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Hy I must check if a structure under applied load goes in buckling with f.e.a. nastran. I did a long time back, so I need help to remember the right way to post-process the results. The f.e.m. is very complex, I have the complete wing. The major problem that I have is to understand in the case...

I'm sizing a fitting of civil aircraft, primary structure. I've started with hand calculation, considering the fitting as a rigid body and I've compared the axial stress with Ftu and Fty (if compression) obtaining Reserve Factor Rf. Then comparing the acting shear with Fsu I obtained the...

I've to model a honeycomb structure to analyse its in NASTRAN. I'm able to model laminated composite but not to model honeycomb. I've a task. I've to use a solid 3D for the core and CQUAD4 for the fabric top/bottom facesheets. I've the mechanical property of the fabric and the core. I'm using...

Let em know the meaning of this table and in which way that table can help me to build a good fem

I'm modelling a wing with longitudinal spar and transv ribs For the flange rib/skin bolted joint I don't know if it's better to use: 1) the CBUSH (PBUSH: K1,K2,K3,K4,K5 high and K6=0 with 3 normal to PSHELL) 2) the RBE2at each fastener location I have seen same model with solution 1 and...

Building the fine f.e.m. of a wing structure, I'm modelling longitudinal spars and transv. ribs using 2D elements. All the spars are continuus while the ribs are cutted, I mean each rib is composed of two or three part along chord wise. It's in the real structure as in the f.e.m.. In the real...

hi I have to model a structure in fabric. The fibers are stiched: +/- 45 and 0/90. How do I built a single fabric ply in Patran? thanks

hi in a buckling analysis (sol 105) the model is in the following unit: inch, lbf (consistent). Could you confirm (or not) that is mandatory to define the material density? Could you confirm (or not) that I have to insert the card: PARAM,WTMASS,0.00259 ? thanks

I have to do a fitting analysis. In particular I'm interested in the joint analysis. The fitting has a clevis, bushings and it is connected to the lug of a second fitting with a pin. Does anyone know in which JAR/FAR I read about the misalignment? thanks

Hi I'm running a fea of a composite skin. The composite is a laminated composite with ply in 0,45,-45,90 direction. The skin is modeled with CQUAD. I've to check the strain. May I obtain the strain at each ply? Is it available in *.F06 ? thanks

Hello I'm working on the sizing of the aircraft structure in composite, I'm in the phase of preliminary load. I did a first size at Ultimate Load considering the strain check and the buckling check, all the MS>0: The post-buckling isn't allowed under Ultimate Load. Now I'm considering the Fail...

Hello I'm running a buckling analysis of a wing main box. The skin, rib and spar have been modeled with CDUADs. My I use the offset for the CQUAD? Does the offset cause an error in evaluation of the eigenvalue?

Hi in my model I have two parallel plates (modeled along their own middle surface), to aviod the compenetration (deformed structure under load) I have to insert the GAP element. In the real structure the two plates are jointed with same fasteners, they are face to face I mean. I have never used...

I'm analysed an aircraft structure. Calculating the MS=Ftu/f-1, I obtained a negative margin, so my supervisor suggested me to consider the allowable equal to 1.5XFtu. What does it mean?

I'm sizing a clip. My you help me to calculate the prying effect on the bolts and flange? A shear load has been applied to the first flange while the second flange is jointed with three bolt to a rigid body.