METHOD TO DETERMINE SURFACE RESIDUAL STRESSES Russian patent published in 2016 - IPC G01L1/06 

FIELD: measurement equipment.

SUBSTANCE: method to determine surface residual stresses is realised by registration of light field scattered by investigated part surface, and the light field corresponds to initial condition of part surface, with the help of an optical measurement system, the source of radiation of which is a laser. At the same time they press a conical indenter into the tested material of the part to produce an imprint, record the light field scattered by the investigated surface of the part, corresponding to its condition after indenter impact; they produce interferograms by subtraction of two recorded light fields, which is distribution of normal movements in a flush around the imprint; recording of imprint diameter. Further they calculate coordinates of reference points on axes of symmetry of the imprint; determine sequence numbers of interferential strips passing through the reference points and determine maximum vertical movements in the flush around the imprint in the reference points according to the formula: where H - strip number, λ - laser wave length; and determine residual stresses with the help of all produced data according to the formula: where axes x and y are directed along axes of symmetry of the recorded distribution of movements; σ_f - limit of material fluidity of the surface layer of the part; ΔW - difference between the value of normal movement W_σ in the reference point measured in diagnostics of residual stresses and base movement W_rm.

EFFECT: reduced impact at investigated surface of a part and reduced indention force.

2 dwg