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24 pages, 9738 KiB

Open AccessEditor’s ChoiceArticle

Mechanical Behavior of Austenitic Steel under Multi-Axial Cyclic Loading

by Abhishek Biswas, Dzhem Kurtulan, Timothy Ngeru, Abril Azócar Guzmán, Stefanie Hanke and Alexander Hartmaier

Materials 2023, 16(4), 1367; https://doi.org/10.3390/ma16041367 - 6 Feb 2023

Cited by 2 | Viewed by 2193

Abstract

Low-nickel austenitic steel is subjected to high-pressure torsion fatigue (HPTF) loading, where a constant axial compression is overlaid with a cyclic torsion. The focus of this work lies on investigating whether isotropic J2 plasticity or crystal plasticity can describe the mechanical behavior during [...] Read more.

Low-nickel austenitic steel is subjected to high-pressure torsion fatigue (HPTF) loading, where a constant axial compression is overlaid with a cyclic torsion. The focus of this work lies on investigating whether isotropic J2 plasticity or crystal plasticity can describe the mechanical behavior during HPTF loading, particularly focusing on the axial creep deformation seen in the experiment. The results indicate that a J2 plasticity model with an associated flow rule fails to describe the axial creep behavior. In contrast, a micromechanical model based on an empirical crystal plasticity law with kinematic hardening described by the Ohno–Wang rule can match the HPTF experiments quite accurately. Hence, our results confirm the versatility of crystal plasticity in combination with microstructural models to describe the mechanical behavior of materials under reversing multiaxial loading situations. Full article

(This article belongs to the Special Issue Fatigue and Fracture of Metals and Alloys: Numerical and Experimental Study)

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13 pages, 7967 KiB

Open AccessArticle

Effects of Micro-Shot Peening on the Fatigue Strength of Anodized 7075-T6 Alloy

by Chih-Hang Su, Tai-Cheng Chen, Yi-Shiun Ding, Guan-Xun Lu and Leu-Wen Tsay

Materials 2023, 16(3), 1160; https://doi.org/10.3390/ma16031160 - 29 Jan 2023

Cited by 9 | Viewed by 2241

Abstract

Micro-shot peening under two Almen intensities was performed to increase the fatigue endurance limit of anodized AA 7075 alloy in T6 condition. Compressive residual stress (CRS) and a nano-grained structure were present in the outermost as-peened layer. Microcracks in the anodized layer obviously [...] Read more.

Micro-shot peening under two Almen intensities was performed to increase the fatigue endurance limit of anodized AA 7075 alloy in T6 condition. Compressive residual stress (CRS) and a nano-grained structure were present in the outermost as-peened layer. Microcracks in the anodized layer obviously abbreviated the fatigue strength/life of the substrate. The endurance limit of the anodized AA 7075 was lowered to less than 200 MPa. By contrast, micro-shot peening increased the endurance limit of the anodized AA 7075 to above that of the substrate (about 300 MPa). Without anodization, the fatigue strength of the high peened (HP) specimen fluctuated; this was the result of high surface roughness of the specimen, as compared to that of the low peened (LP) one. Pickling before anodizing was found to erode the outermost peened layer, which caused a decrease in the positive effect of peening. After anodization, the HP sample had a greater fatigue strength/endurance limit than that of the LP one. The fracture appearance of an anodized fatigued sample showed an observable ring of brittle fracture. Fatigue cracks present in the brittle coating propagated directly into the substrate, significantly damaging the fatigue performance of the anodized sample. The CRS and the nano-grained structure beneath the anodized layer accounted for a noticeable increase in resistance to fatigue failure of the anodized micro-shot peened specimen. Full article

(This article belongs to the Special Issue Fatigue and Fracture of Metals and Alloys: Numerical and Experimental Study)

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17 pages, 6472 KiB

Open AccessArticle

Thermo-Mechanical Fatigue Behavior and Resultant Microstructure Evolution in Al-Si 319 and 356 Cast Alloys

by Kun Liu, Shuai Wang, Lei Pan and X.-Grant Chen

Materials 2023, 16(2), 829; https://doi.org/10.3390/ma16020829 - 15 Jan 2023

Cited by 7 | Viewed by 2078

Abstract

The out-of-phase thermo-mechanical fatigue (TMF) behavior of the two Al-Si cast alloys most widely used for engine applications (319 and 356) were investigated under temperature cycling (60–300 °C) and various strain amplitudes (0.1–0.6%). The relationship between the microstructural evolution and TMF behavior was [...] Read more.

The out-of-phase thermo-mechanical fatigue (TMF) behavior of the two Al-Si cast alloys most widely used for engine applications (319 and 356) were investigated under temperature cycling (60–300 °C) and various strain amplitudes (0.1–0.6%). The relationship between the microstructural evolution and TMF behavior was closely studied. Both alloys exhibited asymmetric hysteresis loops with a higher portion in the tensile mode during TMF cycling. The two alloys showed cyclic softening behavior with regard to the maximum stress, but an earlier inflection of cyclic stress was found in the 356 alloy. The TMF lifetime of the 319 alloy was generally longer than that of the 356 alloy, especially at higher strain amplitudes. All the precipitates (β′-MgSi in 356 and θ′-Al₂Cu in 319) coarsened during the TMF tests; however, the coarsening rate per cycle in the 356 alloy was significantly higher than that in the 319 alloy. An energy-based model was applied to predict the fatigue lifetime, which corresponded well with the experimental data. However, the parameters in the model varied with the alloys, and the 356 alloy exhibited a lower fatigue damage capacity and a higher fatigue damage exponent. Full article

(This article belongs to the Special Issue Fatigue and Fracture of Metals and Alloys: Numerical and Experimental Study)

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24 pages, 6721 KiB

Open AccessArticle

Statistical Characterization of Strain-Controlled Low-Cycle Fatigue Behavior of Structural Steels and Aluminium Material

by Žilvinas Bazaras and Vaidas Lukoševičius

Materials 2022, 15(24), 8808; https://doi.org/10.3390/ma15248808 - 9 Dec 2022

Cited by 1 | Viewed by 1490

Abstract

Probabilistic evaluation of the resistance to low-cycle deformation and failure of the critical components in the equipment used in the energy, engineering, metallurgy, chemical, shipbuilding, and other industries is of primary importance with the view towards their secure operation, in particular, given the [...] Read more.

Probabilistic evaluation of the resistance to low-cycle deformation and failure of the critical components in the equipment used in the energy, engineering, metallurgy, chemical, shipbuilding, and other industries is of primary importance with the view towards their secure operation, in particular, given the high level of cyclic loading acting on the equipment during its operation. Until recently, systematic probabilistic evaluation has been generally applied to the results of statistical and fatigue investigations. Very few investigations applying this approach to the low-cycle domain. The present study aims to substantiate the use of probabilistic calculation in the low-cycle domain by systematic probabilistic evaluation of the diagrams of cyclic elastoplastic deformation and durability of the materials representing the major types of cyclic properties (hardening, softening, stabilization) and investigation of the correlation relationships between mechanical properties and cyclic deformation and failure parameters. The experimental methodology that includes the calculated design of the probabilistic fatigue curves is also developed and the curves are compared to the results of the experiment. Probabilistic values of mechanical characteristics were determined and calculated low-cycle fatigue curves corresponding to different failure probabilities, to assess them from the probabilistic perspective. A comparison of low-cycle fatigue curves has shown that the durability curves generated for some materials using analytical expressions are not accurate. According to the analysis of the relative values of experimental probabilities of low-cycle fatigue curves, the use of analytical expressions to build the curves can lead to a significant error. The results obtained allow for the revision of the load bearing capacity and life of the structural elements subjected to cyclic elastoplastic loading in view of the potential scattering of mechanical properties and resistance parameters to low-cycle deformation and failure. In addition, the results enable determination of the scatter tolerances, depending on the criticality of the part or structure. Full article

(This article belongs to the Special Issue Fatigue and Fracture of Metals and Alloys: Numerical and Experimental Study)

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15 pages, 9092 KiB

Open AccessArticle

Further Investigations and Parametric Analysis of Microstructural Alterations under Rolling Contact Fatigue

by Muhammad Usman Abdullah and Zulfiqar Ahmad Khan

Materials 2022, 15(22), 8072; https://doi.org/10.3390/ma15228072 - 15 Nov 2022

Cited by 2 | Viewed by 1829

Abstract

Bearing elements under rolling contact fatigue (RCF) exhibit microstructural features, known as white etching bands (WEBs) and dark etching regions (DERs). The formation mechanism of these microstructural features has been questionable and therefore warranted this study to gain further understanding. Current research describes [...] Read more.

Bearing elements under rolling contact fatigue (RCF) exhibit microstructural features, known as white etching bands (WEBs) and dark etching regions (DERs). The formation mechanism of these microstructural features has been questionable and therefore warranted this study to gain further understanding. Current research describes mechanistic investigations of standard AISI 52100 bearing steel balls subjected to RCF testing under tempering conditions. Subsurface analyses of RCF-tested samples at tempering conditions have indicated that the microstructural alterations are progressed with subsurface yielding and primarily dominated by thermal tempering. Furthermore, bearing balls are subjected to static load tests in order to evaluate the effect of lattice deformation. It is suggested from the comparative analyses that a complete rolling sequence with non-proportional stress history is essential for the initiation and progression of WEBs, supported by the combination of carbon flux, assisted by dislocation and thermally activated carbon diffusion. These novel findings will lead to developing a contemporary and new-fangled prognostic model applied to microstructural alterations. Full article

(This article belongs to the Special Issue Fatigue and Fracture of Metals and Alloys: Numerical and Experimental Study)

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21 pages, 7819 KiB

Open AccessArticle

An Investigation of the Contact Fatigue Characteristics of an RV Reducer Crankshaft, Considering the Hardness Gradients and Initial Residual Stress

by Xin Li, Wen Shao, Jinyuan Tang, Han Ding and Weihua Zhou

Materials 2022, 15(21), 7850; https://doi.org/10.3390/ma15217850 - 7 Nov 2022

Cited by 10 | Viewed by 3486

Abstract

The crankshaft is one of the core components of a Rotate Vector (RV) reducer. The fatigue life of the RV reducer is severely hindered by fatigue failure on the eccentric cylindrical surface of the crankshaft. The hardness gradients and residual stress in the [...] Read more.

The crankshaft is one of the core components of a Rotate Vector (RV) reducer. The fatigue life of the RV reducer is severely hindered by fatigue failure on the eccentric cylindrical surface of the crankshaft. The hardness gradients and residual stress in the crankshaft, associated with machining operations, exert an enormous impact on the rolling contact fatigue (RCF). In this work, a finite element method (FEM)-based three-dimensional elasto-plastic contact model is established to calculate the stress–strain field by taking hardness gradients and initial residual stress into account. The RCF characteristics of an RV reducer crankshaft is investigated by applying modified Fatemi–Socie (FS) multiaxial fatigue criterion. The results indicate that initial residual stress plays an influential role in the fatigue damage by altering the distribution of the maximum normal stress near the contact surface. The modified FS fatigue criterion could better consider the effect of initial residual stress and the shear stress, which significantly improves the prediction accuracy of the contact fatigue life model. The contact fatigue performance could be considerably improved by designing appropriate shot peening parameters to obtain optimized residual stress distribution. Therefore, the technique presented may serve as an important guideline for the anti-fatigue design of an RV reducer crankshaft. Full article

(This article belongs to the Special Issue Fatigue and Fracture of Metals and Alloys: Numerical and Experimental Study)

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12 pages, 6997 KiB

Open AccessArticle

Influence of Creep Damage on the Fatigue Life of P91 Steel

by Stanisław Mroziński, Zbigniew Lis and Halina Egner

Materials 2022, 15(14), 4917; https://doi.org/10.3390/ma15144917 - 14 Jul 2022

Cited by 1 | Viewed by 1903

Abstract

The following paper presents the results of tests on samples made of P91 steel under the conditions of simultaneously occurring fatigue and creep at a temperature of 600 °C. The load program consisted of symmetrical fatigue cycles with tensile dwell times to introduce [...] Read more.

The following paper presents the results of tests on samples made of P91 steel under the conditions of simultaneously occurring fatigue and creep at a temperature of 600 °C. The load program consisted of symmetrical fatigue cycles with tensile dwell times to introduce creep. Static load (creep) was carried out by stopping the alternating load at the maximum value of the alternating stress. The tests were carried out for two load dwell times, 5 s and 30 s. A comparative analysis of the test results of fatigue load with a dwell time on each cycle confirmed that creep accompanying the variable load causes a significant reduction in sample durability. It was shown in the paper that regarding the creep influence in the linear fatigue damage summation approach, it is possible to improve the compliance of the fatigue life predictions with the experimental results. Full article

(This article belongs to the Special Issue Fatigue and Fracture of Metals and Alloys: Numerical and Experimental Study)

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21 pages, 1685 KiB

Open AccessArticle

Robust Determination of Fatigue Crack Propagation Thresholds from Crack Growth Data

by Josef Arthur Schönherr, Larissa Duarte, Mauro Madia, Uwe Zerbst, Max Benedikt Geilen, Marcus Klein and Matthias Oechsner

Materials 2022, 15(14), 4737; https://doi.org/10.3390/ma15144737 - 6 Jul 2022

Cited by 5 | Viewed by 2223

Abstract

The robust determination of the threshold against fatigue crack propagation

Δ K_{th}

is of paramount importance in fracture mechanics based fatigue assessment procedures. The standards ASTM E647 and ISO 12108 introduce operational definitions of

Δ K_{th}

based on the crack propagation [...] Read more.

The robust determination of the threshold against fatigue crack propagation

Δ K_{th}

is of paramount importance in fracture mechanics based fatigue assessment procedures. The standards ASTM E647 and ISO 12108 introduce operational definitions of

Δ K_{th}

based on the crack propagation rate

d a / d N

and suggest linear fits of logarithmic

Δ K

–

d a / d N

test data to calculate

Δ K_{th}

. Since these fits typically suffer from a poor representation of the actual curvature of the crack propagation curve, a method for evaluating

Δ K_{th}

using a nonlinear function is proposed. It is shown that the proposed method reduces the artificial conservativeness induced by the evaluation method as well as the susceptibility to scatter in test data and the influence of test data density. Full article

(This article belongs to the Special Issue Fatigue and Fracture of Metals and Alloys: Numerical and Experimental Study)

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23 pages, 4696 KiB

Open AccessArticle

Experiment and Theoretical Investigation on Fatigue Life Prediction of Fracturing Pumpheads Based on a Novel Stress-Field Intensity Approach

by Yun Zeng, Meiqiu Li, Han Wu, Ning Li and Yang Zhou

Materials 2022, 15(13), 4413; https://doi.org/10.3390/ma15134413 - 22 Jun 2022

Cited by 1 | Viewed by 1789

Abstract

Fracturing pumpheads are typical pressure vessels that experience frequent fatigue failure under the effect of notches in their cross-bore. To enhance the fatigue life of fracturing pumpheads, the study of the notch effect is indispensable and important to establish a reliable mathematical model [...] Read more.

Fracturing pumpheads are typical pressure vessels that experience frequent fatigue failure under the effect of notches in their cross-bore. To enhance the fatigue life of fracturing pumpheads, the study of the notch effect is indispensable and important to establish a reliable mathematical model to predict their fatigue life. In the present paper, two novel fatigue life prediction models are proposed for notched specimens. In these models, two new geometric fatigue failure regions are defined to improve the weight function. Finally, the elaborated novel stress-field intensity approach was applied to three different types of notched specimens. Experiment results indicate that the new SFI approach achieves 47.82%, 39.48%, and 31.85% higher prediction accuracy than the traditional SFI approach, respectively. It was found that the modified SFI approach provided better predictions than the traditional SFI approach and the TCD method. The II-th novel SFI approach had the highest accuracy, and the I-th novel SFI approach was more suitable for sharply notched specimens. Full article

(This article belongs to the Special Issue Fatigue and Fracture of Metals and Alloys: Numerical and Experimental Study)

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19 pages, 12194 KiB

Open AccessArticle

The Influence of Heat Treatment on the Mechanical Properties and Corrosion Resistance of the Ultrafine-Grained AA7075 Obtained by Hydrostatic Extrusion

by Marta Orłowska, Ewa Ura-Bińczyk, Lucjan Śnieżek, Paweł Skudniewski, Mariusz Kulczyk, Bogusława Adamczyk-Cieślak and Kamil Majchrowicz

Materials 2022, 15(12), 4343; https://doi.org/10.3390/ma15124343 - 20 Jun 2022

Cited by 11 | Viewed by 2111

Abstract

In this paper, the corrosion resistance and mechanical properties of the 7075 aluminum alloy are studied. The alloy was deformed by hydrostatic extrusion and then aged both naturally and artificially. Results are compared with those of coarse-grained material subjected to T6 heat treatment. [...] Read more.

In this paper, the corrosion resistance and mechanical properties of the 7075 aluminum alloy are studied. The alloy was deformed by hydrostatic extrusion and then aged both naturally and artificially. Results are compared with those of coarse-grained material subjected to T6 heat treatment. The aim of the research is to find the optimal correlation between the mechanical properties and the corrosion resistance of the alloy. To this end, static tensile tests with subsequent fractography, open circuit potential, and potentiodynamic polarization tests in 0.05 M NaCl were conducted. Obtained results show that a combination of precipitate hardening and a deformed microstructure leads to increased mechanical strength with high anisotropy due to the presence of fibrous grains. Plastic deformation increases susceptibility to corrosion due to the increased number of grain boundaries, which act as paths along that corrosion propagates. However, further artificial aging incurs a positive effect on corrosion resistance due to changes in the chemical composition of the matrix as a result of the precipitation process. Full article

(This article belongs to the Special Issue Fatigue and Fracture of Metals and Alloys: Numerical and Experimental Study)

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14 pages, 7011 KiB

Open AccessArticle

Mechanical Properties Analysis of Explosive Welded Sheet of AA2519-Ti6Al4V with Interlayer of AA1050 Subjected to Heat-Treatment

by Ireneusz Szachogłuchowicz, Lucjan Śnieżek and Tomasz Ślęzak

Materials 2022, 15(11), 4023; https://doi.org/10.3390/ma15114023 - 6 Jun 2022

Cited by 4 | Viewed by 2110

Abstract

The paper presents results of investigations of welding sheets of AA2519-Ti6Al4V, a difficult-to-joint components materials, produced by explosive welding with a thin technological interlayer of AA1050. The joining process leads to the formation of intermetalics in the vicinity of joint and generates significant [...] Read more.

The paper presents results of investigations of welding sheets of AA2519-Ti6Al4V, a difficult-to-joint components materials, produced by explosive welding with a thin technological interlayer of AA1050. The joining process leads to the formation of intermetalics in the vicinity of joint and generates significant residual stresses. In the next step the laminate was subjected to a heat treatment process in order to improve the mechanical properties by precipitation hardening. This treatment should not be carried out before welding because of negative influence on a ductility of the aluminum alloy. Material in this state was subjected to the tests of chemical composition, microstructure, and microhardness. A tensile test was carried out with accompanying strain analysis by the digital image correlation (DIC) method. Moreover, the residual stresses were determined which were measured by using two methods, the X-ray diffraction and the hole drilling. This approach made it possible to measure the residual stresses both in the plane parallel to the surface and in the cross section of the laminate. Full article

(This article belongs to the Special Issue Fatigue and Fracture of Metals and Alloys: Numerical and Experimental Study)

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18 pages, 12634 KiB

Open AccessArticle

Comparison of Hydrogen Embrittlement Susceptibility of Different Types of Advanced High-Strength Steels

by Sangwon Cho, Geon-Il Kim, Sang-Jin Ko, Jin-Seok Yoo, Yeon-Seung Jung, Yun-Ha Yoo and Jung-Gu Kim

Materials 2022, 15(9), 3406; https://doi.org/10.3390/ma15093406 - 9 May 2022

Cited by 11 | Viewed by 2828

Abstract

This study investigated the hydrogen embrittlement (HE) characteristics of advanced high-strength steels (AHSSs). Two different types of AHSSs with a tensile strength of 1.2 GPa were investigated. Slow strain rate tests (SSRTs) were performed under various applied potentials (E_app) to identify [...] Read more.

This study investigated the hydrogen embrittlement (HE) characteristics of advanced high-strength steels (AHSSs). Two different types of AHSSs with a tensile strength of 1.2 GPa were investigated. Slow strain rate tests (SSRTs) were performed under various applied potentials (E_app) to identify the mechanism with the greatest effect on the embrittlement of the specimens. The SSRT results revealed that, as the E_app increased, the elongation tended to increase, even when a potential exceeding the corrosion potential was applied. Both types of AHSSs exhibited embrittled fracture behavior that was dominated by HE. The fractured SSRT specimens were subjected to a thermal desorption spectroscopy analysis, revealing that diffusible hydrogen was trapped mainly at the grain boundaries and dislocations (i.e., reversible hydrogen-trapping sites). The micro-analysis results revealed that the poor HE resistance of the specimens was attributed to the more reversible hydrogen-trapping sites. Full article

(This article belongs to the Special Issue Fatigue and Fracture of Metals and Alloys: Numerical and Experimental Study)

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15 pages, 11100 KiB

Open AccessArticle

Fatigue Fracture Analysis on 2524 Aluminum Alloy with the Influence of Creep-Aging Forming Processes

by Liyong Ma, Chi Liu, Minglei Ma, Zhanying Wang, Donghao Wu, Lijuan Liu and Mingxing Song

Materials 2022, 15(9), 3244; https://doi.org/10.3390/ma15093244 - 30 Apr 2022

Cited by 5 | Viewed by 2206

Abstract

The different creep-aging forming processes of 2524 aluminum alloy were taken as the research object, and the effects of creep-aging temperature and creep stress on the fatigue-crack propagation properties of the alloy were studied. The research results showed the following under the same [...] Read more.

The different creep-aging forming processes of 2524 aluminum alloy were taken as the research object, and the effects of creep-aging temperature and creep stress on the fatigue-crack propagation properties of the alloy were studied. The research results showed the following under the same sintering time of 9 h, at creep-aging temperatures of 100 °C, 130 °C, 160 °C, and 180 °C, respectively, with an increase in creep-aging temperature: the fatigue-crack propagation rate was promoted, the spacing of fatigue striations increased, and the sizes of dimples decreased while the number was enlarged; this proves that the fatigue property of the alloy was weakened. Compared with the specimens with creep deformation radii of 1000 mm and 1500 mm, the creep deformation stress was the smallest when the forming radius was 1800 mm, with a higher threshold value of fatigue-crack growth in the near-threshold region of fatigue-crack propagation (ΔK ≤ 8 MPa·m^1/2). Under the same fatigue cycle, the specimens under the action of larger creep stress endured a longer fatigue stable-propagation time and a faster fracture speed. Comparing the effect of creep-aging temperature and creep stress, the creep-aging temperature plays a dominant role in the fatigue-crack propagation of creep-aged 2524 aluminum alloy. Full article

(This article belongs to the Special Issue Fatigue and Fracture of Metals and Alloys: Numerical and Experimental Study)

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15 pages, 2642 KiB

Open AccessArticle

Effect of Strain Rate and Temperature on Tensile and Fracture Performance of AA2050-T84 Alloy

by Nagaraj Ekabote, Krishnaraja G. Kodancha, T. M. Yunus Khan and Irfan Anjum Badruddin

Materials 2022, 15(4), 1590; https://doi.org/10.3390/ma15041590 - 20 Feb 2022

Cited by 3 | Viewed by 2360

Abstract

AA2050-T84 alloy is widely used in primary structures of modern transport aircraft. AA2050-T84 is established as a low-density aluminum alloy with improved Young’s modulus, less anisotropy, and temperature-dependent mechanical properties. During flights, loading rate and temperature variation in aircraft engine subsequent parts are [...] Read more.

AA2050-T84 alloy is widely used in primary structures of modern transport aircraft. AA2050-T84 is established as a low-density aluminum alloy with improved Young’s modulus, less anisotropy, and temperature-dependent mechanical properties. During flights, loading rate and temperature variation in aircraft engine subsequent parts are commonly observed. The present work focuses on the effect of loading rate and temperature on tensile and fracture properties of the 50 mm thick (2-inch) AA2050-T84 alloy plate. Quasi-static strain rates of 0.01, 0.1, and 1 s⁻¹ at −20 °C, 24 °C and 200 °C are considered. Tensile test results revealed the sensitivity of mechanical properties towards strain rate variations for considered temperatures. The key tensile properties, yield, and ultimate tensile stresses were positive strain rate dependent. However, Young’s modulus and elongation showed negative strain rate dependency. Experimental fracture toughness tests exhibited the lower Plane Strain Fracture Toughness (K_IC) at −20 °C compared to 24 °C. Elastic numerical fracture analysis revealed that the crack driving and constraint parameters are positive strain rate dependent and maximum at −20 °C, if plotted and analyzed over the stress ratio. The current results concerning strain rates and temperatures will help in understanding the performance-related issues of AA2050-T84 alloy reported in aircraft applications. Full article

(This article belongs to the Special Issue Fatigue and Fracture of Metals and Alloys: Numerical and Experimental Study)

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20 pages, 11619 KiB

Open AccessArticle

Application of Operational Load Monitoring System for Fatigue Estimation of Main Landing Gear Attachment Frame of an Aircraft

by Michal Dziendzikowski, Artur Kurnyta, Piotr Reymer, Marcin Kurdelski, Sylwester Klysz, Andrzej Leski and Krzysztof Dragan

Materials 2021, 14(21), 6564; https://doi.org/10.3390/ma14216564 - 1 Nov 2021

Cited by 13 | Viewed by 2951

Abstract

In this paper, we present an approach to fatigue estimation of a Main Landing Gear (MLG) attachment frame due to vertical landing forces based on Operational Loads Monitoring (OLM) system records. In particular, the impact of different phases of landing and on ground [...] Read more.

In this paper, we present an approach to fatigue estimation of a Main Landing Gear (MLG) attachment frame due to vertical landing forces based on Operational Loads Monitoring (OLM) system records. In particular, the impact of different phases of landing and on ground operations and fatigue wear of the MLG frame is analyzed. The main functionality of the developed OLM system is the individual assessment of fatigue of the main landing gear node structure for Su-22UM3K aircraft due to standard and Touch-And-Go (T&G) landings. Furthermore, the system allows for assessment of stress cumulation in the main landing gear node structure during touchdown and allows for detection of hard landings. Determination of selected stages of flight, classification of different types of load cycles of the structure recorded by strain gauge sensors during standard full stop landings and taxiing are also implemented in the developed system. Based on those capabilities, it is possible to monitor and compare equivalents of landing fatigue wear between airplanes and landing fatigue wear across all flights of a given airplane, which can be incorporated into fleet management paradigms for the purpose of optimal maintenance of aircraft. In this article, a detailed description of the system and algorithms used for landing gear node fatigue assessment is provided, and the results obtained during the 3-year period of system operation for the fleet of six aircraft are delivered and discussed. Full article

(This article belongs to the Special Issue Fatigue and Fracture of Metals and Alloys: Numerical and Experimental Study)

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17 pages, 8198 KiB

Open AccessArticle

Analysis of the Failure Process of Elements Subjected to Monotonic and Cyclic Loading Using the Wierzbicki–Bai Model

by Urszula Janus-Galkiewicz and Jaroslaw Galkiewicz

Materials 2021, 14(21), 6265; https://doi.org/10.3390/ma14216265 - 21 Oct 2021

Cited by 2 | Viewed by 2058

Abstract

This article presents the results of a simulation in which smooth cylindrical and ring-notched samples were subjected to monotonic and fatigue loads in an ultra-short-life range, made of Inconel 718 super alloy. The samples displayed different behaviors as a result of different geometries [...] Read more.

This article presents the results of a simulation in which smooth cylindrical and ring-notched samples were subjected to monotonic and fatigue loads in an ultra-short-life range, made of Inconel 718 super alloy. The samples displayed different behaviors as a result of different geometries that introduced varying levels of stress triaxiality and loading methods. The simulations used the Wierzbicki–Bai model, which took into account the influence of stress tensors and stress-deviator invariants on the behavior of the material. The difference in the behaviors of the smoothed and notched specimens subjected to tensile and fatigue loads were identified and described. The numerical results were qualitatively supported by the results of the experiments presented in the literature. Full article

(This article belongs to the Special Issue Fatigue and Fracture of Metals and Alloys: Numerical and Experimental Study)

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15 pages, 8703 KiB

Open AccessArticle

Effect of Steel-Cutting Technology on Fatigue Strength of Steel Structures: Tests and Analyses

by Sławomir Rowiński

Materials 2021, 14(20), 6097; https://doi.org/10.3390/ma14206097 - 15 Oct 2021

Cited by 2 | Viewed by 1954

Abstract

This paper presents the results of comparative fatigue tests carried out on steel S355J2N specimens cut out using different cutting methods, i.e., plasma cutting, water jet cutting, and oxyacetylene cutting. All the specimens were subjected to cyclic loading from which appropriate S-N curves [...] Read more.

This paper presents the results of comparative fatigue tests carried out on steel S355J2N specimens cut out using different cutting methods, i.e., plasma cutting, water jet cutting, and oxyacetylene cutting. All the specimens were subjected to cyclic loading from which appropriate S-N curves were obtained. Furthermore, face-of-cut hardness and roughness measurements were carried out to determine the effect of the cutting method on the fatigue strength of the tested steel. The fatigue strength results were compared with the standard S-N fatigue curves. The fatigue strength of the specimens cut out with oxyacetylene was found to be higher than that of the specimens cut out with plasma even though the surface roughness after cutting with plasma was smaller than in the case of the other cutting technology. This was due to the significant effect of material hardening in the heat-affected zones. The test results indicate that, in comparison with the effect of the cutting technology, the surface condition of the specimens has a relatively small effect on their fatigue strength. Full article

(This article belongs to the Special Issue Fatigue and Fracture of Metals and Alloys: Numerical and Experimental Study)

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16 pages, 9134 KiB

Open AccessArticle

Experimental Study on Forged TC4 Titanium Alloy Fatigue Properties under Three-Point Bending and Life Prediction

by Bohan Wang, Li Cheng and Dongchun Li

Materials 2021, 14(18), 5329; https://doi.org/10.3390/ma14185329 - 15 Sep 2021

Cited by 6 | Viewed by 2460

Abstract

Ultrasonic fatigue tests of TC4 titanium alloy equiaxed I, II and bimodal I, II obtained by different forging processes were carried out in the range from 10⁵ to 10⁹ cycles using 20 kHz three-point bending. The results showed that the S-N [...] Read more.

Ultrasonic fatigue tests of TC4 titanium alloy equiaxed I, II and bimodal I, II obtained by different forging processes were carried out in the range from 10⁵ to 10⁹ cycles using 20 kHz three-point bending. The results showed that the S-N curves had different shapes, there was no traditional fatigue limit, and the bimodal I had the best comprehensive fatigue performance. The fracture morphology was analyzed by SEM, and it was found that the fatigue cracks originated from the surface or subsurface facets, showing a transgranular quasi-cleavage fracture mechanism. EDS analysis showed that the facets were formed by the cleavage of primary α grains, and the fatigue cracks originated from the primary α grain preferred textures, rather than the primary α grain clusters. From the microstructure perspective, the reasons for better equiaxed high-cycle-fatigue properties and better bimodal ultra-high-cycle-fatigue properties were analyzed. The bimodal I fatigue life prediction based on energy was also completed, and the prediction curve was basically consistent with the experimental data. Full article

(This article belongs to the Special Issue Fatigue and Fracture of Metals and Alloys: Numerical and Experimental Study)

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Void-Induced Ductile Fracture of Metals: Experimental Observations

by Wiktor Wciślik and Sebastian Lipiec

Materials 2022, 15(18), 6473; https://doi.org/10.3390/ma15186473 - 18 Sep 2022

Cited by 28 | Viewed by 4358

Abstract

The paper presents a literature review on the development of microvoids in metals, leading to ductile fracture associated with plastic deformation, without taking into account the cleavage mechanism. Particular emphasis was placed on the results of observations and experimental studies of the characteristics [...] Read more.

The paper presents a literature review on the development of microvoids in metals, leading to ductile fracture associated with plastic deformation, without taking into account the cleavage mechanism. Particular emphasis was placed on the results of observations and experimental studies of the characteristics of the phenomenon itself, without in-depth analysis in the field of widely used FEM modelling. The mechanism of void development as a fracture mechanism is presented. Observations of the nucleation of voids in metals from the turn of the 1950s and 1960s to the present day were described. The nucleation mechanisms related to the defects of the crystal lattice as well as those resulting from the presence of second-phase particles were characterised. Observations of the growth and coalescence of voids were presented, along with the basic models of both phenomena. The modern research methods used to analyse changes in the microstructure of the material during plastic deformation are discussed. In summary, it was indicated that understanding the microstructural phenomena occurring in deformed material enables the engineering of the modelling of plastic fracture in metals. Full article

(This article belongs to the Special Issue Fatigue and Fracture of Metals and Alloys: Numerical and Experimental Study)

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