Quantification procedure of surface stress states and its application for measurements on glass using a reflection polarimeter

by Felix Ben Müller
Doctoral thesis
Date of Examination:2025-06-03
Date of issue:2025-07-14
Advisor:Dr. Georgios Ctistis
Referee:Prof. Dr. Alexander Egner
Referee:Prof. Dr. Stefan Mathias
Referee:Prof. Dr. Michael Seibt
Referee:Prof. Dr. Thomas Weitz
Referee:Prof. Dr. Christian Jooß
Referee:Prof. Dr. Vasile Mosneaga
Persistent Address: http://dx.doi.org/10.53846/goediss-11370

 

 

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Abstract

English

The investigation of surface stress of glass is highly requested for quality control processes, e.g. in the automotive glass industry. Since the state-of-art instruments are not really applicable to industrial processes due to their restrictions, especially the necessity of measuring in contact with the examined glass pane, another solution for surface stress determination is sought. The measurement method should be contactless and quantifiable. Therefore, a polarimetic setup has been developed, which is surface sensitive by the used reflection geometry and contactless without a special entrance optic. The polarimetric measurements qualitatively represent the impact of the surface stress to the optical anisotropy by polarisation-optical measures such as extinction angles as well as Jones or Stokes vector components. Moreover, it is quantifiable by determining the Stokes vector for two different incident polarisations or orientations of the plane of incidence. The quantification is based on the reconstruction of the surface stress from measurements of the polarisation states compared with a referencing database. A theoretical database used as reconstruction reference has been created for a certain geometry. Each dataset consists of the predicted Stokes vector calculated for the originating stress state, including the principle axes’ stress values and their orientation, and for two different incident polarisations or orientations of the plane of incidence. A functional model has been developed enabling the reconstruction of the stress state from the measured Stokes components by the referencing database. Quantifying theoretically calculated datasets by the theoretical reference database, it has been found an accuracy of 20◦ for the orientation of the two principle axes and an accuracy of 8MPa in the stress range of −15MPa ≤ σ ≤ 15MPa and 5MPa in the stress range of −5MPa ≤ σ ≤ 5MPa for their stress values. Furthermore, the experimental application of the reflection polarimetry has been characterised and validated by the transmissive response of the back-side reflection in comparison with a conventional transmission polarimeter. In contrast to the simple transmission image taken through two crossed polarisers of the transmission polarimeter the laser based reflection polarimeter has been equipped with a scanning device enabling twodimensional maps of the optical anisotropy represented by polarisation states. There, the spatial resolution corresponds to the size of the laser spot, which has a diameter of about 1mm. Both polarimeters have shown similar patterns representing the integrated volume stress, which could also be referenced by the two-dimensional maps recorded with the Scattered Light Polariscope, which is one of the commercial state-of-the-art instruments for measuring the surface stress. The approach of creating an experimental database for the stress reconstruction by measured data has shown the limits of the currently available glass samples with known stress states as well as the difficulties of applying external stress to a previously unstressed sample. Similar to the front-side surface sensitive maps representing the surface stress and overlying effects of the surface properties the experimental quantification approach has caused further research questions approaching a quantitative surface stress measurement.
Keywords: polarisation; polarimetry; ellipsometry; glass; dielectric medium; stress; photoelasticity; surface stress quantification; surface stress; anisotropy
 
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