Recent content by NastranQ

Below is the relevant part of the deck which I am using: SOL 111 CEND ECHO = NONE SPC = 1 METHOD = 1 DLOAD = 10 RANDOM = 30 SDAMPING = 20 FREQ = 40 RESVEC = YES STRESS(PLOT,CRMS,NORPRINT)=ALL

Hi All, I am running a random vibration analysis on some structure and I am interested in the RMS stress. I am able to obtain it in the .op2 file by using STRESS(PLOT,CRMS,NORPRINT)=ALL, but the problem is that it also stores the stress results for the preceding frequency response analysis for...

Thank you! I think it is a limitation Hyperview has related to this.

Hello All, I am trying to plot the RMS displacement for a structure I am working on. I am using the below output request to get it out of Nastran. DISPLACEMENT(PLOT,RALL,NORPRINT)=1 Next I am importing the .op2 file in Altair's HyperView and I want to plot the RMS displacement, but it is not...

OK. Can you please send me your model ? (the one that gives 234 MPa)

Thank you very much! Seems to be close to my results. I wonder what preprocessor you are using and also what is the logic it is using to generate the Frequency function? The increments seem to be clustered around the natural frequencies? Not sure why you say I am enforcing displacement I am...

I am actually running in Optistruct which is very similar to Nastran. (more confusion) Only the header part is a bit different. I can prepare an equivalent Nastran file. In the mean time please find attached the Optistruct deck which you can use to see the dimensions and boundary conditions...

Also I am ignoring the first 2 element rows (near to the spider) when plotting the stress.

Hi, Sorry for the late reply. I am using a RBE2 spider which grabs the nodes highlighted below. The acceleration is applied at the center node.

Hi, I am using tone/mm^3 for the density units. This is why it is 7.83e-9... The BC's are cantilever beam indeed. The mode #5 is a torsional mode (see below). Are you using CBEAM/CBAR ? Maybe this is why you are not capturing that mode..

Also the diameter is 40 mm..

Not sure if the attachment went thru. See below..

Thanks again. Please see below the problem specs and also the stress results for one of the iterations I am doing. The stress seems to be stabilizing around this value (209 MPa). Also in the attached sheet I played with different frequency steps and recorded the max stress results. Please let me...

Hi Filipe, Thank you very much for your reply. I still don't have a feel for this. I am currently doing a study on a simple beam structure (hexa meshed)to try and figure out some optimum frequency increments to select. Also I am comparing the results with Ansys which seems to have a different...

Hello, This may be a basic question, but I found no obvious answer on the web or the Nastran Dynamic analysis User's guide. As stated in the Nastran Dynamic analysis user's guide the Random analysis is treated as a data reduction procedure that is applied to the results of a frequency response...