Influence of Exposure to an Aggressive Environment on Cyclic Fatigue Response and Life of an Alloy Steel

Abstract

Corrosion or environment-induced degradation often occurs in structural steel as an electrochemical process which leads to gradual loss in mass over a period when subjected to prolonged exposure to an aggressive environment. Immediate effects of this environment-induced degradation, also referred to in industry circles as corrosion, includes a progressive reduction of the cross section, which in turn has a detrimental influence on stiffness and load carrying capacity of the components in a structure, such as a bridge, a stiffened panel or a building. Due to its high strength, low alloy A572 Grade 50 steel is a potentially viable candidate for a wide range of applications in the construction industry. However, like in other high strength alloy steels, A572 is vulnerable to the effects of degradation-induced by the environment owing to its chemical composition. This paper discusses the details of tests conducted to determine the fatigue properties of A572 steel after inducing uniform environment-induced degradation or corrosion. Flat (rectangular dog-bone shaped) specimens, conforming to specifications detailed in ASTM E8 standard, were used in this study. A technique that was developed by the ASTM and General Motors Corporation (GM) [called GMW14872] for a controlled corrosion process based on use of the spray technique was used to induce accelerated corrosion on selected test specimens in an environment chamber. Stress-controlled high cycle fatigue tests were conducted on the corroded test specimens and compared with the as-new, uncorroded counterpart.

Keywords

• a572 steel
• corrosion
• gmw14872
• orientation
• microstructure
• fatigue life
• degradation.