Analysis of two parameter identification methods for original and modified Johnson-Cook fracture strains, including numerical comparison and validation of a new blue-brittle dependent fracture model for free-cutting Steel 50SiB8
OPEN ACCESS
Loading...
Author / Producer
Date
2021-04
Publication Type
Journal Article
ETH Bibliography
yes
Citations
Altmetric
OPEN ACCESS
Data
Abstract
A non-linear relation between fracture strain and temperature is observed in Split Hopkinson Tension Bar (SHTB) tests for free-cutting steel 50SiB8 at high strains and high temperatures, due to blue-brittleness. A fourth-degree polynomial function for the thermal parts of the original and modified Johnson-Cook (JC) fracture strain constitutive equation is suggested and the corresponding parameters are identified. Fracture modelling of 50SiB8 is not reported in literature. 50SiB8 is characterized under quasi-static, isothermal, high temperature and high strain rate conditions using smooth and notched tension specimens. For the calculation of the original and modified JC fracture parameters, two different parameter identification procedures, so-called forward and backward parameter identification methods are performed, compared with each other and explained in detail. For the stress triaxiality factor of the original and modified JC fracture model, the forward parameter identification method is suggested for the original JC fracture model, while backward parameter identification method is proposed for the modified JC fracture model. The effect of blue-brittleness in the temperature factor and the corresponding parameters are presented. Furthermore, FEM simulations of the original and the blue-brittleness including JC fracture model are compared with experiments. In the blue-brittle temperature range, the new adjusted JC model shows more accurate results, regarding fracture diameter and strain. Additionally, this work introduces a fracture model combining the Bai-Wierzbicki stress triaxiality dependent model, JC fracture models and the nonlinear temperature factor with blue-brittleness effect, while further experiments are required in order to determine its parameters.
Permanent link
Publication status
published
External links
Editor
Book title
Journal / series
Volume
112
Pages / Article No.
102905
Publisher
Elsevier
Event
Edition / version
Methods
Software
Geographic location
Date collected
Date created
Subject
Forward and Backward Parameter Identification Methods; Fracture; Constitutive behaviour; Rate-dependent material; Kolsky bar; blue-brittleness fracture model; FE simulations
Organisational unit
03641 - Wegener, Konrad (emeritus) / Wegener, Konrad (emeritus)
02623 - Inst. f. Werkzeugmaschinen und Fertigung / Inst. Machine Tools and Manufacturing