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.

Formability and Weld Zone Analysis of Tailor-Welded Blanks for Various Thickness Ratios

2005 ◽  
Vol 127 (2) ◽  
pp. 179-185 ◽  
Author(s):  
L. C. Chan ◽  
S. M. Chan ◽  
C. H. Cheng ◽  
T. C. Lee
Keyword(s):  
Fusion Zone ◽  
Base Metal ◽  
Mechanical Characteristics ◽  
Thickness Ratio ◽  
Microhardness Measurement ◽  
Forming Limit ◽  
Uniaxial Tensile ◽  
Metallographic Study ◽  
Major Strain ◽  
Tailor Welded Blanks

Cold-rolled steel sheets of thicknesses ranging from 0.5 to 1.0 mm were used to produce tailor-welded blanks (TWBs) with various thickness ratios. In this study, the formability of the TWBs, as well as the mechanical characteristics of the weld zones, were analyzed experimentally under the effects of various thickness ratios of TWBs. The formability of the TWBs was evaluated in terms of three measures—failure mode, forming limit diagram, and minimum major strain, whereas the mechanical characteristics of the weld zones were investigated by tensile testing, metallographic study, and microhardness measurement. In particular, circular TWBs with different radii and cutoff widths were designed where all the welds were located in the center of the blanks and perpendicular to the principal strain direction. Nd:YAG laser butt-welding was used to weld the TWB specimens of different thickness ratios. The experimental findings in this study showed that the higher the thickness ratio of the TWBs, the lower the forming limit curve level, and the lower formability. The minimum major strain was clearly inversely proportional to the thickness ratio of the TWBs. On the other hand, the results of uniaxial tensile tests clearly illustrated that there was no significant difference between the tensile strengths of the TWBs and those of the base metals. The metallographic study demonstrated a difference of grain size in the materials at base metal, heat-affected zones, and fusion zone. The microhardness measurement indicated that the hardness in the fusion zone increased by about 60% of the base metal.

An innovation in finite element simulation via crystal plasticity assessment of grain morphology effect on sheet metal formability

2021 ◽  
pp. 146442072110246
Author(s):  
Mostafa Habibi ◽  
Roya Darabi ◽  
Jose C de Sa ◽  
Ana Reis
Keyword(s):  
Finite Element ◽  
Tensile Test ◽  
Crystal Plasticity ◽  
Forming Limit Diagram ◽  
Material Behavior ◽  
Forming Limit ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Polycrystal Plasticity ◽  
Grain Distribution

Experimental and numerical study regarding the uniaxial tensile test and the forming limit diagram are addressed in this paper for AL2024 with the face-centered cube structure. First, representation of a grain structure can be obtained directly by mapping metallographic observations via scanning electron microscopy approach. Artificial grain microstructures produced by Voronoi Tessellation method are employed in the model using VGRAIN software. By resorting to the finite element software (ABAQUS) capabilities, the constitutive equations of the crystal plasticity were utilized and implemented as a user subroutine material UMAT code. The hardening parameters were calibrated by a trial and error approach in order to fit experimental tensile results with the simulation. Then the effect of the changing grain size, the heterogeneity factor, and the grain aspect ratio were studied for a uniaxial tensile test to emphasize the importance of the microstudy behavior of grains in material behavior. Furthermore, the polycrystal plasticity grain distribution was employed in the Nakazima test in order to obtain the forming limit diagram. The crystal plasticity-driven forming limit diagram reveals more accurate strains, taking into account the involving the micromechanical features of the grains. An innovative approach is pursued in this study to discover the necking angle, both in tensile test or Nakazima samples, showing a good agreement with the experiment results.

Study on Formability of Tailor Welded Blanks Based on Numerical Simulation

2011 ◽  
Vol 704-705 ◽  
pp. 45-49 ◽  
Author(s):  
Wen Liu ◽  
Shui Sheng Xie ◽  
Ji Qiang Li ◽  
Xu Ding
Keyword(s):  
Weld Seam ◽  
Thickness Ratio ◽  
Forming Limit ◽  
Strength Ratio ◽  
Tailor Welded Blanks ◽  
Numeric Simulation ◽  
Strength Material ◽  
The Difference ◽  
Different Thickness ◽  
Square Box

The strength ratio, thickness ration of blanks and the microstructure of weld seam play important role in the formability of tailor welded blanks (TWB). With numeric simulation technology in different conditions such as different thickness and different strength combination of TWB’s materials, the forming limit depth (FLD) of tailor welded blanks is analyzed. The affect of the thickness ratio and strength ratio on forming limit depth is investigated, the laws influencing the formability of TWB square box are summarized, and approaches are presented to increase the FLD. The results of simulation and practice indicate that reducing the difference of the thickness ratio, choosing lower strength material for thicker blank, and adopting right heat treatment can improve the forming limit depth. Keywords: Tailor Welded Blanks; Forming Limit Depth; Thickness Ratio; Strength Ratio

scholarly journals Forming limit diagram prediction of 6061 aluminum by GTN damage model

2018 ◽  
Vol 19 (2) ◽  
pp. 202 ◽  
Author(s):  
Rasoul Safdarian
Keyword(s):  
Damage Model ◽  
Forming Limit Diagram ◽  
Numerical Results ◽  
Experimental Results ◽  
Correct Selection ◽  
Forming Limit ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Gtn Model ◽  
Gtn Damage Model

Forming limit diagram (FLD) is one of the formability criteria which is a plot of major strain versus minor strain. In the present study, Gurson-Tvergaard-Needleman (GTN) model is used for FLD prediction of aluminum alloy 6061. Whereas correct selection of GTN parameters’ is effective in the accuracy of this model, anti-inference method and numerical simulation of the uniaxial tensile test is used for identification of GTN parameters. Proper parameters of GTN model is imported to the finite element analysis of Nakazima test for FLD prediction. Whereas FLD is dependent on forming history and strain path, forming limit stress diagram (FLSD) based on the GTN damage model is also used for forming limit prediction in the numerical method. Numerical results for FLD, FLSD and punch’s load-displacement are compared with experimental results. Results show that there is a good agreement between the numerical and experimental results. The main drawback of numerical results for prediction of the right-hand side of FLD which was concluded in other researchers’ studies was solved in the present study by using GTN damage model.

A comparative study of forming limit diagram prediction of tailor welded blanks

2014 ◽  
Vol 8 (2) ◽  
pp. 293-304 ◽  
Author(s):  
R. Safdarian ◽  
R. M. Natal Jorge ◽  
Abel D. Santos ◽  
H. Moslemi Naeini ◽  
M. P. L. Parente
Keyword(s):  
Comparative Study ◽  
Forming Limit Diagram ◽  
Forming Limit ◽  
Tailor Welded Blanks

Comparison of different welding methods on mechanical properties and formability behaviors of tailor welded blanks (TWB) made from AA6061 alloys

2020 ◽  
pp. 095440622095250
Author(s):  
Behrouz Bagheri ◽  
Mahmoud Abbasi ◽  
Reza Hamzeloo
Keyword(s):  
Mechanical Properties ◽  
Laser Welding ◽  
Co2 Laser ◽  
Forming Limit Diagram ◽  
Dome Height ◽  
Forming Limit ◽  
Welding Parameters ◽  
Friction Stir ◽  
Tailor Welded Blanks ◽  
Different Characteristics

A tailor welded blank (TWB) includes two or more blanks joined together in order to make a single blank. Different welding methods are used to join blanks with different characteristics and form TWBs. In this study, a comparison is made among the effects of three different welding methods namely CO2 laser welding, friction stir welding (FSW), and friction stir vibration welding (FSVW) on mechanical and formability properties of developed TWBs. AA6061 alloy sheets with different thicknesses (1.2 and 0.8 mm) are joined to get TWBs. The forming limit diagram (FLD) and limiting dome height (LDH) are applied to assess the formability. The Taguchi method is applied to find the optimum values of welding parameters. It is concluded that TWBs made by FSVW have higher mechanical properties and formability compared to TWBs made by FSW and CO2 laser welding. The results also indicate that FLD for TWBs made by FSW is higher than FLD for TWBs made by CO2 laser welding and FLD0, for TWBs made by FSVW, increases as vibration frequency increases.

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.

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.

A Suitable Criterion for Precise Determination of Incipient Necking in Sheet Materials

2006 ◽  
Vol 519-521 ◽  
pp. 111-116 ◽  
Author(s):  
Q. Situ ◽  
Mukesh K. Jain ◽  
M. Bruhis
Keyword(s):  
Strain Rate ◽  
Sheet Material ◽  
Forming Limit Diagram ◽  
Precise Determination ◽  
Forming Limit ◽  
Strain History ◽  
Flow Localization ◽  
Major Strain ◽  
Strain Paths

Forming limit diagram (FLD) is a measure of the formability of a sheet material. The major-minor strain pairs that are closest to the neck on multiple specimens of various strain paths are utilized to construct a boundary between safe and unsafe zones. The challenge to obtain the FLD is the determination of incipient necking. Three approaches to determine the limit strains have been investigated and compared in this research in order to establish the optimal one for implementation: (1) commonly used Bragard criterion ( 1)e Br with periodic grids; (2) tracking the region of large local strains from strain history to locate the instance when critical major strain ( 1)e cr happens; (3) post-processing of strain history to locate the inflection in the major strain rate curve 1 max (e&&) at the onset of localization. The last criterion of inflection in strain rate 1 max (e&&) carries both a numerical and a physical meaning towards developing an understanding of flow localization, formability and fracture.

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