Critical Submergence for a Rectangular Intake

In this study, the critical submergence for a rectangular intake in a uniform canal flow is investigated. The potential solution for the combination of a line sink and a uniform flow is available and known as Rankine half-body. This study is based on the Rankine half-body. Theoretical and experimental results have indicated that, in general, the critical submergence for a rectangular intake can be predicted by means of a critical sink surface which consists of a critical cylindrical sink surface capped with two critical hemispherical sink surfaces at both ends. The effects of intake-duct pipe blockage and location of impervious boundaries on critical submergence of a rectangular intake are presented. Experiments were conducted on a rectangular intake sited in a dead-end uniform canal flow. The agreement between the theoretical and experimental results is found to be acceptable.     

Critical Submergence for Multiple Pipe Intakes

The critical submergence for a group of multiple pipe intakes is predicted using a “superposition method” based on a potential flow solution. Experiments on groups of two, three, and four intakes were conducted. Experimental and theoretical results indicate that intakes in a group mutually influence the discharge into an individual intake. Therefore, the critical submergence for an intake in a group becomes larger than that for an isolated intake under identical flow conditions. The agreement between the theoretical and experimental results is found to be satisfactory.     

Prediction of Critical Submergence for a Rectangular Intake

The effects of the blockage of a rectangular intake duct and impervious flow boundaries on the critical submergence of a rectangular intake are presented. The potential solution, based on the Rankine stagnation point, is determined to be another approximate method for the prediction of the critical submergence of this kind of intake. It is found that a critical cylindrical sink surface capped with two critical hemispherical sink surfaces at both ends with a radius equal to the radial distance of the stagnation point (which is 2/π times the critical submergence of the rectangular intake) can also be used to predict critical submergence. Theoretical results and available experimental data are compared. The theory presented in this study acceptably (by about 1–20%) estimates the critical submergence for the cases where the distance (clearances) of the impervious solid boundaries are larger than 1/2 of the small inner dimension of the intake. On the other hand, the theory overestimates the critical submergence by about 80% for the cases where the distances of the solid boundaries (especially those cutting the free surface such as the dead-end wall) become zero.     

钢管高速超声检测信号传输的关键技术研究

为提高钢管高速超声波检测系统中信号传输的质量和系统性能,对接触式及非接触式二类传输方式进行对比分析。总结了压电超声激励及回波信号特点,分析了目前主要采用的信号耦合技术的结构及工作原理,并在特性参数、技术特点、制造成本等方面进行相互对比,为设计应用提供了依据。     

Effects of Consolidation History on Critical State of Sand

A series of drained biaxial compression tests were conducted on two sands to determine the effects of consolidation history on their critical states. Specimens of each sand were consolidated along at least two separate paths in void ratio-effective stress space, creating several unique consolidation histories. Because the sands were dilative, strains localized during shearing and the evolution to critical state occurred only within the shear band. Digital images were obtained through a plexiglass sidewall throughout each test. Digital image correlation techniques were used to quantify the displacements within the band, and a linear regression technique was used to formulate a displacement function from which strains were computed. The critical state was achieved within the shear band in each test, but the critical state line was found to depend on the initial state and subsequent consolidation history of the sand specimens.     

Effects of the Presence of Others on Food Intake: A Normative Interpretation.

The authors review the effect of the presence of others on food intake. In social facilitation studies, people tend to eat more in groups than when alone. In modeling studies, the presence of others may facilitate or inhibit intake, depending on how much these other people eat. Studies of impression management demonstrate that people tend to eat less in the presence of others than when alone. The authors attempt to reconcile these divergent literatures by reference to a model of inhibitory norms that govern eating. In the presence of palatable food, and in the absence of clear signals of satiety, people look outward to cues from the environment to determine when to stop eating. Socially derived inhibitory norms can account for either increased or decreased intake in the presence of others, depending on how much the others eat and the extent to which one is eager to impress them. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Large Eddy Simulations of the Effects of EMBr and SEN Submergence Depth on Turbulent Flow in the Mold Region of a Steel Caster

Transient turbulent flow in the mold region during continuous casting of steel is related to many quality problems, such as surface defects and slag entrainment. This work applies an efficient multi-GPU based code, CUFlow, to perform large eddy simulations (LES) of the turbulent flow in a domain that includes the slide gate, SEN, and mold region. The computations were first validated by comparing the predicted surface velocity with plant measurements. Then, seven LES simulations were conducted to study the effects of casting speed, electromagnetic braking (EMBr) field strength, and submerged entry nozzle (SEN) depth on the transient flow. The results show that EMBr has an important influence on flow inside the SEN, in addition to flow in the mold. With EMBr, an “M-shaped” flow profile is seen inside the SEN. The swirling flow behavior in the SEN and ports is more symmetrical at high casting speed and with higher EMBr strength. The position of the SEN ports relative to the peak magnetic field affects the EMBr performance. The results confirm and quantify how applying EMBr greatly lowers both the magnitude and turbulent variations of the surface velocity and level profile.     

Cyclic Critical Stress States of Sand with Nonfrictional Effects

New observations of experimental facts are made in this study to understand the physical essentials regarding the changes in mobilized maximum stress and phase-transformation stress states of saturated sands subjected to cyclic undrained shear applications. Saturated sands are not purely frictional materials that are governed only by frictional law (i.e., the shear-normal stress ratio). They are also characterized by the following effects of nonfrictional behavior: (1) Irreversible dilatancy effect; (2) viscous effect at large strain rate; and (3) coupling effect of viscous to frictional resistance. It was found that the first effect reduces the limiting shear resistance, whereas the second and third effects increase it. Based on this finding, 2D and 3D criteria that consider both the frictional and nonfrictional effects are developed by introducing several new concepts such as the “true effective stress,” “moving stress space,” and “moving spatially mobilized plane.” Their effectiveness is confirmed experimentally.     

Effects of Heat-Affected Zone Microstructure on Fracture Toughness of Two X70 Pipe Girth Welds

In the previous study, unstable brittle crack extensions were observed during ductile tearing from all the single-edge notched bend [SE(B)] specimens with an initial crack placed in heat-affected zone (HAZ), machined from one of the two studied X70 pipe girth welds, performed at 258 K (?15 °C). Thus their microstructures and properties have been investigated using optical microscopy, microhardness measurement, and advanced scanning electron microscopy and transmission electron microscopy so as to (1) characterize their metallographic properties including crystallographic texture and (2) correlate them with the unstable brittle crack occurrence and propagation. The results suggest that HAZ softening—strength loss—is a major factor responsible for the cleavage occurrence in the given HAZ specimens as it could induce a large local strain concentration by limiting plasticity in base metal when a ductile crack crosses from the HAZ to the base metal. The HAZ softening seems to be associated with the disappearance of pearlite packets in the HAZ region, which presumably occurred during welding, for the given material. High angle grain boundaries in the fine-grained HAZ appear to affect the direction of cleavage propagation at the point of cleavage initiation (i.e., pop-in).     

加热温度对X70钢原始奥氏体晶粒尺寸的影响

对X70管线钢的原始奥氏体晶粒尺寸随加热温度的变化情况进行了研究,结果表明,随着加热温度的升高,原始奥氏体晶粒尺寸逐渐增大,并在1 200℃附近出现粗大晶粒,而钢中的铌在1 150℃左右已基本固溶,由此对此种管线钢在控轧控冷工艺中加热温度的选择进行了探讨。     

玛钢水暖件电镀锌

以CT-2为光亮剂的氯化钾电镀锌在玛钢水暖件上施镀时,其电流效率为95%,镀层光亮细致,其耐蚀性与低碳钢上的镀锌层相近,证明水暧件原材料的成分及其铸态表面缺陷对电镀锌的质量无显著影响,但电镀锌与热浸锌相比可大大降低锌和能量单耗,降低成本,可用电镀锌来代替现行的热浸锌。     

管路刚度对精轧机液压回油管振动影响的研究

分析了某钢厂5000mm精轧机立辊液压回油管振动问题,考虑使用改变管路的刚度来解决振动问题,并使用ANSYS CFX软件对这段液压回油管路的一截进行了分析,进行了现场测试,通过仿真和测试共同验证改变管路刚度可以有效地减少回油管振动。     

Hydraulics of Bottom Rack Intake

Bottom racks are a standard hydraulic structure used as intakes in mountainous regions, to divert water to turbines, and to retain sediment and other solid matter larger than rack spacing. These racks are also used for fish ways, and to retain floating matter. The present project was directed to explore the hydraulics of bottom rack intakes, without considering any solids in the fluid. Based on extended laboratory observations, the effect of various parameters were explored, such as the bottom slope, the rack geometry, and the rack porosity. In addition, a novel approach to determine the discharge coefficient of a rack structure was developed. Finally, the intake channel below the bottom rack was investigated and several interesting features were found, including a significant flow instability that may have a strongly adverse effect on the rack performance. Guidelines for successful rack designs are given, and the results of the present study may be readily applied.     

Effects of Hydrogen on the Critical Conditions for Dynamic Recrystallization of Titanium Alloy During Hot Deformation

Hot deformation tests were performed to study the flow behavior and microstructural evolution of a Ti600 titanium alloy with different hydrogen contents. The effects of hydrogen on the critical conditions for the initiation of dynamic recrystallization (DRX) were investigated. The DRX kinetics models of hydrogenated Ti600 alloy were developed, and the DRX volume fractions were quantified under different deformation conditions. The results indicate that the addition of proper hydrogen (no greater than 0.3 pct) benefits the decrease of both the critical stress and critical strain for the initiation of DRX. The critical stress and critical strain are dependent linearly on the peak stress and the strain to peak stress, respectively. The strain range from the initiation to the completion of DRX increases gradually with hydrogen in the hydrogen range of 0 to 0.3 pct, and a slightly decreased strain range is observed at the hydrogen content of 0.5 pct relative to that of 0.3 pct. The addition of large amounts of hydrogen (0.3 pct or greater) in Ti600 alloy induces incomplete DRX during hot deformation.     

采用离心浇铸空心管坯生产不锈钢管工艺研究

通过对离心浇铸不锈钢空心管坯的浇铸温度、浇钢时间、铸模转速、钢水浇完至脱模时间的探索及合理控制,成功地离心浇铸了1Cr18Ni9Ti空心管坯;并重点对离心浇注空心坯与轧制管坯的挤压力及其检验结果进行了对比分析,阐明了采用“离心浇铸管坯＋热挤压或＋冷轧”新工艺生产不锈钢管的可行性和优势。     

钢塑复合管在宝钢给水主管线的应用研究

分析了宝钢各个生产、建设阶段钢塑复合管在埋地给水主管线的应用情况及主要问题;对钢塑复合管的制造工艺、技术、应用场合进行了阐述,并指出了实际应用中应关注的重点、要点;同时,亦对钢塑复合管中钢管的内表面处理及应用的标准做了提炼、归纳。     

Effects of Velocity Head and Momentum Exchange on Critical Stable Sectional Area of Downstream Throttled Surge Tank

The velocity head and momentum exchange at the T-junction between the surge tank with a riser and the tail water tunnel of hydroelectric powerplants have been introduced by using the Gardel’s head-loss formula. The effects of the velocity head and momentum exchange on the critical sectional area of the downstream tank have been analyzed. With Thoma’s assumption, the critical stable sectional area of the downstream throttled surge tank is derived theoretically. The study shows that the velocity head has an unfavorable effect on water level stability in the downstream surge tank while the effect of the momentum exchange is positive. These two effects counteract. Thus, the critical sectional area of a downstream throttled surge tank is close to that of a corresponding simple surge tank. However, if the size and shape of a riser are optimized, the area of the downstream surge tank may be further reduced. It is also demonstrated that a downstream throttled surge tank can reduce electricity loss and easily meet the requirements of stability in large flow oscillations when compared to a simple downstream tank.     

Investigation on Mechanical Property of Seamless Pipe

The mechanical properties of the steel pipe rolled with continuously casting round billet after determining the chemical composition in steel were studied. The results show that the total reduction ratio should be higher than 5.2 when the line pipes of grade B, grade 20 and other general seamless pipe were rolled with continuously casting round billet. And the total reduction ratio should be higher than 10.2 and the grain size should be controlled more than grade 7 for casing of oil countryside tubular goods (OCTG).