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1

Problemy napotykane w diagnostyce materiałowej eksploatowanych elementów instalacji przemysłowych

Mężyk Dariusz, Zając Bogdan

Rynek Energii

|

2023

|

Nr 6

66--70

PL

Podczas długotrwałej eksploatacji bloków energetycznych materiały konstrukcyjne stosowane w przemyśle energetycznym pracują w warunkach zmiennych pól naprężeń i zmiennych temperatur. Materiały te są narażone na oddziaływanie środowiska gazów i cieczy oraz na działanie obciążeń mechanicznych. Czynniki te powodują pogorszenie ich własności mechanicznych. Jedną z metod rozpoznania aktualnego stanu materiału są badania diagnostyczne, zarówno nieniszczące, jak i niszczące. W referacie omówiono niektóre aspekty badań kilku elementów długo eksploatowanego kotła energetycznego i problemy związane z oceną ich aktualnego stanu technicznego.

EN

During long-term operation of power units, construction materials used in the power industry work in conditions of changing stress ﬁelds and changing temperatures. These materials are exposed to the effects of gases and liquids and to mechanical loads. These factors cause deterioration of their mechanical properties. One of the methods of recognizing the current state of the material are diagnostic tests, both non-destructive and destructive. The paper discusses some aspects of testing several elements of a long-operated power boiler and problems related to the assessment of their current technical condition.

2

Influence of different machining processes on fatigue life performance of engineered surfaces: a short review

Grzesik Wit

Journal of Machine Engineering

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2022

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Vol. 22, No. 2

18--30

EN

In this paper fundamental information on the influence of the real machined surfaces generated by different machining processes on the fatigue life of machine parts are presented. In the first part the various approaches for the assessment of the stress concentration factor and the correction of a fatigue life limit are discussed. In the second part the results of standard fatigue tests are compared with computed data and predictions using FEM based simulations. The effect of surface discontinues (valleys) in the real surface profiles is related to engineered parts made of different materials including steels, aluminium alloys, aerospace alloys and composites.

3

Research of stress concentration at closely placed holes in wing bearing area in anisotropic plater

Maksymovych Marta, Lazorko Aleksandr, Maksymovych Olesia, Dmitriiev Oleh

Diagnostyka

|

2022

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Vol. 23, No. 4

art. no. 2022302

EN

In this article effective approach of the study of high-stress concentration at closely placed holes in wing bearing area (in anisotropic plates) is proposed. It is based on the boundary integral equation method with the additional use of the asymptotic method. The simplicity, precision of the approach and the stability of the solution are illustrated in the calculation of stresses in the plate with a circular hole, an elliptical hole, elongated holes, a plate with two closely spaced elliptical holes.

4

Stress and failure analysis of composite plates with circular hole subjected to shear loading. Part 1, Analytical and finite element formulation

Khechai Abdelhak, Tati Abdelouahab, Belarbi Mohamed-Ouejdi, Rekbi Fares Mohammed Laid

Composites Theory and Practice

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2022

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R. 22, nr 4

205--210

EN

This current paper, which is the first part of two parts of a complete article, presents the theoretical and finite element formulation developed and proposed by the authors to obtain the stress concentration factors (SCFs) and the first ply failure (FPF) loads of composite laminated plates. The numerical studies are performed using a quadrilateral finite element of four nodes with thirty-two degrees of freedom. The present finite element was previously developed by the authors to study the bending and buckling of composite plates. The present finite element is a combination of two finite elements. The first one is a linear isoparametric membrane element, and the second one is a high-precision rectangular Hermitian element. In the second part of the paper, several examples will be considered to demonstrate and affirm the accuracy and the performance of the present element, as well as highlight the effect of some parameters on the stress distribution. The FPF strengths and their locations in laminated plates with and without holes are calculated by adapting the Hashin-Rotem, Tsai-Hill, and Tsai-Wu failure theories.

5

Stress and failure analysis of composite plates with a circular hole subjected to shear loading. Part 2, Results and discussions

Khechai Abdelhak, Tati Abdelouahab, Belarbi Mohamed-Ouejdi, Rekbi Fares Mohammed Laid

Composites Theory and Practice

|

2022

|

R. 22, nr 4

225--232

EN

This paper, the second part of two parts of a complete paper, presents the analytical and numerical results of stresses around circular cutouts in anisotropic and isotropic plates under shear loading. The main aim of this study is to understand the effect of the presence of cutouts on the stress concentration and failure mechanisms in composite laminates. The numerical investigations are performed by means of the quadrilateral finite element of four nodes with thirty-two degrees of freedom. The present finite element is a combination of two finite elements. The first one is a simple linear isoparametric membrane element and the second one is a high-precision rectangular Hermitian element. The analytical and finite element formulations were presented in the first part of the paper. Several new examples are considered to demonstrate and affirm the accuracy and the performance of the present element and to highlight the effect of some parameters on the stress distributions. The numerically obtained results are found to be in good agreement with the analytical findings. On the other hand, first ply failure (FPF) strengths in laminates with and without holes are calculated by adapting the Hashin-Rotem, Tsai-Hill, and Tsai-Wu failure theories. Finally, the numbers of the figures are obtained, using various E1/E2 ratio values, for the maximum positive and negative stresses values located in the vicinity of the cutout versus the angular location of points, and for various fiber orientation angles.

6

Określenie stopnia wyczerpania struktury i własności mechanicznych wybranych elementów głównych rurociągów parowych bloków energetycznych

Mężyk Dariusz, Zając Bogdan, Olszewski Grzegorz, Kowal Marcin

Badania Nieniszczące i Diagnostyka

|

2022

|

1-4

44--49

EN

The article discusses the main factors influencing the failure frequency of pipeline systems of power units in domestic power plants and combined heat and power plants. Due to the operating conditions and the associated loads, the most important are the fresh steam pipelines, and mainly their shaped elements (elbows, tees, cross-pieces, steam mixers, main valves). The basic methods of assessing the technical condition of the main elements of pipelines using both non-destructive and destructive testing methods were listed. The article focuses on the results of the assessment of the φ= 508 x 20 bend (straight) section made of 10H2M steel taken from a reheated steam pipeline with a total operating time of approximately T = 280,000 hours.

PL

W artykule omówiono główne czynniki wpływające na awaryjność układów rurociągów bloków energetycznych krajowych elektrowni i elektrociepłowni. Ze względu na warunki pracy i związane z nimi obciążenia najistotniejsze znaczenie mają rurociągi pary, a głównie ich elementy kształtowe (kolana, trójniki, czwórniki, mieszacze pary, zasuwy główne). Wymieniono podstawowe metody oceny stanu technicznego głównych elementów rurociągów zarówno metodami badań nieniszczących jak i niszczących. W artykule skoncentrowano się na wynikach oceny odcinka kolana (prostki) φ =508 x 20 ze stali 10H2M pobranego z rurociągu pary wtórnie przegrzanej o sumarycznym czasie pracy około T = 280 000 godzin.

7

The stress-minimizing hole in a shear-loaded elastic plate at a given energy increment

Vigdergauz S.

Archives of Mechanics

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2022

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Vol. 74, nr 2-3

109--126

EN

Minimization of the peak tangential stresses around a single hole in an infinite 2D elastic plate under remote pure shear and a given hole-induced strain energy level is considered as a free-shape optimization problem under a physical constraint. It is solved by combining a genetic algorithm with the almost analytical, and hence highly accurate stress-strain solver for any finitely parameterized family of closed curves. The results obtained in wide ranges of the governing parameters are detailed and discussed. They may be applicable to the optimal holes design in constructive elements and dilute perforated structures. The current analysis extends the author’s previous publications, which were focused on the unconstrained shape optimization within the same setup.

8

Numerical study on dimensions and orientation effect of semi-elliptical cracks in PE100 pipelines

Zitouni T. A., Labed Z.

International Journal of Applied Mechanics and Engineering

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2021

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Vol. 26, no. 3

198--207

EN

The through-thickness crack or surface crack in PE100 pipes subjected to internal pressure represents a serious risk to the structural integrity of HDPE pipes, which has attracted wide attention in modern industry. Although experimental research offers reliable predictions of surface crack influence on pipes, the relatively high cost hinders its application. The numerical simulation, as a cost-effective alternative, has been widely applied to assess stress displacement and strain to the entire pipe structure. This is the initial approach adopted in recent decades. This article provides simulations tests of an uncracked pipe and cracked PE100 pipe under different internal pressure values, with varying each time the dimensions of the crack with 1 mm rate for minor and major radius and 0.5mm rates for the largest contour radius, using ANSYS MECHANICAL STRUCTURAL STATIC for simulation.

9

A new method for measurement the residual stresses in friction stir welding

Jweeg M.J., Hamdan Z.Kh., Majeed A.H., Resan K.K., Al-Waily M.

Archives of Materials Science and Engineering

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2021

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Vol. 112, nr 2

63--69

EN

Purpose: The residual stresses in different welding methods are fundemental problems to consider. Friction stir welding is one of a solid state joining process, it is economical in that it permits joining together different materials, the specimens in this method (FSW) have excellent properties of mechanical as proven by tensile, flextural and fatigue tests, also it is environmentally friendly process minimizes consumption of energy and generate no gasses or smoke. In friction stir welding , there are two kinds of generated residual stresses: tensile stress and compressive stress. So, this study measuring the residual stresses by using a new method for measuring residual stresses depends on tensile testing and stress concentration factor, this method is a simple, fast and low cost, also it is not need special device. Design/methodology/approach: In previous studies, several techniques were used to predict the value of residual stress and its location, such as destructive, semi-destructive, and non-destructive methods. In this study, a simple, new, and inexpensive way was used based on the tensile test and stress concentration of the friction stir welding (FSW). Findings: By comparing the results obtained with the previous studies using the X-ray method, with the current research, it was found that the results are good in detecting the location and value of the residual stress of friction stir welding. The value of discrepancy of the residual stress in the results between those obtained by the previous method and the current method was about 3 MPa. Research limitations/implications: There are many rotational and linear feeding speeds used in this type of welding. This research used two plates from 6061 AA with 3mm thickness, 100 mm width, and 200 mm length. The rotational speed used in friction stir welding was 1400 rpm, and the feeding speed was 40 mm/min. Practical implications: The residual stress obtained with the new method is 6.2 MPa, and this result approximates other known methods such as the X-ray method in previus studies. Originality/value: Using a new simple method for measuring residual stresses of friction stir welding depends on stress concentration factor and tensile testing. This method is fast and low cost , also it is not need specialized device, compared to other methods such as x-ray or hole drilling methods.

10

Thermo-mechanical stress analysis of dissimilar material joints using FEM

Somadder Somnath

Journal of Mechanical and Energy Engineering

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2020

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Vol. 4, No 2

147--153

EN

This article presents numerical investigation of isotropic dissimilar material joints. Dissimilar material joints are broadly used in in various structures, including offshore, nuclear, electronic packaging, IC chip and spacecraft various fields of science and technology. In bi-material joints two different material are bonded with common interface region. High stress concentration occur at the interface of the joint under thermo-mechanical loadings due to the difference in the elastic properties and the thermal expansion coefficients of dissimilar materials.The stresses acting along the interface of dissimilar material joints are very important to determine whether the structure is reliable or not for operation. The main purpose of this research is to provide finite element solutions to predict the stress distribution at the interface of the joint based on the theory of elasticity.

11

The simulation of the stress field of welded joint containing discontinuity No 1014

Nawrocki Jerzy, Słania Jacek

Welding Technology Review

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2019

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R. 91, nr 1

19--23

EN

This paper contains the results simulation and linear elastic fracture mechanic (LEFM) calculation of the welded joint contains it discontinuity 1014. The model base material C-Mn non-alloy steel S235JRG2 according to EN 10025-2 and consumable GMAW wire electrode G3Si1 according to EN ISO 14341 was prepared. Due to stress singularity effect located at the tip of the crack, the Huber-Mises-Hencky (H-M-H) hypothesis cannot be used, so that the stress intensity factor (KI) and fracture toughness (KIC) was applied. The LEFM analysis showed the range where the existence of crack can be acceptable. Based on well-known LEFM issue the verification of simulation program was performed. The stress intensity factor (KI) values was obtained from FEM simulation process.

PL

Przedmiotem artykułu była prezentacja pola naprężenia złącza spawanego zawierającego niezgodność spawalniczą 1014 (pęknięcie podłużne w materiale podstawowym równoległe do osi spoiny) obliczonego za pomocą symulacji MES oraz mechaniki pękania.

12

Wpływ chropowatości powierzchni na trwałość zmęczeniową elementów maszyn – postęp w dziedzinie badań i symulacji

Grzesik Wit

Mechanik

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2019

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R. 92, nr 5-6

307--313

PL

W artykule przedstawiono podstawowe informacje dotyczące wpływu chropowatości powierzchni na trwałość/wytrzymałość zmęczeniową elementów maszyn wykonanych z różnych materiałów konstrukcyjnych i z zastosowaniem różnych metod obróbki. Podano zasady oceny wpływu chropowatości jako zbioru mikroskopijnych karbów na powierzchni rzeczywistej oraz odpowiednie formuły umożliwiające wyznaczenie współczynnika koncentracji naprężeń, który koryguje wartość dopuszczalnej trwałości zmęczeniowej. Wyniki testów zmęczeniowych porównano z wynikami obliczeń i symulacji metodą elementów skończonych (MES). Efekt wpływu chropowatości powierzchni odniesiono do elementów maszyn wykonanych ze stali, stopów aluminium, stopów lotniczych – tytanu i niklu oraz kompozytu wzmocnionego włóknami węglowymi.

EN

In this paper fundamental information on the influence of surface roughness on fatigue life/limit stresses of machine elements made of different construction materials using different machining/manufacturing processes are presented. The rules for the assessment of surface finish influence represented by the set of microscopic notches on the real machined surfaces, which allow the determination of the stress concentration factor and the correction of a fatigue life limit, are provided. The results of fatigue tests are compared with computed data and predictions using FEM based simulations. The effect of surface discontinues resulting from surface roughness are related to machine elements made of steels, aluminium alloys, aerospace alloys – titanium and nickel based superalloys and composite reinforced by graphite fibres.

13

Numerical investigations of stress concentration in reinforcement steel structure by composite overlays

Szybiński Bogdan, Wygoda Mateusz

Journal of KONES

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2019

|

Vol. 26, No. 4

249--256

EN

The stress concentration observed in the vicinity of cut-outs and holes in structural elements significantly influences the fatigue endurance of machines subjected to cyclic loads. Numerous studies have been made so far to improve this situation and increase the structure lifetime. Several design recommendations have also been worked out to avoid the problem of premature failure. The proposed article illustrates the influence of the composite overlays applied around the cut-outs made in flat steel constructional elements subjected to axial tension. The detailed study concerns the reinforcement made from the FRP (fibre reinforcement polymer) composite applied around the notches. Two types of composite materials were used, namely: TVR 380 M12/R-glass (glass fibres embedded in epoxy resin matrix) and AS4D/9310 (carbon fibres embedded in epoxy resin matrix). In the first step, the detailed numerical studies (finite element analysis) were performed for the steel samples (with no overlays added) with cut-outs made in the form of circle, square and triangle hole (the last two with rounded corners). The results of these studies were compared with the existing analytical solutions with respect to the stress concentration factors (SCF) estimation. The relatively good conformity was observed when using dense meshes of finite elements placed around the void vicinity. In the next step, the composite overlays were applied around cut-outs and their influence on the stress concentration was investigated. The influence of the fibre orientation, numbers of layers, sizes of the composite overlay used were considered. It was proved that the application of composite overlays evidently decreases the stress concentration around the notches.

14

Symulacja pola naprężeń w spoinach z wykorzystaniem MES

Nawrocki J., Słania J.

Przegląd Spawalnictwa

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2018

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R. 90, nr 8

62--67

PL

W codziennej praktyce projektowej obliczenia spoin pachwinowych są wykonywane w oparciu o metodę zawartą w obowiązkowej do stosowania normie PN-EN 1993-1-8:2006. Wynikiem obliczeń jest naprężenie zredukowane wyznaczane analitycznie dla przekroju krytycznego. Norma nie odnosi się do zjawiska koncentracji naprężeń, która ma miejsce w złączu w wypadku stosowania spoiny pachwinowej. W poniższej pracy zastosowano metodę elementów skończonych w celu oszacowania tego zjawiska.

EN

The calculation of the fillet welds are performed based on the method delivered by the standard PN-EN 1993-1-8:2006. The typical result of the calculations is the Huber-Mises criteria for the critical section. The standard does not refer to the phenomenon of stress concentration that have to take place in the welded joint in case of incomplete fusion. In this paper the finite element method is used to estimate precisely this phenomenon.

15

Stress and Strain Concentrations in Steel Angle Tension Members Connected by One Leg

Bernatowska E., Ślęczka L.

Czasopismo Inżynierii Lądowej, Środowiska i Architektury / Journal of Civil Engineering, Environment and Architecture

|

2018

|

z. 65, nr 2

5--16

EN

The paper presents the numerical simulations results of net section failure in tensioned angles. Angles are made of structural steel with nominal grade S235. Simulation takes into account ductile fracture initiation, by application of GursonTvergaard-Needleman (GTN) material model. Parametrical analysis of ultimate resistance was carried out. The finite elements analyses were conducted by ABAQUS computer program. Shear lag effect in considered joint was observed, as a non uniform tensile stress distribution in angles in the vicinity of a connection. Stress concentration areas and stress concentration factors have been predicted, both in elastic and ultimate behaviour of joint. Especially change of non-uniform stress distribution in net cross-section was observed, during increase of loading, until the ultimate resistance was reached.

16

Design modifications of pressure boilers with flat endplates with stress relief groove

Szybiński B., Wygoda M.

Journal of KONES

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2017

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Vol. 24, No. 3

309--316

EN

Stress concentration is still present in the vicinities of structural notches in engineering structures. Zones with higher level of stress are particularly dangerous for structures subjected to fatigue or dynamic loads. The vessels with flat endplates with stress relief grooves are the common examples of such structures. Unfortunately, no clear evidence is given in existing codes how optimally to choose the circular groove radius and the optimal value of that radius depends on the dimensions of the boiler, operating conditions and the material used in manufacturing. Additionally, commonly used grooves with circular shapes are not optimal. Series of experimental tests, numerical or analytical studies presented in numerous articles confirmed these facts. In the presented article, the Authors proposed two-stage modification of the investigated vessel. The first step relies on change of the shape of the groove in the endplate, which provides certain reduction of stress concentration but still plastic deformations in the groove vicinity are not eliminated. The second step of the design modification is proposed for the boiler with the optimal elliptic groove configuration. In this step, some material is added around the top of the outer edge of the endplate. Two simple shapes are proposed for these parts - the short cylindrical ring or alternatively the circular ring welded on the top the endplate is used. For both concepts, the search of optimal dimension/parameters is performed. The numerical results of that study clearly show that the full elimination of plastic deformations near the groove is possible. The numerical analysis and optimizations were made with the well- established finite element software ANSYS, which is accepted by commonly used codes for designing of pressure vessels.

17

The numerical modeling of adhesive joints in reinforcement of wooden elements, subjected to bending and shearing

Rapp P.

Drewno : prace naukowe, doniesienia, komunikaty

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2017

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vol. 60, nr 199

21--36

EN

The subject of this paper is a formulation and discussion about an adhesive joint model in cases of reinforcement or reconstruction of weakened cross-sections of wooden elements. The problem is modeled within the linear theory of elasticity as a plane stress case. It is assumed that wood is an orthotropic material. Reinforcement is achieved by attaching a covering plate, and reconstruction by introduction of an insert at a weakened (deteriorated) zone of the element. Analysis of the influence of covering plates and insert thickness on the stress state in adhesive and in adherends is carried out. Elements subjected to bending moments or bending moments with shear forces are considered.

18

Wpływ karbu na zmiany wartości współczynnika intensywności naprężenia podczas wzrostu pęknięć zmęczeniowych dla stopu PA6

Faszynka S., Rozumek D.

Przegląd Mechaniczny

|

2016

|

nr 7

40--44

PL

W pracy przedstawiono wyniki badań doświadczalnych rozwoju pęknięć zmęczeniowych w próbkach o przekroju poprzecznym prostokątnym, wykonanych ze stopu aluminium PA6 przy cyklicznym zginaniu. W próbkach zostały wykonane ostre i łagodne jednostronne karby. Badania doświadczalne przeprowadzono na maszynie zmęczeniowej MZGS-100 w zakresie niskiej i wysokiej liczby cykli, przy współczynniku asymetrii cyklu R =-1. Wyniki badań przedstawiono w postaci wykresów długości pęknięć zmęczeniowych o, w funkcji liczby cykli N oraz prędkości wzrostu pęknięć zmęczeniowych w funkcji zakresu zmian współczynnika intensywności naprężeń ΔKI.

EN

The paper presents experimental tests results of the fatigue crack growth in PA6 aluminium alloy under cyclic bending in specimens with rectangular cross-section. The specimens were weakened by sharp and blunt one-sided notches. The tests were performed on the fatigue test stand MZGS-100 in the Iow and high cycle fatigue regime for the stress ratio R =-1. The test results were described on graphs of the fatigue crack length o versus numbers of cycles N and of the fatigue crack growth rate versus changes of the stress intensity factor range ΔKI.

19

Designing of stress relieve groove parameters for flat endplates of pressure boilers

Szybiński B., Barski M., Wygoda M.

Journal of KONES

|

2016

|

Vol. 23, No. 4

513--520

EN

The application of flat ends as closures in pressure boilers is a certain alternative for commonly used dished ends. However, it is inevitably joined with the stress concentration presence in the vicinity of the junction between the cylindrical pipe and the ending flat plate. The notch effect, which is observed in the connection area, is usually caused by the abrupt change of the inner wall shape and the lack of the curvature continuity in this region. The problem of the stress reduction in the transition zone between the cylindrical pipe and the endplate has been studied by researchers from many years and several proposals how to modify the shape of the respective elements have been established. On the base of these results, several designs for flat end closures are proposed in the codes applied in pressure boilers calculations. This paper shows the effectiveness of one of the design proposals, admitted by code EN 13445-3. In the proposed analysis the special attention are paid to flat ending plates with the circular stress relieve grooves. The parameters of the groove radii and location of its centre are set by a system of inequalities, which usually defines the region of admissible values for radii and position of the circular groove centre. The choice of these values strongly influences the stress concentration and in the considered code, no clear suggestions or justification is given how to choose the best groove parameters, providing the minimum stress concentration. In this report, the Authors show how to choose the best combination of the design parameters providing the minimum stress concentration.

20

Static strength analysis of plate structures using finite element method

Zachwieja J.

Journal of Polish CIMEEAC

|

2015

|

Vol. 10, no 1

155-160

EN

The paper presents the issues regarding modelling and strength calculations for the plate structures including thinwalled tanks and water tubes in steam boilers or heat exchangers subject to thermal stresses. In this case, the subject of the analysis is not the stress-strain state due to the pressure in the structure cross-section but the conditions at the interface between plate and lifting lugs used for handling tanks decommissioned due to technical and economic factors or replaced with the new ones.