# cdm.ing.unimo.it

### Strumenti Sito

wikifemfuchde2019:lez_2019-05-20
mentat2013.1 -ogl -glflush

Inertia relief and dynamic loadcases theory

Embodiment of the vector shape functions constituting the $\underline{\underline{S}}$ matrix columns.

*FSAE-like chassis*

model at the end of the previous lesson

Inertial elements

model as at the end of today's lesson (inertia relief crash deceleration loadcase)

Notes:

The pedagogical model proposed does not include sway/antiroll bars, that are instead a critical element for torsional stiffness loadcases.

In particular, torsional stiffness should be evaluated in both the limiting cases of

• rigid springs, disconnected sway bars;
• disconnected springs, rigid sway bar.

This second loadcase, which is usually neglected, is however relevant for sizing the sway bar support areas on the chassis structure.

• Static test: torsional stiffness;
• Front, right wheel bump loadcase (inertia relief);
• 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).
• Dynamic modal response;
• Dynamic harmonic response: vertical harmonic load at the front, right wheel, 1-100 Hz range, sampled at 0.25Hz resolution ((100-1)*4+1 = 397 steps);

### Connectors

RBE3 link kinematics, in a nutshell:

• in the standard configuration, the centroidal C node dof.s are set as dependent, whereas the other $P_i$ nodes in the distribution maintain their independent dof. characterization;
• a $q_i$ weight is associated to each $P_i$ node of the distribution, uniformly allotted by default;
• the C centroidal node rigidly roto-translates with the distribution COG. G;
• the distribution COG. G translational motion is defined by the weighted average $P_i$ nodes translations;
• the distribution COG. G rotational motion is defined based on the momentum of the $P_i$ nodes translations.

wikifemfuchde2019/lez_2019-05-20.txt · Ultima modifica: 2019/05/28 08:25 da ebertocchi