Carbon Fiber Breakage Mechanism in Aluminum(Al)/Carbon Fibers(CFs) Composite Sheet during Accumulative Roll Bonding(ARB) Process

We put forward a method of fabricating Aluminum(Al)/carbon fibers(CFs) composite sheets by the accumulative roll bonding(ARB) method. The finished Al/CFs composite sheet has CFs and pure Al sheets as sandwich and surface layers. After cross-section observation of the Al/CFs composite sheet, we found that the CFs discretely distributed within the sandwich layer. Besides, the tensile test showed that the contribution of the sandwich CFs layer to tensile strength was less than 11% compared with annealed pure Al sheet. With ex-situ observation of the CFs breakage evolution with-16%,-32%, and-45% rolling reduction during the ARB process, the plastic instability of the Al layer was found to bring shear damages to the CFs. At last, the bridging strengthening mechanism introduced by CFs was sacrificed. We provide new insight into and instruction on Al/CFs composite sheet preparation method and processing parameters.

Formation mechanism and organizational controlling of ultra-fine-grain copper processed by asymmetrical accumulative rolling-bond and annealing

The initial copper with large grain sizes of 60-100 μm was processed by six passes asymmetrical accumulative rolling-bond （AARB） and annealing, the ultra-fine-grained （UFG） copper with grain size of 200 nm was obtained, and the microstructures and properties were studied. The results show that there are large sub-structures and also texture component C for the UFG copper obtained by six passes AARB, possessing high strength and microhardness in company with poor elongation and conductivity. Thereafter, the UFG copper was annealed at 220 °C for 35 min, in which the sub-structures disappear, the grain boundaries are composed of big angle grain boundaries, and the textures are composed of a variety of texture components and parts of twins. Compared with the UFG copper obtained by six passes AARB, the tensile strength and yield strength for the UFG copper obtained by six passes AARB and annealing at 220 °C for 35 min are decreased slightly, the elongation and conductivity are improved obviously.

Spraying Arginine at 5 Days before Harvest Delays Postharvest Broccoli Senescence via Nutrient Accumulation

To determine the effects of preharvest arginine spraying on the nutritional level of broccoli and the mechanism of action of arginine in improving the storage quality of broccoli,arginine spraying(5 mmol/L)was conducted at 0,1,3,and 5 days before harvest.The appearance,respiration rate,mass-loss rate,electrolyte leakage,glucosinolate,ascorbic acid,total phenol,total flavonoid,total sugar and sucrose contents,and sucrose phosphate synthase(SPS),invertase(INV),sucrose synthase synthesis(SSS)and cleavage(SSC)activities of broccoli samples were observed after 0,2,4,6,8,and 10 days of storage.The results showed that spraying arginine at 5 days preharvest(5-ARG)helped to inhibit broccoli respiration during storage,delay electrolyte leakage,and maintain broccoli color.Furthermore,during the growth stage,total sugar accumulation was higher in the 5-ARG group.In addition,during the storage period,sucrose synthesis was accelerated,while sucrose cleavage was inhibited,resulting in more sucrose retention in postharvest broccoli.In conclusion,5-ARG resulted in the accumulation of more nutrients during the growth process and effectively delayed the quality decline during storage,thereby prolonging the shelf life of broccoli.Therefore,this study provides a theoretical basis for improving postharvest storage characteristics of broccoli through preharvest treatments.

Effects of Cadmium Pollution in Soil on Contents and Accumulation Amounts of Nitrogen,Phosphorus, Potassium and Cadmium Elements in Potato Tubers

[Objective] This study aimed to investigate the effects of cadmium contamination in soil on contents and accumulation amounts of nitrogen, phosphorus, potassium and cadmium elements in potato tubers. [Method] Pot experiment was conducted using potato variety ‘Favorita＇ as experimental material, to determine the contents and accumulation amounts of nitrogen, phosphorus, potassium and cadmium elements in potato tubers after treatment with different concentrations of cadmium. [Result] The results showed that different concentrations of cadmium had various effects on the contents and accumulation amounts of nitrogen, phosphorus,potassium and cadmium elements in potato tubers. Nitrogen content in potato tubers was reduced under low cadmium stress and increased under moderate and high cadmium stress. Nitrogen accumulation amount in potato tubers in various cadmium treatments was significantly lower than that in control group（P0.05）; with the increase of cadmium concentration in soil, phosphorus content increased extremely significantly（P0.05）; potassium content in potato tubers in various cadmium treatments was extremely significantly higher than that in control group（P0.01）. Potassium accumulation amount in potato tubers under low cadmium stress reached the highest, which was reduced with the increasing level of cadmium contamination; both content and accumulation amount of cadmium in potato tubers had extremely significantly positive linear correlation with different cadmium concentrations in soil（P 0.01）. [Conclusion] Under cadmium-contaminated conditions, the application level of nitrogen fertilizer is reduced, and the application level of phosphorus fertilizer maintains unchanged. Under low cadmium-contaminated conditions, the application level of potassium fertilizer increases. Severely cadmium-contaminated soil is not suitable for potato cultivation.

Accumulative deformation in railway track induced by high-speed traffic loading of the trains

Prediction and control of the permanent settlement of a track caused by traffic loading from trains is crucial to high-speed railway design and maintenance. In this study, a unified prediction model of accumulative deformation of geomaterials used in railway construction subjected to cyclic loadings is introduced and calibrated using physical model testing. Based on this versatile model, a calculation approach to determine the track structure settlement under repeated loadings caused by the movement of the wheel axle of the train is proposed. Regression analysis on the physical model testing is adopted to determine the parameters involved in the computational approach. Comparison of model test data and computed results shows that the parameters obtained from the back-analysis are consistent throughout the various testing conditions, and the proposed calculation approach is capable of satisfactorily predicting the accumulative settlement of the railway roadbed and subgrade soil for various axle loads and loading cycles. A case study of a high-speed railway is performed to demonstrate the feasibility of the proposed approach in realistic engineering applications. The computation results from the settlement development of a roadbed and subgrade soil are presented and discussed.

Grain refinement and mechanical properties of pure aluminum processed by accumulative extrusion bonding

Ultrafine-grained aluminum processed by a new severe plastic deformation technique, accumulative extrusion bonding (AEB), was investigated. Microstructural characterization indicated good interfacial bonding and an average grain size of ~440 nm was obtained after six passes. Tensile testing revealed that the strength reached the maximum value of 195 MPa and the total elongation exceeded 16% after five passes. The hardness was also significantly improved and almost reached saturation after the first pass. SEM fractography of AEB-processed specimens after tensile test showed that failure mode was shear ductile fracture with elongated shallow dimples. Comparison with conventional accumulative roll bonding indicates that this new AEB technique is more effective in refining grain and improving mechanical properties of the specimens.

Enhanced mechanical properties of lamellar Cu/Al composites processed via high-temperature accumulative roll bonding

Cu/Al multilayers were produced by high-temperature accumulative roll bonding(ARB)methods up to three passes.To achieve a high bonding strength,prior to ARB processing,the Cu and Al sheets were heated to 350,400,450 and 500 ℃,respectively.The mechanical properties were evaluated by tensile tests.The microstructure was examined by optical microscopy and scanning electron microscopy equipped with energy dispersive spectrometry.The ultimate tensile stress,the grain size and the thickness of diffusion layer of lamellar composites increase with rolling temperature.When the rolling temperature is 400 ℃,the laminates show the highest ductility,but the yield stress is the lowest.As the rolling temperature further increases,both the yield stress and the ultimate tensile stress increase and the ductility decreases slightly.The mechanical properties of lamellar composites processed by low and high temperature ARB are determined by grain size and the thickness of diffusion layer,respectively.

Fabrication of ultrafine-grained AA1060 sheets via accumulative roll bonding with subsequent cryorolling

Ultrafine-grained(UFG)AA1060 sheets were fabricated via five-cycle accumulative roll bonding(ARB)and subsequent three-pass cold rolling(298 K),or cryorolling(83 K and 173 K).Microstructures of the aluminum samples were examined via transmission electron microscopy,and their mechanical properties were measured via tensile and microhardness testing.Results indicate that ultrafine grains in ARB-processed sheets were further refined by subsequent rolling,and the grain size became finer with reducing rolling temperature.The mean grain size of 666 nm in the sheets subjected to ARB was refined to 346 or 266 nm,respectively,via subsequent cold rolling or cryorolling(83 K).Subsequent cryorolling resulted in ultrafine-grained sheets of higher strength and ductility than those of the sheets subjected to cold rolling.

Strength prediction of multi-layered copper-based composites fabricated by accumulative roll bonding

This work aims to evaluate the feasibility of the fabrication of nanostructured Cu/Al/Ag multi-layered composites by accumulative roll bonding(ARB),and to analyze the tensile properties and electrical conductivity of the produced composites.A theoretical model using strengthening mechanisms and some structural parameters extracted from X-ray diffraction is also developed to predict the tensile strength of the composites.It was found that by progression of ARB,the experimental and calculated tensile strengths are enhanced,reach a maximum of about 450 and 510 MPa at the fifth cycle of ARB,respectively and then are reduced.The electrical conductivity decreased slightly by increasing the number of ARB cycles at initial ARB cycles,but the decrease was intensified at the final ARB cycles.In conclusion,the merit of ARB to fabricate this type of multi-layered nanocomposites and the accuracy of the developed model to predict tensile strength were realized.

Microstructure and mechanical properties of SiC-particle-strengthening tri-metal Al/Cu/Ni composite produced by accumulative roll bonding process

In this study, a multilayer Al/Ni/Cu composite reinforced with Si C particles was produced using an accumulative roll bonding(ARB) process with different cycles. The microstructure and mechanical properties of this composite were investigated using optical and scanning microscopy and hardness and tensile testing. The results show that by increasing the applied strain, the Al/Ni/Cu multilayer composite converted from layer features to near a particle-strengthening characteristic. After the fifth ARB cycle, a composite with a uniform distribution of reinforcements(Cu, Ni, and SiC) was fabricated. The tensile strength of the composite increased from the initial sandwich structure to the first ARB cycle and then decreased from the first to the third ARB cycle. Upon reaching five ARB cycles, the tensile strength of the composite increased again. The variation in the elongation of the composite exhibited a tendency similar to that of its tensile strength. It is observed that with increasing strain, the microhardness values of the Al, Cu, and Ni layers increased, and that the dominant fracture mechanisms of Al and Cu were dimple formation and ductile fracture. In contrast, brittle fracture in specific plains was the main characteristic of Ni fractures.

Developmental Threshold Temperature and Effective Accumulative Tem- perature of Pupae and Eggs of Holcocerus hippophaecolus

In order to understand the occurrence and the developmental regularity of seabuckthorn carpenterworm (Holcocerus hippophaecolus) and predict its population density, the developmental threshold temperature (C) and effective accumulative tem- perature (K) of the carpenterworm pupae and eggs were analyzed under the conditions of constant and variable temperatures. The results show that the values of C and K of the carpenterworm pupae are (12.1 ± 0.2) °C and (295.2 ± 4.1) day-degrees at constant temperatures, and (15.5 ± 0.4) °C and (202.4 ± 13.1) day-degrees at variable temperatures. However, the values of C and K of the eggs at variable temperatures are (16.7 ± 0.8) °C and (101.5 ± 12.6) day-degrees. The differences of developmental threshold and effective accumulative temperature under the conditions of constant and variable temperatures of the carpenterworm pupae accord with the developmental regularity of most insects in nature. By comparing five different constant temperatures, the conclusion is that the optimum developmental temperature of the pupae is 21 °C when both the pupation of the mature larvae and the eclosion of the pupae are very accordant. Moreover, the percentage of eclosion is over 90%. The average developmental durations of the carpenter- worm pupae and eggs are 31 and 16 d at variable temperatures.

Recrystallized microstructural evolution of UFG copper prepared by asymmetrical accumulative rolling-bonding process

Copper sheet with grain size of 30-60μm was processed by plastic deformation of asymmetrical accumulative rolling-bonding(AARB)with the strain of 3.2.The effects of annealing temperature and time on microstructural evolution were studied by means of electron backscattered diffraction(EBSD).EBSD grain mapping,recrystallization pole figure and grain boundary misorientation angle distribution graph were constructed,and the characteristics were assessed by microstructure,grain size,grain boundary misorientation and texture.The results show that ultra fine grains(UFG)are obtained after annealing at 250℃ for 30?40 min.When the annealing is controlled at 250℃for 40 min,the recrystallization is finished,a large number of small grains appear and most grain boundaries consist of low-angle boundaries.The character of texture is rolling texture after the recrystallization treatment,but the strength of the texture is faint.While second recrystallization happens,{110}<1ī2>+{112}<11ī> texture component disappears and turns into{122}<212>cube twin texture component.

Effect of inter-cycle heat treatment in accumulative roll-bonding(ARB)process on planar isotropy of mechanical properties of AA1050 sheets

The accumulative roll-bonding(ARB)process was applied on the strips of aluminum alloy 1050 in two processing conditions:cold ARB and warm ARB.The results of tensile tests and microhardness measurement show that the warm ARB process exhibits the lower tensile strength and microhardness,more homogeneous distribution of the microhardness,higher elongation,and especially superior planar isotropy of the tensile properties in comparison to the cold ARB,because of the intermediate heat treatment as well as the elevated temperature rolling in the warm ARB process.Furthermore,with increasing the cycles of both processes,the planar isotropy decreases progressively.

Texture evaluation in AZ31/AZ31 multilayer and AZ31/AA5068 laminar composite during accumulative roll bonding

This article presents the texture development of magnesium AZ31 alloy in the accumulative roll bonded(ARB) AZ31/AZ31 multilayer and AZ31/AA5086 laminate composite.The comparative study demonstrates that the texture evolution in AZ31 in a multilayer system is strongly influenced by the interfaces.A typical basal texture of AZ31 has been observed in AZ31/AZ31 multilayer with texture intensity increased with the rolling deformation.Presence of AZ31/AA5086 interface in the laminate composite leads to a tilted basal texture along the rolling direction(RD) in AZ31 alloy.The texture intensity of composite increased initially with rolling reduction and weakened at the higher rolling strain.Weakening of texture in AZ31 during the laminate processing at higher strain has been attributed to the development of wavy interfaces in AZ31/AA5086 laminate.

The efficacy of chemical topping in field-grown cotton is mediated by drip irrigation amount in irrigated agricultural area

Background:Cotton production in China is challenged by high labor input including manual topping(MT).Recently,to replace MT in the Xinjiang cotton region of China,mepiquat chloride(MC)was applied once more than the traditional multiple-application;this was designated as chemical topping(CT),but it is unclear whether the amount of irrigation needs to be adjusted to accommodate CT.Results:The main plots were assigned to three drip irrigation amounts[300(I_(1))480(I_(2)), and 660(I_(3))mm],and the subplots were assigned to the CT treatments[450(MC)750(MC_(2)),and 1050(MC_(3))mL·hm^(-2)25%MC]with MT as a control that was performed after early bloom.The optimum drip irrigation amount for CT was explored based on leaf photosynthesis,chlorophyll fluorescence,biomass accumulation,and yield.There were significant influe nces of drip irrigation,topping treatme nts and their interaction on chlorophyll fluorescence characteristics,gas exchange parameters and biomass accumulation characteristics as well as yield.The combination of I_(2) and MC_(2)(I_(2)MC_(2))performed best.Compared with I_(2)MC_(2)the net photosynthetic rate(Pn),stomatai conductance(Gs),transpiration rate(Tr),and photochemical quenching coefficient(qP)of I_(2)MC_(2)significantly increased by 4.0%~7.2%,6.8%〜17.1%,5.2%~17.6%,and 4.8%~9.6%,respectively,from the peak flowering to boll opening stages.Moreover,I_(2)MC_(2) showed fast reproductive organ biomass accumulation and the highest seed cotton yield;the latter was 6.6%~12.8%higher than that of I_(2)MT.Further analysis revealed that a 25%MC emulsion in water(MCEW)application resulted in yield improvement by increasing Pn,φPSⅡ,and qP to promote biomass accumulation and transport to reproductive organs.Conclusion:The results showed that the 480 mm drip irrigation combined with 750 mL·hm^(-2)MC increased the rate of dry matter accumulation in reproductive organs by increasing Pn,φPSⅡ and qP to improve photosynthetic performance,thus achieving higher yield.

Was the enclosed Qaidam Basin of The Tibetan Plateau Accumulative or Erosive during the Late Quaternary?

A geological feature in the Qaidam Basin known as the"Shell Bar"contains millions of freshwater articulated clam shells buried in-situ.Since the 1980s this feature in the now hyper-arid basin has been interpreted to be lake deposits that provide evidence for a warmer and more humid climate than present during late Marine Isotope Stage 3(MIS 3)(Bowler et al.,1986).However,the global climate during

Investigating of the Microstructure and Mechanical Properties of Al-Based Composite Reinforced with Nano-Trioxide Tungsten via Accumulative Roll Bonding Process

In the present investigation, an Al/WO3p metal matrix nanocomposite was fabricated by accumulative roll bonding (ARB) technique. Microstructural evaluation and mechanical properties of specimens were studied by Field Emission-Scanning Electron Microscopy, X-ray Diffraction, microhardness and tensile test. Several factors that affect uniform distribution of reinforcing particles were investigated. At the initial stages of ARB process particle free zones as well as particle clusters were observed in the microstructure of the composite. After 12 ARB cycles, a nanocomposite with a uniform distribution of nanoparticles was produced. It was shown that the tensile strength of the ARBed composite enhanced with the increasing number of ARB cycles. After the first cycle, a significant increase was observed in the tensile strength of nanocomposite in 2.0 percent volume of WO3p, from 89 MPa to 128 MPa (almost 1.4 times increase in strength). After the final cycle, the tensile strength value increased to 205 MPa (that is almost 2.3 times increase in strength) due to the strain hardening and grain refinement. The X-ray diffraction results showed that Al/WO3p nanocomposite with the average crystallite size of 41 nm was successfully attained after 12 cycles of the ARB process. Finally, observations revealed that the fracture mode in Al/WO3p nanocomposite was of type shearing ductile fracture with elongated shallow dimples.

THE IMPROVEMENT OF ALKALINE MEADOW BY ACCUMULATIVE SAND BY WIND IN THE SONGNEN PLAIN

In the Songnen Plain, there are 330,000 ha of alkaline meadow, many sand sources such as fixed dunes, semi-fixed dunes and sand hills, and rich wind force resources as well. Sand has been stopped naturally and A neurolepidium chinense has grown on alkaline patch of the plain. If we make use of the natural law and set up manmade obstacles in alkaline patches, we can use accumulative sand to cover alkali, improve alkaline meadow, restore A neurolepidium chinense vegetation to develop animal husbandry.

Experimental study on the accumulative effect of multiple pulses on acceleration sensor

Intentional electromagnetic interference is a serious threat to the safety of electronic devices. Multiple electromagnetic pulses will be coupled and transmitted to electronic devices through the cables.Accumulative effects are generated, which make it easier for damage to occur in the electronic devices. In this article, the working principle of micro-silicon acceleration sensors is introduced. The accumulative effects of multiple pulses on acceleration sensors is studied by a large number of injection experiments.The accumulation trends of multiple pulses with different pulse numbers and intervals are analyzed. The damaged structures inside abnormal sensor amplifiers were observed via optical microscopy and scanning electron microscopy. The experimental results show that the accumulative effect is strengthened with increased pulse number or decreased pulse interval, and the threshold voltage for multiple pulses on the acceleration sensor decreases. The threshold voltage for a single pulse is 321.57 V. When the pulse interval is 1 μs and the pulse number is 5, the threshold voltage for multiple pulses is 163.42 V,which is reduced by 49.12% compared with a single pulse. These results provide a reference for the damage design of electromagnetic pulse weapons.

Payoff-based accumulative effect promotes cooperation in spatial prisoner’s dilemma

We study the effect of accumulative payoff on the evolution of cooperation in the evolutionary prisoner＇s dilemma on a square lattice. We introduce a decaying factor for the accumulative payoff, which characterizes the extent that the historical payoff is accumulated. It is shown that for fixed values of the temptation to defect, the density of cooperators increases with the value of the decaying factor. This indicates that the more the historical payoff is involved, the more favourable cooperators become. In the critical region where the cooperator density converges to zero, cooperators vanish according to a power-law-like behaviour. The associated exponents agree approximately with the two-dimensional directed percolation and depend weakly on the value of the decaying factor.