@article{ 11589_62888, author = { Palumbo Gianfranco and Piglionico Vito and Piccininni Antonio and Guglielmi Pasquale and Tricarico Luigi }, title = {Evaluation of the optimal working conditions for the warm sheet HydroForming taking into account the yielding condition}, year = {2016}, journal = {MATERIALS & DESIGN}, volume = {91}, abstract = {The present work aims at determining the optimal working conditions to manufacture an aluminium component by warm sheet HydroForming. The following parameters were considered: temperature, blank holder force, oil pressure; while, as output variables, die filling and maximum oil pressure. The optimization procedure was preliminary based on numerical data. A finite element model was created and great attention was paid to the material modelling: an extensive characterization for evaluating the mechanical and deformative behaviour at different temperatures was conducted; in addition, the effect of modelling different plastic behaviours was considered through the implementation of two yield criteria (the anisotropic Barlat '89 criterion and the isotropic Von Mises one). Results from the optimization procedure indicated the room temperature as the optimal working condition when implementing the Barlat '89 criterion, while the optimal temperature was higher (about 110. °C) when considering the isotropic formulation. It is relevant that, irrespective to the yield criterion, the tuning of both the numerical models was possible, but HydroForming tests confirmed the validity only of the anisotropic criterion. In fact, results from the optimization procedure based on experimental data indicated the room temperature as the optimal condition, highlighting the key role played by the yield criterion in the process modelling.}, keywords = {Al 6xxx series; FEM; Multi-objective optimization; Warm HydroForming; Yield criterion; Mechanical Engineering; Mechanics of Materials; Materials Science (all)}, doi = {10.1016/j.matdes.2015.11.113}, pages = {411--423} } @conference{ 11589_62887, author = { Sorgente Donato and Piccininni Antonio and Piglionico Vito and Guglielmi Pasquale and Grossi Dario and Palumbo Gianfranco and Tricarico Luigi }, title = {Characterization of a superplastic titanium alloy with an experimental and numerical approach based on free-inflation tests}, year = {2016}, publisher = {Trans Tech Publications Ltd}, journal = {MATERIALS SCIENCE FORUM}, volume = {838-839}, booktitle = {Materials Science Forum}, keywords = {Characterization; Inverse analysis; Pressure jump test; Superplasticity; Titanium alloy; Materials Science (all); Condensed Matter Physics; Mechanical Engineering; Mechanics of Materials}, url = {http://www.ttp.net/0255-5476.html}, doi = {10.4028/www.scientific.net/MSF.838-839.177}, pages = {177--182} } @conference{ 11589_62889, author = { Sorgente Donato and Palumbo Gianfranco and Scintilla Leonardo Daniele and Brivio Riccardo and Carozzi Gabriele and Tricarico Luigi }, title = {Superplastic forming of a complex shape automotive component with optimized heated tools}, year = {2016}, publisher = {Trans Tech Publications Ltd}, journal = {MATERIALS SCIENCE FORUM}, volume = {838-839}, booktitle = {Materials Science Forum}, keywords = {Aluminium alloy; Heated forming tools; Superplastic forming; Materials Science (all); Condensed Matter Physics; Mechanical Engineering; Mechanics of Materials}, url = {http://www.ttp.net/0255-5476.html}, doi = {10.4028/www.scientific.net/MSF.838-839.494}, pages = {494--499} } @article{ 11589_62890, author = { Sorgente D and Palumbo G and Scintilla L D and Tricarico L }, title = {Gas forming of an AZ31 magnesium alloy at elevated strain rates}, year = {2016}, journal = {INTERNATIONAL JOURNAL, ADVANCED MANUFACTURING TECHNOLOGY}, volume = {83}, abstract = {In this work, the gas forming of AZ31 magnesium alloy 0.75-mm-thick sheets at elevated strain rates (fast gas forming) is investigated through an experimental-numerical approach. First, free inflation tests were carried out to find the conditions, in terms of temperature and forming pressure, able to give the best compromise between the alloy formability and the forming time. The analysis was successively moved to a closed die forming application with a stepped geometry case study in order to analyse the real forming process. Both an axisymmetric model of the free inflation test and a 3D model of the closed die forming process were built to correlate the results from free inflation tests (in terms of optimal strain rate values) to the closed die forming test: Numerical simulations were run to find the pressure value to be applied in gas forming tests. Experimental gas forming trials were finally conducted in order to support the approach and to analyse post-forming characteristics of the formed parts. Results showed that very small fillet radii can be reached on a commercial Mg alloy sheet setting very short forming times (few seconds). The choice of the forming temperature and of the corresponding optimal strain rate strongly affects the grain growth and the cavitation phenomena. Even if the alloy is prone to a strong static and dynamic grain growth at elevated temperatures, a small mean grain size value can be reached in the formed component due to the short forming times.}, keywords = {FE model; Gas forming; Magnesium alloy; Superplastic forming; Industrial and Manufacturing Engineering; Control and Systems Engineering; Computer Science Applications1707 Computer Vision and Pattern Recognition; Software; Mechanical Engineering}, url = {http://www.springerlink.com/content/0268-3768}, doi = {10.1007/s00170-015-7614-0}, pages = {861--872} } @article{ 11589_62893, author = { Palumbo Gianfranco and Piglionico Vito and Sorgente Donato and Piccininni Antonio and Guglielmi Pasquale and Tricarico Luigi }, title = {Correlating shrinkage microporosity with the mechanical properties of sand-cast superduplex stainless steel using a numerical/experimental approach}, year = {2016}, journal = {MATERIALS & DESIGN}, volume = {93}, abstract = {In this work, the Niyama criterion for the prediction of shrinkage microporosity in a superduplex stainless steel (ASTM A890 Gr. 5A) end-risered plate produced by sand-casting is adopted. To validate numerical results obtained using the commercial software MAGMASoft, experimental castings were produced, and both the shrinkage microporosity and its effect on the material behaviour was evaluated. Metallographic techniques were used to quantify the microporosity and evaluate its distribution; the effect of the shrinkage microporosity on the sand cast material was measured through tensile tests on miniaturised specimens extracted along the longitudinal direction of the plate.Image analyses allowed estimation of the threshold Niyama value for microporosity in the investigated material. An analogous threshold for the Niyama parameter was determined from the mechanical data arising from tensile tests in which specific microporosity levels (and Niyama values) were identified that corresponded to minimum required levels of yield stress, UTS and elongation after fracture as specified by the ASTM standard. Mechanical data were found to be well correlated to the Niyama value, thus allowing to effectively use the purely thermal parameter Niyama to predict the sand cast material behaviour.}, keywords = {MAGMASoft; Miniaturised tensile specimens; Niyama criterion; Sand-casting; Shrinkage microporosity; Superduplex stainless steel (ASTM A890 Gr.5A); Mechanical Engineering; Mechanics of Materials; Materials Science (all)}, doi = {10.1016/j.matdes.2015.12.088}, pages = {168--179} } @conference{ 11589_62896, author = { Piglionico Vito and Piccininni Antonio and Palumbo Gianfranco and Tricarico Luigi }, title = {Multi-objective optimization of the hydroforming process considering different plastic yield criteria}, year = {2015}, publisher = {Trans Tech Publications Ltd}, journal = {KEY ENGINEERING MATERIALS}, volume = {651-653}, booktitle = {Key Engineering Materials}, abstract = {The present work aims at determining the optimal working conditions for the manufacturing of the AA6061-T6 Al alloy by the hydroforming process. As case study a stepped geometry was used. A numerical model was created using the commercial explicit Finite Element code LS-DYNA. The plastic behaviour of the investigated alloy was modelled implementing experimental data (flow stress curves, Lankford coefficients and Forming Limit Curves) and using two different yield criteria: an anisotropic one (Barlat '89) and the conventional isotropic one (Von Mises). Finite Element models were tuned using experimental data from warm hydroforming tests: comparing both the sheet thinning and the die cavity filling, quite different friction conditions had to be supposed for obtaining a good fitting with both the yield criteria. Finite Element models were finally used for evaluating the working range of the hydroforming process: results from a Central Composite Design simulation plan were imported within an integration platform (modeFRONTIER) to evaluate the optimal hydroforming conditions based on a multi-objective genetic algorithm optimization. Even if both numerical models (implementing different yield criteria) were tuned using experimental data, quite different results were obtained from the optimization procedure: the adoption of the anisotropic criterion was thus proved to be the suitable choice for better catching the material behaviour, as also confirmed by experimental hydroforming tests aimed at verifying the robustness of numerical data.}, keywords = {Aluminum alloy; FE model; Formability; Hydroforming; Optimization; Yield criteria; Materials Science (all); Mechanics of Materials; Mechanical Engineering}, url = {http://www.scientific.net/}, doi = {10.4028/www.scientific.net/KEM.651-653.1394}, pages = {1394--1399} } @article{ 11589_62895, author = { Antonio Piccininni and Di Michele Gabriella and Palumbo Gianfranco and Sorgente Donato and Tricarico Luigi }, title = {Improving the Hydromechanical Deep-Drawing Process Using Aluminum Tailored Heat Treated Blanks}, year = {2015}, journal = {ACTA METALLURGICA SINICA}, volume = {28}, abstract = {The present work demonstrates the effectiveness of combining the hydromechanical deep-drawing process with the Tailored Heat Treated Blank (THTB) technique. In the hydromechanical deep-drawing process, the fluid pressure is used for postponing the fracture occurrence in the blank, while the THTB technique allows to create a material property gradient through a suitable artificial aging treatment carried out prior to the forming process. Since the number of process variables is large, in the present work the authors propose an optimization loop for the determination of the parameters controlling the extension of the blank regions to be subjected to the aging treatment and the temperature levels to be set during the heat treatment. The proposed methodology couples a simple finite element model (Abaqus) with a multi-objective optimization platform (modeFRONTIER). A preliminary experimental campaign was carried out for determining the effect of the aging treatment on the mechanical (through tensile tests) and deformative (through formability tests) behavior of the AC170PX aluminum alloy. Optimization results prove the effectiveness of the adopted methodology and put in evidence that the adoption of properly aged blanks in the hydromechanical deep drawing allows to increase the limit drawing ratio and to simplify the process since it is conducted at room temperature.}, keywords = {Aluminum alloy – Aging – Hydromechanical deep drawing – Finite element analysis – Mechanical characterization – Formability}, url = {http://dx.doi.org/10.1007/s40195-015-0347-0}, doi = {10.1007/s40195-015-0347-0}, pages = {1482--1489} } @inbook{ 11589_13035, author = { Palumbo G and Piccininni A and Guglielmi P and Sorgente D and Scintilla LD and Tricarico L }, title = {Application of the warm hydroforming process to the manufacturing of pre-aged 6xxx series components using a numerical/experimental approach}, year = {2014}, journal = {KEY ENGINEERING MATERIALS}, volume = {622-623}, booktitle = {15th International Conference on Metal Forming 2014; Palermo; Italy; 21 September 2014 through 24 September 2014}, abstract = {In this work the Warm Hydroforming (WHF) process for the production of a 6xxx series Al alloy component has been investigated using a numerical/experimental approach: both experimental and numerical hydroforming tests were carried out using the alloy AC170PX, a pre aged (T4 condition) Al alloy often adopted for automotive applications. In order to evaluate both the mechanical and strain behaviour of the material, tensile tests were carried out at different temperature and strain rate levels using the Gleeble system 3180, keeping also into account the ageing effect; in addition, formability (Nakazima) tests in warm conditions were performed by means of a specific equipment and the Forming Limit Curves at different temperature levels were evaluated according to the ISO standard 12004-2. Hydroforming experiments were carried out using a prototypal press machine specifically designed for WHF and SuperPlastic Forming tests. Such tests, scheduled by a DoE approach, were aimed at investigating the suitability of using the investigated Al alloy in the WHF process: attention was thus focused on those parameters mainly affecting the aging phenomenon (temperature, heating time and cycle time). In order to overcome the actual physical limitation of the hydroforming facilities, a Finite Element (FE) model of the WHF process was also created implementing experimental data (flow stress curves and FLCs) and tuned using data from preliminary WHF tests. In particular, after setting the Coefficient Of Friction (COF) according to temperature and verifying the robustness of numerical simulations, the FE model was used for investigating: (i) the influence of the Blank Holder Force (neglected in the experimental campaign); (ii) the adoption of quite smaller values of the parameter cycle time (being the aim to determine higher strain rates in the material). Through the definition of proper response variables (Flatness, Bursting Pressure and Thickness Ratio) both experimental and numerical results were analyzed by means of polynomial Response Surfaces in order to evaluate the optimal process conditions.}, keywords = {Warm HydroForming, Finite Element, A6xxx-T4, ageing, automotive, formability}, doi = {10.4028/www.scientific.net/KEM.622-623.701}, pages = {701--708} } @article{ 11589_1777, author = { M BRANDIZZI and S RENNA and A SATRIANO and D SORGENTE and TRICARICO L }, title = {Nd:YAG laser welding of fine sheet metal butt joints in AZ31 magnesium alloy}, year = {2014}, journal = {WELDING INTERNATIONAL}, volume = {28}, abstract = {Magnesium alloys have been used increasingly in various areas of industry, such as the automotive sector, electronic components. A reliable method for joining components produced with these materials will definitely allow for a wider use of these alloys. In this article, the laser welding process with an Nd:YAG laser using a maximum power of 2 kW was studied and reported. The effect of welding parameters, such as laser and welding, was analysed. Metal sheets of 1mm thickness in AZ31B magnesium alloy were butt-welded with helium and argon as shielding gas in the absence of filler material. The mechanical characteristics were measured during tensile tests, using digital image correlation (DIC) as a deformation measurement technique. After a preliminary experimental plan aimed at exploring the range of process parameters, the welding process was optimized using an approach based on the design of experiments (DoE). Consecutive experimental plans led to optimized butt joints, which, following a tensile test, showed a sound weld bead with fracturing in the base material. Local strain analysis by DIC highlighted different tensile behaviours, in terms of deformation of the weld bead, in the optimized butt joints with respect to those that were not optimized.}, keywords = {laser welding; magnesium alloys; process conditions optimization}, doi = {10.1080/09507116.2012.753266}, pages = {789--798} } @conference{ 11589_16472, author = { G Palumbo and P Guglielmi and A Piccininni and V Piglionico and Sorgente D and L D Scintilla and L Tricarico }, title = {EVALUATION OF THE CREEP BEHAVIOUR OF A SUPER DUPLEX STAINLESS STEEL FOR OIL AND GAS APPLICATIONS}, year = {2014}, booktitle = {ECCC2014 3rd International ECCC Conference}, abstract = {The present work is aimed to determine the mechanical behaviour in hot condition (range 600-1200°C) of a super duplex stainless steel (SAF 2507) for applications in the Oil&Gas field (highly corrosive environments). A wide experimental activity (both tensile and creep tests) was carried out using the Gleeble system, using experimental settings able to make the test robust and replicable. In order to evaluate the constant parameters able to model the material behaviour according to the Norton equation, experimental conditions (in terms of temperature and applied stress) were designed: the Response Surface Methodology (RSM) and a subsequent double multi objective optimization were implemented within an integration platform. Finally, using Visual Basic routines model constants were evaluated and/or refined, thus being able to optimally fit real strain –time curves, also in the primary creep stage.} } @conference{ 11589_22341, author = { G Palumbo and A Piccininni and V Piglionico and P Guglielmi and Sorgente D and L Tricarico }, title = {Investigation about the warm deep drawing of Mg alloys using metamodels}, year = {2014}, booktitle = {International User Meeting modeFRONTIER, Trieste 2014}, abstract = {The present work is focused on the Deep Drawing process in warm conditions and in particular on the evaluation of optimal working conditions and/or enhancement of the process limits using metamodels. Experimental tests were carried out with the aim of investigating the effect of the most important process parameters affecting the DD process: the blank holder pressure, the temperature of the Blank holder and the punch speed. The output variable “Progress” (defined as the ratio between the effective and the maximum punch stroke) was fitted using a separate parallel approach based on two different Response Surface construction algorithms. Further experimental tests were thus designed using an optimization approach based on the above mentioned RS, being the aim to enhance the process limits in terms of maximum achievable drawing ratio. The experimental results coming from the second campaign could be also used as a validation set for the results obtained from the initial optimization, thus allowing to identify which of the two initial RS was the most reliable in evaluating the process window.} } @article{ 11589_5783, author = { Sorgente D and Colonna P and Carbonara A and Palumbo G and Corizzo O and Scintilla L D and Carozzi G and Tricarico L }, title = {FORMATURA SUPERPLASTICA DI UN COMPONENTE AUTOMOBILISTICO IN LEGA DI ALLUMINIO TRAMITE UN APPROCCIO NUMERICO-SPERIMENTALE}, year = {2014}, journal = {LAMIERA}, volume = {9}, pages = {52--54} } @article{ 11589_6959, author = { Sorgente D and Corizzo O and Brandizzi M and Tricarico L }, title = {Preliminary Study on the Formability of a Laser-Welded Superplastic Aluminum Alloy}, year = {2014}, journal = {JOURNAL OF MATERIALS ENGINEERING AND PERFORMANCE}, abstract = {In this work, the effect of the laser-material interaction on the formability of a superplastic aluminum alloy was investigated. In applications such as Tailor-Welded Blanks and in the manufacturing of very large components with a complex shape, laser welding combined with superplastic forming may be a very fitting industrial tool. Bead on plate tests were carried out in order to simulate the laser-welding process and then, free inflation tests were performed to evaluate the compatibility of these two processing techniques. The Al-Mg alloy used in this work has a very small grain size which ensures the superplastic behavior. With the aim of preserving this peculiarity, the following aspects on the formability were investigated: (i) the surface condition of the bead before the forming test (with and without the removal of the excess of metal); (ii) the effect of the travel speed of the laser source on the mean grain size; (iii) the introduction of a refiner, commonly used in aluminum casts, in the molten pool in order to further reduce the mean grain size.}, keywords = {aluminum alloys, grain refinement, laser, superplasticity, welding}, url = {http://link.springer.com/article/10.1007%2Fs11665-014-1206-2}, doi = {10.1007/s11665-014-1206-2}, } @article{ 11589_6748, author = { SORGENTE D and TRICARICO L }, title = {Pressure Profile Designing in Superplastic Forming Based on the Strain Rate and on Post-forming Properties}, year = {2014}, journal = {JOURNAL OF MATERIALS ENGINEERING AND PERFORMANCE}, volume = {23}, abstract = {In this work, the feasibility of reducing the cycle time in superplastic forming through a selective approach in the algorithm that calculates the forming pressure profile was investigated. First, a 3D numerical model of the blow forming process is created. Then, the blank was partitioned in different characteristic areas according to their strain and strain rate histories. Thus, different pressure profiles were numerically calculated choosing different combinations of those partitions of the blank. Experimental trials were finally carried out in order to explore the potential reduction of the forming time that can be achieved through the described approach without affecting the post-forming properties of the formed specimens. Post-forming properties were measured in terms of thickness distribution, mean grain size, and cavitation effects along the formed sheet. In particular, experiments were performed both with the conventional approach (with the whole sheet being monitored) and considering only the area of the sheet that experiences the highest strain values at the end of the forming process. Results highlighted that this latter approach can efficiently reduce the cycle time.}, keywords = {aluminum alloy cavitation pressure profile superplastic forming}, url = {http://link.springer.com/article/10.1007%2Fs11665-014-1027-3}, doi = {10.1007/s11665-014-1027-3}, pages = {2025--2033} } @conference{ 11589_20510, author = { Sorgente and D and Corizzo O and Ancona A and Scintilla LD and Palumbo G and Tricarico L }, title = {Laser hardening of a AISI 52100 bearing steel with a discrete fiber laser spot}, year = {2014}, volume = {8963}, booktitle = {Proceedings of SPIE - The International Society for Optical Engineering}, abstract = {Surface hardening with discrete laser spot treatment is an interesting solution since the adoption of a single pulse allows the treatment of different surface geometries avoiding the effect of back tempering. The aim of this work is to find a suitable process window in which operate to get best results in terms of hardness, diameter and depth of the treated region. A single pulse out of a fiber laser source impinging on a bearing hypereutectoid steel was used using different power values, pulse energy and defocussing distances, in order to get the optimal process parameters. The dimensions of the hardened zone and its hardness were then acquired and related to the laser process parameters, to the prior microstructure of the steel (spheroidized and tempered after oil quenching) and to the roughness on the specimen before the laser treatment. Experimental results highlighted that both the surface condition (in terms of roughness) and the initial steel microstructure have a great influence on the achieved hardness values and on the dimension of the laser hardened layer. The pulse energy and power strongly affected the dimension of the hardened layer, too.}, keywords = {AISI52100; bearing steel; discrete spot; laser hardening} } @conference{ 11589_22743, author = { Sorgente D and Corizzo O and Ancona A and Scintilla L D and Palumbo G and Tricarico L }, title = {Laser hardening of AISI 52100 bearing steel with a discrete fiber laser spot}, year = {2014}, journal = {PROCEEDINGS OF SPIE, THE INTERNATIONAL SOCIETY FOR OPTICAL ENGINEERING}, booktitle = {Proc. SPIE 8963, High-Power Laser Materials Processing: Lasers, Beam Delivery, Diagnostics, and Applications III, 896308 (20 February 2014)}, abstract = {Surface hardening with discrete laser spot treatment is an interesting solution since the adoption of a single pulse allows the treatment of different surface geometries avoiding the effect of back tempering. The aim of this work is to find a suitable process window in which operate to get best results in terms of hardness, diameter and depth of the treated region. A single pulse out of a fiber laser source impinging on a bearing hypereutectoid steel was used using different power values, pulse energy and defocussing distances, in order to get the optimal process parameters. The dimensions of the hardened zone and its hardness were then acquired and related to the laser process parameters, to the prior microstructure of the steel (spheroidized and tempered after oil quenching) and to the roughness on the specimen before the laser treatment. Experimental results highlighted that both the surface condition (in terms of roughness) and the initial steel microstructure have a great influence on the achieved hardness values and on the dimension of the laser hardened layer. The pulse energy and power strongly affected the dimension of the hardened layer, too.}, keywords = {laser, fiber, surface, transformation, hardening, discrete spot, AISI52100, bearing steel}, doi = {10.1117/12.2042083}, } @conference{ 11589_20249, author = { Ancona F and De finis R and Galietti U and Guglielmi P and Palumbo D and Palumbo G and Piccininni A and Piglionico V and Sorgente D and Spina R and Tricarico L }, title = {Development of advanced materials and innovative technologies for the manufacturing of turbo machines to be used in very hard working conditions: Characterization of stainless steels for Oil &Gas applications.}, year = {2014}, booktitle = {Proceeding of SCORE@POLIBA Workshop} } @article{ 11589_5784, author = { SORGENTE D and ANCONA A and TRICARICO L }, title = {Modellazione del trattamento termico mediante laser pulsato ad alta brillanza per la strutturazione superficiale di un acciaio ipereutettoidico}, year = {2014}, journal = {APPLICAZIONI LASER}, volume = {NOVEMBRE-DICEMBRE}, abstract = {Il lavoro analizza gli effetti di un singolo impulso laser di una sorgente in fibra, eseguito nel regime di parametri laser tale da permettere l’indurimento e la rifusione della superficie di un acciaio ipereutettoidico. I parametri laser investigati sono stati la potenza laser, l’energia dell’impulso e la distanza di focalizzazione, il cui effetto è stato determinato valutando la forma, l’ampiezza e la durezza della zona trattata. È stato formulato un modello agli elementi finiti del trattamento termico, calibrato con prove sperimentali, che ha permesso di definire i parametri di processo che garantiscono l’indurimento senza fusione, o la fusione del substrato senza l’insorgere di cricche. Questi risultati sono utili per progettare pattern per la strutturazione via laser di superfici in acciaio.}, url = {http://www.publiteconline.it/applicazioni-laser/index.php?option=com_k2&view=item&id=1108:modellazione-del-trattamento-termico-mediante-laser-pulsato-ad-alta-brillanza-per-la-strutturazione-superficiale-di-un-acciaio-ipereutettoidico&Itemid=123}, pages = {40--47} } @article{ 11589_8042, author = { Sorgente D and Carbonara A and Colonna P and Palumbo G and Spina R and Brivio R and Tricarico L }, title = {Simulazione numerica del processo di formatura superplastica di un componente complesso}, year = {2014}, journal = {LAMIERA}, volume = {6}, abstract = {AFFRONTIAMO LA CARATTERIZZAZIONE DI UN LEGA DI ALLUMINIO FINALIZZATA ALLA CREAZIONE DI UN MODELLO NUMERICO DI UN PROCESSO DI FORMATURA SUPERPLASTICA. L’INDIVIDUAZIONE DEI PARAMETRI DEFORMATIVI OTTIMALI E DELL’EQUAZIONE COSTITUTIVA DEL MATERIALE HANNO PERMESSO DI ANALIZZARE LE CRITICITÀ DI PROCESSO NELLA REALIZZAZIONE DI UN COMPONENTE DI FORMA COMPLESSA NON REALIZZABILE CON TECNICHE CONVENZIONALI.}, pages = {48--51} } @article{ 11589_5732, author = { Palumbo G and Piccininni A and Piglionico V and Guglielmi P and Sorgente D and Tricarico L }, title = {Modelling residual stresses in sand-cast superduplex stainless steel}, year = {2014}, journal = {JOURNAL OF MATERIALS PROCESSING TECHNOLOGY}, volume = {217}, abstract = {A numerical/experimental procedure is proposed for calculating the residual stress state during the cooling phase of the casting process of a superduplex stainless steel (ASTM A890 Gr. 5A). The experimental activity consisted of casting, tensile and creep tests. Casting tests were used to set (by acquiring temperature data at different points) and validate (by measuring displacements after releasing residual stresses by cutting) the Finite Element model. Tensile and creep tests were used to determine the material properties from room temperature to 1200 °C. A fully coupled thermo-mechanical analysis was conducted by neglecting the presence of the sand mould; instead, attention was focused on the material by modelling the creep behaviour using the Bailey-Norton formulation. Measurements of the of the displacements due to the stress release after EDM wire cuts revealed to be in good agreement with the numerical model and confirmed the key role played by viscosity during the cooling phase. Neglecting the viscous strain led to an overestimation (more than twofold) of the stress level in the cast part after the cooling phase in the sand mould. The good matching between experimental and numerical data indicated that a numerical model that incorporates the creep behaviour is able to accurately capture the investigated phenomenon, despite the simplification in the modelling of the casting process (sand mould replaced with virtual convection) which does not substantially affect its accuracy. The robustness of the methodology, which is characterized by small computational cost and good quality of results, was further proved simulating and comparing numerical and experimental results concerning a second casting geometry.}, keywords = {Casting; Creep modelling; Finite element method; Residual stresses; Superduplex stainless steel}, doi = {10.1016/j.jmatprotec.2014.11.006}, pages = {253--261} }