Wyniki wyszukiwania - Biblioteka Nauki

1

Quantitative evaluation of the fracturing process of natural composite on example of the cortical part of bone

100%

Ranatowski M. , Ranatowski E.

Advances in Materials Science

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2005

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tom Vol. 5, nr 1-3

69--74

EN

Modelling of local failures of the natural composite - bone is based on the solution of a number of problems involving the interaction of macrocrack with voids, crazes and micro cracks in heterogeneous material. Base upon the concept of microcrack precursor nucleation, a micromechanics model is used to study the formation of near-tip microcracking and consequent toughening effects. ultimately it causes a redistribution of stresses in the near-tip stress field of the macrocrack and this can affect the stress intensity factor (SIF) CTOD and fracture toughness.

2

Relation between stress state and fracture resistance in mismatched weld joints

100%

Ratanowski E.

Journal of Polish CIMAC

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2011

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tom Vol. 6, no 3

261-268

EN

After formulating a simplified model of under- and overmatched welded joints an analysis was made of stress at interface for the cases of perpendicular and non - perpendicular orientation of the zones (soft layer and hard layer) relative to the load action direction under tension. Conclusions from the theoretical analysis form a basis to an assessment of effort and fracture of the mismatched welded joints. Conditions for producing brittle and ductile fracture in mismatched welded joints in relation to geometrical conditions of the layer (W), expressed by k, and the mechanical properties of the layer materials, W e R , 0 R and equivalent stresses H s , v s are established in further experiments.

3

Modelling of impulse load influence on the stress state of foam materials with positive and negative poisson’s ratio

100%

Sulym H. , Mikulich O. , Shvabyuk V.

Acta Mechanica et Automatica

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2020

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tom Vol. 14, no. 2

79--83

EN

The influence of impulse load applied for different duration on the distribution of normalised dynamic radial stresses in positive and negative Poisson’s ratio medium was investigated in this study. For solving the non-stationary problem in the case of plane deformation for structurally inhomogeneous materials, the model of Cosserat continuum was applied. This model enables accounting for the influence of shear-rotation deformation of micro-particles of the medium. In the framework of Cosserat elasticity, on applying the Fourier transforms for time variable and developing the boundary integral equation method, solving of the non-stationary problem reduces to the system of singular integral equations, where the components that determine the influence of shear-rotation deformations are selected. The numerical calculations were performed for the foam medium with positive and negative Poisson’s ratio for different values of time duration of impulse. Developed approach can be used to predict the mechanical behaviour of foam auxetic materials obtained at different values of a volumetric compression ratio under the action of time variable load based on analysis of the dis-tribution of radial stresses in foam medium.

4

Determination of stress state based on well logging data and laboratory easurements – a CBM well in the southeastern part of the Upper Silesian Coal Basin (Poland)

100%

Kępiński M.

Geology, Geophysics and Environment

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2020

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tom Vol. 46, no. 2

77--92

EN

The main objective of this study is to present calculation methods of horizontal stress profiles, taking into account the stress boundaries model, poro-elastic horizontal strain model and the effective stress ratio approach, using calibration with wellbore failure. The mechanical earth model (MEM) parameters from log measurements and well testing data were estimated for a well located in the southeastern part of the Upper Silesian Coal Basin. Log-derived horizontal stresses of the well are commonly treated as the final product of geomechanical modeling in oil and gas practices. A less popular method for estimating horizontal stresses is based on Kirsch equations juxtaposed with compressional and tensile failure observed on a micro-imager or six-arm caliper. Using this approach, horizontal stresses are determined based on the fact that when hoop stresses exceed the formation’s tensile strength, tensile fractures are created, and when those stresses exceed the compressive strength of the formation, breakouts can be identified. The advantage of this method is that it can be run without in situ stress measurements. The presented workflow is recommended every time there is an image log and dipole sonic measurement in the available dataset, both being necessary to observe the failure zones and MEM.

5

The stress state analysis of the high performance heat exchanger

100%

Łopata S. , Ocłoń P.

Czasopismo Techniczne. Mechanika

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2011

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tom R. 108, z. 4-M/2

359-368

EN

The paper presents the analysis of the stress state in the construction of the high performance heat exchanger with finned elliptical tubes. The thermal computations carried out using the control volume method are introduced and explained. The zones in the construction where the failure is the most probable are presented.

PL

W artykule przedstawiono metodykę oceny stanu wytężenia konstrukcji wysokosprawnego wymiennika ciepła z ożebrowanymi rurami eliptycznymi. Omówiono sposób obliczeń cieplnych z użyciem metody objętości skończonych oraz wskazano miejsca konstrukcji wysokosprawnego wymiennika ciepła, w których prawdopodobieństwo pęknięcia rurek na skutek przekroczenia naprężeń dopuszczalnych jest największe.

6

Dynamic stress concentration at the boundary of an incision at the plate under the action of weak shock waves

100%

Mikulich O. , Shvabyuk V. , Sulym H.

Acta Mechanica et Automatica

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2017

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tom Vol. 11, no. 3

217--221

EN

This paper proposes the novel technique for analysis of dynamic stress state of multi-connected infinite plates under the action of weak shock waves. For solution of the problem it uses the integral and discrete Fourier transforms. Calculation of transformed dynamic stresses at the incisions of plates is held using the boundary-integral equation method and the theory of complex variable functions. The numerical implementation of the developed algorithm is based on the method of mechanical quadratures and collocation technique. For calculation of originals of the dynamic stresses it uses modified discrete Fourier transform. The algorithm is effective in the analysis of the dynamic stress state of defective plates.

7

Anomalous drill-core parting in the sediments of the Upper Silesian basin

100%

Kožušníková A. , Fialová V. , Hoch I.

Annales Societatis Geologorum Poloniae

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2003

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tom Vol. 73, No 2

139-143

EN

Anomalous jointing of drillcores is sometimes observed in prospect boreholes in the Upper Silesian basin. The drillcore is jointed into discs, slices or porringers that are not resemblant to natural jointing. This occurs in various types of sediments, but especially in brittle rocks. Orientation of jointing planes is perpendicular to the borehole axis and does not depend on the distance from the front of the core run. Anomalous jointing reflects locally increased stress in the layer.

8

Stress states caused in chamber of reinforced concrete grain silo by non-centric emptying on large eccentricities

100%

Prusiel J. A. , Gierej K.

Studia Geotechnica et Mechanica

|

2018

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tom Vol. 40, nr 4

282--291

EN

The article presents the analysis of complex stress states in the concrete structure of grain silos, caused by non-centric emptying. The authors present a combination of loads from the pressure of bulk solid on the silo chamber according to Eurocode 1, Part 4 [11], which should be taken into account when emptying on large eccentricities in action assessment class 3 (AAC3) silos. For the example of a cylindrical wheat silo with a height of 25 m and a diameter of 10 m, the researchers carried out an analysis regarding the impact of the size of the eccentric discharge outlet on the distributions of forces and bending moments in a reinforced concrete wall.

9

Relation Structure - Fracture Resistance in Process of Estimate the Weldability of Low Alloy Steels: Part I

100%

Ratanowski E.

Advances in Materials Science

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2010

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tom Vol. 10, nr 4(26)

32-40

EN

The relationship between microstructure and mechanical properties of structural materials is still relevant problem in the theory of materials science and mechanical engineering. The question is how the macro-mechanical parameters can be derived from the microscale mechanisms taking into account local structural heterogeneities. Another question is how to make quantitative descriptions of the strength and toughness properties of welded joints made of non-matching weld metal. These problems are the objects of welding and mechanical investigation and they are related to estimation of weldability. The results of this study concern the evaluation stress state at interface of the under- and overmatched weld joints. After formulating a simplified model of under- and overmatched weld joints an analysis was made of stress at interface for the cases of perpendicular and non - perpendicular orientation of the zones (soft - layer and hard - layer) relative to the load action direction under tension.

10

Use of 3D printing technology in the aviation industry on an example of numerical experimental stress state analysis of unmanned aerial vehicle wing

88%

Święch Ł. , Bendarz A.

Journal of KONES

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2017

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tom Vol. 24, No. 4

327--334

EN

The article presents the results of static tests performed on the primary support structures of a TWISST-ter unmanned aircraft constructed using additive manufacturing techniques commonly known as 3D printing. The primary goal of the experiment was determining the material effort of the structure in order to assess the feasibility of such an engineering solution in terms of material mechanics. Considering the fact that the properties of 3D printed elements are not widely known, both destructive experimental methods and finite element methods were used. During the experimental trails, the ARAMIS deformation measurement system, based on digital three-dimensional image correlation, was used. The results of this experiment allowed for the calibration of the numerical model as achieving convergence with experimentally determined strain fields. This approach ensured the correctness of the numerical determined stress state. Based on the results of the study, the necessary design improvements were implemented and a general conclusion was formed regarding of the numerical analysis of structures made through 3D printing.

11

On the choice of thickness of the cement mantle in cemented hip arthroplasty

88%

Levadnyi I. , Awrejcewicz J. , Loskutov A. , Szymanowska O.

Journal of Theoretical and Applied Mechanics

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2017

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tom Vol. 55 nr 4

1235--1244

EN

Recommendations for the optimal thickness of the cement mantle in cemented hip arthroplasty are outlined based on the results obtained with the finite element method. The investigations show that distal femur cement thickness higher than 2 mm positively affects mechanical behaviour of the cement mantle and can be useful in reducing stress-strain levels in the distal part of the femur what leads to prevention of development of a stress-shielding effect. The results of the study can contribute to the success of long-term implants.

12

The influence of thermal stresses and strand bending on surface defects formation in continuously cast strands

88%

Hadała B. , Cebo-Rudnicka A. , Malinowski Z. , Gołdasz A.

Archives of Metallurgy and Materials

|

2011

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tom Vol. 56, iss. 2

367-377

EN

Improvement of slab surface quality is a very important goal in continues casting process of steel. It is closely coupled with casting line productivity and tendency to increase casting speed. In such a case rapid cooling of strand surface mast be employed. It results in thermal stresses development and formation of surface cracks if casting speed, cooling conditions or the arc of casting machine are not appropriate. The strain and stress fields in continuously cast strand have been determined based on the developed thermo-mechanical model and finite element software. It allowed to calculate variation of selected criterions integrals over the hole casting line starting from solidification process in the mould and ending at cutting section. Steady solution to heat transfer equation has been used to calculate strand temperature field. Mould temperature has been calculated from the three dimensional transient model. Finite element method has been employed to build steady and transient heat transfer models. Finite element solution accuracy to the temperature field has been improved. New algorithm of the solidification heat handling has been developed to stabilize a steady solution to the heat transport equation. Damageability of the strand has been evaluated based on four fracture criterions.

PL

Poprawa jakości powierzchni wlewka ciągłego jest jednym z głównych celów procesu ciągłego odlewania stali. Z drugiej strony ciągła potrzeba zwiększania wydajności linii produkcyjnej poprzez zwiększenie prędkości odlewania, wymaga bardziej intensywnego chłodzenia pasma. Rezultatem takich działań jest rozwój naprężeń cieplnych oraz tendencja do powstawania pęknięć powierzchniowych we wlewku ciągłym. Naprężenia i odkształcenia powstające w materiale określono przy użyciu modelu termomechanicznego z wykorzystaniem oprogramowania bazującego na metodzie elementów skończonych. Dzięki temu możliwym stało się wyznaczenie przebiegu zmian parametrów opisujących wybrane kryteria pękania na całej długości odlewanego pasma (od momentu krzepnięcia w krystalizatorze, aż do momentu odcinania pasma na wyjściu z maszyny COS). W opracowanym modelu wymiany ciepła pole temperatury w odlewanym paśmie wyznaczono przy pomocy stacjonarnego rozwiązania równania wymiany ciepła. Do obliczeń pola temperatury w krystalizatorze wykorzystano trójwymiarowy model niestacjonarny. W obu przypadkach w rozwiązaniu numerycznym zastosowano metodę elementów skończonych. Poprawę stabilności i dokładności rozwiązania pola temperatury uzyskano dzięki uwzględnieniu ciepła krzepnięcia. Podatność pasma na powstawanie defektów określono za pomocą wybranych kryteriów pękania.

13

Experimental and Numerical Stress State Assesment in Refill Friction Stir Spot Welding Joints

88%

Gadalińska E. , Kubit A. , Trzepieciński T. , Moneta G.

Fatigue of Aircraft Structures

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2021

|

tom Iss. 13

54--71

EN

Refill Friction Stir Spot Welding (RFSSW) is a technology used for joining solid materials that was developed in Germany in 2002 by GKSS-GmbH as a variant of the conventional friction stir spot welding (FSSW) [1]. In the RFSSW technology, the welding tool consists of a fixed outer part and rotating inner parts, which are called a pin and a sleeve. The tool for RFSSW is designed to plasticize the material of the parts to be joined by means of a rotary movement. The design of the tool allows independent vertical movement of both elements of the welding tool. This allows obtaining spot welds without creating holes that could weaken the structure. The main advantage of RFSSW is the potential for replacing the technologies that add weight to the structure or create discontinuities, such as joining with screws or rivets. Thus, RFSSW has great potential in the automotive, shipbuilding and aviation industries. Furthermore, the technology can be used to join different materials that could not be connected using other joining methods. The main objective of this work is to understand the physical and mechanical aspects of the RFSSW method - including the residual stress state inside the weld and around the joint. The results of the investigations can help to determine optimal parameters that could increase the strength and fatigue performance of the joint and to prove the significant advantage of RFSSW connections over other types of joints. The work assumes the correlation of two mutually complementary investigation methods: numerical analyses and experimental studies carried out with diffraction methods. The comparison between numerical and experimental results makes potentially possible the determination of degree of fatigue degradation of the material by observing the macroscopic stress state and the broadening of the diffraction peak width (FWHM), which is an indicator of the existence of micro-stress related to the dislocation density and grain size.

14

Numeryczna symulacja stanu naprężeń w rejonie szyjki zęba

88%

Kierklo A. , Tribiłło R. , Walendziuk A.

Zeszyty Naukowe Politechniki Białostockiej. Budownictwo

|

2006

|

tom Z. 27

101-108

PL

W pracy przedstawiono przykład rozwiązania biomechanicznych problemów w stomatologii przy użyciu efektywnych metod numerycznych. Wykorzystując dwuwymiarową analizę MES zbadano rozkład przyszyjkowych naprężeń w zębie przedtrzonowym poddanym obciążeniom od powierzchni zgryzowej. Stwierdzono, że ukośne siły zgryzowe przyłozone do różnych miejsc na guzku policzkowym generują w okolicy szyjki koncentracje dużych naprężeń rozciągających, które są bardzo niekorzystne dla twardych tkanek zęba. Powtarzające się zjawiska rozciągania struktur zębowych w okolicy szyjki mogą powodować zmęczenie, mikropęknięcia i uszkodzenie tkanek, prowadzące w efekcie do powstania ubytków abfrakcyjnych.

EN

This paper is concerned with an example of the solution of biomechanical problems in dentistry by using effective numerical methods. Two-dimensional finite element analysis was used with respect to the cervical stress patterns of the premolar tooth under occlusal loading. It was found that occusal oblique loads applied to the different places of buccal cusp generated cervical concentrations of high tensile stresses with are disadvantageous for teeth's hard tissues. Repeated stretching of dental structures near the fulcrum may cause fatique, microfractures and damage of them, with eventually leads to the abfraction.

15

Application of an equivalent truss model for determining the stress state in multi-phase materials with cellular automata method

88%

Staszczyk A. , Sawicki J.

Advances in Science and Technology. Research Journal

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2017

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tom Vol. 11, no 2

51--57

EN

The Cellular Automata represent a universal method of modelling and simulation. They enable the performance of calculations for even the most complex processes and phenomena. They are also used successfully in mechanical and material engineering. In this paper, the concept of application of the Cellular Automata method for simulating the behaviour of material under stress is presented. The proposed numerical algorithm created performs a number of calculations of local stress states in the structure of precipitation hardened material. The principle of its operation is based on the application of the equivalent truss model, which is often used in the optimisation and design of structures. In this paper, this model was used to simulate a system embodying a section of the material containing various phases with different mechanical properties.

16

Naprężenia rezydualne w brykiecie węglowym i ich wpływ na wielkość sorpcji ditlenku węgla

75%

Wierzbicki M. , Murzyn T.

Prace Instytutu Mechaniki Górotworu PAN

|

2015

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tom Vol. 17, no. 1-2

75--80

PL

Brykiety węglowe powstałe metodą prasowania bezlepiszczowego bywają wykorzystywane w eksperymentach naukowych jako substytut litego węgla. W przypadku eksperymentów wyrzutowych lub pomiarów filtracyjnych cenna staje się wiedza dotycząca stanu naprężenia w brykiecie pozostałego po brykietowaniu. Do oceny średniego naprężenia rezydualnego wykorzystano pomiar tensometryczny odkształcenia matrycy. Wykonanie pomiarów izoterm sorpcji ma brykietach z tego samego materiału przy różnych wielkościach naprężeń rezydualnych pozwoliło na wyznaczenie relacji pomiędzy stanem naprężenia a sorpcją ditlenku węgla. Naprężenie rezydualne rzędu 1 MPa ogranicza maksymalną sorpcję Langmuira o około 1%.

EN

Coal briquettes formed in the pressing processes without the use of binders are widely used in experimental research as substitutes of coal rock. In the case of experiments involving outbursts or filtration measurements, of particular importance is the state of stress in briquettes after the briquette-forming process. The assessment of residual stress is based on strain measurements of the matrix. Measurements of sorption isotherms on briquettes made from the same material and under variable levels of residual stress are used to establish the relationship between the state of stress and carbon dioxide sorption. It is found out that residual stresses of the order of 1 MPa limit the maximal Langmuir sorption by about 1%.

17

Stress state analysis in aspect of wellbore drilling direction

75%

Knez D.

Archives of Mining Sciences

|

2014

|

tom Vol. 59, no. 1

71--76

EN

Drilling directional wells challenges designers. Apart from known problems until now they face exact description of stress distribution in near wellbore region issue. Paper presents analysis of stress state taking into account drilling direction. The transposed in-situ stress state relative to the borehole coordinate system (Cartesian borehole coordinate system) and the total stress component at the borehole wall (cylindrical coordinate system) exhibits cyclic behaviour with respect to drilling direction of borehole. It allows to find optimal wellbore path.

PL

Wiercenie otworów kierunkowych stanowi duże wyzwanie dla projektantów. Poza problemami typowymi obecnie staja oni w obliczu zagadnienia dokładnego opisu rozkładu naprężeń w strefie przyotworowej. Artykuł przedstawia analizę stanu naprężeń w aspekcie kierunku wiercenia. Rozkład naprężeń transponowany do układu odniesienia związanego z otworem wiertniczym (kartezjański układ współrzędnych zgodny z kierunkiem otworu wiertniczego) oraz składowe naprężenia na ścianie otworu wiertniczego (w cylindrycznym układzie odniesienia) wykazują cykliczną zmienność zależną od kierunku wiercenia. Pozwala to na określenie optymalnej trajektorii osi otworu wiertniczego.

18

Wybrane aspekty identyfikacji stanu mechanicznego połączeń spajanych

75%

Ranatowski E.

Zeszyty Naukowe. Mechanika / Akademia Techniczno-Rolnicza w Bydgoszczy

|

1999

|

tom Z. 44 (221)

91-107

PL

W artykule przedstawiono relację: struktura - własności mechaniczne, dla heterogenicznych połączeń spajanych w oparciu o zmodyfikowane rozwiązanie Prandtla. Wykonano ocenę stanu naprężenia [sigma...] dla i, k = x, y w sąsiedztwie powierzchni kontaktowej dla stref o obniżonej i podwyższonej wytrzymałości. Dokonano również oceny parametru S[p], jako fizycznej miary deformacji i wytężenia niejednorodnego złącza oraz parametru K[w], jako skutku oddziaływania więzów mechanicznych. W dalszej kolejności wykorzystano parametr K[w] do oceny parametrów procesu pękania, określając delta[R] = delta[...].

EN

In this paper was presented the relation between structure and mechanical properties of the heterogenous weld joints with used a modified Prandtl solution. An analysis was made of stress sigma[sub ik], i k = x, y at interface for the cases of perpendicular and nonperpendicular orientation of the zones relative to the loda action under tension. Conclusion from stress analysis form a stress state parametr S[sub p] as a physical measure of the deformation and effort of the mismatched weld joint and constraint factor K[sub w]. Futhermore, form some basic for application of the constraint factor K[sub w], to an assessment of the fracture parametr delta[sub R] = delta[...].

19

Nowe zastosowania efektu Barkhausena do wyznaczania stanu naprężeń w warstwie wierzchniej odlewów i części maszyn

75%

Pomorski K. , Kubicki J. , Drotlew A.

Krzepnięcie Metali i Stopów

|

2000

|

tom R. 2, nr 44

515--520

PL

Praca dotyczy zastosowań efektu Barkhausena do identyfikacji stanu naprężeń w materiałach ferromagnetycznych. Opisano zasadę działania aparatury pomiarowej, oraz prototypowego urządzenia wyznaczającego kierunki naprężeń głównych. Przedstawiono wyniki badań rozkładu wartości skutecznej napięcia szumu Barkhausena dla pewnych aplikacji przemysłowych w układzie współrzędnych biegunowych, oraz omówiono możliwości jej zastosowania w metaloznawstwie.

EN

This paper concerns the adoptions of the Barkhausen's effect for the identification of stresses in ferromagnetic materials. The operational processes of the measuring apparatus and the action of the prototypical instrument, which calculates the directions of the predominant stresses, are presented below. The results of the investigations for the distribution of the RMS value of Barkhausen noise voltage for certain industrial applications are illustrated in the polar plot. The possibilities of the employment of this method in metallography are also described below.

20

Wpływ szerokości filara oporowego dla chodnika przyścianowego na stan naprężenia w jego otoczeniu

75%

Majcherczyk T. , Niedbalski Z. , Małkowski P.

Górnictwo i Geoinżynieria

|

2011

|

tom R. 35, z. 2

415-424

PL

W artykule przedstawiono analizę wpływu szerokości filara pozostawionego pomiędzy zrobami zawałowymi a chodnikiem przyścianowym wykonanym dla sąsiedniej ściany na zmianę stanu naprężenia i wytężenia. Dla zapewnienia funkcjonalności chodnika drążonego dla nowej ściany, przeanalizowano szerokości filara od 4 m do 10 m. Analizowany przypadek dotyczy konieczności określenia lokalizacji chodników przyścianowych dla zamykających ścian B-11 i B-11a w pokładzie 348. Warunki górniczo- geologiczne w opisywanym przypadku należy uznać za szczególnie trudne ze względu na duże nachylenie pokładu sięgające 240, znaczne zagrożenie metanowe oraz obustronne otoczenie ściany zrobami zawałowymi. Lokalizacja przedmiotowych wyrobisk uwzględnia warunki ekonomiczne i jednocześnie optymalną szerokość filara, która będzie zapewniać stateczność wyrobisk przyścianowych.

EN

The paper presents the analysis of the influence of support pillar width left between a goaf and a gate drifted for the consecutive longwall on the state of stress and strain. The widths of pillar from 4 m to 10 m were analyzed to ensure the gate functionality for the subsequent longwall panel. The case concerns the necessity of defining main gate locations which close the panel for longwalls B-11 and B-11a in the seam 348. The mining and geological conditions on the spot were found as exceptionally hard due to bed inclinations up to 240, methane hazard and goafs on both sides of the longwall panel. The location of the analyzed workings takes into consideration both the economic conditions and the optimal pillar width, which additionally ensure gate stability.