Effects of Ridge-Mulching with Plastic Sheets for Rainwater-Harvesting Cultivation on WUE and Yield of Winter Wheat

A field experiment was conducted in a manural loesial soil in middle of Shaanxi Province ofChina, a sub-humid area prone to drought, to study the effects of rainwater-harvestingcultivation on water use efficiency (WUE) and yield of winter wheat. Ridge-furrow tillage wasused, the ridge being mulched by plastic sheets for rainwater harvesting while seeding in thefurrows. Results showed that from sowing to reviving stage of winter wheat, water stored in 0-100 cm layer was significantly decreased whereas that in 100-200 cm layer did not change.Compared to the non-mulching, plastic mulch retained 6.5 mm more water as an average of the twoN rate treatments, having a certain effect on conservation of soil moisture. In contrast, atharvest, water was remarkably reduced in both the 0-100 cm and the 100-200 cm layers, andmulched plots consumed 34.8 mm more water as an average of the two treatments: low N rate (75kg N ha-1) with low plant density (2 300 000 plants ha-1) and high N rate (225 kg N ha-1)with highplant density (2 800 000 plants ha-1), in 0-200 cm layer than those without mulching, the formerbeing beneficial to plants in utilization of deep layer water. Mulching was significant inharvesting water and in increase of yield. Mulched with plastic sheets, biological and grainyields were 22.5 and 22.6% higher for the average of the high N rate than for the low N rate,and the high N rate with low plant density was 29.8 and 29.1% higher in both biological andgrain yields than that of the low N rate with low plant density. With high N rate and high plantdensity, the mulched biological and grain yields were 39.5 and 28.9% higher than the correspondingtreatments without mulching. Of the treatments, that with high N rate and low plant density wasthe highest in both biological and grain yields, and the water use efficiency reached 43.7 kgmm-1 ha-1 for biological yield and 22 kg mm-1 ha-1 for grain yield, being the highest WUE reportedin the world up to now.

Effects of plastic sheet on water saving and yield under furrow irrigation method in semi-arid region

The increasing demand of water in the country highlights the need to introduce low-input and water saving technologies for agricultural sustainability and crop production,mainly in semi-arid region.A study was conducted to minimize deep percolation losses from the furrow bottom under two different irrigation treatments viz.(1)furrow bottom with plastic sheet(T1)and(2)furrow bottom without plastic Sheet(T0).The physical and chemical analyses of soil profile were taken at a depth of 0-80 cm before and after crop harvesting.The dry density of soil slightly increased(0.01 g/cm^(3))under both treatments,while soil pH decreased under T1.The average yield was 8332 kg/hm^(2) and 7575 kg/hm^(2),with 21.56 m^(3) and 31.09 m^(3) total volume of irrigation water applied under T1and T0,respectively.The saving percentages of water under treatments were 52.22% and 31.00% under T1 and T0 respectively as compared to the saving of water under traditional irrigation practice.Overall,better performance,in terms of crop production and water saving,was obtained with use of plastic sheet integrated with bottom of furrows.Hence,it is suggested that the furrow irrigation method with plastic sheet may be used to preventing moisture and minimize deep percolation losses from furrow bottom.

Square concrete columns strengthened with carbon fiber reinforced plastics sheets at low temperatures

Twenty-one square concrete columns were constructed and tested. The testing results indicate that bonded carbon fiber reinforced plastics(CFRP) sheets can be used to increase the strength and improve the serviceability of damaged concrete columns at low temperatures. The failure of the specimens,in most cases,takes place within the middle half of the columns. And the failure of strengthened columns is sudden and explosive. The CFRP sheets increase both the axial load capacity and the ultimate concrete compressive strain of the columns. The ultimate loads of strengthened columns at-10,0 and 10 ℃ increase averagely by 9.09%,6.63% and 17.83%,respectively,as compared with those of the control specimens. The axial compressive strength of strengthened columns is related to the curing temperatures. The improvement of axial compressive strength decreases with reducing temperature,and when the temperature drops to a certain value,the improvement increases with falling temperature.

IDENTIFICATION OF ELASTIC-PLASTIC MECHANICAL PROPERTIES FOR BIMETALLIC SHEETS BY HYBRID-INVERSE APPROACH

Analysis, evaluation and interpretation of measured signals become important components in engineering research and practice, especially for material characteristic parameters which can not be obtained directly by experimental measurements. The present paper proposes a hybrid-inverse analysis method for the identification of the nonlinear material parameters of any individual component from the mechanical responses of a global composite. The method couples experimental approach, numerical simulation with inverse search method. The experimental approach is used to provide basic data. Then parameter identification and numerical simulation are utilized to identify elasto-plastic material properties by the experimental data obtained and inverse searching algorithm. A numerical example of a stainless steel clad copper sheet is consid- ered to verify and show the applicability of the proposed hybrid-inverse method. In this example, a set of material parameters in an elasto-plastic constitutive model have been identified by using the obtained experimental data.

Analysis of FCC sheet metal forming with rate-independent polycrystalline plasticity FEM

A rate-independent polycrystalline plasticity constitutive model considering self and latent hardening was developed. Next, a new orientation probability assignment method was proposed and the crystal orientations were assigned to FE integration points, which represent crystals and can rotate individually. Then cup drawing of FCC aluminum sheet was studied using crystalline plasticity finite element analysis. The results show that the validity of proposed model is proved through comparison between numerical results and experimental ones. {001}<110> texture can lead to earing at 45° direction, while {124}<211> texture at 0° and 90° directions. For the rolled aluminum sheet, which contains strong {001}<110> texture, earing is formed at 45° direction after cup drawing. For the annealing aluminum sheet, due to the balance between two main textures, the flange earing tendency is not obvious.

基于PLC的可降解塑料片材成型自动化生产线设计

塑料片材是塑料制品中的重要组成部分,然而现有的塑料片材生产线自动化程度较低,原料主要成分为聚乙烯,难以降解。据此,采用一种新型的可降解塑料作为原料,但此原料是粉状料,无法适用于传统的粒状送料装置;由于其特点是通过挤出后离模发泡的方式成型为片材,并且原料对温度要求较高,传统挤出机无法使用此料生产。因而根据此原料特性和加工工艺设计由送料系统、挤出成型系统、牵引滚压系统、分切冲孔系统及夹取码垛系统组成的可降解塑料片材成型生产线,使用PLC和触摸屏对控制系统的硬软件进行设计。以平均生产节拍作为参考指标,此自动化产线生产效率提高了26.5%,为可降解塑料产品的规模应用提供了技术支撑。

小流域河道综合整治中塑钢板桩护岸技术应用研究

为研究塑钢板桩护岸技术在小流域河道综合整治中的应用效果,结合实例,对比塑钢板桩护岸技术、生态仿木桩护岸技术、插板桩护岸技术优缺点及适用性,确定塑钢板桩护岸方案并对其进行优化设计及计算,确定塑钢板桩结构形式。经施工统计,塑钢板桩护岸日施工进度可达22.4~33.6延米,优于生态仿木桩护岸、插板桩护岸,护岸土层剪应力为6 kPa~12 kPa,剪应力不大,说明塑钢板桩护岸工后稳定性良好。

星形下料器内产生塑化片的原因及对策

介绍了星形下料器的特点,分析了星形下料器运行过程中出现问题的原因,提出了改造、优化星形下料器密封的措施——优化气封输送形式和增大叶轮与特体间隙。改造后效果良好,后续运行中堵塞现象很少发生,检修次数大幅度降低。

基于SOM-FDA利用XRF对药品铝塑包装片的分类

建立了一种对药品铝塑包装片进行快速分类的方法。利用能量色散型X射线荧光光谱(XRF)仪,对47种不同的药品铝塑包装片样品进行了检验,结合自组织映射(self organizing map,SOM)神经网络聚类,通过最大相关性最小冗余(maximum relevance minimum redundancy,MRMR)算法对元素重要性进行排序,并利用最近邻(K-nearest neighbor,KNN)分类器处理样品数据。依据样品中所含元素的种类及质量分数的不同,对药品铝塑包装片进行区分。SOM神经网络聚类的结果为9类,KNN分类器的准确率为97.87%。X射线荧光光谱法操作简便快速、无损检材、灵敏度高。建立的分类模型科学准确,可为公安机关大规模筛选、确定侦查方向、缩短侦查时间提供帮助。

复杂地质条件下钢板桩引孔施工技术研究与应用

本文以某项目工程为例,通过了解该项目地质特性,确定施工方案,重点从旋挖引孔、引孔灌砂、插打钢板桩、承台施工及钢板桩拆除等具体施工技术进行论述,最后对钢板桩围堰稳定性进行验算及监测,结果显示各杆件稳定性均符合要求,基坑水平位移监测数据达标,验证了该工艺的可行性。

Numerical Determination of Shear Strength of Steel Reinforced Concrete Column Strengthened by CFRP Sheets

The earthquake resistant property of reinforced concrete members depends on the interaction between reinforcing bars and surrounding concrete through bond to a large degree. In this paper a general system aimed at dealing with the failure analysis of reinforced concrete columns strengthened with carbon fiber reinforced plastic (CFRP) sheets including bond slip of the anchored reinforcing bars at the foot of the columns is presented. It is based on the yield design theory with a mixed modeling of the structure, according to which the concrete material is treated as a classical two dimensional continuum, whereas the longitudinal reinforcing bars are regarded as one dimensional rods including bond slip at the foot of the columns. In shear reinforced zones both the shear CFRP sheets and transverse reinforcing bars are incorporated in the analysis through a homogenization procedure and they are only in tension. The approach is then implemented numerically by means of the finite element formulation. The numerical procedure produces accurate estimates for the loading carrying capacity of the shear members taken as an illustrative application by correlation with the experimental results, so the proposed approach is valid.

Feature of flow stress of aluminum sheet used for can during hot compression

The flow stress feature of aluminum sheet used for pressure can during plastic deformation at elevated temperature was studied by isothermal compression test using Gleeble 1 500 dynamic materials testing machine. The experimental results show that the steady state deformation is remarkable when the material is deformed in the temperature range of 350～500 ℃ at strain rates within the range of 10 -2 ～10.0 s -1 . The material is sensitive to positive strain rate. A hyperbolic sine relationship is found to correlate well the flow stress with the strain rate, and an Arrhenius relationship with the temperature. Semi empirical constitutive equations of the flow stress are derived from all experimental data for tested material during plastic deformation at elevated temperature by polyelement linear regression analysis. [

A Mechanics Model for Stamping a Sheet on Elastic Die with Large Deformation

A semi analytical method was proposed to solve the mechanics problem of stamping a sheet on elastic die. The sheet was divided into four parts according to its deformation and contact with the punch and elastic die. Analytical solutions were derived individually for each part by using elastic large deflection and plastic large deformation. Solutions were found out with MATLAB by developing a numerical algorithm. Interface forces were obtained by iteration under the compatibility conditions between the neighboring parts of the sheet. Computation shows the method is efficient.

BEHAVIOR OF FLOW STRESS OF ALUMINUM SHEETS USED FOR PRESSURE CAN DURING COMPRESSION AT ELEVATED TEMPERATURE

The behavior of flow stress of Al sheets used for pressure can prepared by different melt-treatment during plastic deformation at elevated temperature was studied by isothermal compression test using Gleeble1500 dynamic hot-simulation testing machine. The results show that the AI sheets possess the remarkable characteristic of steady state flow stress when they are deformed in the temperature range of 350-500℃ at strain rates within the range of 0.01-10.0s^-1. A hyperbolic sine relationship is found to correlate well the flow stress with the strain rate, and an Arrhenius relationship with the temperature, which implies that the process of plastic deformation at elevated temperature for this material is thermally activated. Compared with the AI pieces prepared by no or conventional melt-treatment, hot deformation activation energy of AI sheets prepared by high-efficient melt-treatment is the smallest （ Q= 168.0kJ/mol）, which reveals that the hot working formability of this material is very better, and has directly to do with the effective improvement of its metallurgical quality.

Influence of Transverse Normal Pressure on Deformation Behavior of Sheet Metal

To investigate the influence of magnitude and distribution of the transverse normal pressure on deformation behavior of sheet metal,viscous pressure bulge test (VPB) of overlapping sheet metals is proposed,where the overlapped sheet metal is deformed under the dual-sided normal pressure provided by viscous medium and the overlapping sheet.The transverse normal pressure loading features provided by overlapping sheet metals are first simulated by DEFORM-2D.It shows that the magnitude and space distribution of transverse normal pressure are dependent on strain hardening exponent n-,strength coefficient K-and thickness t-values of the overlapping sheet metal.Based on the stress,deviator stress and strain distribution resulted from the finite element simulation,it indicated that the uniform transverse normal pressure has no effect on deviator stress,the figure and strain distribution of bulge specimens have no change.The non-uniform transverse normal pressure can remarkably change the figure and metal flow of specimens,and the formability of sheet metal can be improved by controlling the transverse normal pressure distribution.

STUDY ON THE PROBLEMS OF CONTACT IN THE NUMERICAL SIMULATION OF SHEET FORMING

This study is concerned with the problems of contact in the process of numerical simulation of sheet metal forming in rigid visco-plastic shell FEM. In respect of analysis of sheet deep drawing process,for the tool model described by triangular elements, a kind of contact judging algorithm about the correlation between the node of deformed mesh and the triangular element of a tool is presented. In SPF/DB Lagrangian multiplier method is adopted to solve the contact problem between deformed meshes, and a new reliable practical dynamic contact checking algorithm is presented. As computation examples, the simulation results of metal sheet deep drawing and SPF/DB are introduced in this paper.

PREDICTION OF PATH-DEPENDENT FAILURE IN ALUMINUM SHEET METALS UNDER FORMING OPERATIONS

An approximate macroscopic yield criterion for anisotropic porous sheet metals is adopted in a failure prediction methodology that can be used to investigate the failure of sheet metals under forming operations. This failure prediction methodology is developed based on the Marciniak-Kuczynski approach by assuming a slightly higher void volume fraction inside randomly oriented imperfecte analysis. Here, a nonproportional deformation history including relative rotation of principal stretch directions is identified in a selected critical element of an aluminum sheet from a FEM fender forming simulation. Based on the failure prediction methodology, the failure of the critical sheet element is investigated under the non-proportional deformation history. The results show that thiven non-proportional deformation history.

精确预测近平面应变载荷下各向异性行为的屈服准则参数识别策略

随着现代汽车工业对冲压零部件成形精度要求的不断提高,描述商用汽车板材变形行为的模型的精度也必须相应提高。在此背景下,结合当前工业级实验室检测能力,提出一种基于单轴拉伸、等双轴拉伸和近平面应变数据标定先进各向异性屈服准则的参数识别策略。将新提出的校准方法应用于BBC2008屈服准则并与其他几种屈服准则(包括工业界广泛使用的Hill48和Barlat89,以及与BBC2008灵活性相当的Yld2004-18p、Yld2011-27p、Yoshida2013和Poly4*Hosford)进行比较。通过定量评估MP980和SPCE钢以及5182-O和A6XXX-T4铝合金的法平面屈服轨迹、对角线平面剪切屈服轨迹、等双轴和单轴拉伸屈服应力与塑性应变比的预测误差,验证了新参数识别策略的有效性和适用性。结果表明,新方法能够全面提升塑性各向异性方面的描述能力,尤其是对于对角线平面剪切屈服轨迹。不同屈服准则对商用汽车板材各向异性行为的描述能力表现出非常大的差异性。特别地,在使用相同力学性能数据校准屈服准则的前提下,释放指数的潜在调节能力比增加材料参数的数量更加重要。

不同屈服准则对MP980钢和5182-O铝合金塑性各向异性描述能力研究

基于MP980钢和5182-O铝合金沿轧制方向成不同角度的单轴拉伸和不同加载路径下的十字型试样双轴拉伸实验数据,通过计算测量数据与不同材料模型预测的单轴拉伸屈服应力与r值、等双轴拉伸屈服应力与r值和塑性功轮廓线的预测误差进行定量评估,分析了使用不同材料参数识别策略的Hill48、新数学形式的Barlat91(New)和Yld2000-2d各向异性屈服准则在描述塑性各向异性方面的能力,评价了这些材料模型的有效性和适用性。结果表明,使用应力各向异性数据识别材料参数,在描述与应力相关的实验数据时更为精确,使用变形各向异性数据识别材料参数,在描述r值时更加精确。包含更多材料参数的Yld2000-2d屈服准则相比于Hill48和Barlat91(New)可以更精确地反映两种板材的各向异性屈服行为。在使用完全相同的力学性能识别屈服准则的材料参数时,高阶模型对塑性功轮廓线具有更高的预测精度。

可降解塑料片材机头流道的流场分析及设计优化

针对可降解塑料片材机头挤出的片材不规整且表面呈波浪状褶皱的问题,基于Polyflow对可降解塑料片材的挤出过程进行模拟,计算并分析了挤出过程中速度、压力、剪切速率的分布,根据数值模拟的结果优化机头流道结构,并和原有机头流道进行对比。结果表明,优化后的机头流道提高了熔体流动速度,增强了出入口的熔体流动性能,提高了流道内成型段的压力降,提升了充模速度和熔体流率,提高了机头的剪切速率,有利于流道内物料混合均匀,解决了片材不规整及表面褶皱的问题。