This units belongs to the fourth part of the course, focussed on magnet design. Here we discuss the pattern of the electromagnetic forces acting on a dipole and on a quadrupole coil.
We first give an analytical estimate of the accumulation of prestress in the midplane for dipoles and quadrupoles based on sector coils. We prove that for dipoles the azimuthal accumulation of stress on the edge of the aperture is simply given by a product of field, current density and magnet aperture. A geometric factor, has to be added to account for the stress increase inside the coil. We then discuss the relation between magnetic pressure and stress, showing that the relation that holds for solenoids is valid for the stress in the coil heads and for radial stress in the transverse plane.
After a brief introduction on mechanical properties, we discuss the preload paradigm, that requires that the coil is always under compression.