Constant Intensity Research Articles

INVESTIGATION ON HYDROLOGIC PERFORMANCE OF PERVIOUS CONCRETE PAVEMENT BY FINITE ELEMENT ANALYSIS

Pervious concrete pavement has been used widely as an effective practice for water management in low-impact development techniques. The hydrologic performance of pervious concrete pavement depends significantlyon the rainfall intensity and the designed slope. This study assessed the hydrologic performance of pervious concrete pavement by evaluating the time for surface ponding via finite element analysis. A series of simulations were carried out to explore the relationship between hydrologic performance and pervious concrete pavement by the Hydrus 2D program. The research’s results showed that as the slope increased, the time of surface ponding also increased. The data indicated that the slope variable had a low impact on the water level in pervious concrete pavement under a constant rainfall intensity. Observation of the effect of rainfall intensity showed that when the rainfall intensity increased twofold, the time for surface ponding dropped about two times. Furthermore, when surface ponding appeared, pervious concrete pavement at higher rainfall intensity had lower water content. The rainfall intensity also significantly affects the hydrologicperformance of the pervious concrete pavement. This study only assessed the hydrologic performance by using the time for surface ponding via finite element analysis. Further experimental studies should be conducted to examine the relationship of other factors to the hydrologic performance of pervious concrete pavement.

Simulation of galvanostatic charge-discharge curves of carbon-based symmetrical electrochemical supercapacitor with organic electrolyte employing potential dependent capacitance and time domain analytical expressions

Electrochemical supercapacitors differ from conventional supercapacitors mainly because they have a very high storage of electrical energy per unit of mass and a capacitance dependent on electrical potential. When studying electrical circuits in the time domain that aim to simulate the curves generated in the charging and discharging processes of electrochemical supercapacitors, as is the case with galvanostatic curves, the capacitance dependent on the electrical potential becomes a factor that considerably increases the degree of difficulty in obtaining the equations for simulating such curves. In this paper, a straightforward electrical circuit was used and fed by a source of electric current I of constant intensity in time in order to simulate the galvanostatic curve properties of a symmetrical supercapacitor evaluated by a galvanostatic cycle technique. Simulation of galvanostatic curves of these carbon-based supercapacitors with organic electrolyte also considered the effects of capacitance dependent on electric potential and the analysis was carried out in the time domain using a 2R(C + kUC(t)) electric circuit powered by a direct current source I. Analytical equations are presented and comparisons between experimental and theoretical curves were made on a quantitative basis.

Generation of a rotating high frequency magnetic field designed for use in magnetic hyperthermia

The paper presents two issues: a new method of generating a rotating magnetic field of high frequency and describes the influence of the rotating magnetic field high frequency on energy losses in a magnetic fluid. This new generation method uses a closed magnetic circuit with ferrite elements. It is powered by two high-frequency power amplifiers through transformers with ferrite cores. As a result, it is relatively easy to obtain high amplitude values ​​of the rotating magnetic field intensity. The article describes the results of the operation of rotating magnetic fields in the frequency range from 38 kHz to 370 kHz, with an amplitude of intensity up to 16 kA·m−1 on energy losses in a magnetic fluid. The obtained results indicate that at a constant frequency f the values ​​of the temperature rate increase dT/dt are proportional to the square of intensity of magnetic field ∝H2. Likewise, the values ​​of the rate of temperature increase dT/dt measured with the constant intensity of the rotating magnetic field H are proportional to the square of frequency ∝f2. It was found that in the area of ​​the low magnetic field intensity, energy losses resulting from magnetic relaxation prevail, which decrease with the increase of the field strength H, and then the share of losses due to magnetic hysteresis increases. A comparison of the calorimetric effect in a rotating and alternating magnetic field shows that the rotating field releases 75% more heat energy than the alternating field.

Metabolites in Cherry Buds to Detect Winter Dormancy.

Winter dormancy is still a “black box” in phenological models, because it evades simple observation. This study presents the first step in the identification of suitable metabolites which could indicate the timing and length of dormancy phases for the sweet cherry cultivar ‘Summit’. Global metabolite profiling detected 445 named metabolites in flower buds, which can be assigned to different substance groups such as amino acids, carbohydrates, phytohormones, lipids, nucleotides, peptides and some secondary metabolites. During the phases of endo- and ecodormancy, the energy metabolism in the form of glycolysis and the tricarboxylic acid (TCA) cycle was shut down to a minimum. However, the beginning of ontogenetic development was closely related to the up-regulation of the carbohydrate metabolism and thus to the generation of energy for the growth and development of the sweet cherry buds. From the 445 metabolites found in cherry buds, seven were selected which could be suitable markers for the ecodormancy phase, whose duration is limited by the date of endodormancy release (t1) and the beginning of ontogenetic development (t1*). With the exception of abscisic acid (ABA), which has been proven to control bud dormancy, all of these metabolites show nearly constant intensity during this phase.

Analysis on the propagation of crack in a functionally graded orthotropic strip under pre-stress

This study presents an analytical analysis on the propagation of a semi-infinite crack in a pre-stressed functionally graded orthotropic strip (FGOS) impacted by the propagation of horizontally polarized shear waves. The Wiener–Hopf technique and two-sided Fourier integral transforms have been employed in the solution treatment of the model to achieve the closed-form expression of the stress intensity factor (SIF) for the force of constant intensity (CF). The effect of crack speed, crack length, horizontal compressive pre-stress/horizontal tensile pre-stress, vertical compressive pre-stress/vertical tensile pre-stress, functional gradient parameter, and anisotropy parameter on the SIF in a pre-stressed FGOS has been unraveled through numerical computation and graphical demonstration. Furthermore, some special cases have been deduced from the derived expression of the SIF for CF. The comparative analysis has been made for the SIF in the considered strip with distinct configuration. Moreover, for the sake of validation, the obtained results for CF with constant load have been matched with the pre-established results as a special case of the problem.

A fast regularisation of a Newtonian vortex equation

We consider equations of the form u_t = \nabla \cdot ( \gamma(u) \nabla \operatorname{N}(u)) , where \operatorname{N} is the Newtonian potential (inverse of the Laplacian) posed in the whole space \mathbb{R}^d , and \gamma(u) is the mobility. For linear mobility, \gamma(u)=u , the equation and some variations have been proposed as a model for superconductivity or superfluidity. In that case the theory leads to uniqueness of bounded weak solutions having the property of compact space support, and in particular there is a special solution in the form of a disk vortex of constant intensity in space u=c_1t^{-1} supported in a ball that spreads in time like c_2t^{1/d} , thus showing a discontinuous leading front. In this paper we propose the model with sublinear mobility \gamma(u)=u^\alpha , with 0<\alpha<1 , and prove that non-negative solutions recover positivity everywhere, and moreover display a fat tail at infinity. The model acts in many ways as a regularisation of the previous one. In particular, we find that the equivalent of the previous vortex is an explicit self-similar solution decaying in time like u=O(t^{-1/\alpha}) with a space tail with size u=O(|x|^{- d/(1-\alpha)}) . We restrict the analysis to radial solutions and construct solutions by the method of characteristics. We introduce the mass function, which solves an unusual variation of Burgers’ equation, and plays an important role in the analysis. We show well-posedness in the sense of viscosity solutions. We also construct numerical finite-difference convergent schemes.

Effect of Computational Method on Accumulated O2 Deficit.

The aim of this study was to examine how relationships between exercise intensity and the rate of energy release established in different ways, affect the calculated O2 deficit accumulated during strenuous exercise. Aerobic energy release is readily measured by the O2 uptake, while anaerobic energy release is by definition independent of O2. The latter is not easily measured during strenuous exercise, but it can be estimated using the accumulated O2 deficit principle. We have calculated it using nine different approaches. Thirteen moderately trained persons (three women) volunteered to serve as subjects for cycle ergometry. Their maximal O2 uptake was 2.9 ± 0.6 mmol s−1 (x̄ ± s; 3.9 ± 0.8 LSTPD min−1). Our reference method (M0) is based on measuring the steady state O2 uptake at the end of at least ten bouts of 10 min of exercise at constant intensity, varying between 30 and 40% of that corresponding to the maximal O2 uptake and up to a power >90% of the maximal O2 uptake, which is a rather time-consuming method. The outcomes of eight different simpler approaches have been compared with those of the reference method. The main result is that the accumulated O2 deficit calculated depends a great deal on the relationship used to calculate it. A protocol of stepwise increases in exercise intensity every 4 min appeared to work well. A gross efficiency method showed the poorest performance. Another important result is that at constant power the O2 uptake continued to increase beyond 4 min of exercise at all powers examined, also at powers well-below those corresponding to the lactate threshold. Finally, the O2 uptake during loadless pedaling was considerably higher than resting O2 uptake, and it appeared to follow a cubic function of the pedaling frequency. In conclusion, to obtain reliable values of the anaerobic energy release using the accumulated O2 deficit principle, reliable relationships between exercise intensity and O2 demand must be established.

Ytterbium doped ZnO nanolaminated planar waveguide for ring resonator applications

In the present paper, optical and structural properties of Yb doped ZnO (YZO) are studied for different Yb molar concentrations. The YZO thin films are deposited over the silicon substrate via the sol-gel spin coating method. The range of Yb doping content (concentration) is 0 mol% to 1.5 mol% in ZnO. The morphological variations of the deposited thin film are studied using XRD, FE-SEM, atomic force microscopy, and Ellipsometer. The obtained results indicate that the YZO thin film possesses a single crystalline structure with (1 0 0) as the preferential orientation. All samples have a smooth, dense structure and are free of pinholes. A detailed optical result showed a favorable behavior of YZO thin film for integrated photonic devices. Hence, an optical ring resonator is simulated using MODE and FDTD tool of Lumerical to validate the experimental results. The eigen mode solver is incorporated in MODE (wavelength ranging from 300 to 800 nm) to compute refractive index, propagation constant, group velocity, losses, dispersion and transmission intensity. Furthermore, quality factor, free spectral range and fullwidth at half-maximum of the ring resonator are evaluated using FDTD.

Frequency-band down-sampled stereo-DIC: Beyond the limitation of single frequency excitation

A low-speed stereo-camera DIC setup was used in this paper to measure the down-sampled bandpass vibration signal of a plate in a given frequency range, which is much higher than the available frame rate. Down-sampled vibration measurements are well known in the literature. However, they are always subject to the strong hypothesis of having a single frequency component in the excitation source (e.g., pure sinusoidal excitation). In this scenario, several approaches can be found in the literature to reconstruct the actual response from the down-sampled data. In this paper, a data postprocessing algorithm is newly introduced to properly reconstruct the target response in the case of a frequency band excitation, thus relaxing the single frequency excitation constraint and allowing to explore a given frequency range with a single measurement. Additionally, a custom excitation signal is presented in this paper to achieve a constant intensity in the studied frequency range. The proposed approach is presented and experimentally validated by measuring a cantilever plate vibration in the kHz range using a 100 fps acquisition. A single acquisition of 98 frames allowed to describe the deformed shapes at 49 different frequency values in the range 1110–1160 Hz, highlighting two resonance peaks. The comparison with the results of multiple conventional single-frequency tests and LDV measurements confirmed the effectiveness of the proposed approach.

Reversible Mechanochromisms via Manipulating Surface Wrinkling.

Mechanochromic structural-colored materials have promising applications in various domains. In this Letter, we report three types of reversible mechanochromisms in simple material systems by harnessing mechano-responsive wrinkling dynamics including (i) brightness mechanochromism (BM), (ii) hue change mechanochromism (HCM), and (iii) viewable angle mechanochromism (VAM). Upon stretching, the BM device exhibits almost a constant hue but reduces light brightness due to the postbuckling mechanics-controlled deformation, while the HCM device can change the hue from blue to red with almost constant intensity because of the linear elastic mechanics-controlled deformation. The VAM device shows a constant hue because of the thin film interference effect. However, the viewable angles decrease with increasing applied strain owing to the light scattering of wrinkles. All of the mechanochromic behaviors exhibit good reversibility and durability. We clearly elucidated the underlying mechanisms for different mechanochromisms and demonstrated their potential applications in smart displays, stretchable strain sensors, and antipeeping/anticounterfeiting devices.

Onset of Optical Instabilities in the Nonlinear Optical Transmission of Heliconical Cholesteric Liquid Crystals

We report the result of an accurate calculation of optical transmission of a light beam traveling along the helix direction of a heliconical cholesteric liquid crystal when the light intensity is affecting the director orientation by an effective optical torque. The study is based on the application of Ambartsumian’s layer addition modified method with the aim of taking into account the continuous modification of the wave field during propagation, which is quite strong when the light wavelength approaches the Bragg resonance. We show first, that the recently calculated red shift of the transmission gap is confirmed under the constant intensity approximation. Additionally, by taking into account the full modulation of the optical field occurring at wavelengths close to the Bragg resonance, a weak red shift is already observable at very low intensities, but quickly has the onset of instabilities in the optical transmission. We give the first account of this effect, which is dependent on the light intensity showing and that it corresponds to the onset of non-uniform distribution of the conical angle and pitch of the structure.

Sensitivity enhancement of nonlinear refractive index measurement by Gaussian-Bessel beam assisted z-scan method.

Characterizing the nonlinear optical properties of numerous materials plays a prerequisite role in nonlinear imaging and quantum sensing. Here, we present the evaluation of the nonlinear optical properties of Rb vapor by the Gaussian-Bessel beam assisted z-scan method. Owed to the concentrated energy in the central waist spot and the constant intensity of the beam distribution, the Gaussian-Bessel beam enables enhanced sensitivity for nonlinear refractive index measurement. The nonlinear self-focusing and self-defocusing effects of the Rb vapor are illustrated in the case of blue and red frequency detunings from 5S1/2 - 5P3/2 transition, respectively. The complete images of the evolution of nonlinear optical properties with laser power and frequency detuning are acquired. Furthermore, the nonlinear refractive index n2 with a large scale of 10-6 cm2/W is determined from the measured transmittance peak-to-valley difference of z-scan curves, which is enhanced by a factor of ∼ 1.73 compared to the result of a equivalent Gaussian beam. Our research provides an effective method for measuring nonlinear refractive index, which will considerably enrich the application range of nonlinear material.

Soil loss and runoff obtained with customized precipitation patterns simulated by InfiAsper

Applying constant precipitation intensity, which does not occur in natural events, is one of the main limitations concerning rainfall simulators in soil erosion studies. The present work evaluated the InfiAsper rainfall simulator operating with a new control panel to program rainfalls with different precipitation intensities (PI). Infiltration rates and soil and water losses were evaluated in a Distrophic Acrisol (clay loam texture) with simulated rainfalls of 30 mm and duration of 40 min, considering advanced (AD), intermediate (IN), delayed (DE), and inverted intermediate (II) patterns, all with PI peaks of 110 mm h−1, and a constant (CT) pattern. The experimental design was in randomized blocks with five treatments (rainfall patterns) and experimental units measuring 2.5 × 2.5 m. The simulator worked satisfactorily, applying the rainfall according to the preconfigured programs. The simulated rainfall with the CT and II patterns did not promote runoff nor soil loss. Infiltration and runoff rates varied according to the applied rainfall pattern, reaching 97.8 and 27.3 mm h−1 (AD), 82.1 and 39.5 mm h−1 (IN), and 76.2 and 49.7 mm h−1 (DE), respectively. Soil loss and surface runoff totaled each 4.77 g m−2 and 3.9 mm (AD), 6.70 g m−2 and 6.8 mm (IN), and 6.03 g m−2 and 7.0 mm (DE). The InfiAsper simulator modified enables varying precipitation intensity besides obtaining satisfactory results in the field and information consistent with the expected characteristics of natural rainfall patterns. In the intermediate and delayed rainfall patterns, soil and water losses are higher than in the advanced.

Modeling the effects of topography and slope gradient of an artificially formed slope on runoff, sediment yield, water and soil loss of sandy soil

Due to frequent severe mining activities and globally destructive extreme storms, soil and water loss in open-pit coal mine dumps is extremely serious. To investigate the effect of topography on soil erosion, rainfall with a constant intensity of 1.50 mm·min−1 was conducted on topography models for 60 min. We investigated the effects of 4 topographies (straight slope, concave slope, S-shaped slope and anti-S-shaped slope) and 4 slope gradients (20°, 25°, 30° and 35°) on runoff, sediment yield, and soil and water loss. The results show that the 25° slope gradient was not conducive to infiltration, but the S-shaped slope was favorable. The runoff and sediment yield increased rapidly, then fluctuated upward in a certain range and eventually stabilized with increasing rainfall duration. With increasing slope gradient, the total runoff decreased exponentially, the total sediment yield decreased linearly, and the total amount of water and soil loss declined continuously. The initial runoff time results exhibited the order of anti-S-shaped slope > straight slope > concave slope > S-shaped slope, but the stable runoff size satisfied the S-shaped slope > straight slope > concave slope > anti-S-shaped slope. The results of the significant degree of influence of topography on sediment yield and water and soil loss exhibited the order of anti-S-shaped slope > S-shaped slope > straight slope > concave slope and S-shaped slope > straight slope > concave slope and anti-S-shaped slope. The effect of slope gradient on soil humidity and runoff was more significant than that on topography and their interaction (p < 0.001). Nevertheless, for sediment yield and water and soil loss, topography had the greatest influence (p < 0.001). Notably, the total amount of water and soil loss on the anti-S-shaped slope was relatively minimal.

Combining GOES-R and ECOSTRESS land surface temperature data to investigate diurnal variations of surface urban heat island

The surface urban heat island (SUHI) phenomenon is characterized by both high spatial and temporal variability, while its diurnal (i.e., diel) variations have rarely been investigated because traditional satellites and sensors flying on polar orbits (e.g., Landsat, MODIS) have no diurnal sampling capability. Here we combined land surface temperature (LST) data from the Geostationary Operational Environmental Satellites (GOES-R) and the Ecosystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) to explore the diurnal variations of SUHI and thermal differentiation among various land covers over the Boston Metropolitan Area. With the combined use of the LST data from GOES-R and ECOSTRESS, we took advantage of the strengths of both GOES-R (i.e., high frequency in each day and night) and ECOSTRESS (i.e., much finer spatial resolution). The SUHI intensity of the urban-core and suburban areas both exhibited clear diurnal patterns for different seasons: a continuous increase in the SUHI intensity from sunrise to noon and a decrease thereafter to sunset, followed by a relatively low and constant intensity during nighttime. The LST contrasts among different land cover types were clearly larger in the daytime than at nighttime and peaked around midday. At noon in summer, the LST of ‘Developed, High Intensity’ was 2.6 °C higher than that of ‘Developed, Medium Intensity’, and about 4.6 °C higher than that of “Developed, Open Space” and “Developed, Low Intensity”. Controlling the percent impervious surface in construction land at a relatively low level (e.g., below ~49%) could effectively alleviate the impacts of SUHI. Compared with GOES-R data, ECOSTRESS LST is suitable for monitoring the diurnal variations of intracity thermal environment at the subdistrict (or neighborhood) scale. Our study highlights the value of the combined use of geostationary satellite and ECOSTRESS LST in exploring the diurnal cycling of the SUHI, and can help inform urban planning and land-based climate mitigation policies in the context of climate change.

Analytical theory of frequency-modulated combs: generalized mean-field theory, complex cavities, and harmonic states.

Frequency-modulated (FM) combs with a linearly-chirped frequency and nearly constant intensity occur naturally in certain laser systems; they can be most succinctly described by a nonlinear Schrödinger equation with a phase potential. In this work, we perform a comprehensive analytical study of FM combs in order to calculate their salient properties. We develop a general procedure that allows mean-field theories to be constructed for arbitrary sets of master equations, and as an example consider the case of reflective defects. We derive an expression for the FM chirp of arbitrary Fabry-Perot cavities-important for most realistic lasers-and use perturbation theory to show how they are affected by finite gain bandwidth and linewidth enhancment in fast gain media. Lastly, we show that an eigenvalue formulation of the laser's dynamics can be useful for characterizing all of the stable states of the laser: the fundamental comb, the continuous-wave solution, and the harmonic states.

Effect of aluminum substitution on structural, electronic and dielectric properties of cubic CaCu3Ti4O12 ceramics: A first-principles study

The paper sheds light on the effect of Al substitution on structural, electronic and dielectric properties of cubic CaCu3Ti4O12 ceramics based on first principles method. The CaCu3Ti4-xAlxO12 (x = 0, 0.5, 1, 1.5 and 2) ceramics still keeps a cubic lattice, and the lattice constant decreases with Al concentration enhanced. Phonon dispersion curves show that the structures of CaCu3Ti4-xAlxO12 ceramics are thermodynamically stable at x ≤ 1. The CaCu3Ti4-xAlxO12 ceramics have magnetic semiconductor properties and the band gaps corresponding to the high symmetry point G increases with increasing Al concentration. It can be concluded that doping Al can increase the dielectric constant and electronic transition intensity of cubic CaCu3Ti4O12 ceramics, and reduce its energy loss. In the low energy region, the dielectric constant of CaCu3Ti3.5Al0.5O12 ceramics is about ten times that of cubic CaCu3Ti4O12 ceramics. The ratio of aluminum atoms to titanium atoms of 1:7 May be the best ratio. It can also be concluded that when A13+ replaces Ti4+ ions, A1 also acts as an electron acceptor to reduce the electron concentration of Ti4+ ions, leading to the generation of oxygen vacancies. These results will provide a theoretical basis for the design of high dielectric constant materials.

Laser-induced changes in the optical properties of the Bayfol UV1 7-2 nuclear track detector

The Bayfol UV1 7-2 is a set of polymeric solid-state nuclear track detectors with several applications in radiation detection fields. Samples from Bayfol film have been exposed to infrared pulsated laser with different fluences (10–115 J/cm2). The outcome of laser irradiation on the structural and optical properties of the Bayfol samples has been studied using X-ray diffraction and UV spectroscopy. Various optical parameters, such as the optical energy gap, Urbach energy, refractive index, optical dielectric constant, tristimulus values, chromaticity coordinates, color intercepts and color intensity, have been calculated and discussed as a function of laser fluences. The optical energy gap decreased by increasing the laser fluence up to 115 J/cm2 and an increase in the Urbach energy. This could be due to the domination of crosslinking that destroys the ordered structure. Furthermore, the non-irradiated Bayfol is nearly colorless. It displays a significant color difference by laser irradiation.

Efficient Room-Temperature Phosphorescence from Discrete Molecules Based on Thianthrene Derivatives for Oxygen Sensing and Detection

In this work, two thianthrene (TA) derivatives, 1-phenylthianthrene (TA1P) and 2-phenylthianthrene (TA2P), were synthesized with single-phenyl modification for pure organic discrete-molecule room-temperature phosphorescence (RTP). They both show the dual emission of fluorescence and RTP in amorphous polymer matrix after deoxygenation, as a result of a new mechanism of folding-induced spin-orbit coupling (SOC) enhancement. Compared with TA1P, TA2P exhibits a higher RTP efficiency and a larger spectral separation between fluorescence and RTP, which is ascribed to the substituent effect of TA at the 2-position. With decreasing oxygen concentration from 1.61% to 0%, the discrete-molecule TA2P shows an about 18-fold increase in RTP intensity and an almost constant fluorescence intensity, which can make TA2P as a self-reference ratiometric optical oxygen sensing probe at low oxygen concentrations. The oxygen quenching constant (K SV) of TA2P is estimated as high as 10.22 KPa−1 for polymethyl methacrylate (PMMA)-doped film, and even reach up to 111.86 KPa−1 for Zeonex®-doped film, which demonstrates a very high sensitivity in oxygen sensing and detection. This work provides a new idea to design pure organic discrete-molecule RTP materials with high efficiency, and TA derivatives show a potential to be applied in quantitative detection of oxygen as a new-generation optical oxygen-sensing material.

Elasto-Plastic Fatigue Crack Growth Behavior of Extruded Mg Alloy with Deformation Anisotropy Due to Stress Ratio Fluctuation.

Fatigue crack growth (FCG) experiments were performed using a low-temperature extruded magnesium alloy AZ31 with texture. Under a constant maximum stress intensity factor (Kmax), the stress ratio R was changed from 0.1 to −1 during the fatigue crack growth process, and the FCG behavior before and after the R change was investigated. As a result, tensile twins were generated owing to the fatigue load on the compression side of R = −1, and the FCG velocity was accelerated. In addition, when the maximum compressive stress at R = −1 (|(σmin)R = −1|) exceeded the compressive yield strength of the material (σcy), the FCG velocity after R fluctuation greatly accelerated. On the other hand, under the condition |(σmin)R = −1| < σcy, the degree of acceleration of the FCG velocity due to R fluctuation was small. In either case, the degree of acceleration in the FCG increased as the Kmax value increased. The above FCG acceleration mechanism due to the R fluctuation was considered based on the observation of the deformation and twinning states of the fatigue crack tip, the fatigue crack closure behavior, and the cyclic stress–strain curve of the fatigue process. The FCG acceleration mechanism was as follows: First, the driving force of the FCG increased owing to the increase in crack opening displacement due to the generation of tensile twins. Second, the coalescence of the main crack and a plurality of microcracks were generated at the twin interface. The elasto-plastic FCG behavior after the stress ratio fluctuations is defined by the effective J-integral range ΔJeff.