Johnson , Kendall And Roberts Research Articles

Nonlinear Elastic Analysis of the Adhesive Strength between Rubber-Like Materials and Rigid Surfaces

Abstract A nonlinear elastic finite element analysis of the adhesive strength between rubber-like materials and rigid surfaces has been conducted based on fracture mechanics principles. The finite element model is an elastomer half sphere adhering to a rigid flat surface. An analytical solution for the system was first developed by Johnson, Kendall and Roberts (JKR) in 1971, which agrees well with experimental data for small contact area. The objective of this paper is to elucidate the relationship between the adhesive fracture energy, tensile loads and debonding process of the system when the contact area is large. A general analysis procedure for nonconforming adhesion-contact problem has been established in this study, which allows us to determine the adhesive fracture energy from measurements of the final pull-off force Pc or the zero-load contact radius α0. Our results agree well with JKR's prediction when the zero-load contact radius is less than 25% of the radius of the sphere. However, as the contact radius increases, the debonding process deviates from JKR's prediction.

Physical adhesion of rubber to glass: cross-link density effects near equilibrium

Pre-cross-linked rubber adheres to glass mainly by physical interactions (van der Waals' bonds). Nevertheless, the measured adhesion is often greater than expected even at low separation rates. By adopting the Johnson, Kendall and Roberts (JKR) technique for assessing adhesion between a rubber hemisphere and a glass slide, it is shown that the apparently stable equilibrium state depends on the manner in which initial contact is obtained. Although the work of adhesion due to osculating contact is close to the Dupré value, that obtained following the application of direct pressure to the system increases with the average inter-cross-link molecular weight, M c , of the elastomer. The kinetics of evolution towards equilibrium are considered using a simple dynamic energy balance argument.