A Modified Storen-Rice Bifurcation Analysis of Sheet Metal Forming Limit Diagrams

2012 ◽  
Vol 79 (6) ◽  
Author(s):  
A. Jaamialahmadi ◽  
M. Kadkhodayan
Keyword(s):  
Bifurcation Analysis ◽  
Metal Forming ◽  
Optimization Procedure ◽  
Forming Limit ◽  
Forming Limit Diagrams ◽  
Left Hand ◽  
Modified Equations ◽  
Special Cases ◽  
Subsequent Yield Surface ◽  
Prediction Approach

Bifurcation analysis is a theoretical prediction approach to measure the FLD when the localized neck causes development of vertex on subsequent yield surface as was adopted by Storen-Rice. Some analyses lead to solutions for special cases such as zero and minimum extension. They offer an equation which needs to be optimized with respect to the minimum limit strain versus neck orientation for the whole domain of FLD. Moreover, the previous reported results for the left-hand side of FLD are not quite satisfactory. In this paper, a re-investigation into bifurcation analysis adopted by S-R lead to modified equations which significantly improved FLD and could be respected as a more general approach to find FLD theoretically. The derivation and optimization procedure of equations are indicated and discussed in detail. The predicted limit strains are studied for different work hardening coefficients and compared with Storen-Rice, Zhu and some experimental data and the obtained results show more agreement. Furthermore, the present restrictions and the required conditions for validation of the Zhu approach are fully discussed.

Effects of Processing, Texture and Temperature on the Formability of AZ31 and ZE10 Sheets

2011 ◽  
Vol 690 ◽  
pp. 298-301 ◽  
Author(s):  
Dietmar Letzig ◽  
Lennart Stutz ◽  
Jan Bohlen ◽  
Karl Ulrich Kainer
Keyword(s):  
Metal Forming ◽  
Alloy Composition ◽  
Deformation Mechanisms ◽  
Forming Limit ◽  
Forming Limit Diagrams ◽  
Sheet Formability ◽  
Strain Paths ◽  
Twin Roll Cast ◽  
Twin Roll ◽  
Forming Limit Curves

Sheet metal forming experiments have been carried out on AZ31 and ZE10 sheets produced by rolling conventionally DC cast slabs as well as twin roll cast (TRC) strips. Nakajima tests were performed on the various sheet materials over the temperature range from RT to 200 °C using Hasek type samples of specified geometries to generate various strain paths. The strain path data were used to derive the forming limit curves as plotted in forming limit diagrams for the two alloys. The temperature dependence of the sheet formability is discussed in terms of the operating deformation mechanisms and the roles of alloy composition, initial texture and processing history.

An Investigation Into the Prediction of Forming Limit Diagrams for Normal Anisotropic Material Based on Bifurcation Analysis

2011 ◽  
Vol 78 (3) ◽  
Author(s):  
A. Jaamialahmadi ◽  
M. Kadkhodayan
Keyword(s):  
Bifurcation Analysis ◽  
Work Hardening ◽  
Yield Criterion ◽  
Forming Limit Diagram ◽  
Optimization Method ◽  
Forming Limit ◽  
Proportional Loading ◽  
Normal Anisotropy ◽  
Left Hand ◽  
Prediction Limit

In this paper, formula derivation for bifurcation analysis based on a constitutive model including Hill 48 yield criterion with normal anisotropy of a pointed vertex on subsequent yield loci to predict the entire forming limit diagram (FLD) is carried out. Proportional loading, total deformation theory of plasticity, and power law relation are assumed. Predicted limit strains for Hill’s zero and minimum extension of localized neck orientation is derived. The dominancy of zero extension and minimum extension on the left-hand side of FLDs for different work hardening components and r-values are investigated in detail. An implicit four order rational function equation for major strain, which preferred that the orientation of neck correspond to minimum value of limit strain, is found by a developed optimization method. Optimized predicted limit strains for typical work hardening components and different r-values are obtained and discussed. Limit strains vary directly on the left and reversely on the right-hand side of FLD when r-value increases. Comparison between the predicted and experimental results exhibits a better agreement compared with those from the isotropic material. In addition, on the left-hand side, the resulted prediction limit strains represent a full dependency to assumed yield criterion. A comparison between the current work and Chow et al. results are performed and discussed in detail.

Formability of High Strength Sheet Metals with Special Regard to the Effect of the Influential Factors on the Forming Limit Diagrams

2015 ◽  
Vol 812 ◽  
pp. 271-275 ◽  
Author(s):  
Miklós Tisza ◽  
Péter Zoltán Kovács ◽  
Zsolt Lukács ◽  
Antal Kiss ◽  
Gaszton Gál
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
High Strength Steels ◽  
High Strength ◽  
Forming Limit ◽  
Experimental Investigations ◽  
Sheet Metals ◽  
Forming Limit Diagrams ◽  
Research Activities

Car manufacturing is one of the main target fields of sheet metal forming: thus sheet metal forming is exposed to the same challenges as the automotive industry. The continuously increasing demand on lower consumption and lower CO2 emission means the highest challenges on materials developments besides design and construction. As a general requirement, the weight reduction and light weight construction principles should be mentioned together with the increased safety prescriptions which require the application of high strength steels. However, the application of high strength steels often leads to formability problems. Forming Limit Diagrams (FLD) are the most appropriate tools to characterize the formability of sheet metals. Theoretical and experimental investigations of forming limit diagrams are in the forefront of todays’ research activities.

Numerical and Experimental Study of Forming Limit Diagrams in Sheet Metal Forming and Seamed Tube Hydroforming

2013 ◽  
Vol 395-396 ◽  
pp. 914-919 ◽  
Author(s):  
Ren Tao Zhang ◽  
Xian Feng Chen ◽  
Hai Bo Su ◽  
Zhi Yong Chen
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Experimental Approach ◽  
Tube Hydroforming ◽  
Numerical Approach ◽  
Forming Limit ◽  
Forming Limit Diagrams ◽  
Localized Necking ◽  
Biaxial Stretching

The paper establishes the forming limit diagrams (FLDs) for QSTE340 seamed tube hydroforming and the mother sheet metal forming by numerical approach and experimental approach. A novel experimental approach is proposed to evaluate the formability for tube hydroforming under biaxial stretching through elliptical bulging.Then the Nakazima and three types of tube hydroforming tests are simulated with finite element (FE) program LS-DYNA. The failure criterion of thickness gradient criterion (TGC) is introduced. The FLDs for seamed tube hydroforming and the mother sheet metal forming are constructed. The comparison of results based on TGC with experimental data shows the TGC is an appropriate one to determine the onset of localized necking. Finally, the differences and relationships between the FLDs for the seamed tube hydroforming and the mother sheet metal forming are discussed.

Investigation of Influence Parameters on Forming Limit Diagrams of Aluminum Alloy-AA2024

2011 ◽  
Vol 473 ◽  
pp. 382-389 ◽  
Author(s):  
Gokhan Celik ◽  
Bilgin Kaftanoğlu ◽  
Celalettin Karadogan
Keyword(s):  
Aluminum Alloy ◽  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Material Characterization ◽  
Forming Limit ◽  
Uniaxial Tensile ◽  
Sheet Metals ◽  
Forming Limit Diagrams ◽  
Punch Speed

Sheet metal forming technology is the keyword for many industries such as aerospace, aeronautics and automobile industries. Customer expectations, quality and safety requirements and market competitions require sheet metal forming operations to be well analyzed before the process to fulfill all these requirements. In this study, combination of FEA (finite element analysis) and mechanical material characterization were used in order to improve sheet metal forming operations while considering cost and quality. On the material characterization side of the studies, simple uniaxial tensile tests were conducted to obtain anisotropy parameters and yield points along different directions and hydraulic bulge test (HBT) was performed to obtain plastic behavior of the material up to 0.7 strains. Deformation measurements were conducted using optical measurement system GOM-ARAMIS while a 60-ton hydraulic press; Zwick/Roell BUP600 was used to deform the sheet part AA2024-0 aluminum alloy. Effects of process parameters, which are initial material thickness, lubrication and punch speed, on sheet metal formability and forming limit diagrams (FLDs) were investigated. On the study of thickness effects, sheet metals those having 0.81mm, 1.27mm and 1.60mm thickness were tested. Punch velocities of 250mm/min, 500mm/min and 750mm/min were used to investigate effect of punch speed on formability of sheet metals. Finally, PTFE (Polytetrafluoroethylene), paraffin lubricated and dry conditions were presented to obtain friction effects. FE analyses were performed to simulate experiments and to obtain friction coefficients of different lubricants. Good correlations were observed between numerical simulations and experimental results.

An Intelligent Tool to Predict Fracture in Sheet Metal Forming Operations

2007 ◽  
Vol 344 ◽  
pp. 841-846
Author(s):  
Rosanna Di Lorenzo ◽  
Giuseppe Ingarao ◽  
Fabrizio Micari
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Production Quality ◽  
Forming Limit ◽  
Fracture Criteria ◽  
Predictive Tool ◽  
Forming Limit Diagrams ◽  
Early Results

One of the main issues in sheet metal forming operations design is the determination of formability limits in order to prevent necking and fracture. In fact, the ability to predict fracture represents a powerful tool to improve the production quality in mechanical industry. Many researchers investigated the problem here addressed, mainly studying forming limit diagrams (FLD) or developing fracture criteria which are able to foresee fracture defects for different processes. In this paper, the author present some early results of a research project focused on the application of artificial intelligence (AI) for ductile fracture prediction in sheet metal forming operations. The main advantage of the application of AI tools and in particular, of artificial neural networks (ANN), is the possibility to obtain a predictive tool with a wide applicability. The prediction results obtained in this paper fully demonstrate the usefulness of the proposed approach.

Surrogate POD models for building forming limit diagrams of parameterized sheet metal forming applications

2013 ◽  
Author(s):  
M. Hamdaoui ◽  
Guénhaël Le Quilliec ◽  
Piotr Breitkopf ◽  
Pierre Villon
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Forming Limit ◽  
Forming Limit Diagrams

scholarly journals Refinements of the Lower Bounds of the Jensen Functional

2011 ◽  
Vol 2011 ◽  
pp. 1-13 ◽  
Author(s):  
Iva Franjić ◽  
Sadia Khalid ◽  
Josip Pečarić
Keyword(s):  
Lower Bounds ◽  
Jensen Inequality ◽  
Left Hand ◽  
Right Hand ◽  
Special Cases ◽  
Jensen Functional ◽  
The Difference ◽  
The Right

The lower bounds of the functional defined as the difference of the right-hand and the left-hand side of the Jensen inequality are studied. Refinements of some previously known results are given by applying results from the theory of majorization. Furthermore, some interesting special cases are considered.

Preliminary Studies on the Determination of FLD for Single Point Incremental Sheet Metal Forming

2012 ◽  
Vol 504-506 ◽  
pp. 863-868 ◽  
Author(s):  
Miklos Tisza ◽  
Péter Zoltán Kovács ◽  
Zsolt Lukács
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
New Technologies ◽  
Single Point ◽  
Research Work ◽  
Dimensional Accuracy ◽  
Forming Limit ◽  
Incremental Sheet Metal Forming

Development of new technologies and processes for small batch and prototype production of sheet metal components has a very important role in the recent years. The reason is the quick and efficient response to the market demands. For this reasons new manufacturing concepts have to be developed in order to enable a fast and reliable production of complex components and parts without investing in special forming machines. The need for flexible forming processes has been accelerated during the last 15 years, and by these developments the technology reaches new extensions. Incremental sheet metal forming (ISMF) may be regarded as one of the promising developments for these purposes. A comprehensive research work is in progress at the University of Miskolc (Hungary) to study the effect of important process parameters with particular emphasis on the shape and dimensional accuracy of the products and particularly on the formability limitations of the process. In this paper, some results concerning the determination of forming limit diagrams for single point incremental sheet metal forming will be described.

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