Damage tolerant and fail-safe (DTFS) high strength preloaded pin assembly
A fracture-resistant double shear joint including a clevis having a first end defining a first bore and a second end defining a second bore, and a reaction load member defining a third bore, wherein the first bore, the second bore, and the third bore are colinear. The fracture-resistant double shear joint can further include a first spacer positioned within the first bore, a second spacer positioned within the second bore, and a shear pin positioned within each of the first bore, the second bore, and the third bore. The shear pin may include an outer cylinder, an inner shear bolt threaded on both ends, and nuts at either end that engage the threads. The nuts may be tightened to place the outer cylinder in compression. The spacers in the first and second bore may include a low friction liner that interfaces with the outer cylinder of the shear pin. The ends of the spacers may be set back from the ends of the first and second bores (that are next to the third bore).
1. A fracture-resistant double shear joint, comprising:
a clevis comprising a first end defining a first bore and a second end defining a second bore;
a first bearing positioned within the first bore;
a second bearing positioned within the second bore;
a reaction load member defining a third bore, wherein the first bore, the second bore, and the third bore are colinear;
a first spacer positioned within the first bore and a second spacer positioned within the second bore;
a shear pin positioned within the first bore, the second bore, and the third bore, wherein the first spacer and the second spacer are configured to space the shear pin from the reaction load member defining the third bore;
a shear bolt comprising a threaded first end and a threaded second end;
an outer cylinder, wherein the shear bolt extends through an opening in the outer cylinder;
a first nut threaded onto the threaded first end of the shear bolt; and
a second nut threaded onto the threaded second end of the shear bolt, wherein an opposing force between the first nut and the second nut applies a compressive stress to the outer cylinder,
wherein the opposing force between the first nut and the second nut applies a tensile force to the shear bolt during application of the compressive stress to the outer cylinder,
wherein the first spacer is positioned between the first bearing and the outer cylinder and the second spacer is positioned between the second bearing and the outer cylinder.
2. The fracture-resistant double shear joint of claim 1 , wherein the first spacer and the second spacer each include a substrate comprising at least one of a metal and a phenolic material, and further comprise a liner comprising polytetrafluoroethylene.
3. The fracture-resistant double shear joint of claim 1 , wherein:
the first spacer is a first liner that physically contacts the first end of the clevis and a first end of the shear pin;
the second spacer is a second liner that physically contacts the second end of the clevis and a second end of the shear pin; and
the shear pin is configured to transmit loads from the reaction load member to the first liner and to the second liner.
4. The fracture-resistant double shear joint of claim 1 , further comprising:
a first pin extender that physically contacts the first nut and a first end of the outer cylinder; and
a second pin extender that physically contacts the second nut and a second end of the outer cylinder.
5. The fracture-resistant double shear joint of claim 1 , further comprising:
a first angled shoulder at a first end of the outer cylinder; and
a second angled shoulder at a second end of the outer cylinder,
wherein the first nut physically contacts the first angled shoulder and the second nut physically contacts the second angled shoulder.
6. The fracture-resistant double shear joint of claim 1 , wherein the shear bolt has a length of from 4.0 inches to 10.0 inches and a diameter of from 0.5 inches to 2.5 inches.
7. The fracture-resistant double shear joint of claim 1 , wherein the shear bolt, the outer cylinder, the first nut, and the second nut each comprise at least one of steel, a non-ferrous alloy, a nickel-cobalt-chromium-molybdenum alloy, and combinations thereof.
8. The fracture-resistant double shear joint of claim 1 , further comprising:
a cap having an opening therethrough, wherein the threaded first end of the shear bolt extends through the opening in the cap; and
a fastener, wherein the fastener extends through a lateral hole in the threaded first end of the shear bolt.
9. The fracture-resistant double shear joint of claim 8 , further comprising a sealant around a base of the cap.
10. The fracture-resistant double shear joint of claim 1 , wherein:
the first spacer is completely positioned between an upper extent and a lower extent of the first end of the clevis; and
the second spacer is completely positioned between an upper extend and a lower extent of the second end of the clevis.
11. The fracture-resistant double shear joint of claim 10 , configured such that a fracture of the shear pin results in the shear pin physically contacting, and being supported by, at least one of the first end and the second end of the clevis.