Variable Amplitude Research Articles

Light and Period Variations in Two K-type Contact Binaries: HI Leo and V523 Cas

We presented a low-precision spectrum for HI Leo, Transiting Exoplanet Survey Satellite data for V523 Cas, and new photometry for both K-type contact binaries. Comparing their light curves on different observing dates, we found small intrinsic variabilities, such as variable amplitudes for HI Leo and the varying heights around the second maxima for V523 Cas. By the Wilson–Devinney Code, we deduced six photometric solutions. The dark spot of V523 Cas may appear on the surface of the more massive component on BJD 2458768, while it disappears on BJD 2458779. Our results indicate that the two binaries are W-type shallow-contact binaries (f ≤ 10%). From the eclipse timing residuals, we found that the orbital periods may continuously increase, accompanied by one to two light-time effects due to additional bodies. The modulated periods and semi-amplitudes are P 3 = 25.8(±1.0) yr and A 3 = 0.ͩ0066(6) for HI Leo, P 3 = 114.8(±2.0) yr and A 3 = 0.ͩ0448(12), P 4 = 18.89(±0.14) yr and A 4 = 0.ͩ0025(2) for V523 Cas, respectively. The orbital period secularly increases at a rate of dP/dt = 2.86(±0.11) × 10−7 day yr−1 for HI Leo and dP/dt = 3.45(±0.07) × 10−8 day yr−1 for V523 Cas, which may be attributed to mass transfer from the secondary to the primary. With mass transferring, the shallow-contact binaries, HI Leo and V523 Cas, will evolve into the broken-contact configurations.

Research on fatigue reliability prediction model and structural improvement of welded drive axle housing based on master S‐N Curve method

AbstractFatigue reliability prediction of welded structures is mainly based on nominal stress or hot spot stress method, but there are some problems such as grid sensitivity and joint geometry dependence. The Master S‐N curve method can solve these problems well, but the corresponding reliability model needs to be studied. In this paper, the fatigue reliability model of welded structures based on the Master S‐N curve method is studied. Considering the randomness of life and the correlation of failure, a reliability model is proposed, which reduces the computational burden by establishing a median damage‐random threshold rule. Taking the welded drive axle housing as an object, the system reliability is analyzed under the bench test condition, and verified by the experimental data. After the verification, this method is used to predict the reliability of the axle housing under variable amplitude loading collected in the test field, and the results are verified by Monte Carlo (MC) method. When the P‐S‐N curves are parallel, the model is accurate, which is the characteristic of the Master S‐N curve method. This method only needs to input the median damage value of the weak part, which is easy to be applied. This method can speed up the reliability prediction cycle of welded structures, which is beneficial to product innovation and optimal design. Finally, an improved design scheme is proposed for the weak parts of welding, and the effects of welding leg width, welding depth, and closed weld on fatigue life are revealed.

Application of Probabilistic Approach to Investigate Influence of Details in Time History of Temperature Changes on the HCF Life of Integrated Bridge Steel Piles Installed on Water

This research estimates the high-cycle fatigue (HCF) life of integrated concrete bridge installed on water due to temperature changes. To this end, CATIA software was used to geometrically model of a real-scale bridge. Next, thermal–structural coupling analysis was performed by finite element (FE) simulation in ANSYS WORKBENCH software. The comparison technique with experimental data was used to validate the simulation. Afterward, thermal analysis was performed due to air temperature changes in different modes, including the average monthly temperature changes (large variations) as well as the maximum and minimum monthly temperature changes (small variations). The results showed that the most changes in deck length and subsequent maximum deviation in the upper part of steel piles were related to the three warm seasons in the presence of the water. Eventually, a probabilistic approach was employed to find variable amplitude fatigue lifetime of the component based on the number of annual loading blocks. To achieve the high-accuracy response, the effective parameters of the proposed probabilistic approach, including order of Fourier series and the stress range, were optimized automatically. In addition, to obtain HCF behavior of raw material, axial tension–compression fatigue tests were performed on the standard specimens fabricated from steel piles. The results revealed that considering small variations in the calculation of structural fatigue life led to a 550% reduction in life compared to structural analysis due to large variations. In addition, the obtained results were compared with the finite element results.

Correction to: An Improved Prediction Model on Fatigue Crack Growth Rate under Variable Amplitude Loads for Metallic Materials

Correction to: An Improved Prediction Model on Fatigue Crack Growth Rate under Variable Amplitude Loads for Metallic Materials

A fatigue crack growth prediction model for cracked specimen under variable amplitude loading

The objective of this study was to propose a crack growth prediction model for cracked specimens under large and variable amplitude loading conditions. In this study, the concept of change in net-section strain energy was applied to simulate elastic–plastic fracture behavior, and three-dimensional fitting of the results with respect to changes in the net-section strain energy, load ratio, and crack growth rate was performed to create the crack growth prediction model. The validity of the generated model was examined using comparisons with experimental data as well as simulation results from existing crack growth models under several variable loading conditions.

A variable amplitude fretting fatigue life estimation technique: Formulation and experimental validation

The aims of the research work summarised in this paper are twofold. The first goal is to make available a large number of new experimental results generated by testing specimens of grey cast iron under both constant and variable amplitude fretting fatigue loading. The second goal is to formulate an advanced fretting fatigue design approach based on the combined use of the Modified Wӧhler Curve Method, the Theory of Critical Distances and the Shear Stress-Maximum Variance Method. The validation exercise based on the experimental results being produced demonstrates that the proposed methodology is a powerful tool suitable for designing mechanical assemblies against fretting fatigue.

Wind-Thermal-Energy Storage System Optimization: Evidence from Simulations of the Economical Consumption of Wind Energy

To realize the economical consumption of wind energy (WE), an optimal dispatch strategy for wind-thermal-energy storage systems (WTESSs) is proposed. The scheduling model is divided into two stages. In the first stage, the strategy aims to shave peaks and fill valleys in the load curve using a time-of-use (TOU) electricity price and to reduce the variance of the net load and use the energy time-shift characteristics of energy storage systems (ESSs) to optimize their charging and discharging power. In the second stage, the strategy minimizes the cost of WTESSs, obtaining the output power of the thermal power units (TPUs) in each period. Considering the actual need for carbon reduction, a method for calculating the TPUs’ life loss cost under different variable load amplitudes is introduced, and a thermal power peaking cost model considering the ladder-type carbon trading model is constructed to calculate the cost accurately. In addition, to account for the fact that connecting all wind power outputs to the grid will significantly increase the grid peak regulation pressure and operational risk, a mathematical model for WE utilization is established to find the optimal power value for wind power grid connection in each period, which enables economical and practical WE scheduling. According to the simulation results, the overall peak-shaving cost of the system can be reduced by up to 23.95%, and the thermal power deep peak regulation cost can be reduced by up to 90.06%.

Cretaceous sequence stratigraphy of the northern Baltimore Canyon Trough: Implications for basin evolution and carbon storage

Abstract We evaluate the Cretaceous stratigraphy and carbon sequestration potential of the northern Baltimore Canyon Trough (NBCT) using >10,000 km of multi-channel seismic profiles integrated with geophysical logs, biostratigraphy, and lithology from 29 offshore wells. We identify and map six sequences resolved primarily at the stage level. Accommodation was dominated by thermal and non-thermal subsidence, though sequence boundaries correlate with regional and global sea-level changes, and the record is modified by igneous intrusion, active faulting, and changes in sediment supply and sources. Our stratigraphic maps illustrate a primary southern (central Appalachian) Early Cretaceous source that migrated northward during the Aptian and Albian. During the Cenomanian, sedimentation rates in the NBCT increased and depocenters shifted northward and landward. We show that deposition occurred in three phases: (1) earlier Cretaceous paleoenvironments were primarily terrestrial indicated by variable amplitude, chaotic seismic facies, serrated gamma logs, and heterolithic sandstones and mudstones with terrestrial microfossils; (2) the Albian to Cenomanian was dominated by deltaic paleoenvironments indicated by blocky, funnel-shaped, gamma-ray logs and clinoforms characterized by continuous high-amplitude seismic reflections with well-defined terminations; and (3) the Cenomanian and younger was marine shelf, inferred from mudstoneprone lithologies, peak gamma-ray values in well logs, and foraminiferal evidence. Long-term transgression and maximum water depths at the Cenomanian/Turonian boundary correlative with Ocean Anoxic Event 2 were followed by a regression and relative sea-level fall. We show that porous and permeable sandstones of three Aptian to Cenomanian highstand systems tracts are high-volume reservoirs for supercritical CO2 storage that are confined by overlying deep water mudstones.

Different path strategies for directed energy deposition of crossing intersections from stainless steel SS316L-Si

Additive manufacturing by directed energy deposition is of increasing interest within the scientific community. Over the past decade, this technology has gained ground with the production of parts from SS 316L-Si stainless steel, an industrial product in widespread use. Yet one of the main challenges when extending the use of this technology to the manufacture of medium complexity parts is how to achieve good intersections. This paper focuses on the use of Plasma Arc Welding (PAW) for the additive manufacturing of X-Cross intersections made of SS 316L-Si stainless steel alloy, defining its geometrical suitability and evaluating its productivity. Firstly, two strategies for the production of parts are presented: the energy control strategy on the curved path of a L-shaped wall and the variable amplitude waveform strategy (variable waving) for the continuous production of a X-cross intersection. A metallographic analysis of the samples extracted in the different tests was completed, focusing mainly on the transversal direction. Next, four deposition strategies based on discrete trajectories (cross-overlapping and cross-waving) and on continuous trajectories (waving and overlapping) are addressed in this paper for the production of cross intersections in a part of medium complexity and for the extension of its use in Near-Net-Shape (NNS) manufacturing. The mechanical properties and microstructure of samples manufactured with these deposition strategies are analysed by means of tensile tests and metallographic characterization. An analysis of the deposition energy and of the productivity is carried out for the four strategies. The productivity is analysed by means of different parameters such as the number of layers, the actual deposition rate and process times (deposition time, waiting time, standby time and idle time). The most advantageous strategies in terms of productivity were cross-waving and waving, achieving torch utilization rates relative to total time of 50 %. Methodologies and conditions for the manufacture of X-cross intersections are established. Finally, a study of the cross-intersection geometry obtained for each deposition strategy is performed. From the geometrical analysis of the crosses produced, it has been observed that the ratio of material used in the cross-overlapping sequence to produce a X-cross intersection in relation to the amount of material deposited is more than 10 % higher than in the other strategies.

Isophoric Inflating Deflating Exploration Algorithm (I-IDEA) for Equal-Amplitude Aperiodic Arrays

We present a deterministic iterative method for synthesizing equal-amplitude aperiodic array radiating patterns with arbitrary upper bounds and are capable of scanning in a wide angular range without violating the sidelobe level constraint. The approach employs the principle of “inflating” and “deflating” the sources to reduce the excitation dynamic of a starting layout iteratively. The proposed approach is flexible since it can start from a regular grid array with variable excitation amplitudes or from a nonuniform aperiodic layout generated with any other synthesis algorithm. Several numerical simulations comparing the proposed approach to some of the algorithms available in the open literature demonstrate the excellent performance of the approach.

DAMAGE EVALUATION ON STEEL MEMBERS SUBJECTED TO SEISMIC RESPONSE USING THERMOELECTRIC DEVICES WITH FREQUENCY DEPENDENCY

After the earthquake events, building damage assessment is detected by experts. However, in fact, it takes a long time to conduct the assessment process during field survey. Also, it is worried about ensuring the safety of the surveys. In recent years, structural health monitoring has been attempted. This paper suggests a damage evaluation method based on temperature measurement using thermoelectric devices. The cyclic loading tests were conducted as parameters with the loading amplitude; three types of constant amplitude, and three types of variable amplitude with gradual decrease, gradual increase, and random amplitude, totaling six types of dynamic cyclic bending. As a result of applying the damage evaluation method to the loading test, it was confirmed that the cumulative damage calculated from the temperature measurement and the cumulative damage calculated from the input displacement were almost equal. In addition, seismic response analysis was conducted using an analytical model of a four-story building, and the effectiveness of the measurement method using thermoelectric devices was examined. The results of seismic response analysis shows that the natural frequency of the primary mode of the displacement response was lower than 4Hz, and the results of the sweep loading test confirmed that the thermoelectric devices captured the waveform of the temperature up to 4Hz.

Experimental and Numerical Study of Cyclic Stress–Strain Response and Fatigue Crack Initiation Life of Mid-Carbon Steel under Constant and Multi-Step Amplitude Loading

This paper investigates the fatigue cyclic deformation behavior of mid-carbon steel. Uniaxial tensile loading tests and fatigue tests under constant and multi-step amplitude loading steps are performed to characterize the influence of loading history. The material is shown to exhibit different uniaxial ratcheting behavior depending on loading history. A smooth and gradual increase in cyclic softening is observed under smaller stress/strain conditions. Based on experimental characterization, numerical investigations are carried out to reproduce the cyclic stress–strain behavior under different variable amplitude load ranges. The nonlinear material behavior is reproduced by means of an elastoplasticity model called the Fatigue SS Model (hereafter, FSS model). The main feature of the FSS model is the ability to describe the cyclic softening behavior within a macroscopically elastic stress state. The good agreement between experimental and numerical results proves the reliability of the model to catch a realistic material response in fatigue problems. Furthermore, the present study introduces a method for the prediction of fatigue crack initiation life under variable loading conditions based on cumulative plastic work.

Performance Evaluation on the Utilization of an Established Variable Amplitude and Frequency of Vibrating Container for Potential Application in Slowing Down Sprouting in Yam

Performance Evaluation on the Utilization of an Established Variable Amplitude and Frequency of Vibrating Container for Potential Application in Slowing Down Sprouting in Yam

Robust estimation of 1/f activity improves oscillatory burst detection.

Neural oscillations often occur as transient bursts with variable amplitude and frequency dynamics. Quantifying these effects is important for understanding brain-behaviour relationships, especially in continuous datasets. To robustly measure bursts, rhythmical periods of oscillatory activity must be separated from arrhythmical background 1/f activity, which is ubiquitous in electrophysiological recordings. The Better OSCillation (BOSC) framework achieves this by defining a power threshold above the estimated background 1/f activity, combined with a duration threshold. Here we introduce a modification to this approach called fBOSC, which uses a spectral parametrisation tool to accurately model background 1/f activity in neural data. fBOSC (which is openly available as a MATLAB toolbox) is robust to power spectra with oscillatory peaks and can also model non-linear spectra. Through a series of simulations, we show that fBOSC more accurately models the 1/f power spectrum compared with existing methods. fBOSC was especially beneficial where power spectra contained a 'knee' below ~.5-10 Hz, which is typical in neural data. We also found that, unlike other methods, fBOSC was unaffected by oscillatory peaks in the neural power spectrum. Moreover, by robustly modelling background 1/f activity, the sensitivity for detecting oscillatory bursts was standardised across frequencies (e.g., theta- and alpha-bands). Finally, using openly available resting state magnetoencephalography and intracranial electrophysiology datasets, we demonstrate the application of fBOSC for oscillatory burst detection in the theta-band. These simulations and empirical analyses highlight the value of fBOSC in detecting oscillatory bursts, including in datasets that are long and continuous with no distinct experimental trials.

Hysteretic behaviour of uniaxially thermoformed auxetic foams under 3-point bending low-frequency vibration

The work describes experiments and models related to auxetic (negative Poisson’s ratio) foams subjected to low-frequency and variable amplitude 3-point bending loading. A custom 3-point bending vibration test rig is designed and used to perform the dynamic test of auxetic PU foam beams within low-frequency range (1–20 Hz) and 5 different displacement amplitudes. The auxetic foams tested in this work are manufactured using a simplified and relatively low-cost uniaxially thermoforming compression technique, which leads to the production of foams with transverse isotropic characteristics. Auxetic foam beam samples with two different cutting orientations and different thermoforming compression ratios rc (20–80%) are tested and compared, also with the use of theoretical Euler–Bernoulli-based and finite element models. The dynamic modulus of the foams increases with rc, ranging between 0.5 and 5 MPa, while the dynamic loss factor is marginally affected by the compression ratio, with overall values between 0.2 and 0.3. The auxetic PU foam has a noticeable amplitude-dependent stiffness and loss factors, while the dynamic modulus increases but slightly decreases with the frequency. The dynamic modulus is also 20–40% larger than the quasi-static one, while the dynamic and static loss factors are quite close. A modified Bouc–Wen model is also further developed to capture the amplitude and frequency-dependent properties of the conventional and auxetic foams with different volumetric compression ratios. The model shows a good agreement with the experimental results.

An efficient explicit jump high-order compact immersed interface approach for transient incompressible viscous flows

In the present work, we propose a novel hybrid explicit jump immersed interface approach in conjunction with a higher-order compact scheme for simulating transient complex flows governed by the streamfunction-vorticity (ψ-ζ) formulation of the Navier–Stokes (N–S) equations for incompressible viscous flows. A new strategy has been adopted for the jump conditions at the irregular points across the interface using Lagrangian interpolation on a Cartesian grid. This approach, which starts with the discretization of parabolic equations with discontinuities in the solutions, source terms, and the coefficients across the interface, can easily be accommodated into simulating flow past bluff bodies immersed in the flow. The superiority of the approach is reflected by the reduced magnitude and faster decay of the errors in comparison to other existing methods. It is seen to handle several fluid flow problems having practical implications in the real world very efficiently, including flows involving multiple and moving bodies. This includes the flow past a stationary circular and a twenty-four edge cactus cylinder, flows past two tandem cylinders, where in one situation both are fixed and in another, one of them is oscillating transversely with variable amplitude in time. To the best of our knowledge, the last two examples have been tackled for the first time by such an approach employing the ψ-ζ formulation in finite difference set-up. The extreme closeness of our computed solutions with the existing numerical and experimental results exemplifies the accuracy and the robustness of the proposed approach.

Multi-frequency hyperthermia characterisation via calorimetry and AC magnetometry measurements

Hyperthermia characterisation of magnetic nanoparticles (MNP) is challenging, with highly variable results reported by different laboratories and large uncertainties associated with the measured values. Here, two experimental methods for probing the heating power of MNP for magnetic field hyperthermia (MFH) therapy are compared. The first technique is calorimetry using a bespoke non-adiabatic system capable of measurements at varying frequencies and intensities of magnetic drive-field. Heat losses during calorimetry were compensated for by incorporating a loss-parameter and fitting process during analysis of the raw measurement data to calculate the sample’s specific loss power (SLP). The second technique was AC magnetometry to measure the sample hysteresis when exposed to drive-fields with variable frequencies and amplitudes. The area of the measured hysteresis loop is used to calculate the SLP. Two distinct commercial magnetic nanoparticle systems (Ferucarbotran and RCL-01) were studied using both measurement techniques at varying drive-field frequencies and intensities. Estimates of the intrinsic loss power (ILP) parameter were made based on detailed analysis of the SLP values for multiple frequencies and intensities for each nanoparticle system and experimental approach. For both nanoparticle systems, the calorimetry technique produced higher estimates of the ILP than the AC magnetometry technique. Despite these variations, the results were encouragingly similar, with all values falling within the calculated uncertainty envelopes and relative differences in the results for the two nanoparticles systems being consistent between the measurement techniques (suggesting systematic errors). Furthermore, the experimentally determined values showed strong agreement with literature. The presented study highlights the potential value of carrying out hyperthermia characterisations with differing drive-field types and measurement methods. This approach can reduce inaccuracies by assisting in identifying outliers and aiding the identification of measurements which fall within the Linear-Response Regime for the given nanoparticle. Thus, the presented approach offers additional security when characterising the ILP of MNP.

Mechanical responses of freeze–thaw treated natural stone masonry subject to compressive variable amplitude fatigue loading: Insights from stiffness loss and constitutive characterization

• The evolution of natural stone masonry stiffness exposed to multi-level cyclic load is revealed. • A novel secant modulus-based failure prediction method is proposed. • A constitutive model is proposed to characterize stone deformation under multi-level fatigue load. Stiffness loss and catastrophic failure frequently occur in natural stone masonry subject to freeze–thaw action and cyclic stress, which may incur serious engineering disasters and casualties. This work strives to experimentally unveil the mechanical responses of a medium-grained building sandstone exposed to dual effects of freeze–thaw and cyclic stress. Testing results are presented from the insights of volumetric deformation, secant modulus evolution. A drop in secant modulus of the first cycle is observed in the failure cyclic loading stage, whereas all former stages exhibit a modulus increase. This precursor well applies to all samples which is freeze–thaw and stress level independent. The development of Poisson’s ratio as well as stress level at onset of volume reversal are also presented. A theoretical modelling is put forward to characterize the axial and circumferential strains exposed to variable cyclic stress. The model shows decent effectiveness calibrated by testing results, the way to determine constants in models is introduced in detail, which can be used by readers in a broader range of construction materials.

Self‐heating measurements under cyclic loading to identify history effects on HCF properties of high‐strength low‐alloy steel: Part I—Experimental investigations

AbstractHigh cycle fatigue properties of steels are usually characterized in the as‐delivered state of the material. However, forming process, variable amplitude and accidental loading, called load history, could affect HCF properties. Given that investigating those history effect of fatigue properties by means of regular fatigue test would be very time consuming, self‐heating measurements under cyclic loading were considered. Two load history effects were studied, a macroscopic plastic pre‐strain and a cyclic pre‐loading, by means of self‐heating measurements under cyclic loading. All of the findings were used to propose a modification of a probabilistic two‐scale model, which links self‐heating measurements to HCF properties, given in the accompanying paper.

Performance Evaluation on the Utilization of an Established Variable Amplitude and Frequency of Vibrating Container for Potential Application in Slowing Down Sprouting in Yam

A variable amplitude and frequency of mechanical vibrating container working on cam and follower mechanism have been established. This study carried out a performance evaluation on the utilization of the established vibrating container for potential application in slowing down sprouting in yam. The vibrating container is electrically operated and a variable speed electric motor of 15, 000 rpm was selected for the machine. The performance parameters of the established mechanical vibrating container investigated were percentage maximum displacement and velocity of the vibration at different combined stages of amplitudes and frequencies. The percentage achievable maximum displacement of vibration measured for theoretical amplitude of cams of 5 mm, 10 mm and 20 mm were 89.40 %, 87.10 % and 72.7 % respectively for low frequency; 91.60 %, 88.40 % and 81.70 % respectively for medium frequency; and 93.20 %, 90.90 % and 86.50 % respectively for high frequency. The percentage achievable maximum velocity of vibration measured for theoretical amplitude of cams of 5 mm, 10 mm and 20 mm were 72.6 %, 71.40 % and 69.11 % respectively for low frequency; 79.81 %, 74.88 % and 70.96 % respectively for medium frequency; and 81.20 %, 77.52 % and 73.69 % respectively for high frequency. The results show that the established mechanical vibrating container has effective and suitable performances. The vibrator thus shows a good potential to effectively slow down sprouting when operated under load condition. It could help in slowing down sprouting in yams