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Thanks Erik!! Very clear!!

Erik, Thanks for your answer but would you please provide more detailed explanation on this? I am not really sure what you are saying here.

Could anyone explain to me what is the definition of element force output in Nastran with ELFORCE card? I have to know how it is caluculated. Thanks!!!

According to the Nastran manual, this value is computed as diagonal term of stiffness matrix divied by diagonal term of D matrix in LDL decomposition, and if MAXRATIO is greather than user specified value (e.g.1.0e8), matrix is said to be singular. Would anyone kindly tell me how to interpret...

Please anyone tell me how to interpret the linear buckling results if it gives me negative buckling factor, meaning 1st eigenvalue is negative?

Thanks. Does anyone know any website where I can download c++ source code for shell element?

I am interested to know the flow in Nastran to calculate the stress at upper face and lower face for shell element. Here, I am only talking about bending state because stress at membrane state is same throughout thickess direction. In my understanding by reading FE book, it is, first get stress...

I am interested to know the flow in Nastran to calculate the stress at upper face and lower face for shell element. Here, I am only talking about bending state because stress at membrane state is same throughout thickess direction. In my understanding by reading FE book, it is, first get stress...

Thanks corus!!

Thanks Nagi for the comment. The model is shell and as you said that there are both bending and membrane loading. What I want to know is that is there any way e.g. by looking at some stress value, to clealy determine which load is dominating in particular case.

When we look at FEA results, is there any way to cleary determine what is dominating the results e.g. it is bending or shear? I am performing FEA and wants to know if it is bending dominating or shear by looking at output, stress.

For Frequecny response analysis, the euqation to solve when direct method is used is defined like this. [ -w^2*[M]+iw[C]+[K] ]U(w)=F(w) w:given frequecny Obviously this is the complex equation and I want to know what kind of techniqu or algorithm that commerial software, Nastran, uses to solve...

According to some dynamics book, it says the 2nd differential equation can be transformed to just a simple algbraic equation by applying Laplace transformation and I know how it works and what is the beneit of doing that in terms of the ease of caluculation. However what I want to know is the...

The issue about handling shell to solid connection came up in this forum a quite few times and understand that this is because of stiffness matrix being singular. Could someone explain what exactly causes matrixt to be singular and how the use of MPC prevent this from happening?

I think electricpete is correct from the point view of vibration analysis. But let's say we have some 2nd differential equation to solve, ex) x"+2x'+5x=f(x), and forget about whether this is vibration study or not, but it is just a mathematical equation. Then my question is that the same...

Hi, As to forced frequcncy analysis, theoretically it is to solve 2nd differential equation and the solutoin would be summation of general solution and particular solution, which I can understand exactly as this behavior is just the sum of transient and steady phonenomenon. However apart from...

I have been using Nastran for many years and know that there is no rotational stiffness about its normal axis to it when using QUAD element(I know QUADR has drilling stiffness). Would anyone please tell me what is a theoretical reason why a rotational stiffness is not involed in traditional...

There is a mesh independent weld element called CWELD in Nastran. I am interested in knowing what kind of formulation is used to handle such a element that is not connected to any surrounding nodes.

Thanks corus for your help. Does maximum shear stress occur at the outer fiber even for pure compression loading case? In my model that I described initially, loads are applied in longitudianl direction so that it behaves like compression case. I thought in this case stress =P/A, so as long as...

I ran a topology optimization for rectangular parallelepiped with axial load on it in which objective function is to minimize compliance while constraining its volume. This gave me the structure where there is a big hole inside thoughout its axial direction and material is placed onto its outer...