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1 Surface Properties
Due to pollution, chemical treatment, plating, and the role of a lubricant, the metal surface to form a thin surface film (such as oxide film, a sulfide film, a phosphate film, a chloride film, indium film, a film of cadmium, aluminum, etc. ), so that the surface and the substrate having different properties. If the surface film in a thickness, the real contact area is still spread on the substrate mask instead of a table, while allowing the surface film is less than the shear strength of the shear strength of the base material; other due to the presence of the surface film less prone to adhesion, friction and friction factor can therefore be reduced.
Surface film thickness on the friction factor has a great influence. If the surface film is too thin, the membrane occurs easily crush and direct contact with the base material; if the surface film is too thick, on the one hand due to the softer film leaving the actual contact area increases, the other two pairs of dual peaks in the surface of the micro- furrow membrane surface effects are more prominent. Visible, there is a surface film worth seeking optimum thickness.
(2) material properties
Metal friction coefficient of friction with matching materials vary. In general, the same metal or large metal intersolubility friction, prone to sticking, the friction factor is larger; Conversely, the friction factor is smaller. Different structural materials have different friction characteristics. Such as graphite layered structure because a stable, and the binding force between layers is small, easy sliding, the friction coefficient is small; Another example is the friction pairing of diamond because of high hardness, the actual contact area is small and not easy adhesion of the friction factor is also small.
3.Temperature
The ambient temperature effect on the friction factor, mainly due to the changing nature of the surface materials caused, Bowden et al tests showed that many metals (such as molybdenum, tungsten, titanium, etc.) and their compounds friction factor in the surrounding medium temperature of 700 ~ 800 ℃ when minimum. This phenomenon is due to the shear strength of the initial temperature drop and rise further sharp decline in the yield point of the actual contact area increases caused by many reasons. But polymer friction or pressure processing, the friction factor changes with temperature maxima will appear.
Seen from the above, the influence of temperature on the friction factor is variable, depending on the specific working conditions, material properties, the oxide film changes and other factors from the fallout of the relationship between temperature and friction factor becomes very complicated.
4 relative velocity
Generally, the sliding speed and temperature rise may cause the surface heat, thus changing the nature of the surface, so the friction coefficient will change with it.
The general state of contact friction plastic, and the sliding friction coefficient of the increase rate over a maximum value, as shown in curve 2 and 3, and the duality between the surface with the normal load increases, the maximum position Move to the coordinate origin. When the load is extremely small, only the rising portion of the curve;
When the dual surface friction relative sliding speed exceeds 50m / s, the contact surface of the large amount of frictional heat. Due to continuous contact with the contact point a short time, instantaneous time to produce a lot of frictional heat diffuses to the substrate, thus frictional heat concentration at the surface, so that the surface layer of high temperature and the melting occurs, the molten metal plays a liquid lubricant, the friction reduction factor increases with speed, such as copper in the sliding speed of 135m / s, its friction coefficient is 0.055; while 350m / s, then reduced to 0.035. However, some materials (such as graphite) is almost free from the sliding friction coefficient of velocity of, the reason is the mechanical properties of such materials in a wide temperature range remains unchanged.
For the boundary friction in speed is lower than 0.0035m / s, that is, from static friction to kinetic friction transition low speed range, as the speed increases, the friction factor adsorbed film tends to be gradually reduced value, reaction film friction factor tends to gradually increase value.
5 Load
Under normal circumstances, the metal friction coefficient friction decreases with increasing load, and then stabilized, this phenomenon can be explained by adhesion theory. When the load is small, the two surfaces are in elastic contact with the dual state, then the actual contact area of the load 2/3 power is proportional, while the adhesion theory, the real contact area is proportional to the friction force, the friction factor and thus the load 1 / 3 power ratio; when the load is large, the two surfaces are plastic dual-contact state, the actual contact area and the load 2/3 to 1 power proportional to the friction coefficient decreased with the load increases while the slower and stabilized; when large loads to two pairs of dual contact state in a plastic surface, the friction factor is almost independent of the load.
The size of the static coefficient of friction but also with two pairs of dual surface under load static contact continuation duration. In general, the longer the duration stationary contact, the greater the static friction factor. This is due to the role of the load, plastic deformation occurs at the contact with the stationary contact time, the actual contact area will be increased, micro-peaks are also embedded in each other. Deeper and cause.
6. Surface roughness
Contacts in the plastic case, since the surface roughness of the actual contact area is very small, so that the coefficient of friction can be almost free from the influence of surface roughness. For elastic or elastoplastic contact with dry friction, when the surface roughness is small, the mechanical action also small, while the molecular force larger role; vice versa. Visible, the friction coefficient decreases there will be a change in the surface roughness minimum.
All of the above factors, the impact on the friction factor is not isolated, but are linked mutual influence, should pay attention to this point in the analysis.
| Product Model | Inside Diameter | Outside Diameter | Thickness |
| 7306BEA NSK | 30 | 72 | 19 |
| 7306B NSK | 30 | 72 | 19 |