This book is intended to be a companion to the NAFEMS book, "An Introduction to the Use of Material Models in FE". It informs Finite Element Analysis users of the manner and methodologies by which materials are tested in order to calibrate material models currently implemented in various FEA programs. While the authors seek first to satisfy the basic material models outlined in the companion book, they make important extensions to FEA used in currently active areas including explicit simulation.
Focus on Validation of Simulation: CAETestBench Validation for crash, additive manufacturing, injection molding, rubber hyperelasticity; Review of NAFEMS publication on V&V.
"Reliable prediction of damage and failure in structural parts is a major challenge posed
in engineering mechanics. Although solid material models predicting the deformation
behaviour of a structure are increasingly available, reliable prediction of failure remains
still open.
With SAMP (a Semi-Analytical Model for Polymers), a general and flexible plasticity
model is available in LS-DYNA since version 971. Although originally developed for
plastics, the plasticity formulation in SAMP is generally applicable to materials that
exhibit permanent deformation, such as thermoplastics, crushable foam, soil and metals.
In this paper, we present a generalized damage and failure procedure that has been implemented
in SAMP and will be available in LS-DYNA soon. In particular, important
effects such as triaxiality, strain rate dependency, regularization and non-proportional
loading are considered in SAMP. All required physical material parameters are provided
in a user-friendly tabulated way. It is shown that our formalism includes many different
damage and failure models as special cases, such as the well-known formulations by
Johnson-Cook, Chaboche, Lemaitre and Gurson among others. "
Quantifying simulation accuracy before running crash simulations could be a helpful confidence building measure. This study continues our development of a mechanism to validate material models for plastics used in modeling high-speed impact. Focusing on models for isotropic materials that include options for rate dependency and failure, we explore other models commonly used for ductile plastics including MAT089 and MAT187.
High strain rate material modelling of polymers for use in crash and drop testing has been plagued by a number of problems. These include poor quality and noisy data, material models unsuited to polymer behaviour and unclear material model calibration guidelines. The modelling of polymers is thus a risky proposition with a highly variable success rate. In previous work, we tackled each of the above problems individually. In this paper, we summarize and then proceed to present a material modelling strategy that can be applied for a wide variety of polymers.
Verification and Validation Are Focus of Technical Presentations at CAE Events, New Multi-CAE TestPaks® Deliver Data for Injection Molding and Crash Simulations,
High strain-rate properties have many applications in the simulation of automotive crash and product drop testing.
These properties are difficult to measure. These difficulties result from inaccuracies in extensometry at high strain
rates due to extensometer slippage and background noise due to the sudden increase in stress at the start of the
test. To eliminate these inaccuracies we use an inferential technique that correlates strain to extension at low
strain rates and show that this can be extended to measure strain at higher strain rates
Plastics appeared as design materials of choice about 30 years ago. They brought with them huge design challenges because their multi-variable, non-linear nature was not well understood by engineers trained to work in a linear elastic world. We outline a 20 year journey accompanying our customers in their efforts to understand and simulate these remarkable materials to produce the highly reliable plastic products of today. We discuss challenges related to processes such as injection molding vs. blow-molding; coping with filled plastics; the difficulties of modeling polymers for crash applications. We include our latest findings related to volumetric yield in polymers and its relationship to failure. We describe the material database technology that was created to store this kind of multi-variable data and the analytical tools created to help the CAE engineer understand and use plastics material data.
