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Unified creep plasticity damage (UCPD) model for rigid polyurethane foams

Conference Proceedings of the Society for Experimental Mechanics Series

Neilsen, Michael K.; Lu, Wei-Yang L.; Scherzinger, William M.; Hinnerichs, Terry D.; Lo, Chi S.

Experiments were performed to characterize the mechanical response of several different rigid polyurethane foams to large deformation. In these experiments, the effects of load path, loading rate, and temperature were investigated. Results from these experiments indicated that rigid polyurethane foams exhibit significant damage, volumetric and deviatoric plasticity when they are compressed. Rigid polyurethane foams were also found to be extremely strain-rate and temperature dependent. These foams are also rather brittle and crack when loaded to small strains in tension or to larger strains in compression. Thus, a phenomenological Unified Creep Plasticity Damage (UCPD) model was developed to describe the mechanical response of these foams to large deformation at a variety of temperatures and strain rates. This paper includes a description of recent experiments and experimental findings. Next, development of a UCPD model for rigid, polyurethane foams is described. Finite element simulations with the new UCPD model are compared with experimental results to show behavior that can be captured with this model.

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TYPE Conference Poster YEAR 2016
ScopusOSTI

Unified Creep Plasticity Damage (UCPD) Model for Rigid Polyurethane Foams

Neilsen, Michael K.; Lu, Wei-Yang L.; Scherzinger, William M.; Hinnerichs, Terry D.; Lo, Chi S.

Numerous experiments were performed to characterize the mechanical response of several different rigid polyurethane foams (FR3712, PMDI10, PMDI20, and TufFoam35) to large deformation. In these experiments, the effects of load path, loading rate, and temperature were investigated. Results from these experiments indicated that rigid polyurethane foams exhibit significant volumetric and deviatoric plasticity when they are compressed. Rigid polyurethane foams were also found to be very strain-rate and temperature dependent. These foams are also rather brittle and crack when loaded to small strains in tension or to larger strains in compression. Thus, a new Unified Creep Plasticity Damage (UCPD) model was developed and implemented into SIERRA with the name Foam Damage to describe the mechanical response of these foams to large deformation at a variety of temperatures and strain rates. This report includes a description of recent experiments and experimental findings. Next, development of a UCPD model for rigid, polyurethane foams is described. Selection of material parameters for a variety of rigid polyurethane foams is then discussed and finite element simulations with the new UCPD model are compared with experimental results to show behavior that can be captured with this model.

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TYPE SAND Report YEAR 2015
OSTIDOI

Validation of a viscoplastic model for foam response over a wide temperature range

Conference Proceedings of the Society for Experimental Mechanics Series

Smith, Adam; Hinnerichs, Terry D.; Lo, Chi S.; Neilsen, Michael K.; Bateman, Vesta I.; Carlson, Lawrence W.; Lu, Wei-Yang L.; Jin, Helena

Accurate material models are fundamental to predictive structural finite element models. Because potting foams are routinely used to mitigate shock and vibration of encapsulated components in electro/mechanical systems, accurate material models for foams are needed. A viscoplastic foam constitutive model has been developed to represent the large nonlinear and rate dependent crush of a polyurethane foam throughout an application space defined by temperature, strain rate and strain levels. Validation of this viscoplastic model, which is implemented in the transient dynamic Presto finite element code, is being achieved by modeling and testing a series of structural geometries of increasing complexity that have been designed to ensure sensitivity to material parameters. Both experimental and analytical uncertainties are being quantified to ensure fair assessment of model validity. Quantitative model validation metrics are being developed to provide a means of comparing analytical model predictions with experimental observations. This paper focuses on model validation of foam/component behavior over a wide temperature, strain rate, and strain level range using a Presto viscoplastic finite element model. Experiments include simple foam/component test articles crushed in a series of drop table tests. Material variations of density have been included. A double blind validation process is described that brings together test data with model predictions.

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TYPE Conference YEAR 2007
ScopusOSTI

Full-field characterization of mechanical behavior of polyurethane foams

International Journal of Solids and Structures

Jin, Helena; Lu, Wei-Yang L.; Scheffel, Simon S.; Hinnerichs, Terry D.; Neilsen, Michael K.

The foam material of interest in this investigation is a rigid closed-cell polyurethane foam PMDI with a nominal density of 20 pcf (320 kg/m3). Three separate types of compression experiments were conducted on foam specimens. The heterogeneous deformation of foam specimens and strain concentration at the foam-steel interface were obtained using the 3-dimensional digital image correlation (3D-DIC) technique. These experiments demonstrated that the 3D-DIC technique is able to obtain accurate and full-field large deformation of foam specimens, including strain concentrations. The experiments also showed the effects of loading configurations on deformation and strain concentration in foam specimens. These DIC results provided experimental data to validate the previously developed viscoplastic foam model (VFM). In the first experiment, cubic foam specimens were compressed uniaxially up to 60%. The full-field surface displacement and strain distributions obtained using the 3D-DIC technique provided detailed information about the inhomogeneous deformation over the area of interest during compression. In the second experiment, compression tests were conducted for cubic foam specimens with a steel cylinder inclusion, which imitate the deformation of foam components in a package under crush conditions. The strain concentration at the interface between the steel cylinder and the foam specimen was studied in detail. In the third experiment, the foam specimens were loaded by a steel cylinder passing through the center of the specimens rather than from its end surface, which created a loading condition of the foam components similar to a package that has been dropped. To study the effects of confinement, the strain concentration and displacement distribution over the defined sections were compared for cases with and without a confinement fixture.

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TYPE Journal Article YEAR 2007
ScopusOSTI

Model validation of experimental hardware, design versus reality

Conference Proceedings of the Society for Experimental Mechanics Series

O'Gorman, Christian C.; Hunter, Patrick H.; Stasiunas, Eric C.; Hinnerichs, Terry D.; Paez, Thomas L.; Urbina, Angel U.

A detailed model validation study has been initiated to assess model predictions of foam encapsulated components. A bottom-up experimental approach has been used to first characterize the foam material, and then characterize foam/component interaction within increasingly complex systems. This paper presents a summary of the model validation approach at component and benchmark levels and details specific issues identified at the subsystem validation level. Specifically, manufacturing process issues were identified in the hardware which precluded continued validation. A summary of the modal data is given and the issues relating to the manufacturing process are discussed.

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TYPE Conference YEAR 2006
ScopusOSTI
Results 1–25 of 38
Results 1–25 of 38