Probly can find a HUCK site online
The swaging process has been described above.
Last I looked, the classic Huckbolt is manufactured to a length longer than the final intended grip.
The shaft of the bolt is reduced in diameter at the intended end, where the shaft is serrated- like threads but not continuous- many parallel circumferential ridges.
The 'nut' part is swedged on by hydraulically pulling the tail of the bolt, and the stub breaks off in tension near the face of the nut. That breaking-off provides a proof test of the installation as well.
That's the basics of the invention- a tightly compressed joint with a 'nut' that can't rotate off. The same performance as a heated and hammered rivet with no need for heating or bucking. Any 'shear pin' behavior is an entirely different question.
AND
the MClink spokesman on tv was saying the energy absorbing tech worked
BS
Fortunately that function was not mobilized. It requires the end[s] of the carbody to crush up to several feet without allowing telescoping- remember Volvo autos and the unibody construction . By crushing, deceleration time is lengthened [the brickwall is softened] while kinetic energy is transformed into permanent deformation of a lot of metal and some heat.