Abstract
In this study fatigue tests have been conducted on additively manufactured notched specimens made of titanium alloy Ti-6Al-4V under uniaxial loading and multiaxial non-proportional loading. Laser powder bed fusion technique has been employed to fabricate cylindrical specimens which have been successively machined to obtain a circumferential notch. Four varieties of specimens were fabricated depending on the build orientation and the application of a post-fabrication stress-relief heat treatment. The influence of layer orientation and heat treatment on the material microstructure has been analyzed. Strain controlled tests were performed with both proportional loading represented by a push-pull strain path and non-proportional loading represented by a circle strain path. The number of cycles to failure under both proportional and non-proportional loadings seemed not depending on layer orientation and heat-treatment. The cyclic plastic behavior of the material has been verified through the observation of the softening and hardening curves. The surface of the crack has been finally analyzed to verify the crack initiation position which has been detected on voids or defects located in the vicinity of the notch tip.
Highlights
IntroductionIn the field of material innovation, additive manufacturing ( known as 3D printing) of metals represents the latest trend of research [1,2]
In the field of material innovation, additive manufacturing of metals represents the latest trend of research [1,2]
Crack initiation site has been observed on the fracture surface, focusing on the observation of cracks initiating from internal defects and their position on the notch surface
Summary
In the field of material innovation, additive manufacturing ( known as 3D printing) of metals represents the latest trend of research [1,2]. The major challenge in the definition of the static and fatigue characteristics of materials fabricated with such techniques is the wide variety of microstructures obtainable due to the wide range of process parameters that can be set in the in the fabrication phase Despite this obstacle, several researches have been conducted and a common trend in the mechanical properties in relation to the microstructure have been defined [5,6]. Components’ geometrical discontinuity features represented by notches, grooves and holes that provoke phenomena of stress concentration may lead to local plasticity Such components are often subjected to multiaxial loading conditions (proportional or non-proportional) which further complicates the mechanical response of the material. Crack initiation site has been observed on the fracture surface, focusing on the observation of cracks initiating from internal defects and their position on the notch surface
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