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A14-002

ROLL STABILITY EVENTS EMBANKMENT

Product(s): Adams/Car

Feature(s): Roll Stability Events Embankment: This example illustrates the embankment roll-over event

Directory:

Files:

Problem Statement

Rollover accidents cause many fatalities. To provide a better occupant protection the study of the rollover motion becomes important. Adams/Car now provides three rollover events. This example shows the embankment rollover event and helps you

to study the vehicle behavior when driving over a small ramp followed by travelling down an embankment and rolling over before reaching a flat ground surface. A roll over bar with varying dimensions can be mounted on the embankment surface to enforce roll-over.

Model Description

The Adams/Car Demo Vehicle model is used.

Steps for Running Example

1. Start Adams/Car, click File - Open - Assembly

2. Right-click in the Assembly Name field, navigate to Search, then choose acar_shared

3. Open MDI_Demo_vehicle.asy

4. Right-click either of the front wheels and select Modify

5. Right-click in the Property File field, navigate to Search, then choose acar_shared and select ftire_205_55R16_for_impact.tir.

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6. Select Apply, and the change is applied to both the left and right wheels

7. Repeat the previous sets for the rear wheels

8. The suspension of the demo vehicle has some weakness for this test and extreme

side forces may impact the steering of the wheels. Therefore modify the center of mass height of the body to 650.0 mm. Select Adjust - General Part Modify and change CM location relative to Part to 1500, 0.0, 650.0 mm.

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9. For stability reasons, FTire requires a maximum Solver time step (hmax) of 1e-3 s. However, due to the heavy impact on the tire hmax should be further reduced to 5.0E-004. Click on Settings Solver - Dynamics, and set the Hmax to 5.0E-004:

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10. Perform an embankment analysis, by clicking Simulate then navigating to Full Vehicle Analysis Roll Stability Events Embankment

11. Fill out the box as shown, then select OK

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The embankment road profile is based on the 3d shell road format and automatically converted to Regular Grid Road (.rgr) after start of the simulation

using cosin/roadtools. This allows for different possible combinations of rigid and soil roads with and without rollover bar.

The simulation will stop after reaching a roll angle of 88 degrees, as shown in the

Message View:

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12. To visually inspect the simulation, select Review - Animation Controls. Fill out

the box as shown and click Animation Forward

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13. Next, the rollover bar is activated and results will be compared to the simulation without rollover bar. Perform an embankment analysis, by clicking Simulate

then navigating to Full Vehicle Analysis Roll Stability Events Embankment

14. Fill out the box as shown, then select OK

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Similar as in the previous simulation, the .rdf road is automatically converted to

Regular Grid Road (.rgr) after start of the simulation using cosin/roadtools.

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As expected the maximum vehicle roll angle is reached earlier due to the rollover

bar located at 1000 mm along the embankment.

15. To visually inspect the simulation, select Review - Animation Controls. Fill out the box as shown and click Animation Forward

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16. Switch to the Adams Postprocessor by clicking Review, Postprocessing Window.

17. Visualize the roll angle, roll velocity and roll acceleration for both simulations to see the impact of the rollover bar:

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18. Next, a simulation will be performed using a soil road surface instead of a full

rigid road surface. Note that the soft soil road type options (soft soil, loose sand and lete sand)

require a Cosin ftsoil license. If a license is not available the soft soil road type options will be removed from the options menu. Click on Simulate and navigate to Full Vehicle Analysis Roll Stability Events Embankment Select a soil road for Road Type, e.g. loose sand, fill out the box as shown, then select OK.

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The rollover bar is always modelled as a rigid bar. If a soil road is selected, both embankment and lower ground plane are modelled with soil properties, the upper

ground plane is always modelled as a rigid plane.

Similar as in the previous simulation, the .rdf road is automatically converted to

Regular Grid Road (.rgr) after start of the simulation using cosin/roadtools. The following message is shown in the Solver message file commenting the Bekker soil road model:

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The simulation stops once the maximum allowed roll angle is reached:

19. To visually inspect the simulation, select Review - Animation Controls. Fill out

the box as shown and click Animation Forward

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20. To examine the roll behavior in Adams Postprocessor click on Review, Postprocessing Window.

21. Visualize the roll velocity to see the impact of the rollover bar and soil road:

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Remarks and known issues

The soft soil road type options (soft soil, loose sand and lete sand) require a Cosin ftsoil license. If a license is not available the soft soil road type options will be removed from the options menu.

Due to the heavy impact of the tires on the road it is important that:

o Parameter rim_to_road_contact_stiffn in the FTire property file is

set to a proper value (in ftire_205_55R16_for_impact.tir set to 2.0e4 N/mm)

o Parameter maximum_time_step in the FTire property file is set to 0.0001 sec and the Adams/Solver parameter hmax is set to 5.0E-004.

o The FTire property file contains enough contact elements, e.g.

number_belt_segments = 80 number_belt_bend_shape_funct = 5 number_blocks_per_belt_segm = 50 number_tread_strips = 30