Mandrel assembly and method of using the same

A mandrel assembly receivable by an installation tool to operate on an opening in a workpiece, the assembly comprising:

• an inner elongated rod having an engagement section, a first section extending from the engagement section, a second section extending from the first section, an expansion section extending from the second section, and a head section coupled to the expansion section with a shoulder formed therebetween;
• and
• an outer member having a first end and a second end, the outer member slideably receivable by the expansion section of the inner elongated rod and axially movable along the inner elongated rod between a first position and a second position, the outer member configured to be in a first configuration for passing through the opening when in the first position and a second expanded configuration for expanding the opening when in the second position, the second end of the outer member engageable with the shoulder of the inner elongated rod to limit axial movement of the outer member relative to the inner elongated rod in a first direction, the outer member having a plurality of longitudinal slots, each longitudinal slot extending through a radial thickness of the outer member and only partially through a longitudinal length of the outer member, wherein a first set of the plurality of longitudinal slots extend from the first end of the outer member and a second set of the plurality of longitudinal slots extend from the second end of the outer member.

An installation system to operate on an opening in a workpiece, the assembly comprising:

• an inner rod having an engagement section, a central section extending from the engagement section, a cylindrical expansion section, a stepped transition section between the expansion section and the central section, and a head section coupled to the expansion section with a shoulder formed therebetween;
• a biasing member slideably receivable by at least a portion of the central section of the rod;
• and
• an outer member having a first end and a second end, the outer member receivable by the expansion section of the rod, the first end of the outer member configured to operate with the biasing member, the second end of the outer member engageable with the shoulder of the head section of the rod to limit axial movement of the outer member in a first direction relative to the inner rod.

A method of using a mandrel assembly, the method comprising:

• placing an outer member of the mandrel assembly in proximity to an opening of a structural workpiece, the outer member slideably moveable on an inner elongated rod between a first position and a second position, the first position corresponding to an expansion section of the inner elongated rod;
• slideably moving the outer member away from a head section of the inner elongated rod into the second position;
• moving at least a portion of the outer member completely through the opening in a first direction;
• after the outer member is moved through the opening in the first direction, forcing the outer member towards the first position to radially expand the outer member using a biasing member positioned between the outer member and an installation tool coupled to the mandrel assembly;
• and
• applying a pulling force to the mandrel assembly to forcibly pull the expanded outer member in a second direction generally opposite the first direction and back through the opening to cause a maximum circumference section of the outer member to radially expand a region of the structural workpiece around the opening to induce fatigue enhancing compressive stresses in the region of the structural member.

A method of using a mandrel assembly to expand an opening in a workpiece, the opening extending from a first side of the workpiece to a second side of the workpiece, the method comprising:

• positioning a mandrel assembly on a first side of the workpiece, the mandrel assembly comprising an elongated rod and an outer member coupled to the elongated rod;
• moving a head of the elongated rod and at least a portion of the outer member in a first configuration through the opening in a first direction to the second side of the workpiece;
• causing the portion of the outer member to extend outwardly from the second side of the workpiece to expand from the first configuration to a second configuration while the mandrel assembly extends through the opening, the outer member in the second configuration having an outer circumference that is greater than a circumference of the opening;
• and
• after expanding the outer member, moving the mandrel assembly in a second direction generally opposite the first direction such that the outer member physically contacts and radially expands the opening of the workpiece.

A mandrel assembly comprising:

• radial expansion means for radially expanding a region around an opening in a structural workpiece, the radial expansion means having a first position and a second position, the first position occurring when a maximum outer circumference of the radial expansion means is larger than the opening, the second position occurring when the maximum outer circumference of the radial expansion means is sized to fit within the opening in a first direction;
• means for slideably supporting the radial expansion means, the means for slideably supporting including a stepped, tapered section adapted to cause expansion of the radial expansion means;
• and
• means for moving the radial expansion means towards the first position while at least a portion of the radial expansion means is on an access side of the structural workpiece and while the radial expansion means is on an opposite side of the structural workpiece, the means for moving permitting the radial expansion means to move into the second position when the radial expansion means is moved through the opening.