Sensitivity study on the effect of thermocouples positioning on the heat transfer coefficient determination

Abstract

Casting is a widely used manufacturing process for complex shaped-parts with high stiffness due to the monolithic integrity. An added value to these demands is high dimensional precision which casting cannot achieve in most cases. To ensure defect-free products and dimensional precision like side walls, radii, the cast has to be cooled according to material type, product size, filling rate and mold design. Nowadays, the cooling control is based mostly on empirical knowledge. To avoid product quality deterioration it is necessary to have an intelligent control system, which adjusts the cooling parameters according to varying casting conditions. To play with the casting parameters, their influence on the cast part is needed to be scientifically known in order to predict it. Numerical simulation is the suitable tool for getting different influences of the casting parameters on the final part shape and dimensions. Instead of costs of test and trials, numerical simulations
needs computation time. The present work focuses on the determination of the heat transfer coefficient at the part/mold and part/core interfaces in permanent mold casting, by a gradient extrapolation method. Using adequate equipment, temperature field was monitored during solidification and cooling of a hollow cylinder cast part made of Al-7%Si alloy. By varying the thermocouples positions, the optimal locations of the measurement points were determinad in order to calculate a very accurate heat transfer coefficient.