Contact area

About: Contact area is a research topic. Over the lifetime, 12358 publications have been published within this topic receiving 256401 citations. The topic is also known as: contact patch & contact region.

Effect of capillary condensation on friction force and adhesion.

Abstract: Friction force measurements have been conducted with a colloid probe on mica and silica (both hydrophilic and hydrophobized) after long (24 h) exposure to high-humidity air. Adhesion and friction measurements have also been performed on cellulose substrates. The long exposure to high humidity led to a large hysteresis between loading and unloading in the friction measurements with separation occurring at large negative applied loads. The large hysteresis in the friction-load relationship is attributed to a contact area hysteresis of the capillary condensate which built up during loading and did not evaporate during the unloading regime. The magnitude of the friction force varied dramatically between substrates and was lowest on the mica substrate and highest on the hydrophilic silica substrate, with the hydrophobized silica and cellulose being intermediate. The adhesion due to capillary forces on cellulose was small compared to that on the other substrates, due to the greater roughness of these surfaces.

Real‐time Rigid Body Simulation for Haptic Interactions Based on Contact Volume of Polygonal Objects

Abstract: This paper proposes a new method for real-time rigid body simulations for haptic interactions based on a penalty method regarding contact volume. Analytical methods for calculation of contact forces require too much time to maintain fast update rates for haptic controls. In addition, they prohibit direct connection of haptic interfaces. Penalty methods, which employ spring-damper models for calculation of contact forces, offer a very rapid rate of iterations. In addition, they permit direct connection of haptic interfaces. Penalty methods are good for haptic interactions. However, previous penalty methods do not regard distribution of contact forces over the contact area. For that reason, they can’t calculate normal and friction forces on face-face contacts correctly. We propose a distributed spring-damper model on a contact area to solve these problems. We analyze threedimensional geometries of the intersecting portion on the polyhedral objects. Then, we integrate forces and torques of distributed spring-damper models. We implement a proposed simulator and compare it with a point-based penalty method and constraint method. The comparison shows that the proposed simulator improves accuracy of the simulation of face-face contact and friction forces and the simulation speed. In addition, we attach a six degree-of-freedom (6-DOF) haptic interface to the simulator. Users can feel 6-DOF force feedback and input 6-DOF motions.

Experiments and viscoelastic analysis of peel test with patterned strips for applications to transfer printing

Abstract: Transfer printing is an exceptionally sophisticated approach to assembly and micro-/ nanofabrication that relies on a soft, elastomeric ‘stamp’ to transfer solid, micro-/ nanoscale materials or device components from one substrate to another, in a large-scale, parallel fashion. The most critical control parameter in transfer printing is the strength of adhesion between the stamp and materials/devices. Conventional peel tests provide effective and robust means for determining the interfacial adhesion strength, or equivalently the energy release rate, and its dependence on peel speed. The results presented here provide analytic solutions for tests of this type, performed using viscoelastic strips with and without patterns of relief on their surfaces, and validated by systematic experiments. For a flat strip, a simple method enables determination of the energy release rate as a function of the peel speed. Patterned strips can be designed to achieve desired interfacial properties, with either stronger or weaker adhesion than that for a flat strip. The pattern spacing influences the energy release rate, to give values that initially decrease to levels smaller than those for a corresponding flat strip, as the pattern spacing increases. Once the spacing reaches a critical value, the relief self-collapses onto the substrate, thereby significantly increasing the contact area and the strength of adhesion. Analytic solutions capture not only these behaviors, as confirmed by experiment, but also extend to strips with nearly any pattern geometry of cylindrical pillars.

Mode-mixity-dependent adhesive contact of a sphere on a plane surface

Abstract: Tangential loading in the presence of adhesion is highly relevant to biological locomotion, but mixed-mode contact of biological materials or similar soft elastomers remains to be well understood. To better capture the effects of dissipation in such contact problems owing to viscoelasticity or irreversible interfacial adhesive processes, a model is developed for the combined adhesive and tangential loading of a rigid sphere on a flat half-space which incorporates a phenomenological model of energy dissipation in the form of increased effective work of adhesion with increasing degree of mode mixity. To verify the model, contact experiments are performed on polydimethylsiloxane (PDMS) samples using a custom-built microtribometer. Measurements of contact area during mixed normal/tangential loading indicate that the strong dependence of the effective work of adhesion upon mode mixity can be captured effectively by the phenomenological model in the regime where the contact area stayed circular and the slip was negligible. Rate effects were seen to be described by a power-law dependence upon the crack front velocity, similar to observations of rate-dependent contact seen for pure normal loading.