SVILUPPO DI UN METODO DIGITALE PER L’ANALISI DELLE SOLLECITAZIONI IN COMPONENTI MECCANICI FORTEMENTE INTAGLIATI

The thesis proposed a experimental method for the assessment of the Notch Stress Intensity Factors (NSIF) of V-notches under mixed mode loadings without the use of particular techniques of experimental type in the preparation of the specimen and the use of sophisticated optical equipment laboratory. The NSIFs are calculated on the basis of a comparison of two digital photos of a calculation grid placed in the area of maximum stress concentration taken whit a digital camera. The photos are calculated to different load conditions and taken with a commercial digital camera. The method is particularly flexible in order to effect the introduction of an innovative compensation system errors and misalignments. The function performed by the compensation system can also seen as a calibration performed on the image and not a priori. The position of each dot in the refinement mesh is read automatically by the software. By using the parameter JV (J-integral applied to the V-grooves) provides directly NSIF of the notch under mixed mode (I and II). A mesh of dark spots is created on the surface near the notch tip and yhr spots have a diameter of abaut 20 pixel which is equivalent to a few tenths of a millimetre in standard applications. The technique is also applicable to plane models that reproduce the resistant section of a weld, in particular will be considered classical form of cruciform joints. Staric measurements were performed with normale tensile loads on speciments PVC or Aluminium. Is finally proposed an alternative employment of the technique for direct application on the surface instead of the notch in section for measuring the KI. This application is interesting because it potentially also be applied directly to the components in use. The accuracy of the experimental method with respect to the FE analysis is around then per cent.