Eduardo de la Guerra Ochoa

A thermal resistances-based approach for thermal-elastohydrodynamic calculations in point contacts

This article presents a thermal resistances-based approach for solving the thermal-elastohydrodynamic lubrication problem in point contact, taking the lubricant rheology into account. The friction coefficient in the contact is estimated, along with the distribution of both film thickness and temperature. A commercial tribometer is used in order to measure the friction coefficient at a ball-on-disc point contact lubricated with a polyalphaolefin base. These data and other experimental results available in the bibliography are compared to those obtained by using the proposed methodology, and thermal effects are analysed. The new approach shows good accuracy for predicting the friction coefficient and requires less computational cost than full thermal-elastohydrodynamic simulations.This article presents a thermal resistances-based approach for solving the thermal-elastohydrodynamic lubrication problem in point contact, taking the lubricant rheology into account. The friction ...

Analysis of different multiaxial fatigue criteria in the prediction of pitting failure in spur gears

The aim of this article is to study the appearance of pitting in spur gears by taking account of different multiaxial fatigue criteria. The stress levels undergone by the teeth are considered in order to be able to predict their life and compare the fatigue strength of gear materials. The process begins calculating the stress field inside the teeth flanks due to the pressure and shear stress in the contact along the mesh. Once the stresses are known, the appearance of failure is studied by using different multiaxial fatigue criteria: Dang Van, Crossland and Liu-Mahadevan criteria. The accuracy of each criterion to predict pitting in gears is analysed using experimental data.

Film Thickness Formula for Thermal EHL Line Contact Considering a New Reynolds–Carreau Equation

This article presents thermal EHL calculations for line contacts using a new analytical form of the Reynolds equation for lubricants whose rheological behaviour follows a modified Carreau model proposed by Bair. The isothermal calculation process was presented in: de la Guerra (Tribol Int 82:133–141, 2015). A new parametric formula is hereby developed using the aforementioned Reynolds–Carreau equation and adding the thermal effects to the solving process. The accuracy of this formula is discussed by comparing the estimates with the experimental and numerical results available. This analytical formula provides a fast and easy calculation methodology with good accuracy within a reasonably wide range of operating conditions.

Friction coefficient in mixed lubrication: A simplified analytical approach for highly loaded non-conformal contacts

This article presents an analytical model for predicting friction in mixed lubrication regime. The calculations consider load shared between roughness asperities and the lubricant film, as well as the appearance of thermal effects in the contact and the influence of the lubricant rheology. Tests using tribometers have been performed to measure the friction coefficient in non-conformal surfaces for both point and line contacts. This allows verifying the results of the model under a broad range of experimental conditions with an influence on the lubrication conditions. Reasonably good precision has been found in the results obtained, which combined with a simplicity of use confers the model a high practical utility for rough estimates of the friction coefficient under mixed lubrication.This article presents an analytical model for predicting friction in mixed lubrication regime. The calculations consider load shared between roughness asperities and the lubricant film, as well as ...