Wyniki wyszukiwania - BazTech

1

Nominal stress-based estimation of fatigue life of welded joints

Głowacka Karolina, Łagoda Tadeusz

Biuletyn Instytutu Spawalnictwa w Gliwicach

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2020

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Vol. 64, No. 2

39--44

EN

The paper presents methods for determining the fatigue life of welded joints with particular emphasis given to typical joints. In addition, the article presents various possible nominal stress-based ways enabling the calculation of stresses, including structural stresses and involving the most complex linear fracture mechanics. The paper also discusses recommendations by the International Institute of Welding related to the determination of the fatigue life of welded joints in flat elements exposed to tension-compression conditions. The work is focused on assessing the fatigue life of welded joints (selected types) in accordance with the guidelines specified in related recommendations issued by the International Institute of Welding and taking into consideration the analysis concerned with the safety of such structures.

PL

Przedstawiono metody wyznaczania trwałości zmęczeniowej złączy spawanych ze szczególnym uwzględnieniem typowych złączy. Podano możliwe sposoby wyznaczania naprężeń uzyskanych na drodze obliczeniowej w złączach spawanych na podstawie naprężeń nominalnych według różnych propozycji, poprzez naprężenia strukturalne, aż po zastosowanie najbardziej skomplikowanej liniowej mechaniki pękania. Na tym tle przedstawiono zalecenia Międzynarodowego Instytutu Spawalnictwa dotyczące wyznaczania trwałości zmęczeniowej złączy spawanych w warunkach rozciągania-ściskania elementów płaskich. Skupiono uwagę na problemie oceny trwałości zmęczeniowej połączeń spawanych wybranych typów złączy zgodnie z wytycznymi zawartymi w zaleceniach Międzynarodowego Instytutu Spawalnictwa oraz analizie bezpieczeństwa takich konstrukcji.

2

Coal permeability change caused by mining-induced stress

Zhang Lulu, Li Bo, Wei Jianping, Wen Zhihui, Ren Yongjie

Mining Science

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2019

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Vol. 26

203--222

EN

To study coal permeability evolution under the influence of mining actions, we conducted a sensitivity index test on permeability to determine the influence of axial and confining stresses on coal permeability. Loading and unloading tests were performed afterward, and the differences between loading and unloading paths in terms of strain and permeability were studied. A permeability evolution model was built in consideration of absorption swelling and effective stress during modeling. An effective stress calculation model was also built using axial and confining stresses. The calculation results of the two models were compared with experimental data. Results showed that permeability were more sensitive to confining stress than axial stress, and effective stress placed a large weight on confining stress. Large axial and radial deformations at peak strength were observed during unloading. In the unloading phase, the permeability of coal began to increase, and the increment was enhanced by large initial axial stress when confining stress was loaded. permeability sensitivity to axial and confining stresses were used to explain these permeability changes. The calculation results of the models fitted the experimental data well. Therefore, the proposed models can be used to calculate effective stress on the basis of axial and confining stresses and describe permeability change in coal under the influence of mining actions.

3

Predykcja ciśnień porowych w otworach wiertniczych przewiercających dolnopaleozoiczne formacje łupkowe basenu bałtyckiego – północna Polska

Słota-Valim M.

Nafta-Gaz

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2017

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R. 73, nr 4

219--226

PL

W niniejszej pracy przedstawiono wyniki analizy ciśnienia porowego przy wykorzystaniu powszechnie stosowanych w przemyśle naftowym metod predykcji ciśnienia porowego, dostępnych na platformie specjalistycznego oprogramowania. Analizę ciśnień porowych przeprowadzono w niemal pełnym interwale czterech otworów wiertniczych przewiercających perspektywiczny interwał łupków dolnego paleozoiku zdeponowanych w południowej części basenu bałtyckiego. Wyniki analizy pozwoliły na wskazanie poziomów o podniesionym ciśnieniu porowym, których przewiercanie może wiązać się z komplikacjami wiertniczymi, a nawet prowadzić do utraty stabilności ściany odwiertu.

EN

This paper presents the results of the pore pressure prediction conducted in almost the entire profile, of four boreholes, drilled through perspective intervals of the lower Paleozoic shales deposited in the southern part of the Baltic Basin. The Pore pressure prediction, was carried out with the use of Eaton and Bowers methods, which are commonly used methods in the oil and gas industry. The results of the analysis allowed to identify overpressure zones, which may lead to drilling complications and even wellbore instability issues.

4

Prognozowanie ciśnień porowych w ośrodku geologicznym z wykorzystaniem modułu Seismic Pore Pressure Modeling firmy WesternGeco

Wilk A.

Nafta-Gaz

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2016

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R. 72, nr 2

79--86

PL

Do obliczenia gradientu ciśnień porowych wykorzystano moduł Seismic Pore Pressure Modeling firmy WesternGeco, który został udostępniony autorowi na okres jednego miesiąca. Atutem wspomnianego modułu jest jego interaktywność oraz fakt, iż pracuje on w systemie Petrel firmy Schlumberger, będącym jednym z podstawowych narzędzi interpretacyjnych używanych przez polskie jednostki przemysłowe. Do obliczeń wykorzystano rzeczywiste pomiary ze zdjęcia sejsmicznego 3D z północnego obszaru Polski. Uzyskano zadowalające wyniki potwierdzające użyteczność tego narzędzia w pracach poszukiwawczych.

EN

Pore pressure gradient calculations were based on the module “Pore Pressure Seismic Modeling” of WesternGeco, which was made available to the author for a period of one month. The advantage of this module is its interactivity, and the fact that it works in the Schlumberger Petrel system, which is one of the basic tools of interpretation used by our native oil industry. For calculations, actual measurements of the 3D seismic survey of the northern Polish territory were used. Satisfactory results confirming the usefulness of this tool in exploration work was achieved.

5

Patient-specific hemodynamics and stress-strain state of cerebral aneurysms

Ivanov D., Dol A., Polienko A.

Acta of Bioengineering and Biomechanics

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2016

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Vol. 18, no. 2

9--17

EN

Purpose: Approximately 5% of the adult population has one or more cerebral aneurysm. Aneurysms are one of the most dangerous cerebral vascular pathologies. Aneurysm rupture leads to a subarachnoid hemorrhage with a very high mortality rate of 45–50%. Despite the high importance of this disease there are no criteria for assessing the probability of aneurysm rupture. Moreover, mechanisms of aneurysm development and rupture are not fully understood until now. Methods: Biomechanical and numerical computer simulations allow us to estimate the behavior of vessels in normal state and under pathological conditions as well as to make a prediction of their postoperative state. Biomechanical studies may help clinicians to find and investigate mechanical factors which are responsible for the initiation, growth and rupture of the cerebral aneurysms. Results: In this work, biomechanical and numerical modeling of healthy and pathological cerebral arteries was conducted. Patient-specific models of the basilar and posterior cerebral arteries and patient-specific boundary conditions at the inlet were used in numerical simulations. A comparative analysis of the three vascular wall models (rigid, perfectly elastic, hyperelastic) was performed. Blood flow and stress-strain state of the two posterior cerebral artery aneurysm models was compared. Conclusions: Numerical simulations revealed that hyperelastic material most adequately and realistically describes the behavior of the cerebral vascular walls. The size and shape of the aneurysm have a significant impact on the blood flow through the affected vessel and on the effective stress distribution in the aneurysm dome. It was shown that large aneurysm is more likely to rupture than small aneurysm.

6

A numerical comparative analysis of ChM and Fixion nails for diaphyseal femur fractures

Ivanov D., Barabash Y., Barabash A.

Acta of Bioengineering and Biomechanics

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2016

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Vol. 18, no. 3

73--81

EN

Purpose: Today intramedullary locked nails are widespread in treatment of diaphyseal long bone fractures of the lower limb. However, such nails have a number of drawbacks: complexity and duration of the installation, high axial stiffness, as well as the failure of locking screws and nail body. Expandable nails such as Fixion have several advantages over lockable ones. They can be quickly installed without the need of reaming and provide sufficient stabilization of the fracture. However, many studies show their low stability under torsional loads. Methods: In this paper, geometric characteristics of Fixion nail were investigated. Bone-nail systems (with Fixion and locked nail) under the influence of three types of loads were numerically studied. Two types of diaphyseal femoral fractures (type A and B in accordance with AO/ASIF classification) were examined. Results: It was revealed that Fixion nail provides axial stiffness of 489 N/mm for the fractures studied. Expandable nail showed higher compression at fragments junction than locked nail. Torsional stability of Fixion nail was also high. Corrosion was found on inner surface of Fixion nail. Conclusions: Fixion nail showed high stability under influence of the three loads studied. Corrosion on the internal wall of the nail may indicate its relatively low resistance to saline.

7

Gas seepage equations of the coal seam under the action of moisture and the stress field

Li B., Li P., Sun D. H., Zhang L. L., Wei C. F., Borisyuk Y. A.

Journal of Power Technologies

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2015

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Vol. 95, nr 4

250--257

EN

A seepage experiment was conducted in relation to a loaded coal mass with various moisture content and working conditions using self-developed tri-axial gas seepage equipment. A briquette sample was used as the research object. The change in the relationship of coal mass permeability under the combined action of moisture content and effective stress was studied experimentally. The relational function was established between coal mass permeability under this combined action and the seepage equation expressing gas migration in the coal seam. The research showed the following: (1) the moisture content of coal heavily influences effective permeability, as coal mass permeability decreases in a quadratic polynomial relationship with the increase of effective stress at constant moisture content; (2) at constant moisture content in the coal mass, coal mass permeability gradually declines in a negative exponent relationship with the increase of effective stress. Moreover, coal seam gas seepage equations under the combined action of moisture and stress field were put forward based on experimental results, the law of mass conversation and Darcy’slaw.

8

Stress and strain distribution in expanded coronary stents depending on applied material

Idziak-Jabłońska A.

Journal of Applied Mathematics and Computational Mechanics

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2015

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Vol. 14, nr 2

21--30

EN

The aim of the study is to present mechanical characteristics of coronary stents. More specifically, stress and plastic strain present in a stent were determined depending on the pressure applied to the internal surface of the stent. The study analyses a model of a slotted-tube stent using the finite element method. The stents with two different numbers of segments and with three wall thicknesses were dealt with. The analysis was carried out for the three most popular biomaterials: austenitic steel Cr-Ni-Mo, cobalt-matrix alloy Co-Cr-W-Ni and titanium-matrix alloy Ti-6Al-7Nb. Numerical analysis presented in the study provides a basis for further research and optimization of stent design. The calculations obtained in the study show that the lowest values of maximum reduced stress occur in the stent made of Cr-Ni-Mo. Furthermore, the stent made of Ti-6Al-7Nb exhibited the lowest values of plastic strain.

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

Inuence of Foam Filling on Dynamic Response of Hemispherical Shell Subjected to Blast Pressure

Świniarski J., Kowal-Michalska K., Niezgodziński T.

Mechanics and Mechanical Engineering

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2013

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Vol. 17, nr 2

177--186

EN

The paper aims to investigate the effect of aluminium foam filling of hemispherical steel shell on its dynamic response, accounting for the blast pressure modelling. The considered structures subjected to uniformly distributed pressure, rigidly connected with a steel plate, are considered. True material stress–strain curves for shell and foam filling are assumed in calculations. The problem is solved by FEM using ANSYS software. The time relations of strain energy and effective stresses for different simulations of blast pressure are determined and compared for steel shells and shells filled with aluminum foam.

11

Study of physico-chemical and mechanical characteristics of consolidated and unconsolidated cemented paste backfills

Yilmaz E., Belem T., Benzaazoua M.

Gospodarka Surowcami Mineralnymi

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2013

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T. 29, z. 1

81--100

PL

W ostatnich latach obserwuje się, że wydajność i jakość próbek zawiesin nasyconych cementem (CPB – Cement Paste Backfill) in situ są stale niższe niż tych samych próbek przygotowanych w plastikowych formach w laboratorium. Może to wynikać z braku w laboratorium skutecznego narzędzia mogącego naśladować zawiesiny in situ, warunki ich utwardzania jak również rozmiary i geometrię próbek. W celu wypełnienia tej luki, w laboratorium opracowano nowe narzędzie o nazwie CUAPS (Curing Under Applied Pressure System), wytworzone i wykorzystane do zbadania wpływu ciśnienia na podstawie skutecznego nacisku na właściwości fizykochemiczne i mechaniczne CPB, jak również próbek otrzymanych z plastikowych form. Badania porównawcze przeprowadzono zarówno dla próbek CUAPS jak i próbek otrzymanych w laboratorium, zawierających lepiszcza (cementu) 3,45 i 7% wag. po 7, 14 i 28 dniach utwardzania. Wyniki wskazują, że wydajność próbek konsolidowanych CUAPS są zawsze bardziej prawdziwe (realistyczne) niż próbek otrzymanych w laboratorium, głównie z powodu odprowadzania wody w wyniku konsolidacji. Ostatecznie metoda CUAPS powoduje korzystny wpływ na utwardzenie CPB dzięki zawartości wody (separacja wody od świeżej zawiesiny odpadów z cementu) i połączeniu części wody zasobowej z zawiesiną w zrobach.

EN

In recent years, it has been observed that the performance and quality of in situ cemented paste backfill (CPB) samples are constantly lower than samples obtained from the same CPB mix poured into laboratory-prepared plastic moulds. This could be well explained by the absence of an efficient laboratory tool capable of mimicking CPB’s in situ placement, hardening, and curing conditions relating to stope size and geometry. To meet this need, a new laboratory tool named CUAPS (curing under applied pressure system) was manufactured and used to examine the effect of curing under effective stress on physico-chemical and mechanical properties of CPB, along with plastic mould samples. A comparative study was conducted for both CUAPS and mould samples containing a binder content of 3, 4.5, and 7 wt% after curing times of 7, 14, and 28 days. Results indicate that the performance of CUAPS-consolidated samples are always more realistic than those of plastic mould-unconsolidated samples mainly due to water drainage induced by consolidation. CUAPS has witnessed an advantageous effect on CPB hardening which includes the amount of bleeding water (separation of water from the fresh backfill material) and a combination of drainage of part of the mixing water and the settlement of paste backfill after its placement in the cap.

12

Wpływ sposobu zawodnienia na ciśnienie porowe i naprężenie efektywne w obliczeniach numerycznych programem FLAC 2D

Dyba M., Pilecki Z.

Przegląd Górniczy

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2012

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T. 68, nr 7

25--31

PL

W pracy analizuje się wpływ trzech wariantów zawodnienia ośrodka porowatego na wyniki obliczeń ciśnienia porowego i naprężenia efektywnego. Obliczenia zostały przeprowadzone dla sprzężonych procesów hydraulicznego i mechanicznego w tzw. podstawowym schemacie przepływu (basic flow scheme-single phase) programu FLAC 2D w wersji 5.0. Zawadniano dwuwarstwowy ośrodek składający się z dolnej warstwy nieprzepuszczalnej i górnej przepuszczalnej do głębokości 1,5 m. Analizowano zmiany ciśnienia porowego i naprężeniaefektywnego na podstawie przekrojów izoliniowych wytworzonego pola oraz wykresów zmian w punktach referencyjnych na profilach poziomym i pionowym. Wyniki obliczeń pokazały, że dla analizy ośrodków wielowarstwowych z różnym gradientem przepuszczalności najbardziej korzystny jest wariant deklaracji „ciśnienia porowego” (pore pressure), zarówno pod względem efektów obliczeń jak również czasu obliczeniowego. Wariant deklaracji ustalonego poziomu wody gruntowej (water table) może znaleźć zastosowanie w opisie pola ciśnienia porowego odpowiadającemu ciśnieniu słupa wody. Obliczenia można prowadzić w ośrodku jednowarstwowym o stosunkowo dobrej przepuszczalności lub wielowarstwowym, w którym gradient przepuszczalności nie tworzy bariery dla przepływu wody. Wariant deklaracji „linii zasilania” (apply pp) może się sprawdzać w warunkach nasycenia modelu do granicy deklarowanego zasilania, lecz dużym ograniczeniem jest wydłużony czas obliczeniowy.

EN

In the work the influence of three variants of watering of the porous medium on the calculation results of pore pressure and effective stress have been analyzed. The numerical calculations have been carried out for coupled hydromechanical processes in the so-called basic flow scheme-single phase of the FLAC 2D programme in the version 5.0. A two-layer medium consisting of an impermeable lower layer and permeable upper layer was watered up to the depth of 1.5 m. The changes of pore pressure and effective stress have been analyzed on the basis of images of isolines sections and graphs constructed at monitoring points along vertical and horizontal profiles in the model. The results of calculations have shown that for the analysis of multilayer media with different gradient of permeability the most advantageous is the variant of “pore pressure” command, both in respect of calculation results and calculation time as well. The command water table can be applied in the description of the pore pressure field corresponding to the pressure of water column. The calculations can be carried out in a one-layer medium with relatively high permeability or in a multilayer medium, where the permeability gradient does not create a barrier for water flow. The command apply pp may find application in conditions of full saturation up to the border of the declared line of water supply, but it is limited by a long calculation time.

13

Elasto-plastic model of unsaturated soil

Fedczuk P.

AGH Journal of Mining and Geoengineering

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2012

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Vol. 36, no. 2

137-144

EN

The paper presents the concept of an elasto-plastic model for partially saturated soil. Elastic properties are described by the classical elastic rule, taking into consideration the effective stresses. Plastic properties are defined by extension of the critical state theory which also takes the suction effect into consideration. The behaviour of soil is described by the extended incremental elasto-plastic constitutive relation (in form "effective stress - strain and suction" relationship). The model operates the equation of the Wheeler and Sivakumar's plastic surface. The generalized hardening rule (for the changing value of suction) connects the increment of the plastic part of the void ratio with stress and suction levels.

PL

W pracy prezentuje się koncepcję sprężysto-plastycznego modelu częściowo nawodnionego gruntu. Sprężyste własności gruntu opisuje klasyczne równanie sprężystości, uwzględniającego efektywne naprężenia. Plastyczne własności definiuje rozwinięta teoria stanu krytycznego uwzględniająca efekt ssania. Zachowanie gruntu opisuje rozszerzone przyrostowe prawo sprężysto-plastyczności (w formie zależności "efektywne naprężenie - odkształcenie i ssanie"). Model operuje zmodyfikowanym równaniem powierzchni plastyczności Wheelera i Sivakumara. Uogólnione prawo wzmocnienia (dla zmiennej wartości ssania) wiąże przyrost plastycznej części wskaźnika porowatości z poziomem efektywnego naprężenia i ssania.

14

Increase of efficiency of the ECAP technology at grain refinement of the alloy AlMn1Cu

Rusz S., Malanik K., Kedron J.

Archives of Materials Science and Engineering

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2008

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Vol. 34, nr 1

52-56

EN

Purpose: The foundation of the resolved problem consists of verification of influence of temperature and also geometry of the ECAP tool on obtaining of required amount of deformation which substantially influences grain size. Research was realised with use of the alloy AlMn1Cu. Verification concerned influence of change or route of deformation on amount of deformation aimed at obtaining of required grain refinement. Design/methodology/approach: At the first stage of solution mathematical simulation was used for determination of conditions for obtaining the required amount of material deformation. Experimental part of the work was then made on the basis of results of the mathematical simulation. Findings: Route of deformation was changed by deflection of horizontal part of the ECAP channel by 10 and 20°. Obtained results were compared with conventional ECAP process without deflection of the channel. Increased efficiency of the ECAP process was confirmed unequivocally. Practical implications: Practical application of the obtained results at forming of the given alloy in the company AlInvest Bridlicna will bring economy of forming operations, as well as operations of heat treatment of that alloy. Originality/value: The obtained results will be verified by designing of new device enabling forming of strip of sheet. This type of alloy is used for production of strip of sheet by technology of successive rolling to the required thickness with required mechanical properties with preservation of the required formability.

15

Naprężenie efektywne w żeliwie o osnowie ferrytycznej

Piekło J., Maj M.

Transport Samochodowy

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2006

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z. 3

117--130

PL

W artykule opisano zagadnienie wyznaczenia naprężeń efektywnych σef w osnowie żeliwa ferrytycznego na podstawie zaproponowanego modelu obliczeniowego. Wyniki uzyskane na drodze obliczeń numerycznych porównano z rozwiązaniem teoretycznym. Poddano analizie pola naprężeń w sąsiedztwie wydzieleń grafitu, którego kształt sprowadzono do trzech głównych postaci występujących w praktyce. Na podstawie wyznaczonej zależności pomiędzy naprężeniem efektywnym σef a kształtem wydzieleń grafitu można oszacować współczynnik intensywności naprężeń KI znając właściwości wytrzymałościowe osnowy oraz kształt wydzieleń grafitu. Zaproponowana autorska metoda określenia wzajemnych relacji między obciążeniem mechanicznym a mikrostrukturą żeliwa może stanowić podstawę precyzyjnej oceny jakości części i podzespołów samochodowych wykonywanych z żeliwa.

EN

In this paper the problem of the determination of effective tensions σef in the matrix of the ferritic cast iron on the ground of proposed computational model has been described. Results obtained in the way of numeric calculations have been compared with the theoretical solution. Stress (tension) fields (in the nearness of the graphite precipitations whose the shape has been reduced to three forms occurring in practice) have been subjected. On the ground of the relationship, between the effective stress σef and the shape of the graphite precipitations, determined in the work, is possible to estimate the coefficient of the intensity of stresses KI knowing tensile proprieties of matrix and the shape of graphite precipitations. The proposed authors method to determine the relations between the mechanical load and cast iron microstructure may be treated as the base of precise quality assessment of the vehicle parts and subassemblies fabricated from cast iron.

16

Uwagi na temat zasady naprężeń efektywnych dla gruntów częściowo nasyconych

Sikora Z., Ossowski R.

Zeszyty Naukowe. Budownictwo / Politechnika Śląska

|

2003

|

z. 97

159-166

PL

W artykule zawarto krytyczny przegląd stosowalności klasycznego wzoru naprężeń efektywnych Bishopa oraz propozycję rozszerzenia tej zasady w zastosowaniu do gruntów częściowo nasyconych z uwzględnieniem zjawisk kapilarności, ciśnienia osmotycznego i wytrzymałości strukturalnej.

EN

A critical discussion on the classic Bishop principle of effective stress is presented. Subsequently a new proposal for extending of the classical Bishop's equation for unsaturated soils is given. The extension includes influence of capillarity, osmotic suction and soil structural strength behaviours.

17

Geometry influence analysis on the distribution of effective stress in the contact zones of structures

Kopecki H., Mazurek P.

Zeszyty Naukowe Politechniki Rzeszowskiej. Mechanika

|

2002

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z. 58 [193]

135-140

EN

The paper presents the stress distribution analysis in the contact zones of select cases. Using FEM procedures and photo-elastic methods the problem is considered from real stress distribution conformity point of view.