TRACC papers at the 8th European LS-DYNA® Users ConferenceThe research and development performed by the Computational Structural Mechanics staff has resulted in two papers that were presented at the 8th European LS-DYNA® Users Conference, Strasbourg, France May 23-24, 2011:
Modeling of Cone Penetration Test Using SPH and MM-ALE Approaches
by Ronald F. Kulak and Cezary Bojanowski
AbstractThe American Society of Association Executives (ASAE) Soil Cone Penetrometer Standard (S313.2) is designed
to characterize general soil mechanical conditions. Its results are used predominantly for comparative purposes.
Variations of this test are used for in-situ determination of the geotechnical engineering properties of soils
and delineating soil stratigraphy.
This paper presents a comparison between experimentally obtained results of cone penetration test with results from
LS-DYNA®/MPP simulations performed on a high performance cluster computer. The previously reported experiments
(conducted by USDA-ARS National Soil Dynamics Laboratory, Auburn, AL, USA) were performed on Norfolk Sand.
These experiments show the variation in results for test conducted under identical conditions. In the LS-DYNA simulations,
the soil was modeled using the material model MAT_005 Soil and Crushable Foam. Two approaches were used to represent
the soil: a hybrid approach that combined Lagrange and Smoothed Particle Hydrodynamic (SPH) methods and
the Multi Material Arbitrary Lagrangian - Eulerian (MM-ALE) method.
The vertical resistance force versus penetration distance of the penetrometer cone was compared to the experimental results.
A close match between numerical results and experimental data was obtained in the study for the Norfork Sand. The response
simulated using the two numerical approaches were almost identical. A sensitivity study revealed that the penetrometer force
was most sensitive to the soil density followed by sensitivity to a failure surface parameter.
Link to complete paper
Roof Crush Resistance and Rollover Strength of a Paratransit Bus
by Cezary Bojanowski, Bronislaw Gepner, Leslaw Kwasniewski, Christopher Rawl and Jerry Wekezer
Paratransit buses constitute a special group of vehicles in the US due to their smaller size, two-step assembly process,
and their use for complementary services to the regular scheduled transit routes. Due to their uniqueness these buses lack
national crashworthiness standards specifically dedicated to the paratransit fleet. Several states in the US adopted the
quasi-static symmetric roof loading procedure according to the standard FMVSS 220 for testing the integrity of the
paratransit buses. However, as many researchers point out, the dynamic rollover test according to UN-ECE Regulation 66
(ECE-R66), which was approved by more than forty countries in the world, (excluding the US), may provide more realistic
assessment of the bus strength.
This paper provides comparison of the numerically assessed strength of the paratransit bus according to the two standards in explicit FE simulations using LS-DYNA®/MPP. The FE model used in this study was previously validated through comparison
of its simulated behavior with response of the bus in the full scale rollover test conducted at the Florida Department
of Transportation testing facility (Tallahassee, FL, USA, 2010).
The results show that the final assessment of the bus crashworthiness from both procedures can be divergent. Although
the tested bus passes the quasi-static FMVSS 220 test, the same bus fails the dynamic rollover procedure of ECE-R66 test.
While the paratransit fleet is outnumbered by the regular transit buses, and experimental testing of the buses seems to be
prohibitively expensive to local manufacturers, the FE simulations provide viable insight into the bus strength.
Link to complete paper
For further information: Ronald F. Kulak or Cezary Bojanowski