Papers by Author: Lisa Park

Abstract: In this technical manuscript the cyclic stress amplitude controlled fatigue properties and fracture behavior of an emerging titanium alloy (referred to by its designation as ATI 425TM by the manufacturer) is presented and discussed. The alloy was provided as rod stock in the fully annealed condition. Test specimens of the as-received alloy were cyclically deformed under total stress amplitude control at two different stress ratios (R = 0.1 and R = 0.3) with the purpose of establishing the conjoint and mutually interactive influences of magnitude of cyclic stress, load ratio and intrinsic microstructural effects on cyclic fatigue life, final fracture behavior and viable mechanisms governing failure at the microscopic level. The high cycle fatigue resistance of this titanium alloy is described in terms of maximum stress, load ratio, and maximum elastic strain. The final fracture behavior of the alloy under cyclic loading conditions is discussed in light of the mutually interactive influences of intrinsic microstructural features, magnitude of cyclic stress, load ratio and resultant fatigue life.

Abstract: In this research paper, the cyclic stress amplitude controlled fatigue response and fracture behavior of an Al-Cu (Aluminum Association designation 2219) is presented and discussed. The alloy was provided as a thin sheet in the T62 temper in the fully anodized condition. A small quantity of the as-provided sheet was taken and the surface carefully prepared to remove the thin layer of anodized coating. Test specimens of the alloy, prepared from the two sheets (anodized and non-anodized), were cyclically deformed under stress amplitude control at two different load ratios with the primary objective of establishing the conjoint influence of magnitude of cyclic stress, load ratio and intrinsic microstructural effects on cyclic fatigue life and final fracture characteristics. The high cycle fatigue resistance of the alloy is described in terms of maximum stress, load ratio, and microstructural influences on strength. The final fracture behavior of the alloy sheet is discussed in light of the concurrent and mutually interactive influences of intrinsic microstructural effects, deformation characteristics of the alloy microstructure, magnitude of cyclic stress, and resultant fatigue life.

Abstract: In this research paper, the cyclic stress amplitude controlled fatigue response and fracture behavior of an Al-Cu-Mg alloy (Aluminum Association designation 2024) is presented and discussed. The alloy was friction stir welded in the T8 temper to provide two plates one having high tensile ductility and denoted as Plate A and the other having low tensile ductility and denoted as Plate B. Test specimens of the alloy, prepared from the two plates, were cyclically deformed under stress amplitude control at two different load ratios with the primary objective of documenting the conjoint influence of magnitude of cyclic stress, load ratio and intrinsic microstructural effects on cyclic fatigue life and final fracture characteristics. The high cycle fatigue resistance of the alloy is described in terms of maximum stress, R-ratio, and microstructural influences on strength. The final fracture behavior of the friction stir welded alloy is discussed in light of the concurrent and mutually interactive influences of intrinsic microstructural effects, deformation characteristics of the alloy microstructure, magnitude of cyclic stress, and resultant fatigue life.