https://popups.uliege.be/esaform21/index.php?id=3348 Publications of Auteurs Andrea Ghiotti fr 0 https://popups.uliege.be/esaform21/index.php?id=3788 Flowforming is an advanced forming technique to produce net shape axisymmetric components, with high dimensional accuracy, based on the simultaneous action of a rotating mandrel and multiple translational rollers. The deformation mechanism has great influence on the uniformity of microstructure, with a gradient in the grain size from the inner to the outer portion of the component cross section, with elongated grains in the rollers feed direction. The highly directional deformation of the microstructure, both along the radial and axial direction, may reach extreme values in the case of large reduction and this aspect may introduce significant uncertainties in the evaluation of the mechanical properties of the final parts (i.e. microhardness, maximum elongation, yield strength) due to the computational methodologies used to estimate the average grain size. The paper focuses on the most frequently used measurement methods to assess the measurement accuracy for the correlation with the local variations of mechanical properties. The reference case for the investigations is the flowforming of AA6082 tubes, processed at different process parameters to change the shape of the grain and the gradient along the radius. Comparisons were carried out with regards to methods that allow measuring the grain size using zero-dimensional features (points), one-dimensional features (lines), and two-dimensional features (areas), respectively with the triple-point count method, the Heyn intercept method and the Jeffries planimetric method. Mon, 29 Mar 2021 14:32:44 +0200 Mon, 12 Apr 2021 11:28:13 +0200 https://popups.uliege.be/esaform21/index.php?id=3788 https://popups.uliege.be/esaform21/index.php?id=3749 In recent years, polymeric materials are being used at an increasing rate in the biomedical industry. In particular, Ultra-High-Molecular Weight Polyethylene (UHMWPE), a thermoplastic polymer characterized by high toughness, good chemical stability and self-lubricating properties, is an ideal candidate for the manufacture of bearing implants used in hip or knee replacements. Nevertheless, it is difficult to achieve a good level of surface finish when turning it, because of its high instability at increasing temperature. In the present study, cryogenic machining was applied instead of dry cutting to machine a biomedical grade UHMWPE at different cutting speeds. The surface finish was assessed in terms of surface roughness, crystallinity degree and hardness in correspondence of the surface. To correlate machinability results with the UHMWPE mechanical behaviour, uniaxial tensile tests were performed in a wide range of temperatures. The obtained results showed that the application of cryogenic machining was an efficient mean to increase the surface finish: in fact, smoother and harder surfaces were obtained regardless of the adopted cutting parameters. Mon, 29 Mar 2021 14:24:30 +0200 Mon, 12 Apr 2021 11:27:39 +0200 https://popups.uliege.be/esaform21/index.php?id=3749 https://popups.uliege.be/esaform21/index.php?id=2151 Auxiliary systems for sheet forming processes are widely used to improve products accuracy and increase tools life. As example, in blanking hydraulic dampers are widely used to reduce shocks and vibrations; nitrogen springs are often integrated in deep drawing tools to correct the ram tilt or to locally increase the blank-holder force, obtaining geometrical features on the stamped blank with one press pass. In this paper, a Magneto-Rheological (MR) semi-active actuator is developed for sheet forming operations and the interaction between MR fluid and electromagnetic field is investigated by Finite Element (FE) analysis. To overcome the limitations of gas springs and hydraulic actuator, the static electromagnetic circuits is reconfigured with respect of conventional MR actuators known in the state-of-the-art. The novel MR actuator has an inner bore where the electric windings are placed, while the narrow gap, in which the active MR fluid flows, is obtained between the inner bore and the cylinder internal surface. The resulting magnetic fields H and induction fields B, as well as the selection of components materials, are studied through the magneto-static FE model. The results from FE simulations show a longer activation length along the gap resulting in higher controllable forces values, without increasing the overall dimensions of the proposed prototype. Tue, 23 Mar 2021 13:27:28 +0100 Mon, 03 May 2021 11:12:09 +0200 https://popups.uliege.be/esaform21/index.php?id=2151