25,468 research outputs found
Voltage-Induced Friction with Application to Electrovibration
Due to the growing interest in robotic and haptic applications, voltage-induced friction has rapidly gained in importance in recent years. However, despite extensive experimental investigations, the underlying principles are still not sufficiently understood, which complicates reliable modeling. We present a macroscopic model for solving electroadhesive frictional contacts which exploits the close analogy to classical adhesion theories, like Johnson-Kendall-Roberts (JKR) and Maugis, valid for electrically neutral bodies. For this purpose, we recalculate the adhesion force per unit area and the relative surface energy from electrostatics. Under the assumption of Coulomb friction in the contact interface, a closed form equation for the friction force is derived. As an application, we consider the frictional contact between the fingertip and touchscreen under electrovibration in more detail. The results obtained with the new model agree well with available experimental data of the recent literature. The strengths and limitations of the model are clearly discussed.TU Berlin, Open-Access-Mittel – 201
Porous LSCF/Dense 3YSZ Interface Fracture Toughness Measured by Single Cantilever Beam Wedge Test
Sandwich specimens were prepared by firing a thin inter-layer of porous
La0.6Sr0.4Co0.2Fe0.8O3-d (LSCF) to bond a thin tetragonal yttria-stabilised
zirconia (YSZ) beam to a thick YSZ substrate. Fracture of the joint was
evaluated by introducing a wedge between the two YSZ adherands so that the
stored energy in the thin YSZ cantilever beam drives a stable crack in the
adhesive bond and allows the critical energy release rate for crack extension
(fracture toughness) to be measured. The crack path in most specimens showed a
mixture of adhesive failure (at the YSZ-LSCF interface) and cohesive failure
(within the LSCF). It was found that the extent of adhesive fracture increased
with firing temperature and decreased with LSCF layer thickness. The adhesive
failures were mainly at the interface between the LSCF and the thin YSZ beam
and FEM modelling revealed that this is due to asymmetric stresses in the LSCF.
Within the firing temperature range of 1000-1150C, the bonding fracture
toughness appears to have a strong dependence on firing temperature. However,
the intrinsic adhesive fracture toughness of the LSCF/YSZ interface was
estimated to be 11 Jm2 and was not firing temperature dependent within the
temperature range investigated.Comment: 13 figures, 1 table, journal paper publishe
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