Banca de DEFESA: FELIPE FERNANDES CAVALCANTE

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : FELIPE FERNANDES CAVALCANTE
DATE: 30/10/2026
TIME: 08:30
LOCAL: Sala de aula LIME
TITLE:

Effects of cutting-edge processing conditions on the flangeability of thin FB 580 steel sheets

KEY WORDS:

advanced high strength steels (AHSS); FB580 steel; punching; conical hole expansion; cryogenics; localized deformation

PAGES: 96
BIG AREA: Engenharias
AREA: Engenharia de Materiais e Metalúrgica
SUMMARY:

The automotive industry widely uses Advanced High-Strength Steels (AHSS) in the manufacturing of vehicular structures, combining weight reduction with compliance to stringent safety standards. However, the presence of high-hardness microconstituents in these materials favors the nucleation of cracks and defects at the sheared edges during the stamping process, significantly limiting the stretching capacity (flangeability) in subsequent forming stages. Faced with this challenge, the main objective of this study is to increase the flangeability of the FB580 ferritic-bainitic steel by investigating two distinct sheared edge processing routes: a thermal route, through punching under cryogenic conditions using liquid nitrogen (LN2), and a mechanical route, based on the application of plastic deformation to the fracture zone of the sheared edge. The methodology encompassed the geometric quantification of the sheared zones, the evaluation of mechanical performance through the hole expansion test (ISO 16630), and fractographic analysis via Scanning Electron Microscopy (SEM), Electron Backscatter Diffraction (EBSD), and hardness mapping in layers adjacent to the edge. The results demonstrated that cryogenic punching altered the edge profile—reducing the shear zone and increasing the fracture zone—but promoted only a marginal gain that was statistically similar to room-temperature punching in the hole expansion test, not justifying its implementation in production lines. In contrast, the mechanical route resulted in a significant increase in the hole expansion ratio (HER), which jumped from 85.0% in the control condition to 107.4% with 70% deformation of the fracture zone, reaching 125.4% under the condition of total deformation of this zone. Fractographic analysis showed that, while samples punched at room temperature fail preferentially in the rolling direction due to the influence of residual stresses in the as-received sheet, localized deformation eliminates this anisotropy. The imposed plastic deformation promoted a circular and symmetric homogenization of the edge work hardening, inhibiting preferential sites for crack nucleation. It is therefore concluded that the application of localized deformation to the sheared edge constitutes a robust edge engineering strategy, capable of modifying crack nucleation and propagation mechanisms, with a direct impact on the industrial applicability of ferritic-bainitic AHSS.

COMMITTEE MEMBERS:
Presidente - 2550377 - THERCIO HENRIQUE DE CARVALHO COSTA
Externo ao Programa - 1792669 - ADILSON JOSÉ DE OLIVEIRA - UFRNExterno ao Programa - 1938946 - NICOLAU APOENA CASTRO - UFRNExterno à Instituição - JETSON LEMOS FERREIRA - Arcelor
Externo à Instituição - JORGE MAGNER LOURENÇO - IFRN