A1 Journal article (refereed), original research

Use of the quasi-static Johnson-Cook model in the failure assessment of tensile specimens with metallurgical constraints

Open Access publication

Publication Details
Authors: Neuvonen Riku, Skriko Tuomas, Björk Timo
Publisher: Elsevier
Publication year: 2020
Language: English
Related Journal or Series Information: European Journal of Mechanics A: Solids
Volume number: 82
ISSN: 0997-7538
eISSN: 1873-7285
JUFO-Level of this publication: 2
Open Access: Open Access publication
Location of the parallel saved publication: http://urn.fi/URN:NBN:fi-fe2020051435618


Direct quenching has recently been used to develop cost-effective novel
high and ultra-high strength steels. In weldments made of these steels, a
distinct soft zone, which can lower the ultimate strength and
deformation capacity of the welded joint, can form in the heat affected
zone of the joint. In order to accurately estimate the static strength
and deformation capacity of a welded steel structure fabricated from
these steels, the effect of this softening must be taken into account.
In this study, the effect of the softened zone is explored based on
round tensile test specimens with metallurgical constraints using
experiments and numerical calculations. The applicability of the
quasi-static part of the Johnson-Cook material model and failure model
for fracture assessment under given conditions was hereby examined.
Firstly, the material parameters were determined for direct-quenched
armor steel and cold-formed structural steel using notched tensile test
specimens and FE models combined with an optimization routine. A good
agreement was achieved between the tests and the results from the FE
models for the notched specimens. Specimens with metallurgical
constraints were manufactured from the materials using rotational
friction welding, and the corresponding FE models were created using the
material parameters obtained from optimization. Two different fracture
mechanisms were observed in the tensile tests conducted for the
specimens with metallurgical constraints, namely cup and cone fractures
at the center of the specimen and fractures near the weld interface. In
the corresponding FE models, the fracture initiations were observed in
the same areas. A good agreement between the FE models and experimental
tensile tests was thus achieved in the case of the cup and cone
fractures. However, the generated FE models underestimated the fracture
displacement in the specimens where the fracture occurred near the weld

Last updated on 2020-05-06 at 08:01