RKB Pressures Distributions and Depth Stresses Developed in Concentrated Contacts Between Elements with Non-Gaussian Rough Surfaces0 pages

th
Proceedings of the ASME 2012 11 Biennial Conference on Engineering Systems Design and Analysis
ESDA2012
July 2-4, 2012, Nantes, France
Paper Number: ESDA2012-82357
PRESSURES DISTRIBUTIONS AND DEPTH STRESSES DEVELOPED IN CONCENTRATED
CONTACTS BETWEEN ELEMENTS WITH NON-GAUSSIAN
ROUGH SURFACES
*
Ana C. Urzică
Technical University of Iasi
Iasi, 700050, Romania
Email: ana.tufescu@yahoo.com
Mihaela Rodica D. Bălan
Technical University of Iasi
Iasi, 700050, Romania
Email: ro_balan@yahoo.com
ABSTRACT
The main step in a contact analysis between rough surfaces
is the evaluation of the pressure distribution developed on the
real contact area. The normal pressure distribution can be used
further to predict subsurface stress, interfacial friction and
surface wear. Only few real rough surfaces are Gaussian, most
of that produced by manufacturing processes are non-Gaussian
having an arbitrarily orientation. The definition of the
roughness will include, in addition to the spatial
characteristics, information about spectral characteristics of
the surface, described with the use of autocorrelation function
ACF.
Conjugate Gradient Method in conjunction with Discrete
Convolution Fast Fourier Transform was refined and applied
to solve the constrained system of equations that governs the
pressure distribution between rough surfaces subjected to
contact loading in elastic dry conditions. The paper reveals
the role played by the spatial characteristics (standard
deviation σ, skewness Sk, and kurtosis K) as well as by
autocorrelation function on both the non-Hertzian pressure
distribution on contact area and depth distribution of von
Mises equivalent stress.
___________________
*Address all correspondence to this author
Spiridon S. Creţu
RKB Europe SA
Balerna, 6828, Switzerland
spiridon.cretu@rkbbearings.com
INTRODUCTION
Important machine elements such as bearings, gears, camfollower, traction drives, wheel-rail are running in concentrated
contact conditions and have their reliability influenced by
different modes of surface failures, Tallian [1]. The roughness
influences the risk of collapse for EHL film, Lugt, et al. [2], as
well as the stresses in the shallow layer of the contacting bodies,
Kim [3], Morales-Espejel, et al. [4] and Bhushan [5]. Because
all machined surfaces are rough to some degree, the knowledge
of the micro-topography has a crucial role in understanding the
thin film lubrication, friction, wear, and failure phenomenon,
Wang, et al.[6], Jeng [7], Bosman and Schipper [8], Sadeghi et
al. [9], Paulin et al. [10], Nélias et al. [11], Zhou [12]. Finally,
the manufacturing strategies have to select technologies able to
generate topographies with positive influence on contact
conditions.
There are different approaches to examine the roughness
effect on contact behavior and eventually to determine an
optimized surface roughness, Liu et al. [13]. Mean values as the
first spatial characteristics of roughness are presently
considered in the evaluation of fatigue life of rolling bearings,
Ioannides et al. [14], ISO 281:2007 [15].
The deterministic models require 2D or 3D computer
generated rough profiles having specific prescribed proprieties.
Patir [16] and Bakolas [17] used a linear transformation of a
matrix to produce rough surfaces with a specified
autocorrelation function (ACF). Mihailidis and Bakolas [18]
used this method for Gaussian surfaces with ACF from
roughness measurements of the gear flank. An autoregressive
moving average model was used by Watson and Spedding [19].
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