Indice
Lecture Notes
Shared terminal lab
Videos
Various stuff
Reference L-shaped cross section, to verify the coupled bending formulas: maxima worksheet, Oxy and G12 oriented MSC.Marc/Mentat linear models. Large rotation, animated hiE lowE models, gif animation.
Hex20profile model
- Wall midcurve as in hex20profile_ffcd24_v000.mfd.
- Wall thickness 2mm.
- Wall scale local reference system: direction 1 (red), axial; direction 2 (green) in cross section, along the wall; direction 3 (blue) normal to the wall.
- Adhesive layer thickness 0.5 mm, elastic isotropic material with E=1000 MPa, ν=0.3.
Soap film analogy for torsion
A Phoney monocoque chassis
Models:
Sway bar kit. Inertial elements kit.
For other models, refer to the ~/_shared
directory within x2go-cdm.ing.unimore.it
.
Properties
Suspension link trusses
Solid circular beam sections, ø12mm, aluminum. Essentially rigid with respect to other chassis structures.
Rear framework
Hollow circular section beam, aluminum.
Main structure: outer diameter ø40mm, wall thickness 1.8mm.
Stiffeners: outer diameter ø30mm, wall thickness 1.2mm.
Composite monocoque
Thicker backbone: 1.8mm aluminum sheet, 25.4mm aluminum honeycomb 3003, density 5.2 lb/ft^3 (hex-3003-td.pdf), 1.8mm aluminum sheet.
Thinner panels: 1.8mm aluminum sheet, 6.35mm same aluminum honeycomb, 1.8mm aluminum sheet.
Frontal shock absorber support plate: provisionally as thinner panels, to be defined based on shock.
Sway (anti-roll) bar
outer diameter ø25mm, wall thickness 2mm, extremely stiff (Super-alloy Z, E=E_steel*1e4
, nu=0.3
); it may be mechanically isolated at need by deactivating one of the connecting elements to the wheel hub carriers.
Such a “deformable but extremely stiff” linkage modeling should be discouraged in favor of an actual kinematic constraining – i.e. an MPC, since excessive stiffness badly impacts the system matrix condition number (or the integration time step, in the case of explicit dynamic simulations); nonetheless, it allowed for a very straightforward implementation.
Inertial elements modeling
The following spreadsheets are used in defining the equivalent rectangular cuboids for each inertially relevant rigid body: engine, wheel assemblies. The driver inertia is modeled through an 80 kg steel bar spanning roughly from the sternum to the pelvis.
Frontal crash absorber collapse loadcase (inertia relief)
At the element faces belonging to the crash_absorber_bearing_area
set (an approx. 155×320 mm area at the front bulkhead), a 25 psi = 0,172 MPa distributed pressure is applied which is due to the honeycomb absorber crushing (see datasheet).
How to set a damped response
Notes on the imposed disps, harmonic response
xxxxx
Buckling
Sparse material
Mindlin plane elementary modes, as shown in 2023-04-18 lesson.
Patch test for the plate element maxima worksheet, mentat model, reference paper from literature.
RBE3 connector: kinematics, moment distribution; RBE2 vs. RBE3 demonstrator model, screenshot.
Dynamics related stuff
On the relevance of constraining in dynamic analyses back view side view relevance of (improper) constraints on the dynamic behaviour of a structure. Design is reliable in actual operational conditions (link). Added constraints stiffen up the structure, thus increasing natural frequencies. However, a 0 Hz rigid body mode natural frequency may rise to a finite value due to added positioning constraints; the associate natural mode may be excited in resonance by dynamic loads.
Poor man dynamic response animated view
MSC.Mentat procedure for creating poor man harmonic response animations
MSC.Mentat procedure for creating poor man natural mode animations
Structural damping references
structural_damping_values_jdstevenson.pdf
damping_cross-reference_and_material_properties.pdf
f_orban_damping_of_materials_and_members_in_structures.pdf
tom_irvine_damping_in_bolted_and_welded_joints.pdf
estratto vol. 2, sezione 8 di Soovere, J., and M. L. Drake. Aerospace Structures Technology Damping Design Guide.LOCKHEED-CALIFORNIA CO BURBANK, 1985.