DyMESH Version 3

DyMESH Version 3 (Engineering Dynamics Company, 2026 HVE Forum) adds a collision model for the vehicle wheels — DyMESH Wheels — so that impact forces and moments developed at the tires/wheels are computed and fed into the vehicle dynamics. Version 3 also finalizes the user-defined third-order force-deflection stiffness described in the Collision Model chapter.

Problem statement

• DyMESH Version 2 calculated 3-D collision forces and moments only for the sprung mass (the vehicle body).
• However, significant collision forces and moments can occur during impact at the wheel(s) — e.g. an angled wheel-to-wheel or wheel-to-body strike.
• Ignoring these forces affects the collision dynamics (post-impact heading, spin, and trajectory).

Solution criteria

The wheel collision model had to:

• Calculate forces and moments from the collision at each individual wheel.
• Integrate the results directly into the equations of motion.
• Be robust, accounting for:
• Wheel shape — a round cylinder.
• Wheel location / displacement (the wheel can be moved by the impact).
• Wheel steering and camber change.
• Wheel spin (tangential friction).

Solution

The wheel model reuses the DyMESH machinery by treating each wheel as its own DyMESH body:

• Treat each wheel as an independent DyMESH object.
• Create the wheel mesh based on tire size. A cylindrical wheel mesh is built from the tire radius and width, using 80 angular increments. Wheel material stiffnesses are set to their own values — \(A\) / \(B\) of 500 / 100 for truck wheels, or 250 / 50 for passenger-car wheels — and a saturation deflection tied to the wheel half-width is assigned per vertex.
• Place transforms in front of and following the DyMESH calculation to carry the wheel's location, steer, camber, and spin into and out of the collision computation.
• The user can select individual wheels for analysis (for computational efficiency — only the wheels expected to be involved need be simulated).

Flow charts

Version 3 adds a wheel loop nested within the existing sprung-mass collision loop.

Sprung Mass loop — for each pair of vehicles:

1. Collision Test → if no collision, skip.
2. Swap Vehicles (assign Primary / Secondary).
3. Get Vehicle Matrices.
4. DyMESH (Primary, Secondary) — the body-to-body collision.
5. DyMESH Wheels (Primary, Secondary) — the wheel collisions.
6. Smooth Collision Pulse.
7. Separation Test.

Figure: Sprung Mass flow chart.

Wheel loop — for each wheel:

1. Collision? → if no, skip.
2. Get Wheel Matrices.
3. Update Wheel Mesh (apply location/steer/camber/spin transform).
4. DyMESH (Primary, Secondary) — run the contact algorithm on the wheel mesh.
5. Add Wheel Force to Sprung Mass.
6. Update Wheel Mesh Damage.
7. Calculate Wheel Displacement.

Figure: Wheels flow chart.

(updated: in the current version of HVE these steps are carried out by SIMON, which updates each wheel mesh, adds the resulting wheel forces to the sprung mass, updates the wheel-mesh damage, and computes the resulting permanent wheel displacement.)

DyMESH Wheels user interface

The wheel model is driven by three areas of the interface: the DyMESH Options, the per-wheel Set-up, and the Output vs. Time results.

DyMESH Options dialog

The DyMESH Options dialog (Options menu) contains:

• Use DyMESH (turns DyMESH on or off).
• Include Environment — also run DyMESH contact against the environment (see Wheel vs. Environment for the wheel side of this feature and the tire-model handoff).
• Force To x-y Plane — keep the DyMESH deformation direction horizontal (not applied to contact with the environment).
• Tow Vehicle / Trailer Contact — allow contact between connected vehicles.
• DyMESH Version No — Version 3 or Version 4.
• DyMESH Start Time and DyMESH Environment Start Time — when vehicle-to-vehicle and vehicle-to-environment contact detection begin.
• Search — Automatic or Set Box Size (a user-entered box size, e.g. 20.00 in).
• Force Smoothing — Version 1 and 2 or Version 3 and Later.

Figure: "DyMESH Options" dialog.

(updated: the deck shows an earlier version of this dialog, with Force Smoothing labelled Version 1 / Version 2 and a Timesteps group, and without the version, connection and start-time controls. Timesteps are now set in the Simulation Controls dialog. The low-level search and pushback settings offered on an Advanced tab in some earlier releases are fixed in the current release; see the HVE User's Manual, Options Menu, DyMESH, Fixed settings.)

Set-up (Wheels)

Each wheel is configured on the Damage tab of the Wheel Data dialog: Axle No., Side (Left / Right), Wheel is Damaged, Auto Start, Start Time, Duration (e.g. 0.1 s), and Peak Lock-up Torque. A Use DyMESH section supplies the wheel force-deflection and moment-deflection parameters:

Parameter	Example	Meaning
Max No-Damage Force	3000 lb	Force threshold below which the wheel is not permanently displaced
Displacement Rate	300 lb/in	Force per unit wheel displacement (stiffness)
Max Force	30000 lb	Saturation force
Max No-Damage Moment	3000 ft-lb	Moment threshold below which no permanent reorientation
Moment Displacement Rate	300 ft-lb/deg	Moment per unit angular change
Max Moment	30000 ft-lb	Saturation moment

Figure: "Wheel Data" dialog, Damage tab, with the Use DyMESH force/moment fields highlighted.

See also the wheel-data / wheel-displacement inputs documented in the Wheel Data dialog reference.

Output vs. time

The Key Results output reports, per wheel, the collision impulses and moments in addition to the usual kinematics and kinetics — e.g. for "Axle 1, Right": Fx Imp, Fy Imp, Fz Imp (lb) and Mx Imp, My Imp, Mz Imp (ft-lb), alongside the whole-vehicle (Kinetics) impulses. This lets the user see how much of the collision load each wheel carried.

Figure: "Key Results" output table highlighting the per-wheel impulse rows.

Wheel displacement capping (updated)

(updated: the current version of HVE adds a refinement not present in the 2026 decks. During each timestep the wheel-mesh damage update tracks the largest actual movement of any wheel-mesh vertex while in contact — the magnitude of the damaged-minus-undamaged vertex displacement, referred to below as the maximum wheel-mesh contact movement for that timestep. The permanent wheel displacement is then capped by that physical contact motion. The displacement derived from the collision force,

\[ \delta_{Wheel} = \frac{F_{Total} - F_{Const}}{F_{Linear}} \]

where \(F_{Total}\) is the collision force on the wheel and \(F_{Const}\) and \(F_{Linear}\) are the constant (no-damage) force threshold and the linear force-per-displacement rate from the wheel's damage data, is limited to no more than the maximum wheel-mesh contact movement, and the per-time-step change in the x/y wheel displacement is likewise scaled so it cannot exceed that movement. This prevents the wheel from being "bent" further than the collision physically moved it.)

Validation

Validation is described as under way, starting from the initial conceptual design (see the Dial Engineering white-paper presentation at the 2012 HVE Forum), covering vehicle-to-vehicle collisions and other configurations.

Examples

The deck shows the wheel model applied to: an intersection collision, a truck tractor, a trailer under-ride, and (memorably) monster trucks. The main technical deck additionally shows angled collisions — a Ford pickup vs. Explorer on a graded road, and the RICSAC 1 (20 mph) and RICSAC 2 (32 mph) staged tests — as sample DyMESH validations.

Figure: Angled collision, Ford pickup vs. Explorer.

Figure: RICSAC 1 (20 mph) angled collision.

Figure: RICSAC 2 (32 mph) angled collision.

Summary

• DyMESH Wheel Impact is robust.
• Clean integration into the existing vehicle dynamics model (SIMON).
• More validation is needed.
• Initially released as a Beta option, now included in the commercial release.

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Source: DyMESH Version 3 (2026 HVE Forum). Updated to match the current version of HVE.

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