Fatigue Reliability and Failure Mechanisms of Steel and Aluminum Alloys for Advanced Manufacturing Applications

Abstract

Fatigue failure is important in an engineering component when it is subjected to repeated or cyclic loading, because it can fracture at stresses below the UTS of the material. The objective of this study is to investigate the fatigue reliability and failure mechanisms of steel and aluminum alloys for advanced manufacturing applications that will assist in selecting more suitable materials to make safer, longer-lasting and more reliable U.S. manufacturing and infrastructure. The experimental investigation is conducted on AISI 1018 steel, AISI 1020 steel, 6061 aluminium alloy and B16 brass as an additional laboratory reference material. Experimental evidence was created using tensile, hardness, Charpy impact, tensile-fatigue, and rotating-beam fatigue laboratory tests. The mechanical characterization test involved stress strain testing, tensile testing, hardness, impact and energy absorption testing, and fatigue testing that covered cyclic loading, fatigue life, and fracture behavior. The loading conditions are related to the fatigue-life prediction via the fatigue analysis, employing the concepts of stress amplitude, mean stress, endurance-limit, Goodman and Basquin finite-life relationship. It was decided that the rotating-beam fatigue experiment would give a direct comparison of the two materials: AISI 1018 steel and 6061 aluminum. Under the conditions tested, failure was observed at 27,700 cycles for the steel specimen and at 5,000 cycles for the aluminum specimen. The Charpy impact experiment also reported mean impact-strength values of 3819.975 for AISI 1018 steel, 2786.569 for AISI 1020 steel, 2199.397 for B16 brass, and 1098.715 for 6061 aluminum. The results here show that there are significant differences between the mechanical and fatigue properties of the materials. When assessing reliability, the study also takes into account that experimental variability, condition of specimens, measurement uncertainty, and differences between theoretical predictions and observed fatigue life can all have an impact. The desired result is a performance and failure comparison of the materials that will yield the most reliable material based on the conditions studied and will be useful in real world material selection guidelines for advanced manufacturing components. The results are used to guide engineering toward greater durability, safety, service life and reliability in extreme manufacturing and infrastructure applications, but the reliability results are based on tested environments.