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Sadek, M., Bergström, J. & Hallbäck, N. (2023). Computing the stress intensity factor range for fatigue crack growth testing at 20 kHz. Engineering Reports
Open this publication in new window or tab >>Computing the stress intensity factor range for fatigue crack growth testing at 20 kHz
2023 (English)In: Engineering Reports, ISSN 2577-8196Article in journal (Refereed) Epub ahead of print
Abstract [en]

Inertia and damping influence the values of the stress intensity factors (SIFs) at high-frequency loading and they must be included in computations. In the present study, different dynamic simulation procedures were carried out for two types of specimen geometries and the achieved SIF values were compared. Fast computation procedures such as harmonic modal analysis and direct steady-state analysis were compared to the computationally expensive transient dynamic analysis. Two different methods for calculating the SIF, the J-integral and the crack tip opening displacement (CTOD) methods, were applied and compared and the results showed a near perfect agreement in calculation of the mode I SIF. The Rayleigh damping model was introduced into the dynamic computation to investigate its effect and the results revealed a clear effect on the SIF at 20 kHz frequency. The fast direct steady-state analysis showed good agreement to both harmonic modal and transient analysis with the different damping values used and is, after this study, the recommended procedure.

Place, publisher, year, edition, pages
John Wiley & Sons, 2023
Keywords
direct steady-state analysis, harmonic modal analysis, stress intensity factor, transient analysis, very high cycle fatigue
National Category
Applied Mechanics
Research subject
Materials Science
Identifiers
urn:nbn:se:kau:diva-97292 (URN)10.1002/eng2.12792 (DOI)001084293400001 ()2-s2.0-85173796816 (Scopus ID)
Available from: 2023-11-03 Created: 2023-11-03 Last updated: 2023-11-22Bibliographically approved
Chai, G., Bergström, J. & Burman, C. (2023). Crack Initiation in Bulk Matrix of Austenitic Stainless Steel during Very High Cycle Fatigue. Materials Performance and Characterization, 12(2)
Open this publication in new window or tab >>Crack Initiation in Bulk Matrix of Austenitic Stainless Steel during Very High Cycle Fatigue
2023 (English)In: Materials Performance and Characterization, ISSN 2379-1365, E-ISSN 2165-3992, Vol. 12, no 2Article in journal (Refereed) Published
Abstract [en]

In the very high cycle fatigue regime, fatigue crack initiation in high-strength steels is usually correlated to a subsurface inclusion with a fine granular area (FGA). Localized stress-strain concentration at the subsurface inclusion is a critical factor. Fatigue crack initiation with an FGA in the bulk matrix without any defect has rarely been reported. In this paper, a fundamental study on the formation of FGAs in the bulk matrix of an austenitic stainless steel has been carried out using a progressive stepwise load-increasing test with a cycle step of about 108 cycles. FGA formation in the subsurface bulk matrix has been observed. The micro structural damage in the fatigue-tested specimens has been studied using the electron channeling contrast imaging electron microscopy technique. Strain localization and grain fragmentation are the main processes for the formation of FGAs. Local plasticity exhaustion leads to crack initiation due to local stress concentrations. This method can also be used to predict the fatigue damage process, especially the damage rate in individual specimens.

Place, publisher, year, edition, pages
American Society for Testing Materials, 2023
Keywords
very high cycle fatigue, fine granular area, austenitic stainless steel, grain boundary, dislocation
National Category
Other Materials Engineering
Research subject
Materials Engineering
Identifiers
urn:nbn:se:kau:diva-96231 (URN)10.1520/MPC20220094 (DOI)001023843700001 ()2-s2.0-85164956269 (Scopus ID)
Available from: 2023-08-07 Created: 2023-08-07 Last updated: 2023-08-09Bibliographically approved
Chai, G., Bergström, J. & Burman, C. (2023). Formation of fine granular area in a non-defect matrix of austenitic stainless steel during very high cycle fatigue. Fatigue & Fracture of Engineering Materials & Structures, 46(6), 2364-2373
Open this publication in new window or tab >>Formation of fine granular area in a non-defect matrix of austenitic stainless steel during very high cycle fatigue
2023 (English)In: Fatigue & Fracture of Engineering Materials & Structures, ISSN 8756-758X, E-ISSN 1460-2695, Vol. 46, no 6, p. 2364-2373Article in journal (Refereed) Published
Abstract [en]

A fine granular area, FGA, is a typical phenomenon observed at the very high cycle fatigue fracture crack origin with a subsurface defect in the material. The FGA has been widely investigated, and different mechanisms have been proposed. In this paper, the formation of FGA in a non-defect matrix of one austenitic steel during very high cycle fatigue was studied using a progressive stepwise load-increasing method and electron scanning microscopy/electron channeling contrast imaging (ECCI) technique. A nano rough surface area or FGA at the fatigue crack origin has been observed in the subsurface matrix without any defect. It is a new phenomenon. A mechanism was proposed using the dislocation plasticity theory. The formation of FGA in a non-defect matrix is a localized plasticity exhausting process by strain localization, grain fragmentation, stress concentration and nano crack initiation and propagation along low-angle grain boundaries. 

Place, publisher, year, edition, pages
John Wiley & Sons, 2023
Keywords
Austenitic stainless steel, Fatigue crack propagation, High-cycle fatigue, Low-cycle fatigue, Plasticity, Crack origins, Dislocation, Engineering materials, Engineering structures, Fatigue fracture, FGA, Grain-boundaries, matrix, Very-High-Cycle Fatigue, VHCF, Grain boundaries, grain boundary
National Category
Other Materials Engineering
Research subject
Materials Science
Identifiers
urn:nbn:se:kau:diva-94390 (URN)10.1111/ffe.14007 (DOI)000962457900001 ()2-s2.0-85151967482 (Scopus ID)
Available from: 2023-04-21 Created: 2023-04-21 Last updated: 2023-12-11Bibliographically approved
Javadzadeh Kalahroudi, F., Sadek, M., Krakhmalev, P., Berglund, T., Bergström, J. & Grehk, M. (2023). On the microstructure and high cycle fatigue of near-net shape PM-HIPed Inconel 625. Materials Science & Engineering: A, 886, Article ID 145671.
Open this publication in new window or tab >>On the microstructure and high cycle fatigue of near-net shape PM-HIPed Inconel 625
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2023 (English)In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 886, article id 145671Article in journal (Refereed) Published
Abstract [en]

This paper investigated the microstructure and fatigue behavior of PM-HIPed Inconel 625. The microstructure was composed of γ phase and (Mo, Nb) carbonitrides located mostly on prior particle boundaries. Despite the presence of these carbonitrides, the samples showed good tensile properties with high elongation. Two different surface conditions, pickled and machined, were used for high cycle fatigue testing under a four-point bending test. The results indicated that pickled samples had 6% lower fatigue strength (at 106 cycles) with three times higher standard deviation compared to the machined ones. Fatigue failure mechanisms were found to be dependent on surface conditions and showed different failure modes due to non-metallic oxide inclusions and surface defects in samples with machined and pickled surfaces, respectively. The effect of type, size, and location of defects, multiplicity of crack initiations, as well as surface roughness were analyzed and discussed.

Place, publisher, year, edition, pages
Elsevier, 2023
Keywords
Fatigue properties, Inconel 625, Mechanical properties, Microstructure, Surface roughness, Carbon nitride, Failure (mechanical), Fatigue testing, High-cycle fatigue, Niobium compounds, Surface defects, Fatigue behaviour, Four-point bending test, High cycle fatigue, High cycle fatigue testing, High elongation, Near net shape, Prior particle boundaries, Surface conditions
National Category
Manufacturing, Surface and Joining Technology
Research subject
Materials Engineering; Materials Science
Identifiers
urn:nbn:se:kau:diva-97121 (URN)10.1016/j.msea.2023.145671 (DOI)001080121200001 ()2-s2.0-85171337833 (Scopus ID)
Available from: 2023-10-20 Created: 2023-10-20 Last updated: 2024-01-29Bibliographically approved
Karimi Bakhshandi, R., Tkachuk, A., Sadek, M., Bergström, J. & Grehk, M. (2022). Failure analysis of two cylindrical impact pistons subjected to high velocity impacts in drilling applications. Engineering Failure Analysis, 140, Article ID 106623.
Open this publication in new window or tab >>Failure analysis of two cylindrical impact pistons subjected to high velocity impacts in drilling applications
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2022 (English)In: Engineering Failure Analysis, ISSN 1350-6307, E-ISSN 1873-1961, Vol. 140, article id 106623Article in journal (Refereed) Published
Abstract [en]

Top hammer drilling is a common method to drill holes in rock formations in mining and civil engineering applications. Failure of drilling machine components has a significant impact on the cost and period of the operation. Internal components of percussive hammers experience extreme loading conditions during their service life. The focus of the present case study is to characterize failure mechanisms of two cylindrical impact pistons subjected to impact loading. The investi-gated components were manufactured from two different steel grades, a surface hardened low alloyed high strength steel and a through hardened cold work tool steel.Failure of both pistons started with degradation of the impact surfaces in term of cavitation erosion and localized surface fatigue phenomena. Subsequently, chipping and removal of material from impact surfaces resulted in formation of semi-spherical holes and craters on both surfaces.Radial and hoop cracks started to develop from cavities on the impact surface. The radial cracks then propagated parallel to the impacting surface in the longitudinal direction of the piston. Once the cracks formed at the impact surface, the damage was controlled by impact fa-tigue. Fatigue beach marks were identified on the fracture surface of failed component.

Place, publisher, year, edition, pages
Elsevier, 2022
Keywords
Impact loading, Fatigue fracture, Wear, Wave mechanics, Cavitation erosion
National Category
Applied Mechanics
Research subject
Materials Science
Identifiers
urn:nbn:se:kau:diva-91553 (URN)10.1016/j.engfailanal.2022.106623 (DOI)000834091000002 ()2-s2.0-85134658247 (Scopus ID)
Funder
Knowledge Foundation, 20150090; 20190033
Available from: 2022-08-22 Created: 2022-08-22 Last updated: 2022-11-02Bibliographically approved
Javadzadeh Kalahroudi, F., Chantziara, K., Sadek, M., Lin, F., Maistro, G., Anantha, K. H., . . . Grehk, M. (2022). High-Nitrogen PM Tool Steel: A Comparison Of Microstructure And Mechanical Properties Of As-HIPed And HIPed Followed By Hot Working. In: World PM 2022 Congress Proceedings: . Paper presented at World PM 2022 Congress and Exhibition, Lyon, France, October 9-13, 2023.. European Powder Metallurgy Association (EPMA)
Open this publication in new window or tab >>High-Nitrogen PM Tool Steel: A Comparison Of Microstructure And Mechanical Properties Of As-HIPed And HIPed Followed By Hot Working
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2022 (English)In: World PM 2022 Congress Proceedings, European Powder Metallurgy Association (EPMA) , 2022Conference paper, Published paper (Other academic)
Abstract [en]

High-nitrogen-chromium alloyed powder metallurgy (PM) tool steels offer many attractive features including high strength and corrosion resistance. The PM route offers various advantages such as advanced alloy composition, high homogeneity, and well-defined size distribution of hard phase particles. This study presents microstructure and mechanical properties of a PM Cr-Mo-V-N alloy. The conventional manufacturing route for this alloy is hot isostatic pressing (HIP) followed by hot working. To investigate the possibility of near-net-shape manufacturing, a comprehensive comparison of the performance was made between steels produced by as-HIPed and HIPed followed by hot working. Both steel types were heat treated in the same way to obtain martensitic matrix with limited retained austenite. In the present investigation, microstructure and phase analyses were performed by X-ray diffraction and scanning electron microscopy. Mechanical tests were carried out by hardness measurements and tensile fatigue tests in the very high cycle fatigue regime using ultrasonic fatigue testing. 

Place, publisher, year, edition, pages
European Powder Metallurgy Association (EPMA), 2022
Keywords
Chromium alloys, Corrosion resistance, Corrosion resistant alloys, Fatigue testing, High strength alloys, High-cycle fatigue, Hot isostatic pressing, Microstructure, Molybdenum alloys, Molybdenum compounds, Scanning electron microscopy, Tensile testing, Tool steel, Ultrasonic testing, Advanced alloys, Alloy compositions, Alloyed powder, Hard phase, High homogeneity, High strength, Corrosion resistances, High-nitrogen, Microstructures, Mechanical properties, Phase particles; Size-distribution, Powder metallurgy
National Category
Metallurgy and Metallic Materials Other Materials Engineering
Research subject
Materials Engineering; Materials Science
Identifiers
urn:nbn:se:kau:diva-95204 (URN)2-s2.0-85160795406 (Scopus ID)9781899072552 (ISBN)
Conference
World PM 2022 Congress and Exhibition, Lyon, France, October 9-13, 2023.
Funder
Knowledge Foundation, 20190033
Available from: 2023-06-12 Created: 2023-06-12 Last updated: 2024-02-07Bibliographically approved
Mussa, A., Krakhmalev, P. & Bergström, J. (2022). Wear mechanisms and wear resistance of austempered ductile iron in reciprocal sliding contact. Wear, 498-499, Article ID 204305.
Open this publication in new window or tab >>Wear mechanisms and wear resistance of austempered ductile iron in reciprocal sliding contact
2022 (English)In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 498-499, article id 204305Article in journal (Refereed) Published
Abstract [en]

Austempered ductile irons (ADIs) are used in applications commonly exposed to severe contact conditions, and as a consequence wear damage frequently followed by failure of components. Hence, wear resistance of the material governs the final life time of a component. In the present work, the sliding wear resistance of two ausferritic spheroidal graphite ductile irons ADI1 and ADI2 used commonly in mining and construction equipment was investigated. ADI1 and ADI2 were heat treated to a similar strength, the volume fraction of the carbon-rich austenite in ADI1 and ADI2 was around 30% and 16%, respectively, and they both contained 10 – 13% nodular graphite. The wear tests were performed using a slider-on-flat-surface (SOFS) tribometer. Case-hardened steel plates made of a high strength steel, 22NiCrMo12–F, were used as the counterface. The wear tests were conducted under lubricated sliding contact at normal loads of 50, 100, 200 and 300 N, and at each load level sliding at 100, 200 and 300 m. The friction force between contacting surfaces was continuously monitored during sliding. The lubrication used in the present investigation was a mineral-oil-based paste commonly used in applications where high frictional heating is generated. Wear mechanisms of the tested specimens were investigated by means of optical and scanning electron microscopy and X-ray diffraction, and the wear damage was quantified using a 3D-profile optical interferometer. The main wear mechanisms, severe plastic deformation and surface delamination, were discussed concerning test conditions and material properties. The ADI1 grade with the higher volume of carbon-rich austenite displayed better resistance to sliding wear at high normal loads. The higher normal loads promoted larger deformation at and beneath the contact surface and initiated austenite transformation into hard martensite. Thus, it was concluded that the increase of wear resistance in ADI1 was due to the formation of marteniste. On the other hand, the ADI2 grade with higher silicon content showed lower wear resistance at high normal loads. This was associated with cracking of the proeutectoid ferrite presented in ADI2.

Place, publisher, year, edition, pages
Elsevier, 2022
Keywords
Austenite, Construction equipment, Ductility, Friction, Graphite, High strength steel, Iron, Loads (forces), Scanning electron microscopy, Tribology, Wear of materials, Ausferrite, Austempered, Austempered ductile irons, Carbon rich, Normal loads, Sliding wear, Transformation induced plasticity, Transformation induced plasticity reciprocal contact, Wear damage, Wear mechanisms, Wear resistance
National Category
Materials Engineering Mechanical Engineering
Research subject
Materials Engineering
Identifiers
urn:nbn:se:kau:diva-89532 (URN)10.1016/j.wear.2022.204305 (DOI)000778621600001 ()2-s2.0-85126143538 (Scopus ID)
Available from: 2022-04-14 Created: 2022-04-14 Last updated: 2022-05-19Bibliographically approved
Mussa, A., Krakhmalev, P., Şelte, A. & Bergström, J. (2020). Development of a new PM tool steel for optimization of cold working of advanced high-strength steels. Metals, 10(10), Article ID 1326.
Open this publication in new window or tab >>Development of a new PM tool steel for optimization of cold working of advanced high-strength steels
2020 (English)In: Metals, ISSN 2075-4701, Vol. 10, no 10, article id 1326Article in journal (Refereed) Published
Abstract [en]

In the present study, Uddeholm Vancron SuperClean cold work tool steel was investigated concerning wear resistance and fatigue strength, using laboratory and semi-industrial tests. The Uddeholm Vancron SuperClean was designed with the help of ThermoCalc calculations to contain a high amount of a carbonitride phase, which was suggested to improve tribological performance of this tool steel. In order to investigate the tested steel, galling tests with a slider-on flat-surface tribotester and semi-industrial punching tests were performed on an advanced high-strength steel, CP1180HD. Uddeholm Vanadis 8 SuperClean containing only a carbide phase and Uddeholm Vancron 40 containing a mixture of carbides and carbonitrides were also tested to compare the performance of the tool steels. The microstructure and wear mechanisms were characterized with scanning electron microscopy. It was found that the carbonitrides presented in Uddeholm Vancron SuperClean improved its resistance to material transfer and galling. Semi-industrial punching tests also confirmed that Uddeholm Vancron SuperClean cold work tool steel also possesses enhanced resistance to chipping and fatigue crack nucleation, which confirms the beneficial role of the carbonitride phase in wear resistance of cold work tool steel.

Keywords
Vancron SuperClean, cold work tool steels, advanced high-strength steels, sliding wear, galling, punching and chipping
National Category
Metallurgy and Metallic Materials Manufacturing, Surface and Joining Technology
Research subject
Materials Engineering; Materials Science
Identifiers
urn:nbn:se:kau:diva-81009 (URN)10.3390/met10101326 (DOI)000586120400001 ()2-s2.0-85092028746 (Scopus ID)
Available from: 2020-10-22 Created: 2020-10-22 Last updated: 2022-04-14Bibliographically approved
Sadek, M., Bergström, J., Hallbäck, N., Burman, C., Elvira, R. & Escauriaza, B. (2020). Fatigue Strength and Fracture Mechanisms in the Very-High-Cycle-Fatigue Regime of Automotive Steels. Steel Research International, 91(8), Article ID 2000060.
Open this publication in new window or tab >>Fatigue Strength and Fracture Mechanisms in the Very-High-Cycle-Fatigue Regime of Automotive Steels
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2020 (English)In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 91, no 8, article id 2000060Article in journal (Refereed) Published
Abstract [en]

Very-high-cycle-fatigue (VHCF) strength properties are of interest to several technical applications assessed globally at different laboratories with long-life fatigue testing capabilities. Also, VHCF failure mechanisms are a scientific topic with remaining open research questions. Herein, three automotive bar grade steels are studied with respect to VHCF strength and initiation mechanisms. A microalloyed ferritic-pearlitic steel (38MnSiV5, 870 MPa tensile strength), a quenched and tempered martensitic steel (50CrV4, 1410 MPa tensile strength), and a carburizing steel (16MnCr5, 1180 MPa core structure tensile strength) are studied to reveal characteristics regarding initiation and VHCF failure mechanisms. A 20 kHz ultrasonic fatigue testing instrument is used to obtain fatigue lives up to and above 10(9) load cycles in uniaxial loading. Hour-glass specimens, smooth or notched, are tested at R = -1 and R = 0.1. Fatigue strength and stress life (SN)-diagram data are achieved, and crack initiation and growth mechanisms are studied using primarily field-emission gun-scanning electron microscopy (FEG-SEM). Fatigue strengths are explained by a modified life-dependent Murakami-expression, the Haigh diagram, and notch sensitivity. Interior and surface crack initiations by surface defects, triple points, and inclusions are found. The fine granular area (FGA) to fish-eye crack growth transition conditions are explored and schematic descriptions are given.

Place, publisher, year, edition, pages
WILEY-V C H VERLAG GMBH, 2020
Keywords
automotive steels, fish eyes, initiation mechanisms, stress life-curve, very high cycle fatigue
National Category
Metallurgy and Metallic Materials Materials Engineering
Research subject
Materials Science; Materials Engineering
Identifiers
urn:nbn:se:kau:diva-78092 (URN)10.1002/srin.202000060 (DOI)000534036300001 ()
Available from: 2020-06-12 Created: 2020-06-12 Last updated: 2022-05-25Bibliographically approved
Mussa, A., Krakhmalev, P. & Bergström, J. (2020). Sliding wear and fatigue cracking damage mechanisms in reciprocal and unidirectional sliding of high-strength steels in dry contact. Wear, 444, Article ID 203119.
Open this publication in new window or tab >>Sliding wear and fatigue cracking damage mechanisms in reciprocal and unidirectional sliding of high-strength steels in dry contact
2020 (English)In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 444, article id 203119Article in journal (Refereed) Published
Abstract [en]

Rock drill components operate under tough contact conditions during rock drilling. Reciprocal and unidirectional motion under high contact stresses are the common contact conditions between interconnected components. It will result in component damage and often the observed surface damage of rock drill tools is due to wear and fatigue cracks. Nevertheless, the effects of the properties and structure of the mating materials on tribological performance, is not fully understood. The present study is dedicated to simulation and investigation of the wear mechanisms observed in reciprocal and unidirectional sliding of high strength steels for rock drill components. A high strength martensitic steel, 22NiCrMo12–F, commonly used in rock drills was tested in self-mating contact. Wear mechanisms were investigated by means of electron microscopy and wear damage was quantified by a 3D optical interferometer. Total damage, as a result of adhesive wear, severe plastic deformation and nucleation and propagation of fatigue cracks, was discussed in relation to test conditions and material properties. It was observed that the coefficient of friction decreased with increasing normal load. Moreover, the results showed that the type of motion had a significant influence on the worn volume and crack nucleation of the specimens in sliding contact. In addition, the reciprocal motion resulted in higher wear than unidirectional motion under the same test conditions.

Keywords
Fatigue cracks, High strength steel, Reciprocal sliding contact, Rock drill rods, Sliding wear and plastic deformation, Adhesives, Cracks, Fatigue crack propagation, Fatigue damage, Friction, Infill drilling, Nucleation, Plastic deformation, Rock drilling, Rock drills, Rocks, Structural panels, Tribology, Coefficient of frictions, High strength martensitic steels, Optical interferometer, Severe plastic deformations, Sliding contacts, Sliding wear, Tribological performance
National Category
Materials Engineering
Research subject
Materials Engineering
Identifiers
urn:nbn:se:kau:diva-76487 (URN)10.1016/j.wear.2019.203119 (DOI)000513001800003 ()2-s2.0-85075419083 (Scopus ID)
Available from: 2020-01-23 Created: 2020-01-23 Last updated: 2022-04-14Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0001-6029-2613

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