Special Issue "Formability of Materials"

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Manufacturing Processes and Systems".

Deadline for manuscript submissions: 31 July 2020.

Special Issue Editor

Assoc. Prof. Maria Beatriz Silva
Website
Guest Editor
IDMEC, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal
Interests: formability; sheet metal forming; tube forming; incremental sheet forming
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

In the last decades, the trend in the manufacturing industry has led to the production of products with better properties, of lighter weight, with less waste, that are more profitable and more sustainable. These challenges have caused a need to develop new and/or improve the existing manufacturing processes applied to new materials. To achieve this, the knowledge of the limits of the formability of materials will determine the success of industrial processes.

Formability limits are a measure of the plastic deformation that a material can reach without failure. Depending on the raw material, and whether it is bulk or sheet, failure is triggered by different modes. These limits can be determined by means of experimental tests, and in recent years, due to techological advances, new methodologies have been developed to obtain them more accurately.

It is my pleasure to invite you to submit a manuscript or review to this Special Issue on the definition of the field formability limits of metallic or polymeric materials.

Assoc. Prof. Maria Beatriz Silva
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • formability limits
  • sheet
  • bulk
  • experimentation
  • metal
  • polymer

Published Papers (4 papers)

Order results
Result details
Select all
Export citation of selected articles as:

Research

Open AccessArticle
Design and Optimization of the Local Laser Treatment to Improve the Formability of Age Hardenable Aluminium Alloys
Materials 2020, 13(7), 1576; https://doi.org/10.3390/ma13071576 - 29 Mar 2020
Abstract
The research of innovative methodologies to improve the Aluminium alloys formability at room temperature still remains an open question: the local modification of the material properties via short-term heat treatments followed by the stamping at room temperature is reported to be an effective [...] Read more.
The research of innovative methodologies to improve the Aluminium alloys formability at room temperature still remains an open question: the local modification of the material properties via short-term heat treatments followed by the stamping at room temperature is reported to be an effective alternative to the forming in warm conditions. In the present work, such a methodology has been applied to the deep drawing of an age-hardenable Aluminium alloy (AA6082-T6) using an experimental/numerical approach. A preliminary extensive material characterization was aimed at investigating the material behaviour: (i) in the as-received condition (peak hardening), (ii) in the supersaturated condition (obtained by physical simulation) and (iii) after being locally solutioned via laser heating. A Finite Element based approach (Abaqus CAE, v. 6.17) was then used to design the laser treatment of the blanks to be subsequently deep drawn at room temperature: a 2D axisymmetric model of the deep drawing process was coupled with the optimization platform modeFRONTIER in order to define the radial extent of the laser heat treated area able to maximize the Limit Drawing Ratio. The experimental tests were finally conducted for validation purposes and revealed the effectiveness of the adopted approach which allowed to improve the drawability of more than 20% with respect to the as received condition (T6). Full article
(This article belongs to the Special Issue Formability of Materials)
Show Figures

Graphical abstract

Open AccessArticle
On the Determination of Forming Limits in Polycarbonate Sheets
Materials 2020, 13(4), 928; https://doi.org/10.3390/ma13040928 - 19 Feb 2020
Abstract
By proposing an adaptation of the methodology usually used in metal forming, this paper aims to provide a general procedure for determining the forming limits, by necking and fracture, of polymeric sheet. The experimental work was performed by means of Nakajima specimens with [...] Read more.
By proposing an adaptation of the methodology usually used in metal forming, this paper aims to provide a general procedure for determining the forming limits, by necking and fracture, of polymeric sheet. The experimental work was performed by means of Nakajima specimens with different geometries to allow to obtain strains in the tensile, plane, biaxial and equibiaxial states for Polycarbonate sheet with 1 mm of thickness. The application of the time-dependent and flat-valley approaches used in metals has been revealed appropriate to characterize the onset of necking and obtain the forming limits of polycarbonate, despite the stable necking propagation typical of polymeric sheets. An analysis of the evolution of the strain paths along a section perpendicular to the crack allowed for a deeper understanding of the steady necking propagation behaviour and the adoption of the methodology of metals to polymers. The determination of the fracture strains was enhanced with the consideration of the principal strains of the DIC system in the last stage, just before fracture, due to the significant elastic recovery typical of polymeric sheets. As a result of this analysis, accurate formability limits by necking and fracture are obtained for polycarbonate sheet, together with the principal strain space, providing a general framework for analysing incremental sheet forming processes where the knowledge of the fracture limits is relevant. Full article
(This article belongs to the Special Issue Formability of Materials)
Show Figures

Figure 1

Open AccessArticle
Formability Limits, Fractography and Fracture Toughness in Sheet Metal Forming
Materials 2019, 12(9), 1493; https://doi.org/10.3390/ma12091493 - 08 May 2019
Cited by 3
Abstract
This paper is focused on the utilisation of double edge notched tension, staggered and shear tests to determine fracture toughness and the formability limits by fracture in principal strain space. The experiments were performed in test specimens with different geometries and ligament angles, [...] Read more.
This paper is focused on the utilisation of double edge notched tension, staggered and shear tests to determine fracture toughness and the formability limits by fracture in principal strain space. The experiments were performed in test specimens with different geometries and ligament angles, and the influence of strain hardening was taken into consideration by selecting two materials (aluminium AA1050-H111 and pure copper), with very different strain hardening exponents. Results are plotted in principal strain space, and the discussion is focused on the link between formability limits, fracture toughness and macroscopic fractography characteristics of the specimens that fail by mode I, mode II or mixed-mode. Full article
(This article belongs to the Special Issue Formability of Materials)
Show Figures

Figure 1

Open AccessArticle
Determination of Forming Limits in Sheet Metal Forming Using Deep Learning
Materials 2019, 12(7), 1051; https://doi.org/10.3390/ma12071051 - 30 Mar 2019
Cited by 2
Abstract
The forming limit curve (FLC) is used to model the onset of sheet metal instability during forming processes e.g., in the area of finite element analysis, and is usually determined by evaluation of strain distributions, derived with optical measurement systems during Nakajima tests. [...] Read more.
The forming limit curve (FLC) is used to model the onset of sheet metal instability during forming processes e.g., in the area of finite element analysis, and is usually determined by evaluation of strain distributions, derived with optical measurement systems during Nakajima tests. Current methods comprise of the standardized DIN EN ISO 12004-2 or time-dependent approaches that heuristically limit the evaluation area to a fraction of the available information and show weaknesses in the context of brittle materials without a pronounced necking phase. To address these limitations, supervised and unsupervised pattern recognition methods were introduced recently. However, these approaches are still dependent on prior knowledge, time, and localization information. This study overcomes these limitations by adopting a Siamese convolutional neural network (CNN), as a feature extractor. Suitable features are automatically learned using the extreme cases of the homogeneous and inhomogeneous forming phase in a supervised setup. Using robust Student’s t mixture models, the learned features are clustered into three distributions in an unsupervised manner that cover the complete forming process. Due to the location and time independency of the method, the knowledge learned from formed specimen up until fracture can be transferred on to other forming processes that were prematurely stopped and assessed using metallographic examinations, enabling probabilistic cluster membership assignments for each frame of the forming sequence. The generalization of the method to unseen materials is evaluated in multiple experiments, and additionally tested on an aluminum alloy AA5182, which is characterized by Portevin-LE Chatlier effects. Full article
(This article belongs to the Special Issue Formability of Materials)
Show Figures

Figure 1

Back to TopTop