bearings online
bearings online
Author :Admin | Publish Date:2013-04-09 10:11:12
Becoming higher in the front (leading edge) of the dent when the dented
surface is travelling slower than the smoother one, and vice versa (see fig. 1
for nomenclature). Nélias and Ville, Ville and Nelias have carried out numerous
experimental observations and numerical simulations of indentations in EHL
contacts with conditions of pure rolling and rolling-sliding. The numerical
simulations in Nélias and Ville with Newtonian fluids showed that any increase
of sliding [bearings online] increases the maximum shear stress
underneath the contact (e.g., higher sliding and higher friction as follows from
a Newtonian fluid). It was observed that the higher the sliding imposed on the
EHL contact, the higher the maximum shear stress in the subsurface and therefore
the shorter the life around the indentation.
In Ville and Nélias, further experiments were conducted and some
simulations also carried out for S = ±0.015. The experiments confirmed earlier
conclusions that the preferred site for spalls to develop depends on the skf bearings friction direction. A dented slower
surface tends to develop a spall at the leading edge of the dent, whereas a
dented faster surface tends to develop the spall at the trailing edge of the
dent. For pure rolling conditions, it is argued that the spall could appear on
either side. From dry contact experiments (Xu et al.) it was observed that the
spall appears in the back side (trailing edge) of the dent on the driving
surface; thus Xu et al. concluded that it is the friction force on the surface
that is the main mechanism promoting spalling of dented surfaces.
Indentations produced by different particles
The basic indent geometry has been idealized in fig. 2. Assuming that the
particle is entrapped in the contact (very large particles are not entrapped and
very small particles go through the film without causing indentations),
different indent shapes are produced – depending on the hardness of the particle
, its geometry and the hardness of the indented material. Indentations of large
size (ø) or very deep (hp) and with large shoulders (sp) are the most dangerous.
Fig. 3 shows different particle characteristics associated with the
corresponding indentations. Soft or malleable (ductile) particles (fibre or
metal) produce shallow bearings indentations with
shoulders. Brittle, hard particles shatter into many very small particles and
produce a cluster of tiny indentations. Friable tough particles produce a large
agglomerate of material that dents the steel, producing sharp shoulders.
Interaction between indentations and lubricant To better understand the
interaction of indentations with surrounding lubricant entrapped in a heavily
loaded contact, SKF has developed detailed models and conducted experiments to
study the phenomena associated with this problem. Here, the process of an
indentation or any other geometrical surface disturbance entering the contact
is described.
Surface geometrical disturbance entering the heavily loaded lubricated
contact When a surface disturbance enters the EHL contact, it generates two
different pressure and film thickness waves. The first one is the associated
pressure wave produced timken bearings by
the steady-state elastic deformation of the surface disturbance. This wave is
accompanied by an opposite wave in the film thickness, and it travels inside the
contact with the same speed as the surface that produces it (e.g.,u2); it is
called “particular integral”.
34BWD04BCA70
35BD219T12DDU
35BD5220AT1XDDUM3C01
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