Investigation Of The Friction And Vibration Properties Of Finger Friction At Different Directions

Finger touch is one of the most important ways for human to know the environment.Human can perceive the object surface texture,material,temperature and humidity,etc.though the finger touch it along different directions.The behavior of human touch and grasp can be seen in everywhere such as using the keyboard,mouse,kitchen ware and opening the bottle cap,packing,engaging in sports,driving,etc.In recent year,finger friction has been wildly researched.However,it makes the difficult to test and simulate finger friction due to the specific physiological structure,complex mechanical properties and many factors which affect the process.The property of finger friction has not been recognized deeply up to now.Therefore,designing a new experimental device to improve the stability and repeatability of finger friction test is great significance to deeply understand the mechanism of finger friction.And it also provides more experimental basis for the design of the surface of the product.In this research,in order to overcome the problem that the normal force and contact angle are difficult to control,a new experimental device of finger friction is designed.The new device can improve the reliability of finger friction test.Thus,the influence of various factors on tribological behavior of finger friction can be investigated more accurately.In those tests,the aluminum alloy samples were selected as the pair of friction.And the texture of sample surface was processed by the sandpaper.The frictional force,normal force,friction coefficient and vibration were investigated for finger sliding on different directions by changing the normal force,contact angle and sliding velocity.The main conclusions are as follows:1?The new experimental device has the advantages of simple structure and convenient processing.The finger bracket and the loading device can control the normal force and contact angle,etc.In the test of finger friction,the curve of normal and friction force fluctuate in a small range.Therefore,the stability and reliability of finger friction test can be improved.2?The friction coefficient decreases with the increasing sample roughness and normal force when the finger slides at different relative direction.However,friction coefficient first decreases and then increases with the contact angle increasing due to the contact area changing from finger pulp to the fingertip with increasing the contact angle.3?The distance between the fingerprints increases when the fingerprints are dragged at a certain sliding direction,leading to an fully engage between fingerprint and sample,thereby improving the contact area.Therefore,the friction coefficient increases.On the contrary,the fingerpr:ints will be stacked along the sliding direction that makes the skin of fingertip becoming smooth when the fingerprints are squeezed.Thus,the result will be opposite to the previous inference when the contact area decreases.The deformation of fingerprints on the finger pulp is opposite to the deformation on the fingertip at the same sliding direction.4?The friction between finger and sample amount to the slide of two texture due to the fingerprints existing on the finger skin.The frequency of finger vibration is mainly determined by the densely texture.The frequency increases with the sample roughness decreasing in different sliding directions.The fingerprints become dense when it was squeezed otherwise it will become sparse.The frequency of vibration is larger when the fingerprint is densely than the fingerprint is sparse at the same test parameters.