EFFECT OF MICRO-GALLIUM ON THE INTERGRANULAR SEGREGATINN OF PHOSPHORUS IN CARBON STEELS

The effect of small amounts of gallium on the intergranular segregation of phosphorus in carbon steels is discussed, with the help of the impact test, fracture morphology and micro-structure analyses, combined with composition analysis on the fracture surfaces by Auger electronspectrometer. The results show that gallium in the steel with a content of gallium more than ten thou-sandth can suppress, to some extent, the intergranular segregation of phosphorus and retard the tempering process. As a result, the temper embrittlement of the steel disappears and the embrittlement transition temperature declines.     

Simulation and experiment for warp characteristic of wet multiple disc clutches

Based on the real size and constrain of the wet clutch, the friction pair of temperature, stress fields coupling model, and the heat convection coefficient model are established. The transient thermal-structural coupling and the thermoelastic instability of the phenomenon of friction discs generated in overload tests are numerically simulated and analyzed with ANSYS/LS-DYNA. Additionally, the distribution of the hot spots in the circle direction and surface of the friction discs are revealed, the distribution of the stress and strain caused by the thermoelastic instability is analyzed and tested. The results show that hot spots and contact pressure are mutual promotion. The thermal expansion and stress concentration caused by temperature gradient lead to steel disc warp. The heat fading caused by the thermoelastic instability leads to steel disc failure.     

Numerical Method for Load Bearing Capacity of High Strength Steel Columns at Elevated Temperature

In order to make fire resistance design of high strength steel columns in building structures, the numerical calculation method on load bearing capacity of high strength steel columns at elevated temperature was investigated. By taking the mechanical property of high strength steel at elevated temperature into consideration, extension was made on the inverse calculation segment length method and the program to compute the load bearing capacity of high strength steel columns at elevated temperature was performed. The program was adopted to compute the load bearing capacity. The results obtained by the program and the finite element analysis were compared and good agreement had been found. The influence of magnitude, distribution mode of residual stress and initial geometry imperfection on ultimate load bearing capacity was analyzed by employing the program. It is shown that the extended method can be is shown used to calculate the load bearing capacity of high strength steel columns at elevated temperature; the magnitude and distribution mode of residual stress had little influence but the geometry imperfection have significant influence on ultimate load bearing capacity.     

Thermo-mechanical coupling analysis of dual-steel-disc of wet multi-disk clutch

To solve the failure problem of power transmission caused by warping, crackle on dual-steel-disc of wet multi-disk clutch, a shipborne wet multi-disk clutch is taken as a research object, models of generation and distribution of friction heat flux are built and numerical methods to solve temperature field and coupled stress field are put forward. Research methods of thermo-mechanical coupling problem of wet multi-disk clutch are proposed. The thermo-mechanical coupling phenomenon of dual-steel-disc is investigated, and the failure mechanism of dual-steel-disc of wet multi-disk clutch is revealed. In the engagement process, the results of temperature field show that the temperature of the dual-steel-disc gradually increases from the inner edge to the outer edge, and the temperature of friction surface reaches the highest at 2.6 s in the 3-second-engagement. The rules of thermal stress distribution are attained that the circumferential tensile thermal stress appears in the region close to the inner edge, while the radial tensile thermal stress appears in the region close to the outer edge. The theoretical basis to solve the thermal failure problem of dual-steel-disc of wet multi-disk clutch is provided.     

轴心受压钢构件高温下局部稳定设计方法

为了得到钢构件高温下局部稳定设计方法,通过试验对建立的有限元模型进行了验证。采用验证后的有限元模型,分析了温度、板件宽厚比、初始几何缺陷、腹板和翼缘相互作用等因素对H形截面轴心受压钢构件局部屈曲应力的影响,提出了Q235钢和Q460钢H形截面轴心受压构件高温下的局部稳定承载力简化计算公式和高温下防止局部屈曲的翼缘宽厚比和腹板高厚比限值。研究表明：当板件宽厚比较小时,构件的局部屈曲应力随宽厚比的增大迅速减小,宽厚比较大时,构件屈曲应力降低不明显;初始几何缺陷对构件局部屈曲应力影响较小;高温下翼缘对腹板屈曲的约束作用比常温下明显;高温下防止局部屈曲的宽厚比限值与常温下宽厚比限值不同。     

Fire-resistance performance of high-strength-steel H shaped columns under the axial compression

In order to investigate the fire-resistance performance of high-strength-steel column,this paper deduces the critical stress of high-strength-steel columns under the axial compression at high temperature by introducing the mechanical properties of high-strength-steel at high temperature.Moreover,coefficients of overall stability and critical temperature for high-strength-steel column under the axial compression are obtained which can provide a reference for design.The comparison of overall stability coefficient and critical temperature between high-strength-steel and normal steel is made.The results show that the overall stability coefficient and critical temperature for normal steel is not applicable for high-strength-steel,and the overall stability coefficient for high-strength-steel is smaller than that for normal steel.The paper uses the finite element analysis to validate the overall stability coefficient,and good match was found between them.     

A New Method for Measuring Bonding Shear Properties of Adhesives on Steel Substrates

Single-lap-joint adhesively bonded metal specimen which is the national standard experimental method in use has an extremely non-uniform distribution of shear stresses along the joint, and tensile stress concentration of high values is produced on the steel substrate interfaces. Therefore the test result, which is not the real bonding shear strength between adhesive and steel substrates, can only be used as a test index for qualities of adhesives not the strength criterion for load is capacity evaluation. The combined bonding disc specimen is adopted for measuring bonding shear properties of adhesive on steel substrates, has a very uniform distribution of shear stresses in adhesive and along the bonding surfaces of steel substrates, of which the uniform coefficient is greater than 0.97. Furthermore, when adhesive joint is treated as an arc and steel substrates are chamfered at both ends of the joint, tensile stresses on the bonding surfaces can be reduced to less than 20 MPa which can hardly cause tensile failure. Thus, the results of combined bonding disc specimens can actually represent the real bonding shear strength or bonding shear-compression strength between adhesive and steel substrates, which can be used as strength criterion for load capacity evaluation of bonding members.     

Temperature Filed Ansys Simulation in QuenchingProcess of 45 Teel Part

Nonlinear thermophysics parameters are considered in ansys finite element software, so it can be used to compute temperature in the quenching. The temperature field in quenching process of 45 steel part is simulated by ansys finite element software, and the relationship between temperature of part and quenching time is obtained. Simulation result is correspondent with real process, this method has quick computing speed, and it can optimize quenching technology and select quenching bath. The most of all,this method can supply the temperature condition in computation of thermal stress and residual stress of quenching process.     

Numerical simulation for the residual stress of U-rib welding onto the flat steel box girder

The flat steel box girder is commonly used for long-span cable-stayed bridges. the structural complexity, construction details and manufactures cause damage to the bridge and the damages seriously grow overtime. The main reason for these damages is that welding technology of flat steel box girder with thin plates and rib elements produces residual stress and strain fields during the welding process, and further more welding cracks commonly appear. In this study, thermal-structural couple methods was adopted to numerically simulate the welding high temperature fields and the stress fields at the joint of U rid and decks of a flat steel box. The welding residual stress distribution was studied as well for further analyzing on the structural damage and strengthening design strategies.     

Integration Strategy for Thermal-Elastic-Plastic Models of Concrete under Plane Stress

Plastic strain was determined at multiple time increments.The strain was caused by stress and temperature.The yield function in high-temperature states is the function of temperature and plastic strain.The calculation efficiency would be decreased and much more calculation would be needed if a conventional method,such as the radial return method,was used.In the case of axial stress states,the temperature path was difficult to determine at various time intervals.Initial value equations were obtained with the Drucker-Prager function of plane stress concrete.This method can solve the previously mentioned problems efficiently when used with the Runge-Kutta integration strategy.A program was developed with an updated co-varying coordinate finite element method based on the S-R decomposition theorem.Computational results show that the integration strategy is highly accurate and efficient.     

棉花种间BC_1群体偏分离的遗传剖析(英文)

偏分离是指观察到的基因型频率偏离预期的孟德尔频率的遗传分离方式,在大多数的遗传定位研究中非常普遍。在之前我们发表的遗传连锁图中,107个SSR标记在BC1作图群体[(Emian 22×3-79)×Emian22]中表现偏分离。为阐明这些偏分离标记的遗传机制及其在其它群体中的偏分离情况,将其中97个共显性标记在另外两个回交群体中进行验证。结果表明,原图谱中的61个偏分离标记在另外2个回交群体中都表现正常分离,说明杂交方式是导致偏分离的一个重要因素。36个偏分离标记至少在两个群体中仍表现偏分离,偏分离应该是配子选择的结果。偏分离标记分布于14条染色体上,其中D亚基因组上的分布多于A亚基因组。偏分离标记在在第2、第16和第18染色体上分布最多,暗示在这些染色体上存在偏分离位点,该结果有助于在棉花中鉴定偏分离位点。     

THE EFFECTS OF HEAT CONDUCTING CROSS-SECTION AREA AND AXIAL HEAT CONDUCTION ON THE HEAT TRANSFER IN THE TUBE-MOUTH REGION OF THE HIGH TEMPERATURE HEAT EXCHANGE EQUIPMENT

In this paper the heat transfer in the tube-mouth region of the high temperatur heat exchange equipment is deeply analysed. The effect; of the heat conducting cross-section area of the tube-mouth region and axial heat conduction along the tube on the temperature field is emphatically examined by numerical computation, and then the relation of the highest temperature in the tube with the elongated tube length is established. The computed results in this paper are compared with those without taking account of these two factors. It is shown that the effect can not be ignored for the corrosion-protection by controlling temperature.     

Assessment of Groundnut under Combined Heat and Drought Stress

In semi‐arid regions, particularly in the Sahel, water and high‐temperature stress are serious constraints for groundnut production. Understanding of combined effects of heat and drought on physiological traits, yield and its attributes is of special significance for improving groundnut productivity. Two hundred and sixty‐eight groundnut genotypes were evaluated in four trials under both intermittent drought and fully irrigated conditions, two of the trial being exposed to moderate temperature, while the two other trials were exposed to high temperature. The objectives were to analyse the component of the genetic variance and their interactions with water treatment, year and environment (temperature) for agronomic characteristics, to select genotypes with high pod yield under hot‐ and moderate‐temperature conditions, or both, and to identify traits conferring heat and/or drought tolerance. Strong effects of water treatment (Trt), genotype (G) and genotype‐by‐treatment (GxTrt) interaction were observed for pod yield (Py), haulm yield (Hy) and harvest index (HI). The pod yield decrease caused by drought stress was 72 % at high temperature and 55 % at moderate temperature. Pod yield under well‐watered (WW) conditions did not decrease under high‐temperature conditions. Haulm yield decrease caused by water stress (WS) was 34 % at high temperature and 42 % under moderate temperature. Haulm yield tended to increase under high temperature, especially in one season. A significant year effect and genotype‐by‐environment interaction (GxE) effect were also observed for the three traits under WW and WS treatments. The GGE biplots confirmed these large interactions and indicated that high yielding genotypes under moderate temperature were different to those at high temperature. However, several genotypes with relatively high yield across years and temperature environments could be identified under both WW and WS conditions. Correlation analysis between pod weight and traits measured during plant growth showed that the partition rate, that is, the proportion of dry matter partitioned into pods, was contributing in heat and drought tolerance and could be a reliable selection criterion for groundnut breeding programme. Groundnut sensitivity to high‐temperature stress was in part related to the sensitivity of reproduction.     

contact stress and steady thermal analysis of herringbone gears in a gas turbine

To obtain the distribution characteristic of contact stress and the bulk temperature on the surface of herringbone gears, parameter modeling of gears was carried out by parametric design language. A numerical simulation was given to calculate the contact stress field and the steady thermal field by combining heat transfer theory, tribology theory, and mesh theory. The distribution of contact stress, the bulk temperature and heat flux also were analyzed. The analysis results show that the distribution of the load along the contact line possesses regularity. The heat flux along the tooth depth direction decreases first and then increases. The effect of thermal conduction of the tooth is stronger than that of convective heat transfer. The conclusion indicates that the finite element emulation method can be used to estimate the transmission performance of herringbone gears.     

Finite Element Method of 3D Stable Heat Conduction of Steel Fluid in Continuous Casting Moulds

The heat transfer of steel fluid in continuous casting mould is a stable process and can be depicted with three-dimensional stable heat conduction equation depending on tension speed. The corresponding finite element equation, including the first, second and third boundary conditions, is deduced out with Galerkin residual method. The coded FEM program is used to analyze the temperature distribution of Q235 steel in continuous billet casting mould. The method proposed is a foundation of thermo-mechanical coupled analysis for the formation of solidified shells and stress in the shells in continuous casting.     

Experimental Analysis on Shear Strengthening Capacity of Secondary Dapped end Beams

Because section steel can only be extended to the edge of the support, when a simple support RC beam is reinforced by bonded section steel, a notch comes into being at the end of the beam which is called a secondary dapped end beam, making the stress state of the beam more complex. Through experimental analysis on 21 dapped end beam specimens shear reinforced by steel plate bonded, the deformation process, performing characteristics and failure mechanism of the specimens were investigated. The result shows that two steel bonded forms, including horizontal steel plate and oblique steel plate with angle 45° bonded, delay the appearance of cracks significantly and improve the maximum bearing capacity by 102% and 93%. Due to the impact of stress concentration at the notch, the main modes of damage include concrete tensile or shear failure with the result of bonding failure of a steel plate. By changing the width of steel plates and analyzing different reinforcement effects, formula of bearing capacity of shear reinforcement was proposed based on the method of truss analogue, which provides a reference for engineering application.     

稻谷仓壁材料摩擦系数的实验研究

利用土工合成材料综合测定仪测定了不同法向压应力（25 kPa、50 kPa、100kPa、150 kPa、200 kPa）下稻谷（水分含量为13.55%、15.14%、17.00%、19.19%w.b）与不同仓壁材料（不锈钢板、混凝土板、木板）的摩擦系数。结果表明：稻谷与不锈钢板摩擦系数较小,与混凝土板和木板的摩擦系数较大;随着法向压应力的增大,稻谷与各仓壁材料的摩擦系数均呈不同幅度的减小;随着水分的增大,稻谷与各仓壁材料的摩擦系数增大。根据实验结果,可拟合出摩擦系数与法向压应力、水分含量的关系方程。     

A SIMPLIFIED PLASTIC ZONE METHOD FORSECON DORDER ELASTICPLASTIC ANALYSISOF STEEL FRAMES

This paper presents a simplified plastic zone method with consideration of the in-fluences of the PDelta. residual stress ,degradation of crosssectional stiffness and plastic zone lengthon the stiffness matrix for second-order elastic-plastic analysis of steel frames. The method not onlymakes up for a insufficiency which is that the degradation of crosssectional stiffness and plasticzone length in a member ean not be considered by a plastic hinge method but also overcomes a defectwhich is very costly and time-consuming because a fine mesh discretization across the crosssectionand along the member length is required by a plastic zone methed. Analysis result Shows proposedsimplified rnethod is simple and practical.     

高温胁迫对水稻光合PSII系统伤害及其与叶绿体D1蛋白间关系

以水稻结实期的人工控温试验测定不同温度处理下水稻旗叶光合速率、叶绿素荧光参数的动态变化,并结合Western印迹与胶体金标记技术对叶肉细胞类囊体膜中D1蛋白的表达检测与活性定位,探讨了高温胁迫对D1蛋白存在形态与活性分布的影响,以及D1蛋白表达与叶片光合速率、PSII荧光参数的联系。结果表明,高温处理下叶片净光合速率下降、PSII潜在活性(F_v/F_o)和PSII光能转化效率(F_v/F_m)降低,且随着高温胁迫时间的持续和叶片功能的衰退,类囊体膜结构损伤越严重,光能转化效率越低;在D1蛋白的两类存在形态中,非磷酸化D1蛋白和磷酸化D1蛋白在高温胁迫下的表达量均有所下降,但前者下降更明显;高温处理下控制D1蛋白表达的叶绿体psbA基因在转录水平呈下调表达,使D1蛋白合成及周转过程受到抑制,进而类囊体膜PSII反应中心的功能受损与叶绿体光合效率下降,揭示高温胁迫对叶片PSII系统的伤害受D1蛋白磷酸化过程和psbA基因表达变化的共同作用,进而影响不同水稻品种在高温胁迫下的光合速率和耐热性。     

植物低温胁迫调控机制研究进展

低温是影响植物生长发育和植被分布的一种非生物胁迫。当环境温度持续低于植物生长的最佳温度时即形成低温胁迫,包括冷害和冻害。冷害是指零度及以上低温对植物造成的伤害,细胞内不结冰,但会使喜温类植物产生生理性障碍,引起该类植物受伤或死亡。冻害是指零度以下低温对细胞造成损伤甚至死亡的现象。植物从感知低温到功能基因表达,进而抵御低温胁迫,相关调控机制一直是研究热点。本文综述了近年来植物低温胁迫相关研究,从信号感知、信号传导、功能基因表达、低温诱导的生理和细胞调机制等几个方面进行了分析讨论,并对植物抗寒研究做出展望,这将有助于抗寒植物新种质的培育。