Analysis of plane strain bending of a strain hardening curved beam based on unified yield criterion

The analysis of plane strain elastic-plastic bending of a linear strain hardening curved beam with a narrow rectangular cross section subjected to couples at its end is conducted based on a unified yield criterion. The solutions for the mechanical properties of plane strain bending are derived, which are adapted for various kinds of non-strength differential materials and can be degenerated to those based on the Tresca, von Mises, and twin-shear yield criteria. The dependences of the two critical bending moments, the radii of the interfaces between the elastic and plastic regions and the radial displacements of the points at the symmetrical plane on different yield criteria and Poisson’s ratios are discussed. The results show that the influences of different yield criteria and Poisson’s ratio on the two critical bending moments, the radii of the interfaces between the elastic and plastic regions and the radial displacements of the points at the symmetrical plane of the curved beam are significant. Once the value of bis obtained by experiments, the yield criterion and the corresponding solution for the materials of interest are then determined.

Analytical computation of support characteristic curve for circumferential yielding lining in tunnel design

Circumferential yielding lining is able to tolerate controlled displacements without failure,which has been proven to be an effective solution to large deformation problem in squeezing tunnels.However,up to now,there has not been a well-established design method for it.This paper aims to present a detailed analytical computation of support characteristic curve(SCC)for circumferential yielding lining,which is a significant aspect of the implementation of convergence-confinement method(CCM)in tunnel support design.Circumferential yielding lining consists of segmental shotcrete linings and highly deformable elements,and its superior performance mainly depends on the mechanical characteristic of highly deformable element.The deformation behavior of highly deformable element is firstly investigated.Its whole deforming process can be divided into three stages including elastic,yielding and compaction stages.Especially in the compaction stage of highly deformable element,a nonlinear stress-strain relationship can be observed.For mathematical convenience,the stress-strain curve in this period is processed as several linear sub-curves.Then,the reasons for closure of circumferential yielding lining in different stages are explained,and the corresponding accurate equations required for constructing the SCC are provided.Furthermore,this paper carries out two case studies illustrating the application of all equations needed to construct the SCC for circumferential yielding lining,where the reliability and feasibility of theoretical derivation are also well verified.Finally,this paper discusses the sensitivity of sub-division in element compaction stage and the influence of element length on SCC.The outcome of this paper could be used in the design of proper circumferential yielding lining.

Milk Yield of Holstein Cows Induced into Lactation Twice Consecutively and Lactation Curve Models Fitted to Artificial Lactations

Nineteen multiparous barren Holstein cows were subjected to an induction of lactation protocol for 21 d administering estradiol cypionate （2 mg kg-1 of body weight （BW） d-1, on day 1 to 14）, progesterone （0.10 mg kg-1 of BW, on day 1 to 7）, lfumethasone （0.03 mg kg-1 of BW, on day 18 to 20） and recombinant bovine somatotropin （rbST;500 mg per cow, on day 1, 6, 16 and 21）. At the end of lactation and with a minimum of a 2-mon dry period, the same cows were again hormonally induced into lactation. Cows in both lactations were not artiifcially inseminated, they were milked 3 times daily and received rbST throughout lactation. Mean accumulated milk yield at 305 d in milk （DIM） did not differ between the ifrst and second induced lactations （（9 710 ＆#177;1 728） vs. （9 309＆#177;2 150） kg;mean＆#177;SD）. Total milk yield （（12 707＆#177;3 406） vs. （12 306＆#177;4 218） kg;mean＆#177;SD） and lactation length （（405＆#177;100） vs. （410＆#177;91） d;mean＆#177;SD） were not different between the ifrst and second induced lactations. In a second study, 15 empirical models including exponential, power law, yield-density, sigmoidal and miscellaneous models were compared for their suitability by modeling 12-mon （n=334）, 18-mon （n=164） and 29-mon （n=22） lactation cycles of Holsteins cows induced into lactation and treated with rbST throughout the lactation. Hoerl （Y=ab1/xxc）, Wood （Y=axb exp（cx）） and Dhanoa （Y=ax（bc）exp（cx）） models were equally suitable to describe 12-mon lactations. An exponential model with ifve parameters （Y=exp（a＋bx＋cd2＋e/x）） showed the best ift for milk yield for 18-mon lactations. The rational model （Y=a＋bx/1＋cx＋dx2） was found to produce the closest ift for 29-mon lactations. It was concluded that, with the protocol used in the present study, multiparous cows respond favorably to a second cycle of induced lactation, with milk yield similar to that experienced during the ifrst cycle. Thus, dairy producers might be able to lengthen the productive life of infertile high producing cows with a renewal of artiifcial lactation, which would imply an overall reduction in voluntary culling of cows. Also, various equations used to describe the lactation curves demonstrated the potential for iftting monthly milk records of Holstein cows with prolonged lactations and induced hormonally into lactation.

Stress—strain curves for different loading paths and yield loci of aluminum alloy sheets

To carry out biaxial tensile test in sheet metal, the biaxial tensile testing system was established. True stress—true strain curves of three kinds of aluminum alloy sheets for loading ratios of 4:1, 4:2, 4:3, 4:4, 3:4, 2:4 and 1:4 were obtained by conducting biaxial tensile test in the established testing systems. It shows that the loading path has a significant influence on the stress—strain curves and as the loading ratio increases from 4:1 to 4:4, the stress—strain curve becomes higher and n-value becomes larger. Experimental yield points for three aluminum alloy sheets from 0.2% to 2% plastic strain were determined based on the equivalent plastic work. And the geometry of the experimental yield loci were compared with the yield loci calculated from several existing yield criteria. The analytical result shows that the Barlat89 and Hosford yield criterion describe the general trends of the experimental yield loci of aluminum alloy sheets well, whereas the Mises yield criterion overestimates the yield stress in all the contours.

Short Stroke Control with Gaussian Curve and PSO Algorithm in Plate Rolling Process

The precision width control is vital for product quality and production economy in plate width control process, so short stroke control method was used in plate rolling by opening or closing edger gap so as to avoid head end necking. Head end necking on different broadening ratio was analyzed, and sections of different elongations at edger roiling was calculated; based on the law of volume constancy, the adjustment functions were described by parabolic functions. Control curves were developed with three Gaussian curves by means of additional combining; SSC control curve was changed with different weights of those curves, w1 effect one-third of SSC length, w2 effect two-third of SSC length, w3 effect all three parts of SSC length. In order to adjust the amount of weights for precise quantification, PSO algorithm was used to build sufficiency function so as to obtain best rectangular degree by global optimization. Practical applications showed that the method proposed is available to improve the product rolling yields by 1.0% -2. 0% and worthy to apply to plate rolling.

Comparison among Growth, Photosynthesis and Yield in Nanjing 9108 and Its Parents during the Late Development Stage

A good quality, high yield, slow mature and middle season Japonica rice variety, Nanjing 9108 and its parents Guandong 194 and Wuxiangjing 14,were taken as the materials for the study. The growth and photosynthetic characteristics of the rice plants at the post-flowering stage were compared and the rice yield components were examined at harvest. The results showed that as compared with Wuxiangjing 14, the per plant yield of Nanjing 9108 was 7.70% higher, and much higher than that of Guandong194. The large total grain per plant and heavy grain weigh of Nanjing 9108 were the important structure basis for its yield. Further analysis o the growth indicators showed that Nanjing 9108 had a large leaf area of upper three green leaves area and a smaller leaf base angle in the third leaf from the bottom blades, which helped get a higher photosynthetic capacity in groups. On the14 thday after flowering, Nanjing 9108 had similar value of net photosynthetic rate（Pn） to that of Wuxianjing 14, but lower than that of Guandong 194. Viewing from the parameters obtained from light response of photosynthesis on the modified model of rectangular hyperbola, Pn of Nanjing 9108 was more aptated to be saturated by light intensity and sensitive to photoinhibition. On the whole, Nanjing 9108 with high yield mainly resulted from its good plant type, grain structure and higher photosynthetic capacity in groups. Further improving its photosynthetic capacity o single leaf in Nanjing 9108 would be an important way for its super high yield po tential in the future.

Effects of Row-Spacing on Canopy Structure and Yield in Different Plant Type Rice Cultivars

Two japonica rice varieties, Longjing 20 （more tillers and curved panicle type, MCP） and Longjing 21 （few tillers and half erect panicle type, FEP）, were used to study the effects of row-spacing on canopy structure, morphological characteristics and yield. The results showed that the percentage of productive tiller reduced first, and increased afterwards as row-spacing increasing. The relationship between row spacing and the percentage of productive tiller fitted a quadratic regression. The effects of row spacing on leaf area index （LAI） at later tillering stage and the highest stem number per square meter also followed a quadratic regression relationship with increasing first and then reducing. The effects of row-spacing on primary branch were larger than the secondary branch in Longjing 20. However, the trend in Longjing 21 was opposite. The relationship between row spacing and seed setting rate of the secondary branch or panicle was negatively correlated. An extreme significant negative correlation was obtained between seed setting rate of secondary branch in Longjing 20. There was no significant positive correlation between row-spacing and yield in Longjing 20 （R2=0.68）. However, the negative correlation between row-spacing and yield of Longjing 21 was extremely significant （R2=–0.96＊＊）. The canopy structure of MCP was more sensitive to row-spacing. The positive correlation between row spacing and the length of the flag leaf （R2=0.89＊＊）, the width of the flag leaf （R2=0.85＊）, the length of the last internode （R2=0.85＊）, the length of the last 2nd internode （R2=0.96＊＊） or the length of the panicle （R2=0.91＊＊） was significant or extremely significant in Longjing 20, but not in Longjing 21. The wider row-spacing promoted the accumulation of the dry matter of panicle, stem and leaf and the yield formation in MCP. The best row-spacing in Longjing 20 was 30 cm. For Longjing 21, the narrower row-spacing was better. The best row-spacing of it was 21 cm. These results suggested that improved the population environment of MCP or the utilization of the free space in the field of FEP could be reached either by wider row-spacing or narrow row-spacing.

Compatibility of the Support System Consisting of Yielding Elements and Shotcrete Lining in Highly Faulted Grounds

The design procedure is made for a mine shaft where permanent underground facilities are interconnected. The highly faulted grounds were identified using empirical and semi-empirical theories. Furthermore, the behavior types are presented. This paper presents excavation and support methods in such ground conditions and the calculations results show that the installation of the yielding elements have an effect on support elements and prevent shotcrete damage during the curing stage. Different numerical analyses carried out showed that, with the yielding elements installed, the total displacements increase but the final axial force reduces, and therefore, the characteristic compressive strength of shotcrete is not exceeded. The calculation results of ground loads and displacements on the designed support system are presented with a 3D numerical geo-mechanical model adopted for highly faulted ground surrounding deeper complex underground structures.

一种新型组合式弯曲型金属阻尼器性能研究

为解决U形阻尼器承载能力低、耗能性差的问题,文中提出了由U形金属板与X形金属板组成的一种新型组合式弯曲型金属阻尼器,基于随动强化模型对阻尼器进行静力循环模拟加载,采用ABAQUS软件进行仿真研究,发现组合式金属阻尼器滞回性能和承载能力均有提高,比U形阻尼器承载能力提高了24%,根据材料屈服强度的理论分析,当X形金属板的材料屈服应力大于307.38 MPa时,组合式金属阻尼器可实现双级屈服效果,仿真中选用Q235B钢U形板和Q345B钢X形板,组合式金属阻尼器取得了较好的双阶段屈服效果。

基于C++的金属丝线屈服曲线的设计与实现

在工业生产实践中,金属丝线折弯成型是常见的加工工艺过程.例如:弹簧机将钢丝压出弹簧,眼镜绕框机将框丝绕出眼镜框型等.该类设备都有一个送丝机构,将直的金属丝推入由动、静轮为主要部件构成的成型机构中挤压变形,从而加工出不同形状、不同大小的框型产品.以自动眼镜绕框机系统为例,说明金属框丝形变与动轮压力角度之间函数关系的建立及使用C++语言实现过程.

增氧灌溉对温室番茄生长及光响应特征的影响

为提高温室番茄产量和光能利用能力,基于温室盆栽试验,设置了3个溶解氧质量浓度梯度5,15,25 mg/L(即处理A1,A2和A3),采用直角双曲线模型、非直角双曲线模型等6种模型对温室番茄叶片进行了光响应曲线拟合,分析了不同增氧水平对温室番茄生物量、产量、光响应曲线模型及光响应参数的影响.结果表明:处理A2下番茄地上部鲜质量、干质量,地下部鲜质量、干质量,根冠比和产量均达到最大,较处理A1分别提升了25.65%,17.62%,13.35%,36.80%,16.25%和33.82%(P<0.05).番茄地上部质量和产量与气孔导度(G S)、胞间CO 2浓度(C i)和蒸腾速率(T r)呈极显著正相关,地下部干质量与G S,C i呈显著正相关,与T r呈极显著正相关.处理A2下温室番茄叶片的最大净光合速率(P n max)、光饱和点(LSP)、暗呼吸速率(R d)和表观量子效率(α)等光响应参数达到最大,光补偿点(LCP)达到最小.6种模型中,直角双曲线修正模型拟合的光响应曲线其R 2最大,均高于0.992,而RMSE和MAE最小,分别在0.447和0.383以下;对P n max,LSP,LCP和R d等参数的拟合值更接近于实测值.因此,溶解氧质量浓度为15 mg/L更有助于温室番茄高产;直角双曲线修正模型是适合增氧灌溉下温室番茄光响应曲线拟合的最优模型.

β成核剂对PPH拉伸双屈服行为的影响

均聚聚丙烯(PPH)广泛应用于制备餐盒和编织袋,加入β成核剂后,改善了PPH的韧性,但是,关于β成核剂对其拉伸双屈服行为影响的研究仍较少。因此,将β成核剂加入PPH熔体中,制备β⁃PPH粒料,再进行注射成型,得到样条测试其性能。将β成核剂加入PPH后,熔融曲线中出现了明显的β晶型熔融峰,随着其结晶峰值温度的升高,PPH的结晶能力得到提高,当β成核剂的含量为0.2%时,PPH中β晶型的相对含量达到最大值,其值为49.8%,断裂伸长率达到最佳;当β成核剂的添加量大于0.2%时,PPH中β晶型的相对含量逐渐降低,断裂伸长率下降。采用50 mm/min的速率进行拉伸,PPH发生高应力的双屈服行为,其第二次屈服应力值为35.53 MPa。而β⁃PPH的2次屈服应力值均较低,与β⁃PPH的第一次屈服应力值相比,其第二次屈服应力值更低,第一个屈服阶段,β⁃PPH产生应力发白现象且温度无明显变化;第二个屈服阶段,β⁃PPH产生局部颈缩且有明显温升现象。随着β成核剂含量的增大,β⁃PPH的第一次屈服应变值、第一次屈服应力值及第二次屈服应力值均减小,第二次屈服应变值增大。

商业银行普通金融债超额收益影响因子研究

商业银行普通金融债是我国债券市场的重要品种,近年来发行交易较为活跃。本文运用小样本稳健的自助法,以2010年至2021年我国商业银行普通金融债收益率和超额收益为对象进行研究,发现政策性银行债收益率曲线前三个主成分(水平、斜率和曲率)以及社会融资规模增速波动项对商业银行普通金融债超额收益具有显著影响,而收益率曲线更高阶主成分、通货膨胀趋势、债券供给的影响并不显著。实证结果表明,社融增速波动项可能是商业银行普通金融债超额收益定价因子,与超额收益呈负相关关系。本文的结论为新兴市场债券定价以及金融债定价的相关研究提供了有益补充。建议商业银行和市场投资者综合考虑收益率曲线形态和社融增速,合理评估金融债供给波动的短期影响,妥善安排债券发行和投资。

Mechanical behaviour of wood compressed in radial direction-part I.New method of determining the yield stress of wood on the stress-strain curve

A test equipment was developed,which allows for real time observation of the deformation behav-ior of wood cellular structure under a compression load applied in radial direction.Compression tests were performed on jack pine(Pinus banksiana)and balsam poplar(Populus balsamifera)spec-imens to explore the relationship between the yield stress and the first failure occurring in wood cell layers during radial compression.The microstructural changes for P.banksiana and P.bal-samifera wood below and above the yield point were analyzed.The study results showed that for P.banksiana the first failure of wood cells occurred at the first earlywood layer,while for P.balsamifera it occurred at the layer with the largest vessels.The first failure of wood cell layer for each species tested was found to correspond to the yield point on the stress-strain curve.A new method of determining the yield stress for wood specimens under radial compression was developed.

单位涌水量的换算方法对比与讨论

《煤炭矿井防治水设计规范》中规定评价含水层富水性,是利用以孔径91 mm、抽水水位降深10 m为准的钻孔单位涌水量来进行评价,而在应用过程时常面临抽水孔径和抽水水位降深不统一的问题。在传统的单位涌水量的换算方法中,通常对3次抽水试验资料进行拟合修正降深,之后进行井径的换算,并且为方便计算假定R_(91)与R_(孔)相同,其计算误差有待于进一步验证。本研究基于前人3次抽水试验实测数据,提出首先采用迭代计算进行井径的换算,并分别计算R_(91)和R_(孔),之后采用MATLAB软件进行Q-S曲线的拟合展开分析。探究结果表明:提出的方法能够分别计算出R_(91)和R_(孔),两种方法计算的单位涌水量分别为0.148 L/(s·m)和0.1303L/(s·m),结果表明将R_(91)与R_(孔)等效处理,会存在一定的误差。

东佛里生羊杂交改良湖羊泌乳性能分析

为了探讨东佛里生羊作为父本对湖羊的杂交改良效果,试验以东佛里生羊(31只)、东佛里生(♂)×湖羊(♀)杂交一代(F1代,204只)、东佛里生(♂)×湖羊(♀)级进杂交二代(F2代,156只)、湖羊(45只)4个试验群体为研究对象,测定了东佛里生羊、F1代和F2代8个月的泌乳量和湖羊3个月的泌乳量,计算4个试验群体的月泌乳量、周泌乳量、总泌乳量和日均泌乳量;分析品种、产羔数、胎次和年龄对母羊泌乳量的影响,比较Wood模型、Wilmink模型和逆多项式模型对4个试验群体泌乳曲线的拟合度(R2),筛选拟合度最高的模型拟合4个试验群体的泌乳曲线。结果表明:东佛里生羊总泌乳量和日均泌乳量分别为(243.19±1.64)kg和(1.01±0.05)kg,显著高于F1代[(227.54±0.61) kg和(0.95±0.02)kg]、F2代[(230.09±0.65)kg和(0.96±0.02)kg]和湖羊[(71.36±1.32) kg和(0.79±0.05)kg,P<0.05];F1代、F2代的总泌乳量和日均泌乳量均显著高于湖羊(P<0.05),其中日均泌乳量分别较湖羊提高了20.25%和21.52%。产羔数对4个试验群体的泌乳量影响均不显著(P>0.05),但产多羔母羊的泌乳量总体高于产单羔母羊。经产母羊的泌乳量总体高于初产母羊;5胎次母羊的日均泌乳量最大[(1.03±0.10)kg],显著高于其他胎次(P<0.05);1胎次母羊的泌乳量最小,为(0.93±0.02)kg。随着年龄的增长,母羊总泌乳量呈现增加趋势;1~4岁母羊的总泌乳量分别为(223.33±0.87)kg、(226.51±0.60)kg、(236.60±0.87)kg和(237.59±1.66)kg,日均泌乳量分别为(0.93±0.03)kg、(0.94±0.02)kg、(0.99±0.03)kg和(0.99±0.06)kg, 3,4岁母羊的总泌乳量、日均泌乳量均显著高于1,2岁母羊(P<0.05);4岁母羊第1,3,4,6个月泌乳量均最大,而3岁母羊第2,5个月泌乳量最大。4个试验群体的Wood模型的R2均最大,由Wood模型可知东佛里生羊泌乳潜力最大,湖羊泌乳潜力最小;湖羊在第4周达到泌乳高峰,而东佛里生羊、F1代和F2代在第8周达到泌乳高峰。说明通过与东佛里生羊杂交可以明显改善湖羊的泌乳性能;产羔数对母羊泌乳量影响不明显,胎次和年龄对母羊泌乳量有明显影响,其中Wood模型对4个试验群体泌乳曲线的拟合效果最好。

多阶段屈服U形金属阻尼器抗震性能研究

针对传统金属阻尼器低位移水平下耗能能力不足,高位移水平下过早失效,难以满足结构耗能需求的问题,提出一种由2种不同尺寸作为耗能组件的U形金属拉压阻尼器,该阻尼器具有多级屈服和失效特性。基于Abaqus软件建立了该阻尼器的有限元模型,通过数值模拟探讨了阻尼器的力学性能。结果表明:该阻尼器滞回曲线饱满,且具有良好的耗能能力和变形能力,能够实现多级屈服的力学性能特点,其恢复力模型与模拟结果吻合较好。

塑性材料拉伸时加载速率对屈服强度影响的分析研究

通过对塑性材料在常温下进行不同加载速率的拉伸试验,分析加载速率与材料屈服强度之间的关系,并通过最小二乘法拟合、指数函数拟合、对数函数拟合、幂函数拟合和拉格朗日插值拟合进行加载速率与材料屈服强度之间的曲线拟合。曲线拟合结果表明:屈服强度关于加载速率增加而增大,屈服强度从最小值283.67KPa,增大至303Kpa,增大值所占比例为6.38%~6.81%;六阶曲线拟合图最能反映屈服强度与加载速率的关系。

基于流变学研究外用半固体制剂质量等同性的应用进展

皮肤外用半固体制剂包括乳膏剂、软膏剂、凝胶剂等剂型,含乳化剂、防腐剂、增稠剂或软化剂等多种辅料,可以是单相体系,也可以是包含连续相和分散相的多相体系,其处方设计、生产工艺复杂。流变学可以综合反映产品中物质分布、聚集状态等微观结构差别,是该剂型的关键质量属性,且与体外释放、体外渗透、稳定性、感官感受等其他项目存在关联性,是评价仿制药与原研药质量一致性最有效的手段之一。本文通过查阅国内外文献以及相应的政策法规要求,介绍流变学研究现状和测试方法,分析影响流变学特性的相关因素,探讨流变学参数所体现出的质量差别,指导制药厂家对处方和工艺进行改进,以期为该类制剂的开发和质量等同性研究提供帮助。

Applications of an IS-MP Model with Yield Curve

This paper interest rates （i.e., the recent macroeconomic presents an IS-MP model with the term structure of yield curve） and discusses some of its applications to activities and policy issues. Specifically, the model is employed to explain （1） why a steepening yield curve may signal the subsequent economic expansion, （2） why long-term zero interest rate policy （ZIRP） may not completely avoid recessions, but disables the yield curve from being inverted to signal the following economic recession, （3） how Operation Twist （OT） may help ease the recession, in particular, under ZIRP, and what limit it may face.