Low-cycle strength of damaged T-joint
Journal Title: Вісник Тернопільського національного технічного університету - Year 2015, Vol 80, Issue 4
Abstract
Stress-strain state and low-fatigue strength of full-scale sample of T-joint with artificial volumetric surface defects under hydraulic inner pressure loading as well as mechanical, cyclic and structural features of material from its different zones have been investigated. Using finite element method (FEM) data on structural stress concentration and stress concentration caused by geometric parameters of the defect and its location on the surface of flush T-joint made from steel 10 were obtained. The tensile and low-cycle tests of material were carried out. The difference in deformation of metal from typical areas of T-joint under static and cyclic loading was established. It is caused by variant morphology of the metal microstructure (structural anisotropy of deformation) in its specific areas that was formed during manufacturing process of the T-joint. Differences of metal microstructure in characteristic areas of T-joint resulted in strengthening and significant loss of the plasticity in one of the zones and corresponded reducing (4..5 times) of the cyclic durability of this area relatively to other investigated areas. Cyclic hydraulic test of T-joint with the artificial volumetric surface defects that simulated corrosion-erosion damage was fulfilled. It was revealed that strain in the defect located along the coupling line of main pipe and branch in the area of structural stress concentration under internal pressure is 2 – 3 times higher than strain in defect with the same geometric parameters at the surface of straight pipe. On the base of investigation of the defect fracture area the mechanism of crack propagation was established. It includes not only formation of facets of brittle and quasibrittle transcrystallite fracture, but regions of the fatigue grooves as well. Number of the groove steps corresponds to the number of cycles for formation of through wall crack in the defect. The failure number of cycles in the area of the defect is satisfactorily consistent with the predicted results using experimental and calculated fatigue curves on the one hand, and results of fractography on the other. It was shown during assessment of the damaged T-joint mechanical properties of metal in its characteristic areas, structural stress concentration and the concentration of stress caused by the presence of defect must be taken into account.
Authors and Affiliations
Petro Yukhysmets, Oleksii Gopkalo, Olena Gopkalo
Keywords
Related Articles
- EP ID EP570823
- DOI -
- Views 69
- Downloads 0
Experimental research of deformation zone of adaptive clamping elements for lathe jaws chucks
The paper deals with the experimental research of clamping surface deformation zone of adaptive clamping jaw to equip lathe jaws chucks during machining work pieces of different diameters. The directly proportional displ...
Mathematical modeling of non-isothermal adsorption mass transfer in nanoporous catalysts
The mathematical model of non-isothermal adsorption mass transfer in micro- and nanopores of intraparticle and interparticle spaces catalytic media, which considers effect of temperature during adsorption process, has be...
Fracture pecularities of prestressed steel reinforcement under hydrogenation in the model working medium
Pecularities of fracture behaviour of progressively drawn pearlitic steels from the initial hot rolled bar (not cold drawn at all) to the final commercial product (prestressing steel wire) were investigated in air and un...
Modelling of mechanical behaviour of shape memory alloys using finite elements method
Superelastic behaviour of Ni-Ti alloy wire under variable amplitude loading was simulated and experimentally studied. Mechanical properties and phase transformation stresses (𝜎𝑀𝑠, 𝜎𝑀𝑓, 𝜎𝐴𝑠, 𝜎𝐴𝑓) of the material were obta...
Influence of thermal heterogeneity on deformation of thin circular cylindrical shell
Thermal deformation of the long cylindrical shell which is taking place in an external temperature field is considered. It is supposed that the material of the shell is heterogeneous, which results in dependence of facto...