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A CDM-based unified viscoplastic constitutive model of FLCs and FFLCs for boron steel under hot stamping conditions
- Publication Year :
- 2022
- Publisher :
- SAGE Publications, 2022.
-
Abstract
- Forming limit curves (FLCs), which are constructed using the limit strains at localised necking, are the most widely used tools for the evaluation of the formability of sheet metals. Fracture forming limit curves (FFLCs) are more recently developed, complementary tools for formability evaluation which are instead constructed using the limit strains at fracture. Since the formability depends strongly on forming conditions such as strain state, temperature and strain rate, models for predicting FLCs and FFLCs are essential for the optimisation and further application of hot forming processes in which these forming conditions vary significantly with both position and time. However, no model has so far been developed to predict FFLCs either alone or in conjunction with FLCs for sheet metals such as boron steel under hot stamping conditions. In this study, a set of unified viscoplastic constitutive equations for the prediction of both FLCs and FFLCs based on continuum damage mechanics (CDM) has been formulated from a set of recently developed constitutive equations for dislocation-based hardening, in combination with two novel coupled variables characterising the accumulated damage leading to localised necking and fracture. The novel variables take into account the effects of strain state, temperature and strain rate on the formability of sheet metals. The material constants in the CDM-based constitutive equations have been calibrated using experimental data comprising true stress-true strain curves and limit strains of a 22MnB5 boron steel obtained at a range of temperatures and strain rates. Investigation of the effect of varying selected parameters in the coupled damage variables on the resulting computed FLCs and FFLCs has demonstrated the flexibility of the model in enabling curves of different shapes and numerical values to be constructed. This indicates the potential of the CDM-based constitutive model for application to other materials for warm or hot stamping processes.
- Subjects :
- Technology
NOTCHED TENSION BARS
Materials Science
Computational Mechanics
sheet metal forming
constitutive modelling
Materials Science, Multidisciplinary
hot stamping
Mechanics
SHEET-METALS
FORMABILITY LIMITS
0905 Civil Engineering
FORMING LIMIT DIAGRAMS
continuum damage mechanics
Mechanical Engineering & Transports
General Materials Science
0912 Materials Engineering
STRESS TRIAXIALITY
Forming limit curve
ELEVATED-TEMPERATURES
STRAIN-RATE
Science & Technology
Mechanical Engineering
MICROSTRUCTURE EVOLUTION
BIAXIAL TESTING SYSTEM
boron steel
Mechanics of Materials
fracture forming limit curve
DUCTILE FRACTURE
0913 Mechanical Engineering
Subjects
Details
- Language :
- English
- Database :
- OpenAIRE
- Accession number :
- edsair.doi.dedup.....74d68f6bde98042c21f0adbf6704eb1b