Experimental research of stress state and residual stresses of the hydropower pipeline branch model

Abstract

The paper presents experimental research of branch model in laboratory conditions. The branch model is, in fact, a reduced real branch whose basic dimensions are interrelated on the basis of similarity theory which arise from the conditions of stress equality on the branch model and the real branch. Using numerical methods - finite element methods, measuring points on the branch model, were determined. At the defined measuring points, experimental measurements of stress were performed, namely using: strain gauges and recording with 3D cameras. The branch model was quasi-statically loaded with different values of internal pressure during the experiment. The values of the internal pressure reached such a level that the maximum stress at the measuring point with the highest measured stress reached values far above the yield strength of the branch model material. The most important results of experimental research on the branch model can be expressed through the following items: - Verification of the fact that in the field of elasticity, there is a linear relationship between stress and internal pressure. - Disclosing what happens when the stresses exceed the value of the yield strength of the branch material, whether there are plastic deformations of the branch model. - Defining the dependence of stress on internal pressure in the field of elasticity and the zone of residual stresses. - Coming to conclusions regarding the distribution of stresses and residual stresses on the branch model.