Effects of chromium on the corrosion and electrochemical behaviors of ultra high strength steels

The effects of chromium on the corrosion and the electrochemical behaviors of ultra high strength steels were studied by the salt spray test and electrochemical methods. The results show that ultra high strength steels remain martensite structures and have anodic dissolution characteristic with an increase of chromium content. There is no typical passive region on the polarization curves of an ultra high strength stainless steel, AerMet 100 steel, and 300M steel. However, chromium improves the corrosion resistance of the stainless steel remarkably. It has the slowest corrosion rate in the salt spray test, one order of magnitude less than that of AerMet 100 and 300M steels. With the increase of chromium content, the polarization resistance becomes larger, the corrosion potential shifts towards the positive direction with a value of 545 mV, and the corrosion current density decreases in electrochemical measures in 3.5wt% NaCl solutions. Because of the higher content of chromium, the ultra high strength stainless steel has a better corrosion resistance than AerMet 100 and 300M steels.

Mechanics Behavior of Ultra High Toughness Cementitious Composites after Freezing and Thawing

Mechanical behaviors of UHTCC after freezing and thawing were investigated,and compared with those of steel fiber reinforced concrete（SFRC）,air-entrained concrete（AEC） and ordinary concrete（OC）.Four point bending tests had been applied after different freezing-thawing cycles（0,50,100,150,200 and 300 cycles,respectively）.The results showed that residual flexural strength of UHTCC after 300 freezing-thawing cycles was 10.62 MPa（70% of no freezing thawing ones）,while 1.58 MPa（17% of no freezing thawing ones） for SFRC.Flexural toughness of UHTCC decreased by 17%,while 70% for SFRC comparatively.It has been demonstrated experimentally that UHTCC without any air-entraining agent could resist freezing-thawing and retain its high toughness characteristic in cold environment.Consequently,UHTCC could be put into practice for new-built or retrofit of infrastructures in cold regions.

Effect of Ultra High Pressure Processing on the Particle Characteristics of Lotus-seed Starch

In this paper, the time dependent effects of various pressure treatments on the characteristics of lotus-seed starch which was modified by ultra-high pressure （UHP） were investigated. The results showed that the polarization cross of lotus-seed starch granules was weakening gradually with increasing the treatment time, which indicated the termination of their ordered crystallite structures. The morphologies of granules were collapsed once the UHP was kept at 500 MPa for 60 minutes. The particle size analysis demonstrated that the granule size and distribution of lotus-seed starches increased as the treatment time was prolonged. X-ray diffraction studies showed that the intensity of the feature diffraction peaks of starch decreased and eventually disappeared with increasing the treatment time, and B-type transformation pattern was observed. The Fourier transform infrared spectra （FTIR） analysis of starch showed that the UHP is a physical modification processing because no new groups formed. The research showed that UHP processing at certain degree is capable to achieve the modification of lotus-seed starch. It is of significance for the deep processing of lotus-seed products.

Seismic performance of steel reinforced ultra high-strength concrete composite frame joints

To investigate the seismic performance of a composite frame comprised of steel reinforced ultra high-strength concrete （SRUHSC） columns and steel reinforced concrete （SRC） beams, six interior frame joint specimens were designed and tested under low cyclically lateral load. The effects of the axial load ratio and volumetric stirrup ratio were studied on the characteristics of the frame joint performance including crack pattern, failure mode, ductility, energy dissipation capacity, strength degradation and rigidity degradation. It was found that all joint specimens behaved in a ductile manner with flexural-shear failure in the joint core region while plastic hinges appeared at the beam ends. The ductility and energy absorption capacity of joints increased as the axial load ratio decreased and the volumetric stirIup ratio increased. The displacement ductility coefficient and equivalent damping coefficient of the joints fell between the corresponding coefficients of the steel reinforced concrete （SRC） frame joint and RC frame joint. The axial load ratio and volumetric stirrup ratio have less influence on the strength degradation and more influence on the stiffness degradation. The stiffness of the joint degrades more significantly for a low volumetric stirrup ratio and high axial load ratio. The characteristics obtained from the SRUHSC composite frame joint specimens with better seismic performance may be a useful reference in future engineering applications.

Flexural response of reinforced concrete beams strengthened with post-poured ultra high toughness cementitious composites layer

Four-point bending tests were conducted up to failure on eleven reinforced concrete (RC) beams and strengthening beams to study the effectiveness of externally pouring ultra high toughness cementitious composites (UHTCC) on improving the flexural behavior of existing RC beams.The strengthening materials included UHTCC and high strength grade concrete.The parameters,such as thickness and length of strengthening layer and reinforcement in post-poured layer,were analyzed.The flexural behavior,failure mode and crack propagation of composite beams were investigated.The test results show that the strengthening layer improves the cracking and ultimate load by increasing the cross section area.Introducing UHTCC material into strengthening not only improves the bearing capacity of the original specimens,but also disperses larger cracks in upper concrete into multiple tightly-spaced fine cracks,thus prolonging the appearance of harm surface cracks and increasing the durability of existing structures.Compared with post-poured concrete,UHTCC is more suitable for working together with reinforcement.The load?deflection plots obtained from three-dimensional finite-element model (FEM) analyses are compared with those obtained from the experimental results,and show close correlation.

PREPARATION OF MICROPOROUS ULTRA HIGH MOLECULAR WEIGHT POLYETHYLENE (UHMWPE) BY THERMALLY INDUCED PHASE SEPARATION OF A UHMWPE/LIQUID PARAFFIN MIXTURE

Ultra-high molecular weight polyethylene (UHMWPE) with a microporous structure was prepared via thermally induced phase separation (TIPS).Liquid paraffin (LP) was used as a diluent in the preparation of microporous UHMWPE. Small angle laser light scattering (SALLS) and differential scanning calorimetry (DSC) were used to determine the phase separation temperatures,i.e.the cloud points and the dynamic crystallization temperatures,respectively.It was found that the cloudI points were coincident with the cryst...

Uniaxial Compressive Properties of Ultra High Toughness Cementitious Composite

Uniaxial compression tests were conducted to characterize the main compressive performance of ultra high toughness cementitious composite （UHTCC） in terms of strength and toughness and to obtain its stress-strain relationships. The compressive strength investigated ranges from 30 MPa to 60 MPa. Complete stress-strain curves were directly obtained, and the strength indexes, including uniaxial compressive strength, compressive strain at peak stress, elastic modulus and Poisson＇s ratio, were calculated. The comparisons between UHTCC and matrix were also carried out to understand the fiber effect on the compressive strength indexes. Three dimensionless toughness indexes were calculated, which either represent its relative improvement in energy absorption capacity because of fiber addition or provide an indication of its behavior relative to a rigid-plastic material. Moreover, two new toughness indexes, which were named as post-crack deformation energy and equivalent compressive strength, were proposed and calculated with the aim at linking up the compressive toughness of UHTCC with the existing design concept of concrete. The failure mode was also given. The study production provides material characteristics for the practical engineering application of UHTCC.

STUDIES ON THE NATURE OF THE MACROMOLECULAR CONDENSED STATE OF "NASCENT" ULTRA HIGH MOLAR MASS POLYETHYLENE

Ultra high molar mass polyethylene(UHPE)powder as polymerized in a slurry process has been studied,in its nascent state,after recrystallization on rapid cooling from the melt and after hot compression molding to a film,by DSC,effect of annealing the recrystallized specimen at 120 similar to 130 degreesC,morphology by polarizing optical microscopy and small angle X-ray scattering.Based on the experimental results obtained the macromolecular condensed state of the nascent UHPE powder is a rare case of a multi-chain condensed state of non-interpenetrating chains,involving interlaced extended chain crystalline layers and relaxed parallel chain amorphous layers.On melting,a nematic rubbery state of nanometer size domain resulted.The nematic-isotropic transition temperature was judged from literature data to be at least 220 degreesC,possibly higher than 300 ℃,the exact temperature is however not sue because of chain degradation at such high temperatures.The recrystallization process from the melt is a crystallization from a nematic rubbery state.The drop of remelting peak temperature by 10 K of the specimen recrystallized from its melt as compared to the nascent state has its origin in the decrease both of the crystalline chain stem length and of the degree of crystallinity.The remelting peak temperature could be returned close to that of the nascent state by annealing at 120~130 ℃.

Ultra High Early Strength Self-compacting Mortar Based on Sulfoaluminate Cement and Silica Fume

The influences of silica fume and aluminum sulfate on hydration process of sulfoaluminate cement were carried out by ring flow, setting time, hydration heat, XRD and DTG analyses. In addition, mortar mixtures with different functional additives have been studied through compressive strength, flexural strength, volume stability at early age and porosity characterization tests. The results show that the addition of silica fume and aluminum sulfate reduces the fluidity and shortens the setting time of sulfoaluminate cement paste, promoting hydration process and increasing hydration products at early age. In the case of appropriate proportion of mortar, the inclusion of hydroxy propyl methyl cellulose, dispersible polypropylene fiber arid organic silicon kind of defoamer can control segregation and bleeding, improve mechanical strength and volume stability at early age, and modify the pore distribution of sulfoaluminate cement mortar, respectively. The sulfoaluminate cement mortar can carry out gravitational grouting in the absence of outside force, the compressive strength of 2 hours and 24 hours have reached 26 and 58 MPa respectively, and have good micro- expansion and tiny.pore distribution characterization.

THE STUDY ON MEASURING TECHNIQUE OF PARTIAL DISCHARGE IN GAS INSULATED SWITCHGEAR USING ULTRA HIGH FREQUENCY METHOD WITH EXTERNAL SENSORS

Objective In order to find early latent faults and prevent catastrophic failures, diagnosis of insulation condition by measuring technique of partial discharge(PD) in gas insulated switchgear (GIS) is applied in this paper, which is one of the most basic ways for diagnosis of insulation condition. Methods Ultra high frequency(UHF) PD detection method by using internal sensors has been proved efficient, because it may avoid the disturbance of corona, but the sensor installation of this method will be limited by the structure and operation condition of GIS. There are some of electromagnetic (E-M) waves leak from the place of insulation spacer, therefore, the external sensors UHF measuring PD technique is applied, which isn't limited by the operation condition of GIS. Results This paper analyzes propagated electromagnetic (E-M) waves of partial discharge pulse excited by using the finite-difference time-domain (FDTD) method. The signal collected at the outer point is more complex than that of the inner point, and the signals' amplitude of outer is about half of the inner, because it propagates through spacer and insulation slot. Set up UHF PD measuring system. The typical PD in 252kV GIS bus bar was measured using PD detection UHF technique with external sensors. Finally, compare the results of UHF measuring technique using external sensors with the results of FDTD method simulation and the traditional IEC60270 method detection. Conclusion The results of experiment shows that the UHF technique can realize the diagnosis of insulation condition, the results of FDTD method simulation and the result UHF method detection can demonstrate each other, which gives references to further researches and application for UHF PD measuring technique.

Direct tension and fracture resistance curves of ultra high performance marine composite materials

Fracture behavior is one of the most important,yet still little understood properties of ultra-high performance cementitious composites(UHPCC),a new marine structural engineering material. Research on the fracture and direct tension behavior of UHPCC was carried out.The constitution law of UHPCC was divided into three phases:pre-partial debonding,partial debonding,and pullout phases.A direct tension constitution law was constructed based on the proposed fiber reinforcing parameter as a function of fiber volume fraction,fiber diameter and length,and fiber bonding strength.With the definition of linear crack shape,the energy release rate of UHPCC was derived and the R-curve equation was calculated from this.Loading tests of UHPCC using a three-point bending beam with an initial notch were carried out.The predictions from the proposed R-curve were in good agreement with the test results, indicating that the proposed R-curve accurately describes the fracture resistance of UHPCC.Introduction of a fiber reinforcement parameter bridges the fracture property R-curve and micro-composites’ mechanics parameters together.This has laid the foundation for further research into fracture properties based on micro-mechanics.The proposed tension constitution law and R-curve can be references for future UHPCC fracture evaluation.

Seismic Behavior of Steel Reinforced Ultra High Strength Concrete Column and Reinforced Concrete Beam Connection

To investigate the seismic behavior of connections composed of steel reinforced ultra high strength concrete (SRUHSC) column and reinforced concrete (RC) beam, six interior strong-column-weak-beam connection specimens were tested subjected to reversal cyclic load. Effects of applied axial load ratio and volumetric stirrup ratio on ductility, energy dissipation capacity, strength degradation and rigidity degradation were discussed. It was found that all connection specimens failed in bending in a ductile manner with a beam plastic hinge. The ductility and energy dissipation capacity increased with the decrease of applied axial load ratio or increase of volumetric stirrup ratio. The displacement ductility coefficient and equivalent damping coefficient lay between those of steel reinforced ordinary concrete connection and those of reinforced concrete connection. The applied axial load ratio and volumetric stirrup ratio had less influence on the strength degradation and more influence on the stiffness degradation. The stiffness degraded sharply with the decrease of volumetric stirrup ratio or increase of applied axial load ratio. The experimental results indicate that SRUHSC column and RC beam connection exhibited better seismic performance and can provide reference for engineering application.

Research on the design of cold rolled ultra high strength sheet steel

This study researches cold rolled ultra high strength martensitic steel processed by water quenching. It is found that both the quenching and overageing temperatures greatly influence the mechanical properties of martensitic steel. A tensile strength of 1500 MPa can be obtained from 0.2% C-1.8% Mn steel by soaking at 840℃,quenching at 700℃ and overageing at 200℃ for several minutes. The continuous cooling transformation （CCT） diagram reveals that full martensite can be obtained at a cooling rate of 100℃/s or higher; and at a cooling rate of 3 - 10℃/s,austenite barely decomposes at 700℃. For steel with 0.2% carbon and less manganese, austenite decomposition occurs before it is cooled to 700℃ at a cooling rate of 3 - 10℃/s, which leads to lower tensile strength. It is possible to reduce the manganese content of the 1500 MPa martensitic steel by increasing the quenching temperature. To increase the quenching temperature,the control of flatness during water quenching becomes a major concern.

Freezing and Thawing Durability of Ultra High Strength Concrete

Resistance to freezing and thawing of two UHSC （ultra high strength concrete） mixtures was evaluated in accordance with ASTM C 666 Procedure A. The two mixtures （plain and fiber reinforced） were developed using materials local to southern New Mexico, USA. Three different curing regimens were investigated for the mixture with fibers and one curing regimen was studied for the mixture without fibers. All curing regimens included 24 h of ambient curing followed by four days of wet curing at 50 ℃, and then two days dry curing at 200 ℃. At an age of seven days, one batch of fiber reinforced specimens was air cured at ambient conditions for the following six days and then placed in a water bath at 4.4 ℃ for 24 h prior to initiating freezing and thawing cycles. The second batch was air cured from day seven to day 12, and then wet cured for one day at 23 ℃ prior to being placed in the 4.4 ℃ water bath. The final batch was wet cured at 23 ℃ from the seventh day to an age of 13 days and then placed in the 4.4 ℃ water bath. The mixture with no fibers was air cured from the seventh day to an age of 12 days and then wet cured for one day at 23 ℃ prior to being placed in the 4.4 ℃ water bath. Higher moisture levels during curing produced greater initial dynamic elastic modulus values and durability factors at the end of the freezing and thawing tests, with the greatest durability factor being 87.5. Steel fibers were observed to improve both compressive strength and durability factor for UHSC.

Analysis of Excitation Characteristics of Ultra High Frequency Electromagnetic Waves Induced by PD in GIS

The understanding of the excitation mechanism of ultra high frequency (UHF) electromagnetic waves (EW) is essential for ap- plying UHF method to partial discharge (PD) detection. Since the EW induced by PD in gas insulated switchgear (GIS) contains not only transverse electromagnetic (TEM) wave, but also high-order transverse electric (TE) and high-order transverse magnetic (TM) waves, we analyzed the proportions between the TEM wave and the high order waves, as well as the influence of the PD position on this proportion, using the finite different time domain (FDTD) method. According to the unique characteristics of the waves, they are separated only ap- proximately. It is found that the high-order mode is the main component, more than 70%, of the electric field around the enclosure of GIS, and that with the increasing distance between PD source and inner conductors, the low frequency ( below about 800 MHz) component of EW decreases, but the high frequency component (above 1 GHz) increases, meanwhile the proportion of high-order components in EW could reach 77% from 70%. It concluded that the closer the PD source to the enclosure is, the easier high order EW may be excited.

The Application of Ultra High Voltage in the World

With rapidly growth in industrial sectors, in order to meet the demand, the usage of Ultra High Voltage (UHV) is needed. High voltage (HV) is between the range of 52 kV and 300 kV. In case of voltage above 800 kV, it can be defined as UHV. With the development of technologies in the world, it could be seen that Japan, Russia, Italy, Brazil, America (U.S), and Canada began to improve UHV in the 1960s and 1970s. In addition, China, a leader developing country for UHV technologies in the world, started UHV technologies in transmission, in 1980s. Nowadays, seven transmission lines are in operation in China. In this study, the concept of HV and UHV will be introduced. Especially, UHV transmission in the worldwide will be researched. Then, the historical development and current situation of UHV will be analyzed and the assessment for Turkey will be done.

Evaluation of the Shear Strength of Perfobond Rib Connectors in Ultra High Performance Concrete

Since the previous strength prediction models for the perfobond rib connector were proposed based upon the results of push-out tests conducted on concretes with compressive strength below 50 MPa, push-out test is performed on perfobond shear connectors applying ultra high performance concretes with compressive strength higher than 80 MPa to evaluate their shear resistance. The test variables are chosen to be the diameter and number of dowel holes and, the change in the shear strength of the perfobond rib connector is examined with respect to the strength of two types of UHPC: steel fiber-reinforced concrete with compressive strength of 180 MPa and concrete without steel fiber with compressive strength of 80 MPa. The test results reveal that higher concrete strength and larger number of holes increased the shear strength, and that higher increase rate in the shear strength was achieved by the dowel action. The comparison with the predictions obtained by the previous models shows that the experimental results are close to the values given by the model proposed by Oguejiofor and Hosain [1].

Chemical Components of Achyranthes bidentata Leaves by Ultra High Performance Liquid Chromatography-Mass Spectrometry

[Objectives] To study the chemical components and relative content of Achyranthes bidentata leaves and provide a scientific basis for further development and utilization of A. bidentata leaves.[Methods] The chemical components of A. bidentata leaves were rapidly analyzed using the ultra high performance liquid chromatography-time of flight-high resolution mass spectrometry (UHPLC-TOF-MS).[Results] Thirty eight chemical compounds were identified in samples of A. bidentata leaves collected from Wen County of Henan Province, in which seven chemical compounds had the relative content higher than 5%, linoleic acid reached 25.7% and inokosterone A reached 13.8%.[Conclusions] A. bidentata leaves contain many kinds of chemical compounds. This study is expected to provide a certain basis for further extraction of linoleic acid and inokosterone A.

Seismic Performance of Steel Reinforced Ultra High-strength Concrete Columns

The seismic performance of steel reinforced ultra-high-strength concrete columns(SRSHC) with various shear-span ratios(λ) were studied through a series of experiments.The concrete compressive cube strength value of experimental specimens ranged from 92.9 MPa to 108.1 MPa.The main experimental variables affecting seismic performance of specimens were axial load ratio and stirrup reinforcement ratio.The columns(λ=2.75) subjected to low cyclic reversed lateral loads failed mainly in the flexural-shear mode failure and columns(λ≤2.0) subjected to low cyclic reversed lateral loads failed mainly in the shear mode failure.Shear force-displacement hysteretic curves and skeleton curves were drawn.Coefficient of the specimen displacement ductility was calculated.Experimental results indicate that ductility decreases with axial pressure ratio increasing,and increases with stirrup reinforcement ratio increasing.Limit values of axial pressure ratio and minimum stirrup reinforcement ratio of columns are proposed to satisfy definite ductility requirement.The suggested values provide a reference for engineering application and for the amendment of the current Chinese design code of steel reinforced concrete composite structures.

Three-Dimensional Analysis of Melanosomes Isolated from B16 Melanoma Cells by Using Ultra High Voltage Electron Microscopy

Melanosomes, isolated by centrifugal separation from culture broth of B16 melanoma cells derived from mouse, were observed by scanning electron microscopy (SEM), and by transmission electron microscopy (TEM). Some interesting structural features were found inside and outside of the melanosomes. By SEM observation, the melanosomes were ellipsoid shape, their surface was not smooth and was covered with rough substructure, 10 to 20 nm particles. By TEM, uneven structure and micro particles were observed in the melanosomes. Furthermore, three-dimensional analysis was tried by using the ultra-high voltage electron microscopy(UHVEM). Micrographs of the melanosomes were taken at various tilted angles by UHVEM, after preparing 500 nm thickness specimens stained with lead citrate. From the micrographs collected, the three-dimensional structures were reconstructed by using i-mode software. Melanin stained by lead and non stained parts was clearly observed in the reconstructed structure. Non stained parts were round, regular size, and distributed widely in the melanosomes.