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Comprehensive friction performance of products and related factors of noise produced by products:


1. A good friction coefficient of friction products are […]

1. A good friction coefficient of friction products are not as high as possible, for car brake pads, according to the author for many years production experience, the friction coefficient of products below 0.4 as well, the best range should be between =0.35~0.38, rarely semi metallic disc brake noise of general products within this range when using when the possibility of noise, friction coefficient of product is higher than 0.4 to 1-2 times. Generally speaking, whether the coefficient of friction of the product is stable and whether the braking process is stable is closely related to whether or not there is a big noise. Specifically: the product contact pressure increase in the use of the process, the transient temperature rise suddenly appears on the contact surface of locally convex starting point "stick" and "separation" caused by the friction characteristics change, pressure, wear, dual position change, vibration noise. Therefore, the stability of the instantaneous friction coefficient and the constant of the driving torque are prerequisites to ensure that the brake noise is not generated. This requires that the friction coefficient of the braking product is comparable to the speed, and the temperature and pressure comparability should be stable. In the braking process, the instantaneous friction coefficient changes as little as possible.
The dynamic friction coefficient, the static / dynamic friction coefficient, is the best, and the instantaneous minimum / instantaneous instantaneous maximum is close to 1. This kind of brake product is usually installed on the car and seldom generates noise.
2. The overall hardness of the product can not be too large. Among them, the product itself, resin content, surface treatment, the number of friction agents, the amount of feed (density) are related to hardness, the proper adjustment of these ratio, optimize its structure will be satisfactory results. What should be pointed out here is: we advocate products with moderate hardness. We can not say that the overall resilience, the lower the hardness better, for example: the content of rubber itself is perfectly elastic hardness is low, but the actual braking noise and often large, as before this says, the elastic is too large, the torque transmission is not smooth jitter, will cause greater anti noise, but the resin rubber modified to reduce the brake noise product is effective, which is not hard and brittle carbide film.
3. The super refining agent will minimize the noise, friction products are often added to its inherent greater friction coefficient of materials, such as: Feldspar powder, chromium ore powder, white corundum, three, two aluminum oxide and other substances. These high Mohs hardness of the material itself (more than 5-8) of these materials are often used as friction increasing agent is added to the product, but the practice proved that the friction increasing agent ultrafining is crucial in preventing noise factors produced products. For example: 200 the purpose of equal amount of WIP in the friction increasing agent will produce noise, use 325 mesh would have no noise, if the friction increasing agent the same ultrafining to the above 1500 items, plus 3% percentage points more than the amount without brake noise. This is to explain the super refinement of friction agent, more practical significance.
4. Products with long heat curing time are easy to produce noise than products with short curing time. This is mainly because the curing time is long, the structure changes, and the overall hardness increases.
5.The amount of feed will also cause noise in different sizes, which may be related to the density and inherent frequency of the product itself.
6. The quality of steel fiber will also affect the braking noise, the general high carbon content of steel fiber or heat treatment temperature of steel fiber will cause brake noise. Therefore in our choice of fibers, fillers and decrease friction modifier should be chosen as the inherent low hardness or moderate use of materials, such as: good heat resistance and high strength aramid (KEVLAR) itself not only wear and no damage to the dual, adding a small amount of aramid fiber can reduce the brake noise, but ceramic although fiber high temperature stable friction coefficient, but the hardness of ceramic fiber is higher (more than 6) are often used in ceramic fiber will occur in increasing the noise rate. In order to reduce the probability of noise, we often advocate using those materials with lower or lower Mohs hardness to reinforce and fill the material. For example: barium sulfate, diatomaceous earth, ice powder, copper powder, aluminum powder, Hui powder, iron powder, graphite, mica, vermiculite powder and rubber, NBR powder, to the overall hardness of products is not high, to reduce the brake noise (see noise reduction formula structure reference table)

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