Method for reducing the fatigue crack growth rate of cracks in the aluminum alloy fuselage skin of an aircraft structure

摘要

A method and apparatus for reducing the fatigue crack growth rate of cracks in the aluminum alloy fuselage skin of aircraft structures. A fatigue crack is identified, the crack having a tip defining the direction of crack propagation. Temperature differentials are produced between a narrow strip of the skin and portions of the skin adjacent to this narrow strip. The narrow strip extends from the crack tip to a predetermined distance forward the crack tip. The temperature differentials produced between the narrow strip and adjacent unheated portions of the aircraft skin are sufficiently high so that the expansion due to heating causes plastic flow to occur in the heated strip. The plastic flow results in a residual tensile stress which acts in the direction of crack propagation when the system is returned to a normal service temperature. This residual tensile stress is of a sufficient magnitude to effectively retard the crack growth rate.