scholarly journals Analysis of Forming Limits in Sheet Metal Forming with Pattern Recognition Methods. Part 2: Unsupervised Methodology and Application

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 1892 ◽  
Author(s):  
Christian Jaremenko ◽  
Emanuela Affronti ◽  
Andreas Maier ◽  
Marion Merklein
Keyword(s):  
Pattern Recognition ◽  
Sheet Metal ◽  
Optical Measurement ◽  
Unsupervised Classification ◽  
Evaluation Methods ◽  
Time Dependent ◽  
Measuring System ◽  
Forming Limit ◽  
Element Analysis

The forming limit curve (FLC) is used in finite element analysis (FEA) for the modeling of onset of sheet metal instability during forming. The FLC is usually evaluated by achieving forming measurements with optical measurement system during Nakajima tests. Current evaluation methods such as the standard method according to DIN EN ISO 12004-2 and time-dependent methods limit the evaluation range to a fraction of the available information and show weaknesses in the context of brittle materials that do not have a pronounced constriction phase. In order to meet these challenges, a supervised pattern recognition method was proposed, whose results depend on the quality of the expert annotations. In order to alleviate this dependence on experts, this study proposes an unsupervised classification approach that does not require expert annotations and allows a probabilistic evaluation of the onset of localized necking. For this purpose, the results of the Nakajima tests are examined with an optical measuring system and evaluated using an unsupervised classification method. In order to assess the quality of the results, a comparison is made with the time-dependent method proposed by Volk and Hora, as well as expert annotations, while validated with metallographic investigations. Two evaluation methods are presented, the deterministic FLC, which provides a lower and upper limit for the onset of necking, and a probabilistic FLC, which allows definition of failure quantiles. Both methods provide a necking range that shows good correlation with the expert opinion as well as the results of the time-dependent method and metallographic examinations.

scholarly journals Determination of Forming Limits in Sheet Metal Forming Using Deep Learning

Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1051 ◽  
Author(s):  
Christian Jaremenko ◽  
Nishant Ravikumar ◽  
Emanuela Affronti ◽  
Marion Merklein ◽  
Andreas Maier
Keyword(s):  
Sheet Metal ◽  
Optical Measurement ◽  
Forming Limit ◽  
Forming Process ◽  
Element Analysis ◽  
Cluster Membership ◽  
Measurement Systems ◽  
Pattern Recognition Methods ◽  
Student’S T ◽  
Available Information

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.

Optimization of Sheet Metal Process Parameters of a Shield Case Piece Using Computer Simulation

2006 ◽  
Vol 510-511 ◽  
pp. 330-333
Author(s):  
M.C. Curiel ◽  
Ho Sung Aum ◽  
Joaquín Lira-Olivares
Keyword(s):  
Sheet Metal ◽  
Thickness Distribution ◽  
Forming Limit Diagram ◽  
Forming Limit ◽  
Physical Processes ◽  
Forming Process ◽  
Element Analysis ◽  
One Step ◽  
Range Of Values ◽  
Principal Strains

Numerical simulations based on Finite Element Analysis (FEA) are widely used to predict and evaluate the forming parameters before performing the physical processes. In the sheet metal industry, there are basically two types of FE programs: the inverse (one-step) programs and the incremental programs. In the present paper, the forming process of the shield case piece (LTA260W1-L05) was optimized by performing simulations with both types of software. The main analyzed parameter was the blankholding force while the rest of the parameters were kept constant. The criteria used to determine the optimum value was based on the Forming Limit Diagram (FLD), fracture and wrinkling of the material, thickness distribution, and the principal strains obtained. It was found that the holding force during the forming process deeply affects the results, and a range of values was established in which the process is assumed to give a good quality piece.

APPLICATION OF FORMING LIMIT CRITERIA BASED ON PLASTIC INSTABILITY CONDITION TO METAL FORMING PROCESS

2008 ◽  
Vol 22 (31n32) ◽  
pp. 5680-5685
Author(s):  
SEONG-CHAN HEO ◽  
TAE-WAN KU ◽  
JEONG KIM ◽  
BEOM-SOO KANG ◽  
WOO-JIN SONG
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Thin Sheet ◽  
Plastic Instability ◽  
Theoretical Background ◽  
Forming Limit ◽  
Preliminary Evaluation ◽  
Forming Process ◽  
Element Analysis

Metal forming processes such as hydroforming and sheet metal forming using tubular material and thin sheet metal have been widely used in lots of industrial fields for manufacturing of various parts that could be equipped with mechanical products. However, it is not easy to design sequential processes properly because there are various design variables that affect formability of the parts. Therefore preliminary evaluation of formability for the given process should be carried out to minimize time consumption and development cost. With the advances in finite element analysis technique over the decades, the formability evaluation using numerical simulation has been conducted in view of strain distribution and final shape. In this paper, the application of forming limit criteria is carried out for the tube hydroforming and sheet metal forming processes using theoretical background based on plastic instability conditions. Consequently, it is confirmed that the local necking and diffuse necking criteria of sheet are suitable for formability evaluation of both hydroforming and sheet metal forming processes.

Research on the Forming Path for Fabricating the Sheet-Metal Part with Non-Horizontal End Face Using CNC Incremental Forming

2014 ◽  
Vol 599-601 ◽  
pp. 413-416 ◽  
Author(s):  
Hu Zhu ◽  
Jin Ju ◽  
Yi Bo Liu
Keyword(s):  
Sheet Metal ◽  
Incremental Forming ◽  
Analysis Method ◽  
Metal Part ◽  
Element Analysis ◽  
Sheet Metal Parts ◽  
Cnc Incremental Forming ◽  
Forming Technology ◽  
The Finite Element Analysis

For the purpose of the fabrication of the sheet-metal parts with non-horizontal end face using the sheet metal CNC incremental forming technology, two kinds of path generating methods, namely the level path perpendicular to Z axis method and the equidistant path parallel to sheet metal are proposed in this paper. Both of the paths are generated by Visual C++ and OpenGL graphics library, the effect of the two kinds of forming paths to the forming quality of the sheet part with non-horizontal end face is researched using the finite element analysis method in this paper.

Prediction of Limiting Strains for Square Pattern – Square Hole Perforated Commercial Pure Aluminium Sheets

2012 ◽  
Vol 548 ◽  
pp. 382-386 ◽  
Author(s):  
G. Venkatachalam ◽  
S. Narayanan ◽  
Narayanan C. Sathiya
Keyword(s):  
Sheet Metal ◽  
Forming Limit Diagram ◽  
Forming Limit ◽  
Pure Aluminium ◽  
Element Analysis ◽  
Material Condition ◽  
Geometrical Features ◽  
Perforated Sheet ◽  
Commercial Aluminium ◽  
Aluminium Sheets

Forming limit diagram (FLD) is the most appropriate tool used to obtain the safe strain region in sheet metal forming industries. This FLD is based on limiting values of major and minor strains. This Limiting strain is the strain at the onset of fracture / necking in a sheet metal. It is influenced by the material / condition of the material, strain condition in geometrical features of a sheet metal. In this paper, square pattern – square holed, perforated commercial aluminium sheets are considered for the study. The limiting strain for the above perforated sheet metals is predicted using finite element analysis. It is found that the limiting strain is controlled by percentage of open area, ligament ratio and hole size.

Identifying Variable Effects on the Dimensional Quality of Compliant Assembly, Using Computer Experiments

2002 ◽  
Author(s):  
Stefan Dahlstro¨m ◽  
S. Jack Hu ◽  
Rikard So¨derberg
Keyword(s):  
Sheet Metal ◽  
Computer Experiments ◽  
Tolerance Analysis ◽  
Response Model ◽  
Element Analysis ◽  
Design Of Computer Experiments ◽  
Compliant Assembly ◽  
Aesthetic Form ◽  
Input Variables

Compliant sheet metal assemblies are often used as support structures in automobiles, airplanes and appliances. These structures not only provide a metrology frame for other modules to be assembled, but also give the product its aesthetic form. For this reason, the dimension quality of the assemblies is a very important factor to control, in order to make sure that the product will function as planned and continuously keep the product cost low. The assembly is influenced by variations in the component parts and the assembly processes. Tolerance analysis, as conducted in most industries today, is normally based on the assumption of rigid parts and is thus not always valid for sheet metal assemblies, due to their compliance. This paper will present a method, based on finite element analysis (FEA) and design of computer experiments, of identifying the influence of input variables on the final geometry variation of the assembly. The influence and the interactions among the input variables are analyzed with a response model that has been constructed, using the simulation results. This response model could be used to identify the important variables that need to be controlled in assembly. An example application is included, in order to demonstrate the simulation model and response model construction. Analysis of the results from the simulations can facilitate the design of the assembly process, in order to control the dimensional quality of the product.

scholarly journals Experimental And Theoretical Determination Of Forming Limit Curve

2015 ◽  
Vol 60 (3) ◽  
pp. 1881-1886
Author(s):  
J. Adamus ◽  
K. Dyja ◽  
M. Motyka
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Fracture Initiation ◽  
Forming Limit ◽  
Forming Process ◽  
Element Analysis ◽  
Metal Forming Process

Abstract The paper presents a method for determining forming limit curves based on a combination of experiments with finite element analysis. In the experiment a set of 6 samples with different geometries underwent plastic deformation in stretch forming till the appearance of fracture. The heights of the stamped parts at fracture moment were measured. The sheet - metal forming process for each sample was numerically simulated using Finite Element Analysis (FEA). The values of the calculated plastic strains at the moment when the simulated cup reaches the height of the real cup at fracture initiation were marked on the FLC. FLCs for stainless steel sheets: ASM 5504, 5596 and 5599 have been determined. The resultant FLCs are then used in the numerical simulations of sheet - metal forming. A comparison between the strains in the numerically simulated drawn - parts and limit strains gives the information if the sheet - metal forming process was designed properly.

Development and Application of the Finite Element Analysis Program of the Stress-Based Forming Limit Criterion for Sheet Metal Forming

2007 ◽  
Vol 561-565 ◽  
pp. 1995-1998
Author(s):  
Ming He Chen ◽  
J.H. Li ◽  
Lin Gao ◽  
Dun Wen Zuo ◽  
Min Wang
Keyword(s):  
Numerical Simulation ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Forming Limit ◽  
Analysis Program ◽  
Element Analysis ◽  
The Finite Element Analysis

In order to solve the problem existed in the numerical simulation of sheet metal forming for its use the strain-based forming limit diagram as criterion, which has the flaw of dependence on the strain paths, this paper develops the finite element analysis program based on the stress forming limit criterion applicable to the blank plastic forming technique, which follows the stress-strain transformation relationship when the sheet metal is undergoing plastic deformation, chooses Hill’s quadratic normal anisotropic criterion as computational model and selects the commercial finite element code Dynaform as its development environment. Also it be analyzed the finite element numerical simulation results of two deep drawing parts by the developed program module and realizes the prediction of sheet metal forming limit adopting the FLSD as criterion. The stress-based forming limit criterion for the developed program provides a new means to analyze the forming limit for the multistage sheet metal forming.

Customizing Procedure of Finite Element Analysis for Sheet Metal Forming

2014 ◽  
Vol 933 ◽  
pp. 212-215
Author(s):  
Xu Dong Xu ◽  
Guang Jun Li ◽  
Zhan Chong Wei ◽  
Fang Xue Li
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Model Building ◽  
Element Analysis ◽  
Standardization Procedure ◽  
Set Up

Based on Pam-Stamp software platform, standardization procedure of finite element analysis for sheet metal forming was customized by set up module such as model building, meshing, setting of boundary conditions, calculation submitting, viewing of results and report generating. Standardization procedure has been successfully applied in the development of new products, which shortens the preparation cycle of procedure, improves the forming quality of the parts and enhances the capability for rapidly researching and developing.

Sign in / Sign up

Export Citation Format

Share Document