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Publication Number: FHWA-HRT-04-096
Date: August 2005

Evaluation of LS-DYNA Wood Material Model 143

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FOREWORD

This report documents the evaluation of a wood material model that has been implemented into the dynamic finite element code LS-DYNA, beginning with version 970. This material model was developed specifically to predict the dynamic performance of wood components used in roadside safety structures when undergoing a collision by a motor vehicle. This model is applicable for all varieties of wood when appropriate material coefficients are inserted. Default material coefficients for two wood varieties, southern yellow pine and Douglas fir, are stored in the model and can be accessed for use.

This report is one of two that completely documents this material model. The first report, Manual for LS-DYNA Wood Material Model 143 (FHWA-HRT-04-097), completely documents this material model for the user. The second report, Evaluation of LS-DYNA Wood Material Model 143 (FHWA-HRT-04-096), completely documents the model’s performance and the accuracy of the results. This performance evaluation was a collaboration between the model developer and the model evaluator. Regarding the model’s performance evaluation, the developer and the evaluator were unable to come to a final agreement regarding the model’s performance and accuracy. These disagreements are itemized and thoroughly discussed in chapter 17 of the second report.

This report will be of interest to research engineers associated with the evaluation and crashworthy performance of roadside safety structures, particularly those engineers responsible for the prediction of the crash response of such structures when using the finite element code LS-DYNA.

Michael F. Trentacoste
Michael F. Trentacoste, Director
Offices of Safety Research and Development

Notice

This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document.

The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers' names appear in this report only because they are considered essential to the objective of the document.

Quality Assurance Statement

The Federal Highway Administration (FHWA) provides high-quality information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement.

1. Report No

FHWA-HRT-04-096

2. Government Accession No.

 

3. Recipient's Catalog No.

 

4. Title and Subtitle

Evaluation of LS-DYNA Wood Material Model 143

5. Report Date

August 2005

6. Performing Organization Code

 

7. Authors(s)

Y.D. Murray, J.D. Reid, R.K. Faller, B.W. Bielenberg, and T.J. Paulsen

8. Performing Organization Report No.

 

9. Performing Organization Name and Address

APTEK, Inc.
1257 Lake Plaza Drive, Suite 100
Colorado Springs, CO 80906-3558

Midwest Roadside Safety Facility
University of Nebraska at Lincoln
1901 Y Street, Building C
Lincoln, NE 68588-0601

10. Work Unit No. (TRAIS)

 

11. Contract or Grant No.

DTFH61-98-C-00071

13. Type of Report and Period Covered

Final Report
Sept. 1998-Sept. 2002

12. Sponsoring Agency Name and Address

Volpe National Transportation Systems Center
55 Broadway, Kendall Square
Cambridge, MA 02142-1093

Federal Highway Administration
6300 Georgetown Pike
McLean, VA 22101-2296

14. Sponsoring Agency Code

15. Supplementary Notes

Contracting Officer’s Technical Representative (COTR): Martin Hargrave, Office of Safety Research and Development

16. Abstract

Calculations are performed with the finite element code LS-DYNA to evaluate the performance of wood material model 143 and to set default material properties for southern yellow pine and Douglas fir. Correlations with published test data include static bending and compression simulations of dry timbers, static bending of saturated posts, and dynamic simulation of saturated posts impacted by bogie vehicles.

The companion manual to this report is:
Manual for LS-DYNA Wood Material Model 143 (FHWA-HRT-04-097)

17. Key Words

Wood, southern yellow pine, Douglas fir, LS DYNA, modeling and simulation, damage, rate effects, plasticity.

18. Distribution Statement

No restrictions. This document is available to the public through the National Technical Information Service, Springfield, VA 22161.

19. Security Classif. (of this report)

Unclassified

20. Security Classif. (of this page)

Unclassified

21. No. of Pages

152

22. Price

 

Form DOT F 1700.7 (8-72)

Reproduction of completed page authorized

Preface

The goal of the work performed under this program, Development of DYNA3D Analysis Tools for Roadside Safety Applications, is to develop wood and soil material models, implement the models into the LS-DYNA finite element code,(1) and evaluate the performance of each model through correlations with available test data.

Two reports are available for each material model. One report is a user’s manual; the second report is a performance evaluation. The user’s manual, Manual for LS-DYNA Wood Material Model 143,(2) thoroughly documents the wood model theory, reviews the model input, and provides example problems for use as a learning tool. It is written by the developer of the model. This report, Evaluation of LS DYNA Wood Material Model 143, comprises the performance evaluation for the wood model. It documents LS-DYNA parametric studies and correlations with test data performed by the model developer, and by a potential end user. The reader is urged to review the user’s manual before reading this evaluation report. A user’s manual(3) and evaluation report(4) are also available for the soil model.

The development of the wood model was conducted by the prime contractor. The associated wood model evaluation effort to determine the model‘s performance and the accuracy of the results was a collaboration between the developer and the potential end user, with the user’s evaluation intended to be independent of the developer’s evaluation. The developer partially evaluated the wood model. The potential end user performed a second independent evaluation of the wood model, provided finite element meshes for the evaluation calculations, and provided static post and bogie impact test data for correlations with the model.

Regarding the second independent evaluation of the wood model, the developer and evaluator were unable to come to a final agreement regarding several issues associated with the model‘s performance and accuracy. These issues are itemized and thoroughly discussed by the developer in chapter 17 of this evaluation report.

Throughout this report, the developer of the wood material model is referred to as the developer. The potential end user of the wood material model is referred to as the user. The developer’s calculations and conclusions are given in chapters 1 through 8 of this report. The user’s calculations and conclusions are given in chapters 9 through 16 of this report.


SI* (Modern Metric) Conversion Factors


Table of Contents

Page

  1. Developer's Introduction

    1.1 Model Theory
    1.2 Model Input
    1.3 Limitations of Laboratory Material Property Data
    1.4 Evaluation Process
    1.5 Verification and Validation

  2. Single-Element Simulations

  3. Timber Compression Test Correlations

  4. Timber-Bending Test Correlations

  5. Quasi-Static Post Test Correlations

    5.1 Southern Yellow Pine Bending Test Data
    5.2 LS-DYNA Correlations
    5.3 LS-DYNA Parametric Studies

  6. Dynamic Post Test Correlations

    6.1 Bogie Impact Test Data
    6.2 LS-DYNA Correlations
    6.3 Filtering and Sampling Issues
    6.4 LS-DYNA Parametric Studies

  7. Additional Evaluation Calculations

    7.1 Plasticity Algorithm Iterations
    7.2 Fully Integrated Elements
    7.3 Erosion Criteria
    7.4 Post-Peak Hardening Parameter

  8. Developer's Summary and Recommendations

  9. User's Introduction

  10. Validation Criteria for the Wood Material Model

    10.1 NDOR Tests: Performance Envelopes

  11. Verification of Results on Different Computer Platforms

    11.1 Single-Element Models
    11.2 Dynamic Post Test Simulation: Bogie Model
    11.3 Dynamic Post Test Simulation: Fast Bogie Model

  12. Single Element: Tension Parallel to the Grain

    12.1 Stress-Strain Behavior: *MAT_WOOD_PINE
    12.2 Volume of Element: *MAT_WOOD_PINE
    12.3 Material Properties: *MAT_WOOD_PINE

  13. Static Wood Post Test Simulations

    13.1 Static Post Model
    13.2 Baseline Model Versus Test Comparison
    13.3 Baseline Versus Refined-Mesh Comparison
    13.4 Parameter Study

  14. Static Wood Post Test Simulations

    14.1 Dynamic Post Model
    14.2 Vaporization and Time Step
    14.3 Sharp Edge Contacts
    14.4 Bending
    14.5 Further Analysis

  15. Element Formulation: Hourglassing

  16. User's Conclusions

  17. Developer's Comments on User's Evaluation

    17.1 Table of Wood Model Topics
    17.2 Discussion of Wood Model Topics
    17.3 Instabilities in Dynamic Analyses

  18. References

List of Figures

List of Tables

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