Wear occurs at most solid surfaces that come in contact with other solid surfaces. While biological surfaces and tissues usually have the ability to repair minor wear damage, engineered self-healing materials only started to emerge recently. An example of a smart self-healing material is the material with imbedded microcapsules or microtubes, which rupture during crack propagation and release a healing agent that repairs the crack. Self-healing mechanisms are hierarchical in the sense that they involve interactions with different characteristic scale lengths. While traditional models of self-healing require equations with many degrees of freedom, taking into account the hierarchical organization allows us to reduce the number of equations to a few degrees of freedom. We discuss the conditions under which the self-healing occurs and provide a general theoretical framework and criteria for self-healing using the concept of multiscale organization of entropy and non-equilibrium thermodynamics. The example of a self-healed Al alloy reinforced with microtubes filled with Sn60Pb40 solder is discussed as a case study.

For the last decade, many researchers have been working to develop self-healing materials, and have obtained good results in the field of polymers. The research described in this paper applies the concept of self healing to fabricate self healing metal matrix composites, with the aid of models developed by the authors for the manufacturing processes and self-healing behavior. The development of self-healing metals is a novel idea that has not been explored in great detail yet. The concept of self-healing described in this paper consists of controlling a low temperature melting alloy imbedded within a higher temperature alloy to create a self healing composite (SHC). When the SHC is damaged or cracked, heat may be applied to the affected area whereupon the low melting alloy will melt and flow into the crack healing the damage and sealing the crack. This study consists of theoretical analysis, metallurgical design, experimental synthesis and Computational Fluid Dynamics of a self-healing aluminum alloy designed by the authors. The aluminum alloy matrix is reinforced with microtubes of alumina (Al2O3) that are filled with a low melting point solder alloy. The objective of the study reported here was to find the influence and efficiency of the solder in healing an aluminum matrix. To check this effect a crack was created in the metal surface, piercing the microtube(s) filled with solder, and then the SHC was heated above the melting point of the solder alloy.

The development of self-healing metals is a novel idea that has not been explored in great detail yet. The concept of self-healing described in this paper consists of incorporating a low temperature melting alloy imbedded within a higher temperature alloy to create a self healing composite (SHC). When the SHC is damaged or cracked, heat may be applied to the affected area whereupon the low melting alloy will melt and flow into the crack healing the damage and sealing the crack. This study consists of theoretical analysis and design of self-healing in aluminum alloy matrix. The experimental and Computational Fluid Dynamics of a self-healing were designed by the authors, the design consists in an aluminum alloy matrix reinforced with microtubes of alumina (Al2O3) that are filled with a low melting point solder alloy. The objective of the study reported here was to find the influence and efficiency of a low melting solder alloy in healing an aluminum matrix. To check this effect a crack was created in the metal surface, piercing the microtube(s) filled with solder, and then the SHC was heated above the melting point of the solder alloy to melt and examine the flow of molten solder alloy into the crack.

It has been a common practice that serpentine cooling passages are used in gas turbine blade to enhance the cooling performance. Insufficient cooled blades are subject to oxidation, creep rupture, and even melting of the material. To control and improve temperature of blade; it requires better understanding of a flow behavior and heat transfer inside the curved U-bends. The interactions between secondary flows and separation lead to very complex flow patterns. To accurately simulate these flows and heat transfer, and to improve the cooling performance, both refined turbulence models and higher-order numerical schemes are indispensable tools for turbine designers. Previous studies have shown that the flow and heat transfer characteristics through curved bends, even with a moderate curvature, cannot be accurately simulated. It is the conventional belief and practice that the usage of a proper turbulence model and a reliable numerical scheme achieves accurate computations. The three-dimensional turbulent flows and heat transfer in a square U-bend duct are numerically studied by using a nonlinear low-Reynolds number (low-Re) k-ω, k-ε and RSM models and the cubic terms are included to represent the effects of extra strain-rates such as streamline curvature and three-dimensionality on both turbulence normal and shear stresses. The finite volume method incorporated with a higher-order bounded interpolation scheme has been employed in the present study. The objective of this study is to validate the simulations using RSM, k-ω, and k-ε models with the experimental results. Three different Reynolds numbers, 36,000, 60,000 and 100,000, were used.