Finite element analysis contains assumptions and uncertainty from a number of sources, which can impact the fidelity of the simulation. This uncertainty is often left untested up to prototyping stages. DatapointLabs’ CAETestbench Validation service was developed to add a mid-stage validation step to a designer’s workflow, to test these simulations before parts are made, in order to build confidence in an engineer’s model beforehand. This validation step is illustrated in a 3D printing application.
[We] introduced the topic of injection molding process simulation and the influence of the manufacturing process on structural analysis. The strength and stiffness of a part can be inaccurately represented if the manufacturing process conditions are not properly considered. This results in a different calculation of system natural frequencies or improper estimation of the energy absorbing characteristics. We continue on this topic, extending the scope to advanced technologies available in the Altair Partner Alliance (APA) to help solve the problem of proper design validation with fiber reinforced plastics.
With the growing interest in additive manufacturing in the aerospace industry, there is a desire to accurately simulate the behavior of components made by this process. The layer by layer print process appears to create a morphology that is different from that from conventional manufacturing processes. This can have dramatic impact on the material properties, which in turn, can affect how the material is modeled in simulation. We tested an additively manufactured metal part for mechanical properties and validated the material model used in a linear static simulation.
The airbag door system is one of the most delicate aspects in the design phase of a car instrument panel: seamless systems are increasingly used, which combine styling criteria with good functional performances. These systems typically include a tear seam, which may be obtained through laser scoring, to pre-determine the location of the opening during airbag deployment. The design of the scoring line is currently validated through experimental tests on real life exemplars, submitted to airbag deployment, resulting in high development times and relevant costs. This is the main reason which suggests proposing numerical simulation in the design phase, not to substitute actual part homologation by testing but in order to limit the scope and complexity of the experimental campaign, thus reducing the development costs and the time to market. So far, modeling the scoring line has been difficult due to limitations in the testing methods and simulation codes available to the industry. The methodology proposed in this paper takes advantage from the availability of a material law as LS-Dyna SAMP-1, with polymer-dedicated plasticity, damage model and strain-rate dependent failure criteria, which is supported by local strain measurement used for material characterization. The method, here described in detail, is validated on a benchmark test, consisting in the real and virtual testing on a variety of scoring profiles obtained on a polypropylene box submitted to high speed impact test.
Notwithstanding the increasing demand for polymeric materials in an
extraordinary variety of applications, the engineers have often only limited tools suitable for
the design of parts made of polymers, both in terms of mathematical models and reliable
material data, which together constitute the basis for a finite-elements based design.
Within this context, creep modelling constitutes a clear example of the needs for a more
refined approach. An accurate prediction of the creep behaviour of polymers would definitely
lead to a more refined design and thus to a better performance of the polymeric components.
However, a limited number of models is available within the f.e. codes, and when the model
complexity increases, it becomes sometimes difficult fitting the models parameters to the
experimental data.
In order to predict the polymer creep behaviour, this paper proposes a solution based on
artificial neural networks, where the experimental creep curves are used to determine the
parameters of a neural network which is then simply implemented in an Abaqus user
subroutine.
This allows to avoid the implementation of a complex material law and also the difficulties
related to match the experimental data to the model parameters, keeping easily into account
the dependence on stress and temperature.
After a discussion of the selection of the appropriate network and its parameters, an example
of the application of this approach to polyolefins in a simplified test case is presented.
FAA William J Huges Technical Center (NJ) conducts a research project to simulate failure in aeroengines and fuselages, main purpose is blade-out containment studies. This involved the implementation in LS-DYNA of a tabulated generalisation of the Johnson-Cook material law with regularisation to accommodate simulation of ductile materials.
The need for accurate material models to simulate the deformation, damage and failure of polymer matrix composites is becoming critical as these materials are gaining increased usage in the aerospace and automotive industries. While there are several composite material models currently available within LS-DYNA, there are several features that have been identified that could improve the predictive capability of a composite model. To address these needs, a combined plasticity and damage model suitable for use with both solid and shell elements is being developed and is being implemented into LS-DYNA as MAT_213. A key feature of the improved material model is the use of tabulated stress-strain data in a variety of coordinate directions to fully define the stress-strain response of the material. To date, the model development efforts have been focused on creating the plasticity portion of the model. The Tsai-Wu development efforts have focused on creating the plasticity portion of the model. The Tsai-Wu composite failure model has been generalized and extended to a strain-hardening based orthotropic material model with a non-associative flow rule. The coefficients of the yield function, and the stresses to be used in both the yield function and the flow rule are computed based on the input stress-strain curves using the effective plastic strain as the tracking variable. The coefficients in the flow rule are computed based on the obtained stress-strain data. The developed material model is suitable for implementation within LS-DYNA for use in analyzing the nonlinear response of polymer composites.
"A general purpose orthotropic elasto-plastic computational constitutive material model has been
developed to accurately predict the response of composites subjected to high velocity impact.
The three-dimensional orthotropic elasto-plastic composite material model is being implemented
initially for solid elements in LS-DYNA® as MAT213. In order to accurately represent the
response of a composite, experimental stress-strain curves are utilized as input, allowing for a
more general material model that can be used on a variety of composite applications. The
theoretical details are discussed in a companion paper. This paper documents the
implementation, verification and validation of the material model using the T800-F3900
fiber/resin composite material."
