scholarly journals Effect of shear forces and ageing on the compliance of adhesive pads in adult cockroaches

2015 ◽  
Vol 218 (17) ◽  
pp. 2775-2781 ◽  
Author(s):  
Y. Zhou ◽  
A. Robinson ◽  
C. Viney ◽  
W. Federle
Keyword(s):  
Shear Forces ◽  
Adhesive Pads

scholarly journals Shear-sensitive adhesion enables size-independent adhesive performance in stick insects

2019 ◽  
Vol 286 (1913) ◽  
pp. 20191327 ◽  
Author(s):  
David Labonte ◽  
Marie-Yon Struecker ◽  
Aleksandra V. Birn-Jeffery ◽  
Walter Federle
Keyword(s):  
Body Weight ◽  
Adhesive Force ◽  
Whole Body ◽  
Small Animals ◽  
Shear Forces ◽  
Stick Insects ◽  
Adhesive Pads ◽  
The Difference ◽  
Large Animals ◽  
Adhesive Performance

The ability to climb with adhesive pads conveys significant advantages and is widespread in the animal kingdom. The physics of adhesion predict that attachment is more challenging for large animals, whereas detachment is harder for small animals, due to the difference in surface-to-volume ratios. Here, we use stick insects to show that this problem is solved at both ends of the scale by linking adhesion to the applied shear force. Adhesive forces of individual insect pads, measured with perpendicular pull-offs, increased approximately in proportion to a linear pad dimension across instars. In sharp contrast, whole-body force measurements suggested area scaling of adhesion. This discrepancy is explained by the presence of shear forces during whole-body measurements, as confirmed in experiments with pads sheared prior to detachment. When we applied shear forces proportional to either pad area or body weight, pad adhesion also scaled approximately with area or mass, respectively, providing a mechanism that can compensate for the size-related loss of adhesive performance predicted by isometry. We demonstrate that the adhesion-enhancing effect of shear forces is linked to pad sliding, which increased the maximum adhesive force per area sustainable by the pads. As shear forces in natural conditions are expected to scale with mass, sliding is more frequent and extensive in large animals, thus ensuring that large animals can attach safely, while small animals can still detach their pads effortlessly. Our results therefore help to explain how nature’s climbers maintain a dynamic attachment performance across seven orders of magnitude in body weight.

scholarly journals Sliding-induced adhesion of stiff polymer microfibre arrays. II. Microscale behaviour

2008 ◽  
Vol 5 (25) ◽  
pp. 845-853 ◽  
Author(s):  
Bryan Schubert ◽  
Jongho Lee ◽  
Carmel Majidi ◽  
Ronald S Fearing
Keyword(s):  
Shear Force ◽  
Strong Dependence ◽  
Adhesive Force ◽  
Shear Forces ◽  
Spherical Probe ◽  
Adhesive Pads ◽  
Normal Adhesion ◽  
Fibre Angle ◽  
First Time ◽  
Adhesion Effect

The adhesive pads of geckos provide control of normal adhesive force by controlling the applied shear force. This frictional adhesion effect is one of the key principles used for rapid detachment in animals running up vertical surfaces. We developed polypropylene microfibre arrays composed of vertical, 0.3 μm radius fibres with elastic modulus of 1 GPa which show this effect for the first time using a stiff polymer. In the absence of shear forces, these fibres show minimal normal adhesion. However, sliding parallel to the substrate with a spherical probe produces a frictional adhesion effect which is not seen in the flat control. A cantilever model for the fibres and the spherical probe indicates a strong dependence on the initial fibre angle. A novel feature of the microfibre arrays is that adhesion improves with use. Repeated shearing of fibres temporarily increases maximum shear and pull-off forces.

scholarly journals Biomechanics of shear-sensitive adhesion in climbing animals: peeling, pre-tension and sliding-induced changes in interface strength

2016 ◽  
Vol 13 (122) ◽  
pp. 20160373 ◽  
Author(s):  
David Labonte ◽  
Walter Federle
Keyword(s):  
Fluid Layer ◽  
Stick Insect ◽  
Linear Increase ◽  
Shear Forces ◽  
Conflicting Demands ◽  
Adhesive Pads ◽  
Direction Dependence ◽  
Peel Force ◽  
Induced Changes ◽  
Adhesive Forces

Many arthropods and small vertebrates use adhesive pads for climbing. These biological adhesives have to meet conflicting demands: attachment must be strong and reliable, yet detachment should be fast and effortless. Climbing animals can rapidly and reversibly control their pads' adhesive strength by shear forces, but the mechanisms underlying this coupling have remained unclear. Here, we show that adhesive forces of stick insect pads closely followed the predictions from tape peeling models when shear forces were small, but strongly exceeded them when shear forces were large, resulting in an approximately linear increase of adhesion with friction. Adhesion sharply increased at peel angles less than ca 30°, allowing a rapid switch between attachment and detachment. The departure from classic peeling theory coincided with the appearance of pad sliding, which dramatically increased the peel force via a combination of two mechanisms. First, partial sliding pre-stretched the pads, so that they were effectively stiffer upon detachment and peeled increasingly like inextensible tape. Second, pad sliding reduces the thickness of the fluid layer in the contact zone, thereby increasing the stress levels required for peeling. In combination, these effects can explain the coupling between adhesion and friction that is fundamental to adhesion control across all climbing animals. Our results highlight that control of adhesion is not solely achieved by direction-dependence and morphological anisotropy, suggesting promising new routes for the development of controllable bio-inspired adhesives.

scholarly journals Shear-sensitive adhesion enables size-independent adhesive performance in stick insects

2019 ◽  
Author(s):  
David Labonte ◽  
Marie-Yon Struecker ◽  
Aleksandra Birn-Jeffery ◽  
Walter Federle
Keyword(s):  
Body Weight ◽  
Adhesive Force ◽  
Whole Body ◽  
Small Animals ◽  
Shear Forces ◽  
Stick Insects ◽  
Adhesive Pads ◽  
The Difference ◽  
Large Animals ◽  
Adhesive Performance

The ability to climb with adhesive pads conveys significant advantages, and is hence widespread in the animal kingdom. The physics of adhesion predict that attachment is more challenging for large animals, whereas detachment is harder for small animals, due to the difference in surface-to-volume ratios. Here, we use stick insects to show that this problem is solved at both ends of the scale by linking adhesion to the applied shear force. Adhesive forces of individual insect pads, measured with perpendicular pull-offs, increased approximately in proportion to a linear pad dimension across instars. In sharp contrast, whole-body force measurements suggested area-scaling of adhesion. This discrepancy is explained by the presence of shear forces during whole-body measurements, as confirmed in experiments with pads sheared prior to detachment. When we applied shear forces proportional to either pad area or body weight, pad adhesion also scaled approximately with area or mass, respectively, providing a mechanism that can compensate for the size-related loss of adhesive performance predicted by isometry. We demonstrate that the adhesion-enhancing effect of shear forces is linked to pad sliding, which increased the maximum adhesive force per area sustainable by the pads. As shear forces in natural conditions are expected to scale with mass, sliding is more frequent and extensive in large animals, thus ensuring that large animals can attach safely, while small animals can still detach their pads effortlessly. Our results therefore help to explain how nature’s climbers maintain a dynamic attachment performance across seven orders of magnitude in body weight.

The Effect of Ball Pad Metallurgy and Ball Composition on Solder Ball Integrity of Plastic Ball Grid Array Packages

1998 ◽  
Author(s):  
C.H. Zhong ◽  
Sung Yi
Keyword(s):  
Failure Mode ◽  
Barrier Layer ◽  
Shear Force ◽  
Solder Ball ◽  
Ball Grid Array ◽  
Reliability Test ◽  
Shear Forces ◽  
Ball Shear ◽  
Plastic Ball ◽  
Plastic Ball Grid Array

Abstract Ball shear forces of plastic ball grid array (PBGA) packages are found to decrease after reliability test. Packages with different ball pad metallurgy form different intermetallic compounds (IMC) thus ball shear forces and failure modes are different. The characteristic and dynamic process of IMC formed are decided by ball pad metallurgy which includes Ni barrier layer and Au layer thickness. Solder ball composition also affects IMC formation dynamic process. There is basically no difference in ball shear force and failure mode for packages with different under ball pad metallurgy before reliability test. However shear force decreased and failure mode changed after reliability test, especially when packages exposed to high temperature. Major difference in ball shear force and failure mode was found for ball pad metallurgy of Ni barrier layer including Ni-P, pure Ni and Ni-Co. Solder ball composition was found to affect the IMC formation rate.

New Systems for the Digestion of Solid Wastes

1992 ◽  
Vol 25 (7) ◽  
pp. 319-326 ◽  
Author(s):  
A. Wellinger ◽  
U. Baserga ◽  
K. Egger
Keyword(s):  
Dry Matter ◽  
Gas Production ◽  
Matter Content ◽  
Solid Wastes ◽  
Dry Matter Content ◽  
Feeding System ◽  
Shear Forces ◽  
Tank Reactor ◽  
Strong Shear ◽  
First Results

Two new systems for the digestion of solid wastes at thermophilic temperatures were developped and are currently being investigated at our research institute. The first system (ANCOM) was designed to process straw-rich cattle manure with a natural dry matter content of 18% to 22%. First results demonstrated a good specific gas production of 1.2 m3 biogas per m3 digester volume and day (54% methane) corresponding to a gas yield of 400 l per kg VS. A second digester system was developed to treat fruit, garden and vegetable (FGV-) waste. Because FGV-waste tends to float, a stirred tank reactor was designed in cooperation with an engineering firm. The reactor includes a distinguished new stirring system taking up strong shear forces and a hydraulic feeding system which guarantees that even during recirculation of the material, the hygenized digested substrate leaving the digester is not brought in contact with the fresh incoming material. First results measured at an HRT of 40 days demonstrated a specific gas production of 2.7 m3 per m3 fermenter and day.

Shear Forces between Tethered Polymer Chains as a Function of Compression, Sliding Velocity, and Solvent Quality

2003 ◽  
Vol 36 (2) ◽  
pp. 389-398 ◽  
Author(s):  
Phillip A. Schorr ◽  
Thomas C. B. Kwan ◽  
S. Michael Kilbey ◽  
Eric S. G. Shaqfeh ◽  
Matthew Tirrell
Keyword(s):  
Polymer Chains ◽  
Sliding Velocity ◽  
Shear Forces ◽  
Solvent Quality ◽  
Tethered Polymer Chains

Large Deflection of a Rectangular Plate Resting on a Pasternak-Type Elastic Foundation

1977 ◽  
Vol 44 (3) ◽  
pp. 509-511 ◽  
Author(s):  
P. K. Ghosh
Keyword(s):  
Rectangular Plate ◽  
Elastic Foundation ◽  
Large Deflection ◽  
Lateral Load ◽  
Bending Moments ◽  
Shear Forces ◽  
Simply Supported ◽  
Base Parameters ◽  
Square Plate

The problem of large deflection of a rectangular plate resting on a Pasternak-type foundation and subjected to a uniform lateral load has been investigated by utilizing the linearized equation of plates due to H. M. Berger. The solutions derived and based on the effect of the two base parameters have been carried to practical conclusions by presenting graphs for bending moments and shear forces for a square plate with all edges simply supported.

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