Knowmats is an informal repository of information related to materials and simulation. The information helps simulation professionals perform best-in-class simulation with a better understanding of how materials are represented in FEA and simulation. read more...
August 24, 2015 | by Sigmasoft | views 4713
The profitability of a molded rubber product depends to a large extent on the mold efficiency. To achieve the maximum productivity, besides the larges possible number of cavities it is desirable to minimize the rubber consumption and to produce parts without defects.
Rheology Rubbers Automotive Biomedical Injection Molding SIGMASOFT Newsletters
August 24, 2015 | by Altair Engineering | views 3907
Import your Matereality CAE Material cards directly into HyperWorks.
August 10, 2015 | by Tony Abbey | views 3998
Even with powerful modern computers, there is often a motivation to use simplifying techniques in structural finite element analysis (FEA).
August 10, 2015 | by Tony Abbey | views 5200
I was recently tasked with creating material to explain what Verification and Validation (V&V) are in relation to FEA (finite element analysis).
August 10, 2015 | by Datapoint Newsletters | views 5753
Material Model Validation, New Knowledge Hub
July 31, 2015 | by Massimo Nutini | views 4310
Questo articolo si propone di illustrare l’importanza dell’utilizzo di metodi per la misura delle proprietà locali del materiale per determinarne la legge di comportamento. Vengono di seguito presentati alcuni esempi che evidenziano quanto più accurate e realistiche siano le simulazioni numeriche di test di trazione ad alta velocità su provini di poliolefine, quando vengano utilizzate proprietà dei materiali rilevate con misure locali, utilizzando metodi ottici. La disponibilità di misure locali e più accurate evidenzia come sia necessario che nei codici di calcolo commerciali vengano implementate delle leggi di materiale più sofisticate di quelle disponibili attualmente, che sono state per lo più originariamente sviluppate per materiali metallici, e dunque non riescono sempre a predire correttamente il comportamento dei componenti in materiali polimerici.
Mechanical Plastics Rate Dependency Automotive High Speed Testing LS-DYNA Research Papers
July 31, 2015 | by Massimo Nutini | views 4597
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.
Mechanical Plastics Automotive Biomedical Structural Analysis Abaqus Research Papers Validation
July 30, 2015 | by Helmut Gese | views 4155
"In sheet-metal-forming the forming limit curve (FLC) is used for ductile sheets to predict fracture in deep drawing. However the use of the FLC is limited to linear strain paths. The initial FLC cannot be used in a complex nonlinear strain history of a deep drawing process or a successive stamp and crash process including a significant change in strain rate. The CRACH software has been developed to predict the forming limit of sheets for nonlinear strain paths [1]. It has been validated to predict instability for bilinear strain paths with static loading in the first path and dynamic loading in the second path for mild steels [2]. As the postprocessing of strain paths from single finite elements in CRACH is not economic for industrial applications MATFEM initiated a project to couple CRACH directly with FEM-Code LS-DYNA using a userdefined material model. This allows a prediction of possible failure during the simulation for all elements with respect to their complete strain history. A special strategy has been developed to include CRACH without extensive increase in total CPU time. The developed interface to LS-DYNA allows also the implementation of other failure criteria demanding the history of deformation like for example a tensorial fracture criterion. In order to test the reliability of the calculated safety factor experimental tests for bilinear strain paths have been simulated [2]. In this case the experimental and numerical investigations have been made on two-stage forming processes (static in the 1st stage and both static/dynamic in the 2nd stage) . The static-static case should simulate a stamping process with bilinear strain path. The static-dynamic case should simulate a successive stamp and crash process. The simulation of a complex deep drawing problem including areas with significantly nonlinear strain paths has been simulated with LS-DYNA/CRACH-coupling. It can be shown that the prediction of CRACH can differ significantely from a “standard” prediction based on the initial FLC. The coupling of LS-DYNA and CRACH showed the potential to predict possible fracture in deep drawing and crash loading at an early design stage and allowed to optimise geometry and material quality to significantly reduce later problems in real components."
Mechanical Metals Rate Dependency Yielding/Failure Analysis Automotive High Speed Testing LS-DYNA Research Papers
July 30, 2015 | by Helmut Gese | views 4674
"Today the automotive industry is faced with the demand to build light fuel-efficient vehicles while optimizing its crashworthiness and stiffness. A wide variety of new metallic and polymeric materials have been introduced to account for these increased requirements. Numerical analysis can significantly support this process if the analysis is really predictive. Within the numerical model a correct characterization of the material behaviour – including elasto-viscoplastic behaviour and failure - is substantial. The particular behaviour of each material group must be covered by the material model. The user material model MF GenYld+CrachFEM allows for a modular combination of phenomenological models (yield locus, strain hardening, damage evolution, criteria for fracture initiation) to give an adequate representation of technical materials. This material model can be linked to LS-DYNA when using the explicit-dynamic time integration scheme. This paper gives an overview on the material characterization of ultra high strength steels (with focus on failure prediction), non-reinforced polymers (with focus on anisotropic hardening of polymers), and structural foams (with focus on compressibility and stress dependent damage evolution) with respect to crash simulation. It will be shown that a comprehensive material model - including damage and failure behaviour - enables a predictive simulation without iterative calibration of material parameters. A testing programme has been done for each material group in order to allow a fitting of the parameters of the material model first. In a second step different component tests have been carried out, which were part of a systematic procedure to validate the appropriate predictions of the crash behaviour with LS-Dyna and user material MF_GenYld+CrachFEM for each material group."
Mechanical Plastics Foams Metals Rate Dependency Yielding/Failure Analysis Automotive High Speed Testing LS-DYNA Research Papers
July 30, 2015 | by Helmut Gese | views 4443
"The Crash Simulation of Magnesium Structures with Finite Element Methods demands the use of suitable material and failure models. An associated plasticity model describing the complex asymmetric yield behaviour in tension and compression of Mg extrusions has been developed during the InMaK-project (Innovative Magnesium Compound Structures for Automobile Frames) supported by the German Federal Ministry for Education and Research (BMBF). Differences to the material model 124 in LS-DYNA are exposed. In order to describe the failure behaviour of Mg extrusions under multiaxial loading in FEM crash simulation this constitutive model has been combined with a fracture model for ductile and shear fracture. The fracture model has been added to the user defined constitutive magnesium model in LS-DYNA. The experimental investigations carried out on model components are compared with numerical derived results. Experimental methods for fracture parameter evaluation are shown and general aspects of metal failure due to fracture as well as different modelling techniques are discussed."
Mechanical Metals Rate Dependency Yielding/Failure Analysis Automotive High Speed Testing LS-DYNA Research Papers
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