Optical Fleximeter

The Optical Fleximeter measurement technique, included in ELS-MDF instrument:

○ Performs flexion measurements on a sample placed on two holding rods, 70mm spaced

○ Is equipped with a camera that frames the center of the sample. It is free to move downwards or upwards during the test

The applications of fleximeter include:

  • Measurement of ceramic body pyroplasticity
  • Study of deformation after firing  of glazed ceramic materials and identification of coupling temperature
  • Bending of green tiles due to consecutive applications of water

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Study of the pyroplastic behaviour of ceramics:

Pyroplastic behaviour during the firing cycle_Jpeg

Pyroplasticity causes deformation defects which interests all kinds of ceramic bodies (porous, completely sintered, glazed or not glazed). Above the glass transition temperature, the glassy phase present into the ceramic body enters into a supercooled liquid state, according to which the viscosity rapidly decreases as the temperature increases. In this way, the material can lose its consistency and deform.

After firing, BODY 1 has a deformation of about 2,5 mm, BODY 2 of about 4 mm, while BODY 3 cannot reach the end of the test because of a too high deformation rate.

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Study of the state of tension of a glazed tile:

FLEX 04_Jpeg.jpg

The state of tension between glaze and body depends essentially on two factors: the relation between their thermal expansion curves and their coupling temperature. The bending curve on a fired glazed piece of tile is fundamental to identify the coupling temperature and also reveals the qualitative level of stress between body and glaze. Combining the flexion curve of the glazed tile (here in green) with the thermal expansion curves of body and glaze allows a complete quantitative study of the residual stresses. In this case the glaze results under compression.

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Bending of green tiles due to consecutive applications of water (simulation of the glazing process) at room temperature:

FLEX 03_JPeg

An excessive bending is a frequent problem on the glazing line, because the deformation imposed by the decoration machines on the green tiles is sometimes so high to provoke the rupture of the material. A very important characteristic of the green tiles is the ability to absorb considerable water quantities without bending too much. The following tests were performed applying 8cc of water in four steps.