Kekuatan Lelah Baja Struktur pada Lingkungan Kelembaban Tinggi

Abstract

The present paper describes the effect of high humidity environment to the fatigue strength of structural steels such as TEW6582 and EMS45. Fatigue tests were conducted on cantilever-type rotating bending fatigue testing machines in controlled relative humidity 70%, 75%, 80%, 85%, and 90% in room temperature. Test specimen is made based on ATSM E466. The rotation of the shaft is 887.5 rpm to rotate the test specimen. Data are presented in the form of S-N curve, Fatigue Strength vs pct RH, corrosion diameter, cracking length and the figure of the surface shape of the specimen after cracking is obtained from the result of SEM. The result of the research shows that fatigue strength of TWE 6582 and EMS 45 steel declines at 70% - 90% relative humidity. The declined fatigue strength of TEW 6582 steel is about 26% and the declined fatigue strength of EMS 45 steel is about 16.1%. The declined fatigue strength is caused by the formation of corrosion pit in the steel surface in the high relative humidity environment. The higher the relative humidity, the more and greater the cracks, which increase the stress concentration in the surface of the specimen. The cracking begins to be seen at 85% relative humidity with 200x enlargement using SEM and at 90% relative humidity the cracking increasingly lengthens which becomes the unity of some formed corrosion pits. Structural steel with high tensile strength has a tendency of declining greater fatigue strength than the steel with medium tensile strength in the high relative humidity environment.