Academic literature on the topic 'Infinite fatigue life'
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Journal articles on the topic "Infinite fatigue life"
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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%.
Book chapters on the topic "Infinite fatigue life"
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Rodopoulos, C. A. "Infinite Life for a plate with a central hole." In Problems of Fracture Mechanics and Fatigue. Springer Netherlands, 2003. http://dx.doi.org/10.1007/978-94-017-2774-7_102.
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Rodopoulos, C. A. "Infinite life for a plate with a semi-circular notch." In Problems of Fracture Mechanics and Fatigue. Springer Netherlands, 2003. http://dx.doi.org/10.1007/978-94-017-2774-7_101.
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Weichert, Dorina, Elena Haedecke, Gunar Ernis, Sebastian Houben, Alexander Kister, and Stefan Wrobel. "Bayesian Inference for Fatigue Strength Estimation." In Cognitive Technologies. Springer Nature Switzerland, 2025. https://doi.org/10.1007/978-3-031-83097-6_6.
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Abstract A vital material property of metals is long life fatigue strength. It describes the maximum load that can be cyclically applied to a defined specimen for a number of cycles that is thought to represent an infinite lifetime. The experimental measurement of long life fatigue strength is costly, justifying the need to create a precise estimate with as few experiments as possible. We propose a new approach for estimating long life fatigue strength that defines a ready-to-use experimental and analysis procedure. It relies on probabilistic machine learning methods, efficiently connecting expert knowledge about the material behavior and the test setup with historical and newly generated data. A comparison to state-of-the-art standard experimental procedures shows that our approach requires fewer experiments to produce an estimate at the same precision—massively reducing experimental costs.
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Müller, A., Volker Trappe, S. Hickmann, and H. P. Ortwein. "Investigation of the infinite life of fibre-reinforced plastics using X-ray refraction topography for the in-situ, non-destructive evaluation of micro-structural degradation processes during cyclic fatigue loading." In Fatigue of Materials at Very High Numbers of Loading Cycles. Springer Fachmedien Wiesbaden, 2018. http://dx.doi.org/10.1007/978-3-658-24531-3_19.
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Radaj, Dieter. "Fatigue strength for infinite life of welded joints in structural steel." In Design and Analysis of Fatigue Resistant Welded Structures. Elsevier, 1990. http://dx.doi.org/10.1533/9781845698751.36.
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SOTO-MENDOZA, Gilberto, José MARTÍNEZ-GARCÍA, Jorge EDMUNDO-MASTACHE, and Luis Héctor HERNÁNDEZ-GÓMEZ. "Redesign of a fatigue machine guide plate based on topology optimization." In Handbooks Engineering Science and Technology TIX. ECORFAN, 2021. http://dx.doi.org/10.35429/h.2021.9.1.97.113.
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Machinery components are subjected to dynamic loads. In particular, the fatigue machines must be designed for these types of conditions. On the other hand, the industry demands that it is sought to consume the least amount of raw material for its construction, that is, to optimize. In general, optimization tasks have been carried out mostly by trial and error. In the present work, a redesign of a guide plate of a fatigue machine was carried out based on Topology Optimization. For this purpose, Static Structural, Topology Optimization, Fatigue and Modal Analysis were carried out. With this, a new design is obtained with a reduction in its raw material of 61%. The component was designed for infinite life so that it will not compromise its structural integrity throughout the life of the equipment operation.
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W. Al Shboul, Khalid, Husam A. Alshareef, and Hayder A. Rasheed. "Advanced Analytical Methods for Fatigue Assessment of Ancillary Systems in Highway Bridges." In Civil Engineering. IntechOpen, 2024. http://dx.doi.org/10.5772/intechopen.113811.
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Fatigue failure is a major concern for highway sign structures due to sustained wind-loading events, which have been recognized in many states. To ensure public safety, AASHTO specifies that structures should be designed for infinite life by maintaining wind-induced stress below their constant amplitude fatigue threshold (CAFT). However, existing structures that were not designed for fatigue may contain unnoticed fatigue cracks that are difficult to detect through visual inspection, which is also time-consuming. To address this issue, a simplified analytical inspection tool was developed and implemented into computer software. The tool assesses all critical components according to AASHTO specifications for fatigue and was used to examine a failed structure, which revealed a fatigue damage crack in the vertical weld of the mast-to-arm box connection at the upper chord level. In addition, a spatial interpolation technique was proposed using Isoparametric finite element shape functions to derive wind speed records for unsampled locations from actual data recorded at known locations. This provides a better understanding of the wind events that might be the driving source for fatigue failure of these flexible structures and facilitates fatigue-life prediction by generating a full range of wind loading. Overall, this chapter contributes to improving the safety and efficiency of highway sign structures by providing effective inspection tools and wind-speed interpolation techniques.
Conference papers on the topic "Infinite fatigue life"
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Mann, Michael D. "Fatigue Life of Commercial High Pressure Tubing." In ASME 2002 Pressure Vessels and Piping Conference. ASMEDC, 2002. http://dx.doi.org/10.1115/pvp2002-1163.
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Design guidance for high pressure components, has undergone a dramatic change with the release of ASME Section VIII division 3 pressure vessel code. For the first time, a thorough design criteria is available for design of thick wall pressure vessels. The most critical components of a design are safety and reliability. Ultra high-pressure vessels, in most cases, do not have an “infinite” life. The design must therefore be “leak before break” and a design cycle life must be specified. This paper looks at the effects of fatigue on commercial high-pressure tubing under tri-axial fatigue. The tubing investigated is 316 stainless steel 9/16″ and 3/8″ diameter 4100 bar (60,000 psi) tubing. The testing was performed using a tri-axial fatigue machine originally designed by Dr. B. Crossland, Dr. J. L. M. Morrison and Dr. J. S. C. Perry in 1960 and upgraded by the Author. This investigation compares the fatigue life prediction per KD3 in the ASME pressure vessel code Section VIII division 3 and actual test results from the fatigue machine. This verification gives important reliability data for commercial hardware used in high-pressure piping.
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Ozaltun, Hakan, Jeremy Seidt, M. H. Herman Shen, Tommy George, and Charles Cross. "An Energy-Based Method for Uni-Axial Fatigue Life Calculation." In ASME Turbo Expo 2009: Power for Land, Sea, and Air. ASMEDC, 2009. http://dx.doi.org/10.1115/gt2009-59512.
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An energy based fatigue life prediction framework has been developed for calculation of remaining fatigue life of in-service gas turbine materials. The purpose of the life prediction framework is to account for the material aging effect on fatigue strength of gas turbine engines structural components which are usually designed for infinite life. Previous studies [1–7] indicate the total strain energy dissipated during a monotonic fracture process and a cyclic process is a material property that can be determined by measuring the area underneath the monotonic true stress-strain curve and the sum of the area within each hysteresis loop in the cyclic process, respectively. The energy-based fatigue life prediction framework consists of the following entities: (1) development of a testing procedure to achieve plastic energy dissipation per life cycle and (2) incorporation of an energy-based fatigue life calculation scheme to determine the remaining fatigue life of in-service gas turbine materials. The accuracy of the remaining fatigue life prediction method was verified by comparison between model approximation and experimental results of Aluminum 6061-T6 (Al 6061-T6). The comparison shows promising agreement, thus validating the capability of the framework to produce accurate fatigue life prediction.
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Andoko, Riduwan Prasetya, and Femiana Gapsari. "Stress and Fatigue Life Simulation of Camshaft with Structural Static ANSYS Approach." In International Conference on Mechanical Engineering. Trans Tech Publications Ltd, 2023. http://dx.doi.org/10.4028/p-4ker16.
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The failure occurred in the camshaft of the minibus vehicle after 14 years of use and a failure analysis was carried out to find the cause. The purpose of this paper is to simulate a failed camshaft by evaluating stress and fatigue using the ANSYS structural static approach to find the cause of the failure. Camshaft meshed with a size of 5 mm for the outer part of the fracture and 3 mm on the fracture. The load given is force (1400 N) and torque (113 Nm) and the support is fixed support on the second bearing. The stress shows that the applied load does not because fracture based on the theory of maximum normal stress and Mohr's criteria, the location of the highest and lowest stresses is not in the fault area, and fatigue life without defects produces infinite cycles or will not fail, and fatigue life simulation with defects results in a reduction in life. Based on these parameters, failure is caused by defects in the fractured part with an indication of the location of the fracture beyond the greatest potential for fracture and lower fatigue life.
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Francis, Benjamin, and David Mair. "An Efficient Method of Estimating Spectral Fatigue Damage for Low RMS Stress Ranges and Arbitrary Fatigue Curves." In ASME 2022 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/pvp2022-84596.
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Abstract In recent years API 579 has provided the analyst with a detailed outline of cycle counting techniques for uni-axial loading (the Rainflow Cycle Counting (RCC) method: ASTM Standard No. E1049 three-point method) and multi-axial loading (the Wang-Brown algorithm (WBCC)). However, for vibration-based fatigue, in the absence of any time history at all; it is common in industry to assess fatigue using frequency domain techniques. The most accurate frequency domain techniques, such as the ever-popular Dirlik’s method, are optimized for a very restricted class of fatigue curve. In closed form Dirlik’s method is only applicable to the class of fatigue curves that exhibit a constant fatigue stress exponent over the number of cycles. In more general settings the validity of the Dirlik probability density is most accurate when the curve power (i.e. ‘m’ where m ≡ h−1 and ‘h’ is found in API 579 Table 14B.3 or ASME VIII Div. 2 Table 3-F.2) is ∼3.0, and is arguably only applicable between 2 to 5. API 579 Method A provides the ‘smooth bar’ fatigue curves, which are described by a polynomial relationship in which m will often approach 20 at very large numbers of cycles. The alternative technique of API 579 Method C for assessing welds, does comply with the fatigue curve restrictions (i.e. m = 3.13 for ferritic and stainless steel and m = 3.61 for Aluminum). However, this method could arguably be augmented with an increased stress exponent at large numbers of cycles and beyond that an infinite life (e.g. BS EN 13445-3 where N = 5 × 106 is infinite life for monotonic loading and a transition to m = 5 for variable amplitude loading followed by infinite life at N = 108). While it is not the claim of this paper, this would be conceptually consistent with the minimum propagating crack size of fracture mechanics, which is the theoretical basis for the Method C approach. This paper follows on from previous work (PVP2020-21392 [1]) and presents a detailed algorithm for constructing fatigue curve specific cycle count correlations in the spirit of the Dirlik cycle counting. As such these correlations are primarily sensitive to the spectral moments. These correlations are based on specific functions of the spectral moments, functions that have been found to produce reliably low scatter with respect to RCC. In addition to the traditional 5 spectral moments, we show that, at very large fatigue curve stress exponents, the spectral entropy can be used to enhance the accuracy of the estimated cycle count. These parameters (5 spectral moments and spectral entropy) are very cheap to calculate in the spectral domain, making this method very computationally efficient. The algorithm also makes it possible for the user to choose the confidence interval on the scatter data. In this way, with some care, the user can naturally account for the inherent hyper-sensitivity of the high cycle part of the fatigue curve to atypically large stress events. Both of these characteristics make this technique suitable for rapid virtual prototyping and subsequent design optimization in real world quick turn-around fitness for service remediation applications.
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Abu-Jadayil, Wisam M., and Donald R. Flugrad. "Optimization of Fatigue Life of Hollow Rollers Under Pure Normal Loading." In ASME 8th Biennial Conference on Engineering Systems Design and Analysis. ASMEDC, 2006. http://dx.doi.org/10.1115/esda2006-95035.
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Fatigue life investigations have been made for hollow rollers in pure normal loading. Different hollowness percentages between 20% and 80% have been tested to find the optimum percentage hollowness that gives the longest fatigue life. Two main models were built for this purpose. Model 1 with two identical sized rollers and Model 2 with two non identical sized rollers. In each model, two cases have been studied, when both rollers are hollow and the case when one roller is hollow while the other one is solid. The Ioannides-Harris (IH) theory was used to calculate the relative fatigue life of the hollow rollers with respect to solid rollers under same loading. Investigations have been made for five different materials, CVD 52100, Carburized steel, VIMVAR M50, M50NiL and Induction-hardened steel. The finite element package ABAQUS has been used to study the stress and deformations in the loaded rollers. In general, the optimum hollowness percentage with the longest fatigue life ranges between 60% and 70% based on the kind of the material, whether the rollers are same size or different size and whether both rollers are hollow or only one of them is hollow. Using IH theory for fatigue life calculation resulted in having infinite fatigue life for those rollers made of Induction-hardened steel that relatively has high fatigue limit value. Rollers in the optimum range are flexible enough to get the best redistribution the stress in the contact zone. For models of a hollow cylindrical roller in contact with a solid roller, the optimum hollowness is around 70%. When both cylindrical rollers are hollow, the optimum hollowness decreases to be between 60% and 65%. At the optimum hollowness, small differences in the fatigue life have been found between models of one hollow roller and models of two hollow rollers. Even though, having both rollers hollow means less weight, saving more material and more stability for the system.
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Koay, Kenny, Brad Bracht, and Vance Browne. "Fatigue Analysis of a Welded Lap Joint Under Bending Load." In ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-32303.
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Welded lap joints subject to cyclic loading are used in industrial vehicles and equipment. Cyclic bending loads can result in fatigue failure of these joints. It is desirable to predict the expected life of the joint as a function of a load-stress parameter. To predict the life of a typical welded structure, additional types of weld joints and loads must also be considered. The lap joint work covered here provides a building block for the structure life prediction. For the work reported here, lap joints were formed by an industrial manufacturing wire feed weld process by certified welders. Strain gages were applied to one of the joint members. A fixture was designed and built to apply a pure bending load to the welded members at the joints, and this was installed in a fatigue test machine. A number of fully reversed tests were run to failure at various loads and some were run to effective infinite life. A resulting set of stress life curves was generated based on mean life and mean life less one and two standard deviations as a function of the “hot spot” stress. This hot spot is the region near the weld toe where the stress distribution starts to deviate from linearity due to the geometric stress riser of the weld fillet and joint geometry. Measurements show that this stress can be approximated by the calculated beam bending stress for the specimens and loads used in the tests. The results of this work provide guidelines for design of welded lap joints for a desired cycle life and for predicting the expected cycle life of an existing joint including uncertainties in life due to weld and test variables. The stress needed to predict the life of a joint is obtained by strain measurements on the actual structure. For design, the stress may be approximated by calculated stresses.
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Verges, Melody Arthur, and Geetha Chilakamarthi. "The Influence of Underfill Properties on the Fatigue Life of Ball Grid Array Packages." In ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-59970.
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The influence of underfill material properties on the fatigue life of a Ball Grid Array (BGA) package in the presence of thermal cycling is investigated in this study. The underfill material properties that are varied include Young’s modulus, Poisson’s ratio, and the coefficient of thermal expansion. The range in values are in accordance with typical underfills used in packages today. A finite element model is created using general purpose Ansys code by assuming that there exists an infinite array of solder interconnects, cylindrical in shape, surrounded by underfill material. The finite element geometry generated consists of a unit cell of concentric cylinders, with the inner being solder material and the outer being underfill material. The interconnect material is modeled as eutectic solder that behaves elastically-perfectly plastic. The Mode I cyclic stresses in the solder are determined as a temperature loading is applied. These stresses are then compared to the residual compressive stresses that are induced as a result of underfill shrinkage upon curing. Results suggest that Mode I stresses induced in the interconnects upon thermal cycling are not negligible in comparison to the beneficial compression that they provide upon curing. Even in the presence of this residual compression, for several material combinations a substantial amount of tension is induced in the connections while being cycled.
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Ogata, Takashi, and Masato Yamamoto. "Biaxial Thermo Mechanical Fatigue Life Propety of a Ni Base DS Super Alloy." In ASME Turbo Expo 2006: Power for Land, Sea, and Air. ASMEDC, 2006. http://dx.doi.org/10.1115/gt2006-90758.
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Development of life assessment methods of high temperature components in gas turbine for maintenance and operating cost reduction is strongly demanded by Japanese utilities. Especially, first row blades are subjected to complicated. Thermo-Mechanical-Fatigue (TMF) loading during start-steady state-stop cycles. Therefore it is important to clarify the TMF life property of blade materials to develop a life assessment procedure. In this study, tension-torsion biaxial TMF tests have been performed between 450C and 870C on a Ni base directional solidified (DS) supper alloy. Strain ratio, φ was defined as shear strain range, Δγ, to normal strain range, Δε, and φ varied from 0 to infinite. The “Blade waveform” which simulated surface temperature and strain loading condition of the blade, was employed. The biaxial TMF tests were also carried out on coated specimens with CoCrAlY. Fatigue life under biaxial TMF loading showed strain ratio dependency giving shorter life with increasing φ. Considering biaxial stress effect on failure life, an equivalent shear strain range was derived based on Γ -plane theory, and biaxial TMF life was well correlated with the equivalent shear strain range. The biaxial TMF life was reduced by introducing strain hold duration at the maximum temperature. The maximum stress increased by introducing the hold time due to increasing mean stress level in the Blade waveform. It was concluded that creep damage gradually accumulated during cycles resulting in TMF life reduction. The nonlinear creep-fatigue damage accumulation model was applied to predict failure life of the hold time tests. As a result, failure life could be predicted within factor of 1.5 on observed life. It was found that fatigue life of CoCrAlY coated material reduced 1/2 to 1/3 from that of without coated material. From observation of longitudinal section of the coated specimens, many cracks started from coating surface and penetrated into the substrate. It was concluded that CoCrAlY coating reduced the biaxial TMF life due to acceleration of crack initiation period in the substrate.
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Trevino, Alexis, Arturo A. Fuentes, Constantine M. Tarawneh, and Joseph Montalvo. "Fatigue Life Estimation of Modified Railroad Bearing Adapters for Onboard Monitoring Applications." In 2015 Joint Rail Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/jrc2015-5790.
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This paper presents a study of the fatigue life (i.e. number of stress cycles before failure) of Class K cast iron conventional and modified railroad bearing adapters for onboard monitoring applications under different operational conditions based on experimentally validated Finite Element Analysis (FEA) stress results. Currently, freight railcars rely heavily on wayside hot-box detectors (HBDs) at strategic intervals to record bearing cup temperatures as the train passes at specified velocities. Hence, most temperature measurements are limited to certain physical railroad locations. This limitation gave way for an optimized sensor that could potentially deliver significant insight on continuous bearing temperature conditions. Bearing adapter modifications (i.e. cut-outs) were required to house the developed temperature sensor which will be used for onboard monitoring applications. Therefore, it is necessary to determine the reliability of the modified railroad bearing adapter. Previous work done at the University Transportation Center for Railway Safety (UTCRS) led to the development of finite element model with experimentally validated boundary conditions which was utilized to obtain stress distribution maps of conventional and modified railroad bearing adapters under different service conditions. These maps were useful for identifying areas of interest for an eventual inspection of railroad bearing adapters in the field. Upon further examination of the previously acquired results, it was determined that one possible mode of adapter failure would be by fatigue due to the cyclic loading and the range of stresses in the railroad bearing adapters. In this study, the authors experimentally validate the FEA stress results and investigate the fatigue life of the adapters under different extreme case scenarios for the bearing adapters including the effect of a railroad flat wheel. In this case, the flat wheel translates into a periodic impact load on the bearing adapter. The Stress-Life approach is used to calculate the life of the railroad bearing adapters made out of cast iron and subjected to cyclic loading. From the known material properties of the adapter (cast iron), the operational life is estimated with a mathematical relationship. The Goodman correction factor is used in these life prediction calculations in order to take into account the mean stresses experienced by these adapters. The work shows that the adapters have infinite life in all studied cases.
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Wang, Qiliang, and Xianmin Zhang. "Fatigue Life Prediction and Optimal Design of a Flexure Based Micro-Motion Stage." In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-63581.
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This paper presents a fatigue-based method for optimal design of a flexure based 3-RRR compliant micro-motion stage, which is driven by three piezoelectric actuators (PZT). As this compliant stage obtains motions from the deflection of its flexure hinges, fatigue failure becomes its major failure mode. The aim of this paper is to provide a method to predict the fatigue life of the stage and redesign it by considering fatigue strength. Firstly, the motion transformation matrix, which reveals the relation between output displacement vector of moving platform and three input displacements of PZT actuators, is established by using the finite element method. Then, the force vectors of all the twelve flexure elements in the stage can be derived. Secondly, the fatigue properties of circular flexure hinge are discussed by considering the effects of flexure dimension parameters, non-zero mean stress, surface conditions and et al. Combined with the material stress life curve and the fatigue strength of the flexure hinges, fatigue life prediction of the micro-motion stage can be carried out by utilizing the nominal stress approach. The aforementioned micro-motion stage, which is optimized based on maximum stress constraint, is presented as an example to illustrate the fatigue life prediction procedure. And the predicted results of fatigue lives in specified condition indicate that fatigue lives of all flexure hinges in the stage differ drastically. In this condition, the stage will fail prematurely due to the most vulnerable hinge. So, the design method based on static strength may lead to unsafe or uneconomic design of the stage. Finally, a fatigue based optimal design method is introduced to redesign the flexure based micro-motion stage. The stage dimensions and the flexure hinge geometry are considered as design variables. The maximum motion range is set as the objective function. And the fatigue strength of flexures is taken as constraint, as well as the natural frequency of the stage and the input force capacity of PZT actuators. A micro-motion stage with optimal dimension parameters is obtained at last. Numerical results show that the optimal stage has a good comprehensive properties and can endure a infinite cycles.
Reports on the topic "Infinite fatigue life"
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PERFORMANCE OPTIMIZATION OF A STEEL-UHPC COMPOSITE ORTHOTROPIC BRIDGE WITH INTELLIGENT ALGORITHM. The Hong Kong Institute of Steel Construction, 2022. http://dx.doi.org/10.18057/icass2020.p.160.
Full textAbstract:
To address the problems of pavement damage and fatigue cracking of orthotropic steel deck (OSD) in bridges, an innovative composite bridge deck composed of OSD with open ribs and ultra-high performance concrete (UHPC) layer was proposed. Firstly, the stress responses of fatigue-prone details in the composite bridge deck were investigated by refined two-scale finite element analysis. The results show that the rib-to-deck joint can achieve an infinite fatigue life, while the floorbeam detail of rib-tofloorbeam joint indicates finite fatigue life. Then, response surface models of stress ranges of fatigue details and structure weight were derived via both the central composite design and response surface method. Finally, to improve the fatigue performance for achieving an infinite fatigue life under relatively low structure weight, the multi-objective optimization was executed by an Improved Non-dominated Sorting Genetic Algorithm (NSGA-II). The obtained Pareto front shows that there is a strong competition between the stress range of fatigue-prone detail and structure weight.