Dear eng-tip community,
I have a couple of questions regarding external superelements originated from condensating a full FE model via EXTSEOUT command.
The condensed models I typically work with (or generate) are obtained using dynamic reduction (CMS). Therefore, using SOL103 for the...
Dear Eng-tip users,
I have a question regarding the analysis of shock wave propagation problems in structures using FEM. Recently I was told that it is not possible to model shock wave propagation using implicit FEM schemes. The argument was that implicit schemes do not include this phenomena...
Hello!
I have a question about how strength should be assessed in satellites structures and their payloads. I have seen different ways of doing the task, and it is not clear to me what is right and what is wrong. Some people calculate stresses directly from dynamic loads caused by random and...
Dear All,
I have a FE model in which two of the parts touch each other but do not remain in contact all the time. The aim of the model is to estimate the stresses caused by an event defined in the frequency domain.
As a first step, I did a normal modes analysis ignoring the contact between...
Dear Eng-Tip community,
I am looking for references for the design and strength analysis of welded connections. In particular, I am wondering if there is an equivalent to the existent guidelines for systematic analysis of threaded joint (such as the German VDI2230).
I have checked some books...
Dear All,
This is a rather basic question, but it still confuses me a lot: what is the best meshing approach? Meshing everything in detail, with fillets, etc.? simplifying the geometry and removing small features? Using solid elements for everything? Using shells for thin parts?
I guess the...
Dear All,
Maybe this is a silly question, but I am getting a bit confused.
Today I was thinking about what happens if a structure is loaded with a frequency dependent load which is a combination of sines at different frequencies, all acting simulaneusly. If they are all acting...
Dear Eng-tips community,
I am running a FE analysis in Hyperworks and I have some issues with one of the model checks. In particular, when I run a free-free check analysis with GROUNDCHECK card, the resultant strain energies are above the predefined threshold, leading to a fail flag:
The...
Dear All,
I would like to ask something regarding rigid body modes. Maybe it is a trivial thing, but I don't really get it: When I create a new model, I usually run a free-free modes check as part of a set of model checks. Then, I check that there are six rigid modes with very low...
Dear all,
I am new in pyroshock analysis and I am trying to assess the stresses caused by a pyroshock in the structure a small satellite. In order to do so, I'm using NASTRAN's Shock Response Spectrum method in sol103 (with NRL method of summation) since the shock data I have is defined in the...
Dear all,
I am trying to model a 2D pin-hole problem on Patran and Nastran. I have already followed different approaches, such as using linear gap elements, rigid MPCs and sin distributed loads applied on the hole. Now, I would like to use the option "contact" that is provided with Patran, but...
