APPLICATION OF INTERFEROMETRIC STRAIN ROSETTE TO RESIDUAL-STRESS MEASUREMENTS

An interferometric strain rosette (ISR) technique is extended to resid ual stress measurements. The ISR technique is based on diffraction and interference of laser light reflected from three micro-indentations d epressed in a specimen surface. Three in-plane strain components betwe en the three micro-indentations can be measured simultaneously. Theref ore the ISR enables a determination of two normal and one shear strain components. For many applications, the ISR is superior to a resistanc e strain rosette due to its short gage length and non-contacting natur e. By applying an ISR to a material surface, residual stresses at the location of the ISR can be obtained through measurement of residual st rains relieved via hole-drilling. Since the gage length can be as shor t as 50 mu m, the ISR is capable of recording high strain gradients an d it allows the strains close to the hole to be measured. The size of the hole can be small and precise location is not required. Since the ISR technique is non-contacting, it may be used to measure residual st resses in hostile environments. Copyright (C) 1996 Elsevier Science Li mited.