Monday, 22 April 2013
Professor Eckart Schnack from the Karlruhe Institute of Technology in Germany has given a Special Seminar in the newly inaugurated Neptune Lecture room at the Wessex Institute of Technology.
The lecture was entitled “Applying NTFA method for nonlinear homogenization of metal-ceramic composites of AlSi12/Al2O3”
Metal Matrix Composites (MMC) are important lightweight materials because of their excellent mechanic properties. In this work, the 3D model microstructure of AlSi12/Al2O3 with periodic spatial discretization is produced and used as the virtual material for the homogenization process. With an efficient description of the macroscopic thermo-mechanical behavior of metal-ceramic composites, the thermo-mechanical homogenization method, the non-uniform transformation field analysis (NTFA) was adopted and extended by reformulation of the underlying equations. This method is an ’’order reduction’’ technique specifically designed for homogenization problems with micro-mechanical motivation. The implementation of NTFA was based on the finite element method. The homogenized material model was implemented into ABAQUS in structural analysis. Comparison of numerical results with full-field simulation highlights the efficiency of NTFA for three-dimensional homogenization problems.
The lecture was followed with great interest by the participants and resulted in a long and lively discussion.
Prof Schnack is a Member of the Board of Directors of the Wessex Institute of Technology.
Friday, 5 April 2013
Prof Patrick Selvadurai, William Scott Professor and James McGill Professor, from the Department of Civil Engineering and Applied Mechanics at McGill University, Montreal in Canada, gave a special seminar at the Wessex Institute of Technology.
The lecture was entitled ‘Contact and Inclusion Problems in Biot Poromechanics’. Prof Selvadurai explained that poromechanics studies the behaviour of a porous media which is saturated with a fluid. The solid part of the material is referred to as the matrix which is permeated by a network of pores or voids which is filled with a fluid and are interconnected. It is usual to assume that both the solid matrix and the pore network are continuous and act like sponge. The theory can be applied to many substances such as rocks and soils and other materials. This type of porous material is a solid matrix which can be considered to be elastic and the fluid to be poroelastic. The poroelastic medium can be defined by its permeability and porosity as well as properties of its constituents both solid matrix and fluid.
Although Karl von Terzaghi is considered to be the father of soil mechanics, Maurice Biot developed the theory associated with poromechanics and published a series of papers between 1935 and 1957 on the theory of dynamic poroelasticity (known as Biot theory). This gives an understanding of behaviour of poroelasticity mediums using:
- The equation of linear elasticity for a solid matrix.
- Navier Stokes equation for viscous fluid.
- Darcy’s Law for flow through a porous matrix.
In the theory of dynamic poroelasticity there exists three types of elastic waves, the first of which is a shear transverse wave and the remaining two are longitudinal and compression waves, these are referred to as type I and II waves.
Several applications to Biots theory were given, one of which was the subsidence of the Leaning Tower of Pisa which relates to the contact problems associated with poroelasticity.
The lecture was well received and generated a lively discussion.