Experimental Study on the Evaluation of Necking and Fracture Strains in Sheet Metal Forming Processes

In this paper the formability of AA2024-T3 metal sheets is experimentally analyzed. For this purpose, a series of StretchBending and Incremental Sheet Forming (ISF) tests are carried out. The former tests allow determine the formability limits through the evaluation of necking and fracture using the optical deformation measurement system ARAMIS® and measuring the thickness strains along the fracture line. The latter are performed with the aim of confirming the validity of these limits. In this case, the spifability, formability in Single Point Incremental Forming (SPIF), was studied in the light of circle grid analysis by means of the 3D deformation digital measurement system ARGUS®. Different punch diameters are used in both processes. The results exhibit the importance of the accuracy in the setting of the formability limits as well as the variability that these limits present depending on the forming process or some variables such as the tool radius.Ministerio de Ciencia e Innovación DPI 2009-1333

Recent Approaches for the Determination of Forming Limits by Necking and Fracture in Sheet Metal Forming

Forming limit diagrams (FLD’s) are used to evaluate the workability of metal sheets. FLD’s provide the failure locus at which plastic instability occurs and localized necking develops (commonly designated as the forming limit curve - FLC), and the failure loci at the onset of fracture by tension (FFL) or by in-plane shear (SFFL). The interest of metal formers in controlling localized necking is understandable because the consequence of plastic instability is an undesirable surface blemish in components. However, because under certain loading conditions fracture can precede necking in sheet metal forming processes, there is a growing interest in characterizing the forming limits by necking and fracture in the FLD’s. This paper gathers together a number of recently developed methodologies for detecting the onset of local necking and fracture by in-plane tension or in-plane shear, and discusses their applicability to determine experimentally the FLC’s, FFL’s and SFFL’s.Ministerio de Economía y Competitividad DPI2012-3291

Simplified numerical approach for incremental sheet metal forming process

The current work presents a finite element approach for numerical simulation of the incremental sheet metal forming (ISF) process, called here ‘‘ISF-SAM’’ (for ISF-Simplified Analysis Modelling). The main goal of the study is to develop a simplified FE model sufficiently accurate to simulate the ISF process and quite efficient in terms of CPU time. Some assumptions have been adopted regarding the constitutive strains/stresses equations and the tool/sheet contact conditions. A simplified contact procedure was proposed to predict nodes in contact with the tool and to estimate their imposed displacements. A Discrete Kirchhoff Triangle shell element called DKT12, taking into account membrane and bending effects, has been used to mesh the sheet. An elasto-plastic constitutive model with isotropic hardening behaviour and a static scheme have been adopted to solve the nonlinear equilibrium equations. Satisfactory results have been obtained on two applications and a good correlation has been shown compared to experimental and numerical results, and at the same time a reduction of CPU time more than 60% has been observed. The bending phenomenon studied through the second application and the obtained results show the reliability of the DKT12 element

Energy consumption analysis of robot based SPIF

Part of: Seliger, Günther (Ed.): Innovative solutions : proceedings / 11th Global Conference on Sustainable Manufacturing, Berlin, Germany, 23rd - 25th September, 2013. - Berlin: Universitätsverlag der TU Berlin, 2013. - ISBN 978-3-7983-2609-5 (online). - http://nbn-resolving.de/urn:nbn:de:kobv:83-opus4-40276. - pp. 131–136.Production processes, as used for discrete part manufacturing, are responsible for a substantial part of the environmental impact of products, but are still poorly documented in terms of environmental impact. A thorough analysis of the causes affecting the environmental impact in metal forming processes is mandatory. The present study presents an energy consumption analysis, including a power study of Single Point Incremental Forming (SPIF) processes using a 6-axes robot platform. The present paper aims to investigate whether the fixed energy consumption is predominant or negligible in comparison to the actual forming operation. Power studies are performed in order to understand the contribution of each sub-unit towards the total energy demand. The influence of the most relevant process parameters, as well as the material being processed and the sheet positioning, with respect to the power demand are analysed

Hole-flanging of AA7075-O sheets: Conventional process versus SPIF

Incluída en nº 50 Procedia ManufacturingRecently, the research interest in hole-flanging for small and medium-sized batches has turned from conventional press-working to SPIF due to the advantages of incremental forming, such as flexibility and cost of tools. Both technologies have been studied separately using different approaches and, therefore, most studies cannot be easily compared. The aim of this work is to provide a better understanding of the deformation process and the material formability in hole-flanging by critically comparing both forming processes. To this end, a series of experimental tests by press-working and a SPIF process in a single stage, using forming tools with same profile radii, are analysed. The material is AA7075-O sheet of 1.6-mm thickness. The deformation process is analysed by measuring circumferential and meridional strains along the flange using Digital Image Correlation techniques. The process limits are evaluated by using the traditional Limiting Forming Ratio (LFR), which defines the maximum reachable diameter of the flange related to the initial pre-cut hole performed, as well as two additional parameters based on either the flange height or the average thickness reduction. Results conclude that the LFR is not an appropriate measurement of flangeability in processes other than conventional press-working and that SPIF is the preferred process to perform hole flanges with more flexibility in shapeGobierno de España DPI2015-64047-RGobierno de España PGC2018-095508-B-I00Junta de Andalucía US-126313

Performances Analysis of Titanium Prostheses Manufactured by Superplastic Forming and Incremental Forming

Abstract Titanium and its alloys are widely used in cranioplasty because they are biocompatible with excellent mechanical properties and favor the osseointegration with the bone. However, when Titanium alloys have to be worked several problems occurred from a manufacturing point of view: the standard procedure for obtaining Titanium prostheses is represented by the machining processes, which result time and cost consuming. The aim of this research consist to introduce alternative flexible sheet forming processes, i.e. Super Plastic Forming (SPF) and Single Point Incremental Forming (SPIF), for the manufacturing of patient-oriented titanium prostheses. The research activities have already highlighted the potentiality of the investigated forming processes that can be alternatively used taking into account both the damage morphology and the need of urgency operation. In the present work, the way of manufacturing the Ti prostheses by SPF and SPIF is described. A comparative analysis has been performed, thus highlighting the peculiarities of the investigated processes and the prostheses feasibility