Increase Of Speed Ratio Research Articles

Computational Fluid Dynamics (CFD) Evaluation of a Horizontal-axis Wind Turbine with a Bionic Blade

With the world's energy supply becoming increasingly scarce, wind power is gaining popularity as a clean source of renewable energy which is good for the environment. Thus, it is an alternative to burning fossil fuels such as coal, which may have an environmental impact during operations due to the emissions of unwanted gases. Wind turbines are the devices used to produce power by moving a turbine's propeller-like blades around a rotor, which spins a generator that generates energy as air passes through them. However, existing wind turbines still suffer from low conversion efficiencies. Therefore, in this current study, the bionic blade design has been used to enhance the performance of a horizontal axis wind turbine utilizing a computational simulation approach while seeking to improve its efficiency. The blade profile of the model used was based on the NACA 0012 airfoil with the modified angle of attack. The hybrid shear stress transport (SST) k-omega was used as the turbulence model. The computational procedures involved the use of various inlet velocities while maintaining a constant rotational speed. The results show that the bionic design was found to improve the overall performance of the standard NACA0012 blade design. Moreover, both power and torque coefficient outputs increase as the tip speed ratio (TSR) increases. However, the torque decreases as the TSR increases. In terms of power coefficient, the highest conversion efficiency was about 28% and it was achieved at 3.7 TSR.

Fluctuating wind load encountered by linearly moving vehicles: Investigation on fluctuating wind spectral characteristics

Wind load is one of the controlling loads for moving vehicles. Existing studies on the wind-induced response of vehicles mostly apply traditional wind spectra directly to the vehicles, overlooking their motion status. Fluctuating wind characteristics encountered by linearly moving vehicles were investigated in this paper. The traditional static frame of view was adjusted to a moving one, two principal flow directions were considered and the idea of positional equivalence introduced in Taylor frozen assumption was extended to the moving direction. A fluctuating wind power spectral density (PSD) was proposed. Then a novel test was designed to enable a measuring probe to travel across a wind field. The fluctuating wind characteristics encountered by moving points are quite different from those encountered by a static point. The integral scale decreases as the speed ratio of the measuring point to the wind increases, and an elliptic model was suggested. The proposed PSD aligns well with the test results, indicating that it can be used to accurately characterize the fluctuating wind load encountered by moving vehicles. Both the test results and the numerical analysis showed that as the speed ratio increases, the PSD and energy spectrum as a whole migrate to higher frequencies.

Analyzing the effect of elliptical vibration assistance in machining of Zr-based BMG

Bulk metallic glasses (BMGs) are known as amorphous metal alloys that have a distinct advantage compared to crystalline metal alloys due to fewer microstructural defects. Elliptical vibration-assisted machining (EVAM) is a promising technique to improve the machining performance of high-strength materials. This paper addresses a knowledge gap by investigating the chip formation mechanism in EVAM of Zr-BMG considering the shear localization due to its amorphous structure. A coupled thermo-mechanical model including the effect of vibration kinematics on Zr-BMG deformation mechanics is proposed. The effects of tool-workpiece separation, speed ratio, and strain rate on shear stress, temperature, and free volume variations due to chip segmentation are predicted and analyzed. The predicted chip formation from the developed model is validated through the comparison of chip morphology with experimental results of EVAM of Zr-BMG. The model reveals the underlying mechanism of material deformation during EVAM of Zr-BMG. According to the simulations and experimental results, the shear localization phenomena in EVAM is delayed due to insignificant changes in free volume, and enhanced heat dissipation resulted in lower temperatures in the cutting zone caused by tool-workpiece separation. Compared to traditional machining, the disparity in temperature generation and free volume diffusion in EVAM reduces as the speed ratio increases. The suppressed accumulation of periodic shear and thermal stresses at the tool tip increases the tool life in EVAM compared to the fractured tool tip in traditional machining.

Friction-mediated tuning of shear deformation and microstructure in asymmetrically rolled Mg–1Gd alloy strips

Asymmetric rolling (ASR) is distinguished from conventional symmetric rolling (SR) process as the mismatched rolling speeds of two rolls introduce additional shear deformation to the rolled strips. Friction between the rolls and strip plays an important role in the formation of shear during ASR, which further impacts the microstructures of metallic strips. In this study, finite element (FE) simulations are used to probe the effects of friction in ASR of magnesium (Mg) alloy strips with varied roll speed ratios. The results on shear deformation distributions through the thickness of the strips reveal that the increase of friction coefficient or roll speed ratio induces greater shear deformation simultaneously. It is also found that the roll speed ratio can only promote the shear formation up to a threshold value which is dictated by the friction coefficient, further increasing the mismatch of the roll speeds provides negligible improvement on the plastic deformation of the strips. Experimentally, Mg–1Gd alloy strips are processed by SR and ASR, followed by electropulse treatment (EPT) to induce static recrystallization (SRX). The predictions of the numerical models are verified via EBSD and XRD observations on the grain refinement and texture weakening in Mg–1Gd alloy, which are the direct microstructure consequences of plastic deformations during rolling. At the roll speed ratio of 1.67, the alloy shows a weakened basal texture with an average grain size of 6.0[Formula: see text][Formula: see text]m after SRX. Further increasing the roll speed ratio to 5, however, does not enhance the grain refinement or texture weakening significantly.

Effects of Gurney Flaps on the Performance of a Horizontal Axis Ocean Current Turbine

Gurney flaps can enhance the hydrodynamic efficiency of airfoils, and they are currently used in several applications, including racing cars and wind turbines. However, there is a lack of studies in the literature on the application of Gurney flaps on the Horizontal Axis Ocean Current Turbine (HAOCT). The influence of Gurney flaps on the hydrodynamic efficiency of the HAOCT is evaluated through numerical analysis. The effect of the Gurney flaps on the turbine is evaluated after the validation of the utilized numerical method is completed using the wind tunnel experimental data of the two-dimensional NACA 63415 airfoil and the water tunnel experimental data of the NACA 638xx series rotor on the clean blade. By calculating the velocity and pressure fields of the 2D airfoil by CFD, it was possible to analyze the lift improvement with the addition of the Gurney flaps by evaluating the pressure difference between the pressure surface and the negative pressure surface, and the drag improvement was due to the Gurney flaps obstructing the chordal flow of the fluid in the wake. For the 2D NACA-63415 airfoil, the drag coefficient increases with the increase in the head angle, while the lift coefficient increases and then decreases. The flap height divided by the local chord length of the Gurney flaps is 0.01, and the lift-to-drag ratio is the highest when the head angle is 4°. For the NACA-638xx turbine, the addition of Gurney flaps significantly increases the axial thrust coefficient. At lower tip speed ratios, the effect of the Gurney flaps on the rotor’s power coefficient is limited, with the greatest increase in the power coefficient at a tip speed ratio of 6 and a decrease in the power coefficient increase as the tip speed ratio increases. Increasing the height of the Gurney flaps can increase the peak power coefficient, but the power performance decreases at high tip speed ratios. The Gurney flaps distributed at the root of the rotor have less effect on the power performance. A 0.4 local radius spread of the Gurney flaps increases the peak turbine power coefficient by only 0.34%, while full-length Gurney flaps can increase the peaked blade power coefficient by 10.68%, indicating that Gurney flaps can be used to design a new HAOCT.

Recrystallization and Anisotropy of AZ31 Magnesium Alloy by Asynchronous Rolling

In this study, the microstructure and mechanical properties of AZ31 magnesium alloy were investigated through asynchronous rolling. The results demonstrate that the rolled sample exhibits a refined grain structure with a significant presence of continuous dynamic recrystallization. Notably, as the roll speed ratio increases, the grain refinement becomes more apparent. For the sample with a roll speed ratio of 1.3, the tensile strength in the rolling direction (RD) reaches 273 MPa, while the elongation measures 20.2%. Similarly, in the transverse direction (TD), the tensile strength reaches 282 MPa, accompanied by an elongation of 18.9%. These values indicate a substantial improvement in elongation compared to conventional rolling processes. The enhanced elongation can be attributed to two primary factors. Firstly, recrystallization contributes to a grain refinement recrystallization ratio of 86%, promoting improved mechanical properties. Secondly, the recrystallized grains induce a favorable Schmidt factor, further supporting elongation. Overall, the findings of this research highlight the benefits of asynchronous rolling in refining the microstructure and enhancing the mechanical properties of AZ31 magnesium alloy.

Stress Characteristics of Horizontal-Axis Wind Turbine Blades under Dynamic Yaw

The dynamic yaw significantly affects the aerodynamic load distribution of wind turbines, and the aerodynamic load is one of the main influencing factors of wind turbine structural stress variation. Taking the NACA4415 horizontal axis wind turbine designed by the research group as the research object, the numerical simulation was used to analyze the distribution characteristics of blade stress, surface thrust coefficient, and the wind turbine power output under periodic dynamic yaw conditions. The results show that the blade stress, blade axial thrust, and wind turbine output power were presented as a cosine distribution with yaw fluctuations. The distribution trend of blade stress showed an increase followed by a decrease from the inside out along the span direction. In addition, due to the influence of dynamic yaw and aerodynamic loads, the stress values near the blade root exhibited significant fluctuations. With the increase in tip speed ratio, the stress values of dynamic windward yaw gradually exceeded those of leeward yaw. Within the range of a 10° to 30° yaw variation period, the stress value with positive yaw was larger than that with negative yaw, and the highest stress value occurred in the range of −5° to 15°. The results can be provided as a theoretical basis for the structural design and yaw control strategies of wind turbines, considering dynamic yaw operation.

Induction study of a horizontal axis tidal turbine: Analytical models compared with experimental results

In a water channel, a scale horizontal axis tidal turbine is positioned in a low-disturbance uniform flow, and Particle Image Velocimetry (PIV) measurements are used to investigate turbulent-flow modifications in front of the turbine. The results confirm that even if the axial velocity deficit is mainly governed by the turbine rotational speed, a similar velocity profile is observed regardless of the rotational speed: the uniform flow evolves to a shear flow with a peak velocity deficit in front of the hub. The mean radial velocity component is not sensitive to the turbine rotational speed in front of the hub, whereas its amplitude increases near the tip of the blade as the Tip Speed Ratio increases. PIV database is also used to verify the validity of consolidated analytical induction models. Models based on the axial momentum theory, vortex method, and self-similar models exhibit some discrepancies with experimental measurements, especially in front of the hub. This paper proposes a turbine induction model that separately considers the influence of the hub and the rotating blades. The mean flow deficit in front of the operating turbine calculated using this new model is consistent with the experimental measurements.

Molecular dynamics simulation on crystal defects of single-crystal silicon during elliptical vibration cutting

In recent years, elliptical vibration cutting (EVC) has become a promising technique to fabricate high quality surface of single-crystal silicon. However, our understanding for its cutting mechanism, especially the evolution of the crystal defects in subsurface workpiece is insufficient. In this paper, molecular dynamics simulation was carried out to explore the formation mechanism of crystal defects in single-crystal silicon during EVC. A three-dimensional MD model was adopted to demonstrate the interaction between subsurface damage and tool movement in one vibration cycle. The results indicate that the formation mechanism of surface morphology including elastic recovery and side flow is greatly determined by the cutting stage in EVC. Meanwhile, the preferred slip motion during subsurface damage formation is distinct in the extrusion and shear stage. Furthermore, the influence of cutting temperature and speed on the formation of crystal defects was investigated. It is found that at elevated temperature, the proportion of the Shockley partial dislocations are apparently increased, and recrystallization process is apparently promoted on the interface of the distorted/crystal region. As the speed ratio increases, the generation and propagation of the crystal defects are suppressed, which is advantageous for suppressing the subsurface damage. These findings provide a comprehensive theoretical basis for improving the understanding in the formation mechanism of crystal defects of single-crystal silicon in EVC.

Magnetic-Mixed Convection in Nanofluid-Filled Cavity Containing Baffles and Rotating Hollow-Cylinders with Roughness Components

Mixed convective heat transfer in a nanofluid-filled lid-driven square cavity equipped with a rotating cylinder, horizontal baffles, and an external magnetic field is numerically examined in this study. A cylinder with triangular components is set at the centre of the cavity while two horizontal baffles are fixed to its vertical walls. The cavity is under the impact of the external magnetic field. Modified Maxwell’s model is taken into consideration to estimate the thermal conductivity of nanofluids. Galerkin FEM is applied to simulate nondimensional governing equations. The computations are carried out for specific ranges of physical parameters, and the results are illustrated through streamlines, isotherms, and average Nusselt number bar charts. Contours plotting indicate that flow circulation and distribution of temperature are significantly affected by the speed of a rotating rough cylinder. The fluid velocity remarkably increases with an increase in speed ratio and Reynolds number but it declines with Hartmann number, baffle length, and volume fraction. Heat transfer rate is substantially augmented by increasing the rotational speed of the rough cylinder, heights of triangular components, and suspended-nanoparticles which are also optimized for increasing baffle’s length and its horizontal arrangement. The findings of this investigation can be applied to improve the cooling efficiency of engineering equipment such as heat exchangers, energy storage systems, electronic equipment, solar collectors, and nuclear reactor safety devices.

Optimal performance of actuator disc models for horizontal-axis turbines

This study analyzes actuator disc (AD) models of horizontal-axis turbines to determine optimal performance, defined as the maximum power extracted at any tip speed ratio. We use the calculus of variations to maximize rotor torque relative to the thrust without making any assumptions about the rotor loading. The torque was obtained from the angular momentum equation and the thrust from the Kutta-Joukowsky equation which depends on the circumferential velocity and tip speed ratio. The optimality requirement is that the pitch of the vorticity exiting the rotor must be constant across the wake and equal to the ratio of torque to thrust. This result generalizes the classical finding of Betz and Goldstein that optimal lightly-loaded ADs have constant pitch. Optimizing the torque in the far-wake, well downstream of the rotor, leads to the same requirement of constant pitch. This implies that the pitch of an optimal rotor is constant everywhere in the wake at all tip speed ratios. We show that it is not possible for the pitch to reach its optimal value because of the vorticity distribution in the wake, and propose modifications to the pitch at the rotor and in the far-wake. The axial and circumferential velocities in the far-wake, which are easily determined, were used to find those at the rotor from the “disc loading equation” for the angular momentum which is also the normalized bound circulation at the rotor. For the simplest case of a lightly-loaded rotor at zero tip speed ratio, the induced circumferential velocity is linear in radius and the axial component is quadratic, As the tip speed ratio increases, the optimal power and thrust asymptote to the familiar Betz-Joukowsky values, and the induced axial velocity and rotor bound circulation become constant. At low tip speed ratios, the optimal wakes are constrained by the need to avoid breakdown of the flow at high swirl, and the conventional thrust equation, involving the axial velocity only, is inaccurate. As found in previous studies, the power coefficient increases monotonically with tip speed ratio, but the thrust coefficient reaches a maximum value slightly above the Betz-Joukowsky limit at a tip speed ratio of two, before decreasing towards the limit.

Analysis of Mechanical Parameters of Asymmetrical Rolling Dealing with Three Region Percentages in Deformation Zones.

A series of mathematical models were proposed to calculate the roll force, torque and power for cold strip asymmetrical rolling by means of the slab method, taking the percentages of the forward-slip, backward-slip and cross-shear zones into account. The friction power, plastic work and total energy consumption can be obtained by the models. The effects of variable rolling parameters—such as the speed ratio, entry thickness, friction coefficient and front and back tension—on the process of asymmetrical rolling are analyzed. In all cases, an increase in speed ratio leads to an increase in friction work and its proportions. The increase in entry thickness and deformation resistance causes both friction work and plastic deformation work to increase. The proportion of friction work decreases with increasing deformation resistance, entry thickness, front tension and back tension. In the circumstances of a thin strip being rolled with a large speed ratio, the proportion of friction work could exceed that of plastic deformation work. The concept of a threshold point of friction work was proposed to explain this phenomenon. As an example, threshold points T1, T2, T3 with the effect of the entry thickness and S1, S2, S3 with the effect of the friction coefficient have been obtained by computation. Finally, the experiment of the strip asymmetrical rolling was conducted, and a maximum error of 9.7% and an RMS error of 5.9% were found in the comparison of roll forces between experimental measurement values and calculated ones.

Aeroacoustics behavioral study of Savonius wind turbine

Vertical Axis Wind Turbines (VAWTs) are appropriate for use in populated areas. If VAWTs were installed at residential areas, the generated aerodynamic noise can be harmful in a way or another. Therefore, in the present study, the aero-acoustics of the conventional Savonius Wind turbine was investigated using Computational Fluid Dynamics (CFD). Both the Unsteady Reynolds-averaged Navier-Stokes (URANS) equations and impermeable Ffowcs Wiliams and Hawkings (FW-H) equation were simultaneously solved. The effect of speed ratio was also studied. The results indicate that; the pressure is inversely proportional to the speed ratio. Additionally, the velocity has been increased due to the increase of the tip speed ratio. Finally, it has improved that for the majority of receivers, the overall sound level increases with increasing speed ratio.

Microstructure, Texture and Mechanical Properties of Mg-6Sn Alloy Processed by Differential Speed Rolling.

The effect of shear deformation introduced by differential speed rolling (DSR) on the microstructure, texture and mechanical properties of Mg-6Sn alloy was investigated. Mg-6Sn sheets were obtained by DSR at speed ratio between upper and lower rolls of R = 1, 1.25, 2 and 3 (R = 1 refers to symmetric rolling). The microstructural and textural changes were investigated by electron backscattered diffraction (EBSD) and XRD, while the mechanical performance was evaluated based on tensile tests and calculated Lankford parameters. DSR resulted in the pronounced grain refinement of Mg-6Sn sheets and spreading of basal texture as compared to conventionally rolled one. The average grain size and basal texture intensity gradually decreased with increasing speed ratio. The basal poles splitting to transverse direction (TD) or rolling direction (RD) was observed for all Mg-6Sn sheets. For the as-rolled sheets, YS and UTS increased with increasing speed ratio, but a significant anisotropy of strength and ductility between RD and TD has been observed. After annealing at 300 °C, Mg-6Sn sheets became more homogeneous, and the elongation to failure was increased with higher speed ratios. Moreover, the annealed Mg-6Sn sheets were characterized by a very low normal anisotropy (0.91–1.16), which is normally not achieved for the most common Mg-Al-Zn alloys.

Power, efficiency, ecological function and ecological coefficient of performance optimizations of irreversible Diesel cycle based on finite piston speed

By connecting the finite time thermodynamics and the finite speed thermodynamics, an irreversible reciprocating Diesel cycle model is established with considering the irreversibilities caused by finite piston speed, heat transfer, friction, and internal irreversible loss. Through numerical calculations, the relationships among net power output (P), thermal efficiency (η), ecological function (E), ecological coefficient of performance (ECOP) and compression ratio (γ), piston speed and piston speed ratio are analyzed. As it is shown in the results, the relation curves of P−γ, η−γ, E−γ, ECOP−γcharacteristics of the cycle are parabolic ones, and those of P−ηand E−ηcharacteristics of the cycle are loop-shaped ones. When piston speed ratio is a constant, the maximum net power output increases, the maximum ecological function first increases and then decreases, the maximum thermal efficiency and the maximum ecological coefficient of performance both decrease with the increase of piston speed. When piston speed is a constant, the maximum net power output and the maximum ecological function both first increase and then decrease, and the maximum thermal efficiency and maximum ecological coefficient of performance both decrease with the increase of piston speed ratio.

Energy Performance and Radial Force of Vertical Axis Darrieus Turbine for Ocean Energy

Vertical axis Darrieus turbine is the key component for ocean energy conversion and utilization. In the present work, the energy performance, flow pattern, and radial force for a vertical axis Darrieus turbine were investigated. The experimental measurements and numerical simulations were in good agreement, which validates the accuracy and reliability of the numerical method. The results showed that the power coefficient gradually increased with the increase of tip speed ratio λ, and the power coefficient had three peaks in a revolution of runner due to three blades. The complex vortex induced by the turbine revolution mainly includes the blade tip vortex and blade surface vortex, which are related to the turbine rotation and flow separation on blade surface. The vorticity transport equation was first introduced to analyze the mechanism and evolution of vortex in a vertical axis Darrieus turbine, and the results revealed that the relative vortex elongation term is the main driving force for the formation and development of the blade surface vortex. The radial force of the Darrieus turbine gradually increases with the increase in tip speed ratio, and it is symmetrical with three humps due to three blades.

The Influence of Printing Parameters and Cell Density on Bioink Printing Outcomes.

Bioink printability persists as a limiting factor toward many bioprinting applications. Printing parameter selection is largely user-dependent, and the effect of cell density on printability has not been thoroughly investigated. Recently, methods have been developed to give greater insight into printing outcomes. This study aims to further advance those methods and apply them to study the effect of printing parameters (feedrate and flowrate) and cell density on printability. Two printed structures, a crosshatch and five-layer tube, were established as printing standards and utilized to determine the printing outcomes. Acellular bioinks were printed using a testing matrix of feedrates of 37.5, 75, 150, 300, and 600 mm/min and flowrates of 21, 42, 84, 168, and 336 mm3/min. Structures were also printed with cell densities of 5, 10, 20, and 40 × 106 cell/mL at 150 mm/min and 84 mm3/min. Only speed ratios (defined as flowrate divided by feedrate) from 0.07 to 2.24 mm2 were suitable for analysis. Increasing speed ratio dramatically increased the height, width, and wall thickness of tubular structures, but did not influence radial accuracy. For crosshatch structures, the area of pores and the frequency of broken filaments were decreased without impacting pore shape (Pr). Within speed ratios, feedrate and flowrate had negligible, inconsistent effects. Cell density did not affect any printing outcomes despite slight rheological changes. Printing outcomes were dominated by the speed ratio, with feedrate, flowrate, and cell density having little impact on printing outcomes when controlling for speed ratio within the ranges tested. The relevance of these results to other bioinks and printing conditions requires continued investigation by the bioprinting community, as well as highlight speed ratio as a key variable to report and suggest that rheology is a more sensitive measure than printing outcomes.

Developing A Machine Suitable for Alfalfa Mowing in Small Farms تطویر الة تناسب حش البرسیم فى المزارع الصغیرة.

This study was carried out to investigate a horizontal mowing knife machine (HMKM) for mowing alfalfa in small fielding's and consequently reducing mowing costs. Speed ratio of 0.86, 0.94 and 0.98; working width of 0.6, 0.8 and 1.0 m and mower knife height of 4, 6 and 8 cmwere studied. Mower efficiency, field capacity, fuel consumption, consumed energy and economic costs were computed. The main results showed that increasing speed ratio and working width result in increasing mower efficiency, field capacity, fuel consumption, economic cost but consumed energy decreased. Increasing mower knife height leads to increase mower efficiency while decreasing fuel consumption, consumed energy and economic cost. The maximum values of mower efficiency was 96.9%, field capacity of 0.66 fed/h, fuel consumption of 2.3 lit/h, machine consumed energy of 17.768 kW.h/fed, and the economic cost decreased by 54.7% at speed ratio of 0.86, working width of 0.6 m and mower knife height of 4 cm comparing to manually sickling conditions.

Analysis of asymmetrical rolling of strip considering two deformation region types

Analytical models of two deformation region types considering the percentages of three regions in the plastic deformation zone are proposed for analyzing asymmetrical rolling of strip and used to calculate the critical speed ratio, three region percentages, roll force, and roll torque. The effective range of speed ratio on thickness reduction increases with increasing critical speed ratio. When the deformation region type is backward-slip zone + cross-shear zone + forward-slip zone (B+C+F), with increasing speed ratio, the thickness reduction in asymmetrical strip rolling increases evidently, but remains unchanged when the critical speed ratio is exceeded, where the deformation region type is backward-slip zone + cross-shear zone (B+C). It is achievable to increase thickness reduction by increasing the roll force and front tension, which can not only increase the reduction rate, but also increase the critical speed ratio. The effect of asymmetrical rolling on thickness reduction is enhanced with decreasing of the roll force and front and back tension because of the increasing cross-shear zone percentage.

Enhancing the {100} grain subdivision in high-purity tantalum sheets by asymmetric cross rolling

Weak subdivision or fragmentation ability of deformed {100} (<100> // ND, normal direction) grains by traditional unidirectional (symmetric) rolling results in uneven deformation during tantalum (Ta) processing. Thus, a recently developed asymmetric cross rolling (ACR) is adopted in this work to enhance the subdivision of {100} grain in Ta sheets. Electron backscatter diffraction (EBSD), transmission electron microscopy (TEM) and Vickers hardness (HV) were used for the characterisation of microstructure in deformed {100} grains. It is shown that added shear strain component in the ACR leads to heterogeneous deformation substructures within {100} grains. The increase of speed ratio in ACR further enhances the subdivision of deformed {100} grains and thus increases the density of geometrically necessary dislocations (GNDs) in them. The computation of the largest Schmid factor (SFrolling) along with Taylor model suggests that the ACR promotes easier slip within deformed {100} grains. Therefore, the necessary total shear strain contributing to the increase of GNDs density is small. By contrast, the shear strain accumulated after CR-1.0 is distributed more evenly in each slip system resulting in rather sparse distribution of dislocation lines.