Parametric study on the variability of opening load determination

This paper examines the crack growth properties of a popular aircraft alloy, 2024-T351, whilst immersed in Corrosion Preventative Compound (CPC). Comparison tests were conducted in laboratory air and in distilled water. The results were very startling. The effect of the CPC was to increase the crack propagation rate to a value higher than that seen in distilled water. The loading regime maintained stress intensity within a narrow range, minimizing non-linear effects—resulting in very consistent results with minimal scatter. The accurate measurement of crack lengths in the different environments was facilitated by the use of the dynamic specimen compliance technique. Analysis conducted included a fractographic survey of the fracture surfaces in an attempt to discover the fatigue mechanism responsible for the results. Several possible mechanisms are proposed. It is vital that the mechanism responsible is identified so that the possible detrimental effect of CPC on fatigue life can be assessed vis-a-vis its beneficial effect in controlling corrosion.