Sand in Cylinders

Sand cores are used in the outer mold of cylinder heads before casting metal to build later cooling channels. This sand core is developed by the Chair of Metal Forming and Casting (UTG) at the Technical University of Munich.

Microstructure-Based Calculation Method for Core Sand

Project µ-Kern

Casting technology uses core sand to map the cooling channels in a cylinder head. Core sand consists of the granular material quartz sand formed to a porous composite by a binder. This is placed in the outer mold before the casting metal and destroyed after the casting process to produce a sand-free casting. We are developing micromechanical simulation models for core sand in cooperation with the Chair of Metal Forming and Casting (UTG) at Technical University of Munich.

 

Calculating the Properties of Inorganically Bound Core Sands

An innovative, inorganic silicate-based binder complies with strict environmental laws and enables sustainable, low-emission production. However, changing the components used changes the physical behavior of the core sand and the result is only visible after passing through the entire process chain. We are able to accelerate development by modeling and simulating the process.

Based on input parameters such as the manufacturing process and the materials used, we effectively calculate physical properties such as strength, gas permeability, and thermal conductivity. In the first phase of the project, we create a representative microstructure for the sand-binder composite and prepare high resolution images of existing composite structures using micro-computer tomography.

In der virtuell erzeugten Mikrostruktur sind Sandkörner in beige, der Binder in grau und der Porenraum zu sehen.
© Fraunhofer ITWM

In the virtually generated microstructure sand cores are simulated in yellow, binders in grey.

Validating the Structures Produced

The UTG partners measure the elastic properties of the sand and the binder. Then, we create virtual microstructures with stochastic methods and validate them by comparing them with structural images. We need to consider the following properties, since they influence the physical properties of the composites:

  • grain shape of the sand
  • size of the grains
  • size distribution of the grains in the sand
  • volume content of the binder
  • chemical composition of the binder

We investigate the dependence of the elastic stresses in the composite on the elastic properties of the materials used i.e., the quartz sand and waterglass. In the second part of the project, we use the Stokes/Navier-Stokes model to calculate the gas permeability and the thermal conductivity. Furthermore, we generalize the elastic model to nonlinear damage effects.