Rotatable multi-pin apparatus, and process for friction driven stitch welding and structural modification of materials

A process of solid-state joining using a welding apparatus with a head, the head including a ring-shaped rotatable shoulder, a first pin and a second pin, both pins extending downwardly from the shoulder and not integrally connected to the shoulder, the process comprising:

• coupling a first workpiece to a table, the workpiece including an upper surface;
• disposing a second workpiece on the upper surface of the first workpiece to define an interface between the first and second workpiece;
• defining an X direction on the table wherein a Y direction is perpendicular to the X direction and parallel to the plane of table, and a Z direction defined as perpendicular to the plane of the table;
• rotating each of the first pin and the second pin about a separate, spaced non-parallel axis of rotation with a gap defined therebetween, the axes of the first and second pins being inclined toward each other to intensify the shear strain of the interface within the gap;
• rotating the ring-shaped shoulder disposed about the first and second pins relative to the first and second pins in their entirety, the pins rotating about non-parallel axes of rotation relative to the shoulder with the ring-shaped shoulder bearing downwardly against the first and second workpieces;
• penetrating the first and second pins through the second workpiece and partially into the first workpiece;
• and
• moving the head along a path that contains the interface in a back and forth stitching motion between the first and second workpieces, with the shoulder bearing downwardly against the second workpiece such that the first pin and second pin mix the first and second workpieces, to form a solid state bond between the first and second workpieces.

A process of solid-state grain refinement of materials using a multi-pin apparatus with a head, the head including a ring-shaped rotatable shoulder, a first pin, a second pin, and a third pin, all pins equidistant from one another and extending downwardly from the shoulder and not integrally connected to the shoulder, the process comprising:

• coupling a workpiece to a table, the workpiece including an upper surface;
• defining an X direction, wherein a Y direction is perpendicular to the X direction and parallel to the plane of table, and a Z direction defined as perpendicular to the plane of the table;
• rotating each of the first pin, the second pin and the third pin about a separate, spaced non-parallel axis of rotation with a gap defined therebetween, the axes of the first and second pins being inclined toward each other to intensify the shear strain of the interface within the gap;
• rotating the ring-shaped shoulder disposed about the first and second pins relative to the first and second pins in their entirety, the pins rotating about non-parallel axes of rotation relative to the shoulder with the ring-shaped shoulder bearing downwardly against the first and second workpieces;
• penetrating the first pin and the second pin through the upper surface of the workpiece to a desired depth;
• moving the head along a path or series of paths in a back and forth stitching motion on the workpiece predetermined to cover a desired region of surface and interior;
• and
• deforming and subdividing the grain structure of workpiece by said moving process.

A process of creating a high shear rate in a workpiece using a head including a ring-shaped rotatable shoulder, a first pin and a second pin, both pins extending downwardly relative to the shoulder and not integrally connected to the shoulder, the process comprising:

• coupling the workpiece to a table;
• rotating each of the first pin and the second pin about a separate, spaced non-parallel axis of rotation in the same direction, wherein the first pin has a diameter, wherein a gap between the first pin and the second pin is less than the diameter, the axes of the first and second pins being inclined toward each other to intensify the shear strain of the interface within the gap;
• rotating the ring-shaped shoulder disposed about the first and second pins relative to the first and second pins in their entirety the pins rotating about non-parallel axes of rotation relative to the shoulder with the ring-shaped shoulder bearing downwardly against the first and second workpieces;
• and
• moving the head through the workpiece in a back and forth stitching motion, with the shoulder bearing downwardly against the workpiece and the first and second pin disposed in the first and second workpieces;
• wherein the first pin rotates in a direction opposite the direction of the second pin in the gap to create a high shear rate of the workpiece within the gap.