Optimization Mechanism of Mechanical Properties of Basalt Fiber-Epoxy Resin Composites by Interfacially Enriched Distribution of Nano-Starch Crystals

Fibre reinforced polymer composites have become a new generation of structural materials due to their unique advantages such as high specific strength,designability,good dimensional stability and ease of large-area monolithic forming.However,the problem of interfacial bonding between the resin matrix and the fibres limits the direct use of reinforcing fibres and has become a central difficulty in the development of basalt fibre-epoxy composites.This paper proposes a solution for enhancing the strength of the fibre-resin interface using maize starch nanocrystals,which are highly yield and eco-friendly.Firstly,in this paper,corn starch nanocrystals(SNC)were prepared by hydrolysis,and were deposited on the surface of basalt fibers by electrostatic adsorption.After that,in order to maximize the modification effect of nano-starch crystals on the interface,the basalt fiber-epoxy resin composite samples were prepared by mixing in a pressureless molding method.The test results shown that the addition of basalt fibers alone led to a reduction in the strength of the sample.Deposition of 0.1 wt%SNC on the surface of basalt fibers can make the strength consistent with pure epoxy resin.When the adsorption amount of SNC reached 0.5 wt%,the tensile strength of the samples was 23.7%higher than that of pure epoxy resin.This is due to the formation of ether bond homopolymers between the SNC at the fibre-epoxy interface and the epoxy resin,which distorts the originally smooth interface,leading to increased stress concentration and the development of cracks.This enhances the binding of basalt fibers.The conclusions of this paper can provide an effective,simple,low-cost and non-polluting method of interfacial enhancement modification.

Numerical Simulation on Flow Control for Drag Reduction of Revolution Body Using Dimpled Surface

Numerical simulation on the flow fields near the dimpled and the smooth revolution bodies are performed and compared by using SST k-ω turbulence model, to explain the reasons of friction and base drag reductions on the bionic dimpled surface and the control behaviors of dimpled surface to boundary layer near wall of the revolution body. The simulation results show that the dimpled surface reduces the skin friction drag through reducing the velocity gradient and turbulent intensity, and reduces the base drag through weakening the pumping action on the flow behind the revolution body caused by the external flow; the low speed rotating vortexes in the dimples segregate the external flow and the revolution body; and the low speed rotating vortexes forming in the bottom of dimples can produce negative skin friction.

Design and key parameter optimization of an agitated soybean seed metering device with horizontal seed filling

Since the low seed filling speed of mechanical seed metering devices reduces the low qualified rate of seed spacing during high-speed practices,it is significant to design agitated seed metering devices with horizontal seed filling that are suitable for high-speed practices.The combination of horizontal seed filling and agitated seed filling can accelerate the seed filling of mechanical seed metering devices,and improve the qualified rate of seed spacing during high-speed practices.In this study,theoretical analysis,discrete element method-based simulation and indoor bench test verification were conducted to investigate how key parameters of the agitated seed metering device with horizontal seed filling(angles,installation position and number of agitating plates,diameters of convex spoons)would affect the characteristics of soybean seed movement,seed number and seeding performance(qualified index,multiple index,missing seeding index)under different working speeds.Computer-based simulation,test design and regression analysis were combined to analyze the population moving rules and optimize the design parameters of seed metering devices.Based on the test scheme as designed,simulations were conducted on Fluent EDEM,and the optimal angle of the agitating plates was determined by analyzing the population migrating rules.Regression equations were established through the regression of test results,and used to find out the optimal design parameters(diameter of convex spoon,positions and number of agitating plates)of seed metering devices.Then the optimal parameter combination among different working conditions was determined that the angle,position and number of agitating plates were 30°,24.4 mm,and 13,respectively,and the diameter of convex spoon was 11.0 mm.With the optimal parameter combination and at the seeding speed of 12 km/h,the qualified index,multiple index and missing seeding index were 93.1%,2.1%and 4.8%,respectively.Under high-speed practices,the new seed metering device was not significantly different from the pneumatic seed metering device,but significantly outperformed the mechanical seed metering device.

A new braking force distribution strategy for electric vehicle based on regenerative braking strength continuity

Regenerative braking was the process of converting the kinetic energy and potential energy, which were stored in the vehicle body when vehicle braked or went downhill, into electrical energy and storing it into battery. The problem on how to distribute braking forces of front wheel and rear wheel for electric vehicles with four-wheel drive was more complex than that for electric vehicles with front-wheel drive or rear-wheel drive. In this work, the frictional braking forces distribution curve of front wheel and rear wheel is determined by optimizing the braking force distribution curve of hydraulic proportional-adjustable valve, and then the safety brake range is obtained correspondingly. A new braking force distribution strategy based on regenerative braking strength continuity is proposed to solve the braking force distribution problem for electric vehicles with four-wheel drive. Highway fuel economy test(HWFET) driving condition is used to provide the speed signals, the braking force equations of front wheel and rear wheel are expressed with linear equations. The feasibility, effectiveness, and practicality of the new braking force distribution strategy based on regenerative braking strength continuity are verified by regenerative braking strength simulation curve and braking force distribution simulation curves of front wheel and rear wheel. The proposed strategy is simple in structure, easy to be implemented and worthy being spread.

Gas-solid Erosion on Bionic Configuration Surface

A three levels orthogonal table-L9（34） was used,namely,impact angle,rotating speed,erodent size,and surface configuration were considered.The three bionic surface configurations are pit,groove,and ring.The experimental results indicate the experiment factors affecting erosive rate are,in their sequence of contribution,erodent size,impact angle,configuration,and rotating speed;the erosive rate increased with increase in rotating speed,erodent size;the erosion resistance of the sample with ring structure is higher than that of the other two samples.Based on this result,regression orthogonal experiment was carried out to select the optimal erosion resistance condition with respect to the ring bionic surface configuration.Regression equations between erosive rate and experimental factors of ring surface configurations were obtained.

Scorpion back inspiring sand-resistant surfaces

A new approach which adopted the idea of coupling bionics to improve erosion resistance was presented, by taking the desert scorpion as the research object. The anti-erosion characteristic rules and mechanism of desert scorpion＇s surface under the dynamics effect of gas/solid mixed media were researched, especially the comprehensive influence mechanism of surface morphology, microstructure, creature flexibility and many other factors was studied. Simulation by CFD software was applied to predict the relative erosion severity. Samples with the coupled bionic configurations and flexibility were produced. Experiment optimum design theory was employed to design experiment scheme. Silica sand of particle size of 105-830 ~tm was used as the erodent. The erosion tests were carried out to validate the simulation results obtained. It is shown that the predicted results are in agreement with those obtained from the experiment. And contrast tests were carried out at the best and worst test points of erosion resistance for four samples. Contrast tests show that the erosion resistance trend occurs in such order with the best erosion resistance as coupling sample, groove, smooth and flexibility, and smooth, and the increasing rate of erosion resistances in sequence of 12.08%, 8.87%, 6.03% in the best test point. But in the poorest point, the increasing rate of erosion resistance is in sequence of 15.64%, 9.53%, 6.59%. The morphologies of eroded surface were examined by the scanning electron microscope, and the possible wear mechanism was discussed.

Design and testing of planting unit for rice dry-direct-seeding planter in cold region

Rice dry-direct-seeding technology is a time-saving,cost-saving and efficient rice cultivation technique that increases the efficiency of seeding.In order to implement the specialization,light simplicity and scale of rice production,improve the level of mechanization of the whole rice production process,and solve the problems of uneven seed furrows,uneven number of seeds sown,shallow mulching and uncompact repression that occur during the promotion and application of dry-direct-seeding for rice in the cold region of northeast China.In this paper,a planting unit for rice dry-direct-seeding planter is designed.The working principles and structural parameters of the furrow opening components,the seeding apparatus and the soil covering-pressing device are described.The mechanical model of the key components of the seeding unit was established,and the forward speed,roller diameter and compacting strength were selected as the test factors.A three-factor,five-level quadratic rotation orthogonal combination test was conducted with the seed breakage rate,seeding depth qualification rate,seeding uniformity coefficient of variation and hole grain count qualification rate as the evaluation indexes.Field performance test and test results show that:at a forward speed of 4 km/h,a roller diameter of 427 mm and a compacting strength of 48.45 kPa,the seed breakage rate was 1.31%,the sowing depth qualification rate was 9.95%,the coefficient of variation of sowing uniformity was 3.75%and the number of holes was 86.75%.This accords with the agronomic requirements of dry-directseeding for rice and implements a combination of superior agronomy and modern farm machinery.

Analysis and experiment on cutting performances of high-stubble maize stalks

In the cold areas of Northeast China,maize high-stubble cutting is a novel stalk conservation tillage method,in which the maize stalks are under a unilaterally-fixed no-support cutting status.Thus,reducing the cutting resistance and power consumption of maize stalks under this status is very significant for the development of high-efficiency high-stubble cutting devices.Based on a self-designed testing system that highly restored the maize high-stubble cutting conditions and by means of experimental design and mathematic statistics,the effects of working parameters(blade angle,blade shape,cutting speed and cutting angle)on the maximum cutting resistance and power consumption were studied.By analyzing stress conditions during the stalk cutting process,six mathematic models were built to express the relationships between individual factors and the maximum cutting resistance or cutting power consumption.Through model optimization,the parameter combination for optimal cutting performance of maize stalks under unilaterally-fixed no-support cutting status was obtained:blade angle is 18°,blade shape is isosceles triangle,cutting speed is 9.5 m/s,and cutting angle is 75°.Field validation experiments under this parameter combination showed that the maximum cutting resistance was(55.23±3.50)N(declined by 11.04%),and power consumption was(11.41±1.04)J(declined by 16.65%).The research findings can be a reference for the design and development of maize high-stubble cutting devices.

Numerical simulation on drag reduction of revolution body through bionic riblet surface

Numerical simulations of flow fields on the bionic riblet and the smooth revolution bodies were performed based on the SST k-ω turbulence model in order to explain the mechanisms of the skin friction drag reduction, base drag reduction on the riblet surface, and flow control behaviors of riblet surface near the wall. The simulation results show that the riblet surface arranged on the rearward of the revolution body can reduce the skin friction drag by 8.27%, the base drag by 9.91% and the total drag by 8.59% at Ma number 0.8. The riblet surface reduces the skin friction drag by reducing the velocity gradient and turbulent intensity, and reduces the base drag by weakening the pumping action on the dead water region which behind the body of revolution caused by the external flow. The flow control behavior on boundary layer shows that the riblet surface can cut the low-speed flow near the wall effectively, and restrain the low-speed flow concentrating in span direction, thus weaken the instability of the low speed steaks produced by turbulent flow bursting.

Numerical Experiment of the Solid Particle Erosion of Bionic Configuration Blade of Centrifugal Fan

In this paper, a bionic method was presented to improve the erosion resistance of blade of the centrifugal fan. A numerical investigation of the solid particle erosion on the standard and bionic configuration blade of 4-72N_o10C centrifugal fan was presented. The numerical study employs computational fluid dynamics （CFD） software, based on a finite volume method, in which the discrete phase model was used to modele the solid particles flow, and the Eulerian conservation equation was adopt to simulate the continuous phase. Moreover, user-defined function was used to define wear equation. The various diameters of the particles were taken into account. The positions of collision of standard and bionic fan blades were discussed, and two kinds of centrifugal fan blade wear were compared. The results show that the particles from the incident source with different positions have different processes of turning and movement when enter into the impeller. The trajectories of flow in the fan channel are significantly different for the particles with different diameters. Bionic fan blade have lower erosion rate than the standard fan blade when the particle size is 20 μm. The anti-erosion mechanism of the bionic fan blade was discussed.

Design and experiment of bionic stubble breaking-deep loosening combined tillage machine

Under the conditions of straw returning operation,there are three major technical bottlenecks in the Phaeozem region of northeast China,namely low stubble breaking rate,poor tillage depth consistency,and high fuel consumption.In this research,a bionic stubble-deep loosening combined tillage machine(BSD)was designed through bionic prototype analysis,coupled bionic analysis,coupled bionic design,theoretical analysis and application of intelligent control techniques.It consists of a bionic stubble breaking device and a bionic self-excited vibratory deep loosening device.Based on the unique biting pattern of locust mouthparts on maize rootstocks,the bionic stubble breaking device adopted a new multi-segment serrated bionic structure and a symmetrical rotational motion,which could significantly increase the stubble breaking rate(p<0.05)and reduce the resistance to stubble breaking operations(p<0.05).Based on the unique biology of the hare’s paws,toes and nails,the bionic self-excited vibration deep loosening device adopted a new series-parallel composite bionic elastic system and an intelligent tilling depth control system with a fuzzy algorithm,which significantly improved the tilling depth consistency(p<0.05).The operational performance of the BSD was verified at different operating speeds through comparative experiments and reveals the mechanism of its excellent performance through theoretical analysis.The final experiment results showed that,at the same operating speed,the BSD improved the stubble breaking rate by 9.62%and 10.67%,reduced the stubble breaking torque by 28 N·m and 33 N·m,reduced the tillage depth coefficient of variation by 12.73%and 13.48%,and reduced the specific fuel consumption by 36 g/km·h and 40 g/km·h compared to the two most common models.The operating performance of the three kinds of machines will decrease with the increase of operating speed,and the BSD has the least decrease.

Review and Classification of Bio-inspired Algorithms and Their Applications

Scientists have long looked to nature and biology in order to understand and model solutions for complex real-world problems.The study of bionics bridges the functions,biological structures and functions and organizational principles found in nature with our modem technologies,numerous mathematical and metaheuristic algorithms have been developed along with the knowledge transferring process from the lifeforms to the human technologies.Output of bionics study includes not only physical products,but also various optimization computation methods that can be applied in different areas.Related algorithms can broadly be divided into four groups:evolutionary based bio-inspired algorithms,swarm intelligence-based bio-inspired algorithms,ecology-based bio-inspired algorithms and multi-objective bio-inspired algorithms.Bio-inspired algorithms such as neural network,ant colony algorithms,particle swarm optimization and others have been applied in almost every area of science,engineering and business management with a dramatic increase of number of relevant publications.This paper provides a systematic,pragmatic and comprehensive review of the latest developments in evolutionary based bio-inspired algorithms,swarm intelligence based bio-inspired algorithms,ecology based bio-inspired algorithms and multi-objective bio-inspired algorithms.

Friction wheel transmission of no-tillage corn planters

To overcome the unfavorable factors of ground wheel-driven chain transmission when a no-tillage planter operates on straw mulching fields,a friction wheel transmission based on ground wheel transmission was designed in this research.The stability,i.e.,the effects of friction wheel tyre pressure on stability of machine transmission was investigated via validation of main factors.The relationships among tyre pressure,deformation and load were determined via theoretical analysis.The tyre pressure extreme for transmission is 25.90 psi,the maximum pressure imposed on the friction wheel tyre is 14 kN,the maximum deformation of friction wheel is 8.7 mm.The stabilities of friction wheel slip rate and seeding distance were investigated via field tests and alteration of friction wheel tyre pressure.After processing the test data,it can be found that the minimum tyre pressure for acquisition of friction wheel slip rate was 24.35 psi.After processing the data of seeding distance,it can be validated that the tyre pressure was kept unchanged following the optimal transmission effect of the transmission through the abrupt change of working speed,which further proved the feasibility of the new friction wheel transmission.The transmission of friction wheel can reduce 14.67%in variation coefficient of seed spacing at the speed of 5 km/h,and 16.22%at the speed of 8 km/h.

Biomimetic earthworm dynamic soil looser for improving soybean emergence rate in cold and arid regions

In cold and arid regions,soil moisture content and accumulated temperature were seriously insufficient during spring sowing,which made it difficult for soybean seedling to emerge.Based on the principle of earthworm optimization and improvement of soil structure,this study innovatively designed a biomimetic earthworm dynamic soil looser through bionic design and theoretical calculation.By highly reducing the movement path and mode of earthworm in the soil,the mechanism could improve the soil temperature(ST)and soil moisture content(SMC),and thus greatly improve the soybean emergence rate(SER).In this study,the effects of biomimetic earthworm dynamic soil looser and its design parameters on soil temperature(ST),soil moisture content(SMC)and soybean emergence rate(SER)were investigated by two-factor test,analysis of variance(ANOVA)and Least significant Difference(LSD).Regression analysis was used to establish the mathematical model between design parameters and soybean emergence rate.MATLAB software was used to optimize the model,and the optimal design parameter combination was obtained.The contrast experiments showed that the biomimetic earthworm dynamic soil looser could construct the soil structure more suitable for the cold and arid regions.Compared with rotary blade(RB)and notched disc harrow(DH),biomimetic earthworm dynamic soil looser could increase soil moisture content by 41.30%and 27.50%,respectively.Compared with the notched disc harrow,the soil temperature could be increased by 7.97%.There was no significant difference between the effect of rotary blade on soil temperature(p>0.05).The soybean emergence rate was increased by 25.40%and 20.70%,respectively,compared with that of notched disc harrow and rotary blade.