Hot Results Research Articles

Hydrogen effect on compression mechanical properties of TiNb alloys at elevated temperatures

The study of this work was focused on the hydrogen effect on hot deformation behavior of hydrogen charged TiNb based alloys at three temperatures in comparison with non-charged specimens. The Ti24Nb and Ti26Nb (at.%) alloys were heat treated by three step regime in argon or hydrogen atmospheres. The hot compression tests were performed on a Gleeble 3800 machine at 800, 750 and 700°C with compression strain of 5×10-3 s-1 and deformation degree of 50 %. The microstructure resulting from heat treatment as well as from isothermal compression test was analyzed using optical and scanning electron microscopies. Measurement of microhardness revealed that higher microhardness values for Ti24Nb after thermo-hydrogen treatment corresponded to fine grained microstructure and strengthening by grain boundaries. Hydrogen contents determined using LECO RH600 analyzer showed that Ti26Nb contained higher amount of hydrogen due to the stabilization of beta phase by higher Nb concentration. Based on the hot compression test results, the plasticity at elevated temperatures was evaluated. The evolution of uniaxial compressive test curves showed the stabilization of flow stress due to the hydrogen for high deformations at lower temperatures. The differences in hot compression behavior for both niobium contents on the one hand and for hydrogen charged and non-charged specimens on the other hand were observed.

The Influence of Thermal Expansion of Unbonded Foundry Sands on the Deformation of Resin Bonded Cores

AbstractDepending on the preparation and the applied materials, moulds and cores can be of high rigidity or can be flexible. Although, chemically bonded moulding materials have relatively good flexibility, their high temperature behaviour determines the dimensional accuracy, the stresses in the castings and can induce several casting defects, such as rattail, veining, etc. The phenomenon is based on two major effects: the thermal expansion of the unbonded foundry sands and the deformation of the sand mixtures. The main objective of the present work was to study the relationship between these two effects, and to improve the knowledge related to the thermo-mechanical interactions between the casting and the mould. Dilatometric analysis of unbonded sand samples were performed and compared to the results of hot distortion tests of moulding mixture specimens. The results showed, that the thermal expansion of foundry sand largely influences the hot distortion behaviour, but depending on the type of binder used.

AC2BS합금의 열간 균열강도 및 인장특성에 미치는 스크랩 함량의 영향

The effects of scrap content on the hot tearing property and tensile property were investigated in AC2BS alloy. The hot tearing strengths were <TEX>$16.4kgf/cm^2$</TEX>, <TEX>$15.2kgf/cm^2$</TEX>, <TEX>$14.9kgf/cm^2$</TEX> and <TEX>$13.3kgf/cm^2$</TEX>, respectively, under the constant solid fraction of 29.3% when the scrap contents of the specimens were 0%, 20%, 35% and 50%. In the same way, tensile strengths of the as-cast condition were <TEX>$24.5kgf/mm^2$</TEX>, <TEX>$23.7kgf/mm^2$</TEX>, <TEX>$17.3kgf/mm^2$</TEX> and <TEX>$16.0kgf/mm^2$</TEX>, respectively, and the corresponding tensile strengths of the T6 heat treatment condition were <TEX>$27.2kgf/mm^2$</TEX>, <TEX>$26.7kgf/mm^2$</TEX>, <TEX>$24.2kgf/mm^2$</TEX> and <TEX>$23.9kgf/mm^2$</TEX>. Hot tearing strength and tensile strength decreased as scrap content of the specimen increased. According to the evaluation of the quantitative hot tearing and tensile test results, the decrease of these strengths is due to the presence of oxide films which act as crack initiation site of the specimens. Therefore, elimination of oxide films of aluminum melt to maintain melt cleanliness is required.

Development of a new TBC system for more efficient gas turbine engine application

To protect the superalloy blades in industrial gas turbine engines from failure Atmospheric plasma-sprayed YSZ (yttria-stabilized zirconia) thermal barrier coatings (TBCs) are widely used. The spalling of YSZ coating is the main failure of TBCs. This failure usually occurs within the YSZ coating near the YSZ/bond coat interface. In the present feasibility study, a novel durable multilayer TBC was fabricated using atmospheric plasma spray (APS) on Ni718 superalloy substrate consisting of a NiCrAlY-20%YSZ- MoSi2 top coat. The developed system introduces a protective top layer of MoSi2 for preventing diffusion of oxygen, oxidation of the bond coating, provides thermal insulation and protection against corrosion and high temperature erosion. The results of hot gas flow exposure test (H2+O2) to the triple layered coating, a kinetic heating study, showed that a decreased temperature 400 °C for heating of 145 second achieved without any visible damage or delamination in such drastic combustion condition exposure even after 27 cycles of such repeated exposure.

Diffraction Radiation Oscillator with Asymmetric Open Resonant System. Part 2. Hot Test Results of Diffraction Radiation Oscillator

Diffraction Radiation Oscillator with Asymmetric Open Resonant System. Part 2. Hot Test Results of Diffraction Radiation Oscillator

터빈 매니폴드 모사장치를 이용한 액체로켓엔진 가스발생기 연소시험

개방형 사이클의 액체로켓엔진에서는 추진제 중 일부를 연소시켜 터빈 구동용 가스를 생성시키는 가스발생기가 사용되며, 개방형 사이클 액체로켓엔진의 주요 구성품으로서 가스발생기 자체의 연소성능 및 특성을 파악하기 위한 연소시험이 요구된다. 하지만, 가스발생기에서 생성된 연소가스는 터빈 매니폴드의 터빈 노즐에서 질식이 이루어지기 때문에 가스발생기뿐만 아니라 터빈 매니폴드 내부 부피를 고려해야만 가스발생기의 연소 성능 및 특성, 그리고 음향 특성을 정확히 파악할 수 있다. 따라서, 본 논문에서는 터빈 매니폴드 모사장치를 이용한 가스발생기 연소시험 결과를 기술하고 가스발생기 단독 연소시험 결과를 이용한 특성 예측을 설명한다. A gas generator which generates turbine driving gas by burning a part of propellants is used in an open cycle liquid rocket engine and as a main component of an open cycle liquid rocket engine autonomous hot firing tests are required to investigate the combustion performance and characteristics of the gas generator. However, since the combustion gas generated by a gas generator is choked at the turbine nozzle in the turbine manifold, it is necessary to consider the internal volume of turbine manifold as well as that of the gas generator for correct investigation of the combustion performance, characteristics, and acoustic characteristics of the gas generator. Therefore, in the paper hot firing test results of a gas generator with a turbine manifold simulator are described and characteristic prediction using the autonomous test of a gas generator is explained.

Exploration of Analgesic Activity of the Ethanolic Extract of Erythrina variegate Bark.

The aim of this study was to evaluate analgesic activity of the ethanolic extract of the bark of Erythrina variegata . The analgesic potential of the extract was evaluated using acetic acid-induced writhing test for peripheral analgesic activity and tail immersion, hot plate, formalin and glutamate test at 50, 100, and 200 mg/kg body weight doses. In analgesic activity tests, the extract at the doses of 50, 100, and 200 mg/kg b.w. produced a remarkable increase in pain threshold in a dose dependent manner. In acetic acid induced writhing test, the inhibitory effect was to be parallel to the reference drug diclofenac sodium. The extract showed 18.89% writhing inhibitory effect at the dose 200 mg/kg b.w., whereas diclofenac sodium showed 79.42% inhibition of writhing at a dose of 10 mg/kg b.w. The results of tail immersion and hot plate test also showed potential analgesic activity of the extract which is also comparable to the standard drug morphine (5 mg/kg b.w.). In formalin test, the bark extract at doses 200 mg/kg b.w. were found to exhibit the highest 47.80% inhibitory effect in late phase, whereas the reference drug morphine showed 63.64% inhibitory effect on licking of the hind paw. In glutamate test, the bark extract at doses 200 mg/kg b.w. were found to exhibit the highest 68.07% inhibitory effect in late phase, whereas the reference drug diclofenac sodium showed 61.53% inhibitory effect on licking of the hind paw. In conclusion, it can be said that the plant part have potential analgesic activity and may be used to relief pain.

Results of hot tests of an oxygen preburner of a liquid-propellant engine 11D58MF

In this article results of LRE 11D58MF oxygen preburner development are considered. Preburner consist of two zones. In the first zone fuel is burned, in the second zone combustion products are mixed with the rest of oxygen. There were 39 hot test on five preburners performed. Tests were conducted with variable chamber pressure, propellant mixture and initial temperature of gas oxygen. Evaluation of temperature field distribution and uniformity in outer section was performed. Mean temperature of combustion products on the exit section of preburner, obtained from test results, agreed well with theoretical calculations. Operational stability of preburner with various input parameters is confirmed. Design of injection elements and fuel input chamber were improved on order to assure reliability of preburner. Ignition and stop sequence instructions were formulated. Theres need to test three more preburners to complete individual development test series.

Investigation on Properties and Microstructure in Hot Stamping Operation of Rear Axle Beams

In the automotive industry, the hot forming of high strength steels offers the possibility to obtain significant reduction of weight without affecting the structural performances of final products. The main reason of its restricted application in the industry lies however in the lack of basic knowledge about mechanical and microstructural characteristics of sheets at elevated temperature, boundary conditions, and other process parameters. To partially overcome this limitation, this paper presents a research on the material properties of the hot stamping steel 22MnB5. Sheets of boron steel 22MnB5 with a thickness of 3.8mm were investigated and the results of experimental hot stamping tests were considered. The yield strength (YS) reached about 1200MPa, tensile strength (TS) reached 1500MPa, microhardness reached over 450HV at heating temperature of 880°C and holding 5 min.

Efectos neurotóxicos de la levobupivacaína y el fentanilo sobre la médula espinal de ratones

BackgroundThe purpose of the study was to compare the neurotoxic effects of intrathecally administered levobupivacaine, fentanyl and their mixture on rat spinal cord. MethodsIn experiment, there were 4 groups with medication and a control group. Rats were injected 15μL saline or fentanyl 0.0005μg/15μL, levobupivacaine 0.25%/15μL and fentanyl 0.0005μg+levobupivacaine 0.25%/15μL intrathecally for four days. Hot plate test was performed to assess neurologic function after each injection at 5th, 30th and 60thmin. Five days after last lumbal injection, spinal cord sections between the T5 and T6 vertebral levels were obtained for histologic analysis. A score based on subjective assessment of number of eosinophilic neurons –red neuron– which means irreversible neuronal degeneration. They reflect the approximate number of degenerating neurons present in the affected neuroanatomic areas as follows: 1, none; 2, 1–20%; 3, 21–40%; 4, 41–60%; and 5, 61–100% dead neurons. An overall neuropathologic score was calculated for each rat by summating the pathologic scores for all spinal cord areas examined. ResultsIn the results of hot plate test, comparing the control group, analgesic latency statistically prolonged for all 4 groups.In neuropathologic investment, the fentanyl and fentanyl+levobupivacaine groups have statistically significant high degenerative neuron counts than control and saline groups. ConclusionsThese results suggest that, when administered intrathecally in rats, fentanyl and levobupivacaine behave similar for analgesic action, but fentanyl may be neurotoxic for spinal cord. There was no significant degeneration with levobupivacaine, but fentanyl group has had significant degeneration.

Molecular docking and analgesic studies of Erythrina variegata׳s derived phytochemicals with COX enzymes.

Secondary metabolites from plants are a good source for the NSAID drug development. We studied the analgesic activity of ethanolic extract of Erythrina variegata L. (Fabaceae) followed by molecular docking analysis. The analgesic activity of Erythrina variegata L. is evaluated by various methods viz., acetic acid-induced writhing test, hot plate and tail immersion test. Subsequently, molecular docking analysis has been performed to identify compounds having activity against COX-1 and COX-2 enzymes by using GOLD docking fitness. The result of preliminary phytochemical screening revealed that the extract contains alkaloids and flavonoids. In analgesic activity tests, the extract at the doses of 50, 100 and 200 mg/kg body weight (b.w.) produced a increase in pain threshold in a dose dependent manner. In acetic acid induced writhing test, the inhibitory effect was similar to the reference drug diclofenac sodium. The extract showed 18.89% writhing inhibitory effect at the dose 200 mg/kg b.w., whereas diclofenac sodium showed 79.42% inhibition of writhing at a dose of 10 mg/kg b.w. The results of tail immersion and hot plate test also showed potential analgesic activity of the extract which is also comparable to the standard drug morphine (5 mg/kg b.w.). Docking studies shows that phaseollin of Erythrina variegata L. has the best fitness score against the COX-1 which is 56.64 and 59.63 for COX- 2 enzyme. Phaseollin of Erythrina variegata L. detected with significant fitness score and hydrogen bonding against COX-1 and COX-2 is reported for further validation.

Performance study of protective clothing against hot water splashes: from bench scale test to instrumented manikin test.

Hot liquid hazards existing in work environments are shown to be a considerable risk for industrial workers. In this study, the predicted protection from fabric was assessed by a modified hot liquid splash tester. In these tests, conditions with and without an air spacer were applied. The protective performance of a garment exposed to hot water spray was investigated by a spray manikin evaluation system. Three-dimensional body scanning technique was used to characterize the air gap size between the protective clothing and the manikin skin. The relationship between bench scale test and manikin test was discussed and the regression model was established to predict the overall percentage of skin burn while wearing protective clothing. The results demonstrated strong correlations between bench scale test and manikin test. Based on these studies, the overall performance of protective clothing against hot water spray can be estimated on the basis of the results of the bench scale hot water splashes test and the information of air gap size entrapped in clothing. The findings provide effective guides for the design and material selection while developing high performance protective clothing.

Design and Experimental Study of a High-Gain W-Band Gyro-TWT With Nonuniform Periodic Dielectric Loaded Waveguide

Gyrotron traveling wave tubes (gyro-TWTs) are of considerable interest for high-power millimeter and submillimeter radiation sources. The analytical design and experiment of a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">W</i> -band gyro-TWT loaded with nonuniform periodic lossy dielectric rings is presented in this paper. The gyro-TWT is operating in the circular TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> mode at the fundamental cyclotron harmonic, and driven by a 60 kV, 8-A gyrating electron beam with velocity ratio 1.2. Hot test results were: 1) maximum peak output power 112 kW; 2) 69.7-dB saturated gain; and 3) 23.3% efficiency at 93.5 GHz. The measured bandwidth with peak power greater than 90 kW is about 4 GHz in the range of 93–97 GHz. The hot test results show excellent agreement with the theoretical prediction. The potential backward wave oscillations involving the spurious modes TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> , TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sub> , and TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">02</sub> are effectively suppressed by the nonuniformly loaded periodic lossy dielectric rings. The <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">W</i> -band gyro-TWT is zero-drive stable at the operating points. It demonstrates that a nonuniform loaded lossy dielectric structure is excellent for suppressing potential spurious oscillations.

Preliminary test results of anuclear pressurized thermal hydraulictesting facility.

In this work, the main features of a nuclear pressurizedthermal hydraulic testing facility named BKTF (BK testing facility) are presented. The facility consists of major systems and components similar to the standard PWR prototype, and it is a volume and pressure scaled model with the total mass of primary coolant in order of hundreds of kilograms. The model is designed to work at normal temperature and pressure less than 160 0C and 10 bars respectively. In this part of research, preliminary results of cold test and hot test are presented. These results show that the system is qualified enough to work under designed pressure and temperature. It is seen that the similarity between temperature and pressure trend lines with these from a real power system during starting up process. In addition, natural circulation was appreciated and compared with forced circulation during the cooling down process and this may help us to have a better vision on passive safety and completely recognize about safety system of nuclear power plant.

Application of annular centrifugal contactors in the hot test of the improved total partitioning process for high level liquid waste

High level liquid waste (HLLW) produced from the reprocessing of the spent nuclear fuel still contains moderate amounts of uranium, transuranium (TRU) actinides, 90Sr, 137Cs, etc., and thus constitutes a permanent hazard to the environment. The partitioning and transmutation (P&T) strategy has increasingly attracted interest for the safe treatment and disposal of HLLW, in which the partitioning of HLLW is one of the critical technical issues. An improved total partitioning process, including a TRPO (tri-alkylphosphine oxide) process for the removal of actinides, a CESE (crown ether strontium extraction) process for the removal of Sr, and a CECE (calixcrown ether cesium extraction) process for the removal of Cs, has been developed to treat Chinese HLLW. A 160-hour hot test of the improved total partitioning process was carried out using 72-stage 10-mm-dia annular centrifugal contactors (ACCs) and genuine HLLW. The hot test results showed that the average DFs of total α activity, Sr and Cs were 3.57×103, 2.25×104 and 1.68×104 after the hot test reached equilibrium, respectively. During the hot test, 72-stage 10-mm-dia ACCs worked stable, continuously with no stage failing or interruption of the operation.

Design of beam-wave interaction based on high efficiency of a high-power broadband klystron

The paper mainly presents the design of beam-wave interaction of a C-band high-peak-power high-efficiency broadband klystron. The beam-wave interaction section is designed based on considerations of efficiency and bandwidth synthetically. As a part of beam-wave interaction section, buncher section is simulated by Particle-In-Cell (PIC) code to observe the bunching process of electron beam to achieve high conversion efficiency of electron beam and RF field. When it comes to the other part, output circuit is designed as a three-section filter by an output cavity loaded with Chebyshev filter, and the cold test results are given. The beam-wave interaction is simulated by EGUN code and Arsenal-MSU code respectively. The simulated results indicated that, the existence of power dips in the operating bandwidth is verified by Arsenal-MSU code, comparing proper results by EGUN code. Then, the method that design parameters are not adjusted except parameters of buncher cavities to remove potential power dips is described. What is more, the simulated results of electron optics system are given by EGUN code and Arsenal-MSU code respectively. The further hot test results of klystron prove that the whole design of beam-wave interaction is effective.

Design and multi-physical properties of a new insulating concrete using sunflower stem aggregates and eco-friendly binders

In the interests of sustainable development, building materials using lignocellulosic aggregates like hemp concretes are more and more used in green construction. This type of concrete made of plant aggregates has particularly attractive thermal and hygroscopic properties. The hemp produced by agricultural holdings represents 10,000 ha in France whereas sunflower production is about 700,000 ha. The purpose of the article is to bring scientific elements which demonstrate that aggregates from the sunflower stem can be valorised in the same way as hemp hurd for the manufacturing of building materials. This study could encourage the development of new outlets for agricultural crops. Moreover, the sunflower aggregates could be available at low costs and promote a local economy as compared to hemp hurd. The experimental program includes the physical and thermal characterisation of the raw materials and the design of concrete where aggregates, obtained from an industrial grinding process, are associated with a binder. The characterisation of the aggregates mainly consists of the granulometric study by image analysis, the water absorption and the determination of thermal properties using especially the hot wire method. Two binders are used to prepare cylindrical specimens of sunflower concrete. Two kinds of mixture are tested in compression after 60 days, in thermal conductivity and capillary water absorption. The first one, called wall mixture, has a binder on aggregates mass ratio of 2 (B/A = 2) and the second mixture, called roof mixture, has a B/A mass ratio of 1. Hot wire test results demonstrate for the wall mixtures an average dry thermal conductivity of 0.096 ± 0.003 W m−1 K−1 for the two binders. Compression results show an average compressive strength value at 60 days of 0.50 ± 0.1 MPa for the wall mixtures and 0.10 ± 0.01 MPa for the roof mixtures after an average 17 % strain. The results obviously show that the sunflower concrete reaches thermal and mechanical properties very close from those of hemp concrete. The capillary absorption test confirms the high absorbent potential of the sunflower aggregates but also the role of the binder towards the water uptake behaviour of lignocellulosic concretes.

Identification and characterization of classical complement pathway inhibitors and their application to in vivo and ex vivo disease models

In this paper a set of mechanism-based unified elastic–viscoplastic constitutive equations has been used to model the mechanisms of plastic flow softening for the two-phase titanium alloy Ti-6Al-4V in hot forming conditions. Globularisation of the secondary (lamellar) alpha phase, dislocation density, plastic deformation induced temperature increase and phase transformation during deformation have been modelled. Hot compression tests were conducted on Ti-6Al-4V samples at different temperatures in a range of 1093 K–1293 K and at different strain rates in the range of 0.1 s−1–10 s−1. The material parameters were determined by using the hot compression test results and by using an Evolutionary Programming (EP)-based optimisation method. Based on the set of constitutive equations, stress–strain relationships for Ti-6Al-4V at different temperatures and strain rates were predicted. Good agreements between the experimental and computed results were obtained in steady state hot forming deformation conditions.

Hot corrosion tests on corrosion resistant coatings developed for gas turbines burning biomass and waste derived fuel gases

This paper reports on results of hot corrosion tests carried out on silicon–aluminide coatings developed for hot components of gas turbines burning biomass and waste derived fuel gases. The corrosion tests of the silicon–aluminide coatings, applied to superalloys IN738LC and CMSX-4, each consisted of five 100h periods; at 700°C for the type II tests and at 900°C for the type I tests. Deposits of Cd+ alkali and Pb+ alkali were applied before each exposure. These deposits had been previously identified as being trace species produced from gasification of biomass containing fuels which after combustion had the potential to initiate hot corrosion in a gas turbine. Additionally, gases were supplied to the furnace to simulate the atmosphere anticipated post-combustion of these biomass derived fuel gases. Results of the type I hot corrosion tests showed that these novel coatings remained in the incubation stage for at least 300h, after which some of the coating entered propagation. Mass change results for the first 100h confirmed this early incubation stage. For the type II hot corrosion tests, differences occurred in oxidation and sulphidation rates between the two substrates; the incubation stages for CMSX-4 samples continued for all but the Cd+ alkali high salt flux samples, whereas, for IN738LC, all samples exhibited consistent incubation rates. Following both the type I and type II corrosion tests, assessments using BSE/EDX results and XRD analysis confirmed that there has to be remnant coating, sufficient to grow a protective scale.In this study, the novel silicon–aluminide coating development was based on coating technology originally evolved for gas turbines burning natural gas and fossil fuel oils. So in this paper comparisons of performance have been made with three commercially available coatings; a CoCrAlY overlay, a platinum-aluminide diffusion, and triple layer nickel–aluminide/silicon–aluminide-diffusion coatings. These comparisons showed that the novel single-step silicon–aluminide coatings provide equal or superior type II hot corrosion resistance to the best of the commercial coatings.

Cold cracking tests—an overview of present technologies and applications

Hot crack prevention in materials production and processing is an essential prerequisite for welded component safety. The causes of hot cracking can ultimately be attributed to the occurrence of metallurgical effects and to structural loads. More than 140 hot cracking test procedures have hitherto been developed for determining the hot cracking resistance. In principle, they are divided in self-restraint and externally loaded hot cracking tests with diverse process variants. Only some of the hot cracking tests are international standardized. Although various factors are known that encourage or prevent hot cracking, it is often not possible even with defined welding conditions to draw immediate conclusions about the hot cracking resistance of a welded component alone from a metallurgical composition of the base and filler materials. Based on an evaluation of the existing theories relating to hot cracking susceptibility assessment, this study summarizes the major hot cracking test procedures and highlights the application limits of the test procedures by presenting overviews along with explanations. It shows that weld hot cracking tests can generally be used to rank materials, welding consumables, and welding conditions. The evaluation of hot cracking test results and of their transferability among one another and to real components always requires consideration of the close relationships between metallurgy, welding process, and parameters, respectively, and prevailing restraint conditions.