The development and application of pulsed magneto-photoelasticity

• Main Author: Conway, Andrew R.
• Published: University of Sheffield 2009
• Subjects: 666.15
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.505422

The problem of residual stress measurement in industrially manufactured tempered glass components has been addressed by the development and application of an experimental stress analysis technique known as pulsed magneto-photoelasticity. In the manufacture of tempered glass, residual stress is intentionally introduced in order to strengthen the material. However, the exact nature of the stress distribution remains unknown and, as a consequence, the strength of tempered glass products can vary significantly. A pulsed magneto-polariscope has been developed to allow the residual stress in glass to be quantified both through the thickness of the material and over the surface plane. Developments to the theory of the technique have enabled optical data, collected in the presence of multiple magnetic fields, to be used to provide a more detailed analysis of the residual stress distribution than has previously been possible. In the first phase of development, a pulsed magneto-polariscope with a continuous bore solenoid coil was designed and constructed. This enabled the proposed developments to be validated by testing birefringent specimens of epoxy resin and sectioned tempered glass test specimens. In addition, computer programs were developed to reduce the experimental complexity of the technique and to provide a platform upon which further research can be undertaken. The technique was extended by the design and inclusion of a novel component termed the dual coil solenoid which enabled high instantaneous magnetic flux densities to be generated, homogenously, over a wo.rking volume thereby allowing industrially manufactured tempered glass products to be analysed. Furthermore, this enabled test specimens of glass to be placed under known loads in order to precisely validate the proposed methodology. The pulsed magneto-polariscope was used to successfully quantify the residual stress distribution within a selection of automotive tempered glass products. The results demonstrated the ability of the developed technique to measure the residual stress in these components and to detect defects incurred in the manufacturing process.