scholarly journals Strength statistics of adhesive contact between a fibrillar structure and a rough substrate

2007 ◽  
Vol 5 (21) ◽  
pp. 441-448 ◽  
Author(s):  
Pankaj K Porwal ◽  
Chung Yuen Hui
Keyword(s):  
Adhesion Strength ◽  
Probability Distributions ◽  
Adhesive Contact ◽  
Strength Distribution ◽  
Fibrillar Structure ◽  
Substrate Roughness ◽  
Equal Distribution ◽  
Fibril Structure ◽  
Attachment Strength ◽  
Fibril Length

Equal distribution of load among fibrils in contact with a substrate is an important characteristic of fibrillar structures used by many small animals and insects for contact and adhesion. This is in contrast with continuum systems where stress concentration dominates interfacial failure. In this work, we study how adhesion strength of a fibrillar system depends on substrate roughness and variability of the fibril structure, which are modelled using probability distributions for fibril length and fibril attachment strength. Monte Carlo simulations are carried out to determine the adhesion strength statistics where fibril length follows normal or uniform distribution and attachment strength has a power-law form. Our results indicate that the strength distribution is Gaussian (normal) for both the uniform and the normal distributions for length. However, the fibrillar structure having normally distributed lengths has higher strength and lower toughness than one having uniformly distributed lengths. Our simulations also show that an increase in the compliance of the fibrils can compensate for both the substrate roughness and the attachment strength variation. We also show that, as the number of fibrils n increases, the load-carrying efficiency of each fibril goes down. For large n , this effect is found to be small. Furthermore, this effect is compensated by the fact that the standard deviation of the adhesive strength decreases as .

Tensile, Torsional and Bending Strain at the Adhesive Rupture of an Iced Substrate

2009 ◽  
Author(s):  
Caroline Laforte ◽  
Jean-Louis Laforte
Keyword(s):  
Adhesion Strength ◽  
Ice Thickness ◽  
Stress And Strain ◽  
Substrate Roughness ◽  
Mean Values ◽  
Time Deformation ◽  
Bending Strain ◽  
Load Cells ◽  
The Mean ◽  
Major Factors

In order to develop an effective deicing device using mechanical deformation of substrates, the adhesive and/or cohesive strains of ice at rupture were measured for three different modes of solicitation: tensile, twisting and bending. A total of 108 icing/deicing tests were conducted with aluminum and nylon samples covered with hard rime ice deposits 2, 5, and 10 mm thick strained at various strains rates in brittle regime at −10°C. Real time deformation was precisely monitored using a strain gage fixed to the A1 interface, and force by means of load cells and a torque-meter. Deicing strain was determined at the time of ice detachment, which corresponds to a visible, instant change in the slope of stress-strain curves. The mean values of deicing strains, ε %, measured in tensile, torsion and bending experiments are respectively, 0.037 ± 0.015%, 0.043 ± 0.023% and 0.004 ± 0.003% As for adhesion strength, the highest values were obtained in tension, 4 MPa ± 50%, and the lowest in bending, 0.014 MPa ± 36%. In torsion, the value was intermediary, at 1.26 MPa ± 67%. Measurements also showed that deicing stress and strain tended to increase with substrate roughness, whereas they decrease with increasing ice thicknesses. In summary, this work points out the effects of two major factors on ice adhesion strength, the solicitation mode and the ice thickness. Finally these results suggest that the first criteria for a mechanical deicing device has to satisfy to be effective is to have the capacity to generating a strain at around 0.04% ice/substrate interface.

scholarly journals Adhesive strength in a high voltage mica insulation system

2019 ◽  
Vol 140 ◽  
pp. 11006
Author(s):  
Tatiana Shikova
Keyword(s):  
Adhesion Strength ◽  
High Voltage ◽  
Adhesive Strength ◽  
Adhesive Contact ◽  
Test Method ◽  
Technological Parameters ◽  
Contact Materials ◽  
Pressing Process ◽  
Thermal Pressing ◽  
Degree Of Curing

The problem of maintaining a monolithic high-voltage mica insulation made by the Resin Rich technology for windings of electrical machines and conductors is considered. The violation of solidity like delaminations and peeling off from conductor can happen both during the process of manufacturing and during exploitation of constructions. The possibility of breaking the solidity is directly related to the magnitude of adhesion strength. Design and manufacturing technology of samples in laboratory and industrial conditions to determine the adhesion strength were developed. Adhesive strength is determined by the method of shear and tensile test method between insulation layers and in system of metal- mica insulation.The created method for the manufacture of samples made it possible to test samples with various designs of adhesive contact, materials of adhesive contact and technological parameters of the pressing process. The adhesion strength depends on the parameters of the thermal pressing process and the degree of curing of the binder in the initial resin rich tape. Adhesive contact of mica insulation to metal through fiberglass is more durable than through film

scholarly journals Design of biomimetic fibrillar interfaces: 2. Mechanics of enhanced adhesion

2004 ◽  
Vol 1 (1) ◽  
pp. 35-48 ◽  
Author(s):  
C.-Y. Hui ◽  
N. J. Glassmaker ◽  
T. Tang ◽  
A. Jagota
Keyword(s):  
Interfacial Strength ◽  
Load Sharing ◽  
Adhesive Contact ◽  
Work Of Adhesion ◽  
Cross Sectional ◽  
Flat Interface ◽  
Dimensionless Function ◽  
The Stability ◽  
Fibril Length ◽  
Perfect Interface

This study addresses the strength and toughness of generic fibrillar structures. We show that the stress σ c required to pull a fibril out of adhesive contact with a substrate has the form σ c = σ 0 Φ( χ ). In this equation, σ 0 is the interfacial strength, Φ( χ ) is a dimensionless function satisfying 0=Φ( χ )=1 and χ is a dimensionless parameter that depends on the interfacial properties, as well as the fibril stiffness and radius. Pull-off is flaw sensitive for χ ≫1, but is flaw insensitive for χ <1. The important parameter χ also controls the stability of a homogeneously deformed non-fibrillar (flat) interface. Using these results, we show that the work to fail a unit area of fibrillar surface can be much higher than the intrinsic work of adhesion for a flat interface of the same material. In addition, we show that cross-sectional fibril dimensions control the pull-off force, which increases with decreasing fibril radius. Finally, an increase in fibril length is shown to increase the work necessary to separate a fibrillar interface. Besides our calculations involving a single fibril, we study the concept of equal load sharing (ELS) for a perfect interface containing many fibrils. We obtain the practical work of adhesion for an idealized fibrillated interface under equal load sharing. We then analyse the peeling of a fibrillar surface from a rigid substrate and establish a criterion for ELS.

Tunable adhesion of an elastic pillar by pressurizing inner cavity

2021 ◽  
pp. 135065012110182
Author(s):  
Turgay Eray
Keyword(s):  
Adhesion Strength ◽  
Smooth Surface ◽  
Adhesive Contact ◽  
Adhesive Force ◽  
Membrane Thickness ◽  
Cavity Pressure ◽  
Flat Punch ◽  
Contact Type ◽  
Inner Pressure ◽  
Rigid Smooth

This work studies the effect of a cavity with inner pressure on the adhesion of circular pillars with a flat tip in contact with a rigid smooth surface. The inner cavity of pillars is pressurized positively before the contact. The effect of the cavity on the adhesion is examined for different cavity diameters and different membrane thicknesses over the cavity. The shape of the tip of the pillars is changed in accordance with the cavity dimension and the positive cavity pressure, which allows the change of an adhesive contact type from a flat-punch adhesive contact to a spherical adhesive contact that results in tunable adhesion strength of circular pillars. The results demonstrate that having an inner cavity reduces the adhesion, where the cavity diameter is more effective than the membrane thickness over the cavity on the reduction of the adhesive force. Applying pressure to the inner cavity of the pillars changes the sphericity, which alters the adhesive force accordingly. The sphericity 0.1 almost has no effect on the tunable adhesion strength, where the higher sphericity results in the reduction of the adhesive force from high adhesive force to low adhesive force linearly with a tunable efficiency between 95% and 98%.

OS1803 Influence of substrate roughness on adhesion strength of cold sprayed coatings

2014 ◽  
Vol 2014 (0) ◽  
pp. _OS1803-1_-_OS1803-2_
Author(s):  
Yuta WATANABE ◽  
Takayuki UCHIDA ◽  
Motohiro YAMADA ◽  
Masahiro FUKUMOTO
Keyword(s):  
Adhesion Strength ◽  
Substrate Roughness ◽  
Influence Of Substrate ◽  
Sprayed Coatings

scholarly journals Construction and Analysis of Fractional Multifactorial Designs To Study Attachment Strength and Transfer of Listeria monocytogenes from Pure or Mixed Biofilms after Contact with a Solid Model Food

2006 ◽  
Vol 72 (4) ◽  
pp. 2313-2321 ◽  
Author(s):  
Graziella Midelet ◽  
André Kobilinsky ◽  
Brigitte Carpentier
Keyword(s):  
Listeria Monocytogenes ◽  
Adhesion Strength ◽  
Polymer Materials ◽  
Processing Plant ◽  
Bacterial Populations ◽  
Tryptone Soya Agar ◽  
Plant Environment ◽  
Low Concentrations ◽  
Attachment Strength ◽  
Cleaning And Disinfection

ABSTRACT The aim of this study was to establish which of seven factors influence the adhesion strength and hence bacterial transfer between biofilms containing Listeria monocytogenes (pure and two-species biofilms) and tryptone soya agar (TSA) as a solid organic surface. The two-species biofilms were made of L. monocytogenes and one of the following species of bacteria: the nonpathogenic organisms Kocuria varians, Pseudomonas fluorescens, and Staphylococcus sciuri and CCL 63, an unidentified gram-negative bacterium isolated from the processing plant environment. We used biofilms prepared under conditions simulating open surfaces in meat-processing sites. The biofilm's adhesion strength and population were evaluated by making 12 contacts on a given whole biofilm (4.5 cm2), using a new slice of a sterilized TSA cylinder for each contact, and plotting the logarithm CFU · cm−2 detached by each contact against the contact number. Three types of detachment kinetics were observed: biphasic kinetics, where the first slope may be either positive or negative, and monophasic kinetics. The bacteria that resisted a chlorinated alkaline product and a glutaraldehyde- and quaternary ammonium-based disinfectant had greater adhesion strengths than those determined for untreated biofilms. One of the four non-Listeria strains studied, Kocuria varians CCL 56, favored both the attachment and detachment of L. monocytogenes. The stainless steel had smaller bacterial populations than polymer materials, and non-Listeria bacteria adhered to it less strongly. Our results helped to evaluate measures aimed at controlling the immediate risk, linked to the presence of a large number of CFU in a foodstuff, and the delayed risk, linked to the persistence of L. monocytogenes and the occurrence of slightly contaminated foods that may become dangerous if L. monocytogenes multiplies during storage. Cleaning and disinfection reduce the immediate risk, while reducing the delayed risk should be achieved by lowering the adhesion strength, which the sanitizers used here cannot do at low concentrations.

scholarly journals Modification of the Surface of a Substrate by Adsorbed Polymer Interlayers for the Control of Adhesion

1996 ◽  
Vol 14 (4) ◽  
pp. 259-266 ◽  
Author(s):  
I. Luzinov ◽  
A. Voronov ◽  
S. Minko
Keyword(s):  
Contact Angle ◽  
Adhesion Strength ◽  
Methacrylic Acid ◽  
Adhesive Joint ◽  
Adhesive Contact ◽  
Polymer Layers ◽  
Angle Measurements ◽  
Adsorbed Polymer ◽  
Contact Angle Measurements ◽  
Modification Of The Surface

A good correlation between the parameters of an adsorbed polymer interlayer and the strength of an adhesive joint was observed. Such polymer interlayers were obtained beforehand by the adsorption of polyacrylates, polymethacrylates and their copolymers with acrylic and methacrylic acid from solution on to the surface of aluminium plates. Oligocarbomethacrylate was used as an adhesive. Contact angle measurements were employed for investigating the structure of the adsorbed polymer layers. It was found out that the fraction of sites screened by the polymer, the fraction of the substrate available for the adhesive and the fraction of attached segments affects the adhesion strength.

INFLUENCE OF INTERFACIAL LAYER THICKNESS AND SUBSTRATE ROUGHNESS ON ADHESION OF TiN COATINGS DEPOSITED AT LOW TEMPERATURES BY IBAD

2011 ◽  
Vol 18 (03n04) ◽  
pp. 83-90 ◽  
Author(s):  
DAMIR KAKAS ◽  
PAL TEREK ◽  
LAZAR KOVACEVIC ◽  
ALEKSANDAR MILETIC ◽  
BRANKO SKORIC
Keyword(s):  
Adhesion Strength ◽  
Low Temperatures ◽  
Interfacial Layer ◽  
Steel Substrate ◽  
Ion Beam ◽  
Substrate Roughness ◽  
Average Roughness ◽  
Carburized Steel ◽  
Tin Coatings ◽  
The One

Ion beam assisted deposition (IBAD) was applied to produce TiN coatings on carburized steel substrates. Low deposition temperatures (~50°C) were applied to prevent distortion and softening of previously heat-treated substrates. Mechanical properties of all studied coatings are comparable to those obtained at usually used high temperatures. In order to improve adhesion between TiN coating and substrate, an interfacial layer was prepared by ion beam mixing of Ti atoms and steel substrate. The adhesion strength evaluation revealed significant improvement compared to the coatings produced without the ion beam mixed interfacial layer. Adhesion increased with increase in thickness of the interfacial layer. Substrate roughness was varied systematically in order to determine its influence on adhesion strength. The research was conducted for a rarely studied domain of low roughness (Average roughness Ra below 50 nm). The results of scratch tests revealed improvement of adhesion with increase in substrate roughness. This adhesion trend is different from the one reported by other authors who used rougher substrates. Two groups of opposing mechanisms acting during adhesion testing were identified. It appears that there exists an optimum roughness below which adhesion strength increases, and above which it decreases with the increase in substrate roughness. Accordingly, applying an expensive surface finish does not have to be a guarantee for achieving the appropriate adhesion of TiN coatings deposited at low temperatures.

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