How can I determine the overall stiffness matrix for a structure using Ansys?

In summary, Ansys APDL can determine the stiffness matrix for any structure, which is the overall stiffness in every direction for any arbitrary loading and boundary condition. To find the stiffness for a particular set of conditions, you need to apply boundary conditions to the model. Slides 22-32 of this paper provide a useful overview of the process. To extract the stiffness matrix and mass matrix from Ansys Classic, a method from the internet suggests building the model, creating a substructure, defining master DOFs, and solving for LS. However, to obtain the overall/lumped/equivalent stiffness matrix for the structure, similar to those calculated using energy methods, it is not clear how to do so using Ansys.
  • #1
Mohamed_Wael
23
0
Hi,
I know that Ansys APDL can determine the stiffness matrix for any structure, I would like to know if I can determine the overall stiffness for this structure or not if yes how can I do this? thanks.
 
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  • #2
The stiffness matrix is the overall stiffness for the structure, it is the stiffness in every direction for the structure for any arbitrary loading and boundary condition. To find the stiffness for a particular set of conditions, you need to apply boundary conditions to the model.

This paper has a useful overview on slides 22-32: http://www.engr.uvic.ca/~mech410/lectures/FEA_Theory.pdf
 
  • #3
Thanks a lot for your help.
Let me clarify my question, I can use ansys to extract the stiffness matrix for a structure using this procedure

I want to find stiffness and mass matrix from ANSYS Classic. I found a method from internet. It is as follows.
1.Build your model normally. No need to apply boundary conditions
2. solu->New analysis->Substructuring
3.Sol->Analysis options and give your substructure name
4.solu->Master DOFs->Define->Pick All->All DOF->OK
5.solu->solve LS
6. Click UM->List->Other->Superelement Data Set the name of your *.sub file, the name you defined in step 3, and set KOPT=Full Contents, then click OK
7.ANSYS will list super element data. Scroll down to:GLOBAL DOF SET NODES, LABELS=.Next ANSYS lists the order of the DOF vector for your global stiffness matrix.I have tried it and it works pretty good but now I want to get the overall/lumped/equivalent stiffness matrix for the structure like the one we get from the energy methods but using ansys. Do u know how ?
 

What is a stiffness matrix in Ansys?

A stiffness matrix in Ansys is a square matrix that represents the stiffness of a structure or system. It contains information about the stiffness of each element within the system and how they are connected to each other.

How is a stiffness matrix calculated in Ansys?

A stiffness matrix in Ansys is calculated using the finite element method. This method divides a structure into smaller elements and uses mathematical equations to determine the stiffness of each element. These stiffness values are then combined to create the overall stiffness matrix for the system.

What is the significance of a stiffness matrix in Ansys?

A stiffness matrix in Ansys is significant because it is used to solve structural and mechanical problems. It provides information about the behavior of a system under various loads and boundary conditions, allowing engineers to make informed decisions about the design and performance of a structure.

Can a stiffness matrix in Ansys be modified?

Yes, a stiffness matrix in Ansys can be modified. This can be done by changing the properties of the elements within the system or by applying constraints and loads to the structure. Modifying the stiffness matrix can help engineers optimize the design of a structure to meet specific requirements.

Are there any limitations to using a stiffness matrix in Ansys?

While a stiffness matrix is a powerful tool, there are some limitations to using it in Ansys. For example, it assumes that the structure is linear and elastic, and does not take into account non-linear behaviors such as plasticity or large deformations. Additionally, it requires a significant amount of computing power and resources for larger and more complex systems.

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