Influence of Pre-Forming on the Forming Limit Diagram of Aluminum and Steel Sheets

2007 ◽  
pp. 113-118
Author(s):  
Massimo Tolazzi ◽  
Marion Merklein
Keyword(s):  
Forming Limit Diagram ◽  
Forming Limit ◽  
Steel Sheets

Influence of Pre-Forming on the Forming Limit Diagram of Aluminum and Steel Sheets

2007 ◽  
Vol 344 ◽  
pp. 113-118 ◽  
Author(s):  
Massimo Tolazzi ◽  
Marion Merklein
Keyword(s):  
Dual Phase Steel ◽  
Process Analysis ◽  
Forming Limit Diagram ◽  
Forming Limit ◽  
Linear Strain ◽  
Forming Limit Diagrams ◽  
Steel Sheets ◽  
Biaxial Stretching ◽  
Strain Paths

This paper presents a method for the experimental determination of forming limit diagrams under non linear strain paths. The method consists in pre-forming the sheets under two different strain conditions: uniaxial and biaxial, and then stretching the samples, cut out of the preformed sheets, using a Nakajima testing setup. The optical deformation measurement system used for the process analysis (ARAMIS, Company GOM) allows to record and to analyze the strain distribution very precisely with respect to both time and space. As a reference also the FLDs of the investigated grades (the deep drawing steel DC04, the dual phase steel DP450 and the aluminum alloy AA5754) in as-received conditions were determined. The results show as expected an influence of the pre-forming conditions on the forming limit of the materials, with an increased formability in the case of biaxial stretching after uniaxial pre-forming and a reduced formability for uniaxial load after biaxial stretching if compared to the case of linear strain paths. These effects can be observed for all the investigated materials and can be also described in terms of a shifting of the FLD, which is related to the art and magnitude of the pre-deformation.

Formability Analysis of Tailor-Welded Blanks of Different Thickness Ratios

2005 ◽  
Vol 127 (4) ◽  
pp. 743-751 ◽  
Author(s):  
L. C. Chan ◽  
C. H. Cheng ◽  
S. M. Chan ◽  
T. C. Lee ◽  
C. L. Chow
Keyword(s):  
Finite Element ◽  
Forming Limit Diagram ◽  
Thickness Ratio ◽  
Forming Limit ◽  
Uniaxial Tensile ◽  
Base Metals ◽  
Steel Sheets ◽  
Major Strain ◽  
Tailor Welded Blanks ◽  
Different Thickness

This paper presents a formability analysis of tailor-welded blanks (TWBs) made of cold rolled steel sheets with varying thicknesses. Steel sheets ranging between 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, and 1.0 mm in thickness were used to produce TWBs of different thickness combinations. The primary objective of this paper is to characterize the effects of thickness ratios on the forming limit diagram (FLD) for a particular type of TWB. The TWBs chosen for the investigation are designed with the weld line located in the center of the specimens perpendicular to the principal strain direction. Nd:YAG laser butt-welding was used to prepare different tailor-made blank specimens for uniaxial tensile tests and Swift tests. The experimental results of the uniaxial tensile test clearly revealed that there were no significant differences between the tensile strengths of TWBs and those of the base metals. After the Swift tests, the formability of TWBs was analyzed in terms of two measures: The forming limit diagram and minimum major strain. The experimental findings indicated that the higher the thickness ratio, the lower the level of the forming limit curve (FLC) and the lower the formability of the TWBs. The findings also show an inverse proportional relationship between thickness ratios and minimum major strains. TWBs with a thickness ratio of close to 1 were found to have a minimum major strain closer to those of base metals. The effects of different thickness ratios on TWBs were further analyzed with a finite element code in a computer-aided engineering package, PAM-STAMP, while the failure criteria of the TWBs in the finite element analysis were addressed by the FLCs which were obtained from the experiments. However, the weld of the TWB in the simulation was simply treated as a thickness step, whereas its heat affected zones were sometimes disregarded, so that the effects of the thickness ratio could be significantly disclosed without the presence of weld zones. The results of the simulation should certainly assist to clarify and explain the effects of different thickness ratios on TWBs.

scholarly journals Experimental and Numerical Investigations into the Failure Mechanisms of TRIP700 Steel Sheets

Metals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 1073 ◽  
Author(s):  
Niloufar Habibi ◽  
Veera Sundararaghavan ◽  
Ulrich Prahl ◽  
Ali Ramazani
Keyword(s):  
Forming Limit Diagram ◽  
Forming Limit ◽  
Failure Behavior ◽  
Damage Initiation ◽  
Localized Necking ◽  
Steel Sheets ◽  
Numerical Studies ◽  
Necking Criterion ◽  
Stress States ◽  
Damage Criteria

The formability and failure behavior of transformation-induced plasticity (TRIP) steel blanks were investigated through various stress states. The forming limit diagram (FLD) at fracture was constructed both experimentally and numerically. Numerical studies were performed to evaluate the applicability of different damage criteria in predicting the FLD as well as complex cross-die deep drawing process. The fracture surface and numerical results reveal that the material failed in a different mode for different strain path. Therefore, the Tresca model, which is based on shear stress, accurately predicted the conditions where shear had a profound effect on the damage initiation, whereas Situ localized necking criterion could calculate the conditions in which localization was dominant.

scholarly journals Experimental and Numerical Investigations into the Failure Mechanisms of TRIP700 Steel Sheets

2018 ◽  
Author(s):  
Niloufar Habibi ◽  
Veera Sundararaghavan ◽  
Ulrich Prahl ◽  
Ali Ramazani
Keyword(s):  
Forming Limit Diagram ◽  
Forming Limit ◽  
Failure Behavior ◽  
Damage Initiation ◽  
Localized Necking ◽  
Steel Sheets ◽  
Numerical Studies ◽  
Necking Criterion ◽  
Stress States ◽  
Damage Criteria

The formability and failure behavior of TRIP steel blanks were investigated through various stress states. The forming limit diagram (FLD) at fracture is constructed both experimentally and numerically. Numerical studies are performed to evaluate the applicability of different damage criteria in predicting the FLD as well as complex cross-die deep drawing process.  The fracture surface and numerical results revealed that the material failed in a different mode for different strain path. Therefore, Tresca model which is based on shear stress accurately predicted the conditions where shear had the profound effect on the damage initiation, whereas Situ localized necking criterion was able to calculate the conditions which localization was dominant.

Sign in / Sign up

Export Citation Format

Share Document