How to implement definite integral on Boundary integration variables

Dear All,

I am trying to integrate the nr unit vector along a sphere on 2D axial symmetric model. My aim is to find force acting on the sphere and when I type to the boundary integration variable, nr*2*pi*r, it gives me wrong number in r-direction.

nr is changing wrt pi. I need to define a definite integral which change from 0 to pi and pi to two pi. How can I do that?

Thank you,

Best Regards,

SA