International audienceThis study presents film thickness and friction measurements of the refrigerant R1233zd (E-1-chloro-3,3,3,trifluoropropene-1) in a tribological contact. For the film thickness, optical interferometry technique with glass–steel contact is used in a ball-disc configuration, whilst for the traction measurements (Stribeck and traction curves), a contact ceramic ball–steel disc is used. In both cases, the Wedeven Associates Machines-5 tribometer is employed. An attempt to model the film thickness results is also carried out. The model gives a reasonably good prediction with respect to the experiments

A general elastohydrodynamic lubrication model was developed to consider the nonsphericity of the bearing geometry in hip joint implants, both under the steady and transient conditions. The articulation between the femoral head and the acetabular cup was represented by a nominal ball-in-socket configuration. The nonsphericity was introduced on the acetabular cup and femoral head bearing surfaces in the form of an ellipsoidal surface represented by variations of the radii of curvature given by the three semi-axis lengths of the ellipsoid with regard to a nominal spherical surface. An appropriate spherical coordinate system and solution domain discretization were used to facilitate the numerical simulations. Both the equivalent discrete spherical convolution model and the corresponding spherical fast Fourier transform technique were used to evaluate the elastic deformation of either the spherical or nonspherical bearing surfaces. A fixed-tracked method was also developed to simulate the complex morphology introduced by moving the interface of the nonspherical bearing surfaces. The general methodology for the nonspherical bearing was first applied to investigate the steady-state elastohydrodynamic lubrication of an ellipsoidal cup articulating against a spherical head in a typical metal-on-metal hip joint implant. Subsequently, the problem of an ellipsoidal head articulating against a spherical cup was considered under the transient conditions. The significance of nonsphericity of bearing geometry in hip joint implants due to manufacturing, designing, and wear was discussed. The results obtained showed that the effect of a nonspherical bearing surface geometry on elastohydrodynamic lubrication was dependent on the orientation, the magnitude, and the deviation direction of the nonsphericity. A well-controlled nonsphericity was seen to be beneficial for improving the lubrication.

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This work investigates the transient effects of a single subsurface inclusion over the pressure, film thickness, and von Mises stress in a line elastohydrodynamic lubrication contact. Results are obtained with a fully-coupled finite element model for either a stiff or a soft inclusion moving at the speed of the surface. Two cases analyzed consider the inclusion moving either at the same speed as the mean velocity of the lubricant or moving slower. Two additional cases investigate reducing either the size of the inclusion or its stiffness differential with respect to the matrix. It is shown that the well-known two-wave elastohydrodynamic lubrication mechanism induced by surface features is also applicable to the inclusions. Also, that the effects of the inclusion become weaker both when its size is reduced and when its stiffness approaches that of the matrix. A direct comparison with predictions by the semi-analytical model of Morales-Espejel et al. ( Proc IMechE, Part J: J Engineering Tribology 2017; 231) shows reasonable qualitative agreement. Quantitatively some differences are observed which, after accounting for the semi-analytical model's simplicity, physical agreement, and computational efficiency, may then be considered as reasonable for engineering applications.

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