scholarly journals Determining Forming Limit Diagrams Using Sub-Sized Specimen Geometry and Comparing FLD Evaluation Methods

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 484
Author(s):  
Kateřina Rubešová ◽  
Martin Rund ◽  
Sylwia Rzepa ◽  
Hana Jirková ◽  
Štěpán Jeníček ◽  
...  
Keyword(s):  
Automotive Industry ◽  
Metal Forming ◽  
Fracture Strain ◽  
Forming Limit Diagram ◽  
Local Strain ◽  
Evaluation Methods ◽  
Forming Limit ◽  
Boron Steel ◽  
Specimen Thickness ◽  
Strain Rates

Sheet metal forming boundaries are established using the forming limit diagram (FLD). The Nakajima and Marciniak tests, which are based on stretching a material using a punch, are the most commonly used methods for determining the FLD or fracture forming limit diagram (FFLD). The results are usually evaluated by calculating local strain, strain rates, specimen thickness reduction or fracture strain. When the amount of experimental material is insufficient, miniaturization of the testing specimens may be a solution. However, the interchangeability of the results for standard and miniaturized specimens has not been proven yet. In this study, the Nakajima tests were performed using standard and sub-sized specimens made of manganese–boron steel 22MnB5, commonly used in the automotive industry. Afterwards, four FLD/FFLD evaluation methods were applied and compared. The miniaturized specimens yielded higher strain values, which was explained by the varied ratio of material thickness/punch diameter and different bending conditions. The highest compliance of the results was recorded for the standard and miniaturized FFLD.

Reliability Analysis of the Tube Hydroforming Process Based on Forming Limit Diagram

2005 ◽  
Vol 128 (3) ◽  
pp. 402-407 ◽  
Author(s):  
Bing Li ◽  
Don R. Metzger ◽  
Tim J. Nye
Keyword(s):  
Automotive Industry ◽  
Metal Forming ◽  
Tube Hydroforming ◽  
Forming Limit Diagram ◽  
Probability Of Failure ◽  
Alternative Methods ◽  
Forming Limit ◽  
Forming Process ◽  
Hydroforming Process ◽  
Free Bulging

Tube hydroforming is an attractive manufacturing process in the automotive industry because it has several advantages over alternative methods. In order to determine the reliability of the process, a new method to assess the probability of failure is proposed in this paper. The method is based on the reliability theory and the forming limit diagram, which has been extensively used in metal forming as the criteria of formability. From the forming limit band in the forming limit diagram, the reliability of the forming process can be evaluated. A tube hydroforming process of free bulging is then introduced as an example to illustrate the approach. The results show this technique to be an innovative approach to avoid failure during tube hydroforming.

Forming limit diagrams by including the M–K model in finite element simulation considering the effect of bending

2016 ◽  
Vol 232 (8) ◽  
pp. 625-636 ◽  
Author(s):  
Mostafa Habibi ◽  
Ramin Hashemi ◽  
Ahmad Ghazanfari ◽  
Reza Naghdabadi ◽  
Ahmad Assempour
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Metal Forming ◽  
Forming Limit Diagram ◽  
Element Model ◽  
Forming Limit ◽  
Finite Element Models ◽  
Element Simulation ◽  
Simple Tension ◽  
Out Of Plane

Forming limit diagram is often used as a criterion to predict necking initiation in sheet metal forming processes. In this study, the forming limit diagram was obtained through the inclusion of the Marciniak–Kaczynski model in the Nakazima out-of-plane test finite element model and also a flat model. The effect of bending on the forming limit diagram was investigated numerically and experimentally. Data required for this simulation were determined through a simple tension test in three directions. After comparing the results of the flat and Nakazima finite element models with the experimental results, the forming limit diagram computed by the Nakazima finite element model was more convenient with less than 10% at the lower level of the experimental forming limit diagram.

A New Approach to the Evaluation of Forming Limits in Sheet Metal Forming

2015 ◽  
Vol 639 ◽  
pp. 333-338 ◽  
Author(s):  
Marion Merklein ◽  
Andreas Maier ◽  
Daniel Kinnstätter ◽  
Christian Jaremenko ◽  
Emanuela Affronti
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Forming Limit Diagram ◽  
Forming Limit ◽  
Strain History ◽  
Failure Behavior ◽  
Forming Limits ◽  
Optical Strain Measurement ◽  
Optical Strain

The forming limit diagram (FLD) is at the moment the most important method for the prediction of failure within sheet metal forming operations. Key idea is the detection of the onset of necking in dependency of different sample geometry. Whereas the standardized evaluation methods provides very robust and reliable results for conventional materials like deep drawing steels, the determined forming limits for modern light materials are often too conservative due to the different failure behavior. Therefore, within this contribution a new and innovative approach for the identification of the onset of necking will be presented. By using a pattern recognition-based approach in combination with an optical strain measurement system the complete strain history during the test can be evaluated. The principal procedure as well as the first promising results are presented and discussed.

Theoretical and Experimental Evaluation of the Formability of Anisotropic Zinc Sheets

2011 ◽  
Vol 473 ◽  
pp. 390-395 ◽  
Author(s):  
Yann Jansen ◽  
Roland E. Logé ◽  
Marc Milesi ◽  
S. Manov ◽  
Elisabeth Massoni
Keyword(s):  
Metal Forming ◽  
Mechanical Response ◽  
Damage Model ◽  
Rolling Direction ◽  
Forming Limit Diagram ◽  
Tensile Tests ◽  
Forming Limit ◽  
The Past ◽  
Force Criterion ◽  
Critical Strains

. Formability of metal sheet has been widely studied for the past 40 years. This study leads to the well known Forming Limit Diagram (FLD) proposed by Keeler and Backhofen [1]. Such a diagram needs typical drawing and stretching experiments to be achieved. Lots of different metals have been considered as steel, aluminium, titanium or magnesium alloys [2]. Despite of the large amount of papers about sheet metal forming, few deal with Zinc sheets. The material has an anisotropic mechanical response due to its hexagonal crystallographic lattice and its microstructural texture. In the presented work, Nakazima and tensile tests have been performed for different mechanical orientations (0°, 45° and 90° angle to the rolling direction) in order to characterise this typical response. A high anisotropic behaviour has been noticed for the hardening and for the critical strains. The FLD is therefore a function of the orientation. Moreover thickness sensitivity is observed and leads to some criticisms about the plane stress assumption usually used in the FLD predictive models [3, 4]. The Modified Maximum Force Criterion (MMFC) is evaluated, and discussed. Then, this model is compared to a damage model used in [5] within an FEM formulation.

An Aid to Practical Sheet Metal Forming

1970 ◽  
Vol 12 (6) ◽  
pp. 443-445
Author(s):  
R. Pearce ◽  
J. Woodthorpe
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Forming Limit Diagram ◽  
Forming Limit ◽  
Analytical Technique

Until recently, no analytical technique was available for the study of failure in complex sheet metal pressing. However, if the maximum ( e1) and minimum ( e2) principal surface strains at failure on sheet metal pressing are measured, a plot of e1 against e2 results in a so-called forming limit diagram. FLD can be constructed in the laboratory and used as an aid to die try-out, production failures and metal specification.

Enhancing the Mechanical Properties and Formability of Cold Rolled Closed Annealed Sheet for Automobile Applications

2019 ◽  
Vol 11 (4) ◽  
Author(s):  
S.P. Sundar Singh Sivam ◽  
L. Ganesh Babu ◽  
D. Kumaran
Keyword(s):  
Sheet Metal ◽  
Metal Forming ◽  
Forming Limit Diagram ◽  
High Strength ◽  
Forming Limit ◽  
Low Carbon ◽  
Resistance Alloy ◽  
Cold Rolled ◽  
Annealed Sheet ◽  
Metallic Sheet

Designers of high pace advanced vehicles in aerospace industries particularly vehicle manufacturing types are placing more needs at the sheet metal forming enterprise by designing components from the high strength thermal resistance alloy. The principle goal of the observation is to test the mechanical, formability parameters and Erichsen cupping values of a sample of cold rolled closed annealed sheet. The quantity of strain that a metallic sheet can tolerate just before localized failure is called limit strain. The boundaries of formability in sheet metal operations are defined regarding the primary traces via the forming limit diagram (FLD). To be useful for engineering purposes, FLD needs to be simple enough so its parameters can be evaluated without difficulty ideally by way of uniaxial tests. The consequences confirmed that the formability of steel having decreased percentage of carbon is forming lesser. It changed into pressure distribution and the grain density of the sheet verifies the formability. The best grouping of strength and ductile properties are noted for metal with the low carbon and higher forming assets.

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