by clicking the arrows at the side of the page, or by using the toolbar.
by clicking anywhere on the page.
by dragging the page around when zoomed in.
by clicking anywhere on the page when zoomed in.
web sites or send emails by clicking on hyperlinks.
Email this page to a friend
Search this issue
Index - jump to page or section
Archive - view past issues
button in toolbar for more information.
Metal Casting Technologies : March 2006
nesses inevitably show a distribution of various microstructure characteristics and thus have different local casting properties. The simula- tion of microstructure formation differentiates between macro- and micromodeling. Using macromodeling, microstructure characteristics can be derived from the results of the heat flow calculations. For instance, the secondary den- drite arm spacing of many aluminium alloys can be calculated from the local cooling rate and the temperature gradient (Fig. 17). The calculation of the formation of grains, eutec- tics, or microscopic gas precipitations can not be implemented in praxis yet. This calculation is often based on two-dimensional calcula- tions in microscopic scale and currently serves mainly as an instrument for the understanding of the microstructure formation. Simulation of residual stresses in castings Basically, in every casting with different wall thicknesses occur residual stresses. Different wall thicknesses of the casting lead to different cooling behavior after pouring as well as after heat treatment and thus result in residual stresses and in distortion of the casting (A. Egner-Walter, 1999). Usually, this distortion lies in an acceptable range. However, the existing re- sidual stresses can lead to a different behav- ior of the casting under load. In material pairs like aluminium cylinder crank cases with cast iron sleeves, massive residual stresses can occur due to the different expansion coefficients, too (L. Kallien, R. Rösch, 1999). Figure 18 Figure 19 Figure 20 www.metals.rala.com.au