•Method of fatigue life prediction for power supporting frame is proposed.•P-S-N curve is improved considering structural parameters and the low stress.•Power supporting frame is manufactured after ...successful fatigue life prediction.
Developing electric-driven seismic vibrator is a promising way to realize green exploration. To ensure the service life of the power supporting frame under long-term operation, a method of predicting fatigue life under random load is proposed. First, stress history of the maximum stress node is obtained through dynamic analysis. Second, based on the rainflow counting method, the stress history at the maximum stress node was statistically analyzed, the distribution of amplitude and the distribution of mean are studied, and the load spectrum is compiled. Third, considering structural parameters and the stress below the fatigue limit, the P-S-N curve of the power supporting frame is achieved through two-steps corrections, and combined with the Miner’s rule, the fatigue life of the power supporting frame is predicted. The results show that under the condition of the significance level of 0.05, the amplitude and the mean of the stress are independent of each other. The amplitude of stress obeys the Weibull distribution with a shape parameter of 1.0362 and a scale parameter of 10.5108, and the mean of stress obeys a normal distribution with a mean value of 40.253 and a standard deviation of 10.1803. Under 95% reliability, considering the structural parameters and the stress below the fatigue limit, a more accurate P-S-N curve of the power supporting frame is obtained, and then with Miner’s rule the fatigue life of the power supporting frame is predicted to be 8.5 years. Based on this study, the power supporting frame was successfully manufactured. This research also provides method and case reference for structural fatigue life prediction under random loads.
Recently, many researchers have adopted the cycle-based degradation model to estimate the aging of battery energy storage system (BESS) based on the cycle information obtained from the rainflow ...counting method. However, the lack of a mathematical expression for the rainflow counting method is one of the biggest obstacles to the widespread use of the cycle-based degradation model. This paper deduces the exact analytical subgradients of the cycle-based aging cost function, which makes it possible to efficiently solve the optimal operation problem without the mathematical expression of the rainflow counting method. We introduce the subgradient projection algorithm to get the theoretical optimal operation in some special cases where the charge-discharge complementarity constraints can be relaxed. We also develop a heuristic algorithm based on the subgradient method to avoid simultaneous charging and discharging in general cases. The effectiveness of the proposed methodologies has been demonstrated with extensive numerical experiments. In the scenarios discussed in this paper, implementing the cycle-based operation rather than the energy-based operation reduces the aging cost by about 12%. When the duration of the simulation is 60 minutes, the computation time of a general-purpose solver is about 74 minutes, and the proposed algorithm only needs 21 seconds.
•The fatigue life cycles in pipelines of different building types and operating temperatures were predicted.•The stress limit values of the primary network supply and return pipeline were 650 MPa and ...759 MPa.•The stress limit values of the secondary network pipeline were calculated to be 811 MPa and 946 MPa.•Fatigue analysis of pipelines under variable frequency regulation of circulating water pumps were conducted.
The use of variable frequency control of circulating water pumps is an important energy-saving operation strategy to cope with changes in heating load. However, it can lead to low cycle fatigue failure of the pipeline when the cyclic stress generated by frequent water temperature fluctuations reaches the fatigue limit. Accurately prediction of the maximum total temperature difference cycles of pipelines is of great significance for ensuring the safe operation of centralized heating networks with frequent water flow rates regulation. Based on the actual operating data of 360,000 heat exchange stations, the stress amplitude and corresponding temperature difference cycles of pipelines at different operating temperatures were calculated, the maximum total temperature difference cycle of pipelines for 30 years was predicted. We calculated the stress limit of pipelines at different safety levels, and evaluated the impact of temperature on the fatigue life of pipelines under different building types and working conditions. The results show that the number of temperature difference cycles in primary network pipelines is three times that in secondary network pipelines, and the number of temperature difference cycles in pipelines of different building types varies greatly. The lower the operating temperature of the pipeline, the smaller the temperature difference fluctuation and the greater the contribution of pipeline fatigue damage when regulating the variable flow rate of the circulating water pump. The stress limit values of primary network supply and return water pipelines are 650 MPa and 759 MPa, while the stress limit values of secondary network supply and return water pipelines are 811 MPa and 946 MPa.
•An ANN model for predicting fatigue damage induced by wide-band non-Gaussian processes was developed and trained successfully using generated 45,000 samples.•The bandwidth parameters, S-N curve ...slope, skewness and kurtosis are used as the input neurons of the developed ANN model.•The ANN model shows an excellent agreement with the rainflow counting method.
Fatigue damage analysis is essential for ships and offshore structures subjected to various fluctuating loadings. In many realistic scenarios, structural responses that exhibit wide-band non-Gaussian characteristics are common, rendering the frequency-domain methods for fatigue damage analysis inaccurate. The rainflow counting method is widely used in the context of time-domain fatigue damage analysis; however, it entails significant computational cost. In this study, an artificial neural network (ANN) model is developed to predict the fatigue damage induced by wide-band softening and hardening non-Gaussian processes, which is based on a frequency-domain method proposed by Benasciutti and Tovo (2005b). Extensive numerical simulations are conducted based on different power spectra with a broad range of bandwidth parameters, S‒N curve slope, skewness and kurtosis. The corresponding fatigue damage is calculated using the rainflow counting method. The obtained database is used to enhance the generalizability of the ANN model. Case studies are conducted to demonstrate that the developed ANN model can give fatigue damage prediction very close to that obtained from the rainflow counting method.
The lithium-ion batteries of battery electric vehicles are generally replaced when their capacity decays below 80% of the rated capacity. In this way, a large number of retired electric vehicle ...batteries (REVB) will be produced in a short time and cause new environmental pollution if REVB are not treated properly. To address this problem, one of the major solutions is to realize the echelon utilization of REVB based on the requirements of different application scenarios. Therefore, this study investigates the economic benefits of REVB participating in different Danish electricity markets. The objective function maximizes the profit in the different markets with considering REVB life loss cost in the operational process. Rainflow counting method is employed to accurately estimate the REVB life loss cost, leading to a strong nonlinearity of the optimization problem. Afterward, simulated annealing based particle swarm optimization (SAPSO) method is used to solve the nonlinear problem and find the optimal operational strategies of the REVB. Finally, a case study with considering different situations is provided to analyze the economic benefits of applying REVB in different markets. The results reveal: 1) SAPSO method performs best in finding the optimal results compared with particle swarm optimization and simulated annealing methods, and 2) It is more likely and beneficial to invest in REVB to participate in the regulation market than the day-ahead market. This significance of the study can be summarized as: 1) Theoretically, apart from proposing a simple, cheap and eco-friendly green strategy, i.e., the echelon utilization of REVB in Danish electricity market, we advance the knowledge and call for attention about under which conditions that performing a green strategy can allow environmental-economic benefits simultaneously achievable. 2) The study provides new business opportunities for energy storage and new energy industries, and can help to realize sustainable development to improve people’s life and environmental quality.
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•Economic benefits of REVB participating in electricity markets are analyzed.•The optimal operational strategies of REVBs are proposed by using SAPSO algorithm.•A rainflow counting method is used to accurately count REVB equivalent cycle times.
This study proposes a multiaxial rainflow counting method to realize simultaneous counting of four‐channel data. The power spectral density (PSD) expressions of stresses and strains in different ...planes are derived according to multiaxial theories to address the fatigue problems under random vibration loading. This study takes the plane with maximum variance of shear strain PSD as the critical plane and proposes a hybrid frequency‐time domain life prediction method for calculating the life under random vibration loading in combination with the proposed new multiaxial rainflow counting method. Both the feasibilities of the proposed multiaxial rainflow counting method and hybrid frequency‐time domain life prediction method are verified by using the multiaxial fatigue experimental results of 6061‐T6 and 7075‐T6 aluminum alloys under random loading. Meanwhile, the calculation results and efficiencies of the proposed life prediction method are summarized, and the prediction effects of the different multiaxial fatigue models are evaluated, and different rainflow counting methods are compared.
Highlights
A novel four‐channel multiaxial rainflow counting method is proposed.
A novel hybrid frequency‐time domain life prediction method is proposed.
Validities of the proposed methods are confirmed by the fatigue life prediction cases.
Different life prediction methods and multiaxial fatigue models are evaluated.
Two compact hybrid mooring concepts adopting top synthetic fibre rope (polyester or nylon), submerged buoy and bottom chain design are studied. In addition to these two mooring concepts, another ...concept that adds two clumped weights on the bottom segment of the hybrid mooring with nylon rope is also studied. The mooring tension RAOs are obtained from seventeen regular wave tests to a point absorber moored by these three mooring configurations. Five spectral methods, including Dirlik, Tovo-Benasciutti, Zhao–Baker, Wirsching–Light and α0.75 methods are applied to study mooring fatigue damage. Five irregular wave model tests are performed, the rainflow counting method in conjunction with measured mooring tension time series is applied to calculate mooring fatigue damage, and the values are used to calibrate the spectral methods. The spectral methods are then used to evaluate the long term fatigue damage of these three moorings in the application in the west Portuguese coast. The rainflow counting method is applied to the mooring tension series generated from estimated mooring tension spectra to analysis fatigue damage, and the results are acted as the reference values for checking the accuracy of spectral methods. Then the performance of spectral methods is evaluated based on the Akaike's Information Criterion.
•Compact hybrid mooring concepts adopting top synthetic fibre rope, submerged buoy and bottom chain design are studied.•A concept that adds two clumped weights on the bottom segment of the hybrid mooring with nylon rope is also studied.•Five spectral methods, Dirlik, Tovo-Benasciutti, Zhao–Baker, Wirsching–Light and α0.75 are applied to mooring fatigue damage.•Five irregular wave model tests are performed, the rainflow counting is applied to the measured mooring tension time series.
•Spectral fatigue damage prediction of a tripod offshore wind turbine support structure is conducted.•The power spectral density of the hot spot stress is estimated.•The prediction of fatigue damage ...is evaluated in several spectral fatigue damage models.•The rainflow cycle counting method is assumed to be the “reference” data.•The model that best fits the fatigue damage is identified with the Akaike’s Information Criterion.
This work deals with the evaluation of the spectral fatigue damage prediction of a tripod offshore wind turbine support structure subjected to combined stochastic wave and wind – induced loads. The stochastic loadings are defined using the sea states based on a scatter diagram related to the North Atlantic. Further, the power spectral density of the hot spot stress is estimated accordingly. The prediction of fatigue damage is evaluated in several spectral fatigue damage models including the Rayleigh, Wirsching–Light, Tunna, α0.75, Tovo and Benasciutti, Zhao–Baker, Rice and Dirlik models. Critical hot spot locations, which experience the most fatigue damage, are analysed based on the finite element method and the S–N fatigue damage approach. The time-domain solution based on the rainflow cycle counting method is assumed to be the “real” data and the model that best fits the fatigue damage of the wind turbine support structure is identified with the Akaike’s Information Criterion.
Owing to the different structural configuration of modular steel construction (MSC) joints compared with those in conventional structural frames, the existing loading protocols might not be ...applicable to MSC joints. Suitable loading protocols for MSC joints are therefore required for use in quasi-static cyclic tests, which is the focus of the present study. A representative three-dimensional MSC building was adopted in the numerical simulation programme. Dynamic analyses were carried out using the developed numerical model under a selection of seismic waves, from which the inter-storey displacements were obtained. The rainflow counting method was employed to process the obtained displacement–time histories, and the key parameters for the loading protocol, including the total number of cycles and maximum amplitude etc. were derived accordingly. A quasi-static cyclic loading protocol dedicated to MSC joints was subsequently established. The proposed loading protocol was compared with the existing loading protocols specified in ATC-24 and in FEMA-461 through numerical simulations. The examined loading protocols were applied to two typical MSC joints, and the numerical results indicated that the proposed protocol led to a small increment in the energy consumption, ductility and bearing capacity, in comparison with the two existing loading protocols. The results show that the existing and the proposed loading protocols are all deemed suitable for use in quasi-static cyclic testing of the MSC joints, and the proposed loading protocol with 37 cycles and 0.0158 rad loading peak value could provide a new and alternative loading program for the quasi-static test of MSC joint.
