Anderson: Dynamics and Stability of Freezing Metallic Foams
Oct
17
Fri 2:00 PM
When Friday, October 17, 2008
Time
2:00 PM - 3:00 PM
Where Tech M416
Contact Molly Scanlon
847-491-5586
Group McCormick-Colloquia Engineering Sciences and Applied Mathematics
Applied Math Colloquium
Title: Dynamics and Stability of Freezing Metallic Foams
Speaker: Anthony Anderson, Northwestern University
Special Note: This talk is part of the RTG Seminar Series.
Abstract: During the solidification of metallic foams, the thin liquid bridges (lamellae) separating adjacent gas bubbles are frozen. When this process is carried out successfully, a light-weight porous solid is produced which exhibits a high ratio of rigidity to specific weight and excellent energy absorption on impact. These are desirable properties in a number of applications, particularly those in the automotive and aerospace industries. In aqueous foams, surfactant is injected to immobilize the gas-liquid interfaces and stabilize the foam. In fact, the study of aqueous foams reduces to that of surfactant transport. In metals, there is no surfactant available, and so a principle difficulty is solidifying them comes from rapid coarsening ahead of the freezing front, which is the result of film rupture followed by coalescence of the adjacent gas bubbles. These coarsening dynamics are ultimately controlled by the microflows in individual lamellae which are the central focus of this presentation. In the first part, I will discuss the nature of the microflows in the vicinity of the freezing front. A simplified model has been developed to examine these flows, heat transfer, and interfacial shapes using an asymptotic analysis which takes advantage of the small aspect ratios of foam lamellae. In the second part, I will present current work on lamellae thinning and rupture. This talk is part of the RTG Seminar Series.
Title: Dynamics and Stability of Freezing Metallic Foams
Speaker: Anthony Anderson, Northwestern University
Special Note: This talk is part of the RTG Seminar Series.
Abstract: During the solidification of metallic foams, the thin liquid bridges (lamellae) separating adjacent gas bubbles are frozen. When this process is carried out successfully, a light-weight porous solid is produced which exhibits a high ratio of rigidity to specific weight and excellent energy absorption on impact. These are desirable properties in a number of applications, particularly those in the automotive and aerospace industries. In aqueous foams, surfactant is injected to immobilize the gas-liquid interfaces and stabilize the foam. In fact, the study of aqueous foams reduces to that of surfactant transport. In metals, there is no surfactant available, and so a principle difficulty is solidifying them comes from rapid coarsening ahead of the freezing front, which is the result of film rupture followed by coalescence of the adjacent gas bubbles. These coarsening dynamics are ultimately controlled by the microflows in individual lamellae which are the central focus of this presentation. In the first part, I will discuss the nature of the microflows in the vicinity of the freezing front. A simplified model has been developed to examine these flows, heat transfer, and interfacial shapes using an asymptotic analysis which takes advantage of the small aspect ratios of foam lamellae. In the second part, I will present current work on lamellae thinning and rupture. This talk is part of the RTG Seminar Series.
