Effect of surface roughness combination on frictional sound

摘要

Whenever two bodies slide against each other in dry contact, they start to vibrate and radiate sound. It is believed that the main cause for such small-scale vibration and sound is the surface roughness. Despite this common recognition, there are only a small number of past experimental studies focused on the effect of surface roughness on friction induced sound. Takahashi [1] studied frictional noise under heavy load, generated by the contact of the rim of a rotating cylinder against a plate specimen (R{sub}(max)<0.5μm). For two different cylinders with R{sub}(max) roughness of 0.2 and 3 pm, sliding against the plate in the presence of spindle oil, he observed that the change in the sound pressure level (SPL) is proportional to 2Olog{sub}10(R{sub}(max2)/ R{sub}(max1)) Later Yokoi and Nakai conducted experiments on a spherical tip pin-on-rim apparatus in dry contact. They used three different disks with roughness R{sub}(max) = 5, 3 and 0.5 μm (pin roughness not specified), and modified Takahashi's relationship, so that the difference in SPL was equal to 20log{sub}10(R{sub}(max2)/ R{sub}(max1)){sup}0.8. In a later study Othman et al. investigated the frictional noise generated when a sharp stylus traversed the rough surface of a flat disk at high speed (1.05 m/s). They used disks made of brass, aluminium and steel with average surface roughness R{sub}a in the range of 1.5 to 20 μm, and found that SPL and surface roughness are related by the expression: R{sub}a = C(SPL){sup}h, where C and b is an experimental parameters, b depending on the material. In essence, Takahashi proposed a linear relationship between sound pressure and surface roughness for lubricated hertzian line contact. Yokoi and Nakai modified it for dry hertzian point contact to a power law with power (of 0.8 - still very close to linear relationship. The formula proposed by Othman et al. for dry point contact at high speed describes a base 10 exponential dependence of sound pressure on the surface roughness.