On the static fatigue limit of cellular glass

logo_smallThis topic is important when the strength of cellular glass becomes an issue. Cellular glass has a much larger strenth than organic foams and in a lot of cases, a glass foam is selected for this reason.

A very important basic paper in that perspective is written a long time ago by S. M. WIEDERHORN and L. H. BOLZ . They discuss the static fatigue limit of glass already in 1970. Recent measurements with an atomic force microscope are confirming the original ideas.

staticfatiguelimitBoth papers show that glass has a static fatigue limit, which means that below this limit, a crack does not grow at all. It is also shown that this limit is decreased with water on the crack tip. Soda lime glass is the weakest glass, borosilicate is better while aluminosilicate is the best. The following figure became the standard in this field.

As a consequence, cellular glass is able to resist a load for ever if the static fatigue limit is not exceeded. This safe limit can be measured with acoustic emission like shown in another paper.

The graph also shows that between very slow (or no) crack growth and fast crack growth about a factor 2 is present for soda lime glass. This could be seen as the material factor between the short time compressive strength of GLAPOR cellular glass and the possible load on the long term. 1000 kPa compressive strength ware resists in principle a load of 500kPa forever.

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