i m mechanical engg. student , i m seeking to design a such type shaft coupling which gets disengaged at over loading , but one thing ther , no use of fluid like in fliud coupling should be there
Well, check out the internet, you'll find a number of different types.
There are couplings based on clutches, shear pins, with retracting mehanisms,...
What are your requirements? How much torque? At what speed? What are the size constraints? In what environment it must operate (media, temperature, pressure, must seal something, ...)? Must be automatically recoverable, must require user action, or acts like a "fusible" link? What are the end connections? Must have vibration dampening characteristics? Must allow misalignments? Must withstand impacts? Must withstand bend/side loads?
Answer these questions, and you'll be closer to your objective.