Development of Verification and Validation Procedures for Computer Simulation use in Roadside Safety Applications NCHRP 22-24

Transcription

1 Development of Verification and Validation Procedures for Computer Simulation use in Roadside Safety Applications NCHRP PHENOMENA IMPORTANCE RANKING TABLES (PIRTS)

2 Meeting Agenda 1:00-1:15 Introductions/Kick-off (Roger Bligh) 1:15 2:45 Calculating validation/verification metrics» Description of the RSVVP program with examples (presentation)» Comparison of identical crash tests (presentation)» Discussion about shape-comparison metric calculations (group discussion) 2:45-3:15 Subject Mater Expert Opinions» Description on the SME activity (short presentation)» Distribute SME worksheets to the group (group activity)» Hand in SME worksheets 3:15-3:30 Break 3:30-4:45 Phenomena Importance Ranking Tables (PIRTS)» Description of PIRTS (presentation)» Example Guardrail PIRT (presentation)» Discussion of roadside hardware PIRTS (group discussion)» Example 820C Vehicle PIRT (presentation)» Discussion of vehicle PIRTS (group discussion) 4:45-5:00 Summary and Recommendations (group discussion) 5:00 Adjourn

3 Phenomena Importance Ranking Tables A PIRT is a table that lists all the phenomena that a model is expected to replicate. Each phenomena in the PIRT should be validated or verified as appropriate. There will be a PIRT for: Each vehicle type in Report 350 (i.e., 820C, 2000P, etc.) Each type of roadside hardware (i.e., guardrail, sign support, guardrail terminal, etc.)

4 EXAMPLE: G4(1S) GUARDRAIL PIRT Phenomenon number Is this phenomena included in the model? Verification or validation score for this phenomena. Zero is best. List of Phenomena Rank Phenomena Included Component Verification Component Validation 1 Rail geometry Y Post geometry Y Rail material properties Y 0-4 Post material properties (quasi-static) Y Post material properties (dynamic) Y 0-6 Post-rail connection failure Y Post foundation response (e.g., post-soil response) Y Rail boundary conditions (e.g., Anchor stiffness) Y 0-9 Snagging Y 0-10 Rail rupture in the impact region Y 0-11 Post rupture in the impact region Y 0-12 Spacer geometry Y 0-13 Spacer material properties Y 0-14 Rail-splice connection geometry (Impact Region) Y 0 15 Rail-splice response (Impact Region) Y Rail-splice connection geometry (non-impact N - - Region) 17 Rail-splice response (non-impact Region) Y 0 Component Validation/Verification Level 16/17=94 Component Validation/Verification Score 0.96 Score from RSVVP or similar The component V/V level is the percent of phenomena included in the model. 100 = all phenomena are included. The component V/V score is the average score for all phenomena included in the model. Zero is the best score.

5 Process Flow chart based on ASME V&V Each phenomenon listed in the PIRT is what ASME V&V calls a reality of interest. We are validating or verifying each phenomena that we expect the model to replicate. Phenomenon of interest Mathematical Model Mathematical Results Acceptable Agreement? True Phenomena True Solution No Yes Enter Phenomenon Score Proceed to next Phenomenon

6 Example: G4(1S) PIRT Each phenomena score must be traceable to some documentation: A paper or report in the literature. Some experiments/simulations performed by the modeler. Unresolved Issues: Should the rank be a weight used in calculating the score or just an identifier? Will model developers do this?

7 Example: G4(1S) PIRT W-beam Geometry was verified by comparison to geometric properties given in the AASHTO-ARTBA-AGC, A Guide to Standardized Highway Barrier Hardware, American Association of State Highway and Transportation Officials, Washington, D.C. (1995) W-beam Actual Model Score Geometric Properties Area (in 2 ) Height (in) Thickness (in) (2.67mm) Depth (in) Ixx (in 4 ) 2.403? - Iyy (in 4 ) Composite/Average Score

8 Example: G4(1S) PIRT Guardrail Post Geometry was verified by comparison to geometric properties given in the Manual of Steel Construction LRFD, American Institute of Steel Construction, W6x9 Actual Model Score (W150x13.5) Area (in 2 ) Depth (in) Web Thickness (in) Flange Width (in) Flange Thickness (in) Ixx (in 4 ) Iyy (in 4 ) Composite/Average Score 2.9

9 Example: G4(1S) PIRT W-Beam Material Properties were verified from the literature. Wright and Ray measured static and dynamic properties of several roadside hardware material including W-beam rail and W6x9 steel posts. Wright, Amy E. and Malcolm H. Ray, Characterizing Roadside Hardware Materials for LS-DYNA3D Simulations, Report No. FHWA-RD , Federal Highway Administration, McLean, Virginia, Density (Mg/mm3) 7.86E-9 Young s Modulus (MPa) 200E3 Poisson s Ratio 0.33 Yield Stress (MPa) 415 Strain rate effects Cowper-Symonds model with D=100.4 s -1 and p=4.9 Plastic Strain at Failure 0.66 Increments of Plastic Strain Increments of Yield Stress (MPa)

10 Example: G4(1S) PIRT Dynamic Guardrail Post Material Properties were verified from the literature. Wright and Ray measured static and dynamic properties of several roadside hardware material including W-beam rail and W6x9 steel posts. Wright, Amy E. and Malcolm H. Ray, Characterizing Roadside Hardware Materials for LS-DYNA3D Simulations, Report No. FHWA-RD , Federal Highway Administration, McLean, Virginia, Density (Mg/mm3) 7.86E-9 Young s Modulus (MPa) 200E3 Poisson s Ratio 0.33 Yield Stress (MPa) 315 Strain rate effects Cowper-Symonds model with D=100.4 s -1 and p=4.9 Plastic Strain at Failure Increments of Plastic Strain Increments of Yield Stress (MPa) The validation score of 3.7 was based on comparison of load-time history data from simulation and test results where a guardrail post was loaded in a three-pointbending configuration in the weak direction of the post

11 Example: G4(1S) PIRT Post-Rail Connection Failure was validated by performing quasi-static laboratory tests and comparing the test results to the FE model of the connection. The validation score of 3.7 was based on average percent error of the four test cases for modified-model-3 regarding maximum force required to fail the connection. It should also be noted that all tests and simulations were conducted in a quasi-static manner for this study and, thus, the effects of strain-rate on material properties must also be considered for the analysis of guardrail impact performance.

12 Example: G4(1S) PIRT Post-Foundation Model was validated using the subgrade reaction approach in which the post is supported by an array of uncoupled springs. The post-soil model was validated with full-scale bogie impact tests of the W150x13.5 post embedded in soil that were conducted at the MwRSF. The tests involved a 946-kg rigid nose bogie vehicle impacting the posts at 550-mm above grade perpendicular to the flange of the post (i.e., strong direction of post). The score of 3.5 was based on an average % error between the test and simulation regarding maximum deflection (which is representative of total energy dissipated) and average force.

13 Example: G4(1S) PIRT Guardrail Terminal / Boundary Conditions were verified by comparing the response of a submodel of a guardrail anchor system to a previously developed and validated model of the MELT guardrail terminal. The finite element model of the Modified Eccentric Loader Terminal (MELT) developed by Patzner et al. was used to develop a force-displacement relationship for the rail-end springs. The MELT model was converted to a straight anchor, and a displacement-time history was applied to the finite element nodes on the end of the w-beam rail to generate a tensile force in the w-beam. The resulting deformation of the anchor model is shown in Figure 4.39 from Plaxico s Thesis and the force-displacement response during loading is shown in Figure Although the model was not validated for this particular loading case, the values obtained from the model were used to develop the forcedisplacement properties for the non-linear springs that may be used as boundary conditions in the modified G4(1S) guardrail model. Based on the fact that the MELT terminal model was validated through full-scale crash testing, the response of the modified version of that model used in this study was given a Verification Score of 0.

14 Example: G4(1S) PIRT Spacer Block Geometry and Material Properties were verified based on drawings of the routed wood blockout for the modified G4(1S) guardrail system. The material properties for the wood were calibrated with full-scale pendulum tests of guardrail posts as described in Plaxico, C.A., G. S. Patzner and M. H. Ray, Finite Element Modeling of Guardrail Timber Posts and the Post-Soil Interaction, Transportation Research Record No. 1647, Paper No , National Cooperative Highway Research Program, Washington, D.C., The properties defined in that study were consistent with those provided in the Wood Handbook.

15 Example: G4(1S) PIRT Rail-Splice Response (Impact Region) was validated based on a comparison between the results of two laboratory tests and a component FE model. Since the results of the F.E. simulation fall everywhere within the bounds of the two tests, the splice model in the non-impact region of the guardrail was given a validation score of zero.

16 Draft Roadside Hardware PIRTS Longitudinal Barriers Phenomena Included? Verified? Validated? 1 Overall geometry 2 Rail geometry 3 Post geometry 4 Rail material properties 5 Post material properties 6 Post-rail connection failure 7 Post foundation response (e.g., post-soil response) 8 Rail boundary conditions (e.g., Anchor stiffness) 9 Snagging 10 Rail rupture in the contact region 11 Post rupture in the contact region 12 Anchor/end conditions 13 Spacer geometry 14 Spacer material properties 15 Connector components geometry

17 Draft Roadside Hardware PIRTS Guardrail Terminals Rank Phenomena Included? Verified? Validated? 1 Overall geometry 2 Rail geometry 3 Post geometry 4 Rail material properties 5 Post material properties 6 Post-rail connection failure 7 Post foundation response (e.g., post-soil response) 8 Rail boundary conditions (e.g., Anchor stiffness) 9 Snagging 10 Rail rupture in the contact region 11 Post rupture in the contact region 12 Anchor/end conditions 13 Spacer geometry 14 Spacer material properties 15 Connector components geometry

18 Draft Roadside Hardware PIRT Crash Cushions Rank Phenomena Included? Verified? Validated? 1 Overall geometry 2 Rail geometry 3 Post geometry 4 Rail material properties 5 Post material properties 6 Post-rail connection failure 7 Post foundation response (e.g., post-soil response) 8 Rail boundary conditions (e.g., Anchor stiffness) 9 Snagging 10 Rail rupture in the contact region 11 Post rupture in the contact region 12 Anchor/end conditions 13 Spacer geometry 14 Spacer material properties 15 Connector components geometry

19 Draft Roadside Hardware PIRT Breakaway Hardware Rank Phenomena Included? Verified? Validated? 1 Overall geometry 2 Rail geometry 3 Post geometry 4 Rail material properties 5 Post material properties 6 Post-rail connection failure 7 Post foundation response (e.g., post-soil response) 8 Rail boundary conditions (e.g., Anchor stiffness) 9 Snagging 10 Rail rupture in the contact region 11 Post rupture in the contact region 12 Anchor/end conditions 13 Spacer geometry 14 Spacer material properties 15 Connector components geometry

20 Vehicle Model PIRTS 820C and 1100C Rank Phenomena Included? Verified? Validated? 1 Overall geometry 2 Mass and inertial properties 3 Rotating wheels/tires 4 Frontal structure (i.e., compare to NCAP test) 5 Frontal structure (i.e., compare to off-set frontal test) 6 Side structure (i.e., compare to FMVSS 214 test) 7 Suspension system (i.e., symmetric bump test) 8 Suspension system (i.e., asymmetric bump test) 9 Steering (i.e., Ackerman angles) 10 Snagging edges (i.e., hood, door, etc.) Wheel assembly damage and failure (e.g., A-arm 11 deformations) 12 Failing Tires

21 Vehicle Model PIRTS 2000P and 2270P Rank Phenomena Included? Verified? Validated? 1 Overall geometry 2 Mass and inertial properties 3 Rotating wheels/tires 4 Suspension system (i.e., symmetric bump test) 5 6Suspension system (i.e., asymmetric bump test) 6 Snagging edges (i.e., hood, door, etc.) 7 Frontal structure (i.e., compare to NCAP test) 8 Side structure (i.e., compare to FMVSS 214 test) 9 Failing tires 10 Wheel assembly damage and failure (e.g., A-arm deformations) 11 Steering (i.e., Ackerman angles)

22 Vehicle Model PIRTS 8000S Rank Phenomena Included? Verified? Validated? 1 Overall geometry 2 Mass and inertial properties 3 Suspension system (i.e., symmetric bump test) 4 Side structure (i.e., compare to FMVSS 214 test) 5 Rotating wheels/tires 6 Snagging edges (i.e., hood, door, etc.) 7 Frontal structure (i.e., compare to NCAP test) 8 Steering (i.e., Ackerman angles) 9 Failing tires

23 Vehicle Model PIRTS TT Rank Phenomena Included? Verified? Validated? 1 Overall geometry of Tractor 2 Overall geometry of Trailer 3 Mass and inertial properties of Tractor 4 Mass and inertial properties of Trailer 5 Rotating wheels/tires 6 Suspension system performance (i.e., symmetric bump test) 7 Suspension system failure 8 Geometric accuracy of the major structural components (e.g., truck frame-rails) 9 Material assignments and characterization for major structural components 10 Snagging edges (i.e., hood, door, etc.) 11 Steering (i.e., Ackerman angles) 12 Kingpin failure 13 Failing tires 14 Frontal structure 15 Side structure

24 Meeting Agenda 1:00-1:15 Introductions/Kick-off (Roger Bligh) 1:15 2:45 Calculating validation/verification metrics» Description of the RSVVP program with examples (presentation)» Comparison of identical crash tests (presentation)» Discussion about shape-comparison metric calculations (group discussion) 2:45-3:15 Subject Mater Expert Opinions» Description on the SME activity (short presentation)» Distribute SME worksheets to the group (group activity)» Hand in SME worksheets 3:15-3:30 Break 3:30-4:45 Phenomena Importance Ranking Tables (PIRTS)» Description of PIRTS (presentation)» Example Guardrail PIRT (presentation)» Discussion of roadside hardware PIRTS (group discussion)» Example 820C Vehicle PIRT (presentation)» Discussion of vehicle PIRTS (group discussion) 4:45-5:00 Summary and Recommendations (group discussion) 5:00 Adjourn