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A Comparative Review of Damage and Failure Models and a Tabulated Generalization

by Paul Du Bois7,793 views

"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. "

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AutomotiveHigh Speed TestingLS-DYNAMechanicalPlasticityPlasticsRate DependencyResearch PapersYielding/Failure Analysis

Using an Intermediate Validation Step to Increase CAE Confidence

by DatapointLabs7,360 views

Simulations contain assumptions and uncertainties that a designer must evaluate to obtain a measure of accuracy. The assumptions of the product design can be differentiated from the ones for the solver and material model through the use of a mid-stage validation. An open loop validation uses a controlled test on a standardized part to compare results from a simulation to the physical experiment. From the validation, confidence in the material model and solver is gained. In this study, the material properties of a polypropylene are tested to characterize for an *ELASTIC *PLASTIC model in ABAQUS. A validation of a quasi-static three-point bending experiment of a parallel ribbed plate is then performed and simulated. 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.

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AbaqusAutomotiveBiomedicalConsumer ProductsFurnitureHome AppliancesMaterial SupplierNonlinear Material ModelsPackagingPlasticityPlasticsResearch PapersStructural AnalysisToys/Sporting GoodsValidation

A Standardized Mechanism to Validate Crash Models for Ductile Plastics

by DatapointLabs7,342 views

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.

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AutomotiveHigh Speed TestingLS-DYNAMechanicalPackagingPlasticsRate DependencyResearch PapersToys/Sporting GoodsValidationYielding/Failure Analysis

A Design-Validation-Production Workflow for Aerospace Additive Manufacturing

by DatapointLabs7,120 views

With the advent of 3D printing and additive manufacturing, manufacturing designs previously thought difficult to produce can now be generated quickly and efficiently and without tooling. In the aerospace industry, weight is often tied directly to cost and is thus of great importance to any engineering design. Traditionally, the design process often involves much iteration between the designer and the analyst, where the designer submits a design to the analyst, and then the analyst completes his or her analysis and sends recommendations back to the designer. The process is repeated until a valid design meets the analysis criteria. The design is then handed to the manufacturing team which then may have additional constraints or concerns and iterations can continue. Additive manufacturing coupled with topology optimization allows the design and analysis loops and manufacturing iterations to be reduced significantly or even eliminated. The critical step is to ensure that the part will perform as simulated.

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3D PrintingAerospace and DefenseAltair RADIOSSMetalsResearch PapersStructural AnalysisValidation

A Robust Methodology to Calibrate Crash Material Models for Polymers

by DatapointLabs6,875 views

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.

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ANSYSAbaqusAerospace and DefenseAltair RADIOSSAutomotiveConsumer ProductsHigh Speed TestingHome AppliancesIndustrial GoodsLS-DYNAMSC.DYTRANMaterial SupplierMechanicalNonlinear Material ModelsPAM-CRASHPackagingPlasticsResearch PapersStructural Analysis

Finite Element Analysis of Additively Manufactured Products

by DatapointLabs6,782 views

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.

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3D PrintingANSYSMechanicalResearch PapersValidation

A Novel Technique to Measure Tensile Properties of Plastics at High Strain Rates

by DatapointLabs6,760 views

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

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ANSYSAbaqusAerospace and DefenseAutomotiveConsumer ProductsHigh Speed TestingHome AppliancesLS-DYNAMSC.DYTRANMaterial SupplierMechanicalNonlinear Material ModelsPAM-CRASHPackagingPlasticsRate DependencyResearch PapersStructural AnalysisToys/Sporting Goods

Comparison of Crash Models for Ductile Plastics

by DatapointLabs6,503 views

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.

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LS-DYNAMechanicalPlasticsRate DependencyResearch PapersValidation

High Speed Stress Strain Material Properties as Inputs for the Simulation of Impact Situations

by DatapointLabs6,392 views

With the recent changes in the crashworthiness requirements for US automobiles for improved safety, design engineers are being challenged to design interior trim systems comprised of polymeric materials to meet these new impact requirements. Impact analysis programs are being used increasingly by designers to gain an insight into the final part performance during the design stage. Material models play a crucial role in these design simulations by representing the response of the material to an applied stimulus. In this work, we seek to develop novel test methods to generate high speed stress-strain properties of plastics, which can be used as input to structural analysis programs...

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ANSYSAbaqusAerospace and DefenseHigh Speed TestingHome AppliancesLS-DYNAMSC.DYTRANMaterial SupplierMetalsNonlinear Material ModelsPAM-CRASHPackagingPlasticsResearch PapersStructural AnalysisThermoformingToys/Sporting Goods

Theoretical Development of an Orthotropic Elasto-Plastic Generalized Composite Material Model

by Paul Du Bois6,223 views

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.

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Aerospace and DefenseAutomotiveCompositesHigh Speed TestingLS-DYNAMechanicalPlasticityResearch PapersValidationYielding/Failure Analysis