Mechanical Modeling of Thin Films and Cover Plates Bonded to Graded Substrates

2008 ◽  
Vol 75 (5) ◽  
Author(s):  
Mehmet A. Guler
Keyword(s):  
Thin Films ◽  
Stress Intensity ◽  
Interfacial Shear Stress ◽  
Contact Problems ◽  
Stress Concentrations ◽  
Elastic Continuum ◽  
Temperature Changes ◽  
Initiation And Propagation ◽  
Axial Normal Stress ◽  
Cover Plates

In this study, the contact problems of thin films and cover plates are considered. In these problems, the loading consists of any one or combination of stresses caused by uniform temperature changes and temperature excursions, far field mechanical loading, and residual stresses resulting from film processing or welding. The primary interest in this study is in examining stress concentrations or singularities near the film ends for the purpose of addressing the question of crack initiation and propagation in the substrate or along the interface. The underlying contact mechanics problem is formulated by assuming that the film is a “membrane” and the substrate a graded elastic continuum, and is solved analytically by reducing it to an integral equation. The calculated results are the interfacial shear stress between the film and the graded substrate, the Mode II stress intensity factor at the end of the film, and the axial normal stress in the film. The results indicate that grading the material properties of the substrate helps to decrease the film stresses and the stress intensity factors at the free edges and to lower the axial normal stresses at the midsection where the film is most likely to crack.

Mechanical Modeling of Thin Films Bonded to Functionally Graded Materials

2009 ◽  
Vol 631-632 ◽  
pp. 333-338 ◽  
Author(s):  
Mehmet Ali Guler ◽  
Yusuf Fuat Gülver ◽  
Serkan Dag
Keyword(s):  
Thin Films ◽  
Functionally Graded Materials ◽  
Interfacial Shear Stress ◽  
Contact Problems ◽  
Functionally Graded ◽  
Stress Concentrations ◽  
Graded Materials ◽  
Temperature Changes ◽  
Initiation And Propagation ◽  
Graded Coating

In this study the contact problems of thin films bonded to Functionally Graded Materials (FGM) are considered. In these problems the loading consists of any one or combination of stresses caused by uniform temperature changes and temperature excursions, far field mechanical loading, and residual stresses resulting from film processing or in the manufacturing process of the graded coating. The primary interest in this study is in examining stress concentrations or singularities near the film ends for the purpose of addressing the question of crack initiation and propagation in the substrate or along the interface. The underlying contact mechanics problem is formulated by assuming that the film is a “membrane” and the FGM an elastic continuum, and is solved analytically by reducing it to an integral equation. The calculated results are the interfacial shear stress between the film and the graded substrate, mode II stress intensity factor at the end of the film and the axial normal stress in the film.

A new type of cracks adding to Griffith–Irwin cracks

2019 ◽  
Vol 485 (2) ◽  
pp. 162-165
Author(s):  
V. A. Babeshko ◽  
O. M. Babeshko ◽  
O. V. Evdokimova
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Tip ◽  
Stress Concentrations ◽  
New Type

The distinctions in the description of the conditions of cracking of materials are revealed. For Griffith–Irwin cracks, fracture is determined by the magnitude of the stress-intensity factor at the crack tip; in the case of the new type of cracks, fracture occurs due to an increase in the stress concentrations up to singular concentrations.

scholarly journals Decohesion of Thin Films From Ceramic Substrates

1985 ◽  
Vol 54 ◽  
Author(s):  
R. M. Cannon ◽  
R. M. Fisher ◽  
A. G. Evans
Keyword(s):  
Thin Films ◽  
Interfacial Fracture ◽  
Internal Stresses ◽  
Interfacial Chemistry ◽  
Stress Concentrations ◽  
Ceramic Substrates ◽  
Delamination Buckling ◽  
Formation Conditions ◽  
Mechanical Factors ◽  
Simple Fracture

ABSTRACTDecohesion of thin films from ceramic or semiconductor substrates is strongly influenced by internal stresses in films and stress concentrations from edges or flaws as well as by interfacial fracture energy. Residual stresses can cause spontaneous delamination, splitting and curling of films under tension or delamination, buckling and spal ling of films under residual compression, even with good interfacial bonding. Delamination behavior is considered using simple fracture mechanics models, supplemented with preliminary measurements of interfacial fracture energies. Formation conditions largely control internal stresses in films; whereas fracture energies are dictated by interfacial chemistry and mechanical factors such as plasticity.

Mechanical Modeling of Multilayered Films on an Elastic Substrate—Part I: Analysis

1990 ◽  
Vol 112 (4) ◽  
pp. 309-316 ◽  
Author(s):  
F. Erdogan ◽  
P. F. Joseph
Keyword(s):  
Interfacial Crack ◽  
Strain Energy Release ◽  
Interfacial Zone ◽  
Stress Concentrations ◽  
Elastic Substrate ◽  
Multilayered Films ◽  
Elastic Continuum ◽  
Modeling And Analysis ◽  
Film Substrate ◽  
Homogeneous Temperature

In this paper the basic residual stress problem for multilayered or multiple films on an elastic substrate is considered. The stresses may be caused by a homogeneous temperature variation or slow thermal cycling and by far field mechanical loading. The films are approximated by orthotropic membranes and the substrate is assumed to be an elastic continuum. The interfacial zone is modeled by either an ideal interface or a homogeneous shear layer. The primary interest in the paper is in examining stress concentrations or singularities near the film ends. For the two interface conditions considered, this is done by varying the film/substrate contact angle. Also studied are strain energy release rate for the propagation of an interfacial crack and the direction and the magnitude of the maximum cleavage stress for a possible crack initiation in the substrate. The basic modeling and analysis are considered in Part I. Part II of the paper is devoted to the presentation and discussion of the results.

Preparation and Character Measurements of AlN Films for RF Magnetron Sputtering

2013 ◽  
Vol 663 ◽  
pp. 409-412
Author(s):  
Tai Long Gui ◽  
Si Da Jiang ◽  
Chun Cheng Ban ◽  
Jia Qing Liu
Keyword(s):  
Crystal Structure ◽  
Thin Films ◽  
Refractive Index ◽  
Magnetron Sputtering ◽  
Total Pressure ◽  
Rf Magnetron Sputtering ◽  
Elliptical Polarization ◽  
Dielectric Thin Films ◽  
Temperature Changes ◽  
Sputtering Power

AlN dielectric thin films were deposited on N type Si(100) substrate by reactive radio frequency magnetron sputtering that directly bombardment AlN target under different sputtering-power and total pressure. The crystal structure,composition,surface and refractive index of the thin films were studied by XRD, SEM, AFM and elliptical polarization instrument. The results show that the surface and refractive of the thin films strongly depends on the sputtering-power and total pressure,the good uniformity and smoothness is found at 230 W, Ar flow ratio 5.0 LAr/sccm, substrate temperature 100°Cand 1.2 Pa. The crystal structure of the as-deposited thin-films is amorphous，then it transforms from blende structure to wurtzite structure as the rapid thermal annealing(RTA) temperature changes from 600 to 1200°C. The refractive index also increases with the RTA temperature it is increasing significantly from 800 to 1000°C．

Synchrotron X-Ray Topography of Dislocation Arrays

1986 ◽  
Vol 82 ◽  
Author(s):  
J. C. Bilello
Keyword(s):  
Thin Films ◽  
Plastic Deformation ◽  
Crack Initiation ◽  
Large Scale ◽  
Crack Initiation And Propagation ◽  
X Ray ◽  
Gaas Substrates ◽  
Initiation And Propagation ◽  
Dislocation Arrays

ABSTRACTThe application of relatively low resolution x-ray topography methods, typically ∿ 1 micrometer, is limited in studies which involve large scale dislocation networks. However, the ability to non-destructively image wide areas for “thick” specimens at high intensity with a tunable x-ray source makes the synchrotron an ideal probe for a range of problems previously inaccessible by other methods. Some examples will be discussed such as: (a) crack initiation and propagation in fatigued bicrystals, (b) real-time in situ plastic deformation studies in strain-annealed Mo crystals, and (c) strain distributions in vapor deposited and LPE thin films on Si and GaAs substrates.

Indentation Fracture Studies of a BaTiO3 Thin Film on a Silicon Substrate

1995 ◽  
Vol 403 ◽  
Author(s):  
Wai-Ming Ho ◽  
Ran Fu ◽  
Kai-Tak Wan ◽  
Ji Chou ◽  
Tong-Yi Zhang
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Residual Stresses ◽  
Silicon Substrate ◽  
Square Root ◽  
Indentation Fracture ◽  
Batio3 Thin Film

AbstractIt has been experimentally and theoretically found that the critical applied stress intensity factor for indentation cracking also depends linearly on the reciprocal of the square root of crack length when the indentation fracture technique is used to measure residual stresses in thin films.

scholarly journals The study of thermal radiative properties of silicon wafers with various thin films by temperature changes

2004 ◽  
Vol 2004 (0) ◽  
pp. 379-380
Author(s):  
Takuji KIYA ◽  
Tafumi SASAKI ◽  
Kazushige KIKUTA ◽  
Takemi CHIKAHISA ◽  
Yukio HISHINUMA ◽  
...  
Keyword(s):  
Thin Films ◽  
Silicon Wafers ◽  
Radiative Properties ◽  
Temperature Changes ◽  
Thermal Radiative Properties

Reliability Issues in MEMS Related to Cyclic Loading Conditions

Materials ◽  
2004 ◽  
Author(s):  
Oliver Kraft ◽  
Cynthia A. Volkert
Keyword(s):  
Thin Films ◽  
Thermal Expansion ◽  
Biaxial Tension ◽  
Film Stress ◽  
Effect Of Temperature ◽  
Maximum Temperature ◽  
Film Material ◽  
Sensors And Actuators ◽  
Metal Thin Films ◽  
Temperature Changes

Continuous and patterned metal thin films are widely used in micro-electro-mechanical systems (MEMS). Applications range from reflective coatings in micro-optics to current carrying metallization in sensors and actuators. In these applications, temperature changes of up to several 100°C may occur, and as a result of thermal mismatch between film and substrate materials, large mechanical stresses arise. For instance, gas sensors containing metal thin films are cycled to temperatures well above 300°C[1] and temperatures up to 800°C can be anticipated in the future. Fig. 1 illustrates the effect of temperature changes on the stress development in a thin film, for the case when the substrate has a smaller thermal expansion coefficient than the film. Initially, at room temperature, the metal film under biaxial tension. On heating, the film tends to expand more than the substrate and the tensile stress in the film is reduced. For small stresses, the film and substrate behave elastically, and the slope of the curve in Fig. 1 is given by ΔαEf/(1−νf) where Δα is the difference in thermal expansion coefficients, and Ef and νf are Young’s modulus and Poisson’s ratio of the film material. Above a certain stress (in this case reached at around 250°C on heating), the film begins to plastically deform. On cooling from the maximum temperature of 500°C, the film tends to contract more than the substrate and, as a result, the film stress becomes tensile. The total strain range, Δεth is given by Δεth=ΔαΔT, where ΔT is the temperature range. Thus, for the applications mentioned above, thin metal films encounter strain ranges up to 1% and will undergo both elastic and plastic deformation during use.

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