Material models and crash simulations in LS-DYNA: Development of virtual test laboratory
Typ
Examensarbete för masterexamen
Program
Automotive engineering (MPAUT), MSc
Publicerad
2021
Författare
Rao Sudarshan, Mayur
Viswanath Shankar Rao, Sriharsha
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
Extensive developments in the field of computational mechanics led to substantial
improvements in the assessment of vehicles in a virtual environment. Vehicle safety
is one of the prime areas where virtual simulations are comprehensively used in the
product development phase. In order to obtain effective results, it is very important
that the material model predicts the failure behaviour accurately in crash analysis.
The main goal of the current study is to contribute to the development of a virtual
material test laboratory where different materials can be tested in multiple stress
states in LS-DYNA using a calibrated input flow curve (obtained from an uniaxial
tension test simulation).
The study was carried out in two phases. Initially, coupon tests were simulated using
solid fine elements which were finally validated against the experimental results
in order to achieve better accuracy. A input flow curve was calibrated from the uniaxial
tension test simulations using optimisation technique and the same curve was
finalized for all the further simulations. The same coupon tests were then simulated
using shell elements and a damage model (GISSMO) was coupled to a constitutive
material model, as damage models play an important role in predicting the fracture
in the material. Necessary information like triaxiality values, failure strain, and
critical strains computed from the solid element models was used to calibrate the
GISSMO model. The calibrated model was then subjected to mesh regularization
for element sizes varying from 0.5mm to 5mm to determine the sensitivity of mesh
size on failure prediction.
The calibrated material model for shells showed promising results and was in good
agreement with experiments and in a full scale Offset Deformable Barrier crash simulation.
The material model was computationally efficient and, using this methodology,
different stress states can be predicted quite effectively using a single flow
curve (derived from simple tension test). This methodology can also be verified for
other metals and polymers.
Beskrivning
Ämne/nyckelord
LS-DYNA , *MAT_024 , GISSMO , Optimisation , triaxiality , critical strain , failure strain , flow curve