In this research, three-layered composite of brass-IF steel-brass was fabricated by cold roll bonding process (CRB) and formability of composite were investigated. Finally, using the results of this research and identifying the properties of the sheet such as yield strengths, anisotropy coefficients, and selecting proper yield criterion, the FLD of different sheets theoretically can be determined precisely. The results illustrate that if critical material parameters such as imperfection factors and the yield criterion coefficients are defined correctly, the Marciniak–Kuczynski (M–K) model is capable of predicting the FLD of high anisotropic sheet metals with acceptable accuracy. Experimental strain diagrams are obtained in three directions with respect to the rolling direction. The error function is optimized and limit strains are calculated using the obtained yield criterion coefficients. The yield stress relationships are obtained under the plane strain conditions and implemented to the error function. Afterward, an appropriate error function is defined and optimized using a Genetic Algorithm. Consequently, directional yield stresses and anisotropy coefficients were extracted. To obtain and calibrate the BBC advanced yield criteria, tensile tests were performed in seven directions at angles of 0°, 15°, 30°, 45°, 60°, 75°, and 90° with respect to the rolling direction. In this research, theoretical and experimental methods are applied to obtain FLDs of the Aluminum Alloy 5083 (AA5083) sheet to investigate the formability behavior of this material, considering the strain hardening effects on the sheet. In sheet metal forming, prediction of the material behavior during the forming process conditions to obtain the forming limit diagram (FLD) is of great importance.
GRIDDED CIRCLE ISO
Finally, conducting the case studies, it was concluded that ISO 12004 2 yields most reliable and reproducible results than the ASTM standard. The Nakajima specimens formed with the two standards showed different failure mechanisms. Failure mechanisms were inspected for further investigation. In order to test the validity and the reliability of the method, limit strains on the same specimens were also determined with using a real time measurement method for the ISO experiments and the results reveal that the method is reliable. Since the same strain evaluation method should be used for the standards so as to be able to investigate the effect of only standards, a simple method in computer grid analysis system was used. The effects of specimen’s geometry, lubrication condition, and determination methods of limit strains on FLCs were considered and compared. The comparison was made for two materials which have moderate brittle and ductile characteristics, AA2024 T4 and AA5754-O alloys respectively. In this study, experimental studies were conducted to evaluate the differences of the ASTM E 2218-02 and ISO 12004 2 standards that are used for construction of forming limit curve (FLC) and that made various assumptions which create dissimilar FLCs for the same material. In addition, the initial orientation of sheets had none effect on FSW process. Also, it was revealed that welding caused formability decrease, and in TWBs with different thicknesses, this negative effect was higher.
The welding process was carried out in rolling and transverse directions with no effect on formability, and then the welding process was performed in the principal stress direction and perpendicular to it these directions had a significant effect on formability. The effect of welding seam directions on formability and FLD were investigated concerning two aspects. The tensile test, micro hardness testing, and metallographic studies were done. The welded zone properties were evaluated by some experiments.
This study was performed on low carbon steel (St14) sheets with a lot of applications in automobile industries. The formability and FLDs of TWBs were evaluated for sheets with the same or different thicknesses and compared to the base metal sheet. At first, the suitable FSW parameters were achieved. In this study, the mechanical properties, formability and forming limit diagrams (FLDs) of the tailor-welded blanks (TWBs) produced by friction stir welding (FSW) were analyzed experimentally.
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