I have modeled a 3D aircraft wing in ansys apdl. There are 8 airfoils in the geometry. I need to change the mass moment of inertia of those sections using a point mass attached to the section. I think mass 21 element can be of help but dont know how to incorporate that in the section to change mass moment of inertia to the desired value. I need to change mass distribution for modal analysis.
Thank you!
I think it is quite easy. This can be done while selecting the type of element you want. In your case it is MASS21. While entering in the command prompt for MASS21 when you type ET,1,21 you will begin to see the command prompt prompting you for other parameters named KOP1,KOP2,KOP3 etc. These are nothing but Keyoptions. For your case enter like this:
ET,1,21,0,0,0. Setting KEYOPT 3 to 0 will define 6 DOFs. Now to enter your desired mass and mass moments go to Real Constants from the preprocessor menu and you can simply enter the values in GUI easily. Just remember for your concentrated mass ANSYS takes average of the masses in 3 directions so if your mass is 1 Kg you have to enter 1 Kg for each of the mass along X,Y and Z directions so the average becomes 1 Kg which is the mass you want. I hope this helps.
Could you please visit https://scholar.google.com.my/ and key-in your keywords, InsyaAllah you will get some information about your question.
I think it is quite easy. This can be done while selecting the type of element you want. In your case it is MASS21. While entering in the command prompt for MASS21 when you type ET,1,21 you will begin to see the command prompt prompting you for other parameters named KOP1,KOP2,KOP3 etc. These are nothing but Keyoptions. For your case enter like this:
ET,1,21,0,0,0. Setting KEYOPT 3 to 0 will define 6 DOFs. Now to enter your desired mass and mass moments go to Real Constants from the preprocessor menu and you can simply enter the values in GUI easily. Just remember for your concentrated mass ANSYS takes average of the masses in 3 directions so if your mass is 1 Kg you have to enter 1 Kg for each of the mass along X,Y and Z directions so the average becomes 1 Kg which is the mass you want. I hope this helps.
Thanks a lot of the solution, it was of good help.
But I still have following problems:
1. The airfoil section is already defined as shell element with some thickness and density.
Now I need to add a point mass of specific value such that the overall mass moment of inertia of the section attains the desired value.
Also I have data of the mass moment of inertia about elastic axis and not CG. I need to match those values.
As I understand, mass 21 is defined on a node and not at a section.
How to find the node at which this mass 21 element can be attached to get this result?
2. When we keep KEYOPT 3 to 0, I need to define all three values of I, which I dont have.
I just have value of Ixx. What to define for other inputs?
3. How to get the value of mass moment of inertia about any specific axis (not origin or CG)
Hi, regarding your new problems I am quite confused about the first problem becuase I am not able to visualize, the way I see it, due to the unsymmetrical nature of the airfoil it could be quite difficult to identify the specific node you want. About the other problems I want to ask if ANSYS gives any error message when you only give Ixx value and leave the other I values void. Meanwhile please go to this link, http://mostreal.sk/html/elem_55/chapter4/ES4-21.htm. It could be of good help.
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