Date of Award
Fall 2021
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Mechanical Engineering
First Advisor
Borg, John P.
Second Advisor
Moore, John A.
Third Advisor
Erdeniz, Dinc
Abstract
Ongoing works aim to develop a predictive computational framework whichcan be utilized to shorten the design and certification cycle of additively manufactured (AM) 304L stainless steel (SS304L). High fidelity experiments are utilized to validate and parameterize the computational framework. Results have detailed differing mechanical responses across a breadth of strain rates for wrought and AM SS304L. Differences are attributed to the microstructural properties resulting from the fabrication and treatment of the materials. This work aims to supplement preexisting high strain rate compressive strength experimental data sets to further quantify process-structure-property (PSP) relationships in development of the computational framework. Materials investigated include as-received and heat treated (1250C) wrought and AM SS304L. Pressure-shear plate impact studies and shock-release experiments are utilizedto compare high strain rate dynamic responses. The pressure-shear experimental configuration allows for a direct measurement of flow strength by first compressing the sample of interest and then imparting shear. These complex loading conditions have not previously been studied for SS304L, nor additively manufactured materials. Loading conditions of these experiments span modest stresses of 1-6 GPa. Analysis utilizes traditional elastodynamic relations and a simulation based optimization approach to determine flow strength. Shock-release experiments are utilized to directly compare strength in the compressed state between SS304L variants utilizing the quasi-elastic response of the material. The technique extends the compressive stresses to states beyond those studied in the pressure shear experiments (4.7-33.9 GPa). Samples are first compressed, and the quasielastic response of a release wave is utilized to infer the strength of the shocked state. Flow strength measurements from the pressure shear experiments indicate slightly higher magnitudes in wrought samples (15%) when compared to Z-Cut samples between compressional stresses of 2.5-3.5 GPa. Results suggest combined loading of the AM material influences the dynamic response, as exhibited by the shear wave structure. Wave structure may be due to local strain differences in the AM material, or other shear induced deformation mechanisms. Data sets from shock release experiments indicate similar release strength properties between asreceived and heat treated wrought and AM SS304L. Comparison of flow strength measurements between pressure-shear and shock-release experiments are in good agreement at 5GPa where the data sets overlap.