Volodymyr Okorokov

University of Strathclyde

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Donald Mackenzie

University of Strathclyde

Yevgen Gorash

University of Strathclyde

Ralph van Rijswick

Delft University of Technology

Gennadiy Lvov

National Technical University "Kharkiv Polytechnic Institute"

Tugrul Comlekci

University of Strathclyde

Xuran Xiao

University of Strathclyde

Marta Morgantini

University of Strathclyde

Holm Altenbach

Otto-von-Guericke University Magdeburg

Konstantin Naumenko

Otto-von-Guericke University Magdeburg

Cooperative Institutions

University of Strathclyde

Martin Luther University Halle-Wittenberg

National Technical University "Kharkiv Polytechnic Institute"

Luther University

Otto-von-Guericke University Magdeburg

University Hospital Magdeburg

National Polytechnic School

Delft University of Technology

University of Kuala Lumpur

Esslingen University of Applied Sciences

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Experimental Study of Autofrettage

Strength of Materials (2018)

Gennadiy Lvov Volodymyr Okorokov

Autofrettage

Hardening (computing)

10.1007/s11223-018-9968-7

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Citations (3)

МОДЕЛЮВАННЯ ПОШКОДЖУВАНОСТІ МАТЕРІАЛУ ПРИ ЦИКЛІЧНОМУ ПРУЖНО-ПЛАСТИЧНОМУ ДЕФОРМУВАННІ

Управління розвитком складних систем (2016)

Gennadiy Lvov Volodymyr Okorokov

The paper is devoted to modeling of the Bauschinger effect and material damage which occur at elastic-plastic deformation. The series of cyclic tension-compression tests of flat samples made from aluminum alloy D16 were conducted. Based on the experimental data a mathematical model of plasticity is developed. Damage parameter is introduced according to effective stress conception.

Bauschinger effect

Tension (geology)

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High cycle fatigue life assessment of notched components with induced compressive residual stress

International Journal of Pressure Vessels and Piping (2023)

Xuran Xiao Volodymyr Okorokov Donald Mackenzie

Compact tension specimen

Paris' law

10.1016/j.ijpvp.2023.105069

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Crack Arrest Analysis of Components With Compressive Residual Stress

Fatigue & Fracture of Engineering Materials & Structures (2024)

Xuran Xiao Volodymyr Okorokov Donald Mackenzie

ABSTRACT A finite element analysis and fracture mechanics methodology for determining the autofrettage pressure required to cause crack arrest in components under varying pressure loading are presented. Superposition of the autofrettage residual stress distribution and working load stress distribution is combined with ANSYS Separating Morphing and Adaptive Remeshing Technology (SMART) to determine the effective stress intensity factor as the crack grows. The condition for crack arrest is identified by comparison with a crack arrest model defining the crack propagation threshold stress intensity factor range for microstructurally short, physically short, and long cracks. The crack propagation threshold models of El Haddad and Chapetti are implemented and applied to fatigue analysis of stainless steel and low carbon steel double notch tensile test specimens with preinduced compressive residual stress. Based on comparison with fatigue test results, the Chapetti model is selected for use in the analysis of a 3D aluminum alloy valve body. The calculated minimum autofrettage pressure required to give crack arrest under a given working load cycle is found to be in good agreement with experimental observations from the literature.

10.1111/ffe.14539

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New formulation of nonlinear kinematic hardening model, Part I: A Dirac delta function approach

International Journal of Plasticity (2019)

Volodymyr Okorokov Yevgen Gorash Donald Mackenzie Ralph van Rijswick

Yield surface

Hardening (computing)

Strain hardening exponent

Necking

Stress–strain curve

Stress relaxation

Dirac delta function

10.1016/j.ijplas.2019.07.006

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Citations (16)

Plasticity-induced compressive residual stress effects in fatigue and corrosion fatigue

Volodymyr Okorokov

Corrosion Fatigue

Goodman relation

Source

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Fatigue and Corrosion Fatigue Life Assessment With Application to Autofrettaged Parts

Volodymyr Okorokov Donald Mackenzie Yevgen Gorash

This study investigates an effect of autofrettage on the fatigue and corrosion fatigue life of high pressure parts made from low carbon structural steel. To estimate the beneficial effect of autofrettage application, an extensive experimental program and advanced theoretical modelling are conducted and analyzed in this study. Accurate calculation of compressive residual stresses is achieved by application of a cyclic plasticity model which can precisely simulate a cyclic plasticity response of material. In terms of a fatigue life prediction methodology, a non-local stress based approach with a modified critical distance theory is used for prediction of the crack initiation stage providing conservative fatigue assessment. Because of the fact that the crack propagation stage can take a considerable part of the total life for autofrettaged parts, more accurate fatigue life calculation is performed by the use of a fracture mechanics approach. The total fatigue life time of autofrettaged parts is then calculated as a sum of the crack initiation and propagation stages.

Autofrettage

Goodman relation

Corrosion Fatigue

Residual strength

Cyclic stress

Carbon steel

10.1115/pvp2018-84536

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High Cycle Fatigue Analysis with induced Residual stress based on Fracture Mechanics

Procedia Structural Integrity (2024)

Xuran Xiao Volodymyr Okorokov Donald Mackenzie

A numerical method based on crack initiation and growth theory to predict the high cycle fatigue life with induced compressive residual stress is presented. Fatigue crack growth in a double-notched S355 low carbon steel specimen is considered. The total life of the specimen is divided into crack initiation life and crack propagation life, which can be calculated separately. To obtain the crack initiation life, an assumed crack initial length is employed to create an S-N equation for crack initiation. The process of crack propagation is simulated by finite element analysis (FEA) and the influence of compressive residual stress included by a stress superposition method, hence changing the stress intensity factor ratio. The total fatigue life with residual stress is calculated by corrected Paris law. Comparison of numerical fatigue results with previous experimental results showed good agreement, indicating that the proposed numerical fracture method is suitable for calculating high cycle fatigue life considering induced residual stress.

Paris' law

Compact tension specimen

10.1016/j.prostr.2023.12.012

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Експериментальне визначення ефекту Баушингера і пошкоджуваності матеріалу

Вісник Національного технічного університету «ХПІ». Серія: Динамiка та мiцнiсть машин (2014)

Volodymyr Okorokov

Present paper is devoted to an experimental determination of the Bauschinger effect and material damage which occur at elastic-plastic deformation. The series of cyclic tension-compression tests of flat samples made from aluminum alloy D16 were conducted. Given a phenomenon of buckling at compres-sion stage the flat samples were cut according to both ATSM standard and preliminarily conduction of the buckling analysis. Based on the experimental data a mathematical model of plasticity is developed in the way of improvement of the nonlinear kinematic hardening model by introducing of an additional function of previously accumulated plastic strain. For better correlation with experimental results the Mises plasticity criterion written in the form of the Baltov and Sawczuk’s model was modified by intro-ducing of a function which is intended to describe decrease of the yield stress during plastic deforma-tion. In order to model a reduction of the young’s module at unloading stage of the cyclic tension-compression test a material damage parameter was introduced according to the effective stress concep-tion. Numerical simulation of the cyclic tension-compression testing which accompanied experimental investigation has shown good coincidence with experiment results.

Bauschinger effect

Tension (geology)

Hardening (computing)

Strain hardening exponent

10.20998/2078-9130.2014.58.49374

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Citations (0)

High cycle fatigue analysis in the presence of autofrettage compressive residual stress

Fatigue & Fracture of Engineering Materials & Structures (2018)

Volodymyr Okorokov Donald Mackenzie Yevgen Gorash Marta Morgantini Ralph van Rijswick

Abstract An experimental and numerical investigation of the effect of residual compressive stress on the high cycle fatigue life of notched low carbon steel test specimens is presented. Experimentally determined cyclic stress strain curves for S355 low carbon steel are utilized in a finite element analysis plasticity modelling framework incorporating a new cyclic plasticity material model representative of cyclic hardening and softening, cyclic mean stress relaxation, and ratcheting behaviors. Fatigue test results are presented for standard tensile fatigue test specimens and novel double notch specimens. Double notch specimens are tested with and without compressive residual stress prior‐induced through tensile overload. It is shown that cyclic plasticity phenomena have a significant influence on the induced residual stress distribution and also on material behavior when fatigue tested in the high cycle regime. It is observed that higher initial compressive residual stresses magnitude does not necessarily lead to a longer fatigue life. Finite element analysis using the new cyclic plasticity material model shows this behavior is due to combined residual stress redistribution under fatigue test cyclic loading and cyclic hardening effects. A fatigue life methodology based on the stress‐life approach augmented by a critical distance method is proposed and shown to give good agreement with experimental results for test specimens with no induced residual stress. The results obtained for specimens with induced residual stress are more conservative, but the degree of conservatism is significantly lower than that in the conventional stress life approach. The proposed methodology is therefore suitable for analysis and design assessment of components with pre‐service induced compressive residual stress, such as autofrettaged pressure components.

Autofrettage

Hardening (computing)

Cyclic stress

Bauschinger effect

10.1111/ffe.12866

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Citations (11)