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--- wikiffcd2022:start [2022/05/30 17:03] – [A Phoney monocoque chassis] ebertocchi
+++ wikiffcd2022:start [2023/01/19 10:16] (versione attuale) – ebertocchi
@@ Linea 156: / Linea 156: @@
 ==== 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}}).
+==== How to set a damped response ====
+<hidden Click here to expand>
+In order to include a small degree of structural damping (eg. 1% of the critical value) into a MSC.Marc/Mentat harmonic response calculation, the following steps may be followed:
+  * enter the menu ''MAIN -> MATERIAL PROPERTIES -> MATERIAL PROPERTIES'';
+  * preemptively define a modulating table 1/ω
+    * menu ''TABLES'', ''NEW -> 1 INDIPENDENT VARIABLE''
+    * define ''NAME'' as ''modulate_stiffmatmult''
+    * set //Indipendent variable v1// ''TYPE'' as ''frequency''
+    * define //table// through ''FORMULA'' and type ''1/pi/v1'', i.e.  $g(f)=\frac{1}{\pi f}$
+  * go back to ''MAIN -> MATERIAL PROPERTIES -> MATERIAL PROPERTIES'' by hitting ''RETURN'';
+  * select the various model materials, and for each of them enter the submenu ''STRUCTURAL -> DAMPING'' and activate ''DAMPING'';
+  * leave alone the ''MASS MATRIX MULTIPLIER'' value (0 is ok, otherwise some "structural" damping will be associated to rigid body motions),
+  * define a ''STIFFNESS MATRIX MULTIPLIER'' equal to the desired fraction of the critical value, namely ''0.01'',
+  * set a frequency modulating function, namely //TABLE//, by hitting the ''TABLE'' button on the right of the //stiffness matrix multiplier// value;
+  * select the just defined ''modulate_stiffmatmult'' table as the modulating one, hence hit''OK'' and ''OK'' again to return back at the material properties menu
+  * in this way, I defined damping as a function of the $\alpha$ e $\beta$ coefficients introduced by the Rayleigh proportional damping model, with zero $\alpha$ and hence no contribution of the mass matrix. In particular $\zeta = \frac{1}{2}(\frac{\alpha}{2 \pi f}+2 \pi f \beta)$ with $\alpha=0$ and $\beta= 0.01 \cdot g(f)=\frac{0.01}{\pi f}$, from which $\zeta=0.01$ as desired.
+  * enter the ''MAIN -> JOBS'' menu and create a copy of the undamped harmonic response job by hitting the ''COPY'' top left button and by setting a new job name;
+  * enter the job ''PROPERTIES'' menu, and reach the ''ANALYSIS OPTIONS'' submenu; activate the  ''COMPLEX DAMPING'' options within the //dynamic harmonic// section, and then exit with''OK''
+  * Enter the ''JOB RESULTS'' submenu and deactivate ''Stress'', ''Equivalent von Mises stress''
+  * substitute them with the //AVAILABLE ELEMENT SCALARS//
+    * '' Equivalent Real Harmonic Stress '', layers ''MAX & MIN''
+    * '' Equivalent Imag Harmonic Stress '', layers ''MAX & MIN''
+    * the //REAL HARMONIC// e //IMAG HARMONIC// stress resultant equivalents for the beam elements, ''DEFAULT'' layer, and the ''Beam Orientatio Vector''
+  * insert from the //AVAILABLE ELEMENT TENSORS// block
+    * '' Real Harmonic Stress '', layers ''ALL''
+    * '' Imag Harmonic Stress '', layers ''ALL''
+  * run the simulation as usual with ''RUN -> SUBMIT''
+  * open the post file as usual with ''OPEN POST FILE (RESULTS MENU)''
+  * The deformed shape may be visualized //according to a given phase// within the oscillation cycle (see also the ''DEFORMED SHAPE SETTINGS'' menu); in the absence of damping the fase was limited to the 0° and 180° values, cases these that may be represented with the bare variation in sign of the stress and displacement components to be monitored.
+  * Please note that the real component has a 0° phase ($\cos(\omega t)$ modulation) whereas the imaginary component has a 270° phae ($-\sin(\omega t)$ modulation).
+  * Please also note that in resonance conditions the **imaginary component** becomes dominant and reaches the peak values, whereas the real component vanishes (resonant response is in fact ~90° out of phase with respect to the real, 0° excitation).
+  * Lets e.g. collect the displacement in $z$ direction of the node at the center of the excited wheel contact area:
+    * enter the POSTPROCESSING ''RESULTS'' menu, with opened t16 result file, and proceed within the ''HISTORY PLOT'' submenu
+    * define the locations for the response sampling with ''SET LOCATIONS'', hence click on the desired node[s], and finalize with ''END LIST''
+    * define the range of the sub-increments to be collected with ''INC RANGE'', and then entering at the prompt ''0:1'' [enter], ''0:397'' [enter], ''1'' [enter], as the sampling beginning, end and step.
+    * proceed with the definition of collected response diagrams by entering th ''ADD CURVES'' menu, and then''ALL LOCATIONS'' (a single location has been selected); select the ''Frequency'' global variable as the abscissa, and the ''Displacement Z Magnitude'' nodal variable as the ordinate. The ''FIT'' scales the axes to contain all the sample points.
+    * By hitting ''RETURN'' I may return to the HISTORY PLOT menu, where the label density may be reduced  ''SHOW IDS'' from '1' to '10'; by entering a  '0' value labels are hidden.
+  * response peaks are now finite (they were theoretically unbounded in the absence of damping), and peaks disappear in correspondence of natural modes that are weakly coupled with the exciting force. In the absence of damping, bounded response at resonance is obtained for **strictly uncoupled** natural modes only.
+</hidden>
+===== Buckling =====
+[[https://cdm.ing.unimo.it/dokuwiki/wikifemfuchde2020/buckling|Buckling (FFCD 2020 course)]]
+{{ :wikiffcd2022:400mm_supported_bar.mfd |}}, versioni
+{{ :wikiffcd2022:400mm_supported_bar_c.mfd |c}},
+{{ :wikiffcd2022:400mm_supported_bar_d.mfd |d}},
+{{ :wikiffcd2022:400mm_supported_bar_e.mfd |e}},
+{{ :wikiffcd2022:400mm_supported_bar_f.mfd |f}},
+{{ :wikiffcd2022:400mm_supported_bar_g.mfd |g}}.
 ===== Sparse material =====
@@ Linea 220: / Linea 273: @@
 ===== Exercises =====
 [[https://cdm.ing.unimo.it/dokuwiki/wikifemfuchde2020/examexercises]]
+===== Exam turns =====
+[[https://cdm.ing.unimo.it/dokuwiki/restricted/turni_esame_pt_pasm_paom]]