scholarly journals The role of adhesion in contact mechanics

2019 ◽  
Vol 16 (151) ◽  
pp. 20180738 ◽  
Author(s):  
M. Ciavarella ◽  
J. Joe ◽  
A. Papangelo ◽  
J. R. Barber
Keyword(s):  
Contact Mechanics ◽  
Contact Problems ◽  
Soft Materials ◽  
Adhesive Contact ◽  
Industrial Systems ◽  
Linear Elastic ◽  
Elastic Fracture ◽  
To Come ◽  
Interacting Surfaces

Adhesive (e.g. van der Waals) forces were not generally taken into account in contact mechanics until 1971, when Johnson, Kendall and Roberts (JKR) generalized Hertz’ solution for an elastic sphere using an energetic argument which we now recognize to be analogous to that used in linear elastic fracture mechanics. A significant result is that the load–displacement relation exhibits instabilities in which approaching bodies ‘jump in’ to contact, whereas separated bodies ‘jump out’ at a tensile ‘pull-off force’. The JKR approach has since been widely used in other geometries, but at small length scales or for stiffer materials it is found to be less accurate. In conformal contact problems, other instabilities can occur, characterized by the development of regular patterns of regions of large and small traction. All these instabilities result in differences between loading and unloading curves and consequent hysteretic energy losses. Adhesive contact mechanics has become increasingly important in recent years with the focus on soft materials (which generally permit larger areas of the interacting surfaces to come within the range of adhesive forces), nano-devices and the analysis of bio-systems. Applications are found in nature, such as insect attachment forces, in nano-manufacturing, and more generally in industrial systems involving rubber or polymer contacts. In this paper, we review the strengths and limitations of various methods for analysing contact problems involving adhesive tractions, with particular reference to the effect of the inevitable roughness of the contacting surfaces.

CAN MUSHROOM-SHAPED FIBERS ENHANCE THE BIO-ADHESIVE PERFORMANCE?

2015 ◽  
Vol 15 (05) ◽  
pp. 1550068 ◽  
Author(s):  
YAN LIU ◽  
HONG LIU ◽  
YANFEI GAO
Keyword(s):  
Adhesive Contact ◽  
Adhesive Systems ◽  
Crack Bridging ◽  
Linear Elastic ◽  
Scale Unit ◽  
Uniform Interface ◽  
Material Contact ◽  
Cylindrical Fiber ◽  
Elastic Fracture ◽  
Adhesive Performance

In biological and artificial adhesive systems, the lowest-scale unit is oftentimes the adhesive contact between a mushroom-shaped fiber and the surrounding material. Contact mechanics analysis in literature suggests that such a shape leads to more uniform interface stress, and thus a more superior adhesive performance, than the cylindrical fiber. In this work, we prove that this concept only works in the limit of linear elastic fracture mechanics (LEFM). When the interface behavior has a large crack bridging zone, de-adhesion occurs more easily in the center of mushroom-shaped indenter and the pull-off force becomes lower than that of cylindrical fiber. Combining the analysis of stress intensity factor and crack bridging characteristics, and tuning the substrate by a layered structure, we have established design rules that can significantly widen the parametric space in which the mushroom-shaped indenter enhances the bio-adhesive performance.

scholarly journals Linear elastic fracture simulation directly from CAD: 2D NURBS-based implementation and role of tip enrichment

2016 ◽  
Vol 204 (1) ◽  
pp. 55-78 ◽  
Author(s):  
X. Peng ◽  
E. Atroshchenko ◽  
P. Kerfriden ◽  
S. P. A. Bordas
Keyword(s):  
Linear Elastic ◽  
Fracture Simulation ◽  
Elastic Fracture

Fracture mechanics in design and service: ‘living with defects’ - Fracture mechanics of non-metallic materials

1981 ◽  
Vol 299 (1446) ◽  
pp. 59-72 ◽  
Keyword(s):  
Fracture Mechanics ◽  
Plane Strain ◽  
Design Criterion ◽  
Simple Extension ◽  
Metallic Materials ◽  
Environmental Behaviour ◽  
Linear Elastic ◽  
Wide Range ◽  
Elastic Fracture

An outline of linear elastic fracture mechanics (l.e.f.m.) is given with an emphasis on those aspects most relevant to non-metallic materials. Provided that the nonlinear zone of energy absorption surrounding the crack tip is small compared with other dimensions, then a K e or G e value may be used. A simple extension of this concept can include elastically nonlinear materials such as rubber. Examples of the use of this method are then given for polymers, rubber and wood, and include some discussion of the difficulties involving plane strain-plane stress transitions. The role of K e as a characterizing parameter in time-dependent, fatigue and environmental behaviour is then described with several examples, and it is concluded that plane strain fractures may be achieved with a wide range of values for any material. The consequences of this in choosing a design criterion are then discussed.

scholarly journals Ice shelf rift propagation: stability, three dimensional effects, and the role of marginal weakening

2019 ◽  
Author(s):  
Bradley Paul Lipovsky
Keyword(s):  
Three Dimensional ◽  
Two Dimensional ◽  
Ice Shelf ◽  
Linear Elastic ◽  
Partial Contact ◽  
Rift Propagation ◽  
Elastic Fracture ◽  
Shelf Margins ◽  
Determining Factor

Abstract. Understanding the processes that govern ice shelf extent are of fundamental importance to improved estimates of future sea level rise. In present-day Antarctica, ice shelf extent is most commonly determined by the propagation of through-cutting fractures called ice shelf rifts. Here, I present the first three-dimensional analysis of ice shelf rift propagation. I present a linear elastic fracture mechanical (LEFM) description of rift propagation. The model predicts that rifts may be stabilized when buoyant flexure results in contact at the tops of the near-tip rift walls. This stabilizing tendency may be overcome, however, by processes that act in the ice shelf margins. In particular, both marginal weakening and the advection of rifts into an ice tongue are shown to be processes that may trigger rift propagation. Marginal shear stress is shown to be the determining factor that governs these types of rift instability. I furthermore show that rift stability is closely related to the transition from uniaxial to biaxial extension known as the compressive arch. Although the partial contact of rift walls is fundamentally a three-dimensional process, I demonstrate that it may be parameterized within more numerically efficient two-dimensional calculations. This study provides a step towards a description of calving physics that is based in fracture mechanics.

scholarly journals Ice shelf rift propagation: stability, three-dimensional effects, and the role of marginal weakening

2020 ◽  
Vol 14 (5) ◽  
pp. 1673-1683
Author(s):  
Bradley Paul Lipovsky
Keyword(s):  
Three Dimensional ◽  
Tangential Displacement ◽  
Ice Shelf ◽  
Linear Elastic ◽  
Partial Contact ◽  
Rift Propagation ◽  
Iceberg Calving ◽  
Elastic Fracture ◽  
Shelf Margins

Abstract. Understanding the processes that govern ice shelf extent is important to improving estimates of future sea-level rise. In present-day Antarctica, ice shelf extent is most commonly determined by the propagation of through-cutting fractures called ice shelf rifts. Here, I present the first three-dimensional analysis of ice shelf rift propagation. I model rifts using the assumptions of linear elastic fracture mechanics (LEFM). The model predicts that rifts may be stabilized (i.e., stop propagating) when buoyant flexure results in the partial contact of rift walls. This stabilizing tendency may be overcome, however, by processes that act in the ice shelf margins. In particular, loss of marginal strength, modeled as a transition from zero tangential displacement to zero tangential shear stress, is shown to favor rift propagation. Rift propagation may also be triggered if a rift is carried with the ice flow (i.e., advected) out of an embayment and into a floating ice tongue. I show that rift stability is closely related to the transition from uniaxial to biaxial extension known as the compressive arch. Although the partial contact of rift walls is fundamentally a three-dimensional process, I demonstrate that it may be parameterized within more numerically efficient two-dimensional calculations. This study constitutes a step towards a first-principle description of iceberg calving due to ice shelf rift propagation.

Adhesive contact of a rigid circular cylinder to a soft elastic substrate – the role of surface tension

Soft Matter ◽  
2015 ◽  
Vol 11 (19) ◽  
pp. 3844-3851 ◽  
Author(s):  
Tianshu Liu ◽  
Anand Jagota ◽  
Chung-Yuen Hui
Keyword(s):  
Surface Tension ◽  
Circular Cylinder ◽  
Contact Mechanics ◽  
Half Space ◽  
Elastic Material ◽  
Adhesive Contact ◽  
Elastic Substrate ◽  
Rigid Cylinder

This article studies the effects of surface tension on the adhesive contact mechanics of a long rigid cylinder on an infinite half space comprising an incompressible elastic material.

scholarly journals Explicit transformation between non-adhesive and adhesive contact problems by means of the classical Johnson–Kendall–Roberts formalism

2021 ◽  
Vol 379 (2203) ◽  
pp. 20200374
Author(s):  
Nikolay V. Perepelkin ◽  
Feodor M. Borodich
Keyword(s):  
Rotational Symmetry ◽  
A Priori ◽  
Contact Problems ◽  
Adhesive Contact ◽  
Elastic Half Space ◽  
Principle Of Superposition ◽  
Linear Elastic ◽  
Thin Elastic Layer ◽  
Force Displacement ◽  
Superposition Of Solutions

The classic Johnson–Kendall–Roberts (JKR) contact theory was developed for frictionless adhesive contact between two isotropic elastic spheres. The advantage of the classical JKR formalism is the use of the principle of superposition of solutions to non-adhesive axisymmetric contact problems. In the recent years, the JKR formalism has been extended to other cases, including problems of contact between an arbitrary-shaped blunt axisymmetric indenter and a linear elastic half-space obeying rotational symmetry of its elastic properties. Here the most general form of the JKR formalism using the minimal number of a priori conditions is studied. The corresponding condition of energy balance is developed. For the axisymmetric case and a convex indenter, the condition is reduced to a set of expressions allowing explicit transformation of force–displacement curves from non-adhesive to corresponding adhesive cases. The implementation of the developed theory is demonstrated by presentation of a two-term asymptotic adhesive solution of the contact between a thin elastic layer and a rigid punch of arbitrary axisymmetric shape. Some aspects of numerical implementation of the theory by means of Finite-Element Method are also discussed. This article is part of a discussion meeting issue ‘A cracking approach to inventing new tough materials: fracture stranger than friction’.

The role of (bio)surfactant sorption in promoting the bioavailability of nutrients localized at the solid-water interface

1999 ◽  
Vol 39 (7) ◽  
pp. 91-98 ◽  
Author(s):  
Ryan N. Jordan ◽  
Eric P. Nichols ◽  
Alfred B. Cunningham
Keyword(s):  
Mass Transfer ◽  
Cell Membrane ◽  
Substrate Concentration ◽  
Water Interface ◽  
Industrial Systems ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
Surfactant Sorption

Bioavailability is herein defined as the accessibility of a substrate by a microorganism. Further, bioavailability is governed by (1) the substrate concentration that the cell membrane “sees,” (i.e., the “directly bioavailable” pool) as well as (2) the rate of mass transfer from potentially bioavailable (e.g., nonaqueous) phases to the directly bioavailable (e.g., aqueous) phase. Mechanisms by which sorbed (bio)surfactants influence these two processes are discussed. We propose the hypothesis that the sorption of (bio)surfactants at the solid-liquid interface is partially responsible for the increased bioavailability of surface-bound nutrients, and offer this as a basis for suggesting the development of engineered in-situ bioremediation technologies that take advantage of low (bio)surfactant concentrations. In addition, other industrial systems where bioavailability phenomena should be considered are addressed.

Reconsidering American Power

2020 ◽  
Keyword(s):  
Social Sciences ◽  
Human Rights ◽  
Postcolonial Studies ◽  
Human Condition ◽  
American Power ◽  
Global Environmental ◽  
The Social ◽  
State Sponsorship ◽  
To Come

Postcolonial studies, postmodern studies, even posthuman studies emerge, and intellectuals demand that social sciences be remade to address fundamentals of the human condition, from human rights to global environmental crises. Since these fields owe so much to American state sponsorship, is it easier to reimagine the human and the modern than to properly measure the pervasive American influence? Reconsidering American Power offers trenchant studies by renowned scholars who reassess the role of the social sciences in the construction and upkeep of the Pax Americana and the influence of Pax Americana on the social sciences. With the thematic image for this enterprise as the ‘fiery hunt’ for Ahab’s whale, the contributors pursue realities behind the theories, and reconsider the real origins and motives of their fields with an eye on what will deter or repurpose the ‘fiery hunts’ to come, by offering a critical insider’s view.

Capillary Imbibition Dynamics in Porous Media

2014 ◽  
Author(s):  
Swayamdipta Bhaduri ◽  
Pankaj Sahu ◽  
Siddhartha Das ◽  
Aloke Kumar ◽  
Sushanta K. Mitra
Keyword(s):  
Porous Medium ◽  
Porous Media ◽  
Paper Strip ◽  
Capillary Imbibition ◽  
Flow Physics ◽  
Fundamental Understanding ◽  
Paper Based Microfluidics ◽  
To Come

The phenomenon of capillary imbibition through porous media is important both due to its applications in several disciplines as well as the involved fundamental flow physics in micro-nanoscales. In the present study, where a simple paper strip plays the role of a porous medium, we observe an extremely interesting and non-intuitive wicking or imbibition dynamics, through which we can separate water and dye particles by allowing the paper strip to come in contact with a dye solution. This result is extremely significant in the context of understanding paper-based microfluidics, and the manner in which the fundamental understanding of the capillary imbibition phenomenon in a porous medium can be used to devise a paper-based microfluidic separator.

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