Global-Local Characterization and Numerical Modeling of TWB Laser Welded Joints

2017 ◽  
Author(s):  
F. Nalli ◽  
P. Russo Spena ◽  
L. Cortese ◽  
D. Reiterer
Keyword(s):  
Local Level ◽  
High Strength Steels ◽  
High Strength ◽  
Image Correlation ◽  
Correlation Technique ◽  
Fe Model ◽  
Base Metals ◽  
Displacement Fields ◽  
Advanced High Strength Steels ◽  
Tailor Welded Blanks

Sheet forming of tailor welded blanks (TWBs) of advanced high strength steels is complex because of the notable differences in mechanical properties, and hence in formability, of base metals, heat affected zones and weld seam. In this work, an accurate characterization of the mechanical behavior of these regions in TWBs made of a DP and TRIP steel was carried out. Micro-samples, machined from base metals and fusion zone were employed to retrieve the local constitutive laws up to fracture. At the same time, macro-samples, extracted throughout the welded joint were tested to assess the weldment overall behavior. Along with global load-displacement data, strain and displacement fields of the joint were evaluated, using a Digital Image Correlation technique. An FE simulation of the entire joint was setup, using the previously identified material properties. In a comparison between the FE model and experiments, good results were obtained both at a global and local level, up to fracture.

Temperature Increase in Forming of Advanced High-Strength Steels Effect of Ram Speed Using a Servodrive Press

2016 ◽  
Vol 138 (9) ◽  
Author(s):  
Ali Fallahiarezoodar ◽  
Ruzgar Peker ◽  
Taylan Altan
Keyword(s):  
Process Design ◽  
Temperature Increase ◽  
High Strength Steels ◽  
High Strength ◽  
Design Stage ◽  
Interface Temperature ◽  
Fe Model ◽  
Advanced High Strength Steels ◽  
The Coefficient Of Friction ◽  
Ram Speed

In forming of advanced high-strength steel (AHSS), the temperature increase at die/sheet interface affects the performance of lubricants and die wear. This study demonstrates that finite-element (FE) analysis, using commercially available software, can be used to estimate temperature increase in single as well as in multiple stroke operations. To obtain a reliable numerical process design, the knowledge of the thermal and mechanical properties of the sheet as well as the tools is essential. Using U-channel drawing the thermomechanical FE model has been validated by comparing predictions with experimental results. The effect of ram speed and stroking rate (stroke per minute (SPM)) upon temperature increase in real productionlike operation have been investigated. Deep drawing of CP800 and DP590 sheets in a servodrive press, using an industrial scale die, has been studied. Thinning distribution and temperatures in the drawn part have been investigated in single and multiple forming operations. It is found that temperatures may reach several 100 deg and affect the coefficient of friction (COF). The values of COF under productionlike conditions were compared to that obtained from laboratory experiments. This study illustrates that in forming AHSS, (a) the temperature increase at the die/sheet interface is relatively high and should be considered in process design stage, and (b) the lubricant performance is significantly affected by the ram speed and sheet/die interface temperature during deformation.

Finite Element Modeling of Deformation Behavior of Steel Specimens under Various Loading Scenarios

2015 ◽  
Vol 651-653 ◽  
pp. 969-974 ◽  
Author(s):  
Dilip Banerjee ◽  
Mark Iadicola ◽  
Adam Creuziger ◽  
Tim Foecke
Keyword(s):  
Finite Element ◽  
Deformation Behavior ◽  
Stress Measurement ◽  
High Strength Steels ◽  
High Strength ◽  
Tensile Tests ◽  
Image Correlation ◽  
Uniaxial Tensile ◽  
Fe Model ◽  
Strain Paths

Lightweighting materials (e.g., advanced high strength steels, aluminum alloys etc.) are increasingly being used by automotive companies as sheet metal components. However, accurate material models are needed for wider adoption. These constitutive material data are often developed by applying biaxial strain paths with cross-shaped (cruciform) specimens. Optimizing the design of specimens is a major goal in which finite element (FE) analysis can play a major role. However, verification of FE models is necessary. Calibrating models against uniaxial tensile tests is a logical first step. In the present study, reliable stress-strain data up to failure are developed by using digital image correlation (DIC) technique for strain measurement and X-ray techniques and/or force data for stress measurement. Such data are used to model the deformation behavior in uniaxial and biaxial tensile specimens. Model predictions of strains and displacements are compared with experimental data. The role of imperfections on necking behavior in FE modeling results of uniaxial tests is discussed. Computed results of deformation, strain profile, and von Mises plastic strain agree with measured values along critical paths in the cruciform specimens. Such a calibrated FE model can be used to obtain an optimum cruciform specimen design.

Effects of Weld Line in Deep Drawing of Tailor Welded Blanks of High Strength Steels

2014 ◽  
Vol 611-612 ◽  
pp. 955-962 ◽  
Author(s):  
Thomas Mennecart ◽  
Alper Güner ◽  
Nooman Ben Khalifa ◽  
A. Erman Tekkaya
Keyword(s):  
Deep Drawing ◽  
Applied Load ◽  
Lightweight Design ◽  
Weld Line ◽  
Base Material ◽  
High Strength Steels ◽  
High Strength ◽  
Fe Model ◽  
Tailor Welded Blanks ◽  
Base Materials

Due to the increase of lightweight design in car bodies, there is a raise in use of tailored welded blanks (TWB). With these blanks it is possible to strengthen the car body where it is necessary. This can lead to less weight. In the case of tailored welded blanks, there is a weld line, which influences the deep drawing behavior significantly during forming. In the presented results two different high strength steels (HCT980X and HCT600X) are welded together. One forming operation is performed, in which the weld line is positioned differently. The results show the influence of the weld line on the forming behavior which is realized by the comparison of deep drawn monolithic parts with the deep drawn tailored welded blanks. While the monolithic parts could be formed without failure, the forming of tailored welded blanks was accompanied by cracks in dependency to the weld line orientation and the applied load in this region. The results also show that the failure occurs in the base material and that the weld line is not damaged by the applied load. After the characterization of the base materials and the weld material, a numerical modelling of the whole TWB could be realized in this work. Two different ways of modelling techniques of the weld line are compared and the necessity of the consideration of the weld line properties is demonstrated. Furthermore, in consideration of the weld line properties in the FE-Model, it is possible to show that the weld line resists the forming operation without failure.

Numerical modeling of stress-strain relationships for advanced high strength steels

2021 ◽  
Vol 182 ◽  
pp. 106687
Author(s):  
Yu Xia ◽  
Chu Ding ◽  
Zhanjie Li ◽  
Benjamin W. Schafer ◽  
Hannah B. Blum
Keyword(s):  
Numerical Modeling ◽  
High Strength Steels ◽  
High Strength ◽  
Stress Strain ◽  
Advanced High Strength Steels
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