Ultrasonically Assisted Self-Piercing Riveting

Abstract

A method for installing a self-piercing rivet by introducing acoustic (ultrasonic) vibrational energy is provided. The method includes positioning multiple workpieces between a blank holder and a die, applying ultrasonic vibrations to locally soften the workpieces and driving, using a press tool, the self-piercing rivet into the workpieces, causing the self-piercing rivet to deform in a radially outward direction, thereby joining the workpieces together without thermal processing and without permanent alterations to the microstructure of the workpiece materials.

1 . A method for installing a self-piercing rivet, the method comprising:
 providing a self-piercing rivet tool including a punch and a die;   positioning a plurality of workpieces between the punch and the die;   applying ultrasonic vibrations to the plurality of workpieces between the punch and the die to locally soften a region of the plurality of workpieces; and   driving, using the punch, a self-piercing rivet into the softened region of the plurality of workpieces, and causing the self-piercing rivet to deform in a radial-outward direction to join the plurality of workpieces together substantially at ambient temperature.   
     
     
         2 . The method of  claim 1  wherein the ultrasonic vibrations are indirectly applied to the plurality of workpieces through vibration of a portion of the self-piercing rivet tool. 
     
     
         3 . The method of  claim 1  further including clamping the plurality of workpieces between a blank holder and the die. 
     
     
         4 . The method of  claim 1  further including providing an ultrasonic transducer to apply the ultrasonic vibrations to at least one of the plurality of workpieces. 
     
     
         5 . The method of  claim 1  wherein applying ultrasonic vibrations imparts vibrations in a direction perpendicular to a surface of the plurality of workpieces. 
     
     
         6 . The method of  claim 1  wherein applying ultrasonic vibrations imparts vibrations in a direction parallel to a surface of the plurality of workpieces. 
     
     
         7 . The method of  claim 1  wherein applying ultrasonic vibrations imparts rotational vibrations about an axis that is normal to a surface of the plurality of workpieces. 
     
     
         8 . The method of  claim 1  wherein applying ultrasonic vibrations is performed prior to the step of driving the self-piercing rivet. 
     
     
         9 . The method of  claim 1  wherein applying ultrasonic vibrations is performed concurrently with the step of driving the self-piercing rivet. 
     
     
         10 . The method of  claim 1  wherein applying ultrasonic vibrations is performed prior to and concurrently with the step of driving the self-piercing rivet. 
     
     
         11 . A self-piercing rivet tool comprising:
 a punch and a die which are operable to drive a self-piercing rivet into a plurality of workpieces positioned between the punch and the die, the self-piercing rivet having a hollow leg extending from a head, the die having a cavity; and   an ultrasonic transducer operable to locally soften a region of the plurality of workpieces positioned between the punch and the die, wherein the hollow leg of the self-piercing rivet is deformed in a radial outward direction when driven into the plurality of workpieces in an axial direction to join the plurality of workpieces together.   
     
     
         12 . The self-piercing rivet tool of  claim 11  wherein the ultrasonic transducer is coupled to the plurality of workpieces through an ultrasonic horn. 
     
     
         13 . The self-piercing rivet tool of  claim 11  wherein the ultrasonic transducer causes the plurality of workpieces to oscillate in a direction perpendicular to the axial direction. 
     
     
         14 . The self-piercing rivet tool of  claim 11  wherein the ultrasonic transducer causes the plurality of workpieces to oscillate in a direction parallel to the axial direction. 
     
     
         15 . The self-piercing rivet tool of  claim 11  wherein the ultrasonic transducer imparts rotational oscillations in the plurality of workpieces about the axial direction. 
     
     
         16 . A method for installing a self-piercing rivet, the method comprising:
 providing a self-piercing rivet tool including a punch, a blank holder, and a die;   clamping a plurality of workpieces between the blank holder and the die, the plurality of workpieces including an upper sheet and a lower sheet;   applying ultrasonic vibrations to the plurality of workpieces in the region between the blank holder and the die to locally soften the plurality of workpieces; and   driving, using the punch, a self-piercing rivet into the softened region of the plurality of workpieces in an axial direction and causing the self-piercing rivet to deform outwardly in a radial direction to join the plurality of workpieces together.   
     
     
         17 . The method of  claim 16  wherein the ultrasonic vibrations are indirectly applied to the plurality of workpieces through vibration of a portion of the self-piercing rivet tool. 
     
     
         18 . The method of  claim 16  wherein applying ultrasonic vibrations imparts vibrations in a direction perpendicular to the axial direction. 
     
     
         19 . The method of  claim 16  wherein applying ultrasonic vibrations imparts vibrations in a direction parallel to the axial direction. 
     
     
         20 . The method of  claim 16  wherein applying ultrasonic vibrations imparts rotational vibrations about the axial direction.