G. Matvienko - Academia.edu (original) (raw)

Papers by G. Matvienko

ABSTRACT. This work deals with the notch sensitivity of sharp notches under multi-axial fatigue l... more ABSTRACT. This work deals with the notch sensitivity of sharp notches under multi-axial fatigue loading. The main discussion concerns the differences in notch sensitivity at high cycle fatigue regime, between tensile, torsional and combined loading. For this comparison, this paper considers a large set of fatigue experimental tests and several computing simulations analyzed with several notch theories for predicting fatigue life of a component. The considered experimental data, taken from literature, deal with the fatigue behavior of cast iron circumferentially V-notched specimens under tension, torsion, and combined loading mode. This paper tries to apply several techniques for theoretical strength assessment and to compare different procedures. The examined procedures need the computation of many parameters, focusing on the importance of using the tensile resistance to set these parameters or using both tensile and torsion resistances. However, the improvements obtained by means o...

Inorganic Materials, 2010

ABSTRACT A technique for experimental determination of fracture toughness and hydrogen embrittlem... more ABSTRACT A technique for experimental determination of fracture toughness and hydrogen embrittlement of pipes made of API 5L X52 steel is described. The tests were performed using arc-shaped specimens with a notch cut out from pipes under the conditions of a three-point bend. The fracture toughness was determined in terms of the J-integral and the stress intensity factor at the notch tip. The value of K ρ,c was established using the volumetric method based on the experimentally measured critical load and the results of the FEM calculation of the distribution of elastic-plastic stresses ahead of the notch tip, and J ρ,c was determined using the method of separable functions. The effect of hydrogen embrittlement was studied using electrolytically prehydrogenated specimens.

ABSTRACT. The plastic zone is theoretically and numerically analyzed for various combinations of ... more ABSTRACT. The plastic zone is theoretically and numerically analyzed for various combinations of the nonsingular terms xx T to zz T ratios in connection with specimen thickness under mode I loading. The plastic zone size distribution is based on the Mises yield criterion for mode I conditions and mapped in the specimen thickness direction. It is shown that the plastic zone size is affected by the zz T -stress, i.e. there is strong effect of out-of-plane constraint (thickness) on crack tip plastic zones. In addition, to study the effect of thickness and loading mode mixity (mode I and II) of the specimen on the singular (K I , K II ) and the non-singular ( xx T , zz T ) terms along the 3D crack front, three-dimensional stress fields are analyzed by means of finite element analysis. The strong effect of thickness and mixed mode loading conditions on the zz T -stress is observed. At the same time, there is not the effect of thickness on the nonsingular xx T -stress at the same loading ...

Theoretical and numerical analysis of the joint influence of the non-singular components of the T... more Theoretical and numerical analysis of the joint influence of the non-singular components of the T-stresses on the crack tip plastic zone estimated by the von Mises yield criterion is carried out under mode I loading in connection with specimen thickness. Calculations are performed for three thicknesses of the CT specimen. The amplitudes of the non-singular terms in the three-dimensional series expansion of the crack front stress field are the terms Txx and Tzz which describe in-plane and out-of-plane constraint, respectively. The plastic zone is analyzed for various combinations of the terms Txx to Tzz ratios. The plastic zone size distribution is mapped in the specimen thickness direction. It is shown that the plastic zone is affected by the Tzz-stress, i.e. there is strong effect of out-of-plane constraint on crack tip plastic zones. Crack tip plastic zone in the middle plane of the specimen decreases with the increase of specimen thickness.

Russian Physics Journal

The paper presents brief information about the establishment and development in Tomsk of high-res... more The paper presents brief information about the establishment and development in Tomsk of high-resolution molecular spectroscopy – the field of science closely related to a study of the optical properties of the atmosphere. The methods and the current state of high-resolution laser spectroscopy and Fourier spectroscopy are described together with new results of mass measurements. The developed theoretical methods for a study of molecular spectra, including methods of their global analysis and information systems of spectral databases, are presented.

$Research paper thumbnail of Two-parameter fracture criterion (K ρ,c -T ef,c ) based on notch fracture mechanics$

International Journal of Fracture, 2011

A two-parameter fracture criterion has been proposed to predict fracture conditions of notched co... more A two-parameter fracture criterion has been proposed to predict fracture conditions of notched components. This criterion includes the critical notch stress intensity factor K ρ,c , which represents fracture toughness of a material with a notch of radius ρ, and the effective T-stress. The effective T-stress T e f has been estimated as the average value of the T-stress distribution in the region ahead of the notch tip at the effective distance X e f. These parameters were derived from the volumetric method of notch fracture mechanics. The results of numerical T e f,c-stress estimation are compared to the T e f,c-stress results obtained from experimental analysis. The material failure curve or master curve K ρ,c = f T e f,c has been established as a result of the notched specimen tests. A large T e f,c range was covered from −0.80 σ Y to +0.19 σ Y using SENT, CT, RT (roman tile) and DCB specimens. It was shown that the notch fracture toughness is a linear decreasing func

The concept of the average stress has been employed to propose the maximum average tangential str... more The concept of the average stress has been employed to propose the maximum average tangential stress (MATS) criterion for predicting the direction of fracture angle. This criterion states that a crack grows when the maximum average tangential stress in the fracture process zone ahead of the crack tip reaches its critical value and the crack growth direction coincides with the direction of the maximum average tangential stress along a constant radius around the crack tip. The tangential stress is described by the singular and non-singular (T-stress) terms in the Williams series solution. The predicted directions of fracture angle are consistent with the experimental data for the mixed mode I/II crack growth behavior of Guiting limestone.

A B S T R A C T Three-dimensional elastic–plastic problems for a power-law hardening material are... more A B S T R A C T Three-dimensional elastic–plastic problems for a power-law hardening material are solved using the finite element method. Distributions of the J-integral in terms of the normalized elastic–plastic stress intensity factor and constraint parameter A along the crack front for varying the strain hardening exponent, specimen thickness and crack length are determined for edge cracked plate, centre cracked plate, three-point bend and compact tension specimens. The second parameter A in three-term elastic–plastic as-ymptotic expansion of the crack tip stress field is a measure of stress field deviation from the Hutchinson-Rice-Rosengren field and can be considered as a constraint parameter in elastic–plastic fracture. The loading levels cover conditions from small-scale to large-scale yielding. Results of finite element analyses show that the constraint parameter A significantly decreases when specimen thickness changes from 0.1 to 0.5 of the specimen width. Then, it has more or less stable value. Among four specimens, the highest constraint is demonstrated by the compact tension specimen that has the constraint parameter A lower than its small-scale yielding value.

$Research paper thumbnail of Determination of fracture mechanics parameters by measurements of local displacements due to crack length increment$

A B S T R A C T New experimental technique for a determination of the stress intensity factor and... more A B S T R A C T New experimental technique for a determination of the stress intensity factor and the non-singular T-stress is developed, verified and implemented. The approach is based on combining the crack compliance method and optical interferometric measurements of local deformation response on small crack length increment. Initial experimental information has a form of in-plane displacement component values, which are measured by electronic speckle-pattern interferometry at some specific points located near a crack tip. The first four coefficients of Williams' series are derived. A determination of initial experimental data at the nearest vicinity of crack/notch tip is the main feature of the developed approach. In this case, it is not necessary to use complex numerical models, which are connected with geometrical parameters and loading conditions of the object under study in a stage of experimental data interpretation. Moreover, an availability of high-quality interference fringe patterns, which are free from rigid body motions, serves as a reliable indicator of real stress state in the vicinity of the crack tip. Experimental verification of the proposed method is performed for specially designed specimen of double cantilever beam type. Distributions of the stress intensity factor and the T-stress for two cracks in different residual stress fields in the vicinity of friction stir welding joints are presented as an example. a nÀ1 , a n , a n+1 = crack length A n (n = 1, 2, 3, 4) = coefficients of Williams infinite series d ξ = in-plane displacement component in ξ-direction E = Young's modulus K I = stress intensity factor (SIF) in mode I n À 1, n, n + 1 = points of crack tip position N = absolute fringe orders T = T-stress value r, θ = radial and angular distance from the crack tip, respectively U n (r, θ), V n (r, θ) = differences in absolute values of in-plane displacement components for cracks of length a n and a nÀ1 u n , v n = absolute values of in-plane displacement component in x-direction and y-direction, respectively, for a crack of a n length x, y = coordinate axis directed along and normally to the crack line, respectively Δa nÀ1 , Δa n , Δa n+1 = crack length increment ΔN nÀ1 , ΔN nÀ0.5 = relative fringe orders Δ N (v) = total crack opening Δv nÀ1 , Δv nÀ0.5 = crack opening λ = wavelength of laser illumination μ = Poisson's ratio Ψ = sensitivity angle of speckle interferometer

A B S T R A C T Full-field three-dimensional (3D) numerical analyses was performed to determine i... more A B S T R A C T Full-field three-dimensional (3D) numerical analyses was performed to determine in-plane and out-of-plane constraint effect on crack-front stress fields under creep conditions of finite thickness boundary layer models and different specimen geometries. Several parameters are used to characterize constraint effects including the non-singular T-stresses, the local triaxiality parameter, the T z-factor of the stress-state in a 3D cracked body and the second-order-term amplitude factor. The constraint parameters are determined for centre-cracked plate, three-point bend specimen and compact tension specimen. Discrepancies in constraint parameter distribution on the line of crack extension and along crack front depending on the thickness of the specimens have been observed under different loading conditions of creeping power law hardening material for various configurations of specimens. Keywords crack-front stress fields; creep; in-plane and out-of-plane constraint parameters. N O M E N C L A T U R E a = crack length A 1 , A 2 = amplitude factors b = thickness E = Young's modulus h = local triaxiality parameter K 1 = stress intensity factor n = creep exponent J = J-integral ¯ t = normalized time of loading T, T zz = non-singular T-stresses T z = dimensionless constraint factor ν = Poisson's ratio σ xx , σ yy , σ zz = stress tensor components σ y = yield stress

Features of an experimental method and numerical modeling for determination of the edge-chipping ... more Features of an experimental method and numerical modeling for determination of the edge-chipping resistance of glass and ceramics using a conical diamond Rockwell indenter (with a tip radius of 200 lm) are presented. The ANSYS finite-element modeling of fracture resistance tests on such brittle materials at meso scale level is discussed. The three-dimensional static nonlinear contact problem for a Rockwell indenter impressed into a deformable solid body is solved. Fracture of the materials under such mechanical loading are studied through a numerical analysis of the transformation of the displacement, strain and stress fields depending on test parameters. It is shown that correct test data can be obtained if the indenter is impressed into the specimen within the zone of the edge effect. If the ceramic material is similar to the model material of linear elastic mechanics, it is reasonable to limit the distance between the edge of the specimen and the load application point to 300 lm.

This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright a b s t r a c t The concept of the T-stress as a local constraint factor has been extended to U-notch tip stress distribution as the effective T-stress. The effective T-stress has been estimated as the average value of the T-stress in the region corresponding to the effective (characteristic) distance ahead of the notch tip. The T-stress is evaluated by finite element method using the experimental load for crack initiation and computing the difference between principal stresses along ligament. A large range of critical effective T-stress values is investigated for different specimen configurations and notch aspect ratios. Crack stabilisation and crack bifurcation for fracture emanating from notches according to the critical effective T-stress is discussed. A model involving the influence of the critical effective T-stress on void growth for ductile failure in the vicinity of the notch tip has been proposed.

Procedia Engineering, 2011

The effect of hydrogen on the material failure curves of APL 5L gas pipe steels was analysed from... more The effect of hydrogen on the material failure curves of APL 5L gas pipe steels was analysed from viewpoint of the notch fracture mechanics. The material failure curves based on two-parameter fracture criterion have been determined for API 5L X52, X70 and X100 gas pipe steels. The notch fracture toughness c K , and the effective T-stress were employed to describe the material failure curve. Tests were carried out on electrolytic hydrogen charged SENT, CT, RT (Roman Tile) and DCB specimens with a notch. Fracture initiation was detected by acoustic emission. Material failure curves for hydrogen charged steels and steels without hydrogen were constructed. It was shown that there is critical hydrogen concentration, which causes significant reduction of local fracture resistance of pipe steels. Procedia Engineering 10 (2011) 942-947 T , has been successfully used to quantify the constraints of notch tip fields for various proposed geometry and loading configurations [5]. We suggest extending the curve of c ef c T f K , , for different steels charging by hydrogen. The results of test for the different specimens geometries with the notch aspect ratio a/t = 0.5 are presented for the case of electrolytic hydrogen charging during 30 days and compared with the results of initial state of the steels. The experimental assessment points ( c ef c T K , , , ) for four specimen geometries (CT, SENT, RT and DCB) of APL X52 steel are summarized in Fig.3. These experimental assessment points allow c ef c T K , , ) based on notch fracture mechanics. Int J Fracture 2011; 167: 173-182.

$Research paper thumbnail of Contact interaction and fracture of the surface layer during rolling friction and wedging$

Journal of Machinery Manufacture and Reliability, 2009

The results of physical and mathematical simulation and fracture of the cracked surface layer dur... more The results of physical and mathematical simulation and fracture of the cracked surface layer during rolling friction and wedging are presented. The simulation is performed with the Lagrangian method of finite elements using the software package ANSYS with the LS-DYNA problem solver. The regularities of elastoplastic deformation, fracture, and wear rate of the surface layer during contact interaction in rolling friction are analyzed.

Computational Materials Science, 2007

In the last four decades several theoretical models have been developed to diagnose the DHC veloc... more In the last four decades several theoretical models have been developed to diagnose the DHC velocity in zirconium alloys. However, majority of the known models ignore a dependence of the crack-tip hydrides on stress intensity factor (SIF) and temperature. In this paper we first present the integrated model of DHC which combines two independent calculation models. The first calculation sub-model is designed to predict the critical characteristics of hydrides (their length and thickness) depending on both temperature and SIF. On this basis, the second calculation sub-model allows us to diagnose the DHC velocity. As a whole, the present model is based on the steadystate solution of diffusion equation, provides the improved description of the local stress in the process zone ahead of the crack and refines the location and critical characteristics of the crack-tip hydride platelets. To illustrate the efficacy of our model some of the recent experimental data are presented on DHC in Zr-2.5%Nb pressure tubes used in Canadian and Indian PHWR's (Pressurized Heavy Water Reactors).

Engineering Fracture Mechanics, 2010

The concept of the T-stress as a local constraint factor has been extended to U-notch tip stress ... more The concept of the T-stress as a local constraint factor has been extended to U-notch tip stress distribution as the effective T-stress. The effective T-stress has been estimated as the average value of the T-stress in the region corresponding to the effective (characteristic) distance ahead of the notch tip. The T-stress is evaluated by finite element method using the experimental load for crack initiation and computing the difference between principal stresses along ligament. A large range of critical effective T-stress values is investigated for different specimen configurations and notch aspect ratios. Crack stabilisation and crack bifurcation for fracture emanating from notches according to the critical effective T-stress is discussed. A model involving the influence of the critical effective T-stress on void growth for ductile failure in the vicinity of the notch tip has been proposed.