Experimental and numerical study of quenching complex-shaped metallic alioys with multiple, overlapping sprays

The present study constitutes a crucial step towards the development of a CAD based intelligent spray quetiching system capable of optimizing the mechanical properties (strength, hardness) of agehardenable aluminum alloys. The quenching of an L-shaped aluminum alloy with multiple, partially overlapping spray nozzles was successfully modeled using the finite element method. Spray heat transfer correlations, which relate the local heat transfer rate in each of the boiling regimes experienced by the surface to the local values of the spray hydrodynamic parameters (volumetric spray flux, mean drop diameter, mean drop velocity), were used as boundary conditions. The spatial distributions of the spray hydrodynamic parameters were modeled and incorporated into the finite element program. Axial nonuniformity in the heat transfer coefficient along the surfaces of long extrusions, which can lead to unwanted residual stresses, was eliminated by developing a method for optimizing the distance between adjacent nozzles. The numerical results were experimentally verified in a simulated industrial environment. This study is the first successful attempt at systematically predicting the temperature response of a quenched part from knowledge of only the part geometry and spray nozzle configuration. Integration of the finite element program with an optimization routine will yield a system capable of selecting the appropriate spray nozzle configuration for a new part prior to production ; thus, achieving superior part quality without conducting costly experimental tests.