On the precision and accuracy of the acoustic birefringence technique for stress evaluation

• Autor(a) principal: Gonçalves Filho, Orlando João Agostinho
• Data de Publicação: 2011
• Outros Autores: Alves, Edson L., Souza, Mauro C. L, Instituto de Engenharia Nuclear, Universidade do Estado do Rio de Janeiro
• Tipo de documento: Artigo de conferência
• Idioma: eng
• Título da fonte: Repositório Institucional do IEN
• Texto Completo: http://carpedien.ien.gov.br:8080/handle/ien/2424
• topic: INAC 2011; Acoustic birefrigerance; Nuclear power industry

This paper presents a numerical procedure for estimation of the precision and accuracy of the acoustic birefringence technique as used in the Instituto de Engenharia Nuclear (IEN) for evaluation of residual and applied stresses in structures and components, mainly of the nuclear power industry. This procedure shall be incorporated to the signal processing module of the ultrasonic system used at IEN’s Ultrasonic Laboratory to account in an automatic and systematic way for the uncertainties in the input data and their propagation throughout the calculations. The acoustic birefringence is generally defined from the speeds of two mutually orthogonal volumetric waves of normal incidence, but when the use of a pulse-echo measurement system is feasible, the birefringence can be defined directly from the time-of-flight of the waves, since they travel the same physical space. The times-of-flight of the waves can thus be regarded as the primary variables of interest. They are estimated by coupling the mathematical techniques of cross correlation and data interpolation, whereas the material’s acoustoelastic constant is determined via a weighted linear regression. An Excel spreadsheet performs all calculations taking into account the uncertainties and the number of significant digits in the results. As an example of the procedure developed, the estimation of the precision and accuracy in the evaluation of the stresses acting in a beam under bending is presented. The analytical solution derived from the strength of materials theory was used as the reference value for accuracy estimation purpose