共查询到20条相似文献,搜索用时 46 毫秒
1.
Hanqing Jiang Dahl-Young Khang Huiyang Fei Hoonsik Kim Yonggang Huang Jianliang Xiao John A. Rogers 《Journal of the mechanics and physics of solids》2008,56(8):2585-2598
Buckling of stiff thin films on compliant substrates has many important applications ranging from stretchable electronics to precision metrology and sensors. Mechanics plays an indispensable role in the fundamental understanding of such systems. Some existing mechanics models assume plane-strain deformation, which do not agree with experimental observations for narrow thin films. Systematic experimental and analytical studies are presented in this paper for finite-width stiff thin films buckling on compliant substrates. Both experiments and analytical solution show that the buckling amplitude and wavelength increase with the film width. The analytical solution agrees very well with experiments and therefore provides valuable guide to the precise design and control of the buckling profile in many applications. The effect of film spacing is studied via the analytical solutions for two thin films and for periodic thin films. 相似文献
2.
《力学快报》2017,(3)
The buckling of thin gel film has attracted much attention due to its applications in the design of threedimensional structure from two-dimensional template. We have established an analytical model to study the swelling-induced buckling of a thin gel strip with one edge clampecd and the others free. The closed-form solutions for the amplitude and wavelength of the buckled shape are obtained by energy minimization of the total potential energy. The analytical results agree well with finite element analysis based on the inhomogeneous gel theory without any parameter fitting. The model provides a route to study complex postbuckling behaviors of thin gel films and guidelines to design the buckled configuration quantitatively by controlling the swelling ratio. 相似文献
3.
Bo Li Shi-Qing Huang Xi-Qiao Feng 《Archive of Applied Mechanics (Ingenieur Archiv)》2010,80(2):175-188
The wrinkling of a stiff thin film bonded on a soft elastic layer and subjected to an applied or residual compressive stress
is investigated in the present paper. A three-dimensional theoretical model is presented to predict the buckling and postbuckling
behavior of the film. We obtained the analytical solutions for the critical buckling condition and the postbuckling morphology
of the film. The effects of the thicknesses and elastic properties of the film and the soft layer on the characteristic wrinkling
wavelength are examined. It is found that the critical wrinkling condition of the thin film is sensitive to the compressibility
and thickness of the soft layer, and its wrinkling amplitude depends on the magnitude of the applied or residual in-plane
stress. The bonding condition between the soft layer and the rigid substrate has a considerable influence on the buckling
of the thin film, and the relative sliding at the interface tends to destabilize the system. 相似文献
4.
Huanyu Cheng Yihui Zhang Keh-Chih Hwang John A. Rogers Yonggang Huang 《International Journal of Solids and Structures》2014
Controlled buckling can impart stretchable mechanics to brittle materials when integrated as thin films on soft, elastomeric substrates. Typical elastomers are permeable to fluids, however, and therefor unable to provide robust barriers to entry of water, for instance, into devices built with the supported thin films. In addition, the mechanical strength of a system dominated by a soft substrate is often unsatisfactory for realistic applications. We show that introduction of a bi-layer substrate yields a robust, high strength system that maintains stretchable characteristics, with a soft layer on top of a relatively stiff layer in the substrate. As a mechanical protection, a soft encapsulation layer can be used on top of the device and the stretchability of the encapsulated system is smaller than that of the system without encapsulation. A simple, analytic model, validated by numerical analysis and FEA, is established for stiff thin films on a bi-layer substrate, and is useful to the design of stretchable systems. 相似文献
5.
Surface microstructures of solid materials play a significant role in various wetting and dewetting phenomena. In the present paper, the effect of micro- and nano-structures of a substrate surface on the morphology and evolution of liquid droplets and thin films is examined. The governing equations satisfied by droplets and films on a sinusoidal surface are derived by considering van der Waals force, surface tension, gravity and hydrostatic pressure. The morphologies of both liquid droplets and thin films are numerically simulated under various characteristic sizes of roughness. It is found that the droplet shapes show a significant dependence upon the characteristic sizes of substrate microstructures. A thin liquid film on a hydrophilic substrate may have a horizontal surface or replicate the substrate morphology, depending on the wavelength of roughness.The project supported by the National Natural Science Foundation of China (10525210, 10121202) and the Ministry of Education of China.The English text was polished by Keren Wang. 相似文献
6.
A thin metallic film deposited on a compliant polymeric substrate begins to wrinkle under compression induced in curing process
and afterwards cooling of the system. The wrinkle mode depends upon the thin film elasticity, thickness, compressive strain,
as well as mechanical properties of the compliant substrate. This paper presents a simple model to study the modulation of
the wrinkle mode of thin metallic films bonded on viscous layers in external electric field. During the procedure, linear
perturbation analysis was performed for determining the characteristic relation that governs the evolution of the plane-strain
wrinkle of the thin films under varying conditions, i.e., the maximally unstable wrinkle mode as a function of the film surface
charge, film elasticity and thickness, misfit strain, as well as thickness and viscosity of the viscous layer. It shows that,
in proper electric field, thin film may wrinkle subjected to either compression or tension. Therefore, external electric field
can be employed to modulate the wrinkle mode of thin films. The present results can be used as the theoretical basis for wrinkling
analysis and mode modulation in surface metallic coatings, drying adhesives and paints, and microelectromechanical systems
(MEMS), etc. 相似文献
7.
《Journal of Fluids and Structures》2002,16(7):989-1008
During manufacturing processes of thin materials such as paper, photographic film, and magnetic film, which are handled as continuous sheets and subjected to drying air-flows, the interaction of the air with the web can cause the free edges to vibrate violently. This phenomenon is related to the waving motion of a flag in the wind, except that the thin films under consideration are under tension in the direction of the air-flow or at right angles to it. A travelling-wave analysis was done based on incompressible potential-flow theory; the critical flow speed, wave speed, wavelength, and flutter frequency were predicted. A closed-form solution of the critical flow speed is suggested. Experiments were carried out with stationary thin films mounted in a wind tunnel where the direction of tension was perpendicular to the flow direction. It was shown that the analysis, which assumes that the film is infinitely long in the flow direction, could successfully predict the critical flow speed above which violent edge vibrations occur. 相似文献
8.
9.
R. Huang 《Journal of the mechanics and physics of solids》2005,53(1):63-89
A compressed elastic film on a compliant substrate can form wrinkles. On an elastic substrate, equilibrium and energetics set the critical condition and select the wrinkle wavelength and amplitude. On a viscous substrate, wrinkle grows over time and the kinetics selects the fastest growing wavelength. More generally, on a viscoelastic substrate, both energetics and kinetics play important roles in determining the critical condition, the growth rate, and the wavelength. This paper studies the wrinkling process of an elastic film on a viscoelastic layer, which in turn lies on a rigid substrate. The film is elastic and modeled by the nonlinear von Karman plate theory. The substrate is linear viscoelastic with a relaxation modulus typical of a cross-linked polymer. Beyond a critical stress, the film wrinkles by the out-of-plane displacement but remains bonded to the substrate. This study considers plane strain wrinkling and neglects the in-plane displacement. A classification of the wrinkling behavior is made based on the critical conditions at the elastic limits, the glassy and rubbery states of the viscoelastic substrate. Linear perturbation analyses are conducted to reveal the kinetics of wrinkling in films subjected to intermediate and large compressive stresses. It is shown that, depending on the stress level, the growth of wrinkles at the initial stage can be exponential, accelerating, linear, or decelerating. In all cases, the wrinkle amplitude saturates at an equilibrium state after a long time. Subsequently, both amplitude and wavelength of the wrinkle evolve, but the process is kinetically constrained and slow compared to the initial growth. 相似文献
10.
《应用数学和力学(英文版)》2017,(5)
The paper investigates continuously changing wrinkle patterns of thin films bonded to a gradient substrate. Three types of gradient substrates including exponential,power-law, and symmetry models are considered. The Galerkin method is used to discretize the governing equation of film bonded to gradient substrates. The wavelength and the normalized amplitude of the wrinkles for substrates of various material gradients are obtained. The numerical simulation based on the finite element method(FEM) is used to evolve the wrinkle patterns. The result agrees well with that of the analytical model.It is concluded that localization of wrinkle patterns strongly depends on the material gradient. The critical membrane force depends on both the minimum value of wrinkle stiffness and the gradient of wrinkle stiffness when the wrinkle stiffness is at its minimum.This work provides a better understanding for local wrinkle formation caused by gradient substrates. 相似文献
11.
A. Wierschem V. Bontozoglou C. Heining H. Uecker N. Aksel 《International Journal of Multiphase Flow》2008,34(6):580-589
We study viscous gravity-driven films flowing over periodically undulated substrates. Linear analysis describes steady flow along small amplitude corrugations for films of arbitrary thickness. Solving the resulting system numerically, we demonstrate resonance (or, possibly, near resonance) and identify different behaviours for thin, intermediate and thick films. Approximating the leading-order velocity profile by the free surface value allows for an analytic solution, which – in the limit of high Reynolds numbers – recovers the different regimes and reveals the relevant physical mechanisms. Our results support the view that the resonance is associated with an interaction of the undulated film with capillary-gravity waves travelling against the mean flow direction. As a consequence, the resonance peak is attained under conditions that render the wave phase velocity equal to zero in the laboratory reference frame, and thus permit direct exchange of energy between the steadily deformed film and the free surface. 相似文献
12.
Manufacturing of multilayer thin films deposited on a glass substrate can be accomplished by means of pulsed laser sources.
Thermal and optical nonlinearities are induced during transient heating, since the response of weakly absorbing thin films
depends on the temperature. The heat source can either directly impinge the film surface,␣front treatment, or the glass substrate,
back treatment. In this paper a one-dimensional conjugate non-linear thermal-optical time dependent problem is numerically
analysed. The investigation is accomplished in order to compare the two processes. For a Nd-YAG laser with wavelength of 1064
nm, a a-Si/TCO and Al/a-Si/TCO multilayers are investigated. Results are presented in form of spatial and temporal temperature
profiles as well as absorbed heat transfer rates inside the layers. The accomplished analysis clearly shows that the back
treatment is more efficient in terms of manufacturing process, oriented to the production of photovoltaic cells.
Received on 4 November 1997 相似文献
13.
Ya-Pu Zhao 《Archive of Applied Mechanics (Ingenieur Archiv)》2002,72(1):77-84
Summary The morphological stability of epitaxial thin elastic films on a substrate by van der Waals force is discussed. It is found
that only van der Waals force with negative Hamaker constant tends to stabilize the film, and the lower bound for the Hamaker constant is also obtained for the stability of thin film.
The critical value of the undulation wavelength is found to be a function of both film thickness and external stress. The
charateristic time-scale for surface mass diffusion scales to the fourth power to the wavelength of the perturbation.
Received 4 December 2000; accepted for publication 31 July 2001 相似文献
14.
The problem of a thin film coated on an elastic layer and subject to a thermal variation is analytically investigated in the present work. The analysis is developed in order to assess the mechanical behaviour of a crystalline undulator designed for obtaining high emission radiations through channelling phenomenon. It consists in a plane silicon wafer alternately patterned with thin films in silicon nitride on both surfaces. The system adopts a periodic curvature as a result of the misfit strain due to the different thermal expansivities of the layer and the film. The problem is governed by an integral equation which can be reduced to a linear algebraic system by approximating the unknown interfacial shear stress via series expansion of Chebyshev polynomials. 相似文献
15.
Caprice Gray Chris B. Rogers Vincent P. Manno Robert D. White 《Experiments in fluids》2011,51(1):281-293
Dual emission laser induced fluorescence (DELIF) is a technique for measuring the instantaneous thin fluid film thickness in dynamic systems. Two fluorophores within the system produce laser induced emissions that are filtered and captured by two cameras. The ratio of the images from these cameras is used to cancel the effect of the laser beam profile on the image intensity. The resultant intensity ratio can be calibrated to a fluid film thickness. The utilization of a 2-dye system when applied to Chemical Mechanical Polishing (CMP) is complicated by the fluorescence of the polymeric polishing pad and the light scattering particles in the polishing slurry. We have developed a model of DELIF for CMP with 1-dye employing the polishing pad as the second fluorophore. While scattering particles in the slurry decrease the overall intensity of the individual images, the contrast in the image ratio increases. Using the 1-dye DELIF system to measure thin slurry films, our model results indicate that a cubic calibration may be needed. However, experimental results suggest a linear calibration is achieved for slurry films between 0 and 133???m thick with scattering coefficients as high as 8.66?mm?1 at a wavelength equal to 410?nm. 相似文献
16.
This paper aims at developing a stochastic-elastic model of a soft elastic body adhering on a wavy surface via a patch of molecular bonds. The elastic deformation of the system is modeled by using continuum contact mechanics, while the stochastic behavior of adhesive bonds is modeled by using Bell's type of exponential bond association/dissociation rates. It is found that for sufficiently small adhesion patch size or stress concentration index, the adhesion strength is insensitive to the wavelength but decreases with the amplitude of surface undulation, and that for large adhesion patch size or stress concentration index, there exist optimal values of the surface wavelength and amplitude for maximum adhesion strength. 相似文献
17.
A flat, compressed elastic film on a viscous layer is unstable. The film can form wrinkles to reduce the elastic energy. In this paper, we are interested in the two-dimensional models for thin films bonded to a viscous layer and in particular we focus on generic instabilities evidenced in this context by Suo and coworkers [Huang, Z., Hong, W., Suo, Z., 2005. Non linear analyses of wrinkles in a film bonded to a compliant substrate. J. Mech. Phys. Solids 53, 2101–2118; Lo, Y.H., 1991. New approach to grow pseudomorphic structures over the critical thickness. Appl. Phys. Lett. 59, 2311–2320]. We present a rigorous linear perturbation analysis for anisotropic materials, that allows the prediction of both the orientation of the corrugations of the thin film, and the wavelength that maximize the growth velocity. Finally, we compare our theoretical estimates to experimental results for a In0.65Ga0.35As alloy constraint to InP. 相似文献
18.
Elastic pulses were generated in a thin (3-mm) right circular conical shell with apex angle of 20 deg, by an axial impact of a drop weight. Radial-strain pulses of about 250-μs duration were measured at three locations along the cone by semiconductor strain gages. The relative amplitude decrease of the strain pulse was determined as a function of the distance traveled. An approximate analytical solution for this problem is presented. It is shown that, for cones made of material with Poisson's ratio ν=1/3, the approximation leads to the one-dimensional spherical-wave equation and the wave velocity is that of longitudinal waves in thin plates. The decay of amplitude predicted by the model depends on the distance traveled and on the wavelength and it agrees fairly well with the experimental results. The model also gives an upper bound on the amplitude decrease of the pulse. 相似文献
19.
The problem of calculating the nonstationary aerodynamic characteristics of a cascade of thin lightly loaded airfoils in a subsonic flow with the formation of thin separation zones of finite extent is solved approximately. As in [1–5], an approach based on a linear small-perturbation analysis, within which the flow is assumed to be inviscid, is employed and the boundaries of the unsteady separation zones are simulated by oscillating lines of contact discontinuity. However, instead of the requirement of a given fixed pressure at the boundary of the separation zone, used in [1–5], this study proposes a more general condition according to which on each element of length of the thin separation layer the pressure oscillates with an amplitude proportional to the local value of the amplitude of its thickness oscillations. The problem is reduced to a system of two singular integral equations which can be solved numerically.Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 1, pp. 181–191, January–February, 1995. 相似文献
20.
H-J. Choi J-H. Kim H-J. Lee S-A. Song H-J. Lee J-H. Han M-W. Moon 《Experimental Mechanics》2010,50(5):635-641
Wrinkle-based measurement of elastic modulus for a nano-scale thin film was analyzed. As a demonstrative example, the wrinkles
of Pt films on a Polydimethylsiloxane (PDMS) substrate under compressive loading were formed with a well-defined wavelength,
corresponding to the difference of elastic moduli between the films and substrates. The elastic modulus of the Pt nano-scale
thin film measured with the wrinkle-based measurement was found to be consistent with that independently measured with micro-tensile
test. Uncertainty of the wrinkle-based measurement was analyzed to figure out the main uncertainty components for the evaluation
of elastic modulus measurement, and guidelines for the reliable wrinkle-based measurement were suggested. 相似文献