THE EFFECT OF PERMEABILITY DISTRIBUTION IN THE NUMERICAL ANALYSIS OF AEROSTATIC CERAMIC POROUS BEARINGS

• Published in: Tecnologia em Metalurgia, Materiais e Mineracao Vol. 20101124; pp. 12 - 22
• Main Authors: Nicoletti, Rodrigo, De Moraes Purquerio, Benedito, De Castro Silveira, Zilda
• Format: Journal Article
• Language: English
• Published: 01.01.2010
• Subjects: Bearings; Ceramics; Design engineering; Dynamical systems; Mathematical analysis; Mathematical models; Nonlinear dynamics; Permeability
• ISSN: 2176-1515

This work presents a numerically study about effect of permeability in the static characteristics of aerostatic ceramic porous bearings. This study is important for bearing design in function of inherent alterations during manufacturing and sintering processes that can induce variability in the permeability among porous ceramic samples. The mathematical modeling of such bearings is based on the modified Reynolds equation, which depends on the pressure-flow assumption (Darcy or Forchheimer) on the static and dynamic permeability coefficients of the porous matrix. In this work, the modified Reynolds equation is numerically solved considering the variations of permeability values, whose distribution was obtained from experimental tests of the ceramic samples. Monte Carlo method is used to introduce variability in the solutions. One focuses on the effects of such variation in the results of bearing loading capacity and bearing stiffness coefficient. Variations in dynamic permeability affect system linearity, which is quite obvious considering that this parameter only appears when quadratic pressure-flow assumption is adopted (system is non linear). However, variations in permeability which is adopted when linear pressure-flow assumption is considered, may lead to a system non-linearity if design variables will be in the edge of the linear region. Therefore, optimum regions of bearing load capacity and stiffness may vary significantly due to static permeability variation, thus hindering bearing design.