Stretch-flange-formability is an important property for ultra high strength steel (UHSS) sheets for press-forming. In this study, microscopic deformation behaviors during punching and following stretch-flange-forming were investigated using three types of 980 MPa grade UHSS sheets with either two ferrite/martensite dual-phase structures or a martensite single-phase structure in order to clarify how
(PDF) On the interplay of friction and stress relaxation On the interplay of friction and stress relaxation to improve stretch-flangeability of dual phase (DP600) steel December 2020 CIRP Journal of Manufacturing Science and Technology 32
The hole expansion test were conducted to evaluate stretch-flangeability. An Ultra Micro-Indentation System (UMIS) were employed to carry out the nano-hardness test to check the nano-hardness of
Development of Methodology with Excellent Reproducibility Stretch-flangeability is an important formability factor for advanced high-strength steels (AHSS) when manufacturing automotive parts. However, the reproducibility of the hole expansion test (HET), a standard testing method established by the international organization for standardization, is quite poor compared with other mechanical testing methods.
Evaluation of stretch flangeability of dual-phase steels Mar 10, 2021 · In this study, investigations on stretch flangeability were carried out on as-received DP 600 steel which had 22 volume % of martensite. Stretch flangeability is normally characterized by the hole expansion test and refers to the ability to avoid cracking during stretch flanging or hole expansion. Two intercritical annealing treatments (soaking temperatures of 760 °C and 800 °C followed by
The stretch flangeability of an ultra-high strength steel sheet having low ductility was improved by smoothing the sheared edge of the sheet.
Improvement of Fatigue Strength of Hole Edge of Ultra-High To increase both the bending and tensile fatigue strengths, a compressive process in rollover of hole edge was added for the thickened sheet having a high bending fatigue strength. It was found that the thickened and compressed hole edge of ultra-high strength steel sheet was effective in improving both the bending and tensile fatigue strengths.
Influence of curvature variation on edge stretchability in Mori K, Abe Y, Suzui Y (2010) Improvement of stretch flangeability of ultra high strength steel sheet by smoothing of sheared edge. J Mater Process Technol 210(4):653659 CrossRef Google Scholar 3.
the r-value of high strength steels is generally less than 1.0, other controlling factors become important. Although stretch flangeability is also known to decrease with increasing the strength, the effect of microscale uniformity is noticeable. The more uniform the micro-structure, the better stretch flangeability can be obtained. It is, there-Gradually contacting punch for improving stretch
Improvement of Stretch Flangeability of High-Tensile Apr 08, 2013 · Thus the authors have conducted a study to improve the stretch flangeability of high-tensile-strength steel sheets by optimizing the punching method and obtained the following conclusion. Work hardening beneath the pierced edge is mainly caused by deformation due to the punch motion while it is shearing the material.