scholarly journals Multimodal Surface Instabilities in Curved Film–Substrate Structures

2017 ◽  
Vol 84 (8) ◽  
Author(s):  
Ruike Zhao ◽  
Xuanhe Zhao
Keyword(s):  
Thin Films ◽  
Mechanical Properties ◽  
Numerical Simulation ◽  
Period Doubling ◽  
Tubular Structures ◽  
Modulus Ratio ◽  
Future Design ◽  
Mismatch Strain ◽  
Curved Structures ◽  
Film Substrate

Structures of thin films bonded on thick substrates are abundant in biological systems and engineering applications. Mismatch strains due to expansion of the films or shrinkage of the substrates can induce various modes of surface instabilities such as wrinkling, creasing, period doubling, folding, ridging, and delamination. In many cases, the film–substrate structures are not flat but curved. While it is known that the surface instabilities can be controlled by film–substrate mechanical properties, adhesion and mismatch strain, effects of the structures’ curvature on multiple modes of instabilities have not been well understood. In this paper, we provide a systematic study on the formation of multimodal surface instabilities on film–substrate tubular structures with different curvatures through combined theoretical analysis and numerical simulation. We first introduce a method to quantitatively categorize various instability patterns by analyzing their wave frequencies using fast Fourier transform (FFT). We show that the curved film–substrate structures delay the critical mismatch strain for wrinkling when the system modulus ratio between the film and substrate is relatively large, compared with flat ones with otherwise the same properties. In addition, concave structures promote creasing and folding, and suppress ridging. On the contrary, convex structures promote ridging and suppress creasing and folding. A set of phase diagrams are calculated to guide future design and analysis of multimodal surface instabilities in curved structures.

Strain and Stress Distribution in Vickers Indentation of Coated Materials

2006 ◽  
Vol 514-516 ◽  
pp. 1472-1476
Author(s):  
Jorge M. Antunes ◽  
Nataliya A. Sakharova ◽  
José Valdemar Fernandes ◽  
Luís Filipe Menezes
Keyword(s):  
Thin Films ◽  
Mechanical Properties ◽  
Numerical Simulation ◽  
Young’S Modulus ◽  
Indentation Depth ◽  
Young's Modulus ◽  
Three Dimensional ◽  
Depth Sensing ◽  
Coated Materials ◽  
Film Substrate

Depth sensing indentation equipment allows the mechanical properties of thin films to be easily determined, particularly the hardness and Young’s modulus. In order to minimize the influence of the substrate on the measured properties, the indentation depth must be limited to a small fraction of the film’s thickness. However, for very thin films, the determination of the contribution of the substrate and the film to the measured mechanical properties becomes a hard task, because both deform plastically. The numerical simulation of ultramicrohardness tests can be a helpful tool towards better understanding of the influence of the parameters involved in the mechanical characterization of thin films. For this purpose, a three-dimensional numerical simulation home code, HAFILM, was used to simulate ultramicrohardness tests on coated substrates. Materials with different Young’s modulus film/substrate ratios were tested. Analyses of strain and stress distributions for several indentation depth values were performed, in order to clarify the composite behaviour.

Appling of New Optical Measurement and Theory in Mechanical Properties of Thin Film

2011 ◽  
Vol 121-126 ◽  
pp. 4295-4299
Author(s):  
Hao MA Yun ◽  
Lu Ping Chao ◽  
J. S Hsu
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Mechanical Properties ◽  
Thermal Stresses ◽  
Optical Measurement ◽  
Phase Shifting ◽  
Deposition Condition ◽  
Full Field ◽  
Evaporation Technique ◽  
Film Substrate

The thesis aims to characterize the mechanical properties and stresses for thin films deposited on the circular substrates. First, the thin films with the same deposition condition were successively deposited on the distinct substrates using the evaporation technique. The phase-shifting Twyman-Green interferometer (PSTGI) was then employed to measure the warpage of the film-substrate structures and therefore the intrinsic stresses and thermal stresses can be calculated from the well-known Stoney’s formula. The coefficients of thermal expansion (CTE) and Young’s modulus of thin films were also obtained from the Stoney’s theory. Furthermore, the merit of full-field character of optical interferometry was used to propose a novel methodology using the Chen and Ou’s theory to improve the accuracy and to reduce the experiment procedures in the traditional measurement of the aforementioned mechanical properties. Finally, the measured results corresponding to the traditional and proposed methods were respectively substituted into their adopted theories to compare their difference. The results reveal that the accuracy of proposed methodology is considerably improved and the experimental procedures are reduced to those of the traditional methods.

On the Characterization of Thin Film-only Mechanical Property Based on the Indentation Image Analysis

2006 ◽  
Vol 976 ◽  
Author(s):  
Yun-Hee Lee ◽  
Yong-Il Kim ◽  
Hoon-Sik Jang ◽  
Seung-Hoon Nahm ◽  
Ju-Young Kim ◽  
...  
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Mechanical Properties ◽  
Penetration Depth ◽  
Volume Ratio ◽  
Hardness Measurement ◽  
Relative Depth ◽  
Au Thin Films ◽  
Film Substrate ◽  
Indenter Penetration

AbstractConventional nanoindentation testing generally uses a peak penetration depth of less than 10 % of thin-film thickness in order to measure film-only mechanical properties, without considering the critical depth for a given thin film-substrate system. The uncertainties in this testing condition make hardness measurement more difficult. We propose a new way to determine the critical relative depth for general thin-film/substrate systems; an impression volume analyzed from the remnant indent image is used here as a new parameter. Nanoindents made on soft Cu and Au thin films with various indentation loads were observed by atomic force microscope. The impression volume calculated from 3D remnant image was normalized by the indenter penetration volume. This indent volume ratio varied only slightly in the shallow regime but decreased significantly when the indenter penetration depth exceeded the targeted critical relative depth. Thus, we determined the critical relative depth by empirically fitting the trend of the indent volume ratio and determining the inflection point. The critical relative depths for Cu and Au films were determined as 0.170 and 0.173, respectively, values smaller than 0.249 and 0.183 determined from the hardness variation of the two thin films. Hence the proposed indent volume ratio is highly sensitive to the substrate constraint, and stricter control of the penetration depth is needed to measure film-only mechanical properties.

scholarly journals The role of nonlinear substrate elasticity in the wrinkling of thin films

2013 ◽  
Vol 371 (1993) ◽  
pp. 20120422 ◽  
Author(s):  
John W. Hutchinson
Keyword(s):  
Thin Films ◽  
Substrate Stiffness ◽  
Modulus Ratio ◽  
Compliant Substrates ◽  
Wide Range ◽  
The Stability ◽  
Film Substrate ◽  
Film Stiffness ◽  
Substrate Elasticity

The role of substrate nonlinearity in the stability of wrinkling of thin films bonded to compliant substrates is investigated within the initial post-bifurcation range when wrinkling first emerges. A fully nonlinear neo-Hookean bilayer composed of a thin film on a deep substrate is analysed for a wide range of the film–substrate stiffness ratio, from films that are very stiff compared with the substrate to those only slightly stiffer. Substrate pre-stretch prior to film attachment is shown to have a significant effect on the nonlinearity relevant to wrinkling. Two dimensionless parameters are identified that control the stability and mode shape evolution of the bilayer: one specifying arbitrary uniform substrate pre-stretch and the other a stretch-modified modulus ratio. For systems with film stiffness greater than about five times that of the substrate the wrinkling bifurcation is stable, whereas for systems with smaller relative film stiffness bifurcation can be unstable, especially if substrate pre-stretch is not tensile.

Effect of Thickness and Substrates on the Mechanical Properties of Tantalum and Tantalum Nitride Thin Films

1995 ◽  
Vol 403 ◽  
Author(s):  
Ranjana Saha ◽  
Rama B. Inturi ◽  
John A. Barnard
Keyword(s):  
Thin Films ◽  
Mechanical Properties ◽  
Elastic Modulus ◽  
Composite System ◽  
Tantalum Nitride ◽  
X Ray Diffraction ◽  
X Ray ◽  
Film Substrate

AbstractDetermining the intrinsic mechanical properties of films by nanoindentation is complicated by the presence of the substrate. Generally, for very thin films (<100 nm) one unavoidably observes the properties of the film/substrate composite system. In order to determine the extent of the effect of the substrate on the mechanical properties of Ta and Ta-N thin films, we have grown these films in four different thicknesses (50, 250, 400 and 500 nm) and on three different substrates (glass, oxidized Si, and sapphire). The structure of the films was evaluated by x-ray diffraction and the mechanical properties (hardness and elastic modulus) were determined by nanoindentation.

scholarly journals Wrinkling Phenomena in Neo-Hookean Film/Substrate Bilayers

2012 ◽  
Vol 79 (3) ◽  
Author(s):  
Yanping Cao ◽  
John W. Hutchinson
Keyword(s):  
Finite Element ◽  
Critical Strain ◽  
Full Range ◽  
Period Doubling ◽  
Modulus Ratio ◽  
Layer System ◽  
Mountain Ridge ◽  
Compliant Substrates ◽  
Film Substrate

Wrinkling modes are determined for a two-layer system comprised of a neo-Hookean film bonded to an infinitely deep neo-Hookean substrate with the entire bilayer undergoing compression. The full range of the film/substrate modulus ratio is considered from the limit of a traction-free homogeneous substrate to very stiff films on compliant substrates. The role of substrate prestretch is considered wherein an unstretched film is bonded to a prestretched substrate with wrinkling arising as the stretch in the substrate is relaxed. An exact bifurcation analysis reveals the critical strain in the film at the onset of wrinkling. Numerical simulations carried out within a finite element framework uncover advanced post-bifurcation modes including period-doubling, folding and a newly identified mountain ridge mode.

Thermo-Mechanical Properties of Terfenol-D Thin Films

1994 ◽  
Vol 360 ◽  
Author(s):  
Quanmin Su ◽  
Y. Zheng ◽  
Manfred Wuttig
Keyword(s):  
Thin Films ◽  
Mechanical Properties ◽  
Amorphous Material ◽  
Recrystallization Temperature ◽  
Dynamic Measurements ◽  
Si Substrates ◽  
Damping Characteristics ◽  
Δe Effect ◽  
Film Substrate ◽  
Deposited Films

AbstractThe thermo-mechanical properties of Terfenol-D thin films deposited on Si substrates werestudied by static and dynamic measurements of film/substrate composite cantilevers. The Curie transition, δE effect and mechanical damping of the film were measuredsimultaneously. The stress in the film was controlled by annealing below the recrystallization temperature and determined to vary from -500 MPa, compression, in as deposited films to +480 MPa, tension, in annealed films. The Curie temperature shifts from 80ºC to 140ºC as the tension increases while the structure of the film remains amorphous. The stress change induced by annealing also drastically effects the film's damping characteristics. The δE effect of the amorphous material, about 20%, wasused to estimate the magnetostriction, λs≈4.10-3.

Effect of lattice mismatch on the epitaxy of sol-gel LiNbO3 thin films

1997 ◽  
Vol 12 (5) ◽  
pp. 1391-1400 ◽  
Author(s):  
T. A. Derouin ◽  
C. D. E. Lakeman ◽  
X. H. Wu ◽  
J. S. Speck ◽  
F. F. Lange
Keyword(s):  
Thin Films ◽  
Buffer Layer ◽  
Lattice Mismatch ◽  
Sol Gel ◽  
Mismatch Strain ◽  
Transmission Electron ◽  
Solution Precursor ◽  
Growth Method ◽  
Film Substrate ◽  
Interfacial Plane

A solution precursor method based on metal alkoxides was used to produce epitaxial LiNbO3 thin films, ≈200 nm thick, on (0001) sapphire substrates. Transmission electron. microscopy revealed that the major cause of surface roughness in these films was grain boundary grooves between mosaic grains with misorientations ≤5°. It is postulated that these low angle boundaries directly result in surface grooving and roughness. The epitaxial films also contained two distinguishable variants in the film/substrate interfacial plane, namely, an aligned variant, and a 60° rotated variant, . A seeded grain growth method was used to minimize the presence of the 60° rotated variant. An epitaxial buffer layer of Fe2O3 was used to lower the mismatch strain, eliminate the 60° rotated variant, and reduce the mosaic nature of the LiNbO3 film. X-ray rocking curve full-width-at-half-maximum (FWHM) values measured on the film peak indicate that the mosaic character can be reduced from 1.5° to 0.76° by using a buffer layer.

scholarly journals Nonslipping Contact Between a Mismatch Film and a Finite-Thickness Graded Substrate

2015 ◽  
Vol 83 (2) ◽  
Author(s):  
Chen Peijian ◽  
Chen Shaohua ◽  
Yao Yin
Keyword(s):  
Failure Modes ◽  
Finite Thickness ◽  
Interfacial Shear Stress ◽  
Modulus Ratio ◽  
Transform Method ◽  
Mismatch Strain ◽  
Elastic Film ◽  
Potential Failure ◽  
The Fourier Transform ◽  
Film Substrate

The contact behavior of an elastic film subjected to a mismatch strain on a finite-thickness graded substrate is investigated, in which the contact interface is assumed to be nonslipping and the shear modulus of the substrate varies exponentially in the thickness direction. The Fourier transform method is adopted in order to reduce the governing partial differential equations to integral ones. With the help of numerical calculation, the interfacial shear stress, the internal normal stress in the film and the stress intensity factors are predicted for cases with different material parameters and geometric ones, including the modulus ratio of the film to the substrate, the inhomogeneous feature of the graded substrate, as well as the profile of the contacting film. All the physical predictions can be used to estimate the potential failure modes of the film–substrate interface. Furthermore, it is found that the result of a finite-thickness model is significantly different from the prediction of a generally adopted half-plane one. The study should be helpful for the design of film–substrate systems in real applications.

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