Surface instability due to initial compressive stress

1973 ◽  
Vol 63 (6-1) ◽  
pp. 1885-1893
Author(s):  
E. J. Brunelle
Keyword(s):  
Compressive Stress ◽  
Initial Stress ◽  
Critical Stress ◽  
Surface Instability ◽  
Shear Moduli ◽  
Finite Slab ◽  
Land Mass ◽  
Linearized Theory ◽  
Two Parameters ◽  
Homogeneous Elasticity

Abstract Utilizing a linearized theory of isotropic, homogeneous elasticity that includes the effects of initial stress, it is demonstrated that Rayleigh and Love surface instabilities occur when the compressive stress reaches appropriate critical values. The Rayleigh surface instability exists for a half-space, as well as for a finite slab, and the critical stress value depends only on Poisson's ratio. The Love surface instability exists for a layer and a substratum, and the critical stress value depends on two parameters: the ratio of the shear moduli and a nondimensional number related to the geometry of the layer. It is suggested that these two instabilities may offer possible, although highly idealized, mechanisms for earthquake initiation and prehistoric land-mass formations such as mountain chains.

Structured Design and Residual Stress for Ni/Ni3Al Multi-Layered Sheet

2012 ◽  
Vol 457-458 ◽  
pp. 118-121 ◽  
Author(s):  
Yong Dong Xiao ◽  
Zhao Hui Hu ◽  
Hong Cheng Gao ◽  
Ji Min Li
Keyword(s):  
Residual Stress ◽  
Compressive Stress ◽  
Thickness Ratio ◽  
Tension Stress ◽  
Fe Method ◽  
Layer Number ◽  
Structured Design ◽  
Two Parameters ◽  
Fracture Work ◽  
Effect Of Microstructure

The residual stress and the effect of microstructure prameters on failure performance of Ni/Ni3Al multi-layered sheet were studied by Correlative theory and FE method. The results showed that the fracture work increases gradually with the increasing of layer number or thickness ratio. However, the rising extent reduced gradually and when the two parameters exceeded a certain value, the fracture work would not be changed. The value of residual stress reached its maximum at the centre and reached its minimum at the edge of multi-layered sheet. Residual stress in Ni layers and Ni3Al layers was compressive stress and tension stress respectively. With increasing of layer number or thickness ratio, compressive stress would rise gradually and compressive stress would reduce gradually.

scholarly journals Interfacial instability in finite elasticity under initial stress

1963 ◽  
Vol 273 (1354) ◽  
pp. 340-344 ◽  
Keyword(s):  
Initial Stress ◽  
Characteristic Equation ◽  
Critical Stress ◽  
Elastic Anisotropy ◽  
Finite Elasticity ◽  
General Characteristic ◽  
Interfacial Instability ◽  
Plane Interface ◽  
Elastic Media

It is shown that two homogeneous elastic media of different rigidities adhering at a plane interface will become unstable at the surface of discontinuity when a certain critical magnitude of initial stress is attained. The general characteristic equation for the interfacial in stability is derived for a general case of elastic anisotropy. The critical stress is evaluated as a function of the rigidity ratio of the two media in the particular case of isotropy.

scholarly journals A Novel Bi-Stable MEMS Membrane Concept Based on a Piezoelectric Thin Film Actuator for Integrated Switching

Proceedings ◽  
2019 ◽  
Vol 2 (13) ◽  
pp. 912 ◽  
Author(s):  
Manuel Dorfmeister ◽  
Bernhard Kössl ◽  
Michael Schneider ◽  
Ulrich Schmid
Keyword(s):  
Thin Film ◽  
Aluminum Nitride ◽  
Compressive Stress ◽  
Piezoelectric Layer ◽  
Critical Stress ◽  
Ground States ◽  
Piezoelectric Thin Film

This study reports on a novel bi-stable actuator with an integrated aluminum nitride (AlN) piezoelectric layer sandwiched between two electrodes. To achieve bistability, the membranes must exceed a characteristic compressive stress value, also called the critical stress. For this purpose, we used highly c-axis orientated stress-controlled AlN with a thickness of 400 nm. First experiments showed, that it is possible to switch between the two stable ground states with at least two rectangular pulses at a frequency of 80 kHz and with a voltage Vpp of 40 V, resulting in a displacement of about 10 µm for each switching direction.

scholarly journals The Rheometric Analysis of the Polymer Modifier’s Properties in the Environment of Hydrated Cement

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1064
Author(s):  
Khrystyna Moskalova ◽  
Aleksej Aniskin ◽  
Goran Kozina ◽  
Božo Soldo
Keyword(s):  
Ethylene Vinyl Acetate ◽  
Test Results ◽  
Structural Failure ◽  
Operating Period ◽  
Shear Moduli ◽  
Shear Rates ◽  
Lower Shear ◽  
Calcium Hydrosilicates ◽  
Multifunctional Additives ◽  
Two Parameters

This paper investigates the effect of polymer modifiers (re-dispersible powder, multifunctional additives, methylhydroxyethylcellulose) on the rheological behavior of emulsions, saturated of calcium hydrosilicates to simulate a hydrating cement structure. The subjects of the study were modified emulsions which had varied concentrations of each additive and they were examined comparatively to a base emulsion. Tests were performed with a CR-rheometer (“Himpribor-1”, Tula, Russia) applying the Searle measuring principle at various shear rates to characterize viscosity properties. The performance of modified mixtures within the operating period was analyzed by using two parameters—effective viscosity (η) and the proportion of structural failure (|m|). The test results showed that the most important factor influencing rheological characteristics is the addition of methylhydroxyethylcellulose additive—the higher additive amount in the emulsion, the higher the viscosity. Furthermore it was noted in the work that adding olefin sulfonate sodium salt causes reduced viscosities as well as lower shear moduli. If ethylhydroxyethylcellulose and ethylene vinyl acetate additives are used in the same mixture together, the rate of structural failure |m| can be relatively similar and low regardless of whether the mixture has large or small viscosity values.

Study on Optimum Structure and Residual Stress of Ti/TiAl Micro-Laminated Sheet

2011 ◽  
Vol 474-476 ◽  
pp. 1137-1140
Author(s):  
Li Ma ◽  
Lu Ju He ◽  
Hai Bo Wang ◽  
Gu Ping Wang
Keyword(s):  
Residual Stress ◽  
Compressive Stress ◽  
Thickness Ratio ◽  
Tension Stress ◽  
Optimum Structure ◽  
Fe Method ◽  
Layer Number ◽  
Microstructure Parameters ◽  
Two Parameters ◽  
Fracture Work

The residual stress and the effect of microstructure parameters on failure performance of Ti/TiAl micro-laminated sheet were studied by Correlative theory and FE method. The results showed that the fracture work increases gradually with the increasing of layer number or thickness ratio. However, the rising extent reduced gradually and when the two parameters exceeded a certain value, the fracture work would not be changed. The value of residual stress reached its maximum at the centre and reached its minimum at the edge of micro-laminated sheet. Residual stress in Ti layers and Ti-Al layers was compressive stress and tension stress respectively. With increasing of layer number or thickness ratio, compressive stress would rise gradually and compressive stress would reduce gradually.

Herringbone Buckling Patterns of Compressed Thin Films on Compliant Substrates

2004 ◽  
Vol 71 (5) ◽  
pp. 597-603 ◽  
Author(s):  
X. Chen ◽  
John W. Hutchinson
Keyword(s):  
Thin Films ◽  
Thermal Expansion ◽  
Stress State ◽  
Compressive Stress ◽  
Critical Stress ◽  
Metal Film ◽  
Minimum Energy ◽  
Thin Metal Film ◽  
Thermal Expansion Mismatch ◽  
Compliant Substrates

A thin metal film vapor deposited on thick elastomer substrate develops an equi-biaxial compressive stress state when the system is cooled due to the large thermal expansion mismatch between the elastomer and the metal. At a critical stress, the film undergoes buckling into a family of modes with short wavelengths characteristic of a thin plate on a compliant elastic foundation. As the system is further cooled, a highly ordered herringbone pattern has been observed to develop. Here it is shown that the herringbone mode constitutes a minimum energy configuration among a limited set of competing modes.

Symmetrical Buckling of Right-Angled Isosceles Triangular Plates

1954 ◽  
Vol 5 (3) ◽  
pp. 131-143 ◽  
Author(s):  
W. H. Wittrick
Keyword(s):  
Boundary Conditions ◽  
Compressive Stress ◽  
Critical Stress ◽  
Uniform Compression ◽  
Triangular Plate ◽  
Suitable Amount ◽  
The Right

SummaryThe problem considered is that of the buckling of a right-angled isosceles triangular plate subjected to shear along the two perpendicular edges together with uniform compression in all directions. Four combinations of boundary conditions are considered, and the buckle is assumed to be symmetrical about the bisector of the right angle. In each case it is shown that, if the plate is subjected to shear only, the critical stress is changed considerably upon reversal of the shear. The larger value occurs when the shear is tending to decrease the right angle. Because of this fact, the interaction curve, giving critical combinations of compression and shear, is unsymmetrical and the critical compressive stress can be appreciably increased by the application of a suitable amount of shear.

Effects of initial stress state on the subsurface stress distribution after ultrasonic impact treatment on thick specimens

2020 ◽  
pp. 030932472097683
Author(s):  
Chuan Liu ◽  
Jiabin Shen ◽  
Changhua Lin ◽  
Jianfei Wang ◽  
Jianxin Wang
Keyword(s):  
Stress State ◽  
Stress Distribution ◽  
Tensile Stress ◽  
Compressive Stress ◽  
Initial Stress ◽  
Correction Method ◽  
Welding Residual Stress ◽  
Initial Stress State ◽  
Ultrasonic Impact Treatment ◽  
Before And After

Thick welded specimens with different initial stress states were prepared and treated with the ultrasonic impact treatment (UIT). The subsurface stresses before and after UIT were measured by the X-ray diffraction (XRD) method combined with layer removal. The measured results were corrected based on the finite element correction method. The effects of initial high tensile stress and low compressive stress on the in-depth after-UIT stress distributions were investigated. The results show that initial stress has no effects on the stresses induced by the UIT within 1 mm depth and within that depth, UIT can induce almost the same longitudinal and transverse stress curves beneath the surface with a peak compressive stress close to the material yield strength at the depth of near 0.6 mm and 0.8 mm. UIT induces almost the same longitudinal and transverse stresses along with the measured depth under initial low compressive stress state. While under the initial high tensile stress state, the initial stress dominates the final stress distribution over 1 mm depth. Initial high tensile stress (welding residual stress) can reduce the depth of the after-UIT compressive stresses to 62.5% to 75% of that under the initial low-compressive stress state.

Active Surface Topographies in Constrained Hydrogel Films

2009 ◽  
Vol 1234 ◽  
Author(s):  
Ophir Ortiz ◽  
Ajay Vidyasagar ◽  
Ryan Toomey
Keyword(s):  
Hydrogen Bonding ◽  
Surface Topography ◽  
Compressive Stress ◽  
Cell Attachment ◽  
Active Surface ◽  
Surface Instability ◽  
Mechanical Instability ◽  
Free Surfaces ◽  
Patterned Films ◽  
Hydrogel Films

AbstractPeriodic wrinkles or corrugations can appear on the free surfaces of constrained hydrogel films. The constraint generates a residual compressive stress that is partially relieved through deviation of free surfaces from a planar configuration. The morphology, amplitude and wavelength of the surface instability are generally well-defined and depend on the strength of the constraint. If swelling of the hydrogel overcomes the constraint, the film can slip along its substrate, altering the resultant compressive stress and surface topography. By tuning this slippage, we aim to direct the surface features presented by thin hydrogel films. Active control of surface morphology could have important implications in several applications ranging from sensors to controlled cell attachment and detachment.In this work, we discuss a method of tuning the amount of slippage and surface topography of patterned poly(N-isopropylacrylamide) (poly-NIPAAm) films. The films were fabricated from photo-crosslinkable polymers comprising NIPAAm and photo-active methacroyloxy-benzophenone (MaBP) monomers. The patterned films were anchored to a substrate through a hydrogen-bonding self-assembled monolayer. The relationship between pattern geometry, pattern dimensions, and solvent were investigated with respect to the mechanical instability generated at the free surface. We observed that the wavelength, width, and amplitude of the instability always increased with the thickness of the polymer pattern. The morphology of the surface instability, however, was especially sensitive to thickness of the pattern, the solvent, and the spatial position with respect to the edge of polymer pattern. If the slippage of the film against the substrate is minimal, a wrinkle pattern in the form of bicusps was observed. If the compressive stress exceeded the hydrogen-bonding anchors, slippage of the film generated either a blister pattern or a honeycomb pattern.

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