Anurekha:

Here are my responses to your questions, I hope that they are helpful

Q1.    Is there any method in ansys where you can define the pressure sweep to
be given to the diaphragm, so that one can obtain a graph between deflection at
a particular node and pressure?

A1: Yes, there are several ways to define a pressure sweep.  You can ramp apply
a pressure over a time step or you can define the pressure in a table and then
apply it as a table load.  TIME is used as a counter in ANSYS.  It can be actual
clock time or any other counter.  A common technique is to set TIME equal to the
applied load, so that when you plot results versus time, you are actually
plotting time versus the applied load.  For example, if you want to apply a
pressure sweep from 0 to 100 MPa.  You could specify the pressure of 100 MPa and
the TIME at the end of the load step to be 100.  You could then apply the
pressure over some number of substeps (e.g, 10). The applied pressure at TIME 10
would then be 10 MPa and the pressure at TIME 50 would 50 MPa, and so on.

Q2.     How to address the contact problem. what I did was that I constrained
the displacement in the z direction to a maximum of the gap between the
electrodes, is it right

A2:  That method should work, but why don't use just use surface-to-surface
contact elements?

Q3.I want to find out the variation of area of the touched portion with
pressure. The approach followed in the paper is tot draw a contour map of the
touched are and to find the are the spacing between the nodes is to be known. My
main difficulty is to compute the touched from the node co-ordinate. how to know
the spacing between the nodes. Is there another method of knowing the spacing.
this information is also helpful if I have to know the w(x,y), deflection at a
position (x,y) from the edges or centre as it is needed to compute the
capacitances the equation of the capacitance is

c=integrationover surface (dxdy/(d-w(x,y))

that means if I have to know the capacitance , I have to know the deflection at
different x,y, can I get the listing in tabular form

A3:  It is easy to find the distance between nodes.  The NDIST command will
calculate the distance between nodes and store it in a parameter.  For example,
the command n12 = ndist(1,2) will calculate the distance between nodes 1 and 2
and store it in parameter n12.  It is also easy to find any calculated result at
a node.  For example, the command nuy1 = uy(1) will store the calculated Y
displacement in parameter nuy1.  You can also combine these commands.  For
example, uy123 = uy(node(1,2,3)) will store the Y displacement at the node
located closest to x=1, y=2, z=3, and store it in parameter uy123.  You need to
review the APDL Guide available in the Help System, particularly, Appendix B
concerning the GET functions.

It is more difficult to find a result at an arbitrary location.  If possible,
you should have a node at each location where you want a result.  If you cannot
have nodes at all locations. then you need to create a path with one of the path
points at the desired location (PPATH command).


Regards.

Daniel Shaw
ANSYS, Inc.