PSI - Issue 36

Iakov Lyashenko et al. / Procedia Structural Integrity 36 (2022) 24–29 Iakov Lyashenko, Vadym Borysiuk / Structural Integrity Procedia 00 (2021) 000 – 000

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2. Experimental device and methodology Photo of the laboratory equipment that was used for studying of the adhesive contact is shown in the left panel of Fig. 1. Motorized linear stages M-403.2DG (manufactured by PI) are denoted by 1 and 2 and operated by two controllers PI C-863 that are shown as 6 and 7 in the figure. These stages can perform the displacement of the indenter for distance up to 50 c m, with increment 0.2 µm. During the movement the indenter can be loaded up to 50 N. Specified magnitudes of load and displacement are more than enough to provide needed range of the parameters required in our experiments on adhesive contact. Three axes force sensor ME K3D40 that operates in the range ±10 N are denoted by 3 in the figure. Obtained signals are amplified by 4-channel strain-gauge amplifier GSV-1A4 SubD37/2 connected to personal computer through 16-bit multifunction input/output device NI USB 6211. Steel indenter mounted on the force sensor is indented into the elastomer (hardened solution of the gelatin) denoted by 4 in the photo. Surface of the elastomer can be fixed at different angles in two directions by tilt mechanism 5. Evolution of the contact area is observed through the video camera 8 (in the figure camera is covered by metal plate and is not visible). All fixator in the laboratory setup are made of aluminum. Materials for indenter and elastomer are selected according to the experimental task. As the figure shows, developed facility can produce independent movement in both normal and tangential directions and complex investigation of the adhesive contact can be performed. Developed apparatus was used in our previous studies of the adhesive contact where various factors, such as surface roughness, impurities, indenter velocity, chemical inhomogeneity of the surface, tangential shift of the indenter etc. were taken into account (Lyashenko, Li and Popov, 2021; Popov et al., 2021). Main difference from the cited works is the hardened water solution of gelatin (denoted as 4 in the Fig. 1) that is used in the proposed study as the high-adhesive material similarly to the (Popov, Pohrt and Li, 2017). Jelly mass was obtained from the hardening of regular culinary gelatin (produced by “Dr. Oeteker” trade mark ). The solution was prepared by dilution of 4 packs of gelatin, with the mass 9 g each in one liter of water (this amount is approximately twice higher than in standard cooking recipes). The jelly, obtained from such solution preserves its solid hard state at room temperature (around 24 degrees Celsius). Jelly was poured into a rectangular container made of Plexiglas, with dimensions 15x15x4 cm 3 (last linear dimension is a layer thickness, at this dimensions the volume of the sample was 900 ml). After the solidification of the jelly, it was brought into contact with the steel indenter, the surface of which has been polished to a mirror. After the contact indenter was displaced in the normal and tangential directions. During the movement, all three components of the force in contact was measured, and the contact area was photographed every 1 s.

Fig. 1. (left panel) general view of the equipment; (right panel) photo of the contact area between indenter and gelatin surface, where arrow shows the crack that appeared at beginning of motion.