Session: 16-01-01: Government Agency Student Poster Competition

Paper Number: 150501

150501 - Finite Element Nanoindentation Simulations for Characterizing Material Extremes: Identifying Spherical Indenter Geometry at Shallow Depths 

Nanoindentation is a now widely utilized technique of measuring hardness and other mechanical and physical properties of metal alloys. In recent years, research has turned to simulation for guided measurements and experiments to reduce cost and increase efficacy. Nanoindentation is a widely adopted method for measuring hardness and elastic modulus in a cost-effective and efficient manner. One of the less understood indenter shapes is the spherical indenter, particularly its geometrical precision at the tip. Prior research shows that at the small scale, around 1-10 µm, a manufacture spherical geometry deviates significantly from the ideal shape. Microscale spherical indenters are often imperfect due to hand manufacturing, leading to significant geometric inaccuracies. An indenter with varying radii (4.51 µm to 4.81 µm) was examined, highlighting the need for a new method to accurately capture the complete geometry of indenter tips. Inaccuracies in the indenter’s geometry significantly affect the elastic-plastic strain field during initial contact with the specimen, as deviations from the assumed perfect geometry impact the average plastic strain in the indentation zone. This study presents a novel geometric framework for nanoindentation analysis using the Finite Element Method (FEM), which significantly enhances the accuracy of mechanical property measurements at the nanoscale.

Implementing this method enables the identification and correction of FEM modeling errors in nanoindentation results, while also addressing experimental and discretization errors. The inaccuracies in finite element modeling can be mitigated through a laser scanning technique using a VKx250 microscope with a height resolution of 9 nm on the tip to obtain its 3D topography and integrating advanced FEM techniques in tandem with the accurately identified nanoindenter geometry. The approach not only refines the understanding of material behavior under nanoindentation but also paves the way for more precise and consistent nanomechanical characterization. This study used a 3D FEM model to simulate nanoindentation, addressing the limitations of the actual indenter. While 2D axisymmetric models are often preferred for their cost-effectiveness and simplicity, the 3D model provided more accurate results. The ABAQUS/Standard continuation method was employed to improve the accuracy and stability of the finite element analysis in handling complex nonlinear problems.

In our investigation, we introduced a new indenter geometry that shows an exceptional correlation with nanoindentation experimental data, indicating a more precise depiction of contact mechanics. Comparative analysis between this newly designed tip and previously assumed geometries has unveiled significant variances, with the new tip yielding a notably small standard deviation in measurements compared to experimental results—an insight emphasizing the critical nature of accurate tip geometry. Additionally, our research into Finite Element Modeling (FEM) underscores the substantial impact of mesh density on simulation outcomes.

Presenting Author: Munireach Nannory University of Tennessee, Knoxville

Presenting Author Biography: I am Munireach Nannory a PhD candidate from Cambodia as a student in Dr. Truster's research group. This is my second year to a master program, and I am interested in conducting computational experiments that will raise my awareness to be able to analyze material response to answer the research objective and question. Especially, my passion lies in delving into computational modeling processes for mesoscale material behavior to explore innovative solutions relevant to theory and practical applications. I am a dual degree holder in Bachelor in Education from Royal University of Phnom Penh in 2021 and Bachelor in Civil Engineering from Pannasastra University of Cambodia in 2022, achieving the honor of being ranked as the number one student in my cohort.

Authors:

Munireach Nannory University of Tennessee, Knoxville
Vivek Chawla Ut Institute For Advanced Materials & Manufacturing
Timothy Truster University of Tennessee, Knoxville