Modeling of spray-formed materials: Geometrical considerations

In this article, a mathematical model is formulated to predict the evolutio n and final geometry of an axisymmetric billet (i. e., round) obtained usin g an off-axis spray arrangement. The model is formulated by calculating the shape change of a profile curve of a billet surface, based on an axisymmet ric surface. On the basis of this model, a methodology to determine the "sh adowing effect" coefficient is presented. The modeling results suggest that there are three distinct regions in a spray-formed billet: a base transiti on region, a uniform diameter region, and an upper transition region. The e ffects of several important processing parameters, such as the withdrawal v elocity of substrate, maximum deposition rate, spray distribution coefficie nt, initial eccentric distance, and rotational velocity of substrate, on th e shape factors (e.g., the diameter size of the uniform region and the geom etry of the transition regions) are investigated. The mechanisms responsibl e for the formation of the three distinct regions are discussed. Finally, t he model is then implemented and a methodology is formulated to establish o ptimal processing parameters during spray forming, paying particular attent ion to deposition efficiency.