ENGINE INLET AND EXHAUST VALVE HEAD STIFFNESS MEASUREMENTS USING LASER INTERFEROMETRY

This paper describes the use of laser interferometry to measure valve head stiffness. The work was done as part of an investigation into excessive valve seat wear. Holographic and electronic speckle pattern interferometry were used to measure and record valve head deformation during static loading. Holographic interferometry was used to produce resolution interferograms representing valve head deformation, while the technique of electronic speckle pattern interferometry provided the opportunity for real-time observation of valve deformation. Two separate valve loading conditions were used, one being a tensile load applied to the valve stem, and the other a hydrostatic pressure applied to the valve face. The hydrostatic loading method gave more consistent results and overcame alignment problems encountered with the tensile loading rig. The techniques described were used to evaluate various valve designs in order to optimise valve head stiffness with minimum weight increase.