Emerging and Innovative Materials for Hydropower Engineering Applications:Turbines,Bearings,Sealing,Dams and Waterways,and Ocean Power

The hydropower sector is currently experiencing several technological developments.New technologies and practices are emerging to make hydropower more flexible and more sustainable.Novel materials have also been recently developed to increase performance,durability,and reliability;however,no systematic discussions can be found in the literature.Therefore,in this paper,novel materials for hydropower applications are presented,and their performance,advantages,and limitations are discussed.For example,composites can reduce the weight of steel equipment by 50%to 80%,polymers and superhydrophobic materials can reduce head losses by 4%to 20%,and novel bearing materials can reduce bearing wear by 6%.These improvements determine higher efficiencies,longer life span,waste reduction,and maintenance needs,although the initial cost of some materials is not yet competitive with respect to the costs of traditional materials.The novel materials are described here based on the following categories:novel materials for turbines,dams and waterways,bearings,seals,and ocean hydropower.

High Water Content Material Based on Ba-Bearing Sulphoaluminate Cement

A new type of high water content material which is made up of two pastes is prepared, one is refute from lime and gypsum, and another is based on Ba-bearing sulphoaluminate cement. It has excellent properties such as slow single paste solidifing ,fust double pustes solidifing ,fast coagulating and hardening, high early strength, good suspeasion property at high W/C ratio and low cost. Meanwhile, the properties and hydration mechanism of the material were analyzed by using XRD, DTA- TG and SEM. The hydrated products of new type of high water content material are Ba-bearing ettringite, BaSO4 , aluminum gel and C-S-H gel.

Application and mechanism of Fenton-like iron-based functional materials for arsenite removal

Between the two major arsenic-containing salts in natural water, arsenite(As(Ⅲ)) is far more harmful to human and the environment than arsenate(As(V)) due to its high toxicity and transportability. Therefore, preoxidation of As(Ⅲ) to As(V) is considered to be an effective means to reduce the toxicity of arsenic and to promote the removal efficiency of arsenic. Due to their high catalytic activity and arsenic affinity, iron-based functional materials can quickly oxidize As(Ⅲ) to As(V) in heterogeneous Fenton-like systems, and then remove As(V) from water through adsorption and surface coprecipitation. In this review, the effects of different iron-based functional materials such as zero-valent iron and iron(hydroxy) oxides on arsenic removal are compared, and the catalytic oxidation mechanism of As(Ⅲ) in heterogeneous Fenton process is further clarified. Finally, the main challenges and opportunities faced by iron-based As(Ⅲ) oxidation functional materials are prospected.

In vitro evaluation of a new resilient, hard-carbon, thin-film coating as a bearing material for ventricular assist devices ——In Vitro Bearing Evaluation of BioMedFlex

Our aim was to evaluate the potential use of BioMedFlex? (BMF), a new resilient, hard-carbon, thin- film coating, as a blood journal bearing material in Cleveland Heart’s continuous-flow left and right ven- tricular assist devices (VADs). BMF is not classified as a diamond-like carbon (DLC) and differs from other thin-film carbon coatings by its high flexural strength, radiopacity, and wear resistance. A 2- to 4-μm-thick BMF adhesion layer was deposited on the VAD journal bearing surfaces. A commercial DLC coating used in other clinical blood pump applications was used as a control. Durability and reliability of the BMF coating was verified in severe pump start/stop testing using 20 BMF-coated journal bearing pairs. The BMF-coated surfaces showed no coating failures, whereas 57% of the DLC bearing pairs developed scratches through the carbon coating, documenting that BMF can provide a durable coating in our blood journal bearing application. In conclusion, BMF has shown qualities that support its significant advantages as an alternative journal bea- ring material in Cleveland Heart pumps. Our plan includes biocompatibility testing with ongoing animal studies, endurance testing with submerged pumps running in saline, and assessment of batch coating processing capability.

Isotope Geochemical Characteristics and Material Sources of Tin--Bearing Porphyries in South China

Tin-bearing porphyries in South China can be divided into the F-rich and F-poorsubtypes. They are high-silica (SiO_2>71%), peraluminous (A/NKC>1.0) and rich inincompatible elements (Rb, Zr, U, W, Sn) and have weak Ce (δCe=0.68-0.82) and strong Eu(δEu=0.01-0.38) negative anomalies. Meantime, they also have low δ_(Nd)(-6.3- -8.4), high^(207)Pb/^(204)Pb (15.588-15.790), medium to high (^(87)Sr/^(86)Sr)_i (0.7084-0.7287) and relatively highδ^(18)O(9.1-10.3‰). These characteristics clearly suggest that the two subtypes of tin-bearingporphyries were derived from the crustal materials. Their differences lie only in the existence ofcertain different components in their source materials. Therefore, there is only one type oftin-bearing prophyry in South China. that is continental crust transformation type.

Key parameters for low temperature warm compaction of high density iron-based P/M materials

In order to reduce powder temperature to lower than 100℃ in warm compaction by changing polymer lubricant design, powder flowability, warm compacting behavior, lubricating mode as well as ultimate tensile strength after sinter-hardening and tempering were investigated systematically. By means of low temperature warm pressing and sintered hardening technique, samples with the sintered densities of 7.407.45g/cm3 and the strengths of 950 1390MPa are achieved as the early compacting pressure is 686735MPa.

Effect of Alternation of Aging and Seawater Erosion on Properties of Rubber Material Used in Lead Rubber Bearing

An artificially accelerated alternation of aging and seawater erosion test of rubber materials used in lead rubber bearing(LRB)was performed,mainly to study the time-varying laws of rubber materials mechanical properties.Time-varying laws of the Mooney–Rivlin and Neo-Hookean constitutive parameters of rubber materials under the alternation of aging and seawater erosion were also analyzed.Results indicate that the rubber material mechanical properties were significantly affected by alternation of aging and seawater erosion.Hardness and elongation stress increased exponentially with test time.And 120 days after the test,the hardness increased by 14%,the maximum percentage increase in stress of 124.76%occurred at 100%constant elongation and the minimum percentage increase in stress of 68.32%occurred at 300%constant elongation;Tensile strength and elongation at break decreased by 44.96%and 53.09%.Besides,constitutive parameters of Mooney–Rivlin and Neo-Hookean all changed greatly with test duration.Finally,time-varying laws of constitutive parameters were verified by comparing the simulated and experimental results of the lead rubber bearing’s stiffness.Research results are of great significance to the seismic performance research and life-cycle performance analysis of offshore traffic engineering such as cross-sea bridges and bridges in the marine environment.

Experimental Study of Moso Bamboo to-Steel Connections with Embedded Grouting Materials

Moso bamboos have attracted excessive attention as a renewable green building material to the concept of sustainable development.In this paper,the 20 bolted Moso bamboo connection specimens with embedded steel plates and grouting materials were designed according to connection configurations with different bolt diameters and end distance of bolt holes,and their bearing capacities and failure modes were analyzed by static tension tests.According to the test results of all connectors,the failure modes of the specimens are divided into four categories,and the effects of bolt diameter and bolt hole end distance on the connection bearing capacity and failure mode are analyzed.The test results show that the deformation and failure process can be divided into four stages.The main influence factor of connector bearing capacity is bolt diameter.Connectors can be divided into four failure modes,and brittle failure can be avoided by adopting certain structural measures.Filling with grouting material can improve the bearing capacity of joints.Due to the large variability of bamboo,further experiments are needed.

Optimization of a digested sludge-derived mesoporous material as an efficient and stable heterogeneous catalyst for the photo-Fenton reaction

The anaerobic digestion of sludge has recently received increased interest because of the potential to transform organic matter into methane‐rich biogas. However, digested sludge, the residue produced in that process, still contains high levels of heavy metals and other harmful substances that might make traditional disposal difficult. We have devised a facile method of converting digested sludge into a mesoporous material that acts as an effective and stable heterogeneous catalyst for the photo‐Fenton reaction. A comparison of the removal of rhodamine B under different conditions showed that FAS‐1‐350, which was synthesized by mixing the digested sludge with a 1 mol/L（NH4）2Fe（SO4）2 solution followed by calcination at 350 °C, exhibited the best catalytic activity owing to its faster reaction rate and lower degree of Fe leaching. The results indicate that Fe^（2＋）‐loaded catalysts have significant potential to act as stable and efficient heterogeneous promoters for the photo‐Fenton reaction, with better performance than Fe^3＋‐loaded catalysts because the Fe（II）/Fe（III）compounds formed in the calcination process are necessary to sustain the Fenton reaction. This protocol provides an alternative, environmentally friendly method of reusing digested sludge and demonstrates an easily synthesized mesoporous material that effectively degrades azo dyes.

An Overview of Performance Characteristics, Experiencesand Trends of Aerospace Engine Bearings Technologies

In this paper, the operating conditions, technical requirements, performance characteristics, design ideas, application experiences and development trends of aerospace engine bearings, including material technology, integration design and reliability, are reviewed. The development history of aerospace engine bearing is recalled briefly at first. Then today＇s material technologies and the high bearing performances of the bearings obtained through the new materials are introduced, which play important roils in the aeroengine bearing developments. The integration design ideas and practices are explained to indicate its significant advantages and importance to the aerospace engine bearings. And the reliability of the shaft-bearing system is pointed out and treated as the key requirement with goals for both engine and bearing. Finally, as it is believed that the correct design comes from practice, the pre-qualification rig testing conducted by FAG Aerospace GmbH ＆ Co. KG is briefly illustrated as an example. All these lead to the development trends of aerospace engine bearings from different aspects.

MICROSTRUCTURE AND PROPERTIES OF HIGH BORON BEARING STEEL

High boron bearing steel, in which boron homogeneously distributed, wassuccessfully produced in the vacuum induction furnace. The microstructural observations of cast andhot rolled steels showed that the addition of titanium can eliminate the quantity of ferrous boridesprecipitated at the grain boundaries and break the net microstructure, as a result, its hotworkability is improved. The titanium boride TiB_2 homogeneously distributes in the matrix ofalpha-Fe. The parameters of hot rolling process, including preheated temperature, initial rollingtemperature, finished rolling temperature and the total deformation, have been optimized.

Axial response and material efficiency of tapered helical piles

Different techniques have been proposed to increase the bearing capacity of open-ended piles.Welding helices to the shaft and tapering the pile shaft could be used simultaneously to enhance the static and dynamic behaviors of these piles.This paper subjects the bearing capacity,stiffness,frictional behavior,and material efficiency of the tapered helical piles to scrutiny.Tapered helical piles are introduced herein as an alternative option to improve the material efficiency of hollow piles.Based on the Taguchi method,a series of experiments was designed and conducted.The axial responses of tapered helical piles are also investigated using finite element analyses.The results derived from loadedisplacement curves and strain gages are used to characterize the axial compression responses of tapered helical piles.The effects of tapered angle,helices diameter and helices distance are examined using dimensionless parameters,and the degree of contribution of these factors is calculated on each of the enumerated variables individually.Experimental results show that the shaft friction resistance of tapered helical piles increases continuously with the pile head settlement.Furthermore,the effect of tapered wall on the shaft friction resistance is more tangible at low stress levels.The results showed that the relative material efficiency factor of the optimum pile could be 2.5 times that of unoptimized pile with a similar quantity of material.

Role of Rare Earth in Low Sulphur Nb-Ti-Bearing Steel

The effect of rare earth on the microstructures, mechanical properties and inclu sions in low sulphur Nb-Ti-bearing steel were investigated. It is shown that t h e transverse yield point, the traverse tensile strength and elongation of testin g steels decrease initially and then rise with increasing content of rare earth. The impact energy values of the testing steels exhibit a contrary trend. Proper amount of rare earth in the steels can improve the anisotropy of impact toughne ss above -20 ℃ and it does not affect the type of microstructures which ar e st ill composed of ferrites and pearlites, but the pearlite amount increases. On one hand, rare earth cleans the molten steel and reduces the amount of inclusions; on the other hand, rare earth makes the inclusions spheroidizd, refi ned and dispersed, and thus improves the distribution of inclusions.

EFFECT OF SULFUR ON PROPERTIES OF BALL BEARING STEEL

5 heats of GCr15 bearing steel of different sulfur contents ranging from 0.009-0.092% （wt.）were smelted. The role of sulfur in bearing steel and its effect on contact fatigue properties andfracture toughness KICWere studied. It was shown that as the sulfur content increases the sulfur content dissolved in the steelsubstrate remains unchanged. The best contact fatigue property appears at the sulfur content of0.045% （wt.）, and the influence of sulfur content on the fracture toughness of bearing steel is notobvious. Finally, the mechanism of the role of sulfur was investigated.

MEASURING AND MODELING OF THE MECHANICAL PROPERTIES OF COMPOSITE BEARING PAD MADE OF PLASTIC MATRIX AND FINE BRONZE ELASTIC SPRINGS

The viscoelastic properties of the normal PTFE plastic and strengthened PTFEplastic for bearing pad are measured. The mechanical properties of the composite material forbearing pad, which is made of the aforementioned plastics as matrix reinforced by fine bronzeelastic springs, are modeled and relaxation modulus of the material are presented. The differencebetween these two kinds of PTFE is studied. The results show that the complex modulus of PTFEplastics for bearing pad is higher than that of normal PTFE plastics.

Modeling of Rolling Contact Friction of Ball Bearings at Elevated Temperature

In order to predict the rolling friction coefficient and analyze the effects of material compatibility on the friction coefficient at elevated temperature(from room temperature to 600℃),a theoretic computation model was developed based on bearing's elastic contact hysteresis and related material characteristic parameters.Some examples were carried out to verify the feasibility of the model.The research results show that the material compatibility has significant effects on rolling friction coefficient,especially the modulus of elasticity and the expansion coefficient of material,and results also show the rolling friction coefficient of the matched pair between GCr15 and Si3N4 is the smallest comparing with that between GCr15 and M50(or ASP-23,or GCr15) when making GCr15,M50,ASP-23,and Si3N4 materials as bearing's rolling balls and GCr15 material as bearing's inner and outer rings.Further research indicates that the working temperature also has played an important role in the rolling friction coefficient of the ball bearing,moreover,the friction coefficient of the matched pair of M50 and Si3N4 behaves most stably at elevated temperature.

Properties and Application of Iron-based Shape Memory Alloy

The properties of FeMnSiCrNi shape memory alloy were investigated. The results show that the best shape memory effect of Fe14Mn6Si9Cr5Ni alloy is 85%. The transformation amount of the ε→γ transformation is not complete after heating the alloy to 1000 K, As and Af points drop with increased transformation enthalpy (ΔH γ→ε ) by thermal cycling and increased prestrain. The alloy shows also good creep and stress relaxation resistance. In addition, the alloy having a tensile force of 20 kN and a sealing pressure of 6 MPa can satisfy requirements for possible industrial application on pipe joints.

Influence of phosphorus on iron-based friction material prepared directly vanadium-bearing titanomagnetite concentrates

In situ selective carbothermic reactions and vacuum sintering were used to prepare iron-based friction material directly vanadium-bearing titanomagnetite concentrates.Effects of phosphorus addition(0.05–0.20 wt.%)on the microstructure and properties of iron-based friction material were investigated.The results show that the addition of phosphorus improves the microstructure and properties of the material significantly.When phosphorus addition increases to 0.15 wt.%,the sintering densification is promoted and the number of lamellar pearlites increases.Therefore,the relative density,hardness and tribological properties of the material are greatly enhanced.Particularly,the friction coefficient decreases 0.58 to 0.43,and the wear rate reduces 1.829×10^(–7) to 0.694×10^(–7)cm^(3)J^(-1).The dominant wear mechanism of the material changes severe abrasive wear to mild oxidation wear accordingly.However,when phosphorus addition exceeds 0.15 wt.%,the matrix continuity and tribological properties of the material are deteriorated.Comprehensively,the optimal addition of phosphorus in the iron-based friction material is 0.15 wt.%.

Numerical simulation and experimental verification of a novel double-layered split die for high-pressure apparatus used for synthesizing superhard materials

Based on the principles of massive support and lateral support, a novel double-layered split die(DLSD) for high-pressure apparatus was designed to achieve a higher pressure-bearing capacity and larger sample cavity. The stress distributions of the DLSDs with different numbers of divided blocks were investigated by the finite element method and compared with the stress distributions of the conventional belt-type die(BTD). The results show that the cylinders and first-layer supporting rings of the DLSDs have dramatically smaller stresses than those of the BTD. In addition, increasing the number of divided blocks from 4 to 10 gradually increases the stress of the cylinder but has minimal influence on the stress of the supporting rings. The pressure-bearing capacities of the DLSDs with different numbers of divided blocks, especially with fewer blocks, are all remarkably higher than the pressure-bearing capacity of the BTD. The contrast experiments were also carried out to verify the simulated results. It is concluded that the pressure-bearing capacities of the DLSDs with 4 and 8 divided blocks are 1.58 and 1.45 times greater than that of the BTD. This work is rewarding for the commercial synthesis of high-quality, large-sized superhard materials using a double-layered split high-pressure die.

Endogenic Au-Ag polymetallic ore deposits and ore-bearing potentiality of strata

The problem of ore-bearing potentiality of the strata involves metallogenic theory and ore-search orientation.Studies of the spatial distribution of endogenic Au-Ag polymetallic ore deposits in North Hebei indicated that the strata in which ore deposits occurred range in age from Paleozoic,Proterozoic to Mesozoic.In addition the ore deposits are characterized as being strata-bound in nature.The arise and establishment of "extracting" viewpoint may be attributed to the following three reasons:1) influence by the idea of "ore-source bed";2) limitation of analytical techniques in the 1980s'(especially gold element);and 3) a small number of samples(sampling locations were mostly disturbed by mineralization).Studies have shown that ore-forming materials would most probably come from the deep interior of the Earth.Deep-seated ore-bearing materials including Au-Ag polymetals were brought to the shallow levels by way of mantle plume-mantle sub-plume-mantle branch structure multi-stage evolution,finally leading to the formation of ore deposits.