how to assign a point mass to a spring

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Rana Nasser posted this 2 weeks ago

Hi Everyone,

I need to do the simulation shown in the picture below, but I couldn't assign the mass to the spring's end or start. I'm using the method in the attached video to add the spring to the structure, so is there any edit or to this method to allow assigning a point mass to the spring's end or start point? or an APDL command to do this?

 

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peteroznewman posted this 2 weeks ago

Hi Rana,

I recommend you follow the video and draw a block, make it Rigid, and use a Remote Displacement on the front face to turn it into a 1 DOF motion along the x-axis. Add a spring (K/2) to ground on each side of the block. Or just use one spring (K), since it is an idealized 1 DOF system anyway.

Adjust the density of the material for the block until you get the mass you want. Or you can add a point mass to the back face of the block and assign the difference the point mass a value of the difference between the desired mass and the current mass of the block, assuming the current mass is less than the desired mass.

Regards,

Peter

Rana Nasser posted this 2 weeks ago

Hi Peter, 

In my simulation the mass "M1" refers to the convective water mass in a water container not a real block

 

peteroznewman posted this 2 weeks ago

Hi Rana,

Okay, but if you want to study the dynamics of a mass and spring system, and you are idealizing the mass to a point mass and are idealizing the springs to linear elastic springs, then the dynamic response is the textbook case of a Mass-Spring system.  I can write the equation of motion for that, or I can build a model to simulate the response and let ANSYS numerically calculate the response.

You might want to compare the textbook Mass-Spring system to the response of a more complex system to draw analogies, or to make a 1 DOF representation of a complex system. In that case, it doesn't matter if you replace the convective mass of water with a rigid solid body, it is an idealization of the system to a 1 DOF system.

Regards,

Peter

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Rana Nasser posted this 2 weeks ago

I'm studying the dynamic response of  a water structure elements and I need to simulate the water contained in the structure. this method is a simplified to do this simulation which used in a published paper and the author used this procedure using ansys apdl 15.0 by employing mass21 and combine14 elements, and I'm trying to use this method in my regulator( water structure) model. 

the simplification procedure of the water response to a dynamic load is as shown in the pictures below

   

 

the application of the simplified method in ansys APDL   

peteroznewman posted this 2 weeks ago

Using Mechanical without any APDL commands, you need a body to add a point mass and springs to.

I don't know how to write the APDL command to create the node and assign the mass element, but I know it is possible.

Regards,

Peter

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