THERMAL STRESS MEASUREMENT ON PISTON RINGS BY REAL TIME HOLOGRAPHIC INTERFEROMETRY

Abstract

The real time holographic interferometry (RTHI) technique was used to study the thermal stress on the motor cycle piston rings. The object holograms of piston rings were recorded and after processing the holographic plate, it was placed back on the holder. It was at this time, the processed holographic plate was illuminated by reference and object beams as the piston ring used to record the hologram was subjected to thermal stress. The generated interferograms before and after the piston ring was stressed were captured by a CCD camera for analysis. The results demonstrated interferograms abnormalities as a result of thermal stress. This was exhibited by interferograms bending and compressions. Using Atmosfringe version 3.3 software and origin version 8.0 software, the analysis of the interferograms were performed. The peak to valley (P-V) aberrations ranged from 0.0128λ to 1.2989λ for the whole range of measurements. Using the Fast Fourier Transform analysis of the interference fringes, phase changes were determined for each of the piston rings. From this result, it was evident that the three piston rings on the piston have different structural characteristics. This depends on the position of the ring on the piston due to their function. The ring near the head of the piston (compression ring), whose purpose is to seal the combustion chamber for maintenance of compression had less phase change and P-V aberrations due to thermal stress in comparison with the other two rings near its skirt.