Mechanical Models Study For Adhesive Contact With Effects Of Tangential Forces

Adhesive contact and friction exist in various aspects of industrial production and human's daily life with significant implications,say,e.g.,the adhesive failure in MEMS and the synthesis of biomimetic tapes.While adhesive contact under normal forces has been widely studied,the interplay between adhesion and tangential forces still remains an open question,which,indeed,is important in understanding the friction and tribology at microscopic and nanoscopic scales.In the beginning of sliding,on the basis of possible sliding and rolling on the tangential force,the following aspects have been studied at depth:A generalized double-Hertz(D-H)model has been established for cylinders in adhesive contact under forces with non-vanishing tangential components.In the model,due to the normal forces,the contacting interface is composed of an adhesive zone and a contact zone.The adhesive traction and the contacting pressure are respectively distributed along the two zones and both of them are similar to the Hertzian pressure except for the sign of the attractive adhesive traction.With the appearance of the tangential components,a new adhesive shear zone(similar to the sliding zone but not identical)and shear contacting zone(similar to the non-sliding zone)develop by generalizing the D-H model.To make it tractable,the adhesive shear traction is assumed to be proportional to the contacting pressure therein.Then the conventional shear traction can be obtained from the non-sliding the conditions.The tractions thus obtained involve no singularity.With the model,relationship between contact sizes and forces,and distributions of tractions have been discussed on the basis of numerical results.Qualitative comparison with experiments has been made.A generalized double-Hertz model for spheres in adhesive contact with substrates has also been developed.The treatments and assumptions are similar to those in the model for cylinders.With the model,numerical calculations have been conducted to demonstrated the adhesive contact behavior and the distribution of tractions.It has been indicated that the tangential components induce the shear-peeling effect.Quantitative comparison has been made with some available experiments.A rolling friction model has been developed for cylinders with account of adhesion.Herein,the contact between a cylinder and a substrate has been approximated by oblique contact.By considering the adhesion hysteresis that exists between the front edge and the trailing edge,the rolling friction model is established on the basis of balance between the energy release rate and the work of adhesion as adopted in the JKR model.Through numerical calculations,relationship between adhesion hysteresis and rolling friction,critical angle and moments has been discussed.