Accession Number : ADA282337

Title :   Experimental Studies of Stress Measurement by Optical Fluorescence.

Descriptive Note : Final rept. Jan 91-Dec 93,

Corporate Author : CALIFORNIA UNIV SANTA BARBARA DEPT OF MATERIALS

Personal Author(s) : Clarke, David R.

Report Date : DEC 1993

Pagination or Media Count : 137

Abstract : A new method for the non-contact measurement of stresses in ceramics has been developed and applied to measuring the stress distribution in a wide variety of composites and polycrystalline ceramics. The basis of the technique is that stresses in a material alter the energy of the luminescence spectra from substitutional dopants. The technique of optical fluorescence was used to directly measure stress distribution and resolve a number of outstanding issues concerning residual stresses in composites. The residual stress distribution along sapphire fibers due to thermal expansion mismatch with the surrounding matrix were determined and used to test elasticity models for residual stress distribution. The report also introduced a method of obtaining the depth distribution along fibers by exploiting the finite depth of field of a microscope lens. The stress distribution in fibers was measured in-situ during the push-out of a fiber. By combining the measurements with finite element simulations, the residual stress distribution, the debond length as a function of applied load, the debond energy and the sliding stress were all determined for sapphire fibers having a variety of coatings in a TiAl matrix. Another method of obtaining the stress distribution, appropriate to long continuous fibers, was described

Descriptors :   *COMPOSITE MATERIALS, *CERAMIC MATERIALS, *FIBER REINFORCED COMPOSITES, *STRESS ANALYSIS, *FLUORESCENCE, SAPPHIRE, POLYCRYSTALLINE, IONS, SPECTROSCOPY, OPTICAL DETECTION, ALUMINUM OXIDES, LUMINESCENCE, CHROMIUM, RESIDUAL STRESS, MEASUREMENT, FIBERS, ZIRCONIUM OXIDES, THERMAL EXPANSION, FINITE ELEMENT ANALYSIS, MATRIX MATERIALS, TITANIUM ALUMINIDE, DOPING.

Subject Categories : Laminates and Composite Materials
      Ceramics, Refractories and Glass
      Optics

Distribution Statement : APPROVED FOR PUBLIC RELEASE