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Federal Highway Administration Research and Technology
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| This report is an archived publication and may contain dated technical, contact, and link information |
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Publication Number: FHWA-HRT-04-094
Date: November 2004 |
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Evaluation of LS-DYNA Soil Material Model 147PDF Version (2.87 MB)
PDF files can be viewed with the Acrobat® Reader® Federal Highway Administration ForewordThis report documents the evaluation of a soil 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 the foundation soil in which roadside safety structures are mounted when undergoing a collision by a motor vehicle. This model is applicable for all soil types when one surface is exposed if appropriate material coefficients are inserted. Default material coefficients for National Cooperative Highway Research Program (NCHRP) Report 350, Strong Soil, 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 Soil Material Model 147 (FHWA-HRT-04-095), completely documents this material model for the user. The second report, Evaluation of LS-DYNA Soil Material Model 147 (FHWA-HRT-04-094), 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 performance evaluation, the developer and evaluator were unable to come to a final agreement regarding the model's performance and accuracy. (The material coefficients for the default soil result in a soil foundation that may be stiffer than desired.) These disagreements are listed and thoroughly discussed in chapter 9 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 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. This report does not constitute a standard, specification, or regulation. 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. Technical Report Documentation Page
Form DOT F 1700.7 (8-72) Reproduction of completed page authorized PrefaceThe goal of the work performed under this program, Development of DYNA3D Analysis Tools for Roadside Safety Applications, is to develop soil and wood 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. This work was performed under Federal Highway Administration (FHWA) Contract No. DTFH61-98-C-00071. The FHWA technical monitor was Martin Hargrave. 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 Soil Material Model 147,(2) thoroughly documents the soil model theory, reviews the model input, and provides example problems for use as a learning tool. This report, Evaluation of LS-DYNA Soil Material Model 147, comprises the performance evaluation for the soil model. It documents LS-DYNA parametric studies and correlations with test data performed by a potential end user of the soil model, along with commentary from the developer. 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 wood model. Development of the soil model was conducted by the prime contractor. The associated soil model evaluation effort to determine the model's performance and the accuracy of the results was a collaboration between the developer and evaluator. The developer created and partially evaluated the soil model. The evaluator performed a second, independent evaluation of the soil model, provided finite element meshes for the evaluation calculations, and provided shear test data for correlations with the model. Finally, the soil model was implemented into the LS-DYNA finite element code. Regarding the second, independent evaluation of the soil 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 listed and thoroughly discussed in chapter 9 of this evaluation report. Throughout this report, the developer of the soil material model, is referred to as the developer. The evaluator, a potential end user of the soil material model, is referred to as the user. The user's calculations and final evaluation of the soil model are documented in chapters 1 through 8 of this evaluation report. Table of ContentsCHAPTER 2. DIRECT SHEAR TESTING CHAPTER 3. BASELINE MODEL: DIRECT SHEAR TEST SIMULATION CHAPTER 4. MATERIAL INPUT PARAMETER STUDY VISCOSITY PARAMETERS, Vn AND GAMMAR Appropriate Values for Bulk and Shear Moduli ANGLE OF INTERNAL FRICTION, PHIMAX, AND COHESION, COH DRUCKER-PRAGER COEFFICIENT, AHYP PLASTICITY ITERATIONS, ITERMAX STRAIN HARDENING PARAMETERS, An AND Et PORE-WATER EFFECTS ON THE BULK MODULUS, PWD1 PORE-WATER EFFECTS ON PORE-WATER PRESSURE, PWD2 RESIDUAL SHEAR STRENGTH, PHIRES VOID FORMATION ENERGY, VDFM, AND VOLUMETRIC STRAIN, DINT DELETION DAMAGE, DAMLEV, AND PRINCIPAL FAILURE STRAIN CHAPTER 5. DEVELOPER'S RECOMMENDED PARAMETERS CHAPTER 6. ELEMENT FORMULATION: HOURGLASSINGCHAPTER 7. LARGE DEFORMATION TECHNIQUES CHAPTER 8. USER'S CONCLUSIONS AND RECOMMENDATIONS CHAPTER 9. DEVELOPER'S COMMENTS Issue 1: Model Will Not Run to Completion Issue 2: Hourglass, ALE, and Element Choice Material Input Parameter Study Angle of Internal Friction: Damage and Dilation Determining Input Parameter Values MATERIAL MODEL PARAMETERS, HOURGLASSING, AND ELEMENT CHOICE USER'S MANUAL QUESTIONS AND ANSWERS APPENDIX A. INITIAL SOIL EXPERIENCE OF USER APPENDIX B. VERIFICATION OF RESULTS ON DIFFERENT COMPUTER PLATFORMS Model hydten1: Hydrostatic Tension Model txc3-4pr0c.k: Triaxial Compression MULTI-ELEMENT CYLINDER: TRIAXIAL COMPRESSION TEST
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= 0.25