Hot forging method and apparatus

1. A joining apparatus for hot forging first and second workpieces together, wherein the first workpiece is provided with a deformable rivet and the second workpiece is provided with an aperture sized to receive the deformable rivet, the apparatus comprising:

• an assembly fixture for supporting the first and second workpieces to be joined with the deformable rivet of the first workpiece extending through the aperture in the second workpiece;
  
  a resistance heating power supply having a pair of power output terminals for providing power output, one of which being in electrical communication with the first workpiece;
  
  a hot forging electrode connected to the other one of the resistance heating power supply power output terminals and movable relative to the deformable rivet;
  
  an actuator affixed to the hot forging electrode for shifting the hot forging electrode into and out of engagement with the deformable rivet;
  
  a pressure regulator cooperating with the actuator for varying a force exerted by the hot forcing electrode on the deformable rivet;
  
  a transducer having an output indicative of position of the hot forging electrode to determine rivet deformation; and
  
  a controller cooperating with the transducer, the pressure regulator, and the resistance heating power supply, wherein the controller regulates the power output of the resistance heating power supply as a function of rivet deformation and regulates the force exerted by the hot forging electrode on the deformable rivet when the hot forcing electrode reaches a predetermined position to ensure that the deformable rivet properly deforms.