Wyniki wyszukiwania - BazTech

1

Assessment of crack growth and fatigue life of an axial fan blade based on a co-simulation approach

Hassen Mariem Ben, Fakhari Seyyed Mojtaba, Mrad Hatem

Advances in Materials Science

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2023

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Vol. 23, nr 3(77)

61--79

EN

This paper presents static and dynamic stress analyses of an axial fan blade, which were carried out under real-life centrifugal and aerodynamic loading conditions using the Abaqus software. The location of the crack was identified on the pressure side of the blade at the conjunction between the blade and the blade root. It reveals a high agreement between the predicted location of stress distribution and the real origin of the crack location. Furthermore, a fracture mechanics criterion was adopted to simulate fatigue crack growth. This was performed using a fracture analysis FRANC3D code for three-dimensional problems. As a result, the calculated stress intensity factors (SIFs) were presented for the first steps, and the fatigue life of the fan blade was evaluated using the Forman de Koning model at different stress ratios.

2

Prediction of Fatigue Cracks Using Gamma Function

Moussouni Abdelfetah, Benachour Mustapha, Benachour Nadjia

Fatigue of Aircraft Structures

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2022

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Iss. 14

29--46

EN

In the present study it has been endeavored to estimate the fatigue crack propagation in V-notch Charpy specimens of 2024 T351 Al-alloy. For this purpose, a new application of fatigue crack growth (FCG) is developed based on the “Gamma function.” Experimental fatigue tests are conducted for stress ratios from 0.1 to 0.5 under constant amplitude loading. The empiric model depends principally on physical parameters and materials’ properties in non-dimensional form. Deviation percentage, prediction ratio, and band error are used for validation of the performance of the fatigue life. The results determined from Gamma application are in good agreement with experimental FCG rates and those obtained from using Paris law.

3

A FCG Model and the Graphical User Interface Under Matlab for Predicting Fatigue Life: Parametric Studies

Kebir Tayeb, Correia José A.F.O., Benguediab Mohamed, Imad Abdellatif

Fatigue of Aircraft Structures

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2021

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Iss. 13

116--139

EN

The focus of this research work was predicting the fatigue life of mechanical components used for industrial and transport systems. To understand how the phenomenon of fatigue occurs in a material, the fatigue crack growth is studied. The purpose of this work was to create a graphical user interface (GUI) under Matlab to allow researchers to conduct the parametric studies of fatigue crack propagation to predict fatigue life. In this work, three models for fatigue crack propagation were used: those of Paris, Walker and Forman in order to study the three parameters: the Paris exponent m, load ratio R and hardness KIC, respectively. In addition, a novel model FCG was developed to study the influence of the hardening parameters (K′, n′) on fatigue crack propagation. The comparison of the simulation results with those in the literature shows good agreement.

4

The effect of technological treatments and loads on the service life of fillet welds

Lewandowski Janusz, Rozumek Dariusz

Biuletyn Instytutu Spawalnictwa w Gliwicach

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2020

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Vol. 64, No. 2

21--25

EN

The paper presents test results concerning the service life of fillet welds made in steel S355. In addition, the article discusses the initiation and growth of fatigue cracks in specimens subjected to bending with torsion. The tests were performed in relation to constant stress ratio R = -1 and 0. The results presented in the article take into account the effect of the technological treatment on the service life of the specimens. The tests revealed longer service life of the specimens not subjected to the technological treatment, both when R = -1 and 0.

PL

Przedstawiono wyniki badań trwałości, inicjacji oraz wzrostu pęknięć zmęczeniowych próbek ze stali S355 ze spoinami pachwinowymi, poddanych zginaniu ze skręcaniem. Badania przeprowadzono przy stałej wartości współczynnika asymetrii cyklu R = - 1 oraz 0. Prezentowane wyniki uwzględniają wpływ zabiegu technologicznego na trwałość badanych próbek. Stwierdzono większą trwałość zmęczeniową próbek bez zabiegu technologicznego, zarówno dla R = -1 jak i R = 0.

5

Assessing surface fatigue crack growth in railway wheelset axle

Rudavskyi D. V., Kaniuk Yu. I., Duriagina Z. A., Kulyk V. V., Shefer M. S., Dolinska I. Ya.

Archives of Materials Science and Engineering

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2020

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Vol. 106, nr 2

59--67

EN

Purpose: The aim of the proposed research is to create a calculation model of surface fatigue crack growth at the axle of railway wheelset working under operational loads. Design/methodology/approach: The energy approach of the fracture mechanics was used to formulate the calculation model of fatigue crack propagation at the wheelset axle surface. The method of least squares was used to determine the investigated material mechanical constants that the kinetic equations of the calculation model contain. The system of differential equations of crack growth kinetics was solved numerically using the Runge-Kutta method. Findings: On the basis of the energy approach of the fracture mechanics the calculation model of fatigue macrocrack growth in three-dimensional elastic-plastic body in case of a mixed-mode I+II+III macromechanism of fracture has been built. On the basis of the created calculation model, the kinetics of the growth of fatigue cracks was investigated both in the middle part of the wheelset axle and in the axle journal. Research limitations/implications: The results obtained on laboratory specimens should be tested during a real railway wheelset axle investigation. Practical implications: The created calculation model can be used in practice to formulate method of residual lifetime estimation of railway wheelset axle. Originality/value: It was shown, that surface crack kinetics depends not only on the crack initial area but also significantly depends on the crack edge geometry and comparatively small crack-like defects at the wheelset axle surface can reach critical sizes in comparatively short run. It has been found that mechanical shear stresses caused by the weight of the loaded railway wagon in the cross section of the wheelset axle journal can significantly accelerate the growth of the transverse fatigue crack at the axle surface, reducing the period of crack subcritical growth by about 20%.

6

The fatigue crack behavior of 7N01-T6 aluminum alloy in different particle environments

Chen Y. Q., Tang Z. H., Pan S. P., Liu W. H., Song Y. F., Zhu B. W., Liu Y., Wen Z. L.

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 4

468--483

EN

An experimental method of evaluating the fatigue behavior of alloys in different particle environments was designed, and the effects of four kinds of particles (i.e., graphite, CaO, Al2O3, and MnO2) on the crack propagating behavior of 7N01-T6 behaviour alloys were investigated. The results show that the particles deposited on the crack surface exert significant influence on the fatigue crack propagation behavior thereof. This influence strongly depends on the elastic moduli of the particles (Ep). As Ep is less than that of aluminium alloy (EAl), the particle accelerates the fatigue-crack-growth rate (FCGR) in the alloys due to the lubrication of the particles on the mating fracture surfaces. When the difference between Ep and EAl is small, the particle effect on the FCGRs of the alloys is small due to the counteraction between the decrease in friction and the promotion on the crack closure of mating fracture surfaces. When Ep is greater than EAl, the particles slow down the FCGRs of the alloys on account of significant crack closure effect. As Ep is much greater than EAl, the particles increase the FCGRs because of the increasing stress concentration at the crack tip.

7

The diagnostics and ways heat treatment optimization of a railway wheels steel

Vira Volodymyr, Kulyk Volodymyr, Chepil Roman, Kharchenko Yevhen, Duriagina Zoia

Diagnostyka

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2019

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Vol. 20, No. 2

105--111

EN

A high resolution sensor of linear displacements has been elaborated for diagnosing the size of the crack tip opening in standard test specimens. Based on the data measured during fatigue crack growth resistance tests of a wheel steel heat treated after various modes, calculations of the strain and energy parameters of local fracture were performed for the corresponding variants of treatment, and fatigue crack growth rate diagrams were constructed using different approaches of fatigue fracture mechanics. It was established that the diagrams obtained using the strain and energy approaches are more sensitive to material microstructure and its mechanical properties than the traditional diagrams obtained using the stress approach. Based on the parameters of the fatigue crack growth resistance estimated using the strain and energy approaches, the effective diagnostics and the best heat treatment mode for the wheel steel was developed. It comprises the stages of isothermal quenching and tempering at a temperature of 500 °С, providing the highest fatigue fracture toughness of the steel.

PL

Opracowano czujnik przemieszczeń liniowych o podwyższonej czułości dla diagnozowania rozwartości szczeliny na podstawie określenia odkształceń i energetycznych parametrów uszkodzenia lokalnego. W oparciu o różne podejścia mechaniki zniszczenia zmęczeniowego zostały skonstruowane diagramy prędkości propagacji pęknięć zmęczeniowych w stali koła kolejowego po różnych rodzajach obróbki cieplnej. Ustalono, że diagramy odporności na pękanie, otrzymane według odkształceniowego lub energetycznego podejścia, są bardziej wrażliwe do strukturalnych i mechanicznych własności materiałów w porównaniu z tradycyjnymi diagramami otrzymanymi według podejścia siłowego. Pokazano zalety odkształceniowego i energetycznego podejścia w porównaniu z podejściem siłowym w zakresie optymalizacji charakterystyk odporności materiałów na pękanie. Dokonano skutecznej diagnostyki stanu technicznego materiału oraz optymalizacji obróbki cieplnej stali kół kolejowych. Ustalono, że hartowanie izotermiczne z odpuszczaniem przy temperaturze 500°C zapewnia najwyższą odporność stali na pękanie.

8

Fatigue crack growth rate, microstructure and mechanical properties of diverse range of aluminum alloy: a comparison

Brahami A., Bouchouicha B., Zemri M., Fajoui J.

Mechanics and Mechanical Engineering

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2018

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Vol. 22, nr 1

329–-339

EN

In practice for all metallic materials, damage by fatigue usually takes in two steps, the appearance of an initial crack which then grows as a function of the present microstructure. The objective of this study is to identify the elements influencing the fatigue crack growth rate on aluminum alloys of different microstructures. Characterization tests and microstructural analysis on 2024-T3, 5083-H22, 6082-T6 and 7075-T6 shades have been carried out. Based on the experimental results obtained, AA7075-T6 has the best fatigue crack rate resistance which is explained by its behavior as well as the nature and dispersive distribution of the secondary element.

9

Fatigue crack growth rate, microstructure and mechanical properties of diverse range of aluminum alloy: a comparison

Brahami A., Bouchouicha B., Zemri M., Fajoui J.

Mechanics and Mechanical Engineering

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2018

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Vol. 22, nr 4

1453--1462

EN

In practice for all metallic materials, damage by fatigue usually takes in two steps, the appearance of an initial crack which then grows as a function of the present microstructure. The objective of this study is to identify the elements influencing the fatigue crack growth rate on aluminum alloys of different microstructures. Characterization tests and microstructural analysis on 2024-T3, 5083-H22, 6082-T6 and 7075-T6 shades have been carried out. Based on the experimental results obtained, AA7075-T6 has the best fatigue crack rate resistance which is explained by its behavior as well as the nature and dispersive distribution of the secondary element.

10

Fatigue crack growth and probability assessment for transverse TIG welded Aluminum alloy 6013-T4

Haryadi G. D., Tungga Dewa R., Ekaputra I. M. W.

Journal of Theoretical and Applied Mechanics

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2018

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Vol. 56 nr 1

179--190

EN

The aim of this study is to investigate the fatigue crack growth behavior with post weld heat treatments (T4) on transverse tungsten inert gas-welded Aluminum alloy 6013. All fatigue tests have been carried out using center cracked tension specimens at ambient temperature under a stress ratio of R = 0.3. The results revealed that various time of aging in T4 affects its mechanical properties, also the fatigue crack growth behavior as well. It has been observed that in the heat treated samples the crack growth rate is lower than that in the as-welded sample, but higher than the rate in the base metal. To be more specific, samples with 18 hours aging exhibit the highest tensile strength and fatigue resistance compared to the other heat treated samples. The probability assessment has also been used to determine the fatigue crack growth rate and a good linearity has been found.

11

Hydrogen Assisted Cracking in a Microalloyed Steel Subjected to a Rapid Thermal Cycle at High Temperature

Lopez-Martinez E., Vázquez-Gómez O., Vergara-Hernández H. J., Campillo B.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 1

315--321

EN

In a martensitic-bainitic microalloyed steel, the effect of hydrogen on fatigue crack growth was studied using rotary bending fatigue tests. The steel was subjected to a rapid thermal cycle to get a microstructure similar to that which would be formed within the coarse-grained heat-affected zone of a weld. Crack growth was monitored as a function of the number of cycles applied during fatigue tests on three types of specimens: 1) those without hydrogen charge, 2) those charged with hydrogen and 3) those charged with hydrogen which was then discharged through low-temperature heat treatment. All types showed persistent slip marks, and cracks propagated along high-shear-stress planes. In the presence of hydrogen, crack growth was affected by microstructural defects caused by the hydrogen charging process, and the persistent slip marks developed in an area closer to the crack tip and crack path. On the contrary, without hydrogen, crack growth occurred perpendicular to the applied force, and the persistent slip marks were fewer in number and further from the crack tip and crack path. This indicates that the plasticity increased (i.e., the damage that occurred in the presence of hydrogen matched the hydrogen-enhanced local plasticity mechanism).

12

Numerical analysis of stress intensity factor in specimens with different fillet geometry subjected to bending

Lewandowski J., Rozumek D.

Acta Mechanica et Automatica

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2018

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Vol. 12, no. 1

38--43

EN

The article presents the maps of xx stress component and compares values of analytical and numerical calculations for the stress intensity factor range of welded specimens with fillet welds which subjected to cyclic bending. The tests were performed under constant value of moment amplitude Ma = 9.20 Nm and stress ratio R = σmin/ σmax = -1. The specimens were made of drag steel rod S355. The specimens were solid and welded. The numerical models were simulated with ABAQUS suite and numerical calculations performed with FRANC3D software.

13

Badania propagacji pęknięć przy cyklicznym zginaniu dla różnych materiałów zgrzewanych wybuchowo

Kwiatkowski G.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2017

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z. 108

73--76

EN

This paper describes fatigue cracks growth in three different bimetallic made by explosive cladding. In any case, it was the same base material - carbon steel P355NH, and clad materials are: austenitic stainless steel 316L, 254SMO and super duplex (50% ferritic structure, 50% of the austenitic structure). Specimens of rectangular cross-section was subje ted to fatigue bending with of the stress mean value equal zero and of constant amplitude equal to 19.41 N•m. The crack propagation was measured using a portable microscope with a micrometer located on the fatigue stand.

14

A Model for Fatigue Crack Growth in the Paris Regime under the Variability of Cyclic Hardening and Elastic Properties

Kebir T., Benguediab M., Imad A.

Fatigue of Aircraft Structures

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2017

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Iss. 9

117--135

EN

Over the last 60 years, several models have been developed governing different zones of fatigue crack growth from the threshold zone to final failure. The best known model is the Paris law and a number of its based on mechanical, metallurgical and loading parameters governing the propagation of cracks. This paper presents an analytical model developed to predict the fatigue crack propagation rate in the Paris regime, for different material properties, yield strength (σy), Young’s modulus (E) and cyclic hardening parameters (K’, n’) and their influence by variability. The cyclic plastic deformation at a crack tip or any other cyclic hardening rule may be used to reach this objective, for to investigate this influence, these properties of the model are calibrated using available experimental data in the literature. This FCGR model was validated on Al-alloys specimens under constant amplitude load and shows good agreement with the experimental results.

15

Corrosion Fatigue Crack Growth Studies on Pressure Vessel and Piping Steels in Water Environment

Mathew N. M., Vishnuvardhan S., Raghava G., Santhi A. S.

Archives of Metallurgy and Materials

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2017

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Vol. 62, iss. 3

1857--1862

EN

Corrosion fatigue crack growth studies were conducted on eccentrically-loaded single edge notch tension specimens made of SA 333 Gr. 6 and SA 516 Gr. 70 carbon steels in water environment. The experiments were conducted using a ±250 kN capacity Universal Testing Machine under constant amplitude sinusoidal loading at a test frequency of 0.50 Hz and stress ratio of 0.1. The fabrication of test specimens and the experiments were carried out based on ASTM E 647 and ASTM E 1820. The crack initiation and growth were monitored and images were captured by using a digital camera at regular intervals of fatigue cycles. By using these images, the length of crack was measured. The tests were terminated when the uncracked portion of the specimens was insufficient to take further load. Crack growth rate and stress intensity factor range values were evaluated at incremental values of loading cycles and crack length. Using the crack growth rate vs. stress intensity factor range plots, best fit curves following power law in the form of Paris’ equation were obtained.

16

Mode I Stress Intensity Factors for Surface Planar Cracks in Circular Bodies Under Rotary Bending

Król R., Grabowski P.

Machine Dynamics Research

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2016

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Vol. 40, No. 4

19--31

EN

A method of calculating stress intensity factors, using point-load weight function, for twodimensional surface cracks subjected to rotary bending, applied to circular objects is described in the paper. The research has regarded planar cracks in finite circular bodies, which may occur e.g. in shaft cross sections of belt-driven machines. This type of drive is widely spread in the technological lines, therefore the research on improving its fatigue durability is crucial for development of this branch of industry. One of a few advantages of the method which has been applied is the possibility to evaluate stress intensity factor (SIF) values precisely in a quick and simple way. The paper shows the computation for various parameters of shape and size of shafts and cracks. The presented method usually yields conservative results compared to reference values obtained for the same configurations with the finite element method, which gives a good perspective to use such calculated SIFs for life assessment. Checking of these possibility is an essential issue of the work described in the paper.

17

Effect of grain size on the fatigue crack growth behavior of 2524-T3 aluminum alloy

Shou W. B., Yi D. Q., Liu H. Q., Tang C., Shen F. H., Wang B.

Archives of Civil and Mechanical Engineering

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2016

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Vol. 16, no. 3

304--312

EN

2524-T3 aluminum alloy sheets with different grain sizes (13 μm, 59 μm, 178 μm, 355 μm, 126 μm, and 87 μm) were prepared using methods such as rolling and annealing. The microstructures and mechanical properties of the 2524-T3 aluminum alloy sheets were studied using optical microscopy (OM), scanning electron microscopy (SEM), and tensile and fatigue crack growth (FCG) rate tests. The grain size had a significant effect on the fatigue crack growth (FCG) rate. Alloys with grain sizes between 50 and 100 μm exhibited high fatigue crack propagation resistances and the lowest FCG rates (da/dN = 1.05–1.45 × 10−3 mm/cycle at ΔK = 30 MPa m1/2). Microstructural observations revealed that fatigue cracks propagated more tortuously in the alloy with grain sizes within the range of 50–100 μm. This result is attributed to the combined effects of grain boundaries, crack deflection, fracture surface roughness-induced crack closure, and plasticity-induced crack closure.

18

Numerical analysis of stress and strain in specimens with rectangular cross-section subjected to torsion and bending with torsion

Faszynka S., Lewandowski J., Rozumek D.

Acta Mechanica et Automatica

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2016

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Vol. 10, no. 1

5--11

EN

The paper presents an analysis of the state of stress and crack tip opening displacement (strain) in specimens with rectangular cross-section subjected to torsion and combined bending with torsion. The specimens were made of the EN AW-2017A aluminium alloy. The specimens had an external unilateral notch, which was 2 mm deep and its radius was 22.5 mm. The tests were performed at constant moment amplitude MT=MBT= 15.84 N.m and under stress ratio R= -1. The exemplary results of numerical computations being obtained by using the FRANC3D software were shown in the form of stress and crack tip opening displacement (CTOD) maps. The paper presents the differences of fatigue cracks growth under torsion and bending with torsion being derived by using the FRANC3D software.

19

Observations on fatigue crack growth and fatigue life of riveted lap joints

Skorupa A., Skorupa M., Machniewicz T., Korbel A.

Mechanics and Control

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2012

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Vol. 31, no. 3

108--114

EN

Effects of variables related to design and production of riveted lap joints representative of longitudinal sheet connections for a pressurized transport aircraft fuselage were experimentally investigated. The specimens from an aircraft Al alloy D16 Alclad sheets of three different thicknesses (1.9, 1.2 and 0.8 mm) were assembled under load control using round head rivets and rivets with the compensator from a P24 Al alloy. For the joints from 1.9 mm thick sheets fatigue tests indicated a dependency of the crack initiation site and crack path on the squeeze force level and on the rivet type. At the same time, increasing the squeeze force led to improved fatigue properties of the joints, specimens assembled using the rivets with the compensator showing fatigue lives consistently longer than joints with the round head rivets. All observed trends have been explained based on hole expansion and load transfer measurements. For thin sheets connected using the round head rivets, local deformations and indentations under the driven rivet head promoted crack initiation and failure in the adjacent sheet. Fatigue test results indicated that the detrimental effect of this type imperfections could outweigh the benefits associated with a decrease in secondary bending due to thinning the sheets. The rivets with the compensator were observed to cause significant local imperfections beneath the manufactured head, which adversely affected the joint fatigue performance.

PL

Sposób zniszczenia i wytrzymałość zmęczeniowa połączeń zakładkowych stosowanych w lotnictwie zależy od wielu czynników technologicznych i konstrukcyjnych, a w szczególności od rodzaju nitu i siły jego zakuwania oraz grubości łączonych blach. W artykule omówiono te zagadnienia na przykładzie blach o różnych grubościach z lotniczego stopu aluminium D16, połączonych zakładkowo za pomocą nitów z łbem kulistym ze stopu PA24. Próbki połączeń poddawane były stałoamplitudowym obciążeniom zmęczeniowym przy różnych poziomach naprężeń nominalnych. Wykazano, że wraz ze wzrostem siły zakuwania nitów rośnie trwałość zmęczeniowa połączenia, a tor pęknięcia oddala się od przekroju netto blachy. Zaobserwowano, że pęknięcia zmęczeniowe pojawiają się w blasze, w której ekspansja otworów nitowych jest mniejsza, co z kolei zależy od rodzaju nitu. Trendy te wyjaśniono na podstawie wyników pomiarów ekspansji otworów nitowych wypełnionych nitami zakutymi przy użyciu różnych sił oraz z uwzględnieniem wyznaczonego eksperymentalnie względnego udziału poszczególnych rzędów nitów w transferze obciążenia. Stwierdzono, że nity z kompensatorem nie są odpowiednie do łączenia cienkich blach; w trakcie zakuwania powstają znaczne deformacje złącza obniżające jego własności zmęczeniowe.

20

Rozwój ścieżek pękania zmęczeniowego przy różnych stosunkach zginania do skręcania

Marciniak Z., Rozumek D., Bodnar G.

Czasopismo Techniczne. Mechanika

|

2010

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R. 107, z. 3-M

87-96

PL

Artykuł zawiera wyniki badań doświadczalnych na próbkach o przekroju prostokątnym wykonanych ze stali 10HNAP (S355J2G1W). Stosunek wysokości próbki do szerokości wynosił 1,5. Badania na zginanie ze skręcaniem prowadzone były przy stosunku amplitudy momentów zginającego do skręcającego M[ag]/M[as] = 0,47; 0,94; 1,87 i częstotliwości obciążenia 26,5 Hz. Całkowity moment M[(t)]=[pierwiastek]M[s][^2](t) + M[g][^2](t) indukowano siłami na ramionach o długości 0,2 m. Jednostronnie utwierdzone próbki badano przy cyklicznym zginaniu ze skręcaniem przy różnych amplitudach momentu zginającego M[ag] = 5,64; 10,17; 15,38 N x m i momentu skręcającego M[as] = 8,23; 10,89, 12,08 N x m. Rozwój ścieżek pękania był obserwowany na powierzchni próbki metodą optyczną.

EN

The paper presents the experimental results concerning fatigue crack paths in the plate specimens made of 10HNAP (S355J2G1W) steel. The specimens have rectangular cross sections of the ratio of height to width equal to 1.5. The tests were realized at a fatigue test stand MZGS-100Ph where the ratio of torsion moment to bending moment was M[B](t)/M[T](t) = 0.47, 0.94, 1.87 and loading frequency was 26.5 Hz. The total moment M[(t)]=[ square root]M[s][^2](t) + M[g][^2](t) was generated by force on the arm 0.2 m in length. Unilaterally restrained specimens were subjected to cyclic bending with torsion with the different amplitudes of bending moment M[aB] = 5.64, 10.17, 15.38 N x m and torsion moment M[aT] = 8.23, 10.89, 12.08 N x m. Crack paths was observed on the specimen surface with the optical method.