Banca de QUALIFICAÇÃO: FELIPE FERNANDES CAVALCANTE

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
STUDENT : FELIPE FERNANDES CAVALCANTE
DATE: 27/04/2026
TIME: 09:00
LOCAL: Sala de reuniões do LIME (UFRN)
TITLE:

INFLUENCE OF CRYOGENIC PUNCHING AND LOCALIZED PLASTIC DEFORMATION ON DAMAGE EVOLUTION AND FLANGEABILITY OF FB580 FERRITIC-BAINITIC STEEL

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 has widely employed Advanced High-Strength Steels (AHSS) to reduce vehicle weight and meet strict safety requirements. However, the presence of high hardness microconstituents in these materials favors crack nucleation at the cut edges during the punching process, severely limiting the stretchability (flangeability) in subsequent forming stages. Faced with this challenge, the main objective of this work 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 localized plastic deformation at the cut edge.The methodology encompassed the geometric quantification of the cut zones, the evaluation of mechanical performance through the hole expansion test (ISO 16630), and fractographic analysis via Scanning Electron Microscopy (SEM). 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, statistically similar to room temperature cutting 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% in 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 from the as-received sheet condition, localized deformation eliminates this anisotropy. The imposed plastic deformation promoted a circular and symmetrical homogenization of the edge work hardening, inhibiting preferential crack nucleation sites.It is concluded, therefore, that the application of localized deformation on the sheared edge configures 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
Interno - 2266607 - FABIO JOSE PINHEIRO SOUSA
Externo ao Programa - 1792669 - ADILSON JOSÉ DE OLIVEIRA - UFRNExterno ao Programa - 1938946 - NICOLAU APOENA CASTRO - UFRNExterno à Instituição - JETSON LEMOS FERREIRA - Arcelor