texte ci-joint. Plusieurs industriels tels que Kobe-Steel, A.S.E.A. et Fielding and Platt omt mis au point des presses destinees uniquement au filage hydrostatique. On verra egalement que le C.E.A. a realise l'extrusion hydrostatique a chaud par l'adaptation d'un systeme sur une presse conventionnelle verticale
[en] Highlights: • Cubic structures in PLA were built by an open source 3D printer and dimensionally evaluated; • It was found that dimensional quality is a function of the amount of deposited material; • The slicing software might calculate an amount of material greater than the necessary for parts with high infill density; • Parts with high infill density values can be dimensionally improved with the adjustment of the extrusion multiplier; • Printing speed is a directional parameter, which means its setting must be made by axis (X,Y,Z). Open source projects have helped extrusion-based Additive Manufacturing processes gain popularity in recent years. While they allow the design and development of low cost machines, one of the main difficulties users have found is the parametric calibration. A study was proposed to understand the best practices for the setup of “input parameters”, since in the open software chain there are many available for setup. Through experimental design methods, the dimensional accuracy of a cubic structure was analysed by varying factors such as: slicing software, layer thickness, infill density, first layer, infill and perimeter speeds, as well as extrusion temperature and multiplier. A Prusa I3 Hephestos printer and a Polylactic Acid (PLA) filament were used, and the parts were evaluated with contact measurement, 3D scanning and mass measurement procedures. Statistical analysis showed that the dimensional accuracy of the components was mostly affected by the infill density and the extrusion multiplier. Both parameters highlight the influence of the slicing software on the planning and quality of the models. Instabilities in the amount and flow of material, characterized by excess deposition, were responsible for the distortions along the three fundamental directions of the cubes.
[en] Internal stresses occurring in a stepped rounded D-ring compressed to 20% squeeze and pressurized with internal pressures of 0, 0.98, 1.96, 2.94, 3.92 and 4.9 MPa are analyzed using a photoelastic experimental hybrid method. At a pressure of 0 MPa and 20% squeeze, the photoelastic isochromatic fringes of the stepped rounded D-ring were almost symmetrical. As the internal pressure increased, the isochromatics shifted and curved towards the extrusion gap. By supplying a radius of 0.33 mm at the corners of the stepped D-ring, the high stresses at the sharp corners were reduced by up to 25%. These results further indicate that extrusion of the stepped rounded D-ring occurred at an internal pressure of 4.9 MPa which was about 25% higher than the pressure at which the extrusion of the stepped unrounded D-ring occurred.