Jaak Valgur

Measurement of Residual Stresses in the Cold-Rolled Fe-Ni-Mn/Invar Thermo-Bimetallic Plate

The paper presents a method for measuring residual stresses in normal thermo-bimetal Fe-Ni-Mn/Invar strips with a thickness of 0.76 mm. For this purpose, a setup was designed which permits to remove layers from a strip substrate by electrochemical etching. Residual stresses in the directions that are longitudinal and transversal to rolling are determined by the curvature method based on the layer growing/removing techniques. As a reference, residual stresses were also determined by hole-drilling technique. Tensile and compressive residual stresses arose both in active and in passive layers and were considerably higher when determined by the hole-drilling technique.

Residual Stress Measurement in Coated Plates Using Layer Growing/ Removing Methods: 100Th Anniversary of the Publication of Stoney’s Paper “the Tension of Metallic Films Deposited by Electrolysis”

In connection with the 100th anniversary of Stoney’s equations, some historical remarks are made with respect to the development of these equations. As an example of the extension of Stoney’s equations, a unique algorithm of the layer growing/removing methods is presented for determination of residual stresses in isotropic inhomogeneous coated plates. Using a computer program based on this algorithm, residual stresses are computed in the galvanic steel coating on the copper plate substrate.

Layer growing/removing method for determination of residual stresses in thin orthotropic inhomogeneous discs

An algorithm of the layer growing/removing method for computing of the residual stresses in thin orthotropic inhomogeneous circular disc is presented. The stresses are calculated from strain measurements on the free stationary contour or on the lateral surface, or from X-ray diffraction measurements on the disc’s moving contour. The suggested algorithm is programmed for PC. Two illustrative examples are presented.