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1
Gao, Ruofan, and Jie Li. "Equivalent constant-amplitude fatigue load method based on the energy equivalence principle." Advances in Structural Engineering 22, no. 13 (June 5, 2019): 2892–906. http://dx.doi.org/10.1177/1369433219852705.
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An equivalent constant-amplitude cyclic loading method for random vehicle load is proposed based on the concept of energy equivalence. The filtered compound Poisson process is adopted to describe random vehicle load, through which the vehicle load spectrum is gained. The total dissipated energy due to fatigue loads subjected to concrete structures is deduced by introducing a multi-scale model, in which the energy dissipation induced by the nano-cracks level is presented, and the energy transition from nano to macro scales is derived. By assuming that the total energy dissipation under random loading equals that under equivalent constant-amplitude loading, the equivalent load ratio and amplitude as well as the number of equivalent cycles for random vehicle load are obtained. To validate the effectiveness of the proposed method, a set of numerical simulations is presented. The fatigue damage accumulations for concrete structures under both the random load and the equivalent loads converted by the proposed method and the classic root mean square method are calculated. By comparing with the root mean square method, the accuracy and advantage of the proposed equivalent load model are verified.
2
Zuo, Huang, Yue Chun Zhang, Ping Liu, Wen Wang, and Shun Xiong. "Study on Loads of Accelerated Contact Fatigue Testing and its Application." Applied Mechanics and Materials 86 (August 2011): 680–83. http://dx.doi.org/10.4028/www.scientific.net/amm.86.680.
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For reducing the development time and cost, determining the load of accelerated contact fatigue testing of a multi-case and multi-stage drive train, multilevel design load method was used to calculate the pitting equivalent loads of gears according to the load spectrum. A reasonable load of pitting fatigue testing was determined after analyzing and studying the pitting equivalent loads of gears. Based on a reducer used for a cement mixer, the pitting equivalent loads of gears were calculated, and the load of pitting fatigue testing was determined. The damage ratios of gears were calculated by the pitting equivalent loads of gears and the testing load, separately, using software MASTA. The results from the load of pitting fatigue testing and the testing load were coincident.
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Ligaj, Bogdan, and Robert Sołtysiak. "Problems of Equivalent Load Amplitude in Fatigue Life Calculations." Polish Maritime Research 23, no. 1 (January 1, 2016): 85–92. http://dx.doi.org/10.1515/pomr-2016-0012.
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Abstract This paper presents issues of fatigue life calculations in operational load conditions. The assumed runs were so processed as to get a set of sinusoidal cycles by using the following methods: full cycles counting method and rainflow counting method. On the basis of such sets of cycles of the varying parameters Sm i and Sa i were prepared block load spectra of equivalent amplitudes Saz , obtained with the use of an original method of these authors, in which two-parameter fatigue characteristics were applied. The work resulted in comparison of fatigue life results for load spectra determined by using the assumed cycles counting methods and the assumed two-parameter fatigue characteristics: the model IM, model II, model III and model IV, respectively.
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Xu, Ge Ning, Xiao Ning Fan, Feng Yi Lu, and Rui Gang Yang. "The ANN Method of Obtaining Fatigue Load Spectrum of Overhead Traveling Crane." Applied Mechanics and Materials 20-23 (January 2010): 525–31. http://dx.doi.org/10.4028/www.scientific.net/amm.20-23.525.
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For the realization of remaining fatigue life estimation, prevention of catastrophic accidents and safety of the cranes in service, it is necessary to obtain the actual load spectrum of overhead traveling crane. Due to the limitation of condition in field experiment, it is difficult to implement a large number of actual Load Spectrum experiments. So, the present paper will focus on overhead traveling cranes for general purpose and conduct data investigation. In a certain period，the numbers of work cycles corresponding to different lifting loads for different rated lifting capacity are collected. Based on Levenberg-Marquardt Back Propagation(LMBP) Artificial Neural Network(ANN), the equivalent load spectrum, which is equivalent to the actual load spectrum, is acquired. The example demonstrates: It is feasible to establish the equivalent load spectrum for some types of crane using ANN. Meanwhile, the equivalent load spectrums of the typical cranes in this type could be obtained and predicted through the trained network. It has provided the reliable data for the reliability analysis and fatigue life estimation of the crane. In the approach to establish the crane load spectrum, an exploring and initiating study work have been done.
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Zhu, Hong Bing. "Calculation Methods for Equivalent Fatigue Stress Amplitude Based on Corten-Dolan Accumulative Damage Rule." Advanced Materials Research 156-157 (October 2010): 1271–74. http://dx.doi.org/10.4028/www.scientific.net/amr.156-157.1271.
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Structures often enduring random amplitude load or multilevel amplitude load. However, the test researches on fatigue often using equivalent amplitude load. It is very important for fatigue research that how to accurately evaluate structure’s fatigue properties of random amplitude load or multilevel amplitude load when only using equivalent amplitude load fatigue test results. According to damaging degree equivalent principle of multilevel amplitude load or random amplitude load, deduced equivalent stress amplitude calculation formula using linearity Miner accumulative damage rule and Corten-Dolan accumulative damage rule. Introduced the formula’s using method on fatigue detail or fatigue life evaluation. Utilizing the S-N curve and S-N equation from RC beams fatigue experiment, verified the formula aiming at 3 RC beams’ random amplitude fatigue experiment results, and it is indicated that the formula’s results had quite high precision and approached the experimentation result though it is partial security. The formula operated convenience and it had higher precision compared to similar formula, so the formula suit for engineering application.
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Miao, Yizhi, Mohsen N. Soltani, and Amin Hajizadeh. "A Machine Learning Method for Modeling Wind Farm Fatigue Load." Applied Sciences 12, no. 15 (July 22, 2022): 7392. http://dx.doi.org/10.3390/app12157392.
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Wake steering control can significantly improve the overall power production of wind farms. However, it also increases fatigue damage on downstream wind turbines. Therefore, optimizing fatigue loads in wake steering control has become a hot research topic. Accurately predicting farm fatigue loads has always been challenging. The current interpolation method for farm-level fatigue loads estimation is also known as the look-up table (LUT) method. However, the LUT method is less accurate because it is challenging to map the highly nonlinear characteristics of fatigue load. This paper proposes a machine-learning algorithm based on the Gaussian process (GP) to predict the farmlevel fatigue load under yaw misalignment. Firstly, a series of simulations with yaw misalignment were designed to obtain the original load data, which considered the wake interaction between turbines. Secondly, the rainflow counting and Palmgren miner rules were introduced to transfer the original load to damage equivalent load. Finally, the GP model trained by inputs and outputs predicts the fatigue load. GP has more accurate predictions because it is suitable for mapping the nonlinear between fatigue load and yaw misalignment. The case study shows that compared to LUT, the accuracy of GP improves by 17% (RMSE) and 0.6% (MAE) at the blade root edgewise moment and 51.87% (RMSE) and 1.78% (MAE) at the blade root flapwise moment.
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Natarajan, Anand. "Damage equivalent load synthesis and stochastic extrapolation for fatigue life validation." Wind Energy Science 7, no. 3 (June 2, 2022): 1171–81. http://dx.doi.org/10.5194/wes-7-1171-2022.
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Abstract. Present verification of the fatigue life margins on wind turbine structures utilizes damage equivalent load (DEL) computations over a limited time duration. In this article, a procedure to determine long-term fatigue damage and remaining life is presented as a combination of stochastic extrapolation of the 10 min DEL to determine its probability of exceedance and computationally fast synthesis of DELs using level crossings of a Gaussian process. Both the synthesis of DELs and long-term stochastic extrapolation are validated using measured loads from a wind farm. The extrapolation for the blade root flap and tower base fore–aft damage equivalent moment is presented using a three-parameter Weibull distribution, whereby the long-term damage equivalent load levels are forecast for both simulated and measured values. The damage equivalent load magnitude at a selected target probability of exceedance provides an indicator of the integrity of the structure for the next year. The extrapolated damage equivalent load over a year is validated using measured multi-year damage equivalent loads from a turbine in the Lillgrund wind farm, which is subject to wakes. The simulation of damage equivalent loads using the method of level crossings of a Gaussian process is shown to be able to reconstruct the damage equivalent load for both blade root and tower base moments. The prediction of the tower base fore–aft DEL is demonstrated to be feasible when using the Vanmarcke correction for very narrow band processes. The combined method of fast damage equivalent load computations and stochastic extrapolation to the next year allows a quick and accurate forecasting of structural integrity of operational wind turbines.
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Jung, Dong Soo, Hyoung Eui Kim, Sung Hun Kim, and E. Sok Kang. "Development of Accelerated Life Test Method of Hydraulic Pump." Key Engineering Materials 326-328 (December 2006): 1861–64. http://dx.doi.org/10.4028/www.scientific.net/kem.326-328.1861.
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This paper proposes a new accelerated life test method of hydraulic pump used in vehicles, which have multiple alternating loads. For determination of life time of hydraulic pump for given field conditions with respect to duty cycle, the equivalent load and speed of this unit has to be determined. Equivalent load and speed can be calculated from the given duty cycle using the predominant theory for cumulative fatigue damage. Finally, we can perform accelerated life test on hydraulic pump by determination of test pressure and speed from calculated equivalent cumulative damage per working cycle and weighted average speed.
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Zhao, Min, and Jin Di. "Fatigue Load for Cable-Girder Anchorage Structure of Highway and Light-Railway Cable Stayed Bridge." Advanced Materials Research 838-841 (November 2013): 1028–33. http://dx.doi.org/10.4028/www.scientific.net/amr.838-841.1028.
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Because fatigue load of bridge structure under the highway and light-railway loads has not been specified in current design codes, it is necessary to study the fatigue load of cable-girder anchorage structure of the highway and light-railway cable stayed bridge. Take Chongqin Hongyan Jialing River bridge as the subject of investigation, the fatigue load of cable-girder anchorage structure is computed through MatLab program developed by Monte Carlo method and the rain flow method. According to the traffic flow surveys on the load spectrum, the fatigue load of cable-girder anchorage structure was calculated accurately by the MatLab program. Through comparison with the calculation results of the MatLab program, a fatigue load calculation method used equivalent fatigue vehicle based on the Palmgren-Miner linear cumulative damage theory is reliable and accurate.
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Wang, Lei, Fa Ming Wu, Xing Mei Lv, and Dian Wang. "A Fatigue Analysis Method Research for Main Frame of the Large-Scale Wind Turbine." Applied Mechanics and Materials 226-228 (November 2012): 995–99. http://dx.doi.org/10.4028/www.scientific.net/amm.226-228.995.
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This paper presents a method to calculate the main frame damage of fatigue directly by the equivalent fatigue load of the wind turbine. This method can take advantage of the equivalent fatigue load to check the damage of the main frame fast. This paper also analyses the weight of each components of the fatigue load, which is convenient for the optimization design of the structure for main frame. Comparing this method with traditional fatigue calculation method, we can find this method is reasonable and veracious. Using this method can greatly improve the efficiency of the damage estimate for the main frame. It can be analogized to other mechanical components, and this method is very valuable in practical engineering applications.
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Liu, Fangping, Chen Yu, and Wentao Yi. "Study on equivalent static method for the analysis of fatigue behavior of reinforced concrete beam." E3S Web of Conferences 272 (2021): 02018. http://dx.doi.org/10.1051/e3sconf/202127202018.
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In order to analyze the whole process of fatigue behaviours of reinforced concrete beams, an equivalent static analysis method is proposed in this paper. Firstly, the constitutive models based on the degradation of stiffness and strength and the accumulation of residual strain of concrete and reinforcement subjected to fatigue loadings are deduced and established by coupling the uniaxial constitutive model of concrete and the ideal elastic-plastic model of reinforcement under static load. Secondly, based on the similarity of concrete failure under static load and fatigue load, the equivalent relationship between fatigue and static analysis can be constructed by using the concrete residual strain as the equivalent parameter. On this basis, an equivalent static method for the analysis of fatigue behavior of reinforced concrete beam is proposed. At last, three reinforced concrete beams with rectangular section are tested, and the fatigue behaviours are analyzed by the method proposed in this paper. The numerical simulation results are compared with the field test data. The result shows that the numerical simulation results are in good agreement with the experimental results, which verifies the reliability and practicability of the method.
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Hao, Guang Bo, and Li Yang Xie. "Damage Equivalent Method of Fatigue Reliability Analysis of Load-Sharing Parallel System." Advanced Materials Research 44-46 (June 2008): 853–58. http://dx.doi.org/10.4028/www.scientific.net/amr.44-46.853.
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As for load-sharing parallel system like multi-engine system and wire cable, dependence-failure must occur due to load redistributing, so the component life distributions changed. After the analysis of the disadvantage of failure probability equivalent principle and the transformation of equivalent working time of different life distribution based on damage equivalent principle, the parallel system reliability model applying full probability formula is established. The established reliability model provides a new method for reliability analysis of load-sharing parallel system whose component life follows any distribution.
13
Fu, Huawei, Xuhong Zhou, Qishi Zhou, Ping Xiang, Zhibin Zhou, and Qiang Fu. "An Improved Model for Design Fatigue Load of Highway Bridges Considering Damage Equivalence." Buildings 12, no. 2 (February 15, 2022): 217. http://dx.doi.org/10.3390/buildings12020217.
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Reasonable fatigue load should be determined before bridge fatigue analysis. However, the design frequency calculation method of the standard vehicle does not always make sense when the standard vehicle load model that is provided by existing standards is adopted, as the weights (equivalent coefficients) variation of different vehicle types are not considered from the perspective of damage equivalence. The method through direct damage calculation is workable but the process is usually laborious and time-consuming. To solve this problem, the traffic data of 35 highway sites involving 15 provinces in China were collected and the fatigue load spectrum were derived. The equivalent coefficients of each vehicle type at all of the 35 locations were calculated directly and the relationship with the corresponding gross vehicle weight was obtained formulaically through statistical analysis. Therefore, the design frequency of the standard vehicle can be calculated by the product of the actual frequency for a certain type of vehicle and the corresponding equivalent coefficient. The effectiveness of the proposed method was verified from the perspective of damage equivalence compared with the existing-standard method, and its flexibility and applicability for complex traffic conditions such as China were also demonstrated. In addition, three grades for the design frequency were put forward as references in relevant project design.
14
Gao, Ruyu, Qin Xin, Xiuquan Hu, and Chunyu Liang. "RESIDUAL PERFORMANCE ANALYSIS OF BRIDGE STRUCTURE CONSIDERING HEAVY LOAD EFFECT." DYNA 97, no. 2 (March 1, 2022): 156–61. http://dx.doi.org/10.6036/10440.
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The structural performance of bridges eventually decreases, and risk in bridge operations increase, as well as the equivalent effect of vehicle loads, particularly heavy traffic. To further clarify the relationship between the residual performance of the bridge under heavy traffic and the fatigue damage, a batch of prestressed concrete fatigue test beams was designed. The equivalent fatigue load, considering the heavy load effect, was determined through investigation and statistics of actual traffic load data. The fatigue failure morphology and crack development of the test beam under the equivalent fatigue load were analyzed based on the fatigue damage principle. The constant amplitude fatigue test method was used to analyze the development law of concrete residual strain, non-prestressed tendon residual strain, and prestressed tendon residual strain. Based on the damage model theory, the damage equation between the damage variable D and the cumulative residual plastic strain ?p considering the effects of heavy traffic was found. In addition, through the test data, the fatigue damage evolution curve based on the development of residual strain was obtained. Research results show that the fatigue test failure is a bending failure of the non-prestressed tendon fatigue fracture. The fatigue life of the beam reduced drastically when the heavy load effect is considered. From the perspective of residual performance, the residual strain of concrete is a good indicator for calculating the fatigue damage index of beams. The research results provide an early warning of fatigue failure and performance evaluation.
15
Liu, Wang, Wang, Zhu, and Lio. "Active Power Dispatch for Supporting Grid Frequency Regulation in Wind Farms Considering Fatigue Load." Energies 12, no. 8 (April 21, 2019): 1508. http://dx.doi.org/10.3390/en12081508.
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This paper proposes an active power control method for supporting grid frequency regulation in wind farms (WF) considering improved fatigue load sensitivity of wind turbines (WT). The control method is concluded into two parts: frequency adjustment control (FAC) and power reference dispatch (PRD). On one hand, the proposed Fuzzy-PID control method can actively maintain the balance between power generation and grid load, by which the grid frequency is regulated when plenty of winds are available. The fast power response can be provided and frequency error can be reduced by the proposed method. On the other hand, the sensitivity of the WT fatigue loads to the power references is improved. The explicit analytical equations of the fatigue load sensitivity are re-derived to improve calculation accuracy. In the process of the optimization dispatch, the re-defined fatigue load sensitivity will be used to minimize fatigue load. Case studies were conducted with a WF under different grid loads and turbulent wind with different intensities. By comparing the frequency response of the WF, rainflow cycle, and Damage Equivalent Load (DEL) of the WT, the efficacy of the proposed method is verified.
16
Do, Van Si. "EVALUATING FATIGUE LIFE OF THE BUTT WELDED JOINTSUNDER THE EFFECT OF RANDOM LOADING." Journal of Science and Technique 15, no. 2 (June 23, 2020): 5–13. http://dx.doi.org/10.56651/lqdtu.jst.v15.n02.119.
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This paper presents the calculation results from theoretical models and experimental results in determining the fatigue life of butt welded joints subjected to random loads. The theoretical calculating the fatigue life of the butt welded joints was developed on the basis of different methods for calculating of common details published previously. Experiments on determining the butt welded joints’ fatigue life were carried out on theLDS V830vibration test system with the load equivalent to the load used in theoretical calculation.The accuracy of different calculation methods was assessed by comparison of the calculation results and experiment results. With the lowest deviation of 5.6% compared to the experiment results, Dirlik's calculation method is the most suitable to calculate fatigue life of butt welded joints subjected to random loads.
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Ma, Xiqiang, Fang Yang, Jishun Li, Yujun Xue, and Zhiqiang Guan. "Fatigue life assessment method of in-service mechanical structure." Advances in Mechanical Engineering 13, no. 2 (February 2021): 168781402199652. http://dx.doi.org/10.1177/1687814021996524.
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The most usual failure mode of any mechanical structure is fatigue, which is characterized by an important feature of the decrease of elastic modulus of the material. In this paper, a fatigue life evaluation model based on equivalent elastic modulus is proposed for in-service mechanical structure. In the proposed model, parameters that represent the operating conditions of the mechanical structure, such as load, vibration, and shaft torque, etc., are used as the generalized load. To replace the fatigue stress, the statistical method is used here, which is also used in the conventional fatigue analysis method. The structural strain is also measured simultaneously. Using the statistical theory, the equivalent modulus of elasticity is formulated based on the relationship of stress, strain, and modulus of elasticity. To validate the proposed model, an online fatigue damage experiment has been conducted. The experimental results have been compared with that of the fatigue life prediction model with good agreement. It is expected that the methodology proposed in this paper will be widely used.
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Zhou, Donglong, and Jianlong Chang. "Fatigue Analysis of a Light Truck Rear Axle Based on Virtual Iteration Method." Shock and Vibration 2022 (May 20, 2022): 1–13. http://dx.doi.org/10.1155/2022/8598491.
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Firstly, the MBD (multi-body dynamics) model of the whole vehicle is built according to the measured vehicle parameters. Then, the road spectra acquisition test is carried out. Under the test road conditions, the acceleration, displacement, and force signals of multiple positions of the whole vehicle are collected. Taking the road test signals as the iterative target and the vehicle MBD model as the iterative carrier, the vehicle equivalent excitation is obtained by using the VIM (virtual iteration method). By applying the equivalent excitation obtained by VIM to the vehicle MBD model, the load spectra of key points of the driving rear axle are obtained. The accuracy of the model is verified by comparing the measured signals with the iterative signals, and the reliability of the key points load spectra is enhanced. Secondly, the FEA (finite element analysis) model of the rear axle is built, and the static analysis results of each key point under unit load are obtained with the help of FEA software. Thirdly, the FEA results, key points load spectra, and material fatigue characteristic curve of the rear axle are input into the fatigue software to conduct the fatigue simulation of the rear axle. According to the fatigue analysis results, the position where the fatigue life does not meet the set goal is accurately located. Finally, the structure is optimized based on the above results. The fatigue life evaluation of the optimized rear axle shows that its durability has been significantly improved.
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Cheng, Wangquan (Winston), Shan Shih, John Grace, and Wenke Tu. "Axial Load Effect on Contact Fatigue Life of Cylindrical Roller Bearings." Journal of Tribology 126, no. 2 (April 1, 2004): 242–47. http://dx.doi.org/10.1115/1.1614823.
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Besides primarily carrying radial load, cylindrical roller bearings with flanges or lips on both inner and outer raceways need also carry axial load in some applications. Because of the axial load, the equivalent dynamic load of the bearing will be increased and the bearing contact fatigue life will be decreased accordingly. The axial load effect on the roller bearing fatigue life had been studied by researchers in the past. Because of different assumptions used in their models, quite different predictions were made in their analysis. This work combines the methods used in the Fernlund-Synek and Brandlein models and studies general contact conditions such as partial contact along the roller length, partial loading zone of the bearing race, manufacturing tolerance and running-in effects on roller length, etc. New formulas for equivalent dynamic loads of the rotating and stationary races are derived. A fatigue limit load is also included in the life calculation to reflect the latest development in contact fatigue life analysis.
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Bailey, Ted E., and Robert W. Frayer. "Prediction of Equivalent Radial Loads for Tapered Roller Bearings." Journal of Tribology 118, no. 3 (July 1, 1996): 651–56. http://dx.doi.org/10.1115/1.2831587.
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Calculating the fatigue life of a tapered roller bearing has become a rather straightforward exercise thanks to the accumulation of rolling contact fatigue data and the subsequent development of formulation relating applied loading to bearing fatigue life. An integral part of the prediction process is to define an equivalent radial load (EQRL) by combining a bearing’s applied radial and thrust loading into a single entity. This paper reviews currently accepted formulation and offers a potentially more accurate alternative method for estimating the EQRL of a tapered roller bearing than does the current AFBMA standard.
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Gao, Pu, Qing Tian Su, Chong Wu, Yi Ming Sun, and Hai Yan Liu. "Fatigue Performance of Deck Slab under Hogging Moment in Continuous Composite Girder Bridge." Advanced Materials Research 255-260 (May 2011): 1142–46. http://dx.doi.org/10.4028/www.scientific.net/amr.255-260.1142.
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Based on the vehicle load model for fatigue design, the stress influence line of the reinforcement in the concrete slab of northern approach of Jiubao bridge, a multi-span continous composite bridge, under the global live load was obtained by spatial frame structure finite element model, while the stress history of the reinforcement under the local live load was obtained by the spatial refined finite element model. Then the stress spectrums under global and local live load were obtained by Rain-flow method according to the predicted traffic volume in the future 100 years and comparisons of amplitudes of equivalent stress under different loads were achieved. At last the fatigue lives of the slab under the different loads were calculated and compared either.
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Yang, Tian Cun, Yan Qin Sun, and He Ming Cheng. "Based on ANSYS Analysis of the Carbon Fiber Structure Equivalent Method with Bending Fatigue Properties." Applied Mechanics and Materials 722 (December 2014): 106–11. http://dx.doi.org/10.4028/www.scientific.net/amm.722.106.
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In the test of higher fatigue load applying to big dimension of carbon fiber plate, the shortage of just right dimension sample block, at the same time, inconvenience applying uniform load, concentrated equvalent on smaller sample block according to FEA simulation caculate is needed. How to exactly equal is the key to the problem.
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Uzan, Jacob. "A Pavement Design and Rehabilitation System." Transportation Research Record: Journal of the Transportation Research Board 1539, no. 1 (January 1996): 110–15. http://dx.doi.org/10.1177/0361198196153900115.
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Because the Superpave system is not readily available for use, an interim pavement design and rehabilitation method was developed that can be used for Israeli traffic and environmental conditions. The existing method was upgraded to include most of the relevant available information and to produce reliable pavement design for the specific conditions in Israel. The upgrading concentrated on multiple topics. An axle-load distribution specific to Israeli conditions was included because analysis indicates that axle loads in Israel are typically above the standard 80-kN single axle load. The extended California bearing ratio (CBR) method was adapted to a variety of axle-load combinations by using Miner's law for damage accumulation. Converting the axle-load distribution to the standard 80-kN equivalent single axle load leads to underdesign of approximately 10 percent in pavement thickness (or to a reduction of about 70 percent of the design life). A fatigue consideration to determine the asphalt-layer thickness was added. Local temperatures were analyzed to determine an equivalent temperature for fatigue calculation. For Israeli conditions, an equivalent temperature of 14°C can be used countrywide for asphalt-layer thicknesses up to 250 mm. An overlay design method consistent with the upgraded design procedure was assembled. It includes backcalculation of layer moduli to determine the subgrade CBR and the quality of the pavement layers; pavement condition surveys to evaluate a representative effective thickness of the asphalt layer; and component-layer analysis to determine the overlay thickness.
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Zhang, Kai, Lina Wu, and Tao Chen. "Weld Fatigue Life Analysis of Truck Mixer Sub-frame Based on Equivalent Structural Stress Method." Journal of Physics: Conference Series 2200, no. 1 (February 1, 2022): 012020. http://dx.doi.org/10.1088/1742-6596/2200/1/012020.
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Abstract In order to accurately calculate the fatigue life of the sub-frame weld of the mixer truck during the design stage, fatigue analysis of the weld is carried out by equivalent structural stress method. Through the finite element analysis of the frame, the key weld position is researched. By using the inertial release method, the stress response of the frame under the single excitation of the unit load is obtained. Combined with the basic principle of equivalent structural stress, the stress at the weld position is calculated, and the main S-N curve with a survival rate of 50% is selected to predict the fatigue life of the weld. The results show that the fatigue life of the key weld is 105.803 cycles, which fails to reach the design target value. The equivalent structural stress method has the characteristics of grid insensitivity and can better predict the fatigue life of the sub-frame weld of the mixer truck.
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TOKUYAMA, Hideki, Toru TAKAHASHI, Mitsumasa IINO, and Makoto IIDA. "Proposal of an evaluation method of equivalent fatigue load for small wind turbine blade." Transactions of the JSME (in Japanese) 80, no. 816 (2014): TEP0232. http://dx.doi.org/10.1299/transjsme.2014tep0232.
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Zhao, Dan, Yu-Xin Liu, Xun-Tao Ren, Jing-Zi Gao, Shao-Gang Liu, Li-Qiang Dong, and Ming-Shen Cheng. "Fatigue life prediction of wire rope based on grey particle filter method under small sample condition." Eksploatacja i Niezawodnosc - Maintenance and Reliability 23, no. 3 (June 1, 2021): 454–67. http://dx.doi.org/10.17531/ein.2021.3.6.
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The fatigue life prediction of wire ropes has two main characteristics: a large test sample size and uncertain factors. In this paper, based on the small number of wire rope fatigue life data, the grey particle filter method has been used to realize the fatigue life prediction of wire rope under different load conditions. First, the GOM(1,1) model is constructed and the reliability life data of wire rope is predicted under small sample size. Then, P-S-N curve of the dangerous part is determined by combining the equivalent alternating stress of the dangerous part of the wire rope during the fatigue test. Subsequently, the particle filter method is used to modify P-S-N curve. Finally, the fatigue life prediction model of wire rope is obtained based on fatigue damage accumulation, which realized the fatigue life prediction under different load conditions, and the results were compared with that from the test. The results show that the proposed method is effective and has high accuracy in wire rope fatigue life prediction under single, combined loading conditions and small sample size.
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Zheng, Wan Shan. "Research on Fatigue Load Parameters of Steel-Concrete Joint of Bridge Used for Highway Traffic and Light-Rail Traffic." Applied Mechanics and Materials 444-445 (October 2013): 122–28. http://dx.doi.org/10.4028/www.scientific.net/amm.444-445.122.
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This paper presents the calculation method for fatigue load parameters of light-rail traffic of the steel-concrete joints of Caiyuanba Yangtze River Bridge. Based on that the light-rail vehicles meet conforms to the normal distribution assumption, rain-flow counting method is adopted for the internal force amplitude of the steel-concrete joint induced by the light-rail traffic, which is then equivalent to fatigue load of constant amplitude according to linear cumulative damage criterion from Miner. With regard to design and research for similar bridges, this method can be referred to.
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Liu, X. R., and Q. Sun. "Probabilistic Properties of Fatigue Damage and an Equivalent Damage Simplification Model for Multi-Level Load Spectra." International Journal of Applied Mechanics 08, no. 02 (March 2016): 1650017. http://dx.doi.org/10.1142/s1758825116500174.
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An equivalent fatigue damage simplification model for multi-level load spectrum is proposed. On the basis of the probabilistic fatigue damage model which takes load sequence effect into account and the constant amplitude fatigue tests, probabilistic properties of damage accumulated in one loading block are achieved quantitatively by statistical methods. The new simplification model can ensure that, for the original spectrum and simplified spectrum, the probabilistic properties of fatigue damage are almost the same. Fatigue tests for Al-alloy straight plates are performed to test the validity of the model. The test results are in good agreement with predicted results.
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Wang, Penghui, Qingyi Xiang, Grzegorz Królczyk, Pengmin Lu, Binhua Wang, and Zhixiong Li. "Dynamic Modeling of a Hydraulic Excavator Stick by Introducing Multi-Case Synthesized Load Spectrum for Bench Fatigue Test." Machines 10, no. 9 (August 28, 2022): 741. http://dx.doi.org/10.3390/machines10090741.
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A multi-case load spectrum compiling method is proposed in this study for dynamic modeling of a hydraulic excavator stick to simplify and accelerate the fatigue bench test. This new method includes a simplified criterion of small-load-omitting threshold based on the principle of invariable fatigue damage, an extreme value inference criterion based on the overflow characteristics of the hydraulic system, and a synthetic extrapolation method under various working conditions. Firstly, a one-dimensional spectrum of a medium-sized excavator stick was compiled. Then, the program load spectrum for the bench fatigue test was obtained by modifying the one-dimensional spectrum based on the damage consistency criterion and the damage equivalent principle. Lastly, the fatigue tests were conducted using the program load spectrum, as well as using the random spectrum. The comparison results demonstrate that the damage location and fatigue life distribution of the stick using these two spectra are generally consistent, with a relative error smaller than 8.8%; however, the proposed program load spectrum can accelerate the test process with less time consuming than that of the random spectrum. As a result, the multi-case load spectrum is feasible and reliable for dynamic modeling of the hydraulic excavator stick in practice.
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Meneghetti, Giovanni, Alberto Campagnolo, Michael Vormwald, and Ehsan Shams. "The peak stress method applied to the fatigue assessment of tube-tube steel joints with weld ends under multiaxial loadings." MATEC Web of Conferences 300 (2019): 19001. http://dx.doi.org/10.1051/matecconf/201930019001.
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The Peak Stress Method (PSM) is an approximate, FE-oriented application of the notch stress intensity factor (NSIF) approach to fatigue design of welded joints, which is based on the singular linear elastic peak stresses calculated from FE analyses performed by using coarse mesh patterns. By adopting the averaged strain energy density (SED) as a fatigue strength criterion, a design stress (the equivalent peak stress) can be defined; in conjunction with a reference design curve previously defined, the fatigue strength assessment of welded joints subjected to multiaxial fatigue loadings can be performed. In the present contribution, the PSM has been applied to the fatigue assessment of tube-tube steel joints with weld ends, which have been fatigue tested in a previous contribution under combined loadings: namely pure axial, pure torsion and in-phase as well as out-of-phase axial-torsion loadings, all of which with two load ratios, i.e. R = 0 and R = -1. The experimental fatigue results have been re-converted in terms of equivalent peak stress by adopting a 3D FE model including an idealised weld end geometry. The equivalent peak stress has proved to assess the fatigue crack initiation location in agreement with experimental observations, moreover a quite good agreement has been obtained between the experimental results and the PSM-based design scatter band.
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Wang, Lei, Tao Shen, Chen Chen, and Huitao Chen. "Dynamic Reliability Analysis of Gear Transmission System of Wind Turbine in Consideration of Randomness of Loadings and Parameters." Mathematical Problems in Engineering 2014 (2014): 1–10. http://dx.doi.org/10.1155/2014/261767.
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A dynamic model of gear transmission system of wind turbine is built with consideration of randomness of loads and parameters. The dynamic response of the system is obtained using the theory of random sampling and the Runge-Kutta method. According to rain flow counting principle, the dynamic meshing forces are converted into a series of luffing fatigue load spectra. The amplitude and frequency of the equivalent stress are obtained using equivalent method of Geber quadratic curve. Moreover, the dynamic reliability model of components and system is built according to the theory of probability of cumulative fatigue damage. The system reliability with the random variation of parameters is calculated and the influence of random parameters on dynamic reliability of components is analyzed. In the end, the results of the proposed method are compared with that of Monte Carlo method. This paper can be instrumental in the design of wind turbine gear transmission system with more advantageous dynamic reliability.
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Yang, Liuqing, Ming Hu, Deming Zhao, Jing Yang, and Xun Zhou. "A method for assessing wheel fatigue reliability considering multiaxial stress state." Advances in Mechanical Engineering 12, no. 1 (January 2020): 168781402090234. http://dx.doi.org/10.1177/1687814020902341.
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Electric multiple unit is a modern transportation tool with high efficiency and large carrying capacity. Regarding its high speed, reliability requirement of the train is very important. As the main load bearing component of a train, the wheel is subjected to harsh working condition. Rolling contact between wheel and rail leads to wheel fatigue failure so that the fatigue reliability of wheel becomes one of the most attractive fields in electric multiple unit reliability study. This article proposed a fatigue reliability assessment method. It could obtain critical parts’ stress distribution efficiently through the force–stress relationship received by numerical simulation, so that it could assess wheel fatigue reliability under measured force–time spectrum. Also, multiaxial fatigue is considered in the method and the equivalent stress can be obtained by multiaxial model and fatigue experiment. Result of the case study shows that fatigue reliability of China Railway High-speed 5 wheel at 60,000 km mileage is 68%.
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Prawesti, Pamahayu, Bambang Suhendro, and Suryo Hapsoro. "Evaluation of rigid pavement on apron of terminal 3 Soekarno-Hatta International Airport using finite element method." MATEC Web of Conferences 270 (2019): 03005. http://dx.doi.org/10.1051/matecconf/201927003005.
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The development of transportation technology is indicated by the appearance of a new aircraft gear configuration, dual trim. The load repetitions of the movement of aircraft with dual-tridem gears, such as B-777-300ER aircraft with MTOW 28 tons, on Terminal 3 Soekarno-Hatta International Airport (SHIA) apron may cause pavement deformation, resulting in long-term fatigue and structural failures. Therefore, the performance of the existing rigid pavements to hold the loads for the next 20 years should be evaluated. Firstly, the equivalent annual departure and coverage of the aircraft in the airport up to 2037 is calculated. Next, the existing rigid pavement structure of the apron in the airport is modeled using a finite element method to calculate thermal stress and fatigue analysis for either the dowel or the slab. Our study result shows that the coverage value for the next 20 years is 86,534 with the maximum deflection of 0.055 mm and the maximum stress of 0.496834 MPa. The calculated thermal stress is 1.55 MPa, resulting in load repetition for the slab 1,241,484 and an infinite load repetition for the dowel.
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Zhou, Wei, Yitong Wu, Xiang Liu, Wei Gong, Hongjie Wang, Guofei Li, Heting Xiao, Dongrun Liu, and Aliyu Kasimu. "Multiple load recognition and fatigue assessment on longitudinal stop of railway freight car." REVIEWS ON ADVANCED MATERIALS SCIENCE 61, no. 1 (January 1, 2022): 167–85. http://dx.doi.org/10.1515/rams-2022-0024.
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Abstract Safety evaluation of key support components remains a challenge for freight trains because of the difficulties in direct and precise monitoring. In this work, the longitudinal stop on well-hole freight train, which prevents the cargo from sliding in anterior-posterior direction, is investigated. Load identification approach is proposed via strain perception at multiple locations, which are selected from the optimal positions sensitive to longitudinal and lateral loading in Finite Element Analysis (FEA). Validation is performed in random loading simulations. The identified loads deviate from the random sets within 4.07%. Longitudinal and lateral forces are recognized in an attempt to calculate the signed von Mises (SVM) stress of the longitudinal stop structure for fatigue evaluation. In application, the reconstructed structural stress climbs up to 107.1 MPa for the right weld base. Employing the rain-flow counting and Miner’s damage rule, the recommendation for load spectra grade in convergence is 64 groups. The equivalent fatigue damage is 0.854 and it drops to 30% in the statistical annual maximum mileage equivalency. Research outcome reveals that the proposed method enables the real-time monitoring of service loads and structural stress in railway freight transport, which provides scientific evidence for its maintenance planning and structural optimization.
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Xiao, W. L., H. B. Chen, and J. F. Jin. "Fatigue Life Prediction Strategies for High-Heat-Load Components." Key Engineering Materials 452-453 (November 2010): 789–92. http://dx.doi.org/10.4028/www.scientific.net/kem.452-453.789.
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High-heat-load components such as photon shutters and masks made of Glidcop Al-15 are subjected to intense thermal cycles from the X-ray beams at the third generation light sources. This paper presents thermal fatigue life prediction results of high-heat-load components at the beam line front end of Shanghai Synchrotron Radiation Facility (SSRF) under different power conditions. Used in this analysis are four typical multiaxial fatigue life prediction models, i.e. the maximum principal strain model, equivalent vonMises strain model, maximum shear strain model and critical plane approach. Detailed comparisons among them were implemented from various aspects including applicable conditions, physical meanings and resultant veracities. Critical plane approach was finally determined to be more appropriate method for dealing with multiaxial fatigue of high-heat-load components. To obtain the multiaxial stress-strain fields, nonlinear finite element analysis (FEA) was performed with commercial software ANSYS.
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Pawliczek, Roland, and Dariusz Rozumek. "The Effect of Mean Load for S355J0 Steel with Increased Strength." Metals 10, no. 2 (February 1, 2020): 209. http://dx.doi.org/10.3390/met10020209.
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The paper presents an algorithm for calculating the fatigue life of S355J0 steel specimens subjected to cyclic bending, cyclic torsion, and a combination of bending and torsion using mean stress values. The method of transforming cycle amplitudes with a non-zero mean value into fatigue equivalent cycles with increased amplitude and zero mean value was used. Commonly known and used transformation dependencies were used and a new model of the impact of the mean stress value on the fatigue life of the material was proposed. The life calculated based on the proposed algorithm was compared with the experimental life. It has been shown that the proposed model finds the widest application in the load cases studied, giving good compliance of the calculation results with the experimental results.
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Lu, Yun, Wei Jia Li, Wen Zhuo Tian, and Kai Zhou. "Study on Measurement of Six-DOF Force/Torque for Loading Experiment on Heavy Load Equipment." Applied Mechanics and Materials 543-547 (March 2014): 1115–18. http://dx.doi.org/10.4028/www.scientific.net/amm.543-547.1115.
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According to the requirements of fatigue test of aircraft cabin, large engine and mining machinery for heavy-duty six dimensional generalized force sensors, a new method of using piezoelectric quartz as force-sensitive element on the basis of the theory of heavy force division and equivalent capacity compression is proposed in this study. Furthermore, in order to minimize the force-coupling for the six-dimension force sensor, the optimization objective function is devised and the calculation method for decoupling is also proposed, on the basis of which, the generalized force sensor with high sensitivity, high stiffness, high linearity but light in its weight is designed. At last, the static calibration experiment is carried out the result shows that the sensor has a good ability of heavy force division and capacity for equivalent compression it can be well used in large tonnage six component force loading device and fatigue test system.
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Xu, Yang, Bin Zhu, Zheng Zhang, and Jiahui Chen. "Hierarchical Dynamic Bayesian Network-Based Fatigue Crack Propagation Modeling Considering Initial Defects." Sensors 22, no. 18 (September 7, 2022): 6777. http://dx.doi.org/10.3390/s22186777.
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Orthotropic steel decks (OSDs) are inevitably subjected to fatigue damage caused by cycled vehicle loads in long-span bridges. This study establishes a probabilistic analysis framework integrating the dynamic Bayesian network (DBN) and fracture mechanics to model the fatigue crack propagation considering mutual correlations among multiple fatigue details. Both the observations of fatigue crack length from field inspection and monitoring data of vehicle loads from the weight-in-motion (WIM) system are utilized. First, fracture mechanics-based uncertainty analysis is performed to determine the multiple uncertainty sources in the Paris crack propagation model, material property, and observation data of crack length. The uncertainty of monitoring data of vehicle loads is ignored because of its high accuracy; consequently, the vehicle-load-related uncertainty is spontaneously ignored, which is also demonstrated to be very small on the investigated actual bridges. Second, a hierarchical DBN model is introduced to construct mutual dependencies among various uncertainties and intra-correlations in the propagation process of multiple fatigue cracks at different components. Third, a stochastic traffic model is established based on the WIM monitoring data and multi-scale finite element analysis via substructure techniques to determine the probability distribution of vehicle-load-related parameters. After variable discretization, a refined exact inference algorithm in a forward–backward–forward manner is adopted to estimate the posterior distribution of equivalent initial crack length and update the established DBN model. Finally, the proposed method is demonstrated by a numerical case study and a typical application on an actual cable-stayed bridge with steel box girders using OSDs in China. The results show that the probability distribution of equivalent initial crack size can be spontaneously derived with a larger mean value than the results of conventional empirical analysis. Furthermore, the component-level fatigue reliability is tracked and predicted based on the established crack propagation model.
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Chen, Bin, Zheng Zhong, Xu Xie, and Pengzhen Lu. "Measurement-Based Vehicle Load Model for Urban Expressway Bridges." Mathematical Problems in Engineering 2014 (2014): 1–10. http://dx.doi.org/10.1155/2014/340896.
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Significant changes in vehicle loads have occurred in China due to the development of the automobile industry and transportation within the past two decades, particularly the rapid increase in traffic flow and the large-scale emergence of heavy trucks. However, research into vehicle loadings on urban bridges is not well developed. In this study, based on traffic flow data collected using a weigh-in-motion system installed on an expressway in an urban logistics zone, we analyzed the traffic flow, vehicle types, and gross vehicle weight (GVW) features and developed models for the vehicle load and fatigue load. According to the axle space, axle types, and axle number, the trucks in the traffic flow were classified into 10 representative vehicle types. The probability distribution of the GVW was fitted to a three-class mixed log-normal distribution. Using the improved Gumbel method, we determined the extreme value distribution of the vehicle loadings in the purpose reference period and assessed the vehicle loadings of urban bridges. In addition, using the equivalent damage theory, six equivalent vehicle models were established according to the measurements of the axle weight and axle space, thereby obtaining a simplified model of fatigue vehicle loadings on urban expressway bridges.
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Chen, Zhan-Biao, Pei-Yan Huang, Zheng-Wei Li, Xin-Yan Guo, Chen Zhao, Xiao-Hong Zheng, and Yi Yang. "Fatigue Performance of RC Beams Strengthened with CFRP under Overloads with a Ladder Spectrum." Sensors 18, no. 10 (October 3, 2018): 3321. http://dx.doi.org/10.3390/s18103321.
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Vehicle overload is detrimental to bridges and traffic safety. This paper presents a study on the fatigue performance of typical reinforced concrete (RC) beams of highway bridges under vehicle overload. A definition method of vehicle overload and a construction method of overload ladder spectrum were first proposed based on traffic data acquisition, statistical analysis and structural calculation of the highway bridges in Guangzhou. A fatigue experimental method was also proposed with the three-ladder vehicle overload spectrum, and the fatigue tests of 15 RC beams strengthened with carbon fiber reinforced polymer (CFRP) under three loading levels were then carried out. The fatigue performance and the failure mechanism of the strengthened beams were presented and discussed, and two fatigue life prediction methods were proposed with the established modified Palmgren-Miner rule and the loading level equivalent method respectively. The results showed that the fatigue performance of the strengthened RC beams was severely degraded under overload ladder spectrum compared with that under constant amplitude cyclic load, and the life prediction methods were proved effective.
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Perez-Becker, Sebastian, Francesco Papi, Joseph Saverin, David Marten, Alessandro Bianchini, and Christian Oliver Paschereit. "Is the Blade Element Momentum theory overestimating wind turbine loads? – An aeroelastic comparison between OpenFAST's AeroDyn and QBlade's Lifting-Line Free Vortex Wake method." Wind Energy Science 5, no. 2 (June 15, 2020): 721–43. http://dx.doi.org/10.5194/wes-5-721-2020.
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Abstract. Load calculations play a key role in determining the design loads of different wind turbine components. To obtain the aerodynamic loads for these calculations, the industry relies heavily on the Blade Element Momentum (BEM) theory. BEM methods use several engineering correction models to capture the aerodynamic phenomena present in Design Load Cases (DLCs) with turbulent wind. Because of this, BEM methods can overestimate aerodynamic loads under challenging conditions when compared to higher-order aerodynamic methods – such as the Lifting-Line Free Vortex Wake (LLFVW) method – leading to unnecessarily high design loads and component costs. In this paper, we give a quantitative answer to the question of load overestimation of a particular BEM implementation by comparing the results of aeroelastic load calculations done with the BEM-based OpenFAST code and the QBlade code, which uses a particular implementation of the LLFVW method. We compare extreme and fatigue load predictions from both codes using sixty-six 10 min load simulations of the Danish Technical University (DTU) 10 MW Reference Wind Turbine according to the IEC 61400-1 power production DLC group. Results from both codes show differences in fatigue and extreme load estimations for the considered sensors of the turbine. LLFVW simulations predict 9 % lower lifetime damage equivalent loads (DELs) for the out-of-plane blade root and the tower base fore–aft bending moments compared to BEM simulations. The results also show that lifetime DELs for the yaw-bearing tilt and yaw moments are 3 % and 4 % lower when calculated with the LLFVW code. An ultimate state analysis shows that extreme loads of the blade root out-of-plane bending moment predicted by the LLFVW simulations are 3 % lower than the moments predicted by BEM simulations. For the maximum tower base fore–aft bending moment, the LLFVW simulations predict an increase of 2 %. Further analysis reveals that there are two main contributors to these load differences. The first is the different way both codes treat the effect of the nonuniform wind field on the local blade aerodynamics. The second is the higher average aerodynamic torque in the LLFVW simulations. It influences the transition between operating modes of the controller and changes the aeroelastic behavior of the turbine, thus affecting the loads.
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Springer, Sebastian, Martin Leitner, Thomas Gruber, Bernd Oberwinkler, Michael Lasnik, and Florian Grün. "Fatigue Assessment of Wire and Arc Additively Manufactured Ti-6Al-4V." Metals 12, no. 5 (May 4, 2022): 795. http://dx.doi.org/10.3390/met12050795.
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Wire and arc additively manufactured (WAAM) parts and structures often present internal defects, such as gas pores, and cause irregularities in the manufacturing process. In order to describe and assess the effect of internal defects in fatigue design, this research study investigates the fatigue strength of wire arc additive manufactured structures covering the influence of imperfections, particularly gas pores. Single pass WAAM structures are manufactured using titanium alloy Ti-6Al-4V and round fatigue, tensile specimen are extracted. Tensile tests and uniaxial fatigue tests with a load stress ratio of R = 0.1 were carried out, whereby fatigue test results are used for further assessments. An extensive fractographic and metallographic fracture surface analysis is utilized to characterize and measure crack-initiating defects. As surface pores as well as bulk pores are detected, a stress intensity equivalent ΔKeqv transformation approach is presented in this study. Thereby, the defect size of the surface pore is transformed to an increased defect size, which is equivalent to a bulk pore. Subsequently, the fatigue strength assessment method by Tiryakioğlu, commonly used for casting processes, is applied. For this method, a cumulative Gumbel extreme value distribution is utilized to statistically describe the defect size. The fitted distribution with modified data reveals a better agreement with the experimental data than unmodified. Additionally, the validation of the model shows that the usage of the ΔK modified data demonstrates better results, with a slight underestimation of up to about −7%, compared to unmodified data, with an overestimation of up to about 14%, comparing the number of load cycles until failure. Hence, the presented approach applying a stress intensity equivalent transformation of surface to bulk pores facilitates a sound fatigue strength assessment of WAAM Ti-6Al-4V structures.
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Vine, John, Luther Krake, and Beau Krieg. "Helicopter Airframe Fatigue Spectra Truncation and Verification." Advanced Materials Research 891-892 (March 2014): 714–19. http://dx.doi.org/10.4028/www.scientific.net/amr.891-892.714.
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Helicopter airframe fatigue cracking is a cause of significant and growing cost of ownership and operational readiness concerns for the operators of (primarily) metallic airframe helicopters. Airframe fatigue has often had relatively low priority for helicopters, with research and design concentrated on the fatigue of flight critical rotating structural components such as rotor blades and pitch links. The Australian Defence Science and Technology Organisation (DSTO) and Naval Air Systems Command (NAVAIR) of the US Navy are collaborating to develop improved methods and technologies that can be used to assess the fatigue damage accrued by ageing helicopter airframes. The flight load sequences, or fatigue spectra, experienced by a helicopter airframe in its lifetime contain many billions of load cycles due to rotor revolutions. The application of spectra containing such vast numbers of load cycles is often impractical for reasons of test duration and cost, therefore spectra simplification techniques must be employed. To this end, truncation is a technique that is used to eliminate non-or lesser-damaging load cycles, producing spectra equivalent in terms of theoretical fatigue damage but with substantially fewer load cycles. This paper describes several truncation techniques that have recently been developed at DSTO specifically to deal with the very large numbers of load cycles that are characteristic of helicopter airframe fatigue spectra. These techniques, which include both sequence and frequency based approaches, feature tunable levels of truncation and allow for large reductions in numbers of turning points while maintaining high-fidelity and realistic fatigue spectra. Also detailed are preliminary results from a comprehensive coupon test program, which DSTO is using to experimentally verify that truncated and un-truncated spectra are approximately equivalent in terms of the fatigue damage that they produce.
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Yu, Fang, Lie Ping Ye, and Zhi Jun Dong. "A Theoretical Study on the Cables Fatigue Life Quantitative Analysis Method of Cable Bridges." Applied Mechanics and Materials 501-504 (January 2014): 1214–20. http://dx.doi.org/10.4028/www.scientific.net/amm.501-504.1214.
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Based on the theory of fatigue fracture of metals, quantitative analysis method was proposed for fatigue strength of cables of cable bridges and conclusions were reached through analysis of calculation formula: the analysis method of stress fatigue life was able to consider the section dimensions of the cables, plasticity of the material and stress ration caused by external loads and other factors which affect the fatigue life. This analysis theory was correct which took into consideration of relatively overall factors and was a better way to analyze the cable fatigue life. Meanwhile, the design of fatigue strength of bridge cables should adopt the theoretical fatigue limit represented by equivalent nominal stress amplitude as the design value of fatigue strength of cable. The theory represented by equivalent nominal stress amplitude considered the influence of stress ratio on fatigue life of cables caused by external loads. Compared with traditional method of fatigue strength estimate, with sufficient theory basis and overall consideration of factors, the results of this method were more reliable.
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Ning, Xin, Songlin Zheng, and Wenlong Xie. "Design principle of active load spectrum for shafting components in wheel hub reducer of electric vehicle." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 233, no. 10 (October 3, 2018): 2546–58. http://dx.doi.org/10.1177/0954407018800569.
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Design principle of active load spectrum is proposed for the lightweight design of shafting components. The characteristics of fatigue and the strengthening effect of low-amplitude load are conducted according to the material properties of the shafting components. The stress–life curve and three-dimensional surface of low-amplitude strengthening load are established for the life calculation of shafting components. Fast calculation method of working stress for variable size of shafting components is obtained considering the road cycle in Shanghai, the load spectrum is extrapolated, the torque working condition which is equivalent to load spectrum of 3000 km is achieved, and the fatigue damage and strengthening proportion of working stress spectrum of shafting components are adjusted, finally the minimum size of shafting components is designed to meet the requirement of service life. The design principle of active load spectrum can provide a new idea for the lightweight design of automotive components.
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Huh, Yong Hak, Philip Park, Dong Jin Kim, and Jun Hyub Park. "Effect of Biaxial Static Loads on Fatigue Crack Propagation Behavior under Cyclic Tensile and Torsional Loading." Key Engineering Materials 321-323 (October 2006): 720–23. http://dx.doi.org/10.4028/www.scientific.net/kem.321-323.720.
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Fatigue crack propagation behavior under cyclic tensile or torsional loading with biaxial static loads has been investigated. Two different biaxial loading systems, i.e. cyclic tensile loading with static torsional load and cyclic torsional loading with static tensile load, were employed to thin-walled tubular specimens. The crack propagation was measured by two crack gages mounted near the notch and crack opening level was measured by unloading compliance method. The directions of the fatigue crack propagated under respective biaxial loading conditions were examined and the growth rates were evaluated by using several cyclic parameters, including equivalent stress intensity factor range, Keff, crack tip opening displacement range, CTD, minimum strain energy density factor range, Smin. Furthermore, the growth rates were evaluated by effective cyclic parameters considering crack closure. It was found that the biaxial static stress superimposed on the cyclic tensile or torsional loading tests has no influence on the propagation directions of the cracks. Furthermore, it was shown that the fatigue crack growth rates under biaixial faigue loading were well expressed by using the cyclic fatigue parameters, Keq,eff, CTDeff, Smin,eff considering crack closure effect.
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Safronov, Oleksandr, Andrii Sulym, Pavlo Khozia, Yurii Vodiannikov, and Vladyslav Rechkalov. "PROCEDURE AND ALGORITHM FOR DETERMINING THE COEFFICIENT OF THE FREIGHT WAGON STABILITY IN COMPLIANCE WITH CURRENT REQUIREMENTS." Railbound Rolling Stock, no. 23 (December 16, 2021): 31–53. http://dx.doi.org/10.47675/2304-6309-2021-23-31-53.
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Improving the reliability of test results is achieved by applying more advanced methods of recording and processing the results. Therefore, an important part of the study of the strength of freight wagons is the choice of methods for obtaining, processing and analyzing experimental data. The article outlines the procedure and algorithms for determining the equivalent stresses under longitudinal and dynamic loads acting during operation. It is shown that algorithms for determining stresses generated by dynamic longitudinal and vertical forces are significantly different due to various load application schemes. Thus, the testing of freight wagons under dynamic longitudinal loads is carried out by the impact against an experimental wagon, and testing under dynamic vertical forces is performed during the wagon motion in the composition of the experimental train on the characteristic, pre-selected (planned) sections of the railway track at specified speeds. To estimate the level of loading of the freight wagon structureunder vertical dynamic loads, a method based on the replacement of a real random process is used by some schematized process, which in terms of the fatigue damage accumulation should be equivalent to a real process. From the whole variety of schematic methods, two methods stand out, i.e., the full cycle method and the rainflow method, which most fully represent the real process.The advantage of the rainflow method is the ability to process the process in real time. However, the algorithm of the rainflow method is quite complicated and does not allow processing large amounts of information. In this regard, a method of maximum discharge was proposed, which is a kind of full cycles method and allows you to process an unlimited amount of information online. An example specified in GOST 25.101 was used for a comparative analysis of the rainflow and maximum discharge methods. Analysis showed a satisfactory matching of both methods. Based on the procedure outlined, the block structure of the computational process is proposed to determine the equivalent reduced voltage amplitude. Each block displays the impact of the forces depending on the loading condition, that is, longitudinal impact force and dynamic forces when the wagon is moving on straight track sections, curves and switches of the railway track. Key words: wagon car, process, dynamic load, longitudinal load, voltage, amplitude, algorithm, equivalent stress, safety margin, strength.
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Oganian, E. S., S. V. Chunin, D. M. Fazliakhmetov, E. V. Muravlev, and O. A. Lobachev. "Evaluating the strength of a beam-type electric switch mechanism housing." Dependability 22, no. 4 (November 21, 2022): 3–7. http://dx.doi.org/10.21683/1729-2646-2022-22-4-3-7.
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Aim. Choice of method and its validation for the purpose of confirming the feasibility of safe operation of a switch mechanism housing submitted to rolling stock axle loads of 30 tf. Method. As of today, there are neither regulations regarding the strength parameters of load-carrying elements of electric switch mechanisms, nor verification procedures. Given the above, when evaluating the strength of electric switch mechanism housing, the authors used the method used for the purpose of evaluating the strength of load-carrying elements of locomotives per GOST R 55513-2013. That method has a long history of application as part of calculation and testing of motive power and has shown good results. According to the method, strength is evaluated by comparing the safety factor of fatigue strength n with the allowed value for steel structures [n] = 2.0. Result. The activities resulted in the validation of the proposed method of strength estimation by the criterion of fatigue strength. The value of fatigue endurance of electric switch mechanism housing was estimated based on the results of fatigue benchmark tests of three items. Each was stressed by stepping up the amplitude of the applied force after the base number of cycles had been reached. At the first stage, the loading was equivalent to the operational value. After the base number of functions had been reached for each item, the following step was initiated. The tests continued until cracks have been found. In the process of testing, the amplitude of stress was recorded at each level of loading. For the purpose of identifying the fatigue strength characteristics, the reduced fatigue strength of the switch mechanism housing was calculated under the hypothesis of linear addition of fatigue damage subject to the condition of deterministic loading and subsequent processing of the findings using statistical methods. The value of fatigue limit has been obtained for the housing of a tie-type electric switch mechanism equal to 48.4 MPa. The safety factor of fatigue strength was found to be equal to 2.86, which is above the minimal allowed value. Conclusion. It has been shown that the housing of a tie-type electric switch mechanism has a sufficient strength as regards the operational static and dynamic loads. Its safe operation when exposed to axle loads of 30 tf has also been confirmed.
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Hong, Hui, Zhenwei Cai, Weizhe Wang, and Yingzheng Liu. "An online monitoring method for creep-fatigue life consumption with real-time damage accumulation." International Journal of Damage Mechanics 30, no. 5 (January 17, 2021): 764–85. http://dx.doi.org/10.1177/1056789520954255.
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Online damage evaluation based on monitored complex cyclic loadings has become an important technique for reliability assessment, especially in high-temperature environments where creep occurs in addition to fatigue. Accuracy and rapidity of calculation are basic requirements for online damage evaluation methods. However, current creep damage evaluation methods seldom consider the fluctuation in stress, which leads to inaccuracy in life-consumption estimates. In addition, traditional cycle-counting methods are not applicable to online use. In this study, an online creep-fatigue damage evaluation method is proposed that accounts for the creep behavior that occurs under fluctuating loads. The cycle-counting method is modified from a rainflow-counting algorithm; it broadens the counting of half-cycles and adopts a new equivalent temperature in the stress-strain response calculation. The proposed method is explained in detail and demonstrated with a case study. The application of this method to a high-temperature, high-pressure pipe demonstrates its online applicability and accuracy. A time-matching algorithm is developed to display the damage evolution in real time, thus revealing the link between the incremental damage and the current load conditions, and yielding an intuitive demonstration of a given component’s state of health.
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Frydrych, Iwona, Nannan Tao, Si Chen, Liping Wang, and Wei Wu. "Tensile-tensile Fatigue Behavior of Multi-axial Warp-knitted Reinforced Composite." Fibres and Textiles in Eastern Europe 26, no. 1(127) (February 28, 2018): 73–80. http://dx.doi.org/10.5604/01.3001.0010.7800.
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An experimental study was carried out on the fatigue behaviour of multi-axial warp-knitted fabric composites. Composite samples reinforced with multi-axial warp-knitted fabric/matrix were manufactured by the vacuum-assisted resin transfer moulding method. Tensile-tensile fatigue cycling was carried out at different load levels, and S-N curves, tensile stress-strain curve and stiffness degradation of the multi-axial composite samples were obtained. Finally post-fatigue tensile tests were done at a stress level of 75%, at the stages of 1/3N and 2/3N, and the equivalent residual strength and stiffness degradation were obtained.