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  mentat2013.1 -ogl -glflush 

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Inertia relief and dynamic loadcases theory

{{ :wikifemfuchde2019:dispensa_2018_v2019-05-20.pdf |}}

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

{{ :wikifemfuchde2019:monoelem_piastra_motielementari_singolidof.mfd |}}

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***FSAE-like chassis***

model at the end of the previous lesson

{{ :wikifemfuchde2019:monocoque_chassis_2019_v004.mud |}}


**Inertial elements**

{{ :wikifemfuchde2019:monocoque_chassis_2019_inertial_elements_alone.mud |}}

{{ :wikifemfuchde2019:inertially_equivalent_cuboid_engine.ods |}}

{{ :wikifemfuchde2019:inertially_equivalent_cuboid_wheel_assemblies.ods |}}


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

{{ :wikifemfuchde2019:monocoque_chassis_2019_v005.mud |}}

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** 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.

==== Loadcases ====

  * Static test: torsional stiffness;
    * preliminary suspension stroke motion test ({{:wikitelaio2016:telaio_monocoque_comeimportato_tutorial_optistruct.mud|original Optistruct tutorial version}} m( );
    * rigid spring or rigid anti-roll bar?
  * 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. 155x320 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 {{ :wikitelaio2017:plascore_crushlite.pdf |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.

{{:wikipaom2015:cinematica_rbe3.png?300|}}

{{:wikipaom2015:cinematica_rbe3_v1.pdf|sorgente ipe}}