Applicability of Fracture Mechanics on Brittle Delamination of Nanoscale Film Edge

Kitamura, Takayuki; Hirakata, Hideki; Satake, Yusuke

doi:10.1299/jsmea.47.106

Cited by 24 publications

(7 citation statements)

References 16 publications

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“…To study the residual stress numerically, the edge effect was considered [23][24][25]. The performance of the TBCs was decreased because of the distribution of stress concentration, which promoted crack initiation in the coating.…”

Section: Resultsmentioning

confidence: 99%

Effect of Top-Coat Thickness and Interface Fluctuation on the Residual Stress in APS-TBCs

Zhao,

Hu,

Wang

et al. 2023

Coatings

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This study focused on the numerical simulation of the distribution of residual stress in yttria-stabilized zirconia (YSZ) coatings prepared with atmospheric plasma spraying (APS). We particularly investigated the stress distribution around the interface between the top coat and bond coat. During thermal spray deposition, droplets and particles deposit on the substrate in a complex manner, causing interface waviness and non-uniform stress distribution. Therefore, residual stress is an important consideration when preparing thermal barrier coatings (TBCs). Residual stresses directly affect the performance of bond coats (BCs) and ceramic top coats (TCs). To accurately evaluate residual stress, we considered interface waviness and the thickness of the ceramic top coat and conducted a detailed analysis of stress distribution. The results show that compressive stress exists at the TC/BC interface, which may be caused by the mismatch in the thermal expansion coefficient between the YSZ top coat and the substrate, potentially leading to coating delamination. Moreover, the residual stress at the TC/BC interface significantly increases with an increasing YSZ thickness. When the top-coat thickness exceeds 300 μm, stress concentration and failure of the coating are likely to occur. Meanwhile, the optimized thermal spray experiment results confirm that the residual stress at the BC/YSZ interface of the thermal barrier coating is tensile stress, with a maximum value of 155 MPa, which is consistent with the finite element calculation results. Furthermore, the failure modes of TBCs with rough interface conditions are discussed in detail. Our research provides important guidance for TBC design and optimizing their performance.

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Section: Resultsmentioning

confidence: 99%

Effect of Top-Coat Thickness and Interface Fluctuation on the Residual Stress in APS-TBCs

Zhao,

Hu,

Wang

et al. 2023

Coatings

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“…To confirm the effectiveness of the molecular-dynamics simulation technique described in Chapters 2 and 3, the author conducted a scratch test on the film-laminated structure (scratch tester: CSR-02 made by Rhesca Co., Ltd.) and compared the test results with the simulation results. Recently, more advanced methods for measuring adhesion strength have been proposed in a number of research papers 14), 15) . However, these advanced methods were very difficult to apply to fairly strong interfaces such as the interface between alumina and Zn.…”

Section: Comparison Between Simulations and Experimentsmentioning

confidence: 99%

Efficient Optimum Design of Metal with Strong Adhesion to Ceramics with a Combination of Orthogonal Array and Response-Surface Method

Iwasaki

2018

J. Soc. Mat. Sci., Japan

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A technology for efficiently designing an appropriate metal material with strong adhesion to a ceramic material was developed by using a combination of an orthogonal array and a response-surface method, and it was applied to the interface adhesion between metals and an example ceramic, alumina (Al2O3) in nanoscale thin-film devices. In this optimum-design technology, at the first step, important factors that significantly influence the adhesion strength were selected from various factors that characterize metal materials by using an orthogonal array with molecular simulations. As a result, the short-side and long-side lattice constants a and b were selected from four metal-material factors (a, b, the electronegativity, E, and the surface energy density, S). At the second step, the adhesion strength was described as a function of the selected important factors by using a response-surface method. From this function, the ideally most appropriate values for a and b that made the adhesion strength maximum were obtained. The obtained optimum values for a and b agreed well with the lattice constants of the ceramic (alumina). At the third step, the most appropriate metal material whose lattice constants were close to the optimum values, which were the lattice constants of the ceramic (alumina), was selected by use of the molecular simulation results of lattice constants. As a result, a Pd alloy with Ni, whose lattice constants were almost the same as the optimum values, was selected as the most appropriate metal material with the strongest adhesion to the ceramic (alumina).

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“…Kotrechko et al [54] and Huang et al [55] investigated the fracture process of nano-crystalline materials under axial tension. Kitamura et al [56] and Ikeda et al [57] investigated the fracture behavior of different materials and proposed the fracture criterion, which can be used to estimate the conditions of crack propagation. They described the crack growth mechanism at the front of various micro-defects and the fracture process in both BCC and FCC materials.…”

Section: Crack Propagation In Zirconiummentioning

confidence: 99%

Molecular Dynamics Study of Zirconium and Zirconium Hydride

Siripurapu¹,

Szpunar²,

Szpunar³

2013

Pricm

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Molecular dynamics (MD) simulations were used in order to investigate structure and mechanical properties of zirconium and zirconium hydride. Calculation of temperature dependent failure of zirconium, diffusion of hydrogen in zirconium, properties of interfaces in zirconium and zirconium hydride and effect of hydrogen on crack nucleation and propagation were in good agreement with available experimental data. These are the first computer simulations where large-scale atomic/molecular massively parallel simulator (LAMMPS) code was used with the Embedded Atom Method (EAM) and Modified Embedded Atom Method (MEAM) to study structure and mechanical properties of zirconium hydrogen system (Zr-H) and zirconium hydride (ZrH2).Verification of methods was done in order to establish the best potential for zirconium and zirconium hydride. EAM and MEAM potentials successfully predicted lattice parameters, mechanical properties and variation of lattice parameters with temperature for α-Zr. MEAM potential was used to predict correctly the face centered structure for ZrH2 and also its mechanical properties.Temperature dependent stress-strain curves were calculated in order to predict yielding point for α-Zr. Results indicate early yielding and failure with increase of temperature in zirconium on application of tensile and compressive strains. Anisotropic stress variation with temperature in α-Zr was calculated.Hydrogen ingress through diffusion of hydrogen in zirconium is a mechanism responsible for formation of hydrides. Temperature-dependent hydrogen diffusion and activation energy for diffusion was calculated and the agreement with experiments was satisfactory. Anisotropy of diffusion of hydrogen is observed for Zr crystal. Hydrogen diffusion was also modeled under tensile and compressive strain and a possible formation of hydrides in the direction perpendicular to applied strain was observed.The effect of strain on orientation of hydride was investigated. Hydride {111} oriented crystal Bonds surrounding atoms and stress concentration analysis were performed using OVITO and VMD software respectively. Weaker bonds and higher stress concentrations are observed in the presence of hydrogen in zirconium. The presented results clearly demonstrate that MD simulation can be used to predict structure and processes that are important for understanding failure in Zr based nuclear materials.iv PREFACE Sections of this thesis have been submitted as a multi-authored paper in refereed conference papers. The research, data analyses and manuscript preparation were carried out by me and the co-authors contributed in editing the manuscripts for submission to refereed conference papers.

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Applicability of Fracture Mechanics on Brittle Delamination of Nanoscale Film Edge

Cited by 24 publications

References 16 publications

Effect of Top-Coat Thickness and Interface Fluctuation on the Residual Stress in APS-TBCs

Effect of Top-Coat Thickness and Interface Fluctuation on the Residual Stress in APS-TBCs

Efficient Optimum Design of Metal with Strong Adhesion to Ceramics with a Combination of Orthogonal Array and Response-Surface Method

Molecular Dynamics Study of Zirconium and Zirconium Hydride

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