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1

Vrancea intermediate-depth focal mechanism catalog: a useful instrument for local and regional stress field estimation

Andreea Craiu, Marius Craiu, Marius Mihai, Florinela Manea Elena, Alexandru Marmureanu

Acta Geophysica

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2023

|

Vol. 71, no. 1

29--52

EN

The Vrancea seismic zone, located in the bend region of the South-Eastern Carpathians, is a unique area with both crustal and intermediate-depth seismic activity and is known as one of the most active seismic area in Europe. Moderate crustal seismicity is recorded all over the Carpathian region, but the far more intense activity occurs in a small subcrustal seismogenic volume beneath the SE‐bend of the Carpathian arc with about 20×50 km lateral and 110 km vertical extent (70–180 km depth). A unique slab geometry, likely preserved until the present, causes stress localization due to the slab bending and subsequent stress release resulting in large mantle earthquakes in the region. The main focus of this study is to determine the focal mechanisms for events with a magnitude larger than 2.7, between 2005 and 2020 and evaluate the current stress field along the Vrancea subcrustal region, from the derived fault plane solutions. The main style of faulting for Vrancea subcrustal events presents a predominant reverse one, with two main earthquakes categories: the first one with the nodal planes, oriented NE–SW parallel with the Carpathian Arc and the second one with the nodal planes, oriented NW–SE perpendicular on the Carpathian Arc. The results of stress inversion indicate a dominant thrust faulting style, with an average stress regime index of 2.87. The stress pattern shows similar partitioning with vertical extension in the slab and no preferred orientation in the overlying crust, showing a transition regime from the extensional regime in the Moesian Platform to the compressional regime in the Vrancea subcrustal zone.

2

Analysis of temperature-field and stress-field of steel plate concrete composite shear wall in early stage of construction

Sun Yun, Guo Yaojie

Archives of Civil Engineering

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2021

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Vol. 67, nr 1

351--366

EN

To study the influence of temperature field and stress field on the cracking of the small thickness steel plate concrete composite shear wall (SPCW) in the early stage of construction. The temperature field and stress field of a 400 mm thickness SPCW was monitored and simulated through experimental research and numerical simulation. Moreover, a series of parameter analyses were carried out by using ANSYS to investigate the distribution of temperature field and stress field of SPCW. Based on the analysis results, some suggestions are put forward for controlling the cracking of SPCW in the early stage of construction. The results show that the temperature stress of 400 mm thickness SPCW in the early stage of construction is small, and there is no crack on the wall surface. For SPCW with thickness less than 800mm, the temperature stress caused by hydration heat in the early stage of construction is small, and the wall will not crack. The parameters such as wall thickness, steel plate thickness, boundary condition and stud space significantly influence the temperature field and stress field distribution of the small thickness SPCW in the early stage of construction, and reasonable maintenance measures can avoid cracking.

3

Stress feld estimation by the geoid undulations of the Samos Kuşadası Bay and implications for seismogenic behavior

Oruç Bülent, Balkan Emir

Acta Geophysica

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2021

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Vol. 69, no. 3

1137--1149

EN

The strong earthquake with magnitude 6.9 occurred ofshore at the northernmost edge of the Samos Island and was strongly felt in the north Aegean islands and İzmir metropolitan city. In this study, the effective elastic thicknesses of the lithosphere and seismogenic layer thickness were correlated with each other in order to understand the nature of the earthquakes. We determined that the upper and lower depth limits of seismogenic layer are in a range of 5–15 km, meaning that only the upper crust is mostly involved in earthquakes in the study area. The fact that seismogenic layer and effective elastic thicknesses are close to each other indicates that the earthquake potential may be within the seismogenic layer. Following that, we estimate the stress feld from the geoid undulations as a proxy of gravity potential energy in order to analyze the amplitude and orientation of the stress vectors and seismogenic behavior implications. The discrete wavelet transform has been carried out to decompose the isostatic residual gravity anomalies into horizontal, vertical and diagonal detail coefcients. The results delineated edges of gravity anomalies that reveal some previously unknown features.

4

The characterization of the stress fields near a crack tip for a compact specimen for elastic-plastic materials dominated by the plane strain state

Graba M.

International Journal of Applied Mechanics and Engineering

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2019

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Vol. 24, no. 3

549--576

EN

The paper presents a comprehensive analysis of the stress field near a crack tip for a compact specimen dominated by the plane strain state using the finite element method. The analysis also includes the calculation of some parameters of in-plane constraints, both for small and large strain assumptions. It discusses the influence of the material characteristic, relative crack length and external load for the stress field, and the in-plane constraint parameter. The approximation formulas for some in-plane constraint parameters are presented.

5

Geomechanical modeling as a basic step in secondary reservoir stimulation treatment design

Słota-Valim M., Jędrzejowska-Tyczkowska H.

Nafta-Gaz

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2017

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R. 73, nr 1

3--13

EN

Unconventional reservoirs require a new approach at every level of the operation on the object, starting from exploration of reservoir formation, through well and drilling design and ending with well completion including reservoir development. Due to the specific nature of unconventional reservoir properties, the hydrocarbons bearing formation requires stimulation treatments like hydraulic fracturing, aiming to improve the pores connectivity and enabling the free flow of the gas into the well bore, which in the end brings production rates to economic levels. In the paper a geomechanical model of the synthetic object, allowing the analysis of many processes accompanying real hydrocarbons exploitation was presented. Special attention was paid to the demonstration of changes in the state of stress in the geological formation, due to the exploitation of hydrocarbons and the influence of the initial horizontal stresses relationship (σH/σh), on the effectiveness of stimulation treatments in unconventional formations.

PL

Formacje złożowe o charakterze niekonwencjonalnym do poprawy właściwości transportowych i uzyskania eksploatacji na poziomie uzasadnionym ekonomicznie wymagają stymulacji poprzez szczelinowanie hydrauliczne, którego efektywność uzależniona jest od panujących warunków mechanicznych, m.in. właściwości sprężystych szczelinowanego ośrodka i oddziałującego pola naprężeń. W pracy przedstawiono i omówiono wyniki modelowania geomechanicznego obiektu syntetycznego, pozwalającego na analizę wielu procesów towarzyszących wydobyciu węglowodorów. Specjalną uwagę poświęcono zmianom w rozkładzie naprężeń w górotworze będących skutkiem eksploatacji oraz wpływowi początkowego układu naprężeń poziomych na efektywność zabiegów udostępnienia niekonwencjonalnej formacji złożowej.

6

Thermodynamic study on complex parts of the sphere and ellipsoid of a nuclear explosive device

Zhenzhi G., Bin H., Guilin Y.

Archives of Thermodynamics

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2016

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Vol. 37, no. 4

89--103

EN

Because the heat release of plutonium material, the composite structure is heated and the stress and strain of the composite structure will increase, which will affect the thermodynamic properties of the structure. The thermodynamic analysis of complex structures, which are composed of concentric structures of plutonium, beryllium, tungsten, explosives, and steel, was carried out. The results showed that when the structure is spherical, the temperature is higher than that of the ellipsoid structure. Stress of the elliptical structure is greater than the spherical structure. This study showed that the more flat the shell is, the greater the stress concentration point occurs at the long axis, and the maximum stress occurs at the beryllium layer. These conclusions provide theoretical support for the plutonium composite component testing.

7

Charakterystyka pól naprężeń przed wierzchołkiem pęknięcia dla kwadratowej płyty poddanej dwuosiowemu rozciąganiu

Grabania M.

TTS Technika Transportu Szynowego

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2015

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R. 22, nr 12

585--592, CD

PL

W artykule przedstawiona została charakterystyka pól naprężeń przed wierzchołkiem pęknięcia dla kwadratowej płyty zawierającej centralne pęknięcie, poddanej dwuosiowemu rozciąganiu. Praca prezentuje szczegóły obliczeń numerycznych, a także porównania stanów naprężeń dla płyt poddanych jednoosiowemu rozciąganiu oraz płyt poddawanych dwuosiowemu rozciąganiu. Analiza numeryczna prowadzona jest dla szeregu modeli materiałów sprężysto-plastycznych oraz różnych względnych długości pęknięcia. Dyskusja dotyczy wpływu geometrii, poziomu i rodzaju obciążenia zewnętrznego oraz charakterystyki materiałowej na pole naprężeń przed wierzchołkiem pęknięcia.

EN

In the paper the stress field near front of crack for center cracked square plate in biaxial tension was pre-sented. The paper presents the details of numerical calculations, and also the comparison of states of stress for plates subjected to uniaxial tensile and plates to be in biaxial tension. The influence of the crack length, material characteristic and the level or type of external load were discussed.

8

Stress-strain state of elastic plate with an arbitrary smooth notch

Kuz I., Kuz O., Sulym H.

Acta Mechanica et Automatica

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2015

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Vol. 9, no. 4

241--244

EN

The paper contains comparing calculations of the stress fields in an elastic plate with notch along the arc of a circle, ellipse or parabola obtained by analytic method based on complex Kolosov-Muskhelishvili potentials and by numerical variation-difference method. These fields differ by no more than 2%, which, in particular, indicates the reliability of such numerical implementation. This discrepancy can be explained by the fact that in the analytical solution domain is unbounded, while the numerical calculation was carried out, obviously, for a finite field. The given stresses at the top of the notch along the arc of an ellipse or a parabola significantly increase with increasing of the relative depth of the notch (while increasing its depth or decreasing width).

9

Nonlinear motion law of coalbed gas seepage under the combined effects of stress field and temperature field

Li B., Wei J., Li P., Wang K., Borisyuk Y. A.

Journal of Power Technologies

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2014

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Vol. 94, nr 2

106--113

EN

The shrinkage and swelling of the coal matrix due to the effects of temperature were investigated through the performance by Henan Province Key Lab of Gas Geology & Gas Control of a permeability test of loaded coal under various temperature and working conditions using its own seepage equipment for thermo-fluid-solid-mechanical coupling of methane-containing coal. The variation of coal permeability under the combined effects of stress and temperature was investigated, and the gas motion law in the coal samples was tested. The variation equations of coal permeability under the combined effects of stress and temperature, as well as the motion equations describing the nonlinear gas seepage law in coal seams were established. The established equations were proved to fit well with the experimental data, which demonstrated that the motion equations and the research methods were both reasonable. Study on the seepage nonlinear motion law of gas in the coal seam is great significance to mineral gas extraction.

10

Stresses and Displacements in an Elliptically Perforated Circular Disc Under Radial Pressure

Markides Ch. F., Kourkoulis S. K.

Engineering Transactions

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2014

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Vol. 62, iss. 2

131--169

EN

The complex potentials governing the elastic equilibrium of a finite circular disc, elliptically perforated at its center, are obtained using Muskhelishvili’s formulation. The disc is subjected to non-uniform distribution of pressure along two symmetric finite arcs of its periphery. Given the complex potentials, the stress- and displacement-fields can be determined everywhere on the disc by introducing a novel flexible interpretation of the conformal mapping, suitably adjusted to the computational process. The results of this procedure are given for various strategic loci and are critically discussed. The length of the loaded arc is considered similar to that obtained from the solution of the intact disc-circular jaw elastic contact problem assuming that the disc is compressed between the steel jaws of the device suggested by the International Society for Rock Mechanics for the implementation of the Brazilian-disc test. Concerning the distribution of the externally induced pressure along the loaded arcs, it is proven that for the general asymmetric configuration (i.e. the axes of the elliptical hole are neither parallel nor normal to the loading axis) the induced asymmetric displacement field does not permit maintenance of equilibrium of the disc as a whole in case the disc is considered exclusively under a distribution of radial pressure: Additional tractions must be exerted along the loaded arcs, obviously in the form of frictional stresses. Besides, providing full-field, analytic expressions for stresses and displacements, the main advantage of the present solution is that, by properly choosing the ratio of the ellipse’s semi-axes, the solution of three additional configurations, of major importance in engineering praxis, are obtained: These of the intact disc, the circular ring and the cracked disc.

11

A semi-analytical solution on static analysis of circular plate exposed to non-uniform axisymmetric transverse loading resting on Winkler elastic foundation

Abbasi S., Farhatnia F., Jazi S. R.

Archives of Civil and Mechanical Engineering

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2014

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Vol. 14, no. 3

476--488

EN

This paper is concerned with static analysis of functionally graded (FG) circular plates resting on Winkler elastic foundation. The material properties vary across the thickness direction so the power-law distribution is used to describe the constituent components. The differential transforms method (DTM) is utilized to solve the governing differential equations of bending of the thin circular plate under various boundary conditions. By employing this solution method, governing differential equations are transformed into recurrence relations and boundary/regularity conditions are changed into algebraic equations. In this study, the plate is subjected to uniform/non-uniform transverse load in two cases of boundary conditions (clamped and simply-supported). Some numerical examples are presented to show the influence of functionally graded variation, different elastic foundation modulus, and variation of the symmetrical transverse loads on the stress and displacement fields. Based on the results, the obtained out-plane displacement coincide with the available solution for a homogenous circular plate. It can be concluded that the applied method provides accurate results and it is easily used for static analysis of circular plates on an elastic foundation.

12

Numerical Verification of the Relationship Between The “In-Plane Geometric Con-Straints” used in Fracture Mechanics Problems

Graba M.

Acta Mechanica et Automatica

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2012

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Vol. 6, no. 2

38-47

EN

In the paper, numerical verification and catalogue of the numerical solutions based on Modify Boundary Layer Approach to determine the relationship between Q-stress and T-stress are presented. Based on the method proposed by Larsson and Carlsson, the Q-stress value are calculated for some elastic-plastic materials for different value of T-stress and external load expressed by J-integral. The influence of the external load, T-stress value and material properties on Q-stress value were tested. Such catalogue may be useful during solving the engineering problems, especially while is needed to determine real fracture toughness with including the geometric constraints, what was proposed in FITNET procedures.

13

Numeryczna analiza pola naprężeń oraz dynamiki rozwoju szczeliny zmęczeniowej w turbinie silnika lotniczego poddanej działaniu złożonego obciążenia termo-mechanicznego

Witek L.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2011

|

z. 99

129-131

EN

This paper presents results of the numerical stress and fracture analysis of the turbine disc. Using the finite element method, the stress state, J-integral and stress intensity factor were obtained for the disc rotated with the operational speed.

14

Modelowanie procesu zmęczenia cieplno-mechanicznego

Okrajni J.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

|

2011

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z. 99

123-125

EN

The main purpose of the work is the method of the description of the thermo-mechanical fatigue process of power plant components working under mechanical and thermal loading. The work focuses on the chosen component strain- stress characteristics. The FEM modelling has been used to describe the local stress- strain behaviour of the chosen power plant element. The calculations of stress distribution on the component surface show that the internal pressure induces considerably smaller values of stresses and strains in comparison with the same stresses specified for thermal loads. Thus, thermal impacts are responsible for cracks initiation and growth in areas of the greatest intensity of damage accumulation. The presented analysis is the part of the complex investigation method which main purpose is increasing the accuracy of the TMF process description and thermo-mechanical life assessment. In such situation the industrial investigations curried out in the work give the model approach and data for the comparison the real behaviour with the predictions.

15

Numerical analysis of stress fields generated by quenching process

Bokota A., Domański T., Sowa L.

Archives of Foundry Engineering

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2011

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Vol. 11, iss. 2 spec.

13--18

EN

In work the presented numerical models of tool steel hardening processes take into account mechanical phenomena generated by thermal phenomena and phase transformations. In the model of mechanical phenomena, apart from thermal, plastic and structural strain, also transformations plasticity was taken into account. The stress and strain fields are obtained using the solution of the Finite Elements Method of the equilibrium equation in rate form. The thermophysical constants occurring in constitutive relation depend on temperature and phase composite. For determination of plastic strain the Huber-Misses condition with isotropic strengthening was applied whereas for determination of transformation plasticity a modified Leblond model was used. In order to evaluate the quality and usefulness of the presented models a numerical analysis of stresses and strains associated hardening process of a fang lathe of cone shaped made of tool steel was carried out.

PL

W pracy przedstawiono model numeryczny procesu hartowania stali narzędziowej, w którym uwzględniono zjawiska mechaniczne generowane zjawiskami cieplnymi i przemianami fazowymi. W modelu zjawisk mechanicznych uwzględniono oprócz odkształceń termicznych, plastycznych i strukturalnych - również odkształcenia transformacyjne. Pola naprężeń i odkształceń uzyskuje się z rozwiązania metodą elementów skończonych równań równowagi w formie prędkościowej. Stałe termofizyczne występujące w związkach konstytutywnych uzależniono od temperatury i składu fazowego. Do wyznaczania odkształceń plastycznych wykorzystano warunek Hubera-Misesa ze wzmocnieniem izotropowym, natomiast do wyznaczania odkształceń transformacyjnych zastosowano zmodyfikowany model Leblonda. W celu oceny jakości i przydatności prezentowanego modelu dokonano analizy numerycznej pól temperatury, udziałów fazowych, naprężeń i odkształceń towarzyszących procesowi hartowania kła tokarki ze stali narzędziowej.

16

Analiza pola temperatury, pola naprężeń i odkształceń w czasie obróbki cieplnej walców hutniczych

Malinowski Z., Cebo A.

Prace Naukowe Politechniki Warszawskiej. Mechanika

|

2009

|

z. 226

111-116

PL

W artykule przedstawiono wyniki obliczeń zmian pola temperatury i naprężeń cieplnych podczas obróbki cieplnej walca hutniczego o średnicy beczki 855 mm, wykonanego ze staliwa L200HNM. Pole temperatury wyznaczono z rozwiązania równania przewodzenia ciepła w całym cyklu nagrzewania i chłodzenia walca. Pole naprężeń wywołane zmianą pola temperatury i przemianami fazowymi wyznaczono z rozwiązania równań Prandtla-Reussa dla ciała sprężysto - plastycznego. Do określenia granicznych wartości naprężeń i odkształceń wykorzystano kryterium Rice i Tracy.

EN

The results of the evaluation of the temperature field and stress and strain field while heat treatment of the rolling mill rolls has been performed. The roll cylinder was made from the cast steel L200HM. The temperature field was calculated from the solution to the heat conduction equation in the whole heat treatment cycle. The stress field was calculated from the Prandtl - Reuss equation for the elastic - plastic body. To indicate the critical zones based on the stress and strain values, the Rice and Tracy criterion was used.

17

New results concerning the identification of neutral inhomogeneities in plane elasticity

Vasudevan M., Schiavone P.

Archives of Mechanics

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2006

|

Vol. 58, nr 1

45-58

EN

Using the concept of a spring-layer (imperfect) interface, we develop the series methods to determine the corresponding interface functions which ensure the (stress) neutrality of an elastic inhomogeneity. We assume that the inhomogeneity occupies a simply-connected domain with a regular boundary and that the inhomogeneity-matrix system is subjected to linear plane deformations. Of particular interest is the fact that the prescribed stress field inside the matrix is assumed to be non-uniform.

18

Algorithms of the method of statically admissible discontinuous stress fields (SADSF) - Part II

Bodaszewski W.

Engineering Transactions

|

2004

|

Vol. 52, iss.4

231-252

EN

In the paper, the author introduces the sets of conditions that create the algorithms of the functions on which one defines the boundary problems met in the search for discontinuous limit fields existing around isolated nodes. Among those, there are functions describing states of stress in the component homogeneous regions, the parameters of lines that separate these regions, and, first of all, the formulae for determining the domains based on the general conditions of existence. These formulae play a key role in numerical implementations of the method. The fields satisfying the Huber-Mises yield condition are of primary choice however, the derived relationships have a general meaning. To emphasise this fact one presents not only the areas of existence valid for the Huber-Mises condition, but also the areas obtained for several other yield conditions applicable to plastically homogeneous materials. The knowledge of the areas opens the possibility of developing the method of search for the fields that obey these conditions, and for algorithmizing this method. This could be applied even for the fields that are characterised by arbitrary, admissible states of stress. One also presents, basing on a mathematically complete set of conditions, typical formulations of problems concerning the fields around the nodes. One discusses the balance between the set of conditions and the unknowns, as well as the transformations into global systems connected with complex fields. One consequently applies parametrisation of the yield conditions, which not only reduces the number of unknowns and leads to simple, recursive forms of the formulae, but, first of all, makes it possible to find the formulae for generation of domains, without which numerical solution of the fields and algorithmization of the method would not be possible at all.

19

Main problems of neogeodynamics phenomena investigation and mapping

Karabanov A., Garetsky R., Aizberg R., Aronova T.

Technika Poszukiwań Geologicznych

|

2003

|

R. 42, nr 6

27-32

EN

The solution of the several problems of neogeodynamics phenomena investigation and mapping was one of the main tasks of the IGCP project No 346 "Neogeodynamics of Baltic Sea Depression and adjacent areas". Investigations performed for the project resulted in a series of international geodynamic maps showing vertical movements at the neotectonic stage, bottom part of Quaternary deposits, recent vertical movements, tectonic stress, epicenters of earthquakes, Moho discontinuity, neotectonic zoning and o on. Hence, the water surfaces of the Baltic Sea and the east part of the North Sea, the southern part of Scandinavia, the German-Polish Depression, the Central European block mountains and depressions, western part of the Russian Plain and, partly the Carpathians, were mapped. Despite of, that was done in traditional manner without any digitalization, the set of maps showing structure and its dynamics from the Quaternary capping down to the Moho surface fulfils requirements of the modern Information Technology, thus it may and can be computerized in follows of the GIS rules. That will enable authors to supplement project with the newest data, and restructure its visual appearance. In the attached presentation, authors review some problems of neogeodynamic researches in Belarus.

PL

Do rozwiązania szeregu problemów neogeodynamiki w projekcie International Geological Correlaction Programme, projekt 346 ustalano związki między zjawiskami powierzchniowymi, a głęboką strukturą litosfery, polem naprężeń, sejsmicznością oraz rozmieszczeniem aktywnych uskoków, które są przyczyną trzęsień ziemi. W tym celu wykonane zostały kompleksowo dla obszaru zlewni Bałtyku i obszarów przyległych mapy utworów powierzchniowych, oraz mapy wgłębne sięgające aż do powierzchni Moho. Mimo, iż opracowanie to byłe wykonane bez procedur dygitalizacji i wektoryzacji, to spełnia ono w swej formie wymagania nowoczesnych technik informacji. Dlatego byłoby wskazane zdygitalizowanie i zwektoryzowanie całego opracowania w manierze GIS w celu wprowadzenia uzupełnień oraz umożliwienia nowoczesnej wizualizacji wyników. W załączonej prezentacji graficznej, autorzy przedstawiają problematykę badań neogeodynamicznych na Białorusi.

20

Numerical and experimental analysis of stress field on the crack front zones

Kopecki H., Zacharzewski J.

Zeszyty Naukowe Politechniki Rzeszowskiej. Mechanika

|

2002

|

z. 58 [193]

155-162

EN

The paper presents experimental and numerical analysis of stress field in neighbourhood crack front for different configuration of crack in tension plate. Photo - elastic method and numerical analysis were used for specimens made by epoxy resin material.