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1

Stress evolution of rock breakages by a disc cutter assisted by pre-cuts

Liu Jie, Chen Wei, Liu Taoying, Peng Di

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 2

art. no. e115, 2023

EN

To study the rock breakage mechanism by constant cross-section cutters assisted by pre-cuts, the present study first performed small-scaled linear cutting tests on sandstone specimens containing pre-cuts. The laboratory tests indicate that the sufficiently large penetration, causing successful internal and surface crack incisions, is essential for large chip formation. In addition, the small pre-cut depth may fail to form large chips. The numerical results agree well with laboratory tests in fracture patterns. More importantly, the numerical analysis indicates that the increases in rolling force frequently result in stress concentrations. When the stresses concentrate to critical values, fracture propagation occurs. The fracture propagation causes stress dissipation and the decrease in rolling force. Thus, the relation between cutting load fluctuations and crack propagation is revealed. Moreover, the influence of penetration on crack propagation is analyzed. By analyzing the stress fields at typical peak points of the rolling force, the crack propagation direction is predicted, and the influence of pre-cut depth on fracture propagation is studied.

2

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

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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.

3

Experimental and theoretical study on the dynamic ejection process of a rock burst under a static load

Zheng Weiyu

Archives of Mining Sciences

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2021

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Vol. 66, no. 1

43--56

EN

As the duration of a rock burst is very short and the roadway is seriously damaged after the disaster, it is difficult to observe its characteristics. In order to obtain the dynamic characteristics of a rock burst, a modified uniaxial compression experiment, combined with a high-speed camera system is carried out and the process of a rock burst caused by a static load is simulated. Some significant results are obtained: 1) The velocity of ejected particles is between 2 m/s and 4 m/s. 2) The ratio of elastic energy to plastic energy is about five. 3) The duration from integrity to failure is between 20 ms and 40 ms. Furthermore, by analyzing the stress field in the sample with a numerical method and crack propagation model, the following conclusions can be made: 1) The kinetic energy of the ejected particles comes from the elastic energy released by itself. 2) The ratio of kinetic energy to elastic energy is between 6% and 15%. This can help understand the source and transfer of energy in a rock burst quantitatively.

4

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.

5

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.

6

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.

7

The influence of normal fault on initial state of stress in rock mass

Tajduś A., Cała M., Tajduś K.

Studia Geotechnica et Mechanica

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2016

|

Vol. 38, nr 1

109--120

EN

Determination of original state of stress in rock mass is a very difficult task for rock mechanics. Yet, original state of stress in rock mass has fundamental influence on secondary state of stress, which occurs in the vicinity of mining headings. This, in turn, is the cause of the occurrence of a number of mining hazards, i.e., seismic events, rock bursts, gas and rock outbursts, falls of roof. From experience, it is known that original state of stress depends a lot on tectonic disturbances, i.e., faults and folds. In the area of faults, a great number of seismic events occur, often of high energies. These seismic events, in many cases, are the cause of rock bursts and damage to the constructions located inside the rock mass and on the surface of the ground. To estimate the influence of fault existence on the disturbance of original state of stress in rock mass, numerical calculations were done by means of Finite Element Method. In the calculations, it was tried to determine the influence of different factors on state of stress, which occurs in the vicinity of a normal fault, i.e., the influence of normal fault inclination, deformability of rock mass, values of friction coefficient on the fault contact. Critical value of friction coefficient was also determined, when mutual dislocation of rock mass part separated by a fault is impossible. The obtained results enabled formulation of a number of conclusions, which are important in the context of seismic events and rock bursts in the area of faults.

8

Analiza numeryczna płyt z centralną szczeliną poddawanych dwuosiowemu rozciąganiu dla materiałów sprężysto-plastycznych

Graba M.

Mechanik

|

2016

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R. 89, nr 10

1234--1243

PL

Zaprezentowano wybrane wyniki analizy numerycznej płyt CCSP(BT) z centralnym pęknięciem poddawanych dwuosiowemu rozciąganiu. Przedstawiono szczegóły modelu numerycznego, wpływ poziomu dwuosiowości naprężeń rozciągających płytę na wartość całki J oraz rozkład naprężeń przed wierzchołkiem pęknięcia. Analizę prowadzono z założeniem małych i dużych odkształceń.

XX

Presented are selected results of numerical analysis for CCSP(BT) plates, containing a central crack subjected to biaxial tension. Details of the numerical analysis were presented and the discussion about the impact of the level of biaxial tension ratio on stress field near crack tip was done. The analysis was performed on the assumption of small and large deformations.

9

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.

10

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.

11

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).

12

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.

13

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.

14

Calculation of Stress-Strain State Elastic Plate with Notch of an Arbitrary Smooth Contour

Kuz I. S., Kuz O. N.

Journal of Applied Computer Science Methods

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2013

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Vol. 5 No. 1

29--46

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 analyticnumerical method based on complex Kolosov-Mushelishvili 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.

15

Modelowanie numeryczne pola naprężenia w górotworze naruszonym wielopokładową eksploatacją węgla kamiennego w warunkach silnego zagrożenia sejsmicznego

Pilecki Z.

Zeszyty Naukowe Instytutu Gospodarki Surowcami Mineralnymi i Energią PAN

|

2011

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nr 80

93-102

PL

Przedstawiono numeryczną dwuwymiarową symulację pola naprężenia wytworzonego w wyniku wielopokładowej eksploatacji węgla kamiennego, prowadzonej w trudnych warunkach zagrożenia sejsmicznego, w jednej z kopalń Górnośląskiego Zagłębia Węglowego. Obliczono wpływ projektowanej eksploatacji w dwóch wariantach na zmianę pola naprężenia w górotworze. Dokonaną eksploatację symulowano w kolejności chronologicznej, w okresach kwartalnych. Obliczenia przeprowadzono dla dwóch wybranych przekrojów geologicznych, w przybliżeniu prostopadłych do siebie. Przemieszczenia pionowe w modelu kontrolowano na podstawie wyników pomiarów geodezyjnych obniżenia powierzchni terenu. Obliczenia wykonano w ośrodku sprężysto-plastycznym z kryterium wytrzymałościowym Coulomba-Mohra za pomocą programu FLAC ver. 5.0. Generalnie, analiza numeryczna pokazała, że projektowana eksploatacja w zależności od wariantów w zróżnicowany sposób zmieniła pole naprężeń w analizowanej partii górotworu. Podkreślono, że duży wpływ na kształtowanie się zagrożenia sejsmicznego miały koncentracje naprężeń, zwłaszcza w strefie uskokowej, grubych warstwach skalnych i w rejonie krawędzi eksploatacyjnych.

EN

Numerical simulation of stress field influenced by multi-seam hard coal mining, in difficult geological and mining conditions, in one of the coal mine of Upper Silesian Basin has been presented. The changes of stress field in rock mass, as a result of up to date mining and planned mining in different variants, have been calculated. Simulation has been carried out for two geological cross-sections, perpendicular each other approximately, in direction of N-S and W-E. In the model, vertical displacements have been controlled by results of geodetic measurements of terrain surface subsidence. Calculation has been done in elastic-plastic medium with Mohr-Coulomb criterion with the help FLAC v. 5.0 system. These numerical analysis enables to estimate the influence of planned mining on stress field, and as well seismic threat. Generally, obtained results showed, that planned mining in analyzed variants may cause different stress changes, especially in fault zone, thick geological layers, and close to neighboring seam edges, and finally different seismic threat forming.

16

Numerical analysis of stress fields generated by quenching process

Bokota A., Domański T., Sowa L.

Archives of Foundry Engineering

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2011

|

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.

17

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.

18

Cenozoic dynamic evolution of the Polish Platform

Jarosiński M., Porawa P., Ziegler P. A.

Geological Quarterly

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2009

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Vol. 53, No 1

3-26

EN

The Cenozoic tectonic evolution of the Polish Platform reflects repeated changes in loading conditions at the Alpine–Carpathian and Arctic–North Atlantic margins of the European continent. After the Late Creta ceous–Paleocene main phase of the Mid-Polish Basinin - version, a second phase of limited uplift of the Mid-Polish Swell occurred during the Middle–Late Eocene. End Eocene and Early Oligocene subsidence of narrow grabens on the Fore-Sudetic Monocline was coeval with normal faulting in the East Alpine foredeep basin and the development of the Central European rift system. At the same time the Outer Carpathian flysch basins were rearranged, presumably in response to the build-up of compressional stresses at crustal levels, whilst subsidence and erosion patterns changed in the Carpathian Foreland from being dominated by the NW–SE trending Mid-Polish Swell to being controlled by the development of the W–E trending Meta-Carpathian Swell. At the end of the Oligocene the Fore-Sudetic graben system propagated into the area of the Trans-European Suture Zone and the Sudetes and remained active during the Early and Middle Miocene. This was paralleled by intensified subduction activity and thrusting of the Carpathians and the development of their flexural foredeep basin. A short early Sarmatian episode of basement in volving transpression along the SW margin of the Mid-Polish Swell correlates with the termination of north-directed nappe transport in the Outer Carpathians. This was followed by eastward migration of the subsidence centre of the Carpathian Foredeep Basin and the gradual termination of tectonic activity in the grabens of the Polish Lowlands. After a period of post-orogenic relaxation the present-day compressional stress regime built up during the Pliocene and Quaternary. Intensified ridge push forces exerted on the Arctic–North Atlantic passive margins contribute to this compressional stress field that is dominated by collision-related stresses reflecting continued indentation of the Adriatic Block. This sequence of events is interpreted in terms of changing tectonic loads in the Carpathians, Alps and at the NW passive margin of Europe. The complex and diachronous interaction of mechanically coupled and uncoupled plates along collision zones probably underlies the temporally varying response of the Carpathian Foreland that in addition was complicated by the heterogeneous structure of its lithosphere. Progressively increasing ridge push on the passive margin played a secondary role in the stress differentiation of the study area.

19

New results concerning the identification of neutral inhomogeneities in plane elasticity

Vasudevan M., Schiavone P.

Archives of Mechanics

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2006

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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.

20

Static failure load predictions under mixed mode loading with an implicit gradient formulation

Tovo R., Livieri P., Benvenuti E.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

|

2005

|

z. 82

211-218

EN

In this paper, a non-local equivalent stress is calculated by solving a second order differential equation of implicit type. The solution is obtained assuming a linear elastic constitutive behaviour and two different definitions of the equivalent stress as failure criteria. The static failure loads of notched PMMA specimens predicted through the present criterion are compared with experimental results taken from the literature.