Assessment of the von Mises stresses and stress triaxiality in notches using modified tensile specimens
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2022
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CONGRESSO BRASILEIRO DE ENGENHARIA E CIÊNCIA DOS MATERIAIS, 24.
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Resumo
Stress triaxiality is important in fracture mechanics to check the safety of several structures. Stress
triaxiality is one of the main factors that influence the fracture process of high toughness steels. For
example, a ductile fracture tends to be more predominant for a low constrain geometry with less
plastic restriction. The configuration and loading of the structural components are different from
those of the mechanical test specimens used to obtain the materials fracture properties. So,
understanding the local stress triaxiality is essential to ensure structural safety. Combination of
tests with numerical simulations is a way to assess this effect. Modifying the standard tensile test
geometry (ASTM E8) with a notch causes a change in the stress triaxiality. Based on the literature
information, two notches were chosen: 1 and 2 mm. These geometries were tested, and the results
were numerically reproduced using a non-linear model with the GTN damage model in the
software Abaqus/Explicit 2020. The properties (elastic and plastic) were obtained from the standard
specimen. An axisymmetric finite element model was developed considering the symmetry in the
specimen longitudinal direction, and a mesh with the smallest element having the dimensions of
0.2x0.4 mm. First, a test speed of 0.015 mm/s was applied in the specimen longitudinal direction
and convergence problems occurred. Thus, the speed was increased to 100 mm/s to solve these
problems. Finally, the nine GTN damage parameters were calibrated to describe numerically the
experimental curve. The stresses were obtained for the centroid of the elements. All the analyses
were done for two points, i.e.,. first is the plastic instability point for a standard specimen, and
second is the maximum force of the load vs. displacement curve. The numerical results analysis
allowed the assessment of the stress field and stress triaxiality near the notch to compare with the
standard specimen. The notch influences the stress locally, but, after a short distance,
approximately 45 mm in these specimens, the tendency was the same for three geometries. The
evaluation of the triaxiality considered the stress in the specimen longitudinal direction and the
hydrostatic stress. Before the point of plastic instability (first point), the stress triaxiality is low,
practically an uniaxial stress state. To the second point, the stress state is no longer uniaxial. The
notch increases the stress triaxiality across the cross-section, and the biggest value occurred in the
center of the specimen. These specimens results can help to identify the region affected by the
notches in structural components.
Como referenciar
PEREIRA, L.d.; DONATO, G.H.; MATTAR NETO, M. Assessment of the von Mises stresses and stress triaxiality in notches using modified tensile specimens. In: CONGRESSO BRASILEIRO DE ENGENHARIA E CIÊNCIA DOS MATERIAIS, 24., 6-10 de novembro, 2022, Águas de Lindóia, SP. Resumo... Disponível em: http://repositorio.ipen.br/handle/123456789/33786. Acesso em: 25 Mar 2025.
Esta referência é gerada automaticamente de acordo com as normas do estilo IPEN/SP (ABNT NBR 6023) e recomenda-se uma verificação final e ajustes caso necessário.