Deformation Measurements of Randomly Rough Surfaces

Measurements of surface deformations as part of the "Contact Mechanics Challenge'' were collected using digital image correlation (DIC). For these experiments, a scaled version (10009) of the periodic and random roughness surface provided for the "Contact Mechanics Challenge'' was used. A 100 mm 9 100 mm scale replica of the surface, approximately 10 mm thick, was 3D-printed using an opaque polymethylmethacrylate and pressed into contact against flat, transparent polydimethylsiloxane (PDMS) sheets with dead weight loads. Four different formulations of PDMS were used, and the resulting elastic moduli ranged from 64 kPa to 2.1 MPa. The DIC technique was used in situ to measure the deformation of the PDMS surface at each load increment from 22.5 to 450 N. Surface deformations in and out of contact were measured across the entire apparent area of contact and overlaid with the measurements of contact area to provide a complete description of the surface profile during loading. A direct comparison between these experiments and the simulations regarding the gap within the contact at a reduced pressure of 0.164 agrees to within +/- 10% when normalized to the maximum gap.