May 22, 2023 | by Datapoint Newsletters | views 1927
DatapointLabs Founders Retire; Company Continues Focus on Materials in Simulation
...read full post
Thermal
Mechanical
Foams
Newsletters
Validation
May 15, 2023 | by DatapointLabs | views 1579
Simulations play a crucial role in engineering and material science, and their success heavily relies on the accuracy of input data. Material testing, data conversion, fitting, and formatting are essential steps in the simulation process. This conference will highlight the importance of material testing requirements that extend beyond ISO and ASTM standards to obtain reliable data for input into various common material models, such as Elastic-Plastic, Hyperelastic, and Rate Dependent models. The complexity of foam materials is shown through a case study of successful validation of polyurethane (PU) foam ball drop impact test using LAW 90. PU foams exhibit high deformation with rate dependency in compressive loading, as well as viscoelastic unloading behavior. Proper handling of input test data and critical settings in simulation setup are crucial for accurate results. The case study will showcase our streamlined approach to successful simulation of foam materials, including challenges and limitations of current material models.
...read full post
Mechanical
Foams
Hyperelastic
Rate Dependency
Altair RADIOSS
Validation
September 22, 2022 | by DatapointLabs | views 1612
Material characterization considerations for SIGMASOFT simulations using thermoplastic and thermoset materials.
...read full post
Rheology
Thermal
Mechanical
Plastics
Rubbers
Injection Molding
SIGMASOFT
January 31, 2022 | by Datapoint Newsletters | views 2835
DatapointLabs Achieves Nadcap® Accreditation
...read full post
Thermal
Mechanical
Plastics
Composites
Quality
September 22, 2021 | by Datapoint Newsletters | views 2761
Improving Crash Simulations; Growth in Testing Services after Move
...read full post
Mechanical
Plastics
Metals
Automotive
LS-DYNA
Newsletters
June 18, 2021 | by Datapoint Newsletters | views 2932
DatapointLabs Poised for Growth after Move
...read full post
Density
Rheology
Thermal
Mechanical
Newsletters
March 05, 2019 | by Datapoint Newsletters | views 4879
High Humidity Testing, TestCart Online Order System, Matereality Version 12, Upcoming Events
...read full post
Mechanical
Plastics
Newsletters
Matereality
Materials Information Management
October 01, 2018 | by DatapointLabs | views 9042
Multiscale material models are being increasingly applied for high-level simulation of complex materials, such as continuous reinforced material products (unidirectional and woven product forms). These multiscale material models require input data from a minimum of experimental tests, which are then used to characterize a multiscale material model that can be used in structural simulations within a variety of commercial finite element solvers, including OptiStruct, RADIOSS, Abaqus, and LS-Dyna. Using these models, it is possible is to predict the performance of layups from single layer properties, as well as performance of these composites under complex loadings.
We present a framework where the required experimental data are collected, including a process for maintaining traceability and consistency of the experimental data using the Matereality software. Experimental test data are transmitted to the HyperWorks Multiscale Designer software for development of an appropriate multiscale material model. The resulting multiscale material model data is stored within Matereality linked to the source experimental data. Different manufactured layups are tested and compared to simulation in a validation step which provides a measure of the solution accuracy.
...read full post
Mechanical
Nonlinear Material Models
Structural Analysis
LS-DYNA
Abaqus
Composites
Altair RADIOSS
Validation
OptiStruct
November 15, 2017 | by Altair Engineering | views 4164
Simulation uncertainties arise from different assumptions made in model creation. Mid-stage software validations improve confidence and optimize the design of additively manufactured aerospace components.
...read full post
Mechanical
Aerospace and Defense
Structural Analysis
Papers
Validation
3D Printing
June 14, 2017 | by Hubert Lobo | views 4814
DatapointLabs Technical Center for Materials has a mission to strengthen the materials core of manufacturing enterprises by facilitating the use of new materials, novel manufacturing processes, and simulation-based product development. A whole-process approach is needed to address the role of materials in this context.
...read full post
Mechanical
Plastics
Rubbers
Metals
Hyperelastic
Nonlinear Material Models
Structural Analysis
ANSYS
Validation
3D Printing
Matereality
Materials Information Management
June 12, 2017 | by DatapointLabs | views 4532
Physically accurate simulation is a requirement for initiatives such as late-stage prototyping, additive manufacturing and digital twinning. The use of mid-stage validation has been shown to be a valuable tool to measure solver accuracy prior to use in simulation. Factors such as simulation settings, element type, mesh size, choice of material model, the material model parameter conversion process, quality and suitability of material property data used can all be evaluated. These validations do not use real-life parts, but instead use carefully designed standardized geometries in a controlled physical test that probes the accuracy of the simulation. With this a priori knowledge, it is possible to make meaningful design decisions. Confidence is gained that the simulation replicates real-life physical behavior. We present three case studies using different solvers and materials, which illustrate the broad applicability of this technique.
...read full post
Mechanical
Plastics
Rubbers
Metals
Structural Analysis
LS-DYNA
Abaqus
ANSYS
Research Papers
Presentations
Validation
3D Printing
May 10, 2017 | by Matereality | views 7376
We describe a new software component that takes into consideration the unique multi-variate nature of LS-DYNA material models. Rate-dependent models require adjustment and tuning of many material parameters to fit the rate-dependent tensile properties. Drawing upon a robust back-end data model, a graphical user interface provides drag and drop capability to allow the user to perform tasks such as model extrapolation beyond tested data, modulus change, rate dependency tuning and failure criteria adjustment while assuring self-consistency of the underlying material model. Unit system conversions are also facilitated, eliminating error and ensuring that material inputs to simulation correctly reflect the intent of the CAE analyst. The utility of the Matereality CAE modelers is illustrated with examples for LS-DYNA material models MAT_019, MAT_024 and MAT_089 LCSR.
...read full post
Mechanical
Rate Dependency
Yielding/Failure Analysis
LS-DYNA
Papers
Presentations
Matereality
April 06, 2017 | by DatapointLabs | views 4950
Performing simulations that can approximate the material behavior of ductile plastics is daunting. Factors such as nonlinear elasticity, inclusion of volumetric and deviatoric behavior, finding and correctly applying the proper material data to create failure criteria are only a few hurdles. A variety of material models exist, each with numerous settings and varied parameter conversion methods. Combined, these cause a great deal of uncertainty for the FEA user. In previous papers, we delved into material models for both LS-DYNA (MAT089, MAT024, and MAT187) and ABAQUS (*ELASTIC, *PLASTIC) using mid-stage validation as a technique to probe solver accuracy. In this presentation, we summarize our findings on the benefits of this combined approach as a general tool to test and tune simulations for greater reliability.
...read full post
Mechanical
Plastics
Automotive
High Speed Testing
Nonlinear Material Models
Structural Analysis
Universal Crash
Presentations
Validation
October 21, 2016 | by DatapointLabs | views 6286
Plastics exhibit non-linear viscoelastic behavior followed by a combination of deviatoric and volumetric plastic deformation until failure. Capturing these phenomena correctly in simulation presents a challenge because of limitations in commonly used material models. We follow an approach where we outline the general behavioral phenomena, then prescribe material models for handling different phases of plastics deformation. Edge cases will then be covered to complete the picture. Topics to be addressed include: Using elasto-plasticity; When to use hyperelasticity; Brittle polymers – filled plastics; Failure modes to consider; Criteria for survival; Choosing materials; Spatial non-isotropy from injection molding; Importance of residual stress; Visco-elastic and creep effects; Strain-rate effects for drop test and crash simulations; Fitting material data to FEA material models; The use of mid-stage validation as a tool to confirm the quality of simulation before use in real-life applications.
...read full post
Density
Rheology
Thermal
Mechanical
Plastics
Rubbers
Hyperelastic
Viscoelastic
Plasticity
Rate Dependency
Yielding/Failure Analysis
Injection Molding
Structural Analysis
ANSYS
Presentations
Validation
October 05, 2016 | by DatapointLabs | views 5499
Hyperelastic material models are complex in nature requiring stress-strain properties in uniaxial, biaxial and shear modes. The data need to be self-consistent in order to fit the commonly used material models. Choosing models and fitting this data to these equations adds additional uncertainty to the process. We present a validation mechanism where, using of a standard validation experiment one can compare results from a simulation and a physical test to obtain a quantified measure of simulation quality. Validated models can be used with greater confidence in the design of real-life components.
...read full post
Mechanical
Hyperelastic
Structural Analysis
ANSYS
Papers
Presentations
Validation
October 04, 2016 | by DatapointLabs | views 4887
Finite element analysis of plastics contains assumptions and uncertainties that can affect simulation accuracy. It is useful to quantify these effects prior to using simulation for real-life applications. A mid-stage validation uses a controlled physical test on a standardized part to compare results from simulation to physical experiment. These validations do not use real-life parts but carefully designed geometries that probe the accuracy of the simulation; the geometries themselves can be tested with boundary conditions that can be simulated correctly. In one study, a quasi-static three-point bending experiment of a standardized parallel ribbed plate is performed and simulated, using Abaqus. A comparison of the strain fields resulting from the complex stress state on the face of the ribs obtained by digital image correlation (DIC) vs. simulation is used to quantify the simulation's fidelity. In a second study, a dynamic dart impact experiment is validated using LS-Dyna probing the multi-axial deformation of a polypropylene until failure.
...read full post
Mechanical
Plastics
Automotive
Structural Analysis
LS-DYNA
Abaqus
Presentations
Validation
July 05, 2016 | by Hubert Lobo | views 4911
We will focus on our work related to the testing, modeling and validation of simulation for crash
and durability applications, including testing techniques, software tools for material parameter conversion, and
the use of a mid-stage validation process that uses standardized experiments to check the accuracy of the simulation prior to use in real-life applications. In addition, we present a short introduction to the Knowmats initiative which seeks to collect posts and links to papers from industry experts as a reference for simulation professionals.
...read full post
Mechanical
Plastics
Automotive
High Speed Testing
Nonlinear Material Models
Structural Analysis
Universal Crash
Presentations
Validation
June 24, 2016 | by Massimo Nutini | views 5235
Topics covered: Damage in mineral filled polypropylene under impact conditions; damage modeling and parameter identification (prior art, LyondellBasell contributions, debate in the CAE community); experimental and numerical validation; next steps
...read full post
Mechanical
Plastics
Rate Dependency
Yielding/Failure Analysis
Automotive
Material Supplier
High Speed Testing
LS-DYNA
Presentations
June 13, 2016 | by DatapointLabs | views 5711
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.
...read full post
Mechanical
Plastics
Rate Dependency
Yielding/Failure Analysis
Automotive
Toys/Sporting Goods
Packaging
High Speed Testing
LS-DYNA
Research Papers
Validation
June 03, 2016 | by DatapointLabs | views 8086
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.
...read full post
Mechanical
Plastics
Rubbers
Foams
Metals
Hyperelastic
Viscoelastic
Plasticity
Rate Dependency
Yielding/Failure Analysis
Aerospace and Defense
Automotive
Biomedical
Building Materials
Consumer Products
Energy and Petroleum
Material Supplier
Furniture
Industrial Goods
CAE Vendor/Supplier
Packaging
Home Appliances
Research Laboratory
High Speed Testing
Nonlinear Material Models
Structural Analysis
LS-DYNA
Abaqus
ANSYS
DIGIMAT
SOLIDWORKS
MSC.DYTRAN
MSC.MARC
MSC.NASTRAN
NX Nastran
PAM-COMFORT
PAM-CRASH
Altair RADIOSS
SIMULIA
Book Review
May 06, 2016 | by Megan Lobdell | views 4121
I found this to be a good explanation of calculating linear Drucker Prager variables for Abaqus.
...read full post
Mechanical
Plastics
Plasticity
Nonlinear Material Models
Abaqus
April 11, 2016 | by Datapoint Newsletters | views 5468
Focus on Validation, STEM Education, New Test Apparatus, Support for Altair HyperWorks
...read full post
Mechanical
LS-DYNA
Abaqus
Altair RADIOSS
Newsletters
Validation
November 11, 2015 | by Altair Engineering | views 4446
[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.
...read full post
Mechanical
Aerospace and Defense
Automotive
Injection Molding
Structural Analysis
Moldex3D
DIGIMAT
Papers
Altair RADIOSS
Newsletters
Validation
September 15, 2015 | by Altair Engineering | views 4968
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.
...read full post
Mechanical
Aerospace and Defense
CAE Vendor/Supplier
Structural Analysis
Altair RADIOSS
Presentations
Validation
3D Printing
September 10, 2015 | by DatapointLabs | views 4487
Molding Views, brought to you by the Injection Molding Division of the Society of Plastics Engineers
...read full post
Rheology
Mechanical
Injection Molding
Moldflow
Moldex3D
SIGMASOFT
Universal Molding
Simpoe-Mold
Newsletters
August 24, 2015 | by Massimo Nutini | views 4485
Optical strain measurement for the mechanical characterization of polymers, and in particular of polyolefins, is becoming a common practice to determine the parameters to be used in a finite element analysis of crash problems. This experimental technique allows measuring the strain locally on the specimen, so that it is particularly suitable when the deformation is localized, as in the case of polymers: therefore a more accurate description of the behaviour of the material is obtained. By so doing, it is possible to describe the material constitutive law in terms of the true, local strain and of the true stress. As these data are those needed by the most complete material models developed for impact calculation, it is clear that this technique is particularly suitable for coupling with the most advanced material models currently available in the F.E. codes, as for instance with Mat 187 (SAMP-1) of LS-Dyna. The local measurement of the strain can also be used for evaluating the volume strain, whose evolution with the increasing strain shows that for PP-based material the deformation is not isochoric in most the cases. The observed increase in the material volume reflects the fact that voids generate and coalesce within the material, possibly resulting in fracture. The measure of the volume strain, computed as the trace of the strain tensor, is here used for determining the damage function utilized by the damage model implemented in SAMP-1. The effective stress is here estimated as the stress which would be measured if the deformation was isochoric, and it can be assessed on the basis of the measurement of the longitudinal local strain only. Corresponding to each value of longitudinal strain, the volume strain is then used to calculate the ratio between the effective and the true stress. Adopting this procedure, the damage function is thus determined without the needs of repeated loading-unloading tests used to derive the damage parameter from the unloading slope, which is furthermore difficult to be measured. As an application, the results of the numerical reproduction of a benchmark test, consisting in a drop test on a polypropylene box, are presented and discussed
...read full post
Mechanical
Plastics
Rate Dependency
Yielding/Failure Analysis
Automotive
High Speed Testing
LS-DYNA
Research Papers
August 24, 2015 | by Massimo Nutini | views 4336
Glass-fiber-reinforced polypropylene (GF PP) materials are increasingly being used by customers to replace metal and engineering polymers in structural automotive applications. Like all glass-fiber reinforced thermoplastics, GF PP products can show anisotropy caused by fiber orientation that is induced by the injection process. Taking into account fiber orientation in the simulations enables designers to improve the accuracy of the analyses. This can help prevent arbitrary choices and assumptions when setting material parameters, which become mandatory when an isotropic material law is used. The method proposed in this paper takes advantage of the availability within Ls-dyna of an anisotropic material law (MAT_103), which allows simplified modeling to address critical issues. This law was not developed to address the problem discussed here.
Therefore, this paper illustrates a simplified approach. The presence of glass reinforced fibers is taken into account by running a mold-filling analysis, and then transferring the material flow orientation in to the structural simulation as a material angle. The dependence of the material failure strain on the material orientation can be also easily modeled through a user subroutine. Finally, the approach only requires simple material data based on basic tensile tests; the material law parameters are then identified through optimization techniques. Although this approach is based on some simplifying assumptions, its application is quick and can help the designer obtain more accurate results with respect to the traditional isotropic approach. A selection of validation tests is then proposed that show reliable predictions using limited additional computational effort.
...read full post
Mechanical
Plastics
Rate Dependency
Automotive
High Speed Testing
LS-DYNA
Research Papers
July 31, 2015 | by Massimo Nutini | views 4201
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.
...read full post
Mechanical
Plastics
Rate Dependency
Automotive
High Speed Testing
LS-DYNA
Research Papers
July 31, 2015 | by Massimo Nutini | views 4458
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.
...read full post
Mechanical
Plastics
Automotive
Biomedical
Structural Analysis
Abaqus
Research Papers
Validation
July 30, 2015 | by Helmut Gese | views 4026
"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."
...read full post
Mechanical
Metals
Rate Dependency
Yielding/Failure Analysis
Automotive
High Speed Testing
LS-DYNA
Research Papers
July 30, 2015 | by Helmut Gese | views 4546
"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."
...read full post
Mechanical
Plastics
Foams
Metals
Rate Dependency
Yielding/Failure Analysis
Automotive
High Speed Testing
LS-DYNA
Research Papers
July 30, 2015 | by Helmut Gese | views 4324
"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."
...read full post
Mechanical
Metals
Rate Dependency
Yielding/Failure Analysis
Automotive
High Speed Testing
LS-DYNA
Research Papers
July 28, 2015 | by Paul Du Bois | views 4743
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.
...read full post
Mechanical
Metals
Rate Dependency
Yielding/Failure Analysis
Aerospace and Defense
Automotive
High Speed Testing
LS-DYNA
Presentations
Validation
July 27, 2015 | by Paul Du Bois | views 4828
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.
...read full post
Mechanical
Plasticity
Yielding/Failure Analysis
Aerospace and Defense
Automotive
High Speed Testing
LS-DYNA
Composites
Research Papers
Validation
July 27, 2015 | by Paul Du Bois | views 4441
"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."
...read full post
Mechanical
Plasticity
Yielding/Failure Analysis
Aerospace and Defense
Automotive
High Speed Testing
LS-DYNA
Composites
Research Papers
Validation
July 27, 2015 | by Paul Du Bois | views 4563
"Recently new materials were introduced to enhance different aspects of automotive safety while minimizing the
weight added to the vehicle. Such foams are no longer isotropic but typically show a preferred strong direction due
to their manufacturing process. Different stress/ strain curves are obtained from material testing in different
directions. A new material model was added to the LS-DYNA code in order to allow a correct numerical simulation
of such materials. Ease-of-use was a primary concern in the development of this user-subroutine: we required stress/
strain curves from material testing to be directly usable as input parameters for the numerical model without
conversion. The user-subroutine is implemented as
MAT_TRANSVERSELY_ANISOTROPIC_CRUSHABLE_FOAM, Mat law 142 in LS-DYNA Version 960-1106.
In this paper we summarize the background of the material law and illustrate some applications in the field of
interior head-impact. The obvious advantage of incorporating such detail in the simulation lies in the numerical
assessment of impacts that are slightly offset with respect to the foam’s primary strength direction."
...read full post
Mechanical
Foams
Rate Dependency
Automotive
High Speed Testing
LS-DYNA
Research Papers
July 27, 2015 | by Paul Du Bois | views 4313
Lightweight design is one of the major principles in automotive engineering and has made polymer materials to inherent parts of modern cars. In addition to their lightweight thermoplastics, elastomers, fabric and composites also incur important functions in passive safety. In the age of virtual prototyping, assuring these functions requires the accurate modeling of the mechanical behavior of each component. Due to their molecular structure, polymer materials often show viscoelastic characteristics such as creep, relaxation and recovery. However, considering the general state of the art in crash simulation, the viscoelastic characteristics are mainly neglected or replaced by viscoplastic or hyperelastic and strain rate dependent material models. This is either due to the available material models that are often restricted to linear viscoelasticity and thus cannot model the experimental data or due to the time consuming parameter identification. In this study, a nonlinear viscoelastic material model for foams is developed and implemented as a user material subroutine in LS-DYNA. The material response consists of an equilibrium and a non-equilibrium part. The first one is modeled with a hyperelastic formulation based on the work of Chang [8] and formerly implemented as *MAT_FU_CHANG_FOAM in LS-DYNA (*MAT_083). The second one includes the nonlinear viscoelastic behavior following the multiple integral theory by Green and Rivlin [9]. The polyurethane foam Confor CF-45 used as part of the legform impactor in pedestrian safety was chosen for its highly nonlinear viscoelastic properties to test the presented approach. The investigation shows the ability of the method to reliably simulate some important nonlinear viscoelastic phenomena such as saturation.
...read full post
Mechanical
Foams
Viscoelastic
Automotive
Nonlinear Material Models
LS-DYNA
Research Papers
July 27, 2015 | by Paul Du Bois | views 4301
"Heavy trucks have large masses and only small deformation zones. Because of this, they are loaded
relatively severe in case of a crash. Under those conditions structural response is characterised not
only by plastic deformation but also by failure in terms of cracks or fracture. Hence, failure prediction is
essential for designing such parts.
The following article describes the procedure of generating material models for failure prognosis of
solid parts in the Commercial Vehicles Division at Daimler.
Sheet metal parts are mostly discretised by shell elements. In this case the state of stress is
characterized by hydrostatic pressure over von-Mises effective stress, the so-called triaxiality. For
many real-life load cases which can be modeled by thin shells this ratio is between –2/3 and –2/3.
Within this range the Gurson material model with the Tvergaard Needlemann addition leads to
sufficiently accurate results. Furthermore, the Gurson material model allows considering the effect of
element size, which amongst others is important for ductile materials.
Most often however, in the case of solid parts the state of stress is more complex, which results in a
triaxiality smaller than –1 or larger than 2/3. Gurson material models are usually validated based on
shell meshes and tensile tests with flat bar specimen. If applied to solid parts, these models tend to
underpredict failure . Thus, for solid parts the GURSON_JC material model is used.
The Johnson Cook parameters are derived from an existing Gurson material model. Afterwards the
material model is adapted to test results by modifying the load curve giving failure strain against
triaxiality. This requires tensile tests"
...read full post
Mechanical
Metals
Rate Dependency
Yielding/Failure Analysis
Automotive
High Speed Testing
LS-DYNA
Research Papers
Validation
July 27, 2015 | by Paul Du Bois | views 4423
"To assess the problem of containment after a blade-off accident in an aero-engine by numerical
simulation the FAA has instigated a research effort concerning failure prediction in a number of
relevant materials. Aluminium kicked off the program which involved an intensive testing program
providing failure data under different states of stress, different strain rates and different temperatures.
In particular split Hopkinson bars were used to perform dynamic punch tests on plates of different
thicknesses allowing to investigate the transition between different failure modes such as petaling and
plugging. Ballistic impact tests were performed at NASA GRC for the purpose of validation.
This paper focuses on the numerical simulation effort and a comparison with experimental data is
done. The simulations were performed with LS-DYNA and a tabulated version of the Johnson-Cook
material law was developed in order to increase the generality, flexibility and user-friendliness of the
material model."
...read full post
Mechanical
Metals
Yielding/Failure Analysis
Aerospace and Defense
High Speed Testing
LS-DYNA
Research Papers
Validation
July 27, 2015 | by Paul Du Bois | views 3922
"Reliable prediction of the behavior of structures made from polymers is a topic under considerable investigation in
engineering practice. Especially, if the structure is subjected to dynamic loading, constitutive models considering
the mechanical behavior properly are still not available in commercial finite element codes yet. In our paper, we
present a new constitutive law for polymers which recovers important phenomena like necking, crazing, strain rate
dependency, unloading behavior and damage. In particular, different yield surfaces in compression and tension and
strain rate dependent failure, the latter with damage induced erosion, is taken into account. All relevant parameters
are given directly in the input as load curves, i.e. time consuming parameter identification is not necessary. Moreover,
the models by von Mises and Drucker-Prager are included in the description as special cases.
With the present formulation, standard verification test can be simulated successfully: tensile and compression test,
shear test and three point bending tests."
...read full post
Mechanical
Plastics
Plasticity
Rate Dependency
Yielding/Failure Analysis
Automotive
High Speed Testing
LS-DYNA
Research Papers
July 27, 2015 | by Paul Du Bois | views 6354
"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. "
...read full post
Mechanical
Plastics
Plasticity
Rate Dependency
Yielding/Failure Analysis
Automotive
High Speed Testing
LS-DYNA
Research Papers
July 22, 2015 | by Paul Du Bois | views 4362
Generating a LS-DYNA material model from cupon-level quasi-static experimental data, developing appropriate failure characteristics, and scaling these characteristics to mesh sizes appropriate for a variety of simulation models requires a regularization procedure. During an Investigation of an anisotropic material model for extruded aluminum, numerical accuracy issues led to unrealistic mesh regularization curves and non-physical simulation behavior. Sensitivity problems due to constitutive material behavior, small mesh sizes, single precision simulations, and simulated test velocity all contributed to these accuracy issues. Detailed analysis into the sources of innaccuracy led to the conclusion that in certain cases, double precision simulations are necesscary for accurate material characterization and mesh regularization.
...read full post
Mechanical
Metals
Yielding/Failure Analysis
Aerospace and Defense
Automotive
Extrusion
Nonlinear Material Models
LS-DYNA
Research Papers
July 22, 2015 | by Paul Du Bois | views 4640
"Simulation of rubber-like materials is usually based on hyperelasticity. If strain-rate dependency has to be
considered viscous dampers are added to the rheological model. A disadvantage of such a description is timeconsuming
parameter identification associated with the damping constants. In this paper, a tabulated formulation is
presented which allows fast generation of input data based on uniaxial static and dynamic tensile tests at different
strain rates. Unloading, i.e. forming of a hysteresis, can also be modeled easily based on a damage formulation. We
show the theoretical background and algorithmic setup of our model which has been implemented in the explicit
solver LS-DYNA [1]-[3]. Apart from purely numerical examples, the validation of a soft and a hard rubber under
loading and subsequent unloading at different strain rates is shown."
...read full post
Mechanical
Rubbers
Hyperelastic
Rate Dependency
Yielding/Failure Analysis
Automotive
High Speed Testing
LS-DYNA
Research Papers
July 22, 2015 | by Paul Du Bois | views 4498
"Reliable prediction of the behaviour of structures made from polymers is a topic
under considerable investigation in engineering practice. Especially, if the
structure is subjected to dynamic loading, constitutive models considering the
mechanical behaviour properly are still not available in commercial finite element
codes.
First, we give an overview of material laws for thermoplastics and show how the
behaviour can be characterized and approximated by using visco-elasticity and
metal plasticity, respectively. Experimental work is presented to point out
important phenomena like necking, strain rate dependency, unloading behaviour
and damage. A constitutive model including the experimental findings is derived.
In particular, different yield surfaces in compression and tension and strain rate
dependent failure, the latter with damage induced erosion, need to be taken into
account. With the present formulation, standard verification tests can be
simulated successfully. Also, an elastic damage model is used to approximate
the unloading behaviour of thermoplastics adequately."
...read full post
Mechanical
Rate Dependency
Yielding/Failure Analysis
Automotive
High Speed Testing
LS-DYNA
Research Papers
July 22, 2015 | by Paul Du Bois | views 4114
"During the past years polymer materials have gained enormous importance in the automotive industry. Especially
their application for interior parts to help in passenger safety load cases and their use for bumper fascias in pedestrian
safety load cases have driven the demand for much more realistic finite element simulations. For such applications
the material model 187 (i.e. MAT_SAMP-1) in LS-DYNA® has been developed.
In the present paper the authors show how the parameters for the rather general model may be adjusted to allow for
the simulation of crazing effects during plastic loading. Crazing is usually understood as inelastic deformation that
exhibits permanent volumetric deformations. Hence a material model that is intended to be applied for polymer
components that show crazing effects during the experimental study, should be capable to produce the correct volumetric
strains during the respective finite element simulation. The paper discusses the real world effect of crazing,
the ideas to capture these effect in a numerical model and exemplifies the theoretical ideas with a real world structural
component finite element model."
...read full post
Mechanical
Plastics
Rate Dependency
Automotive
High Speed Testing
LS-DYNA
Research Papers
June 11, 2015 | by DatapointLabs | views 5355
With the growing interest in 3D printing, 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. In the first stage of our work, we seek to test an additively manufactured material for mechanical properties and validate its use in ANSYS simulation using the Cornell Bike Crank model.
...read full post
Mechanical
ANSYS
Research Papers
Validation
3D Printing
April 28, 2015 | by Matereality | views 11520
TPM has posted this 3 minute video on how to use the SolidWorks Materials Portal
Mechanical
Metals
Structural Analysis
SOLIDWORKS
April 28, 2015 | by DatapointLabs | views 5086
There is interest in quantifying the accuracy of different material models being used in LS-DYNA today for the modeling of plastics. In our study, we characterize two ductile, yet different materials, ABS and polypropylene for rate dependent tensile properties and use the data to develop material parameters for the material models commonly used for plastics: MAT_024 and its variants, MAT_089 and MAT_187. We then perform a falling dart impact test which produces a complex multi-axial stress state and simulate this experiment using LS-DYNA. For each material model we are able to compare simulation to actual experiment thereby obtaining a measure of fidelity of the simulation to reality. In this way, we can assess the benefits of using a particular material model for plastics simulation.
...read full post
Mechanical
Plastics
Rate Dependency
LS-DYNA
Research Papers
Validation
April 28, 2015 | by Paul Du Bois | views 4144
"The simulation of rubber materials is becoming increasingly
important in automotive crashworthiness simulations.
Although highly sophisticated material laws are available in
LS-DYNA to model rubber parts, the determination of material
properties can be non-trivial and time consuming. In many
applications, the rubber component is mainly loaded uniaxially
at rather high strain rates. In this paper a simplified material
model for rubber is presented allowing for a fast generation of
input data based on uniaxial static and dynamic test data."
...read full post
Mechanical
Rubbers
Hyperelastic
Rate Dependency
Automotive
High Speed Testing
LS-DYNA
Research Papers
March 12, 2015 | by DatapointLabs | views 5646
Finite-element analysis and injection-molding simulation are two technologies that are seeing widespread use today in the design of plastic components. Limitations exist in our ability to mathematically describe the complexity of polymer behavior to these software packages. Material models commonly used in finite-element analysis were not designed for plastics, making it difficult to correctly describe non-linear behavior and plasticity of these complex materials. Time-based viscoelastic phenomena further complicate analysis. Dealing with fiber fillers brings yet another layer of complexity. It is vital to the plastics engineer to comprehend these gaps in order to make good design decisions. Approaches to understanding and dealing with these challenges, including practical strategies for everyday use, will be discussed.
...read full post
Mechanical
Plastics
Blow Molding
Extrusion
Injection Molding
Nonlinear Material Models
Structural Analysis
Thermoforming
LS-DYNA
Abaqus
DIGIMAT
Presentations
March 09, 2012 | by Datapoint Newsletters | views 5524
Expanded Mechanical Test Capabilities.
...read full post
Mechanical
Rubbers
Newsletters
September 15, 2011 | by Datapoint Newsletters | views 4568
Expansion: New Lab Space, New TestPaks. DIGIMAT MX Reverse Engineering Update.
...read full post
Mechanical
DIGIMAT
PAM-COMFORT
Newsletters
July 14, 2011 | by Datapoint Newsletters | views 4587
New Lab Space & Equipment
...read full post
Mechanical
Newsletters
May 11, 2009 | by DatapointLabs | views 5408
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.
...read full post
Mechanical
Plastics
Aerospace and Defense
Automotive
Consumer Products
Material Supplier
Industrial Goods
Packaging
Home Appliances
High Speed Testing
Nonlinear Material Models
Structural Analysis
LS-DYNA
Abaqus
ANSYS
MSC.DYTRAN
PAM-CRASH
Altair RADIOSS
Research Papers
August 25, 2008 | by Datapoint Newsletters | views 4793
New 100kN Instron. New TestPaks Alliance Partner. Expanded Viso-Elastic Testing Capability. New at TestPaks.com.
...read full post
Mechanical
Viscoelastic
SOLIDWORKS
ANSYS FIDAP
POLYFLOW Extrusion
Newsletters
April 28, 2005 | by DatapointLabs | views 4988
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
...read full post
Mechanical
Plastics
Rate Dependency
Aerospace and Defense
Automotive
Consumer Products
Material Supplier
Toys/Sporting Goods
Packaging
Home Appliances
High Speed Testing
Nonlinear Material Models
Structural Analysis
LS-DYNA
Abaqus
ANSYS
MSC.DYTRAN
PAM-CRASH
Research Papers
March 18, 1994 | by DatapointLabs | views 4176
This book presents a valuable resource for engineers and designers seeking to apply structural analysis and other advanced methods to the design of plastic parts. The reader learns what to expect for the mechanical properties of polymers and develops a grasp of how plastics respond to various applied stress conditions. The book introduces mechanical tests and polymer transitions, moving onward into chapters on elastic behavior, creep and stress relaxation, dynamic mechanical properties, stress- strain behavior and strength, It also covers abrasion, fatigue, friction and stress cracking. Additionally, the effects of fillers and fibers on these properties are considered.
...read full post
Mechanical
Plastics
Structural Analysis
Composites
Book Review