Method and apparatus for friction stir welding

A tool for forming a friction stir weld joint in a workpiece, comprising:

• a rotatable pin having first and second ends and defining a stirring portion therebetween structured to frictionally engage the workpiece so as to at least partially form the friction stir weld joint;
• a rotatable first shoulder defining an aperture therethrough structured to slidably receive said first end of said pin;
• and
• a second shoulder defining an aperture structured to receive said second end of said pin such that said pin extends between said first and second shoulders, said second shoulder being in rotatable communication with said pin, at least one of said first and second shoulders has a surface defining at least one raised portion structured to frictionally engage the workpiece so as to at least partially form the friction stir weld joint, and wherein said first and second shoulders are structured to opposingly support the workpiece during friction stir welding.

A tool for forming a friction stir weld joint in a workpiece, comprising:

• a rotatable pin having first and second ends and defining a stirring portion therebetween structured to frictionally engage the workpiece so as to at least partially form the friction stir weld joint;
• a rotatable first shoulder defining an aperture therethrough structured to slidably receive said first end of said pin;
• and
• a second shoulder defining an aperture structured to receive said second end of said pin such that said pin extends between said first and second shoulders, said second shoulder being in rotatable communication with said pin, and wherein said second shoulder defines a plurality of fins adapted to transfer heat away from the weld joint.

An apparatus for forming a friction stir weld joint in a workpiece, comprising:

• a machine having a spindle defining a rotatable inner portion and a rotatable outer portion;
• and
• a friction stir welding tool, comprising:
• a pin having first and second ends and defining a stirring portion therebetween structured to frictionally engage the workpiece so as to at least partially form the friction stir weld joint, said first end of said pin being in rotatable communication with said inner portion of said spindle;
• a first shoulder defining an aperture therethrough structured to slidably receive said first end of said pin, said first shoulder being in rotatable communication with said outer portion of said spindle;
• and
• a second shoulder defining an aperture structured to receive said second end of said pin such that said pin extends between said first and second shoulders, said second shoulder being in rotatable communication with said pin, and wherein said first shoulder is structured to rotate independently of said pin and said second shoulder.

A method of friction stir welding a workpiece, comprising:

• positioning first and second shoulders adjacent the workpiece, each of the first and second shoulders having a surface structured to frictionally engage the workpiece;
• connecting a pin to the first and second shoulders so that the pin extends therebetween, the pin defining a stirring portion structured to frictionally engage the workpiece;
• and
• thereafter, rotating the first shoulder at a first angular velocity and the pin and the second shoulder at a second angular velocity different from the first angular velocity so that at least a portion of each of the pin, first shoulder, and second shoulder frictionally engages the workpiece to thereby form a friction stir weld joint.

A method of friction stir welding a workpiece, comprising:

• positioning first and second shoulders adjacent the workpiece, each of the first and second shoulders having a surface structured to frictionally engage the workpiece;
• connecting a pin to the first and second shoulders so that the pin extends therebetween, the pin defining a stirring portion structured to frictionally engage the workpiece;
• rotating the first shoulder;
• and
• concurrently with said first rotating step, rotating the pin and the second shoulder independently of the first shoulder so that at least a portion of each of the pin, first shoulder, and second shoulder frictionally engages the workpiece to thereby form a friction stir weld joint.

A friction stir weld lap joint being formed by a rotating friction stir welding tool, comprising:

• a first structural member;
• a second structural member, said second structural member at least partially overlapping said first structural member so as to define an interface therebetween;
• and
• a friction stir weld joint joining said first and second structural members at least partially at said interface, said friction stir weld joint defining first and second portions, said first portion being mixed by the friction stir weld tool at a first angular velocity, said second portion being mixed by the friction stir welding tool at a second angular velocity to thereby form grain structures of different refinement in said first and second portions.