Patent ID: 8863585

Claim:
An apparatus for testing reversal bending fatigue in an elongated beam, the beam having opposing first and second end portions and an intermediate portion between the first and second end portions, the beam having a longitudinal axis extending between the first and second end portions, the apparatus comprising: a first rigid arm having a load end portion, a linkage end portion, and a first opening for receiving the first end portion of the beam; a second rigid arm comprising a load end portion, a linkage end portion, and a second opening for receiving the second end portion of the beam; a linkage having a first end portion coupled to the linkage end portion of the first rigid arm and a second end portion coupled to the linkage end portion of the second rigid arm; a first bearing positioned within the first opening for allowing the beam to translate in the longitudinal direction of the beam relative to the first rigid arm; a second bearing positioned within the second opening for allowing the beam to translate in the longitudinal direction of the beam relative to the second rigid arm, the first and second bearings restricting translation of the beam perpendicular to the longitudinal direction of the beam when the beam is installed; and wherein pivoting the load ends portions of the first and second rigid arms in opposite directions causes the first bearing to exert a first bending moment on the first end portion of the beam and causes the second bearing to exert a second bending moment on the second end portion of the beam, resulting in a pure bending condition in the intermediate portion of the beam; and wherein cyclically alternating the direction of the first and second bending moments cause the intermediate portion of the beam to cyclically bend back and forth in opposite directions while remaining in a pure bending condition.