M. Mukherjee

Bio: M. Mukherjee is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topic(s): Metal foam & Blowing agent. The author has an hindex of 16, co-authored 45 publication(s) receiving 711 citation(s). Previous affiliations of M. Mukherjee include Indian Institute of Science & Applied Materials.

Structure and deformation correlation of closed-cell aluminium foam subject to uniaxial compression

Abstract: We report the results of an experimental and numerical study conducted on a closed-cell aluminium foam that was subjected to uniaxial compression with lateral constraint. X-ray computed tomography was utilized to gain access into the three-dimensional (3-D) structure of the foam and some aspects of the deformation mechanisms. A series of advanced 3-D image analyses are conducted on the 3-D images aimed at characterizing the strain localization regions. We identify the morphological/geometrical features that are responsible for the collapse of the cells and the strain localization. A novel mathematical approach based on a Minkowski tensor analysis along with the mean intercept length technique were utilized to search for signatures of anisotropy across the foam sample and its evolution as a function of loading. Our results show that regions with higher degrees of anisotropy in the undeformed foam have a tendency to initiate the onset of cell collapse. Furthermore, we show that strain hardening occurs predominantly in regions with large cells and high anisotropy. We combine the finite element method with the tomographic images to simulate the mechanical response of the foam. We predict further deformation in regions where the foam is already deformed.

The effect of cooling rate on the structure and properties of closed-cell aluminium foams

Abstract: The application of different cooling rates as a strategy to enhance the structure of aluminium foams is studied. The potential to influence the level of morphological defects and cell size non-uniformities is investigated. AlSi6Cu4 alloy was foamed through the powder compact route and then solidified, applying three different cooling rates. Foam development was monitored in situ by means of X-ray radioscopy while foaming inside a closed mould. The macro-structure of the foams was analysed in terms of cell size distribution as determined by X-ray tomography. Compression tests were conducted to assess the mechanical performance of the foams and measured properties were correlated with structural features of the foams. Moreover, possible changes in the ductile brittle nature of deformation with cooling rate were analysed by studying the initial stages of deformation. We observed improvements in the cell size distributions, reduction in microporosity and grain size at higher cooling rates, which in turn led to a notable enhancement in compressive strength. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Fatigue of a laterally constrained closed cell aluminum foam

Abstract: An experimental investigation into the constant stress amplitude compression-compression fatigue behavior of closed-cell aluminum foam, both with and without lateral constraint, was conducted. Results show that while the early stages of strain accumulation due to fatigue loading are independent of constraint, the rapid strain accumulation stage behaviors are sensitive to the constraint. This was ascribed to the noticeable hardening with plastic deformation observed under constraint during quasi-static loading, which in turn reduces the effective maximum stress experienced by the foam specimen during fatigue loading. This was demonstrated through a simple empirical model that connects fatigue strain accumulation without constraint to that under constraint. Complementary X-ray tomography experiments suggest that the fatigue behavior of the foams is relatively less sensitive to morphological defects such as missing walls than the quasi-static mechanical properties such as plastic strength. Evaluation of the energy absorption behavior suggests that the damage that accumulates during fatigue does not affect the energy-absorbing ability of the foam adversely.

Defect generation during solidification of aluminium foams

Abstract: The reason for the frequent occurrence of cell wall defects in metal foams was investigated. Aluminium foams often expand during solidification, a process which is referred as solidification expansion (SE). The effect of SE on the structure of aluminium foams was studied in situ by X-ray radioscopy and ex situ by X-ray tomography. A direct correlation between the magnitude of SE and the number of cell wall ruptures during SE and finally the number of defects in the solidified foams was found.

Microporosity in aluminium foams

Abstract: We studied microporosity in the metallic matrix of aluminium foams produced by the powder metallurgical route both with and without application of a blowing agent. Microporosity was studied in-situ in liquid metal foams as well as ex-situ in the solidified microstructures. In-situ studies were carried out using synchrotron X-rays. Quantitative analyses of the amount and distribution of microporosity inside cell walls, Plateau borders and nodes were performed on 2D micrographs and on 3D reconstructed volumes generated by X-ray tomography. We studied the influence of alloying elements, blowing agent and holding time on the amount and type of micropores. The mechanisms of microporosity formation and the evolution of microporosity via diffusion of hydrogen and by coalescence are discussed. It was observed that alloy composition and holding time have a strong influence on microporosity. Different possible strategies to control microporosity are suggested.

Porous Metals and Metallic Foams: Current Status and Recent Developments†

Abstract: Porous metals and metallic foams are presently the focus of very active research and development activities. There are currently around 150 institutions working on metallic foams worldwide, most of them focussing on their manufacture and characterisation. Various companies are developing and producing these materials which are now being used in numerous industrial applications such as lightweight structures, biomedical implants, filters, electrodes, catalysts, and heat exchangers. This review summarizes recent developments on these materials, with particular emphasis on research presented at the latest International Conference on Porous Metals and Metallic Foams (MetFoam 2007).

Commercial Applications of Metal Foams: Their Properties and Production

Abstract: This work gives an overview of the production, properties and industrial applications of metal foams. First, it classifies the most relevant manufacturing routes and methods. Then, it reviews the most important properties, with special interest in the mechanical and functional aspects, but also taking into account costs and feasibility considerations. These properties are the motivation and basis of related applications. Finally, a summary of the most relevant applications showing a large number of actual examples is presented. Concluding, we can forecast a slow, but continuous growth of this industrial sector.

Light‐Metal Foams—History of Innovation and Technological Challenges

Abstract: The history of metallic foams and the key innovations that have led to the variety of processing methods known today are reviewed. It is evident that the idea of foaming metals is very old and that most of the techniques used today have been proposed already in the 1950s. The most important milestones in the development of foaming technologies and the some of the attempts to commercialise metal foams are reviewed.

Compression fatigue behavior of Ti-6Al-4V mesh arrays fabricated by electron beam melting

Abstract: This paper focuses on the compression fatigue behavior of Ti–6Al–4V mesh arrays with high porosities of ∼60–85%, which were fabricated by an additive manufacturing technique using electron beam melting. The results show that their fatigue lives are mainly determined by uniform deformation through the entire specimens, while their failures are characterized by rapid strain accumulation and a severe crush band at an angle of 45° to the cyclic loading direction. The relation between the relative fatigue strength and relative density can be evaluated by the well-known Gibson–Ashby model with the exponential factor n being 2.7, which is higher than the reported data for aluminum and nickel foams, and almost double the idealized value (n = 1.5) of a stochastic open cellular foam. The underlying mechanism of fatigue failure appears to be interaction between cyclic ratcheting and fatigue crack initiation and propagation, while the former plays a dominant role in fatigue life. TEM observations found that dislocations are generated along the interface of the α′ phase and their generation becomes more evident with an increase in the relative density. This would contribute to the retardation of cyclic ratcheting and an improvement in the fatigue strength.