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AFM Modelling
Posted Apr 27, 2011, 5:19 a.m. EDT 1 Reply
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Hi,
I´m trying to model a mechanical contact problem. I attached here the 2D and the 3D version of it.
You have three entities:
a SPHERE that indents a
CELL that lies on a
SUBSTRATE.
The problem is parametric stationary where the parameter that varies is the value of a prescribed displacement of the indenter inside the cell. I´m interested on the raction forces of the system in the (respectively for the 2D and 3D models) y component and z component.
The two models have the same geometry and the same material properties, then the problem is solved in the same manner (therefore I would like to get the same reaction forces).
If in the two models I plot the summation of the variable solid.RFy and solid.RFz respectively over the boundaries of the sphere I don´t get the same result.
In order get the same I wrote a stange formulas on the 2D model. i.e.
(-2solid.RF/solid.d)*(pi/2)RADIUSIND*10^-6
With this I get the same of the 3D model.
now
the factor 2 is just for symmetry
solid.RF/solid.d is a factior that I found in the model library hyperelastic seal (the measure unit of this member is N/m)
(pi/2)RADIUSIND*10^-6 this is the value of a quarter of circonference of the indenter (that part where I have stored the reaction forces)
Do you think that I ´m right?
If not, what should I do?
Regards,
Giulio
I´m trying to model a mechanical contact problem. I attached here the 2D and the 3D version of it.
You have three entities:
a SPHERE that indents a
CELL that lies on a
SUBSTRATE.
The problem is parametric stationary where the parameter that varies is the value of a prescribed displacement of the indenter inside the cell. I´m interested on the raction forces of the system in the (respectively for the 2D and 3D models) y component and z component.
The two models have the same geometry and the same material properties, then the problem is solved in the same manner (therefore I would like to get the same reaction forces).
If in the two models I plot the summation of the variable solid.RFy and solid.RFz respectively over the boundaries of the sphere I don´t get the same result.
In order get the same I wrote a stange formulas on the 2D model. i.e.
(-2solid.RF/solid.d)*(pi/2)RADIUSIND*10^-6
With this I get the same of the 3D model.
now
the factor 2 is just for symmetry
solid.RF/solid.d is a factior that I found in the model library hyperelastic seal (the measure unit of this member is N/m)
(pi/2)RADIUSIND*10^-6 this is the value of a quarter of circonference of the indenter (that part where I have stored the reaction forces)
Do you think that I ´m right?
If not, what should I do?
Regards,
Giulio
1 Reply Last Post Apr 27, 2011, 7:42 a.m. EDT
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Posted:
1 decade ago
Hi
if you have a cylindrical symmetry and action going along the direction of the symmetry axis, you should rather use 2D-axi. Because 2D is for long (default mostly 1[m] in the paper direction = z ) and does not give you the cylindrical symmetry. This will give you differences (sometimes not) on the results when comparing to the true 3D model
--
Good luck
Ivar
if you have a cylindrical symmetry and action going along the direction of the symmetry axis, you should rather use 2D-axi. Because 2D is for long (default mostly 1[m] in the paper direction = z ) and does not give you the cylindrical symmetry. This will give you differences (sometimes not) on the results when comparing to the true 3D model
--
Good luck
Ivar