The VW 01129 standard, developed by the Volkswagen automobile company, applies to mechanical fasteners with metric ISO threads and flat head bearing surfaces.
Friction coefficient, tightening torque and preload force interact with each other. The friction coefficient is affected by the material combination and the type of surface protection. To ensure smooth threading of connections, the range of variation of the allowable coefficient of friction must be limited and the position of the average value determined. Appropriate lubrication integrated into or subsequently applied to the surface protective coating can meet these specifications.
The determined friction coefficients may deviate from the actual application friction coefficients due to various marginal conditions.
In the case of specially designed parts for which it is not possible to determine the coefficient of friction, the corresponding parts without the special design must be finished to obtain this value.
Since the friction coefficients are affected by the spin speed, the measurements are made in equal conditions. For this purpose, two-stage tightening at a speed of 200 min-1 and a final tightening in 20 minutes are foreseen for the coefficient of friction.
The overall friction coefficient is determined by the friction coefficients on the screw thread and under the screw head or nut bearing surface. Permissible tolerances apply both to the total coefficient of friction and to the individual coefficients of friction of the screw head or nut bearing surface and the coefficient of friction in the screw thread.
Simply, friction is the resistance one object encounters as it moves over another. Some objects are easier to rub than others. This is because an object exhibits more frictional resistance. In many problems, a surface is assumed to be smooth, ie not exerting any frictional force. But in real life this is not the case. A rough surface offers some frictional resistance.
The friction coefficient is a number that expresses the friction between two surfaces. The coefficient of friction between two equal surfaces is the same. The maximum frictional force, the coefficient of friction, is equal to the normal reaction force when an object is sliding or in constraining equilibrium. The frictional force acts parallel to the surfaces in contact and in a direction that opposes the action taking place.
Among the numerous test, measurement, analysis and evaluation studies it provides for businesses in various sectors, our organization also provides limit values testing services for friction coefficients within the scope of VW 01129 standard, with its trained and expert staff and advanced technological equipment.
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