Analysis of the variation of metals mechanical properties depending on operation time

Abstract

A long-term operating influence on mechanicalproperties variation of constructional materials is analysedin this article. During the exploitation of structures andpipelines the consistent surrounding influence causes corrosionof the structures materials. Beside the surroundinginfluence of the constant stress state affects structures too.For constant stresses mechanical properties of structuralelements are variable and the metal is ageing. The articlepresents experimental researches of hot-water pipelinesmaterial. From 20 - 40 years exploited pipelines specimenswere cut and tension test was fulfilled. The test resultsdisclosed that material strength stress increased minutely.The value of materials yield stress in exploited specimensshowed up later if compared with new material. In the bestway the changed materials plasticity properties wereexposed by specimens relative elongation, which characterizesmaterials fragility. Linear materials mechanical propertiesdependenty on lifetime is presented in the article.According to this linear law it is possible to calculate materialsmechanical properties of a structure, which isexploited, and assess safety of this structure.