Effect of Strain Ratio on Fatigue Model of Ultra-fine Grained Pure Titanium

The ultra-fine grained(UFG)pure titanium was prepared by equal channel angular pressing(ECAP)and rotary swaging(RS).The strain controlled low cycle fatigue(LCF)test was carried out at room temperature.The fatigue life prediction model and mean stress relaxation model under asymmetrical stress load were discussed.The results show that the strain ratio has a significant effect on the low cycle fatigue performance of the UFG pure titanium,and the traditional Manson-coffin model can not accurately predict the fatigue life under asymmetric stress load.Therefore,the SWT mean stress correction model and three-parameter power curve model are proposed,and the test results are verified.The final research shows that the threeparameter power surface model has better representation.By studying the mean stress relaxation phenomenon under the condition of R≠-1,it is revealed that the stress ratio and the strain amplitude are the factors that significantly afiect the mean stress relaxation rate,and the mean stress relaxation model with the two variables is calculated to describe the mean stress relaxation phenomenon of the UFG pure titanium under different strain ratios.The fracture morphology of the samples was observed by SEM,and it was concluded that the final fracture zone of the fatigue fracture of the UFG pure titanium was a mixture of ductile fracture and quasi cleavage fracture.The toughness of the material increases with the increase of strain ratio at the same strain amplitude.

Microstructures of ultra-fine grained FeCoV alloys processed by ECAP plus cold rolling and their evolutions during tempering

A new processing method,equal channel angular pressing(ECAP)plus cold rolling(CR),was applied to producing ultra-fine grained FeCoV alloy.The microstructures of ultra-fine grained FeCoV alloy after ECAP,ECAP plus CR,and the effect of tempering treatment on the microstructure of FeCoV alloy produced by ECAP plus CR were investigated.The results show that an elongated substructure with a width of about 0.3μm is obtained after four-pass ECAP using Route A.Cold rolling after ECAP cannot change the morphologies of elongated substructure,and it results in higher fraction of high-angle boundaries and higher dislocation density compared with the identical ECAP without rolling.Subsequent tempering for 30 min at 853 K brings about many nano-phases precipitating at subgrain boundaries and insides the grains,and the size of precipitated phase is measured to be about 10 nm.Nano-phases grow up with increasing tempering temperature and equiaxed structure forms at 883 K.

Isothermal Growth Kinetics of Ultra-fine Austenite Grains in a Nb-V-Ti Microalloyed Steel

Ultra-fine austenite grains with size of i-3 μm were prepared in a Nb-V-Ti steel through repetitive treatment of rapid heating and quenching. A model for the growth kinetics of these ultra-fine austenite grains was successfully created through successive 2 processes, and the activation energy Q for growth was estimated to be about 693.2 kJ/mol, which directly shows the inhibition effect of microalloy elements on the growth of ultra-fine austenite grains.

Effect of welding heat input on HAZ character in ultra-fine grain steel welding

In this essay, we studied how heat input affected the microstructure, hardness, grain size and heat-affected zone(HAZ) dimension of WCX355 ultra-fine grain steel which was welded respectively by the ultra narrow-gap welding (UNGW) process and the overlaying process with CO 2 as protective atmosphere and laser welding process. The experimental results show when the heat input changed from 1.65 kJ/cm to 5.93 kJ/cm, the width of its HAZ ranged from 0.6 mm to 2.1 mm.The average grain size grew up from 2～5 μm of base metal to 20～70 μm and found no obvious soften phenomenon in overheated zone. The width of normalized zone was generally wide as 2/3 as that of the whole HAZ, and the grain size in this zone is smaller than that in base metal. Under the circumstance of equal heat input, the HAZ width of UNGW is narrower than that of the laser welding.

Microstructural Evolution and Thermal Stability of Ultra-fine Grained Al-4Mg Alloy by Equal Channel Angular Pressing

Experiments were conducted to evaluate the grain refinement and thermal stability of ultra-fine grained Al-4Mgalloy introduced by equal-channel angular pressing (ECAP) at 473 K. The results show that the intensities of X-ray(111/222) and (200/400) peaks for the alloy processed by ECAP decrease significantly and the peak widths of halfheight become broadening compared with the corresponding value in the annealed alloy. The microstructure of 2passes ECAPed alloy consists of both elongated and equiaxed subgrains. The residual strain in the alloy increaseswith increasing passes numbers, that appears as increasing dislocation density and lattice constant of matrix. Anequiaxed ultra-fine grained structure of～0.2μm is obtained in the present alloy after 8 passes. The ultra-fine grainsare stable below 523 K, because the alloy retains extremely fine grain size of～1μm after static annealing at 523 Kfor 1 h.

Effect of upsetting force on microstructure of welds in resistance spot welding of 400 MPa ultra-fine grain steel

The ultra-fine grain （UFG） steel is welded by using resistance spot welding technique with or without requirement of upsetting force. Metallographic inspection shows that the grain size of weld nugget is larger than that of the base metal and the microstructure is altered significantly. In addition, contracting defects such as air holes can be found in the nugget center. The experiments show that the defects can be effectively avoided by the technique of adding upsetting force during the nugget cooling and crystallizing processes. In tensile shear tests, the welding joint starts to crack from the inner edge of the corona bond. The results of micro-hardness tests show that the newly born martensite structure dramatically improves the hardness of the joint. Under the interactions between residual stresses and regenerated fine grains, the micro-hardness of the heat-affected zone （ HAZ ） is lower than that of the nugget, but evidently higher than that of the base metal.

Promoting the Empowerment of Science and Technology to Ensure Food Safety Production:A Case Study of Huizhou City

The current situation of grain production in Huizhou City was analyzed firstly,and then the existing problems and challenges of grain safety production were pointed out,such as increases in the pressure to ensure grain safety production and the difficulty of stable development of grain production.Finally,several countermeasures and suggestions for the stable development of grain production were put forward.

Surface Cracking Behaviors of Ultra-Fine Grained Tungsten Under Edge Plasma Loading in the HT-7 Tokamak

Tests of the candidate plasma facing materials（PFMs） used in experimental fusion devices are essential due to the direct influence of in-situ plasma loading.A type of ultrafine grained（UFG） tungsten sintered by resistance sintering under ultra-high pressure（RSUHP） method has been exposed in the edge plasma of the HT-7 tokamak to investigate its performance under plasma loading.Under cychc edge plasma loading,the UFG tungsten develops both macro and micro cracks.The macro cracks are attributed to the low temperature brittleness of the tungsten material itself,while the micro cracks are generated from local intense power flux deposition.

Investigation on fracture behavior of the welded joint HAZ of ultra-fine grain steel SS400

The critical crack dimensions of both base-metal specimen and HAZ specimen are measured via wide-plate tensile tests. Based on the “fitness for purpose” principle, the fracture behavior of the ultra-fine grain steel SS400 welded joint HAZ is assessed. The test results indicate that overmatching is benefit for the whole capability’s improvement of ultra-fine grain steel SS400. The test results are confirmed by using finite element method (FEM).

Groove Design and Microstructure Research of Ultra-Fine Grain Bar Rolling

New flat-oval groove rolling process of multi-direction deformation is proposed to manufacture ultra-fine grain bar. Application of new groove series can introduce uniform large plastic strain into whole cross section of the material, and meanwhile satisfy the requirements of shape and size. Principle of grain refinement, based on experimental research of small specimen, is that grain refinement of ferrite is mainly dynamic recrystallization when low-carbon alloy steel is at low temperature deformation. Relationship of grain size and z-factor is also obtained through experimental research, as well as ultra-fine ferrite grain less than 1 micron. To predict strain, shape, dimensions and grain size of the material in rolling process, numerical simulation model of the warm groove bar rolling process is established via nonlinear finite element method, and distribution of grain size of the final section is obtained via finite element subroutine. The result indicates that ultra-fine grain bar rolling can accomplish at low temperature region.

GRAIN & OIL SCIENCE AND TECHNOLOGY

Grain&Oil Science and Technology is a peer-reviewed international scientific journal dedicates to promoting the advancement of science and technology in grain and oil storage,grain engineering,oil engineering,food science,food nutrition and safety,new technologies and related research progress,publishes the highest quality original contributions and reviews on new achievements.

GRAIN & OIL SCIENCE AND TECHNOLOGY

Grain & Oil Science and Technology is a peer-reviewed international scientific journal dedicates to promoting the advancement of science and technology in grain and oil storage, grain engineering, oil engineering, food science, food nutrition and safety, new technologies and related research progress, publishes the highest quality original contributions and reviews on new achievements.

Gradient Ultra-fine Grained Surface Layer in 6063 Aluminum Alloy Obtained by Means of Rotational Accelerated Shot Peening

Gradient ultra-fine grained surface layer in 6063 aluminum alloy was obtained by means of a novel surface self-nanocrystallization technique,namely rotational accelerated shot peening(RASP)treatment.The average grain sizes along the vertical section vary from hundreds of nanometers in the top surface to micrometers in the matrix.By using orthogonal experimental design to compare roughness values and hardness values,we synthesized the processing parameters to obtain sample of smaller roughness values and higher hardness.

Functional Foods: Can Food Technology Help in the Prevention and Treatment of Diabetes?

Recently, the interest in functional foods is increased dramatically thanks to some scientific evidences demonstrating that, regardless of their nutritional value, some foods components beneficially influence several functions of the body, making them “functional” for the prevention and treatment of degenerative diseases, such as type 2 diabetes and cardiovascular diseases. In particular, the marketplace offers conventional and modified functional foods which acting on intestine, glucose and lipid metabolism are potentially useful for diabetic patients. The field of functional foods, however, presents some criticalities. Up to now, only few functional foods have obtained the statement of a “Health Claim”, either because there are not sufficient scientific evidences based on human intervention studies, that justify a “Health Claim”, or because data are not consistent with the proposed claims. In addition, some functional foods show a low palatability and a lack of variety. Both these issues limit their ordinary intake. This critical aspect also involves the lack of a possible synergistic effect deriving from the contemporary consumption in the diet of different functional foods, as observed with some healthy dietary pattern. Functional foods represent, then, a challenge for the food industry, which needs to implement and/or develop innovative technologies able to create new foods with improved healthy properties, but also with better organoleptic properties suitable for a daily consumption.

种植技术和种植密度对吉花2号主要农艺性状和产量的影响

研究不同种植技术和种植密度对吉林省多粒型花生吉花2号主要农艺性状和产量的影响,筛选适宜吉林省生态环境的种植技术和最佳种植密度,完善吉花2号配套高效栽培技术。采用2种种植技术及5个种植密度(1.79×10^(5)、2.02×10^(5)、2.30×10^(5)、2.69×10^(5)、3.23×10^(5)株/hm^(2)),研究特定时期花生光合指标及产量变化。结果显示,吉花2号采用小垄双行种植技术、种植密度为2.02×10^(5)株/hm^(2)时生育期最短,较双粒穴播种植技术生育期提前1~2 d;植株的株高最小,有利于地下部干物质积累;叶面积系数最大,总光合势最大;产量最高(3651.15 kg/hm^(2)),较双粒穴播种植技术增产10.17%。小垄双行种植技术在不同密度下,吉花2号产量都高于双粒穴播种植技术。因此,小垄双行种植技术在生产上应大力推广。

有土斯有粮:高标准农田建设提高了粮食单产吗?

作为“藏粮于地,藏粮于技”战略的重要政策实践,高标准农田建设被期待能够有效实现粮食增产和更好保障国家粮食安全。基于27个省(市、自治区)的面板数据,探索了高标准农田建设对粮食单产的影响及其可能机制。研究发现:(1)高标准农田建设能显著提高粮食单产。替换核心变量、进行非参数估计和考虑内生性的稳健性检验,均证实上述发现可信。(2)机制验证表明,高标准农田建设主要通过提升规模经营、促进技术进步和降低生产风险三大路径来提高粮食单产。(3)异质性分析发现,高标准农田建设对起伏度较小地形、粮食主产区、较发达地区的粮食单产促进效应更大。研究结果表明高标准农田建设确实是夯实粮食安全根基的重要举措,需扎实推进新一轮高标准农田建设工作。

江西省现代种业发展现状、问题和对策建议

通过对江西省涉农科研单位、种业公司、涉农管理部门进行调研和访谈,总结了江西省现代种业的发展现状及其存在的问题,并提出了相应的对策建议。结果表明:近年来,江西省种业发展取得了积极的成效,但仍存在农业种质资源保护不全、种业科技创新水平不高、种业企业竞争实力不强、种业监管保障能力不足等问题,并提出了健全相关法律法规、培育壮大龙头种业企业、加大种质资源保护利用力度、提升种业科技创新能力、完善种业监管保障体系等政策建议,以期为江西省现代种业高质量发展和保障国家粮食安全提供参考依据。

科技报告政策细粒度知识图谱构建及应用研究

[目的/意义]科技报告作为我国重要的科技信息资源,不断促进国家的科技创新发展。构建科技报告政策细粒度知识图谱,并探讨其应用价值,对了解、制定和优化相关的政策,保证科技报告质量,提升科技报告工作效率,促进国家科技创新具有重要意义。[方法/过程]收集并整理近10年的科技报告政策,深入挖掘其基本信息和政策文本内容,利用SciAIEngine、Excel、Gephi等工具进行细粒度知识分类聚类,构建科技报告政策细粒度知识图谱。依据政策之间的细粒度知识关联情况,探究图谱在科技报告政策领域的应用价值。[结果/结论]细粒度知识图谱可用于科技报告政策的知识查询、知识统计和内容聚类分析,还可为政策优化提供一定的依据,未来可在科技报告制度建设、科技资源共享、知识产权保护和国家科技报告服务系统方面继续探究。研究虽有所不足,但对未来研究仍有一定的帮助与启发。

农业机械化、农机服务与粮食生产技术效率——基于人口老龄化视角

基于随机前沿生产函数和多值处理效应模型,使用黑龙江省47个村粮食种植农户样本数据,研究农机服务对老龄农户和非老龄农户粮食生产技术效率的影响。结果表明:当前黑龙江省农户粮食生产平均技术效率为57.2%,总体水平偏低,技术损失较大,存在一定的提升空间;非老龄农户更能从现有的农机服务中获益,农机服务未带来老龄农户技术效率的显著提高,但使得老龄农户留在农业生产之中,形成互补关系;在播种和收获环节,农机服务对技术效率的正向影响受到人口老龄化的抑制,原因在于老龄农户倾向于投入劳动替代农机服务,在不同地块之间转移劳作的成本更高。在发展农机服务、扩大服务经营规模的同时,应考虑农业经营主体的经营特征,完善土地流转机制,促进农业适度规模经营与农机服务协调发展。

饲料粮中霉菌毒素检测技术的研究进展

霉菌毒素具有很强的毒性,广泛存在于饲料粮中。霉菌毒素经饲料粮进入动物体后,会产生明显的毒副反应,不仅会降低动物的生长性能、免疫力和饲养经济效益,而且容易转移到动物源性食品中,危及人体健康。在饲料工业和畜牧养殖业中,如何高效、便捷、低成本检测霉菌毒素的污染情况至关重要。因此,本文阐述霉菌毒素的种类及危害,并罗列了常见的霉菌毒素检测技术,以期为霉菌毒素检测技术的推广和研发提供参考。