Article
Finite Element Analysis on Initial Crack Site of Porous
Structure Fabricated by Electron Beam Additive Manufacturing
Meng-Hsiu Tsai
1,2,†
, Chia-Ming Yang
3,†
, Yu-Xuan Hung
1
, Chao-Yong Jheng
3
, Yen-Ju Chen
4
, Ho-Chung Fu
1,
*
and In-Gann Chen
3,
*
Citation: Tsai, M.-H.; Yang, C.-M.;
Hung, Y.-X.; Jheng, C.-Y.; Chen, Y.-J.;
Fu, H.-C.; Chen, I.-G. Finite Element
Analysis on Initial Crack Site of
Porous Structure Fabricated by
Electron Beam Additive
Manufacturing. Materials 2021, 14,
7467. https://doi.org/10.3390/
ma14237467
Academic Editors: Ludwig Cardon
and Clemens Holzer
Received: 31 October 2021
Accepted: 30 November 2021
Published: 6 December 2021
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1
Department of Mold and Die Engineering, National Kaohsiung University of Science and Technology,
Kaohsiung 807618, Taiwan; tmh@nkust.edu.tw (M.-H.T.); terry840710@yahoo.com.tw (Y.-X.H.)
2
School of Dentistry, College of Dental Medicine, Kaohsiung Medical University, Kaohsiung 80708, Taiwan
3
Department of Materials Science and Engineering, National Cheng-Kung University, Tainan 701, Taiwan;
lf2killer@hotmail.com (C.-M.Y.); water60068@gmail.com (C.-Y.J.)
4
Metal Processing R & D Department, Metal Industries Research and Development Centre (MIRDC),
Kaohsiung 811, Taiwan; yjchen@mail.mirdc.org.tw
* Correspondence: hcfu@nkust.edu.tw (H.-C.F.); ingann@mail.ncku.edu.tw (I.-G.C.);
Tel.: +886-7-3814526-15410 (H.-C.F.); +886-6-2763741 (I.-G.C.)
† Meng-Hsiu Tsai and Chia-Ming Yang contributed equally to this manuscript as the first authors.
Abstract:
Ti6Al4V specimens with porous structures can be fabricated by additive manufacturing to
obtain the desired Young’s modulus. Their mechanical strength and deformation behavior can be
evaluated using finite element analysis (FEA), with various models and simulation methodologies
described in the existing literature. Most studies focused on the evaluation accuracy of the mechanical
strength and deformation behavior using complex models. This study presents a simple elastic model
for brittle specimens followed by an electron beam additive manufacturing (EBAM) process to predict
the initial crack site and threshold of applied stress related to the failure of cubic unit lattice structures.
Six cubic lattice specimens with different porosities were fabricated by EBAM, and compression tests
were performed and compared to the FEA results. In this study, two different types of deformation
behavior were observed in the specimens with low and high porosities. The adopted elastic model
and the threshold of applied stress calculated via FEA showed good capabilities for predicting the
initial crack sites of these specimens. The methodology presented in this study should provide a
simple yet accurate method to predict the fracture initiation of porous structure parts.
Keywords:
electron beam additive manufacturing; Ti6Al4V; brittleness; finite element analysis;
elastic model; initial crack site
Highlights
1.
A combination of EBAM and FEA was employed for the analysis of initial crack sites.
2.
The initial crack sites predicted by the elastic model were consistent with experimental
results.
3.
The threshold stresses calculated by FEA coincided with the crack sites of specimens
with different porosities.
4.
The collapse mechanism due to strut behavior under uniaxial compression stress was
investigated.
1. Introduction
Porous materials, also called cellular solids, fabricated by additive manufacturing have
attracted attention in biomedical implants, such as acetabular hip cups [
1
–
3
], mandibles [
4
],
fusion cages [
5
,
6
], and various other applications [
2
]. Implants made from a material with
a low elastic modulus can reduce the effect of stress shielding [
7
]. The use of porous metal
structures can effectively eliminate this phenomenon. The amount of porosity in the im-
plant is considered a crucial factor in promoting successful bone integration with a porous
Materials 2021, 14, 7467. https://doi.org/10.3390/ma14237467 https://www.mdpi.com/journal/materials
