Method for in-field measurement of permanent deformations on plant components, and assembly of instruments for performing said method

摘要

A method for measuring deformations on plant components provides for the application of a first periodic structure on a component (2) and for the comparison at a distance in time of said first periodic structure on the component with a second periodic reference structure in order to detect the presence of moiré fringes of interference that are produced as a consequence of a dimensional variation of the periodic structure on the component associated to a deformation of the component. The method is characterised in that said first periodic structure is applied on the plant component directly in field, and includes the following phases: buffing of a portion (1) of surface of the component (2), on which the first periodic structure must be applied, in order to remove superficial layers of oxides and to obtain a prescribed degree of roughness; electro-deposition on said buffed portion of surface (1) of a protective coating against oxidation comprising a layer of nickel and a layer of rhodium; deposition on said portion of surface (1) covered with the protective coating of a layer of photo-sensitive resins; exposure of said layer of photo-sensitive resins to two interfering beams of monochromatic light that generate on its surface a grid of fringes of interference having a first pitch (P) with a prescribed value; development of the photo-sensitive resins layer for the selective removal of the same in a way as to obtain a periodic structure having said first pitch (P) and comprising a plurality of photo-sensitive resins bands interspaced with channels in correspondence of which the protective coating is left uncovered; electro-deposition of nickel bands (24) in said channels between the bands of photo-sensitive resins; removal of said photo-sensitive resins bands in such a way as to obtain a grid having said first pitch (P) made of a plurality of nickel bands (24) embossed on said portion of surface covered by the protective coating. All aforementioned phases are performed on the component directly in field.