A thermomechanical study of the effects of mold topography on the solidification of Aluminum alloys

Abstract

A thermomechanical study of the effects of mold topography on the solidification of aluminum alloys at early times is provided. The various coupling mechanisms between the solid-shell and mold deformation and heat transfer at the mold/solid-shell interface during the early stages of aluminum solidification on molds with uneven topographies are investigated. The air-gap nucleation time, the stress evolution and the solid-shell growth pattern are examined for different mold topographies to illustrate the potential control of aluminum cast surface morphologies during the early stages of solidification using proper design of mold topographies. The unstable shell growth pattern in the early solidification stages results mainly from the unevenness of the heat flux between the solid-shell and the mold surface. This heat flux is determined by the size of the air-gaps formed between the solidifying shell and mold surface or from the value of the contact pressure. Simulation results show that a sinusoidal mold surface with a smaller wavelength leads to nucleation of air-gaps at earlier times. In addition, the unevenness in the solid-shell growth pattern decreases faster for a smaller wavelength. Such studies can be used to tune mold surfaces for the control of cast surface morphologies.

The Mechanical Properties Research of Stress Frame Casting under Different Solidification Conditions

“…3) manufactured four samples. The thin rod parts were prepared as φ5 standard tensile test bars, whereas the thick rod parts were produced as φ10, after maching, those tensile test bars were polished using SiC sand paper (from 400 to 2000 grit) in order to eliminate the scratches of machined surfaces [12,13]. Tensile testing was carried out on an WDW-100KN testing machine at room temperature with the chuck speed of 2mm﹒min -1 .…”

Explicit coupled thermo‐mechanical finite element model of steel solidification

“…Lee and coworkers [4] recently developed a finite volume method for coupled fluid flow, heat transfer, and stress of solidifying shells in a beam-blank mold. Nevertheless, almost all thermo-mechanical models of solidification processes have applied finite element methods with implicit solution methods [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. This is due to their efficiency over finite-difference and finite volume methods in fast, stable convergence of the highly coupled and stiff non-linearities typically encountered in stress problems, especially with complex geometries.…”

“…A separate creep model can be added to roughly account for the time dependency [8]. More accurate elastic-viscoplastic models have been used [1,5,[9][10][11][12][13][14][15][16][17][18][19][20], which unify the phenomena of creep and plasticity together through a structure parameter such as inelastic strain in the solid. Integration of these time-dependent constitutive laws is a very challenging computational task due to their numerical stiffness.…”

Efficient thermo-mechanical model for solidification processes

“…Later, separate creep laws were added [9,10]. With the rapid advance of computer hardware, more computationally challenging elastic-viscoplastic models have been used [2,3,6,[11][12][13][14][15][16][17][18] which treat the phenomena of creep and plasticity together since only the combined effect is measurable. Most models use a Lagrangian approach with a fixed mesh due to its easy implementation, although an alternative Eularian-Langrangian approach has also been used [6,14].…”