Open PhD position at the Chair of Mechanics, Faculty of Civil and Geodetic Engineering, University of Ljubljana.

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Young and motivated researcher with a strong passion for science. I have hands-on experience in genomic bioinformatics and am eager to contribute to cutting-edge research in genomics.

I am solving a model in Abaqus with column and beam connections. However, there are frictional or adhesive contact properties between the column and beam. Step-1 is frequency analysis and step-2 is earthquake acceleration analysis.

The problem I encounter in this model is as follows: it provides tie connection as if the interface properties defined for contact do not exist. Even though I used different types of definitions for the solution, the same result was found. These types of definitions (general contact, general contact and assigning the properties I requested with the fake contact, using the find contact option).

How should the settings in frequency analysis be? The model does not have to work as a whole single part. Because the column and beam are frictionally connected. I see the solution in the appropriate settings in step-1 and step-2.

I would be very grateful if you could help me with this issue.

Hi all,

Is there anyone who have the experience of solving nonlinear eigenvalue problem? I meet a special question.

The question is to solving the eigenfunction:

H(x) x=a x

where a is a real number, x is an eigenvector while H(x) is a matrix depended by x. The aim is to find a vector x and H(x) satisfying the equation which make the eigenvalue a minimum. In this question, H is far from a Hermitian in most case. And this question is not similar to conventional Kohn-Sham equation where most of the eigenvectors contribute to the construction of H. In contrast, in present question, H(x) may have many eigenvectors but, it depends on one of its eigenvector (x) only.

The method I try is self-consistent field method, i.e. determine a "temporary" H by a random or guess x, and by solving this temporary H a new x is obtained, and from new x a new H can be determined, etc. Currently, a major problem is that the matrix is not Hermitian, and therefore no real eigenvalue and corresponding eigenvector can be selected to define new "H". Since the target is to find a real number a and vector with real number elements, I hope that any temporary H can be composed by real number as well.

Does anyone have some idea about solving such a question? Any suggestion will be appreciated.

Thanks!

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Hi,

I am trying to export elemental stiffness matrix from Abaqus by adding the following lines in the input file "*Element Matrix Output, Elset=Set-1, File Name=myMatrix, Frequency=1, Output File=User Defined, Stiffness=Yes" for 4-noded linear quad element. I got stiffness matrix but the size of this matrix is 12x4 while it should be 8x8. Could you please explain how the Abaqus is writing the elemental stiffness matrix? Please check attached output for your reference.

Hello! I need to extract the mass and stiffness matrices for a model with the following problem size:

P R O B L E M S I Z E

NUMBER OF ELEMENTS IS 249191

153326 linear line elements of type T3D2

84141 linear hexahedral elements of type C3D8R

102 linear line elements of type B31

11613 linear quadrilateral elements of type S4R

NUMBER OF NODES IS 267444

NUMBER OF NODES DEFINED BY THE USER 267240

NUMBER OF INTERNAL NODES GENERATED BY THE PROGRAM 204

TOTAL NUMBER OF VARIABLES IN THE MODEL 837207 (DEGREES OF FREEDOM PLUS MAX NO. OF ANY LAGRANGE MULTIPLIER VARIABLES. INCLUDE *PRINT,SOLVE=YES TO GET THE ACTUAL NUMBER.)

The properties are input as mass density, and I believe they will be used to generate a consistent mass matrix.

Here's the input file code I used: ** Global Mass and Stiffness matrix *Step, name=Export matrix *MATRIX GENERATE, STIFFNESS, MASS, VISCOUS DAMPING, STRUCTURAL DAMPING *MATRIX OUTPUT, STIFFNESS, MASS, VISCOUS DAMPING, STRUCTURAL DAMPING, FORMAT=coordinate

I have the following questions regarding my problem: