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.

A novel test rig for in situ and real time optical measurement of the contact area evolution during pre-sliding of a spherical contact

Abstract: An experimental test rig was developed in order to investigate elastic–plastic single micro-spherical contact under combined normal and tangential loading. This novel apparatus allows in situ and real time direct optical measurement of the real contact area (RCA) evolution in pre-sliding. It also allows relative displacement measurements under very low rates of tangential loading (down to 0.01 N/s) to capture accurately the fine details at sliding inception. This is achieved by piezoelectric actuation in closed loop feedback control in addition to synchronization with data and image acquisition to obtain real time measurement. The RCA measurement is realized by direct optical observation technique, whereas two different image processing algorithms were implemented for the elastic and the elastic–plastic contact regimes. The various features and capabilities of the test rig are presented along with some preliminary experimental results of RCA and friction behavior to assess its performance.

Effect of microseparation on contact mechanics in ceramic-on-ceramic hip joint replacements.

Abstract: The contact mechanics in ceramic-on-ceramic hip implants are investigated in this study under the microseparation condition where the edge contact occurs between the superolateral rim of the acetabular cup and the femoral head. A three-dimensional finite element model is developed to examine the effect of the microseparation distance between the femoral head and the acetabular cup on the contact area and contact stresses between the bearing surfaces. It is shown that microseparation leads to edge contact and elevated contact stresses, and these are mainly dependent on the magnitude of separation, the radial clearance between the femoral head and the acetabular cup, and the cup inclination angle. For a small microseparation distance (less than the diametrical clearance), the contact occurs within the acetabular cup, and consequently an excellent agreement of the predicted contact pressure distribution is obtained between the present three-dimensional anatomical model and a simple two-dimensional ax...

Fracture Mechanics and Adherence of Viscoelastic Solids

Abstract: Contact of two elastic solids is treated as a thermodynamic problem. It is shown that U = UE+US and UE = US+UP+US are thermo-dynamic potentials respectively for transformations at fixed grips and at fixed load conditions (UE, UP, US are the elastic, potential, interface energies). Equations giving the displacement δ and the strain energy release rate G as a function of the contact area A and the load P appear to be the equations of state of the system. Two bodies in contact on an area A are in equilibrium if G=w, where w is the thermodynamic (or Dupre’s) work of adhesion. This equilibrium is stable if ∂G/∂A is positive, unstable if negative. The quasistatic force of adherence is the load corresponding to ∂G/∂A = o. But equilibrium may be stable at fixed grips and unstable at fixed load, so that the quasistatic force of adherence may depend on the stiffness of the measuring apparatus. When G>w, the separation of the two bodies starts, and can be seen as the propagation of a crack in mode I. G-w is the force applied to unit length of crack; under this force, the crack takes a limiting speed v, which is a function of the temperature, and one can write $$G - w = w\phi \left( {{a_T}v} \right).$$

Effects of a carbon nanotube layer on electrical contact resistance between copper substrates

Abstract: Reduction of contact resistance is demonstrated at Cu–Cu interfaces using a multiwalled carbon nanotube (MWCNT) layer as an electrically conductive interfacial material. The MWCNTs are grown on a copper substrate using plasma enhanced chemical vapour deposition (PECVD) with nickel as the catalyst material, and methane and hydrogen as feed gases. The MWCNTs showed random growth directions and had a bamboo-like structure. Contact resistance and reaction force were measured for a bare Cu–Cu interface and a Cu–MWCNT–Cu interface as a function of probe position. For an apparent contact area of 0.31 mm 2 ,a n80% reduction in contact resistance was observed when the MWCNT layer was used. Resistance decreased with increasing contact force, thereby making it possible to use this arrangement as a small-scale force sensor. Also, the Cu–MWCNT–Cu interface was roughly two times stiffer than the bare Cu–Cu interface. Contact area enlargement and van der Waals interactions are identified as important contributors to the contact resistance reduction and stiffness increase. A model based on compaction of the MWCNT layer is presented and found to be capable of predicting resistance change over the range of measured force. (Some figures in this article are in colour only in the electronic version)