Fatigue failure of high strength steels under extreme vibrations of military standards: A comparative study

Abstract

High-strength steels are widely preferred in the design of equipment and vehicles used in the defense industry, which are mostly exposed to random vibrations with supernormal amplitudes during their service life. The motivation of this study is to investigate the performance of high-strength steels in excessive random excitation. To compare the results of different steels extensively used in military applications, vibration tests were carried out on the samples made up of S355MC, S700MC, and S960MC steels under random vibration according to MIL-STD-810G standards. Contrary to expectations, it has been curiously observed that high-strength steels may experience higher stresses that result in to fail earlier than expected due to lower damping ratios. The findings of the study showed that it is difficult to ensure that the use of high-strength steel always provides longer life, especially in a vibration environment. In addition, two frequently used sample manufacturing methods, laser cutting, and milling were applied to observe the effect of the manufacturing method. Different fatigue damage models both in the frequency and the time domain are also evaluated by considering the experimental results of different materials and manufacturing methods.