Journal articles: 'Infinite fatigue life'

1

Bathias. "There is no infinite fatigue life in metallic materials." Fatigue & Fracture of Engineering Materials & Structures 22, no. 7 (1999): 559–65. http://dx.doi.org/10.1046/j.1460-2695.1999.00183.x.

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Shen, Jian, Xiao Yun Liu, and Lang Wu. "Fatigue Performance of Concrete with Pre-Cracks in Tension-Compression Cycles." Applied Mechanics and Materials 584-586 (July 2014): 1054–61. http://dx.doi.org/10.4028/www.scientific.net/amm.584-586.1054.

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A tension-compression cycle fatigue test was performed in order to study the fatigue property of C50 concrete with pre-cracks in cyclic loading. The stress ratio was-1 and the amplitude was 0.2 MPa ~1.30 MPa. The results show that the modified coefficient of fatigue strength is 0.198~0.265 and the infinite life fatigue strength is below 0.45MPa. While the log value of fatigue life is approximately linear with the amplitude of fatigue load stress, the discreteness of fatigue life, the particularity of concrete, has little to do with the amplitude. The S-N, P-N fatigue life curves and the constant fatigue life diagram of pre-crack concrete are obtained.

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Kim, Tae Wan, Sang Don Lee, and Yong Joo Cho. "Contact Fatigue Life Prediction under EHL Contact." Key Engineering Materials 297-300 (November 2005): 22–27. http://dx.doi.org/10.4028/www.scientific.net/kem.297-300.22.

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In this study, the simulation of contact fatigue based on stress analysis is conducted under Elastohydrodynamic Lubrication (EHL) state. To predict a crack initiation life accurately, it is necessary to calculate contact stress and subsurface stresses accurately. Contact stresses are obtained by contact analysis of a semi-infinite solid based on the use of influence functions and the subsurface stress is obtained using rectangular patch solutions. The numerical algorithm using newton-rapson method was constructed to calculate the EHL pressure. Based on these stress values, three multiaxial high-cycle fatigue criteria are used. As a result, the effects of EHL on contact fatigue life are calculated.

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MOREL, F., and L. FLACELIERE. "Data scatter in multiaxial fatigue: from the infinite to the finite fatigue life regime." International Journal of Fatigue 27, no. 9 (2005): 1089–101. http://dx.doi.org/10.1016/j.ijfatigue.2005.01.009.

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Riveros, Guillermo, Hussam Mahmoud, and Emad Hassan. "Advanced Materials Methods Driving New Life in Critical Infrastructure." Journal on Teaching Engineering 3, no. 1 (2024): 60–73. https://doi.org/10.24840/2183-6493_003-001_2100.

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Fatigue damage is a major threat to many hydraulic steel structures (HSS). HSS experience fatigue loading during operation and are exposed to harsh environmental conditions that reduce fatigue life. The common methods to inspect and repair HSS is time-consuming and costly. Studies investigating the use of bonded Carbon and Basalt fiber reinforced polymer (CFRP, BFRP) to repair fatigue cracks in HSS are lacking. The main objectives of this study was to increase the bonding of FRP, investigate the effectiveness of different fiber-reinforced polymers, and perform experiments on different retrofitting configurations. In this study, eight large-scale center-cracked panels were tested under mode I loading under different environmental conditions, repair materials, and retrofitting configurations. Results indicated that the use of both CFRP and BFRP are both effective at extending fatigue life. Steel retrofitted with full patches of BFRP that cover the crack can reached infinite fatigue life. This article will conclude with several examples where FRP’s have been used to repair lock gates.

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Awwaluddin, Muhammad. "ANALISIS FATIGUE LIFE STRUKTUR DUDUKAN BOGIE MONORAIL UTM 125 KAPASITAS 24 TON MENGGUNAKAN METODE FINITE ELEMENT." Jurnal Teknik Mesin Cakram 2, no. 2 (2020): 59. http://dx.doi.org/10.32493/jtc.v2i2.4022.

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Abstrak: Struktur dudukan bogie pada monorail UTM 125 dengan kapasitas 24 ton perlu dilakukan analisis fatigue. Analisis fatigue merupakan salah satu metode untuk memperkirakan resiko kegagalan, kerusakan dan usia dari suatu struktur yang diakibatkan oleh beban berulang. Dengan analisis fatigue, resiko kegagalan struktur dapat diperkecil sehingga dapat meminimalkan kerugian yang lebih besar. Analisis fatigue dilakukan menggunakan software finite element mengikuti diagram proses analisis. Pembebanan yang diberikan adalah beban aktual desain, beban akibat angin dan beban pada saat kereta berbelok. Dari analisis fatigue pada struktur bogie tersebut didapatkan hasil yang sudah masuk dalam katagori aman atau high cycle (infinite cycle).Kata kunci : analisis struktur, fatigue Struktur, kerusakan struktur, Monorail

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Song, Z. X., Dong Po Wang, G. A. Wei, and C. H. Yang. "Fatigue Performance Study of E36 Steel Welding Joint." Applied Mechanics and Materials 80-81 (July 2011): 173–77. http://dx.doi.org/10.4028/www.scientific.net/amm.80-81.173.

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Fatigue test was carried out on E36 steel no reinforcement welding joint under the same constant amplitude load with ultrasound fatigue tester independent designed by Tianjin University. Test results showed that the specimen would enter infinite life area after 1 x 109 cycle times; All broken specimens fractured in the welding seam. We observed fracture surface using SEM and found all the crack initiation from defects. This paper further analysed the influence of nature, size, position, and distribution of defects on fatigue life.

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Leonetti, Davide, Johan Maljaars, and H. H. (Bert) Snijder. "Uncertainty analysis of constant amplitude fatigue test data employing the six parameters random fatigue limit model." MATEC Web of Conferences 165 (2018): 10016. http://dx.doi.org/10.1051/matecconf/201816510016.

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Estimating and reducing uncertainty in fatigue test data analysis is a relevant task in order to assess the reliability of a structural connection with respect to fatigue. Several statistical models have been proposed in the literature with the aim of representing the stress range vs. endurance trend of fatigue test data under constant amplitude loading and the scatter in the finite and infinite life regions. In order to estimate the safety level of the connection also the uncertainty related to the amount of information available need to be estimated using the methods provided by the theory of statistic. The Bayesian analysis is employed to reduce the uncertainty due to the often small amount of test data by introducing prior information related to the parameters of the statistical model. In this work, the inference of fatigue test data belonging to cover plated steel beams is presented. The uncertainty is estimated by making use of Bayesian and frequentist methods. The 5% quantile of the fatigue life is estimated by taking into account the uncertainty related to the sample size for both a dataset containing few samples and one containing more data. The S-N curves resulting from the application of the employed methods are compared and the effect of the reduction of uncertainty in the infinite life region is quantified.

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Jimenez-Vicaria, J. David, M. Dolores Gomez-Pulido, and Daniel Castro-Fresno. "Numerical and Experimental Evaluation of a CFRP Fatigue Strengthening for Stringer-Floor Beam Connections in a 19th Century Riveted Railway Bridge." Metals 11, no. 4 (2021): 603. http://dx.doi.org/10.3390/met11040603.

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A local and global finite element analysis of the stringer-floor beam connection of a 19th century riveted railway bridge in Spain made of puddle iron were performed to obtain the maximum principal strains in the riveted connecting angles corresponding to bending moments from train loading on the bridge. Due to the anisotropic nature of puddle iron, the connecting angles were modelled using Hill anisotropic plasticity potential and a parametric study in the local FE model of the connection was performed. A laboratory specimen fabricated with original stringers dismantled from the railway bridge was tested to calibrate the numerical models, so the yield stress ratio that best fitted experimental results was obtained. Based on the method of constant fatigue-life diagram and modified Goodman fatigue failure criterion, it was detected that the connecting angles were prone to fatigue crack initiation, as the combination of mean stress and alternating stress amplitude at the toe of the angle fillet remained outside the infinite fatigue-life region. An innovative strengthening system based on adhesively-bonded carbon-fiber reinforced polymer (CFRP) angles was designed to prevent fatigue crack initiation in the connecting angles of the stringer-floor beam connection. Different CFRP laminate layouts were numerically evaluated and a proper configuration was obtained that reduced both the mean stress and the alternating stress amplitude in the connecting angle to shift from finite fatigue-life region to infinite fatigue-life region in the constant fatigue-life diagram. To validate the effectiveness of the proposed CFRP strengthening method, its application on a second laboratory specimen fabricated with original stringers was evaluated experimentally and compared with numerical results. The research study conducted showed that the use of adhesively-bonded CFRP angles was an effective strengthening system in reducing the stress level in the fillet region of the puddle iron connecting angles (where fatigue cracks are prone to initiate) and consequently could increase fatigue life of the stringer-floor beam connection.

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Lee, Young Choon, Nam Jin Jeon, Cheol Kim, Seo Yeon Ahn, and Myung Jae Cho. "Shape Optimization of a Small Bus Steering Knuckle Considering a Fatigue Load." Advanced Materials Research 740 (August 2013): 319–22. http://dx.doi.org/10.4028/www.scientific.net/amr.740.319.

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Finite element analysis was accomplished for a steering knuckle component of a small bus to see whether the static and fatigue strength requirements were satisfied or not. The knuckle was modeled with ANSYS 10-node quadratic elements. The cyclic fatigue load was applied and Soderberg criteria were applied to check the fatigue life. The knuckle structure has an infinite life (10-6 cycle) judging from the fatigue analyses. Shape optimization based on the gradient based method has been performed in order to find out the knuckle shape that has a minimum weight and satisfies the static and fatigue strength requirements. As a result of shape optimization, the weight of the steering knuckle was reduced 8%.

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da Silva, Filipe Alexandre Couto, and Paulo M. S. T. de Castro. "Redesign of a Failed Hoisting Shaft of a Vertical Transfer Device." Eng 4, no. 3 (2023): 1981–2002. http://dx.doi.org/10.3390/eng4030112.

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The redesign of a failed hoisting shaft belonging to a 10 m stroke vertical transfer device (VTD) is presented. Firstly, the operation of the VTD is thoroughly analysed, the variation of loads and moments along the operating cycle is characterised, and transients such as emergency stop loads are calculated. The selection of safety factors and duty cycle factors was followed by the shaft sizing. After an initial rough sizing, the high-cycle fatigue (HCF) design for cyclic bending moments was performed, first considering constant torque and then considering cyclic torque. The number of bending and torsion cycles performed by the hoisting shaft over 10 years was shown to exceed 106, and an infinite life design is mandatory. The analyses showed that the initial shaft diameter was insufficient, thus justifying the failures observed before the present redesign. A classical fatigue model combining torsional shear stresses with bending stresses was used to take into account reversed torsional loading and ensure infinite fatigue life. This work highlights the need to thoroughly understand a machine’s operating cycle so that the wrong premises for fatigue design calculations are not assumed.

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Gänser, H.-P., A. Leitgeb, K. Glinsner, and W. Eichlseder. "Computation of a modified Haigh-Goodman diagram for damage tolerant design for infinite fatigue life." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 221, no. 5 (2007): 619–23. http://dx.doi.org/10.1243/0954406jmes616ft.

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A method for constructing a modified Haigh-Goodman diagram for flawed components is proposed based on the approximation by El Haddad for the crack growth threshold diagram, taking into account the influence of the stress ratio on the fatigue limit of the unflawed material as well as on the linear-elastic crack growth threshold. The modified Haigh diagram uses a minimum of easily obtainable material parameters and permits an easy application of damage tolerant design concepts when dimensioning for infinite fatigue life.

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Harris, T. A., and J. I. McCool. "On the Accuracy of Rolling Bearing Fatigue Life Prediction." Journal of Tribology 118, no. 2 (1996): 297–309. http://dx.doi.org/10.1115/1.2831299.

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Ball and roller bearings are designed to meet endurance requirements basically determined according to the Standard fatigue life calculation method. This method is based on the Lundberg-Palmgren fatigue life theory as modified by reliability, material, and lubrication factors. As application load and spied requirements have increased, the Lundberg-Palmgren method has resulted in bearings of increased size, adding unnecessarily to the size and weight of mechanisms. This is a critical design situation for weight and size-sensitive components such as aircraft gas turbine engines and helicopter power transmissions. The bearing life prediction method developed by Ioannides and Harris recognizes the existence of a fatigue limit stress. If the stresses an operating bearing experiences do not exceed the limit stress, the bearing can achieve infinite life. In any case, the method tends to predict longer lives than the Lundberg-Palmgren method. This paper evaluates the life prediction accuracies of the Lundberg-Palmgren and Ioannides-Harris methods by comparing lives calculated according to these methods and to those actually experienced in 62 different applications. As a result of the investigation, the Ioannides-Harris method is shown to more accurately predict bearing fatigue endurance.

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Tchoupou, Kévin M. Tsapi, Bertin Désiré Soh Fotsing, and Alexis Kuitche. "Fatigue Safety Coefficient Based Mutual Comparison of the Simple Working Regime of Hermetic Compressor Suspension Springs." International Journal of Engineering Research in Africa 16 (June 2015): 26–37. http://dx.doi.org/10.4028/www.scientific.net/jera.16.26.

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Compressors suspension made up of helical suspension spring system has a significant importance on the operation of hermetic compressors, considering the aspects of noise and vibration. These springs are loaded by harmonic forces very often. High cycles fatigue damage and failure can be found during its service loading. The severity of lading regime has been studied for three typical loading regimes of springs using the fatigue safety factor. The spring fails by fatigue not yielding; infinite life is not predicted. All cases are demonstrated in the Haigh diagram. Finite life is predicted. It has been showed that loading cases with constant mean shear give lowest safety factor than the proportional or constant middle stress regimes.

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Ślęzak, Tomasz. "Prediction of Fatigue Life of Welded Joints Made of Fine-Grained Martensite-Bainitic S960QL Steel and Determination of Crack Origins." Advances in Materials Science and Engineering 2019 (February 4, 2019): 1–9. http://dx.doi.org/10.1155/2019/9520801.

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Due to growing requirements connected with the utilization of advanced structures, nowadays the modern design processes are developed. One of the crucial issues considered in these processes is proper design of the joints against fatigue in order to fulfill a stated life of operation. In this study, the method of fatigue life prediction based on the criterion of permissible strain range in the notch root is presented. An engaged simplified model of fatigue life prediction was previously developed for mild and carbon steels. The evaluation made during the research has proven that this method can also be used for S960QL high-strength steel characterized by entirely different properties and structure. A considered theoretical model demonstrates satisfactory correlation with experimental data and safely describes the fatigue life of weldments. Furthermore, the predicted fatigue life of studied steel without welds shows great comparability with experimental data. The limit value of the strain range in the notch root was estimated. Below this value of strain, the fatigue life of welded joints is infinite, theoretically. Finally, the impact of the surface imperfections on the fatigue crack initiation was revealed. For paternal material, the origins of cracking were discovered at the places of nonmetallic scale particles. In welded joints, the fatigue cracks initiated at the whole length of the fusion line.

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Shen, Jian, and Xiao Yun Liu. "Research on the Bridge Tower Crack Propagation under Thermal Fatigue Loading." Advanced Materials Research 1004-1005 (August 2014): 1537–40. http://dx.doi.org/10.4028/www.scientific.net/amr.1004-1005.1537.

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The bridge tower crack extension probability is very large because of the stress concentration at the crack tip, combined with the fatigue stress. Based on the long-term observations of temperature fatigue load spectrums of a bridge tower and the experiment of concrete fatigue performance parameters, the problem of crack propagation is analyzed by infinite life safety reliability model and safe and reliable crack extension randomness model. It is concluded that the concrete structure crack extension probability is close to 98.6% and reasonable repair cycle should be about 3 years.

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Wang, Fengde, Wensheng Xiao, Qi Liu, Lei Wu, and Zhanbin Meng. "An Analytical Method for Jack-Up Riser’s Fatigue Life Estimation." Mathematical Problems in Engineering 2018 (2018): 1–9. http://dx.doi.org/10.1155/2018/5843525.

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In order to determine whether a special sea area and its sea state are available for the jack-up riser with surface blowout preventers, an analytical method is presented to estimate the jack-up riser’s wave loading fatigue life in this study. In addition, an approximate formula is derived to compute the random wave force spectrum of the small-scale structures. The results show that the response of jack-up riser is a narrow band random vibration. The infinite water depth dispersion relation between wavenumber and wave frequency can be used to calculate the wave force spectrum of small-scale structures. The riser’s response mainly consists of the additional displacement response. The fatigue life obtained by the formula proposed by Steinberg is less than that of the Bendat method.

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Chen, Yan, and Yuan Tao Sun. "Study on Crack Component Fatigue Life Analysis Based on SIF Fitting." Applied Mechanics and Materials 229-231 (November 2012): 656–60. http://dx.doi.org/10.4028/www.scientific.net/amm.229-231.656.

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The present structure crack analysis method simplifies the crack as type I crack, and put the stress intensity factor (SIF) mathematical expression of infinite plate under the bi-directional even stress load into Paris formula to analyse the fatigue life of crack components. Due to the finiteness and complexity of component shape and the nonuniformity of the stress distribution in the engineering practice, which makes the SIF value inaccuracy according to the present method, so that the result of crack fatigue life has a large error. Considering the shortcomings of the method, this paper offers a new method which is using the finite element method to calculate SIF in different crack length directly. By means of function fitting, this method determines the mathematical relation between SIF and the crack length and changes the form of Paris formula based on the relation. Furthermore, it can analyse the fatigue life of crack components and improve the analysis accuracy theoretically.

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Wang, Bo Han, Li Cheng, and Xun Chun Bao. "Effect of Heat Treatment on Very High Cycle Fatigue Properties of TC4." Key Engineering Materials 881 (April 2021): 3–11. http://dx.doi.org/10.4028/www.scientific.net/kem.881.3.

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The bimodal, equiaxed and Widmanstatten microstructures of TC4 titanium alloy were obtained through different heat treatment processes. The content of primary α phase in the bimodal and equiaxed microstructures was measured to be about 40% and 90%, and the average size was about 9.4μm and 7.9 μm. Three types of microstructure fatigue S-N curves are obtained, which are successively descending type, single-platform descending type and infinite life type. The order of very high cycle fatigue performance is Widmanstatten>equiaxed>bimodal, but the anti-fretting fatigue performance of Widmanstatten is the worst. The grain refinement makes the fatigue performance of the equiaxed better than that of the bimodal. The second process is determined as the best heat treatment method. There is no significant difference in the life of the crack propagation stage. The very high cycle fatigue life mainly depends on the crack initiation stage. In the bimodal and the equiaxed, the crack initiates in the primary α phase of the subsurface, and the crack in the Widmanstatten initiates in the coarse α 'grain boundary of the subsurface.

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Lee, Yong-Bok. "A Study on Estimation of Infinite Fatigue Life in Cruciform Fillet Welded Joint." Journal of the Korean Institute of Gas 17, no. 1 (2013): 19–25. http://dx.doi.org/10.7842/kigas.2013.17.1.19.

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Lee, Sang Hoon. "Fatigue Analysis of Stripper Bolt Under Combined Loading for Improvement of Stamping Die Design." Journal of Vibration and Acoustics 108, no. 2 (1986): 222–29. http://dx.doi.org/10.1115/1.3269328.

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A common problem of fatigue failure of stamping dies was experienced during the stamping operation with socket-head screws. In order to establish a design standard for the stripper bolt, a methodology for determination of the loads and the fatigue strength of the stripper bolt was developed. Stresses due to an impulsive load and a rectangular pulse were calculated based on a simplified spring mass system and the appropriate corrections were made to elaborate the solution. This approximate solution was validated by a finite element analysis. The stripper bolt should have an infinite fatigue life to survive a half million stamping operations. The fatigue problem involves a stress concentration with combined mean and alternating stresses. The Gerber parabola and the residual stress method were employed to treat the combined loading and the stress concentration. In order to enhance the fatigue life of the stripper bolt, a cushion is introduced at the surface where an impact load is applied. The cushion is found very effective in improving the fatigue life of the stripper bolt. An interactive computer program was developed as a tool for designing stamping dies.

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Fathi Sola, Jalal, Farhad Alinejad, Foad Rahimidehgolan, and Amirreza Niazmand. "Fatigue life assessment of crankshaft with increased horsepower." International Journal of Structural Integrity 10, no. 1 (2019): 13–24. http://dx.doi.org/10.1108/ijsi-04-2018-0020.

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Purpose The purpose of this paper is to analyze the fatigue life of the crankshaft in an engine with increased horsepower. Design/methodology/approach The applied load on the powertrain components was calculated through a dynamic analysis. Then, to estimate the induced stress in every crank angle, the calculated loads in different engine speeds were applied on the crankshaft. Finally, the critical plane fatigue theories in addition to URM standard were used to estimate the damage and fatigue life of the crankshaft with the increased power. Findings It was found that a simultaneous increase of gas pressure and engine speed by 30 percent will cause an increase of maximum applied load on the crankshaft by 25 percent. It was also found that while the results of finite element (FE) method predict an infinite life for the crankshaft after increasing the power, the URM method predicts an engine failure for the increased power application. In this study, the crankpin fillet is introduced as the most critical area of the crankshaft. Originality/value Increasing the power of the internal combustion engines without changing its main components has been of high interest; however, the failure associated with the increased load as the result of increased power has been a big challenge for that purpose. Moreover, although URM standard provided an efficient practice to evaluate a crankshaft fatigue life, using FE analysis may provide more reliability.

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Wang, Guixin, Yilong Cao, Jialing Zhu, and Qiang Yu. "Analysis of dynamic fatigue characteristics of critical parts of highly strengthened single cylinder diesel engine." Journal of Physics: Conference Series 2383, no. 1 (2022): 012101. http://dx.doi.org/10.1088/1742-6596/2383/1/012101.

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In this paper, the strength analysis and fatigue life calculation of multi-component coupling of crankshaft, connecting rod and engine body of highly strengthened single cylinder diesel engine are carried out. The stress of crankshaft, connecting rod and engine body in two working cycles is calculated by multi-component coupling transient dynamics, and the strength is analyzed based on the third strength theory firstly; Then, the accuracy of the transient calculation results is verified by the strength experiment of the crankshaft and connecting rod reduced scale model and the calculation of the static stress of the body; Finally, according to the stress fatigue life calculation method, the fatigue life of crankshaft, connecting rod and engine body is calculated. The maximum stress of crankshaft, connecting rod and body is less than the yield limit of corresponding materials; The fatigue life calculation results show that the damage accumulation of the engine body is very little, which meets the design requirements of infinite life. The damage accumulation of the crankshaft at the fillet of the main journal and the connecting rod at the side of the rod is 32005.6 hours and 102841.7 hours respectively, which meeting the design requirements of 20000 hours.

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LEE, HYUN-SEUNG, JANG-WON LEE, and YOUNG-SHIN LEE. "FATIGUE ANALYSIS ON THE END COUPLING OF THE ALUMINUM HOT ROLLING EQUIPMENT." International Journal of Modern Physics B 25, no. 31 (2011): 4225–28. http://dx.doi.org/10.1142/s0217979211066635.

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The End Coupling is the main component of the aluminum hot rolling equipment. The End Coupling is used for transmission of rotational power with heavy-duty load. Fracture of the End Coupling causes serious economic losses because an End Coupling is a very expensive component and it takes a long time to repair it. Therefore, preventing the destruction of the End Coupling is essential for ensuring a long mechanical life cycle. In this paper, a parameter study on the End Coupling was performed in order to minimize maximum stress of the End Coupling under static loads. As a result of an optimum design for life extension on the End Coupling, the maximum stress of the modified End Coupling was lower than that of the initial model by 29%. The fatigue analysis for fatigue life prediction of the modified End Coupling was performed using the commercial finite element method. In the results of the fatigue life analysis, the safety factor of the modified End Coupling was 1.123. Therefore, it was demonstrated that the modified End Coupling has infinite life.

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Dong, Hong Lei, Zhi Xiang Duan, Bang Xian Li, and De Yin Wang. "Study on Fatigue Performance of Large Volume Seamless Steel Cylinder Served in CNG Hydraulic Daughter Station System." Applied Mechanics and Materials 249-250 (December 2012): 642–45. http://dx.doi.org/10.4028/www.scientific.net/amm.249-250.642.

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The working condition of cylinder is different from the design which needs high frequency of 20~ 22MPa in hydraulic daughter station system. In order to evaluate the safety of cylinder, the fatigue performance of jumbo cylinder was studied by way of FEA. The results show that cylinder fatigue cycle life is less than 15000 under the pressure range 2~ 36.7MPa and it cannot be used as design working pressure 22MPa. But it can serve in 20~22MPa for infinite loop to meets the requirement of hydraulic daughter station.

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Goushegir, Seyed Mohammad, Jorge F. dos Santos, and Sergio T. Amancio-Filho. "Fatigue Performance of Metal–Composite Friction Spot Joints." Materials 14, no. 16 (2021): 4516. http://dx.doi.org/10.3390/ma14164516.

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Friction spot joining is an alternative technique for joining metals with polymers and composites. This study investigated the fatigue performance of aluminum alloy 2024/carbon-fiber-reinforced poly(phenylene sulfide) joints that were produced with friction spot joining. The surface of the aluminum was pre-treated using various surface treatment methods. The joined specimens were tested under dynamic loading using a load ratio of R = 0.1 and a frequency of 5 Hz. The tests were performed at different percentages of the lap shear strength of the joint. Three models—exponential, power law, and wear-out—were used to statistically analyze the fatigue life of the joints and to draw the stress–life (S–N) curves. The joints showed an infinite life of 25–35% of their quasi-static strength at 106 cycles. The joints surpassing 106 cycles were subsequently tested under quasi-static loading, showing no considerable reduction compared to their initial lap shear strength.

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Abbadi, Ahmed, Laurent Michel, and Bruno Castanié. "Experimental Analysis of Debonding of Skin/Stringer Interfaces under Cyclic Loading and Ageing." Advanced Composites Letters 23, no. 6 (2014): 096369351402300. http://dx.doi.org/10.1177/096369351402300602.

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An experimental investigation aiming to characterize the fatigue failure mechanisms and effect of ageing of skin/stringer interfaces is presented. A simplified specimen known as a “stringer foot specimen” is used. The effects of local design, of the angle of plies located at the interface and of moisture ageing are studied. Among other results, it is shown that a quasi-infinite fatigue life can be obtained under 33% of the static damage initiation load for all designs. In the framework of multi-level analysis, this study is a preliminary investigation to study cyclic buckling of composite stiffened structures.

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Prasetyo, Anang, Efi Afrizal, and Nazaruddin Nazaruddin. "Development of Rotary Fatigue Test Equipment Based on the Joseph Marin Approach." Journal of Ocean, Mechanical and Aerospace -science and engineering- (JOMAse) 67, no. 3 (2023): 95–100. http://dx.doi.org/10.36842/jomase.v67i3.344.

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This paper proposed the development of rotary fatigue test equipment. This equipment was used to test the JIS S45C steel, validated using the Joseph Marin approach. Analyzing the fatigue strength of JIS S45C steel using the Joseph Marin approach was compared to experimental testing. The dimension of the test specimens was based on the ASTM E 466. The test data was displayed in the form of an S-N curve. The test results showed the fatigue strength of JIS S45C steel on the whole that was close to each other, experimentally and using the Joseph Marin approach. In the infinite life region, it is known that the fatigue strength based on the Joseph Marin approach was lower than experimental tests. Therefore, if JIS S45C steel had received a hefty load repeatedly, it would fail more quickly.

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Major, Stepan, Stepan Hubalovsky, and Josef Šedivý. "Combined Corrosion and Fatigue Degradation of Nitinol Implants." Advanced Materials Research 712-715 (June 2013): 474–77. http://dx.doi.org/10.4028/www.scientific.net/amr.712-715.474.

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Nitinol is metal alloy of nickel and titanium. It has wide range of applications. The most significant application is production of self-expanding stent-grafts, which are commonly used in vascular surgery. Stent-graft manufactures are confronted with two basic requirements: stents must have an infinite life; stents must be made of the thinnest wires us possible. Stent-graft failure or device fatigue remains major concern for stent-graft manufactures and researches. The stent-grafts are mechanically loaded, and also the device is placed in very aggressive environment. The corrosion stability of Nitinol is strongly dependent on the surface preparation: grinding, polishing, chemical etching. The paper deals with fatigue degradation of stent-grafts in corrosive environment.

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Kim, Ye Jin, Young Min Kim, Young Rae Cho, and Sung Hyuk Park. "Tensile and Fatigue Properties of Twin-Roll-Cast AZ31 Magnesium Alloy Strips with Different Thicknesses." Materials Science Forum 1034 (June 15, 2021): 9–15. http://dx.doi.org/10.4028/www.scientific.net/msf.1034.9.

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This study investigates the microstructure, tensile properties, and high-cycle fatigue resistance of twin-roll-cast Mg-3Al-1Zn (wt%) alloy strips with thicknesses of 1 mm, 1.5 mm, and 3 mm. The investigation results reveal that the 1-and 1.5-mm-thick strips show a fully dynamically recrystallized (DRXed) microstructure consisting of fine equiaxed DRXed grains, whereas the 3-mm-thick strip shows a partially DRXed microstructure containing very coarse elongated unDRXed grains because of the insufficient strain imposed during twin-roll casting. The inhomogeneous microstructure of the 3-mm-thick strip leads to a large deviation in its tensile elongation. The average grain size of the strips increases with increasing strip thickness, which results in reductions in both their tensile strength and their ductility because of the weakened grain-boundary hardening effect and the promoted formation of undesirable twins, respectively. The high-cycle fatigue resistance in the stress regime with finite fatigue life is similar for all three strips, but the fatigue strength with infinite fatigue life decreases from 175 MPa to 140 MPa as the strip thickness increases from 1 mm to 3 mm. The fatigue strength (FL) increases linearly with increasing yield strength (YS) according to the relationship FL = -199.5 + 2.03·YS.

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Kumar, Gideon Praveen, and Lazar Mathew. "FATIGUE AND DURABILITY OF A NOVEL PERCUTANEOUS AORTIC VALVE STENT." Biomedical Engineering: Applications, Basis and Communications 23, no. 01 (2011): 45–49. http://dx.doi.org/10.4015/s1016237211002360.

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To design against mechanical failure, most implants such as valve stents are assessed on the basis of survival on a long term. However, accurate investigation of the stress/strain distributions in such valve stents, which govern their deformation and fracture behavior, is essential for their prolonged, and safe use. With this background, an S–N type fatigue analysis was done on three stents with Von Mises stress component having the infinite life at 1.e + 006. The results of this study may aid a biomedical scientist to zero in on the material that could be used to analyze and fabricate percutaneous valve stents.

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Pehlivan, Ahmet Selim, Mahmut Faruk Aksit, and Kemalettin Erbatur. "Fatigue Analysis Design Approach, Manufacturing and Implementation of a 500 kW Wind Turbine Main Load Frame." Energies 14, no. 12 (2021): 3581. http://dx.doi.org/10.3390/en14123581.

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The main load frame of a wind turbine is the primary mount for all nacelle equipment and is used as the principal load transmitter. This frame should have a reliable fatigue safety rating because it is a load-bearing component. In this work, the fatigue life design, manufacturing and implementation process for the main load frame of a 500 kW wind turbine are studied. The weight of the main load frame and static safety factors are preserved while the cyclic life of the bedplate is kept infinite. Modified Goodman theory is applied to achieve an effective fatigue design using a commercial finite element software package. Analytical calculations are carried out to obtain the safety factors of the bedplate and dynamic strength of the materials. A finite element approach is employed to perform stress analysis. Stress oscillations are established for both welded and cast parts of the hybrid bedplate, and the maximum and minimum stress values are established. Fatigue safety factors are calculated via fatigue analysis iterations. The obtained safety factors are adequate from the perspective of commonly accepted fatigue safety standards. Welding and casting techniques are applied together for manufacturing of the frame. On-site testing indicates that the wind turbine does not show any signs of fatigue. Rupture, cracks, and abrupt accelerometer reading variations are not observed.

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Slebioda, Marek, Reinier Giele, and Matthijs Langelaar. "Topology optimization for infinite fatigue life of cyclic symmetric structures subjected to non-proportional loading." Computers & Structures 286 (October 2023): 107113. http://dx.doi.org/10.1016/j.compstruc.2023.107113.

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Hammed, Vivean Hassan, Mohammed Ali Nasser, and Ali Hassan Salih. "Fatigue Life Prediction for an Extrusion Die Based on the Experimental Factors." Tikrit Journal of Engineering Sciences 32, no. 1 (2025): 1–15. https://doi.org/10.25130/tjes.32.1.31.

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According to the fact that the practical method for finding the working fatigue life is very expensive and takes a longer time with a huge amount of samples till the failure initiation of the die. So, the present research describes the main purpose of predicting the fatigue life of the die numerically based on the highest loading factors getting from the experimental work, indicating how many numbers of product samples can be produced during the whole life of this designed die depending on these loading or over. This fatigue life analysis and assessment were adopted by ANSYS Workbench 2019 R3 software depending on the loading factors (axial extrusion load and friction temperature difference) affecting the die strength and fatigue life during the experimental extrusion process. These factors were generated according to the variation of extrusion speed and changing product materials. The extrusion die was used to convert a cylindrical bar with (19) mm diameter into a square bar with (13 × 13) mm with an extrusion rate of 1.67. The results showed that the highest stress intensity factor reached about (251.4 MPa) at the critical converge-diverge section due to the die profile design, and the die is safe and has an infinite life reaching up to (10^9 cycles), using Lead or Aluminum products taking the maximum extrusion load of (90 kN) and temperature difference of (2 ℃) at 150 mm/min extrusion speed. While changing the product billet into harder materials, the die life decreased and might fail later.

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Ne´lias, D., and F. Ville. "Detrimental Effects of Debris Dents on Rolling Contact Fatigue." Journal of Tribology 122, no. 1 (1999): 55–64. http://dx.doi.org/10.1115/1.555329.

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Debris dents produced by solid particles in suspension in oil or grease when they travel through an EHL contact may be at the origin of rolling bearing failures. A summary of an experimental investigation carried out to identify (i) the particle entry ratio, (ii) the mechanisms of particle fragmentation or deformation, (iii) the resulting indentation features, and (iv) the initiation site of subsequent surface damage is presented first. Afterwards, numerical simulations of a dent moving through an EHL contact are performed. A critical slide-to-roll ratio is found. Results of our numerical simulations are analyzed and discussed in relation to the concept of infinite life for rolling bearing applications. [S0742-4787(00)00901-2]

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Mantilla, C. A., J. A. Valdés, and F. Casanova. "Multiaxial fatigue analysis for the shaft of a 100 MW hydro-power generator." Journal of Mechanical Engineering and Sciences 13, no. 2 (2019): 4928–45. http://dx.doi.org/10.15282/jmes.13.2.2019.12.0409.

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This paper presents a stress and fatigue life analysis for the shaft of a 100 hydro-generator. Normal and shear stresses were measured at the cylindrical section of the shaft at several power levels. A finite element model was developed to find points with stress concentration and the corresponding stress concentration factor. Analytical models taken from the literature were implemented to calculate stresses during phase-to-ground and phase-to-phase failure. Stresses were linked with the generation history of the machine taken each hour during one year to obtain the stress history. With the stress history, the Wang-Brown multiaxial fatigue model and the Miner’s rule were used to estimate the fatigue life. Stresses on the shaft were found to be dependent on the generated power. Operation at partial load (between 30 and 60% of full load) was found to produce higher vibration in comparison with operation at power greater than 60% of full load. Changing the power level produced higher damage than the vibration produced during operation at a steady state condition. It was found that the shaft has a practically infinite life even when the damage produced during electrical failure was considered.

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Béranger, Mathieu, Guillaume Morin, Sarah Saanouni, Alain Koster, and Vincent Maurel. "Fatigue of automotive engine cylinder heads – A new model based on crack propagation." MATEC Web of Conferences 165 (2018): 10013. http://dx.doi.org/10.1051/matecconf/201816510013.

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The main reliability issue encountered during cylinder head development is the appearance of fatigue cracks during severe endurance tests. Some of these cracks can initiate in the coolant water jacket and lead to the complete part failure. They are mainly associated with the combination of combustion pressure alternate stresses and high cycle fatigue load in infinite life domain. However, Haigh or Dang Van analysis issued from 3D Finite Element Analysis reveals several issues: crack initiations are not correctly located and scatter of crack sizes are not predicted. To overcome these difficulties, a new fatigue model dedicated to cylinder heads in Aluminum - Silicon alloy has been developed in Renault powertrain division. The model is based on fatigue crack growth modelling in order to take into account various and combined load ratio in one hand, and typical characteristics of the microstructure of casting alloy in the other hand. This paper presents the theoretical basis of this model and the associated identification methodology for two different aluminum alloys.

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Klabklay, Teerawat, Chaiyut Sumpavakup, Asawadech Khumkrong, Natthikan Thasanavirud, and Pannachai Pensuk. "Finite Element Analysis for Estimating Strength and Fatigue of the APM Structure." E3S Web of Conferences 602 (2025): 01012. https://doi.org/10.1051/e3sconf/202560201012.

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APM stands for autonomous people mover, which is a mass transit system widely used in many airports to transport passengers between terminals. This article focuses on APM structure newly designed comprising five components namely, chassis, floor, body, roof, and support. The objective of this article is to estimate the strength and fatigue of each component to assess safety. The finite element analysis is implemented to figure out the key results in both static and fatigue load analysis as follows: maximum displacements, maximum stresses and minimum factors of safety in static load, and minimum fatigue life cycles. The grid independence test, which is a significant process in numerical method, is carried out. The results show that the maximum displacements of the chassis, floor, body, roof, and support provide 13.3, 1.13, 0.21, 2.0, and 0.06 millimeters, respectively. The maximum stresses are about 155, 138, 35.9, 167, and 58.2 MPa, respectively, which do not exceed yield strength of material. The minimum factors of safety are about 1.6, 1.8, 7.0, 1.5, and 4.3, respectively, which are in accordance with APM standards. The minimum fatigue life cycles are obtained 1.4, 1.25, 4.81, 1.03, and 2.96 million cycles, respectively, which are not less than the infinite life cycle. Thus, it is obvious that all five components of APM structure are adequate strength and safe to function.

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Buratynski, E. K. "Analysis of Bending and Shearing of Tri-Layer Laminations for Solder Joint Reliability." Journal of Electronic Packaging 120, no. 3 (1998): 221–28. http://dx.doi.org/10.1115/1.2792626.

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For solder joint reliability reasons, direct chip attach technology uses an underfill material to restrict the movement of the silicon die relative to the substrate due to differences in their coefficients of thermal expansion. Modeling the fatigue life of a solder joint assembled with this technology requires a shear strain versus applied shear stress relationship. The direct chip attach configuration can be modeled as a tri-layer lamination that bends and shears with temperature excursions from the stress-free temperature. The present analysis formulates an axisymmetric, tri-layer, elastic material stress model with finite radii for the silicon die and underfill layer and an infinite sized substrate layer. A closed form solution to the shear distributions at the interfaces and the bending of the lamination is presented. This solution is a function of the reactant forces exerted by solder joints and forms the basis of a fatigue life model.

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Vigón, Paula, Antonio Argüelles, Miguel Lozano, and Jaime Viña. "Mode II Delamination under Static and Fatigue Loading of Adhesive Joints in Composite Materials Exposed to Saline Environment." Materials 16, no. 24 (2023): 7606. http://dx.doi.org/10.3390/ma16247606.

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This study investigates the fatigue delamination behavior of adhesive joints in epoxy carbon composite materials under Mode II fracture loading. The joints were characterized using the End-Notched Flexure (ENF) test, comprising adhesive joints formed by bonding two unidirectional carbon fiber epoxy matrix laminates with epoxy adhesive. These joints were subjected to different exposure periods (1, 2, 4, and 12 weeks) in a saline environment. Prior to dynamic fatigue testing, critical Mode II energy release rate values were determined through quasi-static tests, serving as a reference for subsequent fatigue characterization. This study aimed to comprehend how exposure duration to a saline environment affected the initial stage of fatigue delamination growth and employed a probabilistic model based on the Weibull distribution to analyze the experimental data. The results, gathered over a two-year experimental program, revealed varying behaviors in adhesive joint resistance to delamination based on exposure duration. A noteworthy reduction in fatigue strength capacity was observed, with fracture energies for infinite fatigue life reaching approximately 20% of their static loading capacity. This study sheds light on the deterioration of adhesive joints when exposed to a saline environment.

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Jayanthan, Gunarajah, S. A. Abu Bakar, and I. I. Mazali. "Fatigue Life and Stress Analysis of a Single Cylinder Four Stroke Crankshaft." International Journal of Automotive and Mechanical Engineering 21, no. 3 (2024): 11695–711. http://dx.doi.org/10.15282/ijame.21.3.2024.19.0902.

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This paper focuses on the optimization of a crankshaft using ANSYS software in terms of weight and strength. The initial designs of the crankshaft, piston, and connecting rod were created using SolidWorks. The force generated by the gas during the combustion process was calculated to be 12017 N. Next, the SolidWorks assembled system was imported into ADAMS View software for simulation, which revealed a time-variant force of the crankpin of 14049 N. The calculated value was verified with results obtained from analytical calculations, showing a deviation of 0.23%. Finite element analysis was done for the crankshaft using ANSYS transient structural after applying loadings and boundary conditions. The optimization process aimed to minimize the crankshaft's weight while maintaining its strength and durability. The results of the ANSYS simulations showed a weight reduction of 2.5% from the original 2.983 kg to 2.907 kg, while maintaining the required strength and durability. The optimized crankshaft was compared to its original design in terms of fatigue life, weights, and stresses. The maximum von Mises stress was reduced by 16%, shear stress by 3.5%, and deformation by 3.5%, which were validated through analytical calculations. The crankshaft analysis resulted in a significant increase in fatigue life, calculated to be infinite under the given conditions. To conclude, the objective to optimize the crankshaft for performance and efficiency was achieved, demonstrating a 2.5% weight reduction and substantial improvements in fatigue life and stress distribution, proving the effectiveness of ANSYS software for the design optimization process.

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Thakur, K., S. S. Banwait, and R. Bedi. "Finite element analysis of U-frame of robotic gait trainer for rehabilitation." IOP Conference Series: Materials Science and Engineering 1248, no. 1 (2022): 012068. http://dx.doi.org/10.1088/1757-899x/1248/1/012068.

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Abstract The use of robotic trainers in the medical field for rehabilitation has increased in recent years due to the results they can achieve compared to conventional therapy methods. This study proposes the design of a U-frame and handrail assembly in a dynamic bodyweight support system of a robotic trainer and provides the static structural analysis of the model. Von Mises stress distribution and fatigue life of the components have been provided to ensure the safety of the model during the rehabilitation process. The material considered for the simulation on the Ansys workbench is mild steel. The peak stress value observed is 96.64 MPa. In case of fatigue failure, the model provided is safe for the infinite cycle with a safety factor of 2.5.

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da Costa, Pedro R., Diogo Montalvão, Manuel Freitas, and Luis Reis. "Ultrasonic fatigue experiments with biaxial cruciform specimens." MATEC Web of Conferences 300 (2019): 18004. http://dx.doi.org/10.1051/matecconf/201930018004.

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Fatigue studies of materials in simple or complex loading systems for any given lifetime is object of continuous research. This is due to the advancements on mechanical and structural components, as well as for new and innovative materials, which implies the knowledge of a materials response to all dynamic loads. The fatigue failure regime beyond what was once considered to be the fatigue limit (infinite life) is characterized between 107 and 109, known as Very High Cycle Fatigue regime. Due to the time consuming and wide energy consumption of conventional fatigue testing for such regime, fatigue tests under ultrasonic actuators are being used, capable of applying the dynamic loads at around 20 kHz. Nowadays, several variants of ultrasonic fatigue tests were already proposed and tested but it is still a somewhat limited fatigue test if compared to the conventional servo-hydraulic fatigue testing machines of general use. In this study, biaxial in plane stresses are induced in specially designed cruciform specimens with ultrasonic fatigue testing resonant principals. Two geometries were numerically analysed, manufactured and experimentally tested, the in-phase tension-tension (T-T) specimen and the out-of-phase compression-tension (C-T) specimen. All specific designed geometries go under a thorough numerical and several experiments analysis for their validation. The specimens showing a correct and as intended behaviour are led to failure.

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Lima, Douglas Nogueira de, and Sergio Junichi Idehara. "Improved Performance of Box Truck Life using Computational Analysis." Journal of Engineering and Exact Sciences 11, no. 1 (2025): 21154. https://doi.org/10.18540/jcecvl11iss1pp21154.

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This case study presents an investigation of the structural behavior of a box truck body mounted on the chassis of a Volkswagen Constellation 24.330, utilizing Finite Element Method (FEM). The study specifically evaluates the performance of the structure under static and fatigue conditions, comparing scenarios with and without reinforcement applied to the rear column. Aimed at improving the structural performance and durability of commercial vehicles, the research focuses on identifying stress distribution, analyzing torsional behavior, and addressing common structural failures such as cracks and deformations. The results demonstrate that the implementation of rear column reinforcement enhances the structural performance of the box body. Stress concentrations were reduced by over 30% under uniform load conditions, while maximum displacement under torsion decreased by 64%. Additionally, the torsional stiffness of the structure increased by 162%, leading to improved durability and greater resistance to dynamic loads. The fatigue analysis showed infinite life for most parts of the reinforced structure; however, critical areas, such as the intermediate columns and lower I-beam regions, were identified as stress concentration zones requiring closer attention to manufacturing quality. This study highlights the importance of computational simulations in optimizing vehicle design by enabling accurate predictions of structural behavior. By reducing stress concentrations and improving durability, the proposed solution addresses the challenges faced by commercial vehicles and enhances their safety and reliability in the market.

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Subhash, NN, Adathala Rajeev, Sreedharan Sujesh, and CV Muraleedharan. "TTK Chitra tilting disc heart valve model TC2: An assessment of fatigue life and durability." Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine 231, no. 8 (2017): 758–65. http://dx.doi.org/10.1177/0954411917703676.

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Average age group of heart valve replacement in India and most of the Third World countries is below 30 years. Hence, the valve for such patients need to be designed to have a service life of 50 years or more which corresponds to 2000 million cycles of operation. The purpose of this study was to assess the structural performance of the TTK Chitra tilting disc heart valve model TC2 and thereby address its durability. The TC2 model tilting disc heart valves were assessed to evaluate the risks connected with potential structural failure modes. To be more specific, the studies covered the finite element analysis–based fatigue life prediction and accelerated durability testing of the tilting disc heart valves for nine different valve sizes. First, finite element analysis–based fatigue life prediction showed that all nine valve sizes were in the infinite life region. Second, accelerated durability test showed that all nine valve sizes remained functional for 400 million cycles under experimental conditions. The study ensures the continued function of TC2 model tilting disc heart valves over duration in excess of 50 years. The results imply that the TC2 model valve designs are structurally safe, reliable and durable.

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Hernandez-Rodriguez, Marco A. L., Rafael D. Mercado-Solis, Gerardo Presbítero, Diego E. Lozano, Gabriela M. Martinez-Cazares, and Yaneth Bedolla-Gil. "Influence of Boron Additions and Heat Treatments on the Fatigue Resistance of CoCrMo Alloys." Materials 12, no. 7 (2019): 1076. http://dx.doi.org/10.3390/ma12071076.

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Cobalt-based alloys are widely used in the manufacture of joint prostheses. In this study, the effect of boron additions and heat treatment on the ASTM F75 was evaluated by rotating bending fatigue. The boron ranged from 0.06–1 wt %. The alloys were tested in as-cast and heat-treated conditions. In the as-cast condition, the infinite life was observed at 380 MPa, improving to 433–615 MPa according to the amount of boron added. In the heat treatment condition, the fatigue resistance was improved only in the base alloy. The addition of 0.06 wt % boron and heat treatment led to the same resistance as in the as-cast condition. Adding large amounts of boron combined with heat treatment diminished the fatigue limit. The fracture analysis revealed primarily brittle behaviour with some ductile features even on the same sample; only the heat-treated alloy with 0.06 wt % boron was clearly ductile. This alloy also exhibited notably better toughness to crack propagation.

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Bachir Bouiadjra, Bel Abbes, S. M. A. K. Mohammed, Faycal Benyahia, and Abdulmohsen Albedah. "Fatigue Behavior of Al 7075-T6 Plates Repaired with Composite Patch under the Effect of Overload." Metals 11, no. 12 (2021): 2025. http://dx.doi.org/10.3390/met11122025.

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Repair of aeronautical structures by composite patch bonding has shown its effectiveness in several studies during the last few decades. This repair technique leads to a retardation in the propagation of repaired cracks via load bridging across the patch throughout the adhesive layer, interfacing it with the repaired structure. The purpose of this study is to analyze the behavior of patch-repaired cracks present in thin plates made of aluminum alloy 7075-T6 and subjected to a single tensile overload. The sequence of application of overload on the fatigue behavior was also studied. Fatigue tests were conducted on Al 7075-T6 notched specimens where crack growth and number of cycles to failure were monitored for different patching/overload scenarios. A detailed fractographic study was performed on failed specimens to analyze the micromechanical behavior of the crack growth related to each scenario. The obtained results showed that the application of the overload before bonding the patch leads to an almost infinite fatigue life of the repaired plates.

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Torres Duarte, Luis M., Gonzalo Mariano Domínguez Almaraz, and Hipólito M. Venegas Montaño. "Ultrasonic fatigue testing of AISI 304 and 316 stainless steels under environmental and immersion conditions." Frattura ed Integrità Strutturale 18, no. 68 (2024): 175–85. http://dx.doi.org/10.3221/igf-esis.68.11.

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Ultrasonic fatigue tests were carried out on stainless steel AISI 316 and 304, under two modalities: at room temperature and in immersion (water for 316 and antifreeze for 304 steels); all tests were carried out with a loading ratio R=-1. The results obtained in the tests at room temperature (without immersion), for both materials exhibited a significant increase in temperature, leaving heat marks on the narrow section of the specimens. This phenomenon occurred due to the low coefficient of thermal conductivity of these stainless steels (16.2 W/ (m °K)), and the recorded temperatures were around 200 °C, generating instantaneous failure of material. Analyzes of fracture surfaces on specimens tested at room temperature reveal that crack initiation was related to the high temperature, causing alteration at the granular scale of the material, followed by a typical behavior crack propagation and failure. For specimens tested under immersion conditions, it was possible to reduce the temperature below 100 °C, which solved the problem of failure due to thermal effect. The results for 316 stainless steel immersed in water showed a fatigue life of 1.188×1010 cycles at188 MPa of stress loading in the specimen; while specimens subjected to 263 MPa stress showed a fatigue life of around 7×106 cycles, representing a significant reduction with an approximate factor of 1700. On the other hand, specimens of 304 stainless steel immersed in antifreeze with the lowest loading values of 169 MPa, showing an infinite ultrasonic fatigue life; while tests subjected to 263 MPa loading stress attains 3.62×106 cycles of ultrasonic fatigue life. The scanning electron microscopy visualizations for both cases of immersion tests showed that the initiation and propagation of the crack occurred on the surface of the specimens, exhibiting the typical mechanical fracture behavior without any apparent thermal influence.

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Tuninetti, Víctor, Diego Martínez, Sunny Narayan, Brahim Menacer, and Angelo Oñate. "Design Optimization of a Marine Propeller Shaft for Enhanced Fatigue Life: An Integrated Computational Approach." Journal of Marine Science and Engineering 12, no. 12 (2024): 2227. https://doi.org/10.3390/jmse12122227.

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This study investigates the design and potential failure modes of a marine propeller shaft using computational and analytical methods. The aim is to assess the structural integrity of the existing design and propose modifications for improved reliability and service life. Analytical calculations based on classification society rules determined acceptable shaft diameter ranges, considering torsional shear stress limits for SAE 1030 steel. A Campbell diagram analysis identified potential resonance issues at propeller blade excitation frequencies, leading to a recommended operating speed reduction for a safety margin. Support spacing was determined using both the Ship Vibration Design Guide and an empirical method, with the former yielding more conservative results. Finite element analysis, focusing on the keyway area, revealed stress concentrations approaching the material’s ultimate strength. A mesh sensitivity analysis ensured accurate stress predictions. A round-ended rectangular key geometry modification showed a significant stress reduction. Fatigue life analysis using the Goodman equation, incorporating various factors, predicted infinite life under different loading conditions, but varying safety factors highlighted the impact of these conditions. The FEA revealed that the original keyway design led to stress concentrations exceeding allowable limits, correlating with potential shaft failure. The proposed round-ended rectangular key geometry significantly reduced stress, mitigating the risk of fatigue crack initiation. This research contributes to the development of more reliable marine propulsion systems by demonstrating the efficacy of integrating analytical methods, finite element simulations, and fatigue life predictions in the design process.

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Yu, Qian, Guixin Wang, Yilong Cao, and Jiaqi Zhao. "Strength analysis of diesel engine block based on multi-body transient dynamics." Advances in Economics and Management Research 4, no. 1 (2023): 232. http://dx.doi.org/10.56028/aemr.4.1.232.2023.

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Based on the multi-body transient dynamics calculation method, the strength of a low-speed marine diesel engine block is analyzed. Firstly, UG software is used to simplify the whole machine and obtain the corresponding simplified model. Then, in ANSYS software, the corresponding loads and boundary conditions are applied to each component in the diesel engine model to simulate the normal working process of the diesel engine and calculate the structural strength of the engine block. It is found that the stress on the engine block is not constant, but changes with the rotation of the crankshaft and the explosion of each cylinder. The position of the maximum stress on the engine block appears at the bolt hole on the upper surface of the cylinder block, and is far less than the tensile yield strength of the material. Finally, the fatigue life of the computer block is calculated by importing three elements: stress distribution data, material properties and load spectrum. It is found that the mechanical fatigue life time of the engine block is much longer than the overhaul period of the diesel engine, which can be considered as infinite life.

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Journal articles on the topic 'Infinite fatigue life'

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