1,721,100 research outputs found
Progetto, sviluppo e validazione di un modulo software per il timing di presse automatiche multistazione integrato in un sistema CAD/CAE per la tecnologia dello stampaggio a freddo
No full textIl presente lavoro verte sulla progettazione, sviluppo e validazione di un modulo CAD/CAE per il timing di presse automatiche multistazione e si inserisce all'interno di un progetto europeo B.R.I.T.E. di più ampio respiro che tocca tutti gli aspetti fondamentali del process planning nella tecnologia della forma tura a freddo.
In esso viene presentata un'analisi delle differenti tipologie di presse presenti nel mercato, accompagnata da un'indagine sulle procedure di tirning e set-up estesa sia ai costruttori che agli utilizzatori di tali presse.
E' stato così possibile definire sia l'architettura funzionale del modulo, sia l'algoritmo per la simulazione dei movimenti, algoritmo che può essere utilizzato per tutte le tipologie di presse che sono state classificate.
Nello sviluppo del modulo come applicazione interattiva all'interno del sistema CAD Euc1id-IS (Matra-Datavìsion) é stata posta particolare attenzione sia alle problematiche di portabilità su altri sistemi CAD, che all'integrazione del modulo di timing con gli altri moduli che costituiscono il sistema CAD/CAE per la tecnologia dello stampaggio a freddo.
La validazione, infine, del software si é focalizzata su aÌcune presse multistazione tra quelle utilizzate dai partners industriali del progetto e che presentavano tipologie di funzionamento e caratteristiche di regolazione assai differenti
Mathematical definition of the 3D strain field of the ring in the radial-axial ring rolling process
No full textReceived 29 March 2016 Received in revised form
4 July 2016
Accepted 7 July 2016 Available online 15 July 2016
Keywords:
Metal forming Ring rolling
Strain analysis Analytic functions FE analysis
1. Introduction
Radial-axial ring rolling (RARR) is widely used in the produc- tion of seamless rings for the automotive and aerospace industries, where a ring work-piece is drawn into the mandrel-main roll gap and the axial rolls gap, causing expansion of the diameter as well as reduction in the thickness and height [1,2].
In the literature, many efforts have been spent in the in- vestigation of the radial-axial ring rolling process considering different points of view, generally aiming to improve the knowl- edge of the interactions among the ring, the tools, the process set up and the production environment. As concerns the process de- sign, Hua et al. [3] defined useful rules for the estimation of the ring stiffness, which is an important factor to avoid collapses or unexpected deformations during the forming process. Zhou et al. [4], utilizing ABAQUS/Explicit solver, studied the influence of the tools dimensions, providing rules to optimize their choice. Zhou et al. [5] also analyzed the influence of the axial rolls motion laws
n Corresponding author.
E-mail address: [email protected] (L. Quagliato).
http://dx.doi.org/10.1016/j.ijmecsci.2016.07.009
0020-7403/& 2016 Elsevier Ltd. All rights reserved.
abstract
The paper focuses on the radial-axial ring rolling process and details a new mathematical approach for the determination of the evolution of the ring geometry during the deformation process, taking into account separately the sequence of incremental deformations occurring when the ring passes through the mandrel-main roll gap and through the axial rolls gap. Based on the determined geometry of the ring, the three strain components of the strain tensor are estimated and the equivalent plastic strain is computed. The proposed approach, taking into account a third strain in each deformation gap, allows an estimation of the equivalent plastic strain, which is a required parameter for the analytical estimation of the flow stress of the material, needed to compute the forming force. Since a direct validation of the strain components is not possible in the industrial RARR process, authors’ models for the determination of geometry and strain, together with preliminary authors’ models for the estimation of strain rate and temperature drop along the process, have been applied to a literature case for the estimation of the radial forming force in order to obtain a validation of the proposed models. Prediction of radial forming force utilizes a literature model based on slip line theory adapted to the ring rolling process. To extend the validation of the approach and to explore the quality of its predictions to other process configurations, different geometry of the ring have been considered and compared with FEM predictions. These com- parisons resulted in good agreement between analytical and FEM results as concerns ring geometry evolution, strain tensor prediction and effective strain estimation
FEM macht geldwerten Nutzen
No full textNicht nur bei Blech und Antriebsstrang ist Massenminderung angezeigt. In jedem Pkw stecken rund 4000 Federn. Das bedeutet Sparpotenzial. FEM-Analysen auf Basis der Software Simufact.Forming 10.0 helfen dabei, die Drahtdurchmesser von Schraubenfedern ohne Verlust an Performance zu optimieren. Die Universität Padua hat’s vorgerechnet
Experimental investigation on the thermo-mechanical fatigue in hot- and warm- forging
No full textIn hot and warm forging processes, widely adopted in the manufacturing industry when complex shape or large components should be obtained in medium-high production runs, coupled thermal and mechanical cycles are the main causes of damage for dies: wear, plastic deformation and TMF cracking are the possible failure mechanisms. Differently from wear and plastic deformation where the damage is gradually incremented during the service life of the dies and their effects can be monitored on the forged components, TMF failure arises suddenly without any previous notice on the forged part. Reduction of the risk of these failures, or an improvement of tool service life, can be obtained by a proper choice of die material, as well as by tuning the forging cycle parameters. To this aim industrial practice and experience can be helpful, but at the moment estimation of tool life can not be achieved neither by experimental technique, nor by simulation software. For the investigation of thermo-mechanical fatigue (TMF) phenomena that arises in dies for hot and warm forging operations a new simulative laboratory test has been developed. The experimental apparatus can apply thermo-mechanical cycles on the material specimen generating thermal gradients in the cross-section and reproducing on a small portion of material conditions not so far from those of industrial die. TMF behaviour of a die steel (DIN X37CrMoV5-1 vacuum remelted) has been investigated on this system considering different working conditions and taking into account the effects of i) maximum temperature cycle, ii) minimum temperature cycle, and iii) eq /Y (T ) ratio (cyclic mechanical load and temperature are varied in phase) on specimen life.
Design of Experiments (DoE) techniques have been used to define the experimental campaign consisting of a screening design followed up with a response surface design. Same experiments have been used to tune and validate a theoretical model proposed by the authors as a generalization of Woehler-Miner law following Chaboche approach
A virtual prototyping environment for a robust design of an injection moulding process
No full texttThis paper proposes a new approach that enables a robust optimisation of the injection moulding pro-cess, based on the integration of numerical simulations, Response Surface Methodology and stochasticsimulations in a type of integrated environment known as a virtual prototyping environment (VPE). Theprincipal aim of the proposed approach is to include in the numerical setup of injection moulding theeffects of fluctuations of process parameters.To clarify the proposed methodology, the paper details its application to the injection moulding processfor the production of an engine cover. The moulded part presents some critical tolerances on differentdimensions because of sealing and assembly requirements and the application of the VPE makes it pos-sible to perform a robust setup taking into account the process fluctuations. The numerical predictionwas confirmed by real production measurements on small pre-production runs performed adopting themoulding window explored in the virtual setup
Thermo-mechanical fatigue life assessment of hot forging die steel
No full textDies for hot forging operations are subjected to coupled mechanical and thermal cycles which deeply influence their thermo-mechanical fatigue life. Crack initiation and propagation on die surface are induced both by thermal gradients acting in the layer near the contact surface with the billet and by the superimposed stresses due to the mechanical cycles.
At present, die life cannot be estimated either by experimental tools, or by simulation software. Therefore, a programme of research has been started in this field. A new laboratory test has been developed that is able to reproduce in specimens the thermo-mechanical conditions derived from industrial cases. A description of the test equipment and the relevant procedure is summarized in the first part of the work. Then, the paper focuses on the experimental investigation of a typical hot forging die steel. Design of Experiments (DoE) techniques were used in designing and analysing the experimental programme. A thermo-mechanical fatigue life assessment model, based on the experimental data and using response surface methodology (RSM), is proposed. Effects on life, due to variation of some forging parameters, are evaluated
Automotive Suspension Springs Cold Formed Using Pre-Hardened Wire_Part 2 Numerical Modelling of the Coiling Process
No full textWeight reduction of automotive components includes the coil springs used in car suspensions. Spring wire diameter can be reduced, but it is necessary to use high-strength spring material to maintain required mechanical properties. In Part 1 of this article, the authors look at the technology used in the mass production of suspension springs including the forming processes involved in the use of high-strength materials to lower the weight of these automotive components. In Part 2, the authors will explore numerical modelling of the coiling process relative to material properties and spring diameter size
Automotive Suspension Springs Cold Formed Using Pre-Hardened Wire_Part 1 The Industrial Case
No full textWeight reduction of automotive components includes the coil springs used in car suspensions. Spring wire diameter can be reduced, but it is necessary to use high-strength spring material to maintain required mechanical properties. In Part 1 of this article, the authors look at the technology used in the mass production of suspension springs including the forming processes involved in the use of high-strength materials to lower the weight of these automotive components. In Part 2, the authors will explore numerical modelling of the coiling process relative to material properties and spring diameter size
Design of a flanged ring produced by hot forming using FE analysis
No full textThis paper describes the investigation for a ring rolling company aimed at designing, by means of FE analysis, the manufacturing steps involved in the production of a flanged ring, made of 42CrMo4 steel, used for power generation plants. Company engineers proposed the following hot forming cycle consisting in (i) upsetting, (ii) indenting, (iii) piercing and, (iv) ring rolling. The FE analysis conducted adopting the proposed design evidenced different problems (confirmed by a pre-production test operated at the company job shop) both in the forming of the initial ring and in the ring rolling process. The hot forming of the pierced perform exceeds the capacity of the presses available at the job shop. Therefore this part of the forming cycle was redesigned modifying the tooling, reducing the press stroke and adding a new upsetting stage with a flat die at the end of the hot piercing. Moreover the lack of material in the flanged part of the final ring and the excessive axial expansion of the ring suggested to reduce the height of the preform and to increase the diameter of the flanged zone.
The new configuration of the perform sequence and main roller shape were successful in correcting both the axial expansion and the filling of the flanged zone, also keeping the required forming forces below the industrial limits
Micro wire drawing: effect of lubricant and analysis of the mechanical properties of steel and copper wires
No full textRecently, fine wires on the order of 300 to 100 μm in diameter have become popular for mechanical and electrical -applications such as micro springs, micro pins, printer mesh,cutting wire for Electrical Discharge Machining (EDM) and wire for cutting silicon, quartz and other semiconductor materials. The wires are produced by cold micro wire drawing. Recent studies1 have demonstrated that at micro scale the so called “size effect” determines differences in the production processes when passing from the macro to the micro scale. In particular, it has been found that the main differences are related to the material behavior and the friction. As concerns friction, it has been found2 that friction can increase by a factor above 20 and that the conventionally used friction laws cannot incorporate the size effect. Instead, the general Wanheim/Bay friction law can be used to describe friction at micro scale. The material behavior changes with miniaturization, caused by size effects that occur when a process is scaled down from conventional size to micro scale. Scaling down the dimensions of the part as in microforming, the ratio of the grains on the surface layer with the internal grains increases, and according to metal physics theory, stress hardening is reduced. For this reason, when microspecimens are tested in compression or in tension, the increased contribution of external grains to the integral flow stress causes a reduction of the strength of the material as explained by the surface layer model. When the external surface of microparts is not free during deformation, but interacts with the tooling system (as in mirco wire drawing), some experimentations show that the material presents an increased flow stress localized in few tens of microns at the external surface of the part3, which can not be detected by the tensile or compression test. This investigation, after an introduction on the experimental apparatus and the procedure, focuses on the cold drawing of low-carbon steel and commercially pure copper, where the wire diameter is reduced from 300 to 269 μm. Different lubrication conditions have been tested and relevant drawing forces have been monitored. The tensile strength of the drawn wire and the hardness distribution in the cross section has been measured. The drawn wires have been electro-chemically polished to remove their external layer and the resulting wire (the reduced one) has also been subjected to the tensile test. From the comparison between the strength of the drawn wire and that of the reduced wire, the strength of the external layer has been estimated. Finally, a grain size analysis in the cross section of the undeformed and drawn wire has been performed. Differences in strengthening of these materials have been evidenced as well as in the final grain distribution observed in the drawn wires
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