Determination of residual stresses in structural elements with continuously distributed eigenstrains

The aim of the work is to demonstrate the application of the cutting method in determining the membrane component of residual stresses in elements of metal structures with continuously distributed eigenstrains, when methods of etching, drilling holes and X-ray diffraction can provide only limited information. The objects of the study area (a) a 250 × 25 × 10 mm bar made of aluminum-magnesium alloy, one narrow face of which is subjected to spot pressure treatment, (b) a 150 × 25 × 10 mm edge made of austenitic stainless steel, surfaced on the basis by wire-arc, (c) sheet ferritic-martensitic steel with a thickness of 14 mm, subjected to mechanothermic treatment. The method used consisted in (1) cutting a sample in the form of a bar cut from a workpiece by an electroerosion method into strips 1 mm thick at a coordinate along which the membrane component of residual stresses was inhomogeneously distributed, and (2) measuring the deflections of the strips and reconstructing from these data the distributions of the sought component of residual stresses and the incompatible part of the eigenstrains that generate these residual stresses, according to the relations obtained by the authors earlier. As the result in all considered problems the method showed fairly good solvability and revealed technologically important differences in the distributions of residual stresses in the height of the edge surfaced by wire-arc with and without layer forging with pneumatic tools, as well as in the thickness of the sheet subjected to unilateral rapid cooling with or without plastic bending in one direction or the other. The method does not require special laboratory equipment, and the cutting method used has a minimal effect on the material, symmetrically on both sides of the strips.

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