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wikifemfuchde2019:lez_2019-05-20 [2019/05/20 15:45] – ebertocchiwikifemfuchde2019:lez_2019-05-20 [2019/05/28 08:25] (versione attuale) – ebertocchi
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 +  mentat2013.1 -ogl -glflush 
 +
 +----
 +
 +Inertia relief and dynamic loadcases theory
 +
 +{{ :wikifemfuchde2019:dispensa_2018_v2019-05-20.pdf |}}
 +
 +----
 +
 +Embodiment of the vector shape functions constituting  the $\underline{\underline{S}}$  matrix columns.
 +
 +{{ :wikifemfuchde2019:monoelem_piastra_motielementari_singolidof.mfd |}}
 +
 +----
 +
 +***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 |}}
 +
 +
 +----
 +
 +model as at the end of today's lesson (inertia relief crash deceleration loadcase)
 +
 +{{ :wikifemfuchde2019:monocoque_chassis_2019_v005.mud |}}
 +
 +----
 +
 +** 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}}