BUAFULL

Acoustics of friction under light loads

 Partecipanti

Mappa

 Word cloud

Esplora la "nuvola delle parole (Word Cloud) per avere un'idea di massima del progetto.

 Obiettivo del progetto (Objective)

'Understanding the properties and consequences of friction under light normal loads is fundamental to areas such as tactile sensing, haptic systems used in robotic gripping of sensitive objects, and characterization of products rangıng from the softness of fabrics to effects of lotions on skin. In tactile sensing, as a finger is lightly rubbed over a surface, the mechanoreceptors in the dermis become excited and send signals to the brain for processing. Their excitation results from the asperities, adhesion, and other geometric and chemical surface properties that come into contact with the skin. These same sources also give rise to vibration and sound as two surfaces are in sliding friction even under light load, such as a finger pad over a silk fabric. Whereas the mechanoreceptors respond around 200 - 300 Hertz, spectrum of the actual sounds and vibrations that are generated can go beyond these values, thus presenting additional opportunities for surface characterisation through the acoustics response. Only a limited number of those address friction sounds and vibrations under light loads. Studies that address soft materials have not yet been reported. Much of the previous work in this area relates to perception and tactile sensing with limited attention to the generation mechanisms of sound and vibration between soft surfaces. The proposed project builds on the principle investigator's experience in this area for the past two decades. The project will focus on modeling friction forces over an area the size of a finger pad that moves over a surface and develop predictive models of the sound and vibration that emanate from such a moving contact area. The novelty the project brings includes consideration of materials and also adhesive surfaces, which are important in gripping. Another outcome of this project will be a new test set up that can mimic a finger rubbing over a material under light friction and has the ability simultaneously measure dynamic quantities.'

Introduzione (Teaser)

EU-funded scientists developed a novel system akin to a human finger touching silk in a bid to measure sound, vibration and friction between soft materials.

Descrizione progetto (Article)

Vibration and sound generation between two surfaces that are smoothly sliding against each other stem from different surface properties. Although surface characterisation through acoustic responses has been largely addressed in tactile sensing, friction-induced vibrations and sounds between soft surfaces have hitherto received little attention.

Scientists initiated the EU-funded project 'Acoustics of friction under light loads' (http://me.bilkent.edu.tr/?page_id=912&nvaf_id=11&lang=en (BUAFULL)) to further advance studies in this field. BUAFULL related the tribological characteristics of the rubbing surfaces (mainly roughness, adhesion and geometry) to the acoustic response under light loads. Its ultimate aim was to emulate friction finger lightly rubbing a soft material.

To this end, scientists developed a lightweight pendulum that acts like a finger, where a rotating beam slides on the surface area under the finger to provide the touch. A lift mechanism in the pendulum controlled the contact force.

Studies showed that the pendulum lifted the surface by an amount proportional to the friction developed between them. The pendulum motion was found to be constrained, also involving discontinuous contacts. In addition, friction-induced non-linear responses such as wedge locking, jam and swerve could have an impact on the expected pendulum dynamics.

Correlating the pendulum dynamic response to the friction provided important new insight into friction measurements between soft surfaces under light loads. Another significant finding was that the measurement set-up was able to separate the adhesive friction component. Dynamic modelling of a constrained pendulum described such relationships and also provided design guidelines to avoid wedge locking of the pendulum tip with the surface.

Project developments are fundamental to further advancing a number of areas. These include tactile sensing, haptic systems used in robotic gripping of sensitive objects, and product characterisation ranging from fabric softness to surfactant effects on skin.