José Risso

Numerical and Experimental Stress Analysis of an Internal Combustion Engine Valve During the Closing Event

This paper presents a numerical methodology to predict the stress evolution in an internal-combustion engine valve during the closing event. The problem is studied using a three-dimensional finite element model, showing that the seating process of the valve produces high bending stresses which are not demonstrated by two-dimensional models. The valve stem stress response under impact was registered experimentally using strain gauges and then compared with the finite element method solutions, showing good agreement. The main contribution of this paper is the identification of the factors which generate the development of impact stresses during the closing event in an internal- combustion engine valve and which could result in fatigue failure.

Computation of Stress and Strain Evolution During Heat Treatment of Work Rolls

We present a numerical simulation of heat treatment of cast metallic alloys by the finite element method, to predict strains and stresses produced during the said process. From a computational point of view, this problem involves a coupled thermal-metallurgical-mechanical analysis modeled as a non-stationary and non-linear process. The calculation of metallurgical properties is coupled directly with thermal analysis. Material properties, which are dependent on temperature and microstructural composition, are rewritten for the purpose of the analysis as functions of temperature and time. Results of thermo-metallurgical analysis are taken as data for the subseguent mechanical analysis. The simulation was successful and proved the causes of failure during heat treatment of a centrifugally cast three-layered Hi-Chrome work roll.