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Sample records for 20-l continuously stirred

  1. Continuous-flow stirred-tank reactor 20-L demonstration test: Final report

    Energy Technology Data Exchange (ETDEWEB)

    Lee, D.D.; Collins, J.L.

    2000-02-01

    One of the proposed methods of removing the cesium, strontium, and transuranics from the radioactive waste storage tanks at Savannah River is the small-tank tetraphenylborate (TPB) precipitation process. A two-reactor-in-series (15-L working volume each) continuous-flow stirred-tank reactor (CSTR) system was designed, constructed, and installed in a hot cell to test the Savannah River process. The system also includes two cross-flow filtration systems to concentrate and wash the slurry produced in the process, which contains the bulk of radioactivity from the supernatant processed through the system. Installation, operational readiness reviews, and system preparation and testing were completed. The first test using the filtration systems, two CSTRs, and the slurry concentration system was conducted over a 61-h period with design removal of Cs, Sr, and U achieved. With the successful completion of Test 1a, the following tests, 1b and 1c, were not required.

  2. Evaluation of the Small-Tank Tetraphenylborate Process Using a Bench-Scale, 20-L Continuous Stirred Tank Reactor System at Oak Ridge National Laboratory: Results of Test 5

    Energy Technology Data Exchange (ETDEWEB)

    Lee, D.D.

    2001-08-30

    The goal of the Savannah River Salt Waste Processing Program (SPP) is to evaluate the presently available technologies and select the most effective approach for treatment of high-level waste salt solutions currently stored in underground tanks at the U.S. Department of Energy's Savannah River Site in Aiken, South Carolina. One of the three technologies currently being developed for this application is the Small-Tank Tetraphenylborate Process (STTP). This process uses sodium tetraphenylborate (TPB) to precipitate and remove radioactive cesium from the waste and monosodium titanate (MST) to sorb and remove radioactive strontium and actinides. Oak Ridge National Laboratory is demonstrating this process at the 1:4000 scale using a 20-L-capacity continuous-flow stirred-tank reactor (CSTR) system. Since March 1999, five operating campaigns of the 20-L CSTR have been conducted. The ultimate goal is to verify that this process, under certain extremes of operating conditions, can meet the minimum treatment criteria necessary for processing and disposing of the salt waste at the Savannah River Saltstone Facility. The waste acceptance criteria (WAC) for {sup 137}Cs, {sup 90}Sr, and total alpha nuclides are <40 nCi/g, <40 nCi/g, and <18 nCi/g, respectively. However, to allow for changes in process conditions, the SPP is seeking a level of treatment that is about 50% of the WAC. The bounding separation goals for {sup 137}Cs and {sup 90}Sr are to obtain decontamination factors (DFs) of 40,000 (99.998% removal) and 26 (96.15% removal), respectively. (DF is mathematically defined as the concentration of contaminant in the waste feed divided by the concentration of contaminant in the effluent stream.)

  3. Nonequilibrium chemical instabilities in continuous flow stirred tank reactors: The effect of stirring

    Science.gov (United States)

    Horsthemke, W.; Hannon, L.

    1984-11-01

    We present a stochastic model for stirred chemical reactors. In the limiting case of practical interest, i.e., fast stirring, we solve for the characteristic function in steady state and derive expressions for the stationary moments through a perturbation expansion. Moments are explicitly calculated for a generic model of bistable behavior. We find that stirring decreases the area of the bistable region essentially by changing the point of transition from the high reaction rate state to the low reaction rate state. This is in remarkable agreement with the experimental findings of Roux, et al. Our results indicate that stirring should not be considered simply as an ``enhanced diffusion'' process and that nucleation plays only a minor role in transitions between multiple steady states in a continuous flow stirred tank reactor (CSTR).

  4. Adaptive Controller Design for Continuous Stirred Tank Reactor

    OpenAIRE

    Prabhu, K; V. Murali Bhaskaran

    2014-01-01

    Continues Stirred Tank Reactor (CSTR) is an important issue in chemical process and a wide range of research in the area of chemical engineering. Temperature Control of CSTR has been an issue in the chemical control engineering since it has highly non-linear complex equations. This study presents problem of temperature control of CSTR with the adaptive Controller. The Simulation is done in MATLAB and result shows that adaptive controller is an efficient controller for temperature control of C...

  5. Design of Controllers for Continuous Stirred Tank Reactor

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    Somasundaram Deepa

    2015-02-01

    Full Text Available The objective of the project is to design various controllers for temperature control in Continuous Stirred Tank Reactor (CSTR systems. Initially Zeigler-Nichols, modified Zeigler-Nichols, Tyreus-Luyben, Shen-Yu and IMC based method of tuned Proportional Integral (PI controller is designed and comparisons are made with Fuzzy Logic Controller. Simulations are carried out and responses are obtained for the above controllers. Maximum peak overshoot, Settling time, Rise time,  ISE, IAE  are chosen as performance index. From the analysis it is found that the Fuzzy Logic Controller  is a promising controller than the conventional controllers.

  6. Adaptive Controller Design for Continuous Stirred Tank Reactor

    Directory of Open Access Journals (Sweden)

    K. Prabhu

    2014-09-01

    Full Text Available Continues Stirred Tank Reactor (CSTR is an important issue in chemical process and a wide range of research in the area of chemical engineering. Temperature Control of CSTR has been an issue in the chemical control engineering since it has highly non-linear complex equations. This study presents problem of temperature control of CSTR with the adaptive Controller. The Simulation is done in MATLAB and result shows that adaptive controller is an efficient controller for temperature control of CSTR than PID controller.

  7. A cubic autocatalytic reaction in a continuous stirred tank reactor

    Energy Technology Data Exchange (ETDEWEB)

    Yakubu, Aisha Aliyu; Yatim, Yazariah Mohd [School of Mathematical Sciences, Universiti Sains Malaysia, 11800 USM, Penang Malaysia (Malaysia)

    2015-10-22

    In the present study, the dynamics of the cubic autocatalytic reaction model in a continuous stirred tank reactor with linear autocatalyst decay is studied. This model describes the behavior of two chemicals (reactant and autocatalyst) flowing into the tank reactor. The behavior of the model is studied analytically and numerically. The steady state solutions are obtained for two cases, i.e. with the presence of an autocatalyst and its absence in the inflow. In the case with an autocatalyst, the model has a stable steady state. While in the case without an autocatalyst, the model exhibits three steady states, where one of the steady state is stable, the second is a saddle point while the last is spiral node. The last steady state losses stability through Hopf bifurcation and the location is determined. The physical interpretations of the results are also presented.

  8. Kinetics of propionate conversion in anaerobic continuously stirred tank reactors

    DEFF Research Database (Denmark)

    Bangsø Nielsen, Henrik; Mladenovska, Zuzana; Ahring, Birgitte Kiær

    2008-01-01

    The kinetic parameters of anaerobic propionate degradation by biomass from 7 continuously stirred tank reactors differing in temperature, hydraulic retention time and substrate composition were investigated. In substrate-depletion experiments (batch) the maximum propionate degradation rate, A......-m, was estimated. The results demonstrate that the rate of endogenous substrate (propionate) production should be taken into account when estimating kinetic parameters in biomass from manure-based anaerobic reactors.......(max), and the half saturation constant, K-m, were initially estimated by applying the integrated Michaelis-Menten equation. A(max) was in the range from 22.8 to 29.1 mu mol gVS(-1) h(-1) while K-m, was in the range from 0.46-0.95 mM. In general, A(max) gave a good reflection of the reactor performances. Secondly...

  9. Implementation of Neural Control for Continuous Stirred Tank Reactor (CSTR

    Directory of Open Access Journals (Sweden)

    Karima M. Putrus

    2011-01-01

    Full Text Available In this paper a dynamic behavior and control of a jacketed continuous stirred tank reactor (CSTR is developed using different control strategies, conventional feedback control (PI and PID, and neural network (NARMA-L2, and NN Predictive control. The dynamic model for CSTR process is described by a first order lag system with dead time.The optimum tuning of control parameters are found by two different methods; Frequency Analysis Curve method (Bode diagram and Process Reaction Curve using the mean of Square Error (MSE method. It is found that the Process Reaction Curve method is better than the Frequency Analysis Curve method and PID feedback controller is better than PI feedback controller. The results show that the artificial neural network is the best method to control the CSTR process and it is better than the conventional method because it has smaller value of mean square error (MSE. MATLAB program is used as a tool of solution for all cases used in the present work.

  10. Chaotic behavior in the dynamical system of a continuous stirred tank reactor

    Science.gov (United States)

    Retzloff, D. G.; Chan, P. C.-H.; Chicone, C.; Offin, D.; Mohamed, R.

    1987-03-01

    The dynamical system describing a continuous stirred tank reactor (CSTR) for the reactions A→B→C and A→C, B→D is considered. A circulating attractor with accompanying circulating orbits is shown to exist when the critical point of the system is unique and unstable. The orbit structure has been numerically found to consist of periodic orbits and chaotic behavior.

  11. Effect of electromagnetic stirring on solidification structure of austenitic stainless steel in horizontal continuous casting

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    ZHOU Shu-cai

    2007-08-01

    Full Text Available An investigation on the influence of low frequency rotary electromagnetic stirring on solidification structure of austenitic stainless steel in horizontal continuous casting was experimentally conducted and carried out on an industrial trial basis. The results show that application of appropriate electromagnetic stirring parameters can obviously improve the macrostructure of austenitic stainless steel, in which both columnar and equiaxed grains can be greatly refined and shrinkage porosity or cavity zone along centerline can be remarkably decreased due to eliminating intracrystalline and enlarging equiaxed grains zone. The industrial trials verify that the electromagnetic stirring intensity of austenitic stainless steel should be higher than that of plain carbon steel. Electromagnetic stirring has somewhat affected the macrostructure of austenitic stainless steel even if the magnetic flux density of the electromagnetic stirring reaches 90 mT (amplitude reaches 141 mT in average at frequency f=3-4Hz, which provides a reference for the optimization of design and process parameters when applying the rotary electromagnetic stirrer.

  12. Effect of electromagnetic stirring on solidification structure of austenitic stainless steel in horizontal continuous casting

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    An investigation on the influence of low frequency rotary electromagnetic stirring on solidification structure of austenitic stainless steel in horizontal continuous casting was experimentally conducted and carried out on an industrial trial basis. The results show that application of appropriate electromagnetic stirring parameters can obviously improve the macrostructure of austenitic stainless steel, in which both columnar and equiaxed grains can be greatly refined and shrinkage porosity or cavity zone along centerline can be remarkably decreased due to eliminating intracrystalline and enlarging equiaxed grains zone. The industrial trials verify that the electromagnetic stirring intensity of austenitic stainless steel should be higher than that of plain carbon steel. Electromagnetic stirring has somewhat affected the macrostructure of austenitic stainless steel even if the magnetic flux density of the electromagnetic stirring reaches 90 mT (amplitude reaches 141 mT ) in average at frequency f=3-4Hz, which provides a reference for the optimization of design and process parameters when applying the rotary electromagnetic stirrer

  13. Effect of tryptone and ammonia on the biogas process in continuously stirred tank reactors treating cattle manure

    DEFF Research Database (Denmark)

    Nielsen, Hanne Bjerg; Ahring, Birgitte Kiær

    2007-01-01

    Two themophilic continuously stirred tank reactors, R1 and Two thermophilic continuously stirred tank reactors, R1 and R2, were subject to pulses of tryptone and ammonia. R1 was operated at an ammonia-N concentration of 3.0 g l(-1) and R2 was operated at an ammonia-N concentration of 1.7 g l(-1)....

  14. Selective precipitation of Cu from Zn in a pS controlled continuously stirred tank reactor

    NARCIS (Netherlands)

    Sampaio, R.M.; Timmers, R.A.; Xu, Y.; Keesman, K.J.; Lens, P.N.L.

    2009-01-01

    Copper was continuously and selectively precipitated with Na2S to concentrations below 0.3 ppb from water containing around 600 ppm of both Cu and Zn in a Continuously Stirred Tank Reactor. The pH was controlled at 3 and the pS at 25 (pS = ¿log(S2¿)) by means of an Ag2S sulfide selective electrode.

  15. Electromagnetic stirring in the continuous casting of steel. Agitacion electromagnetica en la colada continua de acero

    Energy Technology Data Exchange (ETDEWEB)

    Alvarez de Toledo, G.; Campo, O.; Lainez, E. (Sidenor, Basauri (Spain))

    1995-01-01

    The electromagnetic stirring of steel in the machines for the continuous casting process has improved the internal quality of the cast product. Experimental work with stirrers situated at different positions of continuous casting machines of billets has been carried out. The in-mould stirrer is the one that produces a major modification of the billet internal structure, and also the biggest decrease of the central segregation. An in mould electromagnetic coil has been developed which allows the use of high stirring power without producing an undesirable movement of the liquid steel in the meniscus zone, therefore no mould powders entrapments are produced. It has been developed a method for determining the optimum electric frequency of the stirrer. (Author) 31 refs.

  16. Evaluation of an integrated continuous stirred microbial electrochemical reactor: Wastewater treatment, energy recovery and microbial community.

    Science.gov (United States)

    Wang, Haiman; Qu, Youpeng; Li, Da; Zhou, Xiangtong; Feng, Yujie

    2015-11-01

    A continuous stirred microbial electrochemical reactor (CSMER) was developed by integrating anaerobic digestion (AD) and microbial electrochemical system (MES). The system was capable of treating high strength artificial wastewater and simultaneously recovering electric and methane energy. Maximum power density of 583±9, 562±7, 533±10 and 572±6 mW m(-2) were obtained by each cell in a four-independent circuit mode operation at an OLR of 12 kg COD m(-3) d(-1). COD removal and energy recovery efficiency were 87.1% and 32.1%, which were 1.6 and 2.5 times higher than that of a continuous stirred tank reactor (CSTR). Larger amount of Deltaproteobacteria (5.3%) and hydrogenotrophic methanogens (47%) can account for the better performance of CSMER, since syntrophic associations among them provided more degradation pathways compared to the CSTR. Results demonstrate the CSMER holds great promise for efficient wastewater treatment and energy recovery.

  17. Bistability in an uncatalyzed bromate oscillator in a continuously fed stirred tank reactor

    Science.gov (United States)

    Dutt, Arun K.; Müller, S. C.

    1996-01-01

    Uncatalyzed gallic acid oscillating system has been investigated in a continuously fed stirred tank reactor (CSTR). In the [Bromate]0-[Bromide]0 concentration space, a region has been located where a bistability is observed between an oscillatory branch and a flow branch. To our knowledge this is the first evidence of bistability in an uncatalyzed bromate oscillator. Some observations have been explained in terms of the skeleton mechanism proposed in the past.

  18. MODELLING AND CONTROL OF CONTINUOUS STIRRED TANK REACTOR WITH PID CONTROLLER

    Directory of Open Access Journals (Sweden)

    Artur Wodołażski

    2016-09-01

    Full Text Available This paper presents a model of dynamics control for continuous stirred tank reactor (CSTR in methanol synthesis in a three-phase system. The reactor simulation was carried out for steady and transient state. Efficiency ratio to achieve maximum performance of the product per reactor unit volume was calculated. Reactor dynamics simulation in closed loop allowed to received data for tuning PID controller (proportional-integral-derivative. The results of the regulation process allow to receive data for optimum reactor production capacity, along with local hot spots eliminations or temperature runaway.

  19. Bio-hydrogen production from molasses by anaerobic fermentation in continuous stirred tank reactor

    Science.gov (United States)

    Han, Wei; Li, Yong-feng; Chen, Hong; Deng, Jie-xuan; Yang, Chuan-ping

    2010-11-01

    A study of bio-hydrogen production was performed in a continuous flow anaerobic fermentation reactor (with an available volume of 5.4 L). The continuous stirred tank reactor (CSTR) for bio-hydrogen production was operated under the organic loading rates (OLR) of 8-32 kg COD/m3 reactor/d (COD: chemical oxygen demand) with molasses as the substrate. The maximum hydrogen production yield of 8.19 L/d was obtained in the reactor with the OLR increased from 8 kg COD/m3 reactor/d to 24 kg COD/m3 d. However, the hydrogen production and volatile fatty acids (VFAs) drastically decreased at an OLR of 32 kg COD/m3 reactor/d. Ethanoi, acetic, butyric and propionic were the main liquid fermentation products with the percentages of 31%, 24%, 20% and 18%, which formed the mixed-type fermentation.

  20. Biological treatment of phenolic wastewater in an anaerobic continuous stirred tank reactor

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    Firozjaee Taghizade Tahere

    2013-01-01

    Full Text Available In the present study, an anaerobic continuous stirred tank reactor (ACSTR with consortium of mixed culture was operated continuously for a period of 110 days. The experiments were performed with three different hydraulic retention times and by varying initial phenol concentrations between 100 to 1000 mg/L. A maximum phenol removal was observed at a hydraulic retention time (HRT of 4 days, with an organic loading rate (OLR of 170.86 mg/L.d. At this condition, phenol removal rate of 89% was achieved. In addition, the chemical oxygen demand (COD removal corresponds to phenol removal. Additional operating parameters such as pH, MLSS and biogas production rate of the effluents were also measured. The present study provides valuable information to design an anaerobic ACSTR reactor for the biodegradation of phenolic wastewater.

  1. Cascade degradation of organic matters in brewery wastewater using a continuous stirred microbial electrochemical reactor and analysis of microbial communities

    OpenAIRE

    Haiman Wang; Youpeng Qu; Da Li; Ambuchi, John J.; Weihua He; Xiangtong Zhou; Jia Liu; Yujie Feng

    2016-01-01

    A continuous stirred microbial electrochemical reactor (CSMER), comprising of a complete mixing zone (CMZ) and microbial electrochemical zone (MEZ), was used for brewery wastewater treatment. The system realized 75.4 ± 5.7% of TCOD and 64.9 ± 4.9% of TSS when fed with brewery wastewater concomitantly achieving an average maximum power density of 304 ± 31 m W m−2. Cascade utilization of organic matters made the CSMER remove a wider range of substrates compared with a continuous stirred tank re...

  2. Genetic Algorithm Based PID Controller Tuning Approach for Continuous Stirred Tank Reactor

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    A. Jayachitra

    2014-01-01

    Full Text Available Genetic algorithm (GA based PID (proportional integral derivative controller has been proposed for tuning optimized PID parameters in a continuous stirred tank reactor (CSTR process using a weighted combination of objective functions, namely, integral square error (ISE, integral absolute error (IAE, and integrated time absolute error (ITAE. Optimization of PID controller parameters is the key goal in chemical and biochemical industries. PID controllers have narrowed down the operating range of processes with dynamic nonlinearity. In our proposed work, globally optimized PID parameters tend to operate the CSTR process in its entire operating range to overcome the limitations of the linear PID controller. The simulation study reveals that the GA based PID controller tuned with fixed PID parameters provides satisfactory performance in terms of set point tracking and disturbance rejection.

  3. Immersion and invariance adaptive control of a class of continuous stirred tank reactors

    Institute of Scientific and Technical Information of China (English)

    Gaiyan HONG; Xiangbin LIU; Hongye SU

    2015-01-01

    An immersion and invariance (I&I) manifold based adaptive control algorithm is presented for a class of continuous stirred tank reactors (CSTR) to realize performance-oriented control in this paper. The nonlinear contraction method is combined into the control law design to render the closed-loop CSTR system globally asymptotically stable, firstly. Then, the I&I method is used to form the adaptation law such that the off-the-manifold coordinate (the parameter estimation error) converges to zero using P-monotone property enforced by selecting tuning function in manifold. As a result, the state of the closed-loop CSTR converges to its desired value asymptotically. The simulation is given to illustrate the effectiveness of the presented algorithm.

  4. Fluid dynamic analysis of a continuous stirred tank reactor for technical optimization of wastewater digestion.

    Science.gov (United States)

    Hurtado, F J; Kaiser, A S; Zamora, B

    2015-03-15

    Continuous stirred tank reactors (CSTR) are widely used in wastewater treatment plants to reduce the organic matter and microorganism present in sludge by anaerobic digestion. The present study carries out a numerical analysis of the fluid dynamic behaviour of a CSTR in order to optimize the process energetically. The characterization of the sludge flow inside the digester tank, the residence time distribution and the active volume of the reactor under different criteria are determined. The effects of design and power of the mixing system on the active volume of the CSTR are analyzed. The numerical model is solved under non-steady conditions by examining the evolution of the flow during the stop and restart of the mixing system. An intermittent regime of the mixing system, which kept the active volume between 94% and 99%, is achieved. The results obtained can lead to the eventual energy optimization of the mixing system of the CSTR.

  5. Thermodynamics of open nonlinear systems far from equilibrium: The continuously stirred tank reactor

    Science.gov (United States)

    Yoshida, Nobuo

    1993-11-01

    A thermodynamic analysis is made of a continuously stirred tank reactor (CSTR) which is fed with ideal gases and in which arbitrary types of chemical reactions take place. For stationary states and oscillatory ones in which limit cycles are established, expressions are derived which describe the change of entropy of the reactor contents relative to the feed in terms of explicit quantities, including the rate of entropy production due to the chemical reactions. This entropy change is shown to be always greater than what would be observed in closed systems under comparable circumstances. It is pointed out that this statement is beyond what the second law of thermodynamics can predict. In previous articles, entropy and entropy production have been found to follow certain systematic trends in some specific models based on the CSTR. That work is compared with the present theory.

  6. Artificial Neural Networks Based Modeling and Control of Continuous Stirred Tank Reactor

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    R. S.M.N. Malar

    2009-01-01

    Full Text Available Continuous Stirred Tank Reactor (CSTR is one of the common reactors in chemical plant. Problem statement: Developing a model incorporating the nonlinear dynamics of the system warrants lot of computation. An efficient control of the product concentration can be achieved only through accurate model. Approach: In this study, attempts were made to alleviate the above mentioned problem using “Artificial Intelligence” (AI techniques. One of the AI techniques namely Artificial Neural Networks (ANN was used to model the CSTR incorporating its non-linear characteristics. Two nonlinear models based control strategies namely internal model control and direct inverse control were designed using the neural networks and applied to the control of isothermal CSTR. Results: The simulation results for the above control schemes with set point tracking were presented. Conclusion: Results indicated that neural networks can learn accurate models and give good non-linear control when model equations are not known.

  7. Anaerobic digestion performance of vinegar residue in continuously stirred tank reactor.

    Science.gov (United States)

    Li, Lin; Feng, Lu; Zhang, Ruihong; He, Yanfeng; Wang, Wen; Chen, Chang; Liu, Guangqing

    2015-06-01

    Anaerobic digestion (AD) of vinegar residue was investigated in continuously stirred tank reactor (CSTR). The influence of organic loading rate (OLR) and effluent recirculation on AD performance of vinegar residue was tested. Five OLRs, 1.0, 1.5, 2.0, 2.5, and 3.0 g(vs) L(-1) d(-1), were used. The highest volumetric methane productivity of 581.88 mL L(-1) was achieved at OLR of 2.5 g(vs) L(-1) d(-1). Effluent reflux ratio was set as 50%, the results showed that effluent recirculation could effectively neutralize the acidity of vinegar residue, raise the pH of the feedstock, and enhance the buffering capacity of the AD system. Anaerobic digestion of vinegar residue could be a promising way not only for converting this waste into gas energy but also alleviating environmental pollution which might be useful for future industrial application.

  8. Stability criteria and critical runway conditions of propylene glycol manufacture in a continuous stirred tank reactor

    Directory of Open Access Journals (Sweden)

    Miguel Ángel Gómez

    2015-08-01

    Full Text Available Here, a new method for the analysis of the steady state and the safety operational conditions of the hydrolysis of propylene oxide with excess of water, in a Continuous Stirred Tank Reactor (CSTR, was developed. For industrial operational typical values, at first, the generated and removed heat balances were examined. Next, the effect of coolant fluid temperature in the critical ignition and extinction temperatures (TCI and TCE, respectively was analyzed. The influence of the heat exchange parameter (hS on coolant and critical temperatures was also studied. Finally, the steady state operation areas were defined. The existence of multiple stable states was recognized when the heat exchange parameter was in the range 6.636 < hS kJ/(min.K < 11.125. Unstable operation area was located between the TCI and TCE values, restricting the reactor operation area to the low stable temperatures.

  9. CFD optimization of continuous stirred-tank (CSTR) reactor for biohydrogen production.

    Science.gov (United States)

    Ding, Jie; Wang, Xu; Zhou, Xue-Fei; Ren, Nan-Qi; Guo, Wan-Qian

    2010-09-01

    There has been little work on the optimal configuration of biohydrogen production reactors. This paper describes three-dimensional computational fluid dynamics (CFD) simulations of gas-liquid flow in a laboratory-scale continuous stirred-tank reactor used for biohydrogen production. To evaluate the role of hydrodynamics in reactor design and optimize the reactor configuration, an optimized impeller design has been constructed and validated with CFD simulations of the normal and optimized impeller over a range of speeds and the numerical results were also validated by examination of residence time distribution. By integrating the CFD simulation with an ethanol-type fermentation process experiment, it was shown that impellers with different type and speed generated different flow patterns, and hence offered different efficiencies for biohydrogen production. The hydrodynamic behavior of the optimized impeller at speeds between 50 and 70 rev/min is most suited for economical biohydrogen production.

  10. A new halogen-free chemical oscillator: the reaction between permanganate ion and ninhydrin in a continuously stirred tank reactor

    Science.gov (United States)

    Treindl, Ľudovít; Nagy, Arpád

    1987-07-01

    The reaction between permanganate ion and ninhydrin in the presence of phosphoric acid in aqueous solution shows sustained oscillations in a continuously stirred tank reactor (CSTR). It exhibits a kinetic bistability between an oscillatory and a stationary state. Our new oscillating system seems to be a second permanganate chemical oscillator, thus broadening the small group of non-halogen-based chemical oscillators.

  11. A mathematical model for multiple hydrogeneration reactions in a continuous stirred three phase slurry reactor with an evaporating solvent

    NARCIS (Netherlands)

    Janssen, H.J.; Westerterp, K.R.; Vos, J.

    1992-01-01

    An experimental study of the catalytic hydorgenation of 2,4-dinitrotoluene (DNT) in a mini-installation with a continuously operated stirred three-phase slurry reactor and an evaporating solvent is discussed. Some characteristic properties of the reactor system and the influence of the operating par

  12. Solidification Structure of Continuous Casting Large Round Billets under Mold Electromagnetic Stirring

    Institute of Scientific and Technical Information of China (English)

    Tao SUN; Feng YUE; Hua-jie WU; Chun GUO; Ying LI; Zhong-cun MA

    2016-01-01

    The solidification structure of a continuous casting large round billet was analyzed by a cellular-automaton-finite-element coupling model using the ProCAST software.The actual and simulated solidification structures were compared under mold electromagnetic stirring (MEMS)conditions (current of 300 A and frequency of 3 Hz).There-after,the solidification structures of the large round billet were investigated under different superheats,casting speeds,and secondary cooling intensities.Finally,the effect of the MEMS current on the solidification structures was obtained under fixed superheat,casting speed,secondary cooling intensity,and MEMS frequency.The model accurately simulated the actual solidification structures of any steel,regardless of its size and the parameters used in the continuous casting process.The ratio of the central equiaxed grain zone was found to increase with decreasing su-perheat,increasing casting speed,decreasing secondary cooling intensity,and increasing MEMS current.The grain size obviously decreased with decreasing superheat and increasing MEMS current but was less sensitive to the casting speed and secondary cooling intensity.

  13. [Research on change process of nitrosation granular sludge in continuous stirred-tank reactor].

    Science.gov (United States)

    Yin, Fang-Fang; Liu, Wen-Ru; Wang, Jian-Fang; Wu, Peng; Shen, Yao-Liang

    2014-11-01

    In order to investigate the effect of different types of reactors on the nitrosation granular sludge, a continuous stirred-tank reactor (CSTR) was studied, using mature nitrosation granular sludge cultivated in sequencing batch reactor (SBR) as seed sludge. Results indicated that the change of reactor type and influent mode could induce part of granules to lose stability with gradual decrease in sludge settling ability during the initial period of operation. However, the flocs in CSTR achieved fast granulation in the following reactor operation. In spite of the changes of particle size distribution, e. g. the decreasing number of granules with diameter larger than 2.5 mm and the increasing number of granules with diameter smaller than 0.3 mm, granular sludge held the absolute predominance of sludge morphology in CSTR during the entire experimental period. Moreover, results showed that the change of reactor type and influent mode didn't affect the nitrite accumulation rate which was still kept at about 85% in effluent. Additionally, the average activity of the sludge in CSTR was stronger than that of the seed sludge, because the newly generated small particles in CSTR had higher specific reactive activity than the larger granules.

  14. Removal of phosphorus from aqueous solution by Posidonia oceanica fibers using continuous stirring tank reactor

    Energy Technology Data Exchange (ETDEWEB)

    Wahab, Mohamed Ali, E-mail: waheb_med@yahoo.fr [University of Carthage, Water Research and Technologies Centre (CERTE), Wastewater Treatment and Recycling Laboratory, B.P. 273, 8020 Soliman (Tunisia); Hassine, Rafik Ben [International Environmental Green Technology (IGET) (Tunisia); Jellali, Salah, E-mail: salah.jallali@certe.rnrt.tn [University of Carthage, Water Research and Technologies Centre (CERTE), Wastewater Treatment and Recycling Laboratory, B.P. 273, 8020 Soliman (Tunisia)

    2011-05-15

    The present study aims to develop a new potentially low-cost, sustainable treatment approach to soluble inorganic phosphorus removal from synthetic solutions and secondary wastewater effluents in which a plant waste (Posidonia oceanica fiber: POF) is used for further agronomic benefit. Dynamic flow tests using a continuous stirred tank reactor (CSTR) were carried out to study the effect of initial concentration of phosphorus, amount of adsorbent, feeding flow rate and anions competition. The experimental results showed that the removal efficiency of phosphorus from synthetic solutions is about 80% for 10 g L{sup -1} of POF. In addition, the variation of the initial concentration of phosphorus from 8 to 50 mg L{sup -1} increased the adsorption capacity from 0.99 to 3.03 mg g{sup -1}. The use of secondary treated wastewater showed the presence of competition phenomenon between phosphorus and sulphate which could be overcoming with increasing the sorptive surface area and providing more adsorption sites when increasing the adsorbent dosage of POF. Compared with columns studies, this novel CSTR system showed more advantages for the removal of soluble phosphorus as a tertiary treatment of urban secondary effluents with more adsorption efficiency and capacity, in addition to the prospect use of saturated POF with nutriment as fertilizer and compost.

  15. Cassava Stillage Treatment by Thermophilic Anaerobic Continuously Stirred Tank Reactor (CSTR)

    Science.gov (United States)

    Luo, Gang; Xie, Li; Zou, Zhonghai; Zhou, Qi

    2010-11-01

    This paper assesses the performance of a thermophilic anaerobic Continuously Stirred Tank Reactor (CSTR) in the treatment of cassava stillage under various organic loading rates (OLRs) without suspended solids (SS) separation. The reactor was seeded with mesophilic anaerobic granular sludge, and the OLR increased by increments to 13.80 kg COD/m3/d (HRT 5d) over 80 days. Total COD removal efficiency remained stable at 90%, with biogas production at 18 L/d (60% methane). Increase in the OLR to 19.30 kg COD/m3/d (HRT 3d), however, led to a decrease in TCOD removal efficiency to 79% due to accumulation of suspended solids and incomplete degradation after shortened retention time. Reactor performance subsequently increased after OLR reduction. Alkalinity, VFA and pH levels were not significantly affected by OLR variation, indicating that no additional alkaline or pH adjustment is required. More than half of the SS in the cassava stillage could be digested in the process when HRT was 5 days, which demonstrated the suitability of anaerobic treatment of cassava stillage without SS separation.

  16. Bioleaching of an organic-rich polymetallic concentrate using stirred-tank technology

    OpenAIRE

    Spolaore, Pauline; Joulian, Catherine; Gouin, Jérôme; Ibanez, A.; Augé, Thierry; Morin, Dominique; d'Hugues, Patrick

    2009-01-01

    The bioleaching of a concentrate produced from a black shale ore in an industrial operation in Poland was assessed. Following preliminary batch culture tests, processing in continuous conditions was tested to determine the main specifications for the application of the stirred-tank technology to this organic-rich polymetallic concentrate. The experimental work was carried out in a laboratory-scale unit consisting of three stirred tanks (50 L or 20 L) using an acidophilic and moderate thermoph...

  17. Dynamical Analysis of a Continuous Stirred-Tank Reactor with the Formation of Biofilms for Wastewater Treatment

    Directory of Open Access Journals (Sweden)

    Karen López Buriticá

    2015-01-01

    Full Text Available This paper analyzes the dynamics of a system that models the formation of biofilms in a continuous stirred-tank reactor (CSTR when it is utilized for wastewater treatment. The growth rate of the microorganisms is modeled using two different kinetics, Monod and Haldane kinetics, with the goal of studying the influence of each in the system. The equilibrium points are identified through a stability analysis, and the bifurcations found are characterized.

  18. The Reduced Rank of Ensemble Kalman Filter to Estimate the Temperature of Non Isothermal Continue Stirred Tank Reactor

    OpenAIRE

    Erna Apriliani; Dieky Adzkiya; Arief Baihaqi

    2011-01-01

    Kalman filter is an algorithm to estimate the state variable of dynamical stochastic system. The square root ensemble Kalman filter is an modification of Kalman filter. The square root ensemble Kalman filter is proposed to keep the computational stability and reduce the computational time. In this paper we study the efficiency of the reduced rank ensemble Kalman filter. We apply this algorithm to the non isothermal continue stirred tank reactor problem. We decompose the covariance of the ense...

  19. Control of the sulfide (S2-) concentration for optimal zinc removal by sulfide precipitation in a continuously stirred tank reactor

    NARCIS (Netherlands)

    Veeken, A.H.M.; Akoto, L.; Pol, L.W.H.; Weijma, J.

    2003-01-01

    Precipitation of Zn2+ with S2− was studied at room temperature in a continuously stirred tank reactor of 0.5 l to which solutions of ZnSO4 (800–5800 mg Zn2+/l) and Na2S were supplied. The pH was controlled at 6.5 and S2− concentration in the reactor was controlled at set point values ranging from 3.

  20. The nonequilibrium electromotive force. II. Theory for a continuously stirred tank reactor

    Science.gov (United States)

    Keizer, Joel

    1987-10-01

    In previous work [J. Keizer, J. Chem. Phys. 82, 2751 (1985)] we used statistical nonequilibrium thermodynamics to predict a non-Nernstian component to the electromotive force (EMF) for half-reactions involving reactants at nonequilibrium steady states. In this paper we present a simple theory for calculating the nonequilibrium component of the EMF based on the elementary transport processes occurring in a continuously stirred tank reactor (CSTR). The calculations utilize the density-density correlation function, which is obtained from the statistical theory of nonequilibrium thermodynamics. This gives rise to an expression for the second partial derivatives of the generalized entropy, or sigma function, which is used to calculate generalized chemical potentials. The generalized chemical potentials are related to the EMF through a generalization of the Nernst equation. The calculations presented here depend on the residence time in the CSTR, reaction rate constants, feed line concentrations in the CSTR, and the diffusion constants of reactants and products. A characteristic diffusion length is used to represent the length scale below which turbulent mixing effects are not important. Calculations with the theory are carried out for several different reaction mechanisms, including A+B⇄C; A+B⇄C, D+E⇄B; A+B⇄2B; and A+B→C+D, A+D→C+E. Values of the nonequilibrium EMF depend on the mechanism as well as all of the transport parameters cited above. For a plausible choice of the diffusion length, corrections to the Nernst formula can be as large as 10-15 mV. Specific calculations for the reaction of Fe2+ with S2O2-8 are shown in the preceding paper to agree with experimental measurements on this system in a CSTR.

  1. Production of hydrogen in a granular sludge-based anaerobic continuous stirred tank reactor

    Energy Technology Data Exchange (ETDEWEB)

    Show, Kuan-Yeow [Faculty of Engineering and Science, University of Tunku Abdul Rahman, 53300 Setapak, Kuala Lumpur (Malaysia); Zhang, Zhen-Peng; Tay, Joo-Hwa [School of Civil and Environmental Engineering, Nanyang Technological University, 639798 (Singapore); Institute of Environmental Science and Engineering, Nanyang Technological University, 637723 (Singapore); Tee Liang, David [Institute of Environmental Science and Engineering, Nanyang Technological University, 637723 (Singapore); Lee, Duu-Jong [Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan, RO (China); Jiang, Wen-Ju [Department of Environmental Science and Engineering, Sichuan University, Chengdu 610065 (China)

    2007-12-15

    An investigation on biohydrogen production was conducted in a granular sludge-based continuous stirred tank reactor (CSTR). The reactor performance was assessed at five different glucose concentrations of 2.5, 5, 10, 20 and 40 g/L and four hydraulic retention times (HRTs) of 0.25, 0.5, 1 and 2 h, resulting in the organic loading rates (OLRs) ranged between 2.5 and 20 g-glucose/L h. Carbon flow was traced by analyzing the composition of gaseous and soluble metabolites as well as the cell yield. Butyrate, acetate and ethanol were found to be the major soluble metabolite products in the biochemical synthesis of hydrogen. Carbon balance analysis showed that more than half of the glucose carbon was converted into unidentified soluble products at an OLR of 2.5 g-glucose/L h. It was found that high hydrogen yields corresponded to a sludge loading rate in between 0.6 and 0.8 g-glucose/g-VSS h. Substantial suppression in hydrogen yield was noted as the sludge loading rate fell beyond the optimum range. It is deduced that decreasing the sludge loading rate induced the metabolic shift of biochemical reactions at an OLR of 2.5 g-glucose/L h, which resulted in a substantial reduction in hydrogen yield to 0.36-0.41 mol-H{sub 2}/mol-glucose. Optimal operation conditions for peak hydrogen yield (1.84 mol-H{sub 2}/mol-glucose) and hydrogen production rate (3.26 L/L h) were achieved at an OLR of 20 g-glucose/L h, which corresponded to an HRT of 0.5 h and an influent glucose concentration of 10 g/L. Influence of HRT and substrate concentration on the reactor performance was interrelated and the adverse impact on hydrogen production was noted as substrate concentration was higher than 20 g/L or HRT was shorter than 0.5 h. The experimental study indicated that a higher OLR derived from appropriate HRTs and substrate concentrations was desirable for hydrogen production in such a granule-based CSTR. (author)

  2. Extended continuous-flow stirred-tank reactor (ECSTR) as a simple model of life under thermodynamically open conditions

    Science.gov (United States)

    Takinoue, Masahiro; Ma, Yue; Mori, Yoshihito; Yoshikawa, Kenichi

    2009-07-01

    A continuous-flow stirred-tank reactor (CSTR) is a vital tool for investigating the nonlinear dynamics of chemical systems. This report proposes an extended CSTR (ECSTR) inspired by active and passive transports through a closed membrane in living systems. In addition to the externally-controlled flow in a conventional CSTR, we introduce passive diffusion through a membrane into the ECSTR. This extension allows us to control the chemical dynamics with a larger parameter-dimension. Numerical analyses show that the ECSTR can expand an oscillatory region in the parameter space and can convert a non-oscillatory chemical system to an oscillatory system.

  3. Cascade degradation of organic matters in brewery wastewater using a continuous stirred microbial electrochemical reactor and analysis of microbial communities

    Science.gov (United States)

    Wang, Haiman; Qu, Youpeng; Li, Da; Ambuchi, John J.; He, Weihua; Zhou, Xiangtong; Liu, Jia; Feng, Yujie

    2016-01-01

    A continuous stirred microbial electrochemical reactor (CSMER), comprising of a complete mixing zone (CMZ) and microbial electrochemical zone (MEZ), was used for brewery wastewater treatment. The system realized 75.4 ± 5.7% of TCOD and 64.9 ± 4.9% of TSS when fed with brewery wastewater concomitantly achieving an average maximum power density of 304 ± 31 m W m−2. Cascade utilization of organic matters made the CSMER remove a wider range of substrates compared with a continuous stirred tank reactor (CSTR), in which process 79.1 ± 5.6% of soluble protein and 86.6 ± 2.2% of soluble carbohydrates were degraded by anaerobic digestion in the CMZ and short-chain volatile fatty acids were further decomposed and generated current in the MEZ. Co-existence of fermentative bacteria (Clostridium and Bacteroides, 19.7% and 5.0%), acetogenic bacteria (Syntrophobacter, 20.8%), methanogenic archaea (Methanosaeta and Methanobacterium, 40.3% and 38.4%) and exoelectrogens (Geobacter, 12.4%) as well as a clear spatial distribution and syntrophic interaction among them contributed to the cascade degradation process in CSMER. The CSMER shows great promise for practical wastewater treatment application due to high pre-hydrolysis and acidification rate, high energy recovery and low capital cost. PMID:27270788

  4. Cascade degradation of organic matters in brewery wastewater using a continuous stirred microbial electrochemical reactor and analysis of microbial communities.

    Science.gov (United States)

    Wang, Haiman; Qu, Youpeng; Li, Da; Ambuchi, John J; He, Weihua; Zhou, Xiangtong; Liu, Jia; Feng, Yujie

    2016-06-07

    A continuous stirred microbial electrochemical reactor (CSMER), comprising of a complete mixing zone (CMZ) and microbial electrochemical zone (MEZ), was used for brewery wastewater treatment. The system realized 75.4 ± 5.7% of TCOD and 64.9 ± 4.9% of TSS when fed with brewery wastewater concomitantly achieving an average maximum power density of 304 ± 31 m W m(-2). Cascade utilization of organic matters made the CSMER remove a wider range of substrates compared with a continuous stirred tank reactor (CSTR), in which process 79.1 ± 5.6% of soluble protein and 86.6 ± 2.2% of soluble carbohydrates were degraded by anaerobic digestion in the CMZ and short-chain volatile fatty acids were further decomposed and generated current in the MEZ. Co-existence of fermentative bacteria (Clostridium and Bacteroides, 19.7% and 5.0%), acetogenic bacteria (Syntrophobacter, 20.8%), methanogenic archaea (Methanosaeta and Methanobacterium, 40.3% and 38.4%) and exoelectrogens (Geobacter, 12.4%) as well as a clear spatial distribution and syntrophic interaction among them contributed to the cascade degradation process in CSMER. The CSMER shows great promise for practical wastewater treatment application due to high pre-hydrolysis and acidification rate, high energy recovery and low capital cost.

  5. Cascade degradation of organic matters in brewery wastewater using a continuous stirred microbial electrochemical reactor and analysis of microbial communities.

    Science.gov (United States)

    Wang, Haiman; Qu, Youpeng; Li, Da; Ambuchi, John J; He, Weihua; Zhou, Xiangtong; Liu, Jia; Feng, Yujie

    2016-01-01

    A continuous stirred microbial electrochemical reactor (CSMER), comprising of a complete mixing zone (CMZ) and microbial electrochemical zone (MEZ), was used for brewery wastewater treatment. The system realized 75.4 ± 5.7% of TCOD and 64.9 ± 4.9% of TSS when fed with brewery wastewater concomitantly achieving an average maximum power density of 304 ± 31 m W m(-2). Cascade utilization of organic matters made the CSMER remove a wider range of substrates compared with a continuous stirred tank reactor (CSTR), in which process 79.1 ± 5.6% of soluble protein and 86.6 ± 2.2% of soluble carbohydrates were degraded by anaerobic digestion in the CMZ and short-chain volatile fatty acids were further decomposed and generated current in the MEZ. Co-existence of fermentative bacteria (Clostridium and Bacteroides, 19.7% and 5.0%), acetogenic bacteria (Syntrophobacter, 20.8%), methanogenic archaea (Methanosaeta and Methanobacterium, 40.3% and 38.4%) and exoelectrogens (Geobacter, 12.4%) as well as a clear spatial distribution and syntrophic interaction among them contributed to the cascade degradation process in CSMER. The CSMER shows great promise for practical wastewater treatment application due to high pre-hydrolysis and acidification rate, high energy recovery and low capital cost. PMID:27270788

  6. Problem Based Learning (PBL: Analysis of Continuous Stirred Tank Chemical Reactors with a Process Control Approach

    Directory of Open Access Journals (Sweden)

    Regalado-Méndez Alejandro

    2010-10-01

    Full Text Available This work is focused on a project that integrates the curriculum such as thermodynamic, chemical reactorengineering, linear algebra, differential equations and computer programming. The purpose is thatstudents implement the most knowledge and tools to analyse the stirred tank chemical reactor as a simpledynamic system. When the students finished this practice they should have learned about analysis ofdynamic system through bifurcation analysis, hysteresis phenomena, find equilibrium points, stabilitytype, and phase portrait. Once the steps were accomplished, we concluded that the purpose wassatisfactorily reached with an increment in creative ability. The student showed a bigger interesting inthis practice, since they worked in group. The most important fact is that the percentage of failure amongstudents was 10%. Finally, using alternative teaching-learning process improves the Mexican systemeducation.

  7. Linear and Non-linear Multi-Input Multi-Output Model Predictive Control of Continuous Stirred Tank Reactor

    Directory of Open Access Journals (Sweden)

    Muayad Al-Qaisy

    2013-04-01

    Full Text Available In this article, multi-input multi-output (MIMO linear model predictive controller (LMPC based on state space model and nonlinear model predictive controller based on neural network (NNMPC are applied on a continuous stirred tank reactor (CSTR. The idea is to have a good control system that will be able to give optimal performance, reject high load disturbance, and track set point change. In order to study the performance of the two model predictive controllers, MIMO Proportional-Integral-Derivative controller (PID strategy is used as benchmark. The LMPC, NNMPC, and PID strategies are used for controlling the residual concentration (CA and reactor temperature (T. NNMPC control shows a superior performance over the LMPC and PID controllers by presenting a smaller overshoot and shorter settling time.

  8. Stochastic resonance in the presence or absence of external signal in the continuous stirred tank reactor system

    Science.gov (United States)

    Hou, Zhonghuai; Xin, Houwen

    1999-07-01

    A two variable model, which has been proposed to describe a first-order, exothermic, irreversible reaction A→B carried out in a continuous stirred tank reactor (CSTR), is investigated when the control parameter is modulated by random and/or periodic forces. Within the bistable region where a limit cycle and a stable node coexist, stochastic resonance (SR) is observed when both random and periodic modulations are present. In the absence of periodic external signal noise induced coherent oscillations (NICO) appear when the control parameter is randomly modulated near the supercritical Hopf bifurcation point. In addition, the NICO-strength goes through a maximum with the increment of the noise intensity, characteristic for the occurrence of internal signal stochastic resonance (ISSR).

  9. Operational strategies for thermophilic anaerobic digestion of organic fraction of municipal solid waste in continuously stirred tank reactors

    DEFF Research Database (Denmark)

    Angelidaki, Irini; Cui, J.; Chen, X.;

    2006-01-01

    Three operational strategies to reduce inhibition due to ammonia during thermophilic anaerobic digestion of source-sorted organic fraction of municipal solid waste (SS-OFMSW) rich in proteins were investigated. Feed was prepared by diluting SS-OFMSW (ratio of 1:4) with tap water or reactor process...... water with or without stripping ammonia. Three continuously stirred tank reactors were operated at 55 degrees C with 11.4 gVS d(-1) loading rate and 15 d retention time. Total ammonia nitrogen (TAN) level in the reactor fed with recirculated water alone was spiked to 3.5 and 5.5 g-N l(-1) through...... ammonium bicarbonate additions. Dilution of SS-OFMSW with fresh water showed a stable performance with volatile fatty acids of water after stripping ammonia showed even better performance with a methane yield...

  10. Numerical investigation of the influence of kinetics and shape factor on barium sulfate precipitation in a continuous stirred tank

    Institute of Scientific and Technical Information of China (English)

    Zheng WANG; ZaiSha MAO; Chao YANG; Qinghua ZHANG; Jingcai CHENG

    2009-01-01

    The effect of kinetics and shape factor on barium sulfate precipitation in a continuous stirred tank has been investigated numerically through solving the standard momentum and mass transport equations in combination with the moment equations for crystal population balance. The numerical method was validated with the literature data. The simulated results include the distribution of the local supersaturation ratio in the reactor, the mean crystal size, and the coefficient of variation. The simulation results show that the value of shape factor used in the model affected greatly the mean crystal size and the moments of the crystal size distribution. The influence of the kinetic expressions on the simulation is also analyzed. It is important to investigate the relationship of the shape factor with the precipitator type and other operation conditions to obtain reliable simulation results and suitable kinetic equations of crystal nucleation and growth rates.

  11. Optimal conditions and operational parameters for conversion of Robusta coffee residues in a continuous stirred tank reactor

    Energy Technology Data Exchange (ETDEWEB)

    Msambichaka, B.L.; Kivaisi, A.K.; Rubindamayugi, M.S.T. [Univ. of Dar es Salaam, Applied Microbiology Unit (Tanzania, United Republic of)

    1997-12-31

    This experiment studied the possibility of optimizing anaerobic degradation, developing microbial adaptation and establishing long term process stability in a Continuous Stirred Tank Reactor (CSTR) running on Robusta coffee hulls as feed substrate. Decrease in lag phase and increase in methane production rate in batch culture experiment conducted before and after process stabilization of each operational phase in the CSTR clearly suggested that microbial adaptation to increasing coffee percentage composition was attained. Through gradual increase of coffee percentage composition, from 10% coffee, 2% VS, 20 days HRT and a 1 g VS/1/day loading rate to 80% coffee, 4.5% VS, 12 days HRT and a loading rate of 3 g VS/1/day the CSTR system was optimized at a maximum methane yield of 535 ml/g VS. Again it was possible to attain long term process stability at the above mentioned optimal operational parameters for a further 3 month period. (au)

  12. COMPUTER SIMULATION OF CONTINUOUS ELECTROMAGNETIC STIRRING FOR MAKING RHEOLOGIC SEMI-SOLID SLURRY OF ZL112Y ALUMINUM ALLOY

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    To realize the technology of fabricating the rheologic semi-solid slurry of ZL112Y aluminum alloy via continues electromagnetic stirring process, ANSYS software was used to simulate electromagnetic force field and fluid velocity field in the alloy melt in a crucible tube in three coils. In the first section of the paper, eletromagnetic force field and fluid velocity field caused by single coil were simulated. The result of this simulation gives an average velocity of 3.2 cm/s and it is called critical velocity because a fluid velocity over it will cause a fine and spherical structure of solid primary a in a semi-solid melt. And, from this result, a reasonable temperature of semi-solid of the alloy and an electrical current intensity were established. The electrical current intensity of the result of this simulation corresponded to the current intensity used in a practice experiment, in which the primary a was obviously refined and sphericized. Based on this simulation of single coil electromagnetic stirring, in the second section of the paper, eletromagnetic force field and fluid velocity field caused by three coils were simulated. The result of the simulation shows that, 1) there is a semi-solid zone of 32 mm from bottom of the crucible tube to the upper; 2) the electrical current intensities of three coils of 400 A, 600 A, and 400 A, which were set to top range, middle range and bottom range of the tube, respectively, were the optimum parameters of electromagnetic current intensity under the condition of this investigation; and 3) under effect of these electromagnetic current intensity, the fluid velocities of the melt in the tube were 6.3 cm/s in top range, 3.75 cm/s in middle range, and 3.9 cm/s in bottom range of it, respectively.

  13. Biohydrogen production in a continuous stirred tank bioreactor from synthesis gas by anaerobic photosynthetic bacterium: Rhodopirillum rubrum.

    Science.gov (United States)

    Younesi, Habibollah; Najafpour, Ghasem; Ku Ismail, Ku Syahidah; Mohamed, Abdul Rahman; Kamaruddin, Azlina Harun

    2008-05-01

    Hydrogen may be considered a potential fuel for the future since it is carbon-free and oxidized to water as a combustion product. Bioconversion of synthesis gas (syngas) to hydrogen was demonstrated in continuous stirred tank bioreactor (CSTBR) utilizing acetate as a carbon source. An anaerobic photosynthetic bacterium, Rhodospirillum rubrum catalyzed water-gas shift reaction which was applied for the bioconversion of syngas to hydrogen. The continuous fermentation of syngas in the bioreactor was continuously operated at various gas flow rates and agitation speeds, for the period of two months. The gas flow rates were varied from 5 to 14 ml/min. The agitation speeds were increasingly altered in the range of 150-500 rpm. The pH and temperature of the bioreactor was set at 6.5 and 30 degrees C. The liquid flow rate was kept constant at 0.65 ml/min for the duration of 60 days. The inlet acetate concentration was fed at 4 g/l into the bioreactor. The hydrogen production rate and yield were 16+/-1.1 mmol g(-1)cell h(-1) and 87+/-2.4% at fixed agitation speed of 500 rpm and syngas flow rate of 14 ml/min, respectively. The mass transfer coefficient (KLa) at this condition was approximately 72.8h(-1). This new approach, using a biocatalyst was considered as an alternative method of conventional Fischer-Tropsch synthetic reactions, which were able to convert syngas into hydrogen.

  14. Molecular weight​/branching distribution modeling of low-​density-​polyethylene accounting for topological scission and combination termination in continuous stirred tank reactor

    NARCIS (Netherlands)

    N. Yaghini; P.D. Iedema

    2014-01-01

    We present a comprehensive model to predict the molecular weight distribution (MWD),(1) and branching distribution of low-density polyethylene (IdPE),(2) for free radical polymerization system in a continuous stirred tank reactor (CSTR).(3) The model accounts for branching, by branching moment or ps

  15. The catalytic hydrogenation of 2,4-dinitrotoluene in a continuous stirred three-phase slurry reactor with an evaporting solvent

    NARCIS (Netherlands)

    Westerterp, K.R.; Janssen, H.J.; Kwast, van der H.J.

    1992-01-01

    An experimental study of the catalytic hydorgenation of 2,4-dinitrotoluene (DNT) in a mini-installation with a continuously operated stirred three-phase slurry reactor and an evaporating solvent is discussed. Some characteristic properties of the reactor system and the influence of the operating par

  16. Production of biohythane from food waste via an integrated system of continuously stirred tank and anaerobic fixed bed reactors.

    Science.gov (United States)

    Yeshanew, Martha M; Frunzo, Luigi; Pirozzi, Francesco; Lens, Piet N L; Esposito, Giovanni

    2016-11-01

    The continuous production of biohythane (mixture of biohydrogen and methane) from food waste using an integrated system of a continuously stirred tank reactor (CSTR) and anaerobic fixed bed reactor (AFBR) was carried out in this study. The system performance was evaluated for an operation period of 200days, by stepwise shortening the hydraulic retention time (HRT). An increasing trend of biohydrogen in the CSTR and methane production rate in the AFBR was observed regardless of the HRT shortening. The highest biohydrogen yield in the CSTR and methane yield in the AFBR were 115.2 (±5.3)L H2/kgVSadded and 334.7 (±18.6)L CH4/kgCODadded, respectively. The AFBR presented a stable operation and excellent performance, indicated by the increased methane production rate at each shortened HRT. Besides, recirculation of the AFBR effluent to the CSTR was effective in providing alkalinity, maintaining the pH in optimal ranges (5.0-5.3) for the hydrogen producing bacteria.

  17. Effects of casting speed on microstructure and segregation of electromagnetically stirred Aluminum alloy in continuous casting process

    Institute of Scientific and Technical Information of China (English)

    LEE Dock-Young; KANG Suk-Won; CHO Duck-Ho; KIM Ki-Bae

    2006-01-01

    Recently, a semi-solid metal processing has been acknowledged as a cost-effective technique to be able to manufacture high quality product for the transportation industry.In this study a hypo-eutectic Al alloy was fabricated by means of an electromagnetic stirrer in continuous casting process and the microstructural change during solidification due to a fluid flow by electromagnetic stirring was examined.Due to the forced fluid flow during solidification a dendritic phase of primary α phase of Al alloy was turned into a globular phase, which can make the Al alloy get a thixotropic behavior in the semi-solid region.In order to establish the quantitative relationship between microstructure and the process parameters, the morphology shape, a silicon distribution and a size of primary α phase were observed according to casting speed in continuous casting machine.The primary α phase was turned into the degenerate dendrites approaching a spherical configuration with increasing casting speed.The fine-grained and equiaxed microstructure appeared at higher casting speed.A segregation behavior of Si element was declined with increasing casting speed and a very uniform distribution of Si element was observed on the billet at a casting speed of 600 mm·min-1.A thickness of the solidifying shell of the billet was shortened with increasing the casting speed.

  18. Dynamic nonlinear feedback for temperature control of continuous stirred reactor with complex behavior

    OpenAIRE

    Pablo A. López Pérez; Ricardo Aguilar‐López

    2009-01-01

    The main objective of this work is to present an alternative methodology for the design of a class of integral high order slidingmodecontroller applied to a class of continuous chemical reactor with complex behavior for temperature tracking purposes.The proposed design is based on the differential geometry framework, where the named reaching trajectory contains a highorder sliding mode term in order to diminish chattering. Considering that the proposed technique is model based, an observerbas...

  19. Dynamic nonlinear feedback for temperature control of continuous stirred reactor with complex behavior

    Directory of Open Access Journals (Sweden)

    Pablo A. López Pérez

    2009-08-01

    Full Text Available The main objective of this work is to present an alternative methodology for the design of a class of integral high order slidingmodecontroller applied to a class of continuous chemical reactor with complex behavior for temperature tracking purposes.The proposed design is based on the differential geometry framework, where the named reaching trajectory contains a highorder sliding mode term in order to diminish chattering. Considering that the proposed technique is model based, an observerbaseduncertainty estimator is coupled, which provides robustness against model uncertainties and noisy measurements.Numerical simulations are performed in order to show the capacities of the proposed controller, which is compared with othernonlinear methodologies.

  20. Reuse of drinking water treatment residuals in a continuous stirred tank reactor for phosphate removal from urban wastewater.

    Science.gov (United States)

    Bai, Leilei; Wang, Changhui; Pei, Yuansheng; Zhao, Jinbo

    2014-01-01

    This work proposed a new approach of reusing drinking water treatment residuals (WTR) in a continuous stirred tank reactor (CSTR) to remove phosphate (P) from urban wastewater. The results revealed that the P removal efficiency of the WTR was more than 94% for urban wastewater, in the condition of initial P concentration (P0) of 10 mg L⁻¹, hydraulic retention time (HRT) of 2 h and WTR dosage (M0) of 10 g L⁻¹. The P mass transfer from the bulk to the solid-liquid interface in the CSTR system increased at lower P0, higher M0 and longer HRT. The P adsorption capacity of WTR from urban wastewater was comparable to that of the 201 × 4 resin and unaffected by ions competition. Moreover, WTR had a limited effect on the metals' (Fe, Al, Zn, Cu, Mn and Ni) concentrations of the urban wastewater. Based on the principle of waste recycling, the reuse of WTR in CSTR is a promising alternative technology for P removal from urban wastewater.

  1. Entropy production in a chemical system involving an autocatalytic reaction in an isothermal, continuous stirred tank reactor

    Science.gov (United States)

    Yoshida, Nobuo

    1990-02-01

    The rate of entropy production due to chemical reaction is calculated for various combinations of parameter values in the cubic autocatalator model in an isothermal, continuous stirred tank reactor (CSTR) proposed by Gray and Scott and by Escher and Ross. Values of the entropy production averaged over periods of limit cycle oscillations are compared with those in coexistent unstable stationary states. It is found that in ranges of the residence time over which there are limit cycles, the entropy production in coexisting stationary states increases as the residence time is shortened, i.e., as the system is removed farther from thermodynamic equilibrium. The average entropy production over a limit cycle is less than that in the corresponding stationary state over wide ranges of parameter values, but not necessarily for the whole oscillatory region. More specifically, the former inequality always prevails in ranges where the entropy production of stationary states is larger, i.e., the residence time is shorter, but in some cases the inequality is reversed in ranges of lower magnitudes of the entropy production.

  2. Efficient azo dye decolorization in a continuous stirred tank reactor (CSTR) with built-in bioelectrochemical system.

    Science.gov (United States)

    Cui, Min-Hua; Cui, Dan; Gao, Lei; Cheng, Hao-Yi; Wang, Ai-Jie

    2016-10-01

    A continuous stirred tank reactor with built-in bioelectrochemical system (CSTR-BES) was developed for azo dye Alizarin Yellow R (AYR) containing wastewater treatment. The decolorization efficiency (DE) of the CSTR-BES was 97.04±0.06% for 7h with sludge concentration of 3000mg/L and initial AYR concentration of 100mg/L, which was superior to that of the sole CSTR mode (open circuit: 54.87±4.34%) and the sole BES mode (without sludge addition: 91.37±0.44%). The effects of sludge concentration and sodium acetate (NaAc) concentration on azo dye decolorization were investigated. The highest DE of CSTR-BES for 4h was 87.66±2.93% with sludge concentration of 12,000mg/L, NaAc concentration of 2000mg/L and initial AYR concentration of 100mg/L. The results in this study indicated that CSTR-BES could be a practical strategy for upgrading conventional anaerobic facilities against refractory wastewater treatment.

  3. Application of a continuously stirred tank bioreactor (CSTR) for bioremediation of hydrocarbon-rich industrial wastewater effluents.

    Science.gov (United States)

    Gargouri, Boutheina; Karray, Fatma; Mhiri, Najla; Aloui, Fathi; Sayadi, Sami

    2011-05-15

    A continuously stirred tank bioreactor (CSTR) was used to optimize feasible and reliable bioprocess system in order to treat hydrocarbon-rich industrial wastewaters. A successful bioremediation was developed by an efficient acclimatized microbial consortium. After an experimental period of 225 days, the process was shown to be highly efficient in decontaminating the wastewater. The performance of the bioaugmented reactor was demonstrated by the reduction of COD rates up to 95%. The residual total petroleum hydrocarbon (TPH) decreased from 320 mg TPH l(-1) to 8 mg TPH l(-1). Analysis using gas chromatography-mass spectrometry (GC-MS) identified 26 hydrocarbons. The use of the mixed cultures demonstrated high degradation performance for hydrocarbons range n-alkanes (C10-C35). Six microbial isolates from the CSTR were characterized and species identification was confirmed by sequencing the 16S rRNA genes. The partial 16S rRNA gene sequences demonstrated that 5 strains were closely related to Aeromonas punctata (Aeromonas caviae), Bacillus cereus, Ochrobactrum intermedium, Stenotrophomonas maltophilia and Rhodococcus sp. The 6th isolate was affiliated to genera Achromobacter. Besides, the treated wastewater could be considered as non toxic according to the phytotoxicity test since the germination index of Lepidium sativum ranged between 57 and 95%. The treatment provided satisfactory results and presents a feasible technology for the treatment of hydrocarbon-rich wastewater from petrochemical industries and petroleum refineries.

  4. Quantifying the Reactive Uptake of OH by Organic Aerosols in aContinuous Flow Stirred Tank Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Che, Dung L.; Smith, Jared D.; Leone, Stephen R.; Ahmed, Musahid; Wilson, Kevin R.

    2009-03-01

    Here we report a new method for measuring the heterogeneous chemistry of submicron organic aerosol particles using a continuous flow stirred tank reactor. This approach is designed to quantify the real time heterogeneous kinetics, using a relative rate method, under conditions of low oxidant concentration and long reaction times that more closely mimic the real atmosphere. A general analytical expression, which couples the aerosol chemistry with the flow dynamics in the chamber is developed and applied to the heterogeneous oxidation of squalane particles by hydroxyl radicals (OH) in the presence of O2. The particle phase reaction is monitored via photoionization aerosol mass spectrometry and yields a reactive uptake coefficient of 0.51+-0.10, using OH concentrations of 1-7x108 molec cdot cm-3 and reaction times of 1.5+-3 hours. This uptake coefficient is larger than that found for the reaction carried out under high OH concentrations (~;;1x1010 molec cdot cm-3) and short reaction times in a flow tube reactor. This difference suggests that oxidant concentration and reaction time are not interchangeable quantities in reactions of organic aerosols with radicals. In general, this approach provides a new way to examine how the chemical aging of organic particles measured at short reaction times and high oxidant concentrations in flow tubes might differ from the long reaction times and low oxidant levels found in the real atmosphere.

  5. Application of a continuously stirred tank bioreactor (CSTR) for bioremediation of hydrocarbon-rich industrial wastewater effluents

    Energy Technology Data Exchange (ETDEWEB)

    Gargouri, Boutheina; Karray, Fatma; Mhiri, Najla; Aloui, Fathi [Laboratoire des Bioprocedes Environnementaux, Pole d' Excellence Regional AUF-LBPE, Centre de Biotechnologie de Sfax, Universite de Sfax, BP 1117, 3018 Sfax (Tunisia); Sayadi, Sami, E-mail: sami.sayadi@cbs.rnrt.tn [Laboratoire des Bioprocedes Environnementaux, Pole d' Excellence Regional AUF-LBPE, Centre de Biotechnologie de Sfax, Universite de Sfax, BP 1117, 3018 Sfax (Tunisia)

    2011-05-15

    A continuously stirred tank bioreactor (CSTR) was used to optimize feasible and reliable bioprocess system in order to treat hydrocarbon-rich industrial wastewaters. A successful bioremediation was developed by an efficient acclimatized microbial consortium. After an experimental period of 225 days, the process was shown to be highly efficient in decontaminating the wastewater. The performance of the bioaugmented reactor was demonstrated by the reduction of COD rates up to 95%. The residual total petroleum hydrocarbon (TPH) decreased from 320 mg TPH l{sup -1} to 8 mg TPH l{sup -1}. Analysis using gas chromatography-mass spectrometry (GC-MS) identified 26 hydrocarbons. The use of the mixed cultures demonstrated high degradation performance for hydrocarbons range n-alkanes (C10-C35). Six microbial isolates from the CSTR were characterized and species identification was confirmed by sequencing the 16S rRNA genes. The partial 16S rRNA gene sequences demonstrated that 5 strains were closely related to Aeromonas punctata (Aeromonas caviae), Bacillus cereus, Ochrobactrum intermedium, Stenotrophomonas maltophilia and Rhodococcus sp. The 6th isolate was affiliated to genera Achromobacter. Besides, the treated wastewater could be considered as non toxic according to the phytotoxicity test since the germination index of Lepidium sativum ranged between 57 and 95%. The treatment provided satisfactory results and presents a feasible technology for the treatment of hydrocarbon-rich wastewater from petrochemical industries and petroleum refineries.

  6. Reuse of drinking water treatment residuals in a continuous stirred tank reactor for phosphate removal from urban wastewater.

    Science.gov (United States)

    Bai, Leilei; Wang, Changhui; Pei, Yuansheng; Zhao, Jinbo

    2014-01-01

    This work proposed a new approach of reusing drinking water treatment residuals (WTR) in a continuous stirred tank reactor (CSTR) to remove phosphate (P) from urban wastewater. The results revealed that the P removal efficiency of the WTR was more than 94% for urban wastewater, in the condition of initial P concentration (P0) of 10 mg L⁻¹, hydraulic retention time (HRT) of 2 h and WTR dosage (M0) of 10 g L⁻¹. The P mass transfer from the bulk to the solid-liquid interface in the CSTR system increased at lower P0, higher M0 and longer HRT. The P adsorption capacity of WTR from urban wastewater was comparable to that of the 201 × 4 resin and unaffected by ions competition. Moreover, WTR had a limited effect on the metals' (Fe, Al, Zn, Cu, Mn and Ni) concentrations of the urban wastewater. Based on the principle of waste recycling, the reuse of WTR in CSTR is a promising alternative technology for P removal from urban wastewater. PMID:25176310

  7. Biohydrogen and Bioethanol Production from Biodiesel-Based Glycerol by Enterobacter aerogenes in a Continuous Stir Tank Reactor.

    Science.gov (United States)

    Jitrwung, Rujira; Yargeau, Viviane

    2015-05-11

    Crude glycerol from the biodiesel manufacturing process is being produced in increasing quantities due to the expanding number of biodiesel plants. It has been previously shown that, in batch mode, semi-anaerobic fermentation of crude glycerol by Enterobacter aerogenes can produce biohydrogen and bioethanol simultaneously. The present study demonstrated the possible scaling-up of this process from small batches performed in small bottles to a 3.6-L continuous stir tank reactor (CSTR). Fresh feed rate, liquid recycling, pH, mixing speed, glycerol concentration, and waste recycling were optimized for biohydrogen and bioethanol production. Results confirmed that E. aerogenes uses small amounts of oxygen under semi-anaerobic conditions for growth before using oxygen from decomposable salts, mainly NH4NO3, under anaerobic condition to produce hydrogen and ethanol. The optimal conditions were determined to be 500 rpm, pH 6.4, 18.5 g/L crude glycerol (15 g/L glycerol) and 33% liquid recycling for a fresh feed rate of 0.44 mL/min. Using these optimized conditions, the process ran at a lower media cost than previous studies, was stable after 7 days without further inoculation and resulted in yields of 0.86 mol H2/mol glycerol and 0.75 mol ethanol/mole glycerol.

  8. Biohydrogen and Bioethanol Production from Biodiesel-Based Glycerol by Enterobacter aerogenes in a Continuous Stir Tank Reactor

    Directory of Open Access Journals (Sweden)

    Rujira Jitrwung

    2015-05-01

    Full Text Available Crude glycerol from the biodiesel manufacturing process is being produced in increasing quantities due to the expanding number of biodiesel plants. It has been previously shown that, in batch mode, semi-anaerobic fermentation of crude glycerol by Enterobacter aerogenes can produce biohydrogen and bioethanol simultaneously. The present study demonstrated the possible scaling-up of this process from small batches performed in small bottles to a 3.6-L continuous stir tank reactor (CSTR. Fresh feed rate, liquid recycling, pH, mixing speed, glycerol concentration, and waste recycling were optimized for biohydrogen and bioethanol production. Results confirmed that E. aerogenes uses small amounts of oxygen under semi-anaerobic conditions for growth before using oxygen from decomposable salts, mainly NH4NO3, under anaerobic condition to produce hydrogen and ethanol. The optimal conditions were determined to be 500 rpm, pH 6.4, 18.5 g/L crude glycerol (15 g/L glycerol and 33% liquid recycling for a fresh feed rate of 0.44 mL/min. Using these optimized conditions, the process ran at a lower media cost than previous studies, was stable after 7 days without further inoculation and resulted in yields of 0.86 mol H2/mol glycerol and 0.75 mol ethanol/mole glycerol.

  9. A continuous stirred hydrogen-based polyvinyl chloride membrane biofilm reactor for the treatment of nitrate contaminated drinking water.

    Science.gov (United States)

    Xia, Siqing; Zhang, YanHao; Zhong, FoHua

    2009-12-01

    A continuous stirred hydrogen-based polyvinyl chloride (PVC) membrane biofilm reactor (MBfR) was investigated to remove nitrate from the drinking water. The reactor was operated over 100 days, and the result showed that the average nitrate denitrification rate of 1.2 g NO(3)(-)-N/m(2) d and the total nitrogen (TN) removal of 95.1% were achieved with the influent nitrate concentration of 50 mg NO(3)(-)-N/L and the hydrogen pressure of 0.05 MPa. Under the same conditions, the average rate of hydrogen utilization by biofilm was 0.031 mg H(2)/cm(2) d, which was sufficient to remove 50 mg NO(3)(-)-N/L from the contaminated water with the effluent nitrate and nitrite concentrations below drinking water limit values. The average hydrogen utilization efficiency was achieved as high as 99.5%. Flux analysis demonstrated that, compared to sulfate reduction, nitrate reduction competed more strongly for hydrogen electron, and obtained more electrons in high influent nitrate loading.

  10. Fermentative hydrogen production from beet sugar factory wastewater treatment in a continuous stirred tank reactor using anaerobic mixed consortia

    Institute of Scientific and Technical Information of China (English)

    Gefu ZHU; Chaoxiang LIU; Jianzheng LI; Nanqi REN; Lin LIU; Xu HUANG

    2013-01-01

    A low pH, ethanol-type fermentation process was evaluated for wastewater treatment and bio-hydrogen production from acidic beet sugar factory wastewater in a continuous stirred tank reactor (CSTR) with an effective volume of 9.6 L by anaerobic mixed cultures in this present study. After inoculating with aerobic activated sludge and operating at organic loading rate (OLR) of 12 kgCOD·m-3·d-1, HRT of 8h, and temperature of 35℃ for 28 days, the CSTR achieved stable ethanol-type fermentation. When OLR was further increased to 18 kgCOD·m-3·d-1, on the 53rd day, ethanol-type fermentation dominant microflora was enhanced. The liquid fermentation products, including volatile fatty acids (VFAs) and ethanol, stabilized at 1493mg·L-1 in the bioreactor. Effluent pH, oxidation-reduction potential (ORP), and alkalinity ranged at 4.1-4.5, -250-(-290) mV, and 230-260mgCaCO3·L-1. The specific hydrogen production rate of anaerobic activated sludge was 0.1 L'gMLVSS-1· d-1 and the COD removal efficiency was 45%. The experimental results showed that the CSTR system had good operation stability and microbial activity, which led to high substrate conversion rate and hydrogen production ability.

  11. Simultaneous removal of selected oxidized contaminants in groundwater using a continuously stirred hydrogen-based membrane biofilm reactor

    Institute of Scientific and Technical Information of China (English)

    Siqing Xia; Jun Liang; Xiaoyin Xu; Shuang Shen

    2013-01-01

    A laboratory trial was conducted for evaluating the capability of a continuously stirred hydrogen-based membrane biofilm reactor to simultaneously reduce nitrate (NO3--N),sulfate (SO42-),bromate (BrO3-),hexavalent chromium (Cr(Ⅵ)) and parachloronitrobenzene (p-CNB).The reactor contained two bundles of hollow fiber membranes functioning as an autotrophic biofilm carrier and hydrogen pipe as well.On the condition that hydrogen was supplied as electron donor and diffused into water through membrane pores,autohydrogenotrophic bacteria were capable of reducing contaminants to forms with lower toxicity.Reduction occurred within 1 day and removal fluxes for NO3--N,SO42-,BrO3-,Cr(Ⅵ),and p-CNB reached 0.641,2.396,0.008,0.016 and 0.031 g/(day.m2),respectively after 112 days of continuous operation.Except for the fact that sulfate was 37% removed under high surface loading,the other four contaminants were reduced by over 95%.The removal flux comparison between phases varying in surface loading and H2 pressure showed that decreasing surface loading or increasing H2 pressure would promote removal flux.Competition for electrons occurred among the five contaminants.Electron-equivalent flux analysis showed that the amount of utilized hydrogen was mainly controlled by NO2--N and SO42-reduction,which accounted for over 99% of the electron flux altogether.It also indicated the electron acceptor order,showing that nitrate was the most prior electron acceptor while sulfate was the second of the five contaminants.

  12. Conversion-space time profiles of stirred tank reactors continuously fed with reactants and catalyst under conditions of strong catalyst deactivation

    OpenAIRE

    Flaschel, E.; Margot, A; Dohmen, M; Renken, A.

    1995-01-01

    Feeding continuously operated stirred tank reactors with reactants and homogeneous catalysts subject to inactivation will usually lead to a limited substrate conversion with increasing space time. However, it is shown that a max. of conversion may be obsd. under certain circumstances. Guided by exptl. evidence, the theor. background is discussed for identifying reaction systems for which such conversion maxima at distinct space times may be obtained. This phenomenon may be obsd. only if the c...

  13. Jet-Stirred Reactors

    OpenAIRE

    Herbinet, Olivier; Guillaume, Dayma

    2013-01-01

    The jet-stirred reactor is a type of ideal continuously stirred-tank reactor which is well suited for gas phase kinetic studies. It is mainly used to study the oxidation and the pyrolysis of hydrocarbon and oxygenated fuels. These studies consist in recording the evolution of the conversion of the reactants and of the mole fractions of reaction products as a function of different parameters such as reaction temperature, residence time, pressure and composition of the inlet gas. Gas chromatogr...

  14. A laboratory and pilot plant scaled continuous stirred reactor separator for the production of ethanol from sugars, corn grits/starch or biomass streams

    Energy Technology Data Exchange (ETDEWEB)

    Dale, M.C.; Lei, Shuiwang; Zhou, Chongde

    1995-10-01

    An improved bio-reactor has been developed to allow the high speed, continues, low energy conversion of various substrates to ethanol. The Continuous Stirred Reactor Separator (CSRS) incorporates gas stripping of the ethanol using a recalculating gas stream between cascading stirred reactors in series. We have operated a 4 liter lab scale unit, and built and operated a 24,000 liter pilot scale version of the bioreactor. High rates of fermentation are maintained in the reactor stages using a highly flocculent yeast strain. Ethanol is recovered from the stripping gas using a hydrophobic solvent absorber (isothermal), after which the gas is returned to the bioreactor. Ethanol can then be removed from the solvent to recover a highly concentrated ethanol product. We have applied the lab scale CSRS to sugars (glucose/sucrose), molasses, and raw starch with simultaneous saccharification and fermentation of the starch granules (SSF). The pilot scale CSRS has been operated as a cascade reactor using dextrins as a feed. Operating data from both the lab and pilot scale CSRS are presented. Details of how the system might be applied to cellulosics, with some preliminary data are also given.

  15. Analysis on the Deflection Angle of Columnar Dendrites of Continuous Casting Steel Billets Under the Influence of Mold Electromagnetic Stirring

    Science.gov (United States)

    Wang, Xincheng; Wang, Shengqian; Zhang, Lifeng; Sridhar, Seetharaman; Conejo, Alberto; Liu, Xuefeng

    2016-11-01

    In the current study, the deflection angle of columnar dendrites on the cross section of steel billets under mold electromagnetic stirring (M-EMS) was observed. A mathematical model was developed to define the effect of M-EMS on fluid flow and then to analyze the relationship between flow velocities and deflection angle. The model was validated using experimental data that was measured with a Tesla meter on magnetic intensity. By coupling the numerical results with the experimental data, it was possible to define a relationship between the velocities of the fluid with the deflection angle of high-carbon steel. The deflection angle of high-carbon steel reached maximum values from 18 to 23 deg for a velocity from 0.35 to 0.40 m/s. The deflection angles of low-carbon steel under different EM parameters were discussed. The deflection angle of low-carbon steel was increased as the magnetic intensity, EM force, and velocity of molten steel increased.

  16. Effect of noise correlation on noise-induced oscillation frequency in the photosensitive Belousov-Zhabotinsky reaction in a continuous stirred tank reactor.

    Science.gov (United States)

    Simakov, David S A; Pérez-Mercader, Juan

    2013-12-27

    We report on the experimental study of noise-induced oscillations in the photosensitive Ru(bpy)3(2+)-catalyzed Belousov-Zhabotinsky reaction in a continuous stirred tank reactor (CSTR). In the absence of deterministic oscillations and any external periodic forcing, oscillations appear when the system is perturbed by stochastic fluctuations in light irradiation with sufficiently high amplitude in the vicinity of the bifurcation point. The frequency distribution of the noise-induced oscillations is strongly affected by noise correlation. There is a shift of the noise-induced oscillation frequency toward higher frequencies for an intermediate range of the noise correlation exponent, indicating the occurrence of coherence resonance. Our findings indicate that, in principle, noise correlation can be used to direct chemical reactions toward certain behavior.

  17. 基于MLD模型的CSTR建模和控制%Modeling and Control of a Continuous Stirred Tank Reactor Based on a Mixed Logical Dynamical Model

    Institute of Scientific and Technical Information of China (English)

    杜静静; 宋春跃; 李平

    2007-01-01

    A novel control strategy for a continuous stirred tank reactor (CSTR) system, which has the typical characteristic of strongly pronounced nonlinearity, multiple operating points, and a wide operating range, is initiated from the point of hybrid systems. The proposed scheme makes full use of the modeling power of mixed logical dynamical (MLD) systems to describe the highly nonlinear dynamics and multiple operating points in a unified framework as a hybrid system, and takes advantage of the good control quality of model predictive control (MPC)to design a controller. Thus, this approach avoids oscillation during switching between sub-systems, helps to relieve shaking in transition, and augments the stability robustness of the whole system, and finally achieves optimal (i.e.fast and smooth) transition between operating points. The simulation results demonstrate that the presented approach has a satisfactory performance.

  18. Coproduction of hydrogen and methane via anaerobic fermentation of cornstalk waste in continuous stirred tank reactor integrated with up-flow anaerobic sludge bed.

    Science.gov (United States)

    Cheng, Xi-Yu; Li, Qian; Liu, Chun-Zhao

    2012-06-01

    A 10 L continuous stirred tank reactor (CSTR) system was developed for a two-stage hydrogen fermentation process with an integrated alkaline treatment. The maximum hydrogen production rate reached 218.5 mL/L h at a cornstalk concentration of 30 g/L, and the total hydrogen yield and volumetric hydrogen production rate reached 58.0 mL/g-cornstalk and 0.55-0.57 L/L d, respectively. A 10 L up-flow anaerobic sludge bed (UASB) was used for continuous methane fermentation of the effluents obtained from the two-stage hydrogen fermentation. At the optimal organic loading rate of 15.0 g-COD/Ld, the COD removal efficiency and volumetric biogas production rate reached 83.3% and 4.6L/Ld, respectively. Total methane yield reached 200.9 mL/g-cornstalk in anaerobic fermentation with the effluents and alkaline hydrolysate. As a result, the total energy recovery by coproduction of hydrogen and methane with anaerobic fermentation of cornstalk reached 67.1%.

  19. Anaerobic treatment of cassava stillage for hydrogen and methane production in continuously stirred tank reactor (CSTR) under high organic loading rate (OLR)

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Gang; Xie, Li; Zou, Zhonghai; Wang, Wen; Zhou, Qi [Key Laboratory of Yangtze River Water Environment, Ministry of Education (Tongji University), UNEP-Tongji, Tongji University, Siping Road No. 1239, Shanghai 200092 (China); Shim, Hojae [Department of Civil and Environmental Engineering, Faculty of Science and Technology, University of Macau, Macau SAR 999078 (China)

    2010-11-15

    Anaerobic hydrogen and methane production from cassava stillage in continuously stirred tank reactor (CSTR) were investigated in this study. Results showed that the heat-pretreatment of inoculum did not enhance hydrogen yield compared to raw inoculum under mesophilic condition after continuous operation. However, the hydrogen yield increased from about 14 ml H{sub 2}/gVS under mesophilic condition to 69.6 ml H{sub 2}/gVS under thermophilic condition due to the decrease of propionate concentration and inhibition of homoacetogens. Therefore, temperature was demonstrated to be more important than pretreatment of inoculum to enhance the hydrogen production. Under high organic loading rate (OLR) (>10 gVS/(L.d)), the two-phase thermophilic CSTR for hydrogen and methane production was stable with hydrogen and methane yields of 56.6 mlH{sub 2}/gVS and 249 mlCH{sub 4}/gVS. The one-phase thermophilic CSTR for methane production failed due to the accumulation of both acetate and propionate, leading to the pH lower than 6. Instead of propionate alone, the accumulations of both acetate and propionate were found to be related to the breakdown of methane reactor. (author)

  20. Reactor models for a series of continuous stirred tank reactors with a gas-liquid-solid leaching system: Part I. Surface reaction control

    Science.gov (United States)

    Papangelakis, V. G.; Demopoulos, G. P.

    1992-12-01

    In this three-part series of articles, comprehensive three-phase steady-state hydrometallurgical reactor models of the continuous stirred tank reactor (CSTR) type are developed and applied to a commercial (pressure oxidation) process. The key features of the developed models are the coupling of both mass and heat balance equations, the description of the nonisothermal performance (autothermal) of a multistage continuous reactor, and the treatment of multimineral feed materials. The model considers only the oxidation reactions, because they mainly affect the thermal balance of the reactor. The stoichiometries and intrinsic kinetics of the heterogeneous leaching reactions, which are established via independent experiments, are the foundation of the developed model. A three-phase (g-l-s) reaction process might be controlled by either surface reaction control, i.e., the rate(s) of the heterogeneous leaching reaction(s), or by gas transfer control, i.e., the rate of transfer of the gaseous reactant into the liquid phase. In the present article (Part I), the case of surface reaction control is treated. The article addresses, in particular, the following topics: (1) it outlines the basic mass and heat balance equations which describe the performance of a multistage leaching reactor; (2) it presents a continuous function to describe the particle size distribution of the feed; and (3) it develops, on the basis of probability theory, number- and mass-particle size density functions which give the size distribution of particle populations reacting according to the surface reaction control-shrinking core model.

  1. Hydrolysis-acidogenesis of food waste in solid-liquid-separating continuous stirred tank reactor (SLS-CSTR) for volatile organic acid production.

    Science.gov (United States)

    Karthikeyan, Obulisamy Parthiba; Selvam, Ammaiyappan; Wong, Jonathan W C

    2016-01-01

    The use of conventional continuous stirred tank reactor (CSTR) can affect the methane (CH4) recovery in a two-stage anaerobic digestion of food waste (FW) due to carbon short circuiting in the hydrolysis-acidogenesis (Hy-Aci) stage. In this research, we have designed and tested a solid-liquid-separating CSTR (SLS-CSTR) for effective Hy-Aci of FW. The working conditions were pH 6 and 9 (SLS-CSTR-1 and -2, respectively); temperature-37°C; agitation-300rpm; and organic loading rate (OLR)-2gVSL(-1)day(-1). The volatile fatty acids (VFA), enzyme activities and bacterial population (by qPCR) were determined as test parameters. Results showed that the Hy-Aci of FW at pH 9 produced ∼35% excess VFA as compared to that at pH 6, with acetic and butyric acids as major precursors, which correlated with the high enzyme activities and low lactic acid bacteria. The design provided efficient solid-liquid separation there by improved the organic acid yields from FW.

  2. Determination of Noncovalent Binding Using a Continuous Stirred Tank Reactor as a Flow Injection Device Coupled to Electrospray Ionization Mass Spectrometry

    Science.gov (United States)

    Santos, Inês C.; Waybright, Veronica B.; Fan, Hui; Ramirez, Sabra; Mesquita, Raquel B. R.; Rangel, António O. S. S.; Fryčák, Petr; Schug, Kevin A.

    2015-07-01

    Described is a new method based on the concept of controlled band dispersion, achieved by hyphenating flow injection analysis with ESI-MS for noncovalent binding determinations. A continuous stirred tank reactor (CSTR) was used as a FIA device for exponential dilution of an equimolar host-guest solution over time. The data obtained was treated for the noncovalent binding determination using an equimolar binding model. Dissociation constants between vancomycin and Ac-Lys(Ac)-Ala-Ala-OH peptide stereoisomers were determined using both the positive and negative ionization modes. The results obtained for Ac- L-Lys(Ac)- D-Ala- D-Ala (a model for a Gram-positive bacterial cell wall) binding were in reasonable agreement with literature values made by other mass spectrometry binding determination techniques. Also, the developed method allowed the determination of dissociation constants for vancomycin with Ac- L-Lys(Ac)- D-Ala- L-Ala, Ac- L-Lys(Ac)- L-Ala- D-Ala, and Ac- L-Lys(Ac)- L-Ala- L-Ala. Although some differences in measured binding affinities were noted using different ionization modes, the results of each determination were generally consistent. Differences are likely attributable to the influence of a pseudo-physiological ammonium acetate buffer solution on the formation of positively- and negatively-charged ionic complexes.

  3. Comparison of bioleaching of heavy metals from municipal sludge using indigenous sulfur and iron-oxidizing microorganisms: continuous stirred tank reactor studies.

    Science.gov (United States)

    Pathak, Ashish; Kothari, Richa; Dastidar, M G; Sreekrishnan, T R; Kim, Dong J

    2014-01-01

    A comparative study was undertaken using indigenous sulfur-oxidizing microorganisms and iron-oxidizing microorganisms in separate 12 litre continuous stirred tank reactors (CSTRs) for solubilization of heavy metals from anaerobically digested sewage sludge. The CSTRs were operated at hydraulic retention times (HRTs) ranging from 4 to 10 days using sewage sludge feed having near neutral pH. The pH, oxidation-reduction potential (ORP) and solubilization efficiency of metals were found to be highly dependent on HRT and an increase in HRT led to higher solubilization of metals in both the CSTRs. In both the CSTRs, the CSTR operated with sulfur-oxidizing microorganisms at an HRT of 8 days was found to be optimum in solubilizing 58% Cu, 52% Ni, 72% Zn and 43% Cu from the sludge. The nutrient value, nitrogen and phosphorus of bioleached sludge was also conserved (<20% loss) at 8 days HRT. The metals fractionation study conducted using BCR sequential extraction procedure suggested that most of the metals remaining in the bioleached sludge were in the more stable fractions (F3 and F4) and, therefore, can be safely apply as a fertilizer on land.

  4. Comparison of bioleaching of heavy metals from municipal sludge using indigenous sulfur and iron-oxidizing microorganisms: continuous stirred tank reactor studies.

    Science.gov (United States)

    Pathak, Ashish; Kothari, Richa; Dastidar, M G; Sreekrishnan, T R; Kim, Dong J

    2014-01-01

    A comparative study was undertaken using indigenous sulfur-oxidizing microorganisms and iron-oxidizing microorganisms in separate 12 litre continuous stirred tank reactors (CSTRs) for solubilization of heavy metals from anaerobically digested sewage sludge. The CSTRs were operated at hydraulic retention times (HRTs) ranging from 4 to 10 days using sewage sludge feed having near neutral pH. The pH, oxidation-reduction potential (ORP) and solubilization efficiency of metals were found to be highly dependent on HRT and an increase in HRT led to higher solubilization of metals in both the CSTRs. In both the CSTRs, the CSTR operated with sulfur-oxidizing microorganisms at an HRT of 8 days was found to be optimum in solubilizing 58% Cu, 52% Ni, 72% Zn and 43% Cu from the sludge. The nutrient value, nitrogen and phosphorus of bioleached sludge was also conserved (sequential extraction procedure suggested that most of the metals remaining in the bioleached sludge were in the more stable fractions (F3 and F4) and, therefore, can be safely apply as a fertilizer on land. PMID:24117088

  5. Hydrolysis-acidogenesis of food waste in solid-liquid-separating continuous stirred tank reactor (SLS-CSTR) for volatile organic acid production.

    Science.gov (United States)

    Karthikeyan, Obulisamy Parthiba; Selvam, Ammaiyappan; Wong, Jonathan W C

    2016-01-01

    The use of conventional continuous stirred tank reactor (CSTR) can affect the methane (CH4) recovery in a two-stage anaerobic digestion of food waste (FW) due to carbon short circuiting in the hydrolysis-acidogenesis (Hy-Aci) stage. In this research, we have designed and tested a solid-liquid-separating CSTR (SLS-CSTR) for effective Hy-Aci of FW. The working conditions were pH 6 and 9 (SLS-CSTR-1 and -2, respectively); temperature-37°C; agitation-300rpm; and organic loading rate (OLR)-2gVSL(-1)day(-1). The volatile fatty acids (VFA), enzyme activities and bacterial population (by qPCR) were determined as test parameters. Results showed that the Hy-Aci of FW at pH 9 produced ∼35% excess VFA as compared to that at pH 6, with acetic and butyric acids as major precursors, which correlated with the high enzyme activities and low lactic acid bacteria. The design provided efficient solid-liquid separation there by improved the organic acid yields from FW. PMID:26512860

  6. Coupling of acrylic dyeing wastewater treatment by heterogeneous Fenton oxidation in a continuous stirred tank reactor with biological degradation in a sequential batch reactor.

    Science.gov (United States)

    Esteves, Bruno M; Rodrigues, Carmen S D; Boaventura, Rui A R; Maldonado-Hódar, F J; Madeira, Luís M

    2016-01-15

    This work deals with the treatment of a recalcitrant effluent, from the dyeing stage of acrylic fibres, by combination of the heterogeneous Fenton's process in a continuous stirred tank reactor (CSTR) with biological degradation in a sequential batch reactor (SBR). Three different catalysts (a commercial Fe/ZSM-5 zeolite and two distinct Fe-containing activated carbons - ACs - prepared by wet impregnation of iron acetate and iron nitrate) were employed on the Fenton's process, and afterwards a parametric study was carried out to determine the effect of the main operating conditions, namely the hydrogen peroxide feed concentration, temperature and contact time. Under the best operating conditions found, using the activated carbon impregnated with iron nitrate, 62.7% of discolouration and 39.9% of total organic carbon (TOC) reduction were achieved, at steady-state. Furthermore, a considerable increase in the effluent's biodegradability was attained (BOD5:COD ratio increased from toxicity (from 92.1 to 94.0% of Vibrio fischeri inhibition down to 6.9-9.9%). This allowed the application of the subsequent biological degradation stage. The combination of the two processes provided a treated effluent that clearly complies with the legislated discharge limits. It was also found that the iron leaching from the three catalysts tested was very small in all runs, a crucial factor for the stability and long-term use of such materials. PMID:26513317

  7. Performance comparison of a continuous-flow stirred-tank reactor and an anaerobic sequencing batch reactor for fermentative hydrogen production depending on substrate concentration.

    Science.gov (United States)

    Kim, S-H; Han, S-K; Shin, H-S

    2005-01-01

    This study was conducted to compare the performance of a continuous-flow stirred-tank reactor (CSTR) and an anaerobic sequencing batch reactor (ASBR) for fermentative hydrogen production at various substrate concentrations. Heat-treated anaerobic sludge was utilized as an inoculum, and hydraulic retention time (HRT) for each reactor was maintained at 12 h. At the influent sucrose concentration of 5 g COD/L, start-up was not successful in both reactors. The CSTR, which was started-up at 10 g COD/L, showed stable hydrogen production at the influent sucrose concentrations of 10-60 g COD/L during 203 days. Hydrogen production was dependent on substrate concentration, resulting in the highest performance at 30 g COD/L. At the lower substrate concentration, the hydrogen yield (based on hexose consumed) decreased with biomass reduction and changes in fermentation products. At the higher substrate concentration, substrate inhibition on biomass growth caused the decrease of carbohydrate degradation and hydrogen yield (based on hexose added). The ASBR showed higher biomass concentration and carbohydrate degradation efficiency than the CSTR, but hydrogen production in the ASBR was less effective than that in the CSTR at all the substrate concentrations.

  8. Bistability in isothermal photochemical systems: The A ⇆ h nu B --> h nu C reaction in a continuous flow stirred tank reactor

    Science.gov (United States)

    Laplante, J. P.; Lavabre, D.; Micheau, J. C.

    1988-08-01

    In this paper we present a kinetic analysis of the consecutive photoreaction scheme A⇄hνB→hνC assuming the reaction is carried out in a continuous flow stirred tank reactor (CSTR). The reactor is kept at constant temperature and fed with reactant A at a constant flow rate. A numerical analysis of the model's stationary states reveals a range of constraints for which the system possesses multiple steady states. The observed bistability depends strongly on the rate constant of the B→A reaction k2 . It is typically observed when k2 is much larger than the other rate constants. Our numerical calculations also reveal a marked dependency on parameters such as the molar absorptivities and the irradiation intensity I0 . Interestingly, multiple steady states are only observed for intermediate values of I0 . Analytical approximations are obtained for the stationary states in the limit where the end-product C does not absorb light. These approximations are used to clarify the mechanism responsible for the light-induced instability.

  9. Anaerobic co-digestion of chicken manure and corn stover in batch and continuously stirred tank reactor (CSTR).

    Science.gov (United States)

    Li, Yeqing; Zhang, Ruihong; He, Yanfeng; Zhang, Chenyu; Liu, Xiaoying; Chen, Chang; Liu, Guangqing

    2014-03-01

    Anaerobic co-digestion of chicken manure and corn stover in batch and CSTR were investigated. The batch co-digestion tests were performed at an initial volatile solid (VS) concentration of 3gVS/L, carbon-to-nitrogen (C/N) ratio of 20, and retention time of 30d. The methane yield was determined to be 281±12mL/gVSadded. Continuous reactor was carried out with feeding concentration of 12% total solids and C/N ratio of 20 at organic loading rates (OLRs) of 1-4gVS/L/d. Results showed that at OLR of 4gVS/L/d, stable and preferable methane yield of 223±7mL/gVSadded was found, which was equal to energy yield (EY) of 8.0±0.3MJ/kgVSadded. Post-digestion of digestate gave extra EY of 1.5-2.6MJ/kgVSadded. Pyrolysis of digestate provided additional EY of 6.1MJ/kgVSadded. Pyrolysis can be a promising technique to reduce biogas residues and to produce valuable gas products simultaneously.

  10. Solidification Structure and Macrosegregation of Billet Continuous Casting Process with Dual Electromagnetic Stirrings in Mold and Final Stage of Solidification: A Numerical Study

    Science.gov (United States)

    Jiang, D.; Zhu, M.

    2016-08-01

    Coupling macroscale heat transfer and fluid flow with microscale grain nucleation and crystal growth, a mixed columnar-equiaxed solidification model was established to study the SWRT82B steel solidification structure and macrosegregation in 160 mm × 160 mm billet continuous casting with dual electromagnetic stirrings in mold and final stage of solidification (M-EMS and F-EMS). In the model, the phases of liquid, columnar, and equiaxed were treated separately and the initial growing equiaxed phase, which could move freely with liquid, was regarded as slurry. To obtain the equiaxed grains nucleation and columnar front evolution, the unit tracking method and the columnar front tracking model were built. The model was validated by magnetic induction intensity of stirrer, billet surface temperature, and carbon segregation. The equiaxed phase evolution and the solute transport with effect of fluid flow and grains transport were described in this article. The results show that the equiaxed phase ratio will not increase obviously with higher current intensity of M-EMS, while the negative segregation near the strand surface becomes more serious. The negative segregation zone near the billet center and the center positive segregation come into being with the effect of equiaxed grains sedimentation and liquid thermosolutal flow. It is also found that the liquid solute transport in the F-EMS zone becomes the main factor with higher current intensity rather than the solidification rate, and therefore, the final billet center segregation decreases first and then turns to rise with the current intensity. The optimal current intensities of M-EMS and F-EMS proposed for SWRT82B billet continuous casting are 200 and 400 A, respectively.

  11. Recovery of resources for advanced life support space applications: effect of retention time on biodegradation of two crop residues in a fed-batch, continuous stirred tank reactor

    Science.gov (United States)

    Strayer, R. F.; Finger, B. W.; Alazraki, M. P.; Cook, K.; Garland, J. L.

    2002-01-01

    Bioreactor retention time is a key process variable that will influence costs that are relevant to long distance space travel or long duration space habitation. However. little is known about the effects of this parameter on the microbiological treatment options that are being proposed for Advanced Life Support (ALS) systems. Two bioreactor studies were designed to examine this variable. In the first one, six retention times ranging from 1.3 to 21.3 days--were run in duplicate, 81 working-volume continuous stirred tank reactors (CSTR) that were fed ALS wheat residues. Ash-free dry weight loss, carbon mineralization, soluble TOC reduction, changes in fiber content (cellulose, hemicellulose, and lignin), bacterial numbers, and mineral recoveries were monitored. At short retention times--1.33 days--biodegradation was poor (total: 16-20%, cellulose - 12%, hemicellulose - 28%) but soluble TOC was decreased by 75-80% and recovery of major crop inorganic nutrients was adequate, except for phosphorus. A high proportion of the total bacteria (ca. 83%) was actively respiring. At the longest retention time tested, 21.3 days, biodegradation was good (total: 55-60%, cellulose ca. 70%, hemicellulose - ca. 55%) and soluble TOC was decreased by 80%. Recovery of major nutrients, except phosphorus, remained adequate. A very low proportion of total bacteria was actively respiring (ca. 16%). The second bioreactor study used potato residue to determine if even shorter retention times could be used (range 0.25-2.0 days). Although overall biodegradation deteriorated, the degradation of soluble TOC continued to be ca. 75%. We conclude that if the goal of ALS bioprocessing is maximal degradation of crop residues, including cellulose, then retention times of 10 days or longer will be needed. If the goal is to provide inorganic nutrients with the smallest volume/weight bioreactor possible, then a retention time of 1 day (or less) is sufficient.

  12. Photocatalytic inactivation of Flavobacterium and E. coli in water by a continuous stirred tank reactor (CSTR) fed with suspended/immobilised TiO2 medium.

    Science.gov (United States)

    Cohen-Yaniv, Vered; Narkis, Nava; Armon, Robert

    2008-01-01

    A photocatalytic continuous stirred tank reactor (CSTR) was built at laboratory scale to inactivate two environmental bacteria strains (Flavobacterium and E. coli) in tap water. Several parameters were found to impact reactor efficiency. Bacterial initial concentration is an important factor in inactivation rate. After 30 minutes of irradiation at 10(8)-10(9) CFU mL(-1) starting concentration, a >5 log reduction was achieved while at 10(4)-10(6) CFU mL(-1) only a 2 log reduction was observed. Water hardness and pH have an important influence on the photocatalytic inactivation process. Soft water, with low Ca(+2) and Mg(+2) at low pH approximately 5.3 resulted in increased inactivation of Flavobacterium reaching >6 orders of magnitude reduction. E. coli and Flavobacterium at pH 5 were inactivated by 3 logs more as compared to pH 7 under similar conditions. pH below TiO2 isoelectric point (approximately 5.6) supports better contact between bacteria and anatase particles resulting in superior inactivation. TiO2 powder suspension was compared with immobilised powder in sol-gel coated glass beads in order to exclude the need for particles separation from the treated water. TiO2 suspension was more effective by 3 orders of magnitude when compared to coated glass beads. An interesting observation was found between the two bacterial strains based on their hydrophobicity/hydrophilicity balance. The more hydrophobic Flavobacterium compared to E. coli was inactivated photocatalytically by >3 logs more then E. coli in the first 30 minutes of irradiation interval. The results indicate the importance of the parameters involved in the contact between TiO2 particles and microorganisms that govern the successful inactivation rate in CSTR.

  13. Coupling of acrylic dyeing wastewater treatment by heterogeneous Fenton oxidation in a continuous stirred tank reactor with biological degradation in a sequential batch reactor.

    Science.gov (United States)

    Esteves, Bruno M; Rodrigues, Carmen S D; Boaventura, Rui A R; Maldonado-Hódar, F J; Madeira, Luís M

    2016-01-15

    This work deals with the treatment of a recalcitrant effluent, from the dyeing stage of acrylic fibres, by combination of the heterogeneous Fenton's process in a continuous stirred tank reactor (CSTR) with biological degradation in a sequential batch reactor (SBR). Three different catalysts (a commercial Fe/ZSM-5 zeolite and two distinct Fe-containing activated carbons - ACs - prepared by wet impregnation of iron acetate and iron nitrate) were employed on the Fenton's process, and afterwards a parametric study was carried out to determine the effect of the main operating conditions, namely the hydrogen peroxide feed concentration, temperature and contact time. Under the best operating conditions found, using the activated carbon impregnated with iron nitrate, 62.7% of discolouration and 39.9% of total organic carbon (TOC) reduction were achieved, at steady-state. Furthermore, a considerable increase in the effluent's biodegradability was attained (BOD5:COD ratio increased from <0.001 to 0.27 and SOUR - specific oxygen uptake rate - from <0.2 to 11.1 mg O2/(gVSS·h)), alongside a major decrease in its toxicity (from 92.1 to 94.0% of Vibrio fischeri inhibition down to 6.9-9.9%). This allowed the application of the subsequent biological degradation stage. The combination of the two processes provided a treated effluent that clearly complies with the legislated discharge limits. It was also found that the iron leaching from the three catalysts tested was very small in all runs, a crucial factor for the stability and long-term use of such materials.

  14. 三维运动连续进料式混合搅拌机%Operating Principles and Properties of a 3-dimensional Motion Continuous Feeding Stirring Mixer

    Institute of Scientific and Technical Information of China (English)

    戴长虹; 李绍纯

    2011-01-01

    The paper introduced a new type of 3-dimensional motion continuous feeding stirring mixer, which includes fiamework, tempering tank, mixer shaft, agitating machine, rotating machine, rotating shaft, collector ring, and brush.The operating principles and assembling drawing of this stirring mixer were fully discussed. The main characteristic of this mixer includes two aspects, on the one hand is mixing the materials in rotary tempering tank under the rotating shaft functions, thus greatly increase the mix efficiency, on the other hand is mixing the materials while continuous charge-in through the hollow rotating shaft. Therefore, this type of mixer with continuous tilling function has advantages of high efficiency, high precision, low energy consumption and practical for many fields of industry. [ Ch, 1 fig. 14 ref. ]%文章设计了一种新型三维运动连续进料式混合搅拌机.其结构包括机架、混合桶、搅拌轴、搅拌电机、旋转电机、旋转轴、集电环和电刷.该混合搅拌机一方面将混合桶的旋转和混合桶内搅拌轴的旋转结合在一起,大幅度提高了混料的效率,另一方面将旋转轴作为进、出料口,可以进行连续性装填,提高了效率,降低了能耗.

  15. Aperiodicity resulting from two-cycle coupling in the Belousov-Zhabotinskii reaction. III. Analysis of a model of the effect of spatial inhomogeneities at the input ports of a continuous-flow, stirred tank reactor

    Science.gov (United States)

    Györgyi, László; Field, Richard J.

    1989-11-01

    Deterministic chaos is a well-established phenomenon in continuous-flow, stirred tank reactor (CSTR) experiments with the oscillatory Belousov-Zhabotinskii (BZ) reaction. However, it has not yet been possible to reproduce the experimentally observed, robust chaos in simulations using realistic models of the homogeneous chemical kinetics of the BZ reaction. That it may be necessary to consider spatial inhomogeneities in modeling the BZ chaos is suggested by the existence of strong stirring effects on the aperiodic behavior and by the difficulty of reproducing chaos under the same conditions in reactors of different physical configuration. Such inhomogeneity might result from a lack of perfect mixing in the CSTR, especially near the inlets, or from diffusion of species at low flow rates from the CSTR reaction mixture into the tips of the inlets. The presence of spatial inhomogeneities allows coupling between essentially independent oscillators, a well-known source of chaos. Such a model using a realistic representation of the BZ kinetics leads to an eight-variable set of ordinary differential equations. Numerical analysis of these equations by continuation methods and by numerical integration shows the existence of broad regions of chaos and various hysteresis effects involving limit cycles, a steady state and/or a strange attractor. Tristability was found in calculations in a narrow flow rate range. The computed behavior appears for parameter values closely related to the values used experimentally to obtain similar phenomena, and the visual similarity of the computed and experimental strange attractors is striking. The experimental routes to chaos, period doubling, intermittency, and secondary Hopf bifurcations are all reproduced in the simulations. The computed and experimental structures of periodic windows observed within chaotic regions also are very similar.

  16. Effects of nitrobenzene concentration and hydraulic retention time on the treatment of nitrobenzene in sequential anaerobic baffled reactor (ABR)/continuously stirred tank reactor (CSTR) system.

    Science.gov (United States)

    Kuscu, Ozlem Selcuk; Sponza, Delia Teresa

    2009-04-01

    The effects of increasing nitrobenzene (NB) concentrations and hydraulic retention times (HRT) on the treatment of NB were investigated in a sequential anaerobic baffled reactor (ABR)/aerobic completely stirred tank reactor (CSTR) system. In the first step of the study, the maximum COD removal efficiencies were found as 88% and 92% at NB concentrations varying between 30 mg L(-1) and 210 mg L(-1) in ABR. The minimum COD removal efficiency was 79% at a NB concentration of 700 mg L(-1). The removal efficiency of NB was nearly 100% for all NB concentrations in the ABR reactor. The methane gas production and the methane gas percentage remained stable (1500 mL day(-1) and 48-50%, respectively) as the NB concentration was increased from 30 to 210 mg L(-1). In the second step of the study it was found that as the HRT decreased from 10.38 days to 2.5 days the COD removal efficiencies decreased slightly from 94% to 92% in the ABR. For maximum COD and NB removal efficiencies the optimum HRT was found as 2.5 days in the ABR. The total COD removal efficiency was 95% in sequential anaerobic (ABR)/aerobic (CSTR) reactor system at a minimum HRT of 1 day. When the HRT was decreased from 10.38 days to 1 day, the methane percentage decreased from 42% to 29% in an ABR reactor treating 100 mg L(-1) NB. Nitrobenzene was reduced to aniline under anaerobic conditions while aniline was mineralized to catechol with meta cleavage under aerobic conditions.

  17. Friction stir welding tool

    Science.gov (United States)

    Tolle; Charles R. , Clark; Denis E. , Barnes; Timothy A.

    2008-04-15

    A friction stir welding tool is described and which includes a shank portion; a shoulder portion which is releasably engageable with the shank portion; and a pin which is releasably engageable with the shoulder portion.

  18. Robust L2-L∞ Control for Continuous Stirred Tank Reactor Based on T-S Model%基于T-S模型的连续搅拌反应釜鲁棒L2-L∞控制

    Institute of Scientific and Technical Information of China (English)

    李艳辉; 冯岩

    2014-01-01

    To realize precise control for CSTR( Continuous Stirring Tank Reactor) systems in actual reactions, a robust L2-L∞ state feedback control problem is studied by using a T-S fuzzy model to approximate the nonlinear object according to reaction characteristics of the CSTR. All reactor temperatures which are easier to be measured can be treated as premise variables in the model, where fewer number of fuzzy rules are employed. The design method of partial controllers is given by applying the PDC ( Parallel Distributed Compensation ) algorithm. A global controller is designed by adopting the LMI ( Linear Matrix Inequality ) technique, and the design of controllers is cast into a convex optimization problem. Simulations are provided to demonstrate the effectiveness of the proposed design scheme, which can be applied to other chemical industrial reactions.%为实现对连续搅拌反应釜( CSTR:Continuous Stirring Tank Reactor)系统在实际反应中的精确控制,根据CSTR反应特点,采用T-S模糊模型逼近非线性对象,研究鲁棒L2-L∞状态反馈控制问题。模型中将更易测量的反应器温度作为前件变量,模糊规则少。应用平行分配补偿算法( PDC:Parallel Distributed Compensation),给出局部控制器的设计方法,并利用线性矩阵不等式( LMI:Linear Matrix Inequality)技术设计全局控制器,在此基础上把控制器的设计转化为一个凸优化的求解问题。最后仿真验证了该方法的有效性,从而可扩展到其他化学工业反应中。

  19. Ce-Zr-La/Al2O3 prepared in a continuous stirred-tank reactor: a highly thermostable support for an efficient Rh-based three-way catalyst.

    Science.gov (United States)

    Wang, Su-Ning; Lan, Li; Hua, Wei-Bo; Shi, Zhong-Hua; Chen, Yao-Qiang; Gong, Mao-Chu; Zhong, Lin

    2015-12-21

    Two Ce-Zr-La/Al2O3 composite oxides, CZLA-C and CZLA-B, were synthesized using a co-precipitation method in a continuous stirred-tank reactor (CSTR) and a batch reactor (BR), respectively. Two Rh-based three-way catalysts (TWCs), Rh/CZLA-C and Rh/CZLA-B were obtained by a wet-impregnation method using the two composites as the supports. The physicochemical properties of the samples before and after thermal treatment at 1000 °C were characterized by N2 adsorption-desorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), H2-temperature programmed reduction (H2-TPR) and CO chemisorption. The results indicated that CZLA-C shows higher thermal stability than CZLA-B due to a sparsely-agglomerated morphology. Compared with Rh/CZLA-B, Rh/CZLA-C displayed better reducibility and higher thermal stability and exhibited significantly higher activity in the catalytic removal of the simulated gasoline vehicle exhaust emission (NO, CO and C3H8). Our work can provide a facile and economical synthesis route to advanced support materials and catalysts for exhaust emission control.

  20. Hinfinity control for continuous stirred tank reactor based on Takagi-Sugeno fuzzy bilinear models%基于Takagi-Sugeno模糊双线性模型的连续搅拌反应釜H∞控制

    Institute of Scientific and Technical Information of China (English)

    陈珺; 刘飞

    2012-01-01

    This paper is concerned with the H-infinity control for a class of continuous stirred tank reactor (CSTR) systems, in which the nonlinear dynamics are described by TakagiSugeno fuzzy bilinear models. By introducing two free matrix variables, we derive a new sufficient condition, in terms of linear matrix inequalities, of the global stability with a prescribed Hinfinity performance level for the closedloop fuzzy bilinear systems. The controller design method is also given. Simulation results of a CSTR system illustrate the effectiveness of the design method.%本文研究了一类连续搅拌反应釜(CSTR)系统的H∞控制问题.系统中的非线性动态特性可采)用Takagi-Sugeno(T-S)模糊双线性模型进行描述.通过引入两个自由矩阵,给出一个新的保证闭环模糊双线性系统在H∞性能指标下全局渐近稳定的充分条件和控制器设计方法,并且该条件最终可归结为求解一组线性矩阵不等式的可行性问题.CSTR系统的仿真结果表明设计方法的有效性.

  1. Inactivating effects of lignin-derived compounds released during lignocellulosic biomass pretreatment on the endo-glucanase catalyzed hydrolysis of carboxymethylcellulose: A study in continuous stirred ultrafiltration-membrane reactor.

    Science.gov (United States)

    Cantarella, Maria; Mucciante, Claudia; Cantarella, Laura

    2014-03-01

    This study focusses on the reversible/irreversible damage that selected phenolic compounds, released during steam-explosion pretreatment, mandatory for cellulose accessibility, causes on both stability and activity of a commercial cellulase (half-life=173h) during carboxymethyl-cellulose hydrolysis. Long-term experiments performed in continuous stirred UF-membrane bioreactors, operating at steady-state regime, in controlled operational conditions, allowed evaluating the inactivation-constant in the phenol presence (kd1) and after its removal (kd2) from the reactor feed. p-Hydroxybenzoic acid (1 and 2g L(-1)) are the extreme limits in the inactivating effect with enzyme half-lives 99.02 and 14.15h, respectively. The inactivation reversibility was assessed for vanillic acid, p-hydroxybenzoic acid, syringaldehyde, p-coumaric acid, being kd1>kd2. p-Hydroxybenzaldehyde and protocatechuic acid irreversibly affected cellulase stability increasing its inactivation with kd2>kd1. p-Hydroxybenzaldehyde, 1g L(-1), syringaldehyde, and vanillin, at 2gL(-1), had similar kd1÷kd2.

  2. Characterization of flow conditions in 2 L and 20 L wave bioreactors using computational fluid dynamics.

    Science.gov (United States)

    Oncül, Alper A; Kalmbach, Andreas; Genzel, Yvonne; Reichl, Udo; Thévenin, Dominique

    2010-01-01

    Characterization of flow conditions is of great importance to control cell growth and cell damage in animal cell culture because cell viability is influenced by the flow properties in bioreactors. Alternative reactor types like Wave Bioreactors have been proposed in recent years, leading to markedly different results in cell growth and product formation. An advantage of Wave Bioreactors is the disposability of the Polyethylenterephthalet-bags after one single use (fast setup of new production facilities). Another expected advantage is a lower shear stress compared to classical stirred-tank reactors, due to the gentle liquid motion in the rocking cellbag. This property would considerably reduce possible cell damage. The purpose of the present study is to investigate in a quantitative manner the key flow properties in Wave Bioreactors, both numerically and experimentally. To describe accurately flow conditions and shear stress in Wave Bioreactors using numerical simulations, it is necessary to compute the unsteady flow applying Computational Fluid Dynamics (CFD). Corresponding computations for two reactor scales (2 L and 20 L cellbags) are presented using the CFD code ANSYS-FLUENT. To describe correctly the free liquid surface, the present simulations employ the Volume of Fluid (VOF) method. Additionally, experimental measurements have been carried out to determine liquid level, flow velocity and liquid shear stress, which are used as a validation of the present CFD simulations. It is shown that the obtained flows stay in the laminar regime. Furthermore, the obtained shear stress levels are well below known threshold values leading to damage of animal cells. PMID:19918766

  3. Topological stirring of two-dimensional atomic Bose-Einstein condensates

    International Nuclear Information System (INIS)

    We stir vortices into a trapped quasi two-dimensional atomic Bose-Einstein condensate by moving three laser stirrers. We apply stirring protocols introduced by Boyland et al. (2000), that efficiently build in topological chaos in classical fluids and are classified as Pseudo-Anosov stirring protocols. These are compared to their inefficient mixing counterparts, finite-order stirring protocols. We investigate if inefficient stirring protocols result in a more clustered distribution of vortices. The efficiency with which vortices are 'mixed' or distributed in a condensate is important for investigating dynamics of continuously forced quantum turbulence and the existence of the inverse cascade in turbulent two-dimensional superfluids

  4. Neural network predictive control of continuous stirred-tank reactor based on Hammerstein-Wiener model%基于Hammerstein-Wiener模型的连续搅拌反应釜神经网络预测控制

    Institute of Scientific and Technical Information of China (English)

    满红; 邵诚

    2011-01-01

    针对化工过程中广泛使用的连续搅拌反应釜(CSTR),提出一种基于神经网络的模型预测控制策略,采用分段最小二乘支持向量机辨识Hammerstein-Wiener模型系数的方法,在此基础上建立线性自回归模式(ARX)结构和高斯径向基神经网络串联的非线性预测控制器.利用BP神经网络训练预测控制输入序列和拟牛顿算法求解非线性预测控制律,从而实现一种基于支持向量机Hammerstein-Wiener辨识模型的非线性神经网络预测控制算法.对CSTR的仿真结果表明,该方法能够更有效地跟踪控制反应物浓度.%A model predictive control strategy based on neural network is presented for a continuous stirred tank reactor (CSTR). A segmentation method was adopted to identify Hammerstein-Wiener model coefficient by least squares support vector machines and then to construct a nonlinear predictive controller which was by a linear optimal component and radial basis function neural networks in series. A nonlinear predictive control algorithm based on least support vector machines Hammerstein-Wiener model was realized by using BP neural network to train predictive input sequences and to solve nonlinear predictive control rules by Quasi-Newton method. The simulation results of CSTR illustrate that this approach is effective tracking and controlling product concentration.

  5. Importance of reduced sulfur for the equilibrium chemistry and kinetics of Fe(II), Co(II) and Ni(II) supplemented to semi-continuous stirred tank biogas reactors fed with stillage

    International Nuclear Information System (INIS)

    Highlights: • Thermodynamics and kinetics of Fe, Co and Ni added to biogas reactors were studied. • Formation of Fe-sulfide and Fe-thiol aqueous complexes controlled the Fe solubility. • Cobalt solubility was controlled by processes independent of Co-sulfide interaction. • Iron added to the biogas reactors effected the Ni speciation and solubility. - Abstract: The objective of the present study was to assess major chemical reactions and chemical forms contributing to solubility and speciation of Fe(II), Co(II), and Ni(II) during anaerobic digestion of sulfur (S)-rich stillage in semi-continuous stirred tank biogas reactors (SCSTR). These metals are essential supplements for efficient and stable performance of stillage-fed SCSTR. In particular, the influence of reduced inorganic and organic S species on kinetics and thermodynamics of the metals and their partitioning between aqueous and solid phases were investigated. Solid phase S speciation was determined by use of S K-edge X-ray absorption near-edge spectroscopy. Results demonstrated that the solubility and speciation of supplemented Fe were controlled by precipitation of FeS(s) and formation of the aqueous complexes of Fe-sulfide and Fe-thiol. The relatively high solubility of Co (∼20% of total Co content) was attributed to the formation of compounds other than Co-sulfide and Co-thiol, presumably of microbial origin. Nickel had lower solubility than Co and its speciation was regulated by interactions with FeS(s) (e.g. co-precipitation, adsorption, and ion substitution) in addition to precipitation/dissolution of discrete NiS(s) phase and formation of aqueous Ni-sulfide complexes

  6. Friction Stir Weld Tools

    Science.gov (United States)

    Carter, Robert W. (Inventor); Payton, Lewis N. (Inventor)

    2007-01-01

    A friction stir weld tool sleeve is supported by an underlying support pin. The pin material is preferably selected for toughness and fracture characteristics. The pin sleeve preferably has a geometry which employs the use of an interrupted thread, a plurality of flutes and/or eccentric path to provide greater flow through. Paddles have been found to assist in imparting friction and directing plastic metal during the welding process.

  7. Friction Stir Welding

    Science.gov (United States)

    Nunes, Arthur C., Jr.

    2008-01-01

    Friction stir welding (FSW) is a solid state welding process invented in 1991 at The Welding Institute in the United Kingdom. A weld is made in the FSW process by translating a rotating pin along a weld seam so as to stir the sides of the seam together. FSW avoids deleterious effects inherent in melting and promises to be an important welding process for any industries where welds of optimal quality are demanded. This article provides an introduction to the FSW process. The chief concern is the physical effect of the tool on the weld metal: how weld seam bonding takes place, what kind of weld structure is generated, potential problems, possible defects for example, and implications for process parameters and tool design. Weld properties are determined by structure, and the structure of friction stir welds is determined by the weld metal flow field in the vicinity of the weld tool. Metal flow in the vicinity of the weld tool is explained through a simple kinematic flow model that decomposes the flow field into three basic component flows: a uniform translation, a rotating solid cylinder, and a ring vortex encircling the tool. The flow components, superposed to construct the flow model, can be related to particular aspects of weld process parameters and tool design; they provide a bridge to an understanding of a complex-at-first-glance weld structure. Torques and forces are also discussed. Some simple mathematical models of structural aspects, torques, and forces are included.

  8. Continuous stirred tank reactor mechanical modelling and opening virtual simulation system development%连续搅拌反应釜机理建模与开放式虚拟仿真系统开发

    Institute of Scientific and Technical Information of China (English)

    邓晓刚; 于佐军

    2016-01-01

    This paper proposes an opening virtual simulation system design method based on the chemical reactor mechanism model.One common chemical reactor referred to as continuous stirred tank reactor (CSTR) is used as the simulation objective.Firstly,its mathematical models are built using the mechanism analysis technique.Then the process flow diagram is constructed by LabVIEW software and the simulation programs are established using the four-order Runge-Kutta method.With the help of shared variable engine (SVE),the simulation data are deployed to OPC server,which leads to good system open performances.Matlab is used to illustrate the calling procedure of sharing data.This system can simulate the CSTR device characteristics well. Also the openness of simulation helps students to design their own control strategy and provides a platform for the innovative experiment.%以一类常见的化学反应器———连续搅拌反应釜(CSTR)为虚拟仿真对象,提出一种基于化学反应器装置机理模型的开放式虚拟仿真系统开发方法。首先,使用机理分析法建立数学模型;然后,在 LabVIEW 软件中构建工艺流程界面,并基于四阶龙格-库塔法编制虚拟仿真程序;进一步,利用共享变量引擎将虚拟装置数据发布到 OPC Server 中,使虚拟系统具有良好的开放性。以 Matlab 软件为例,说明了共享数据的调用过程。该虚拟仿真系统不但能够较好地模拟 CSTR 的工艺特性,而且其数据的开放性有助于学生自行设计控制方案、自主开展创新性实验研究。

  9. Phase separation dynamics under stirring

    OpenAIRE

    Lacasta Palacio, Ana María; Sancho, Jose Maria; Sagués Mestre, Francesc

    1995-01-01

    Phase separation dynamics in the presence of externally imposed stirring is stuidied. The stirring is assumed independent of the concentration and it is generated with a well-defined energy spectrum. The domain growth process is either favored or frozen depending on the intensity and correlation length of this advective flow. This behavior is explained by analytical arguments.

  10. Stirring by swimming bodies

    International Nuclear Information System (INIS)

    We consider the stirring of an inviscid fluid caused by the locomotion of bodies through it. The swimmers are approximated by non-interacting cylinders or spheres moving steadily along straight lines. We find the displacement of fluid particles caused by the nearby passage of a swimmer as a function of an impact parameter. We use this to compute the effective diffusion coefficient from the random walk of a fluid particle under the influence of a distribution of swimming bodies. We compare with the results of simulations. For typical sizes, densities and swimming velocities of schools of krill, the effective diffusivity in this model is five times the thermal diffusivity. However, we estimate that viscosity increases this value by two orders of magnitude.

  11. Research on Change Process of Nitrosation Granular Sludge in Continuous Stirred-Tank Reactor%CSTR 中亚硝化颗粒污泥的变化过程研究

    Institute of Scientific and Technical Information of China (English)

    阴方芳; 刘文如; 王建芳; 吴鹏; 沈耀良

    2014-01-01

    在连续全混反应器(CSTR)中接种 SBR 培养成熟的亚硝化颗粒污泥,考察反应器构型对亚硝化颗粒污泥生长和运行的影响特性.结果表明,反应器构型和进水模式变化初期部分颗粒污泥解体,污泥平均沉速下降;但随着反应器的进一步运行, CSTR 中实现了亚硝化絮体污泥的快速颗粒化过程;整个研究过程中,虽颗粒粒径分布存较大变化,如粒径>2.5 mm 颗粒的减少和粒径《0.3 mm 颗粒的增加,但颗粒态污泥始终是 CSTR 中占优势的污泥形态.另外,研究表明反应器构型和进水模式的改变对出水中亚硝酸盐累积率(保持在85%左右)无显著影响,并且新生的小粒径颗粒污泥比大粒径颗粒具有更高的比反应活性,此 CSTR 中污泥的平均活性亦高于接种污泥平均活性.%In order to investigate the effect of different types of reactors on the nitrosation granular sludge, a continuous stirred-tank reactor (CSTR) was studied, using mature nitrosation granular sludge cultivated in sequencing batch reactor (SBR) as seed sludge. Results indicated that the change of reactor type and influent mode could induce part of granules to lose stability with gradual decrease in sludge settling ability during the initial period of operation. However, the flocs in CSTR achieved fast granulation in the following reactor operation. In spite of the changes of particle size distribution, e. g. the decreasing number of granules with diameter larger than 2. 5 mm and the increasing number of granules with diameter smaller than 0. 3 mm, granular sludge held the absolute predominance of sludge morphology in CSTR during the entire experimental period. Moreover, results showed that the change of reactor type and influent mode didn't affect the nitrite accumulation rate which was still kept at about 85% in effluent. Additionally, the average activity of the sludge in CSTR was stronger than that of the seed sludge, because

  12. 微生物燃料电池耦合连续搅拌反应系统(CSTR)低温下处理“糖蜜-电镀”废水%Microbial fuel cell with continuous stirred reactor system (CSTR) for continuous flow Processing of “Molasses-Electroplating”wastewater at low temperatures

    Institute of Scientific and Technical Information of China (English)

    谢静怡; 李永峰; 孙彩玉; 秦必达

    2015-01-01

    为提高传统微生物燃料电池( MFC)在低温条件下的效率,实现实验装置放大化.本实验将连续搅拌反应系统( CSTR)与双极室微生物燃料电池系统相结合,连续流处理糖蜜废水,并间接回收金属单质,处理模拟电镀废水,考察系统的产电性能和废水处理效果.结果表明,当系统稳定运行后,最高电压及功率密度分别可达到340 mV和58.65 mW·m-2.20 d后,系统COD去除率明显增加,最高COD去除率可达到81%.实验运行10 d后,银离子开始析出,最高去除率可达到90%左右.%In order to improve the efficiency of traditional microbial fuel cells ( MFC ) at low temperatures, and scale up the experimental device amplification, this experiment combined a continuous stirred reactor with a two chamber microbial fuel cell to continuously process molasses wastewater and simulated electroplating wastewater, indirectly recovered metals, and investigated electricity production and wastewater treatment effect. The results from the experiment showed that the highest voltage output of 340 mV and the maximum power density of 58. 65 mW·m-2 were obtained under a stable operating condition. In addition,COD removal rate reached its highest value (81%)after 20 d, and the maximum removal rate(90%) for Ag+ was recorded after 10 d.

  13. Stirring and mixing effects on oscillations and inhomogeneities in the minimal bromate oscillator

    Science.gov (United States)

    Dutt, A. K.; Menzinger, M.

    1999-04-01

    Stirring and mixing effects on the oscillations and inhomogeneities in the bromate-bromide-cerous system (minimal bromate oscillator) have been investigated in a continuously fed stirred tank reactor (CSTR). A movable microelectrode is used to monitor the inhomogeneities inside the CSTR in an oscillating phase. The results are explained in terms of the theory of imperfect mixing.

  14. Phosphorus removal in aerated stirred tank reactor

    Energy Technology Data Exchange (ETDEWEB)

    Ghigliazza, R.; Lodi, A.; Rovatti, M. [Inst. of Chemical and Process Engineering ``G.B. Bonino``, Univ. of Genoa (Italy)

    1999-03-01

    The possibility to obtain biological phosphorus removal in strictly aerobic conditions has been investigated. Experiments, carried out in a continuous stirred tank reactor (CSTR), show the feasibility to obtain phosphorus removal without the anaerobic phase. Reactor performance in terms of phosphorus abatement kept always higher then 65% depending on adopted sludge retention time (SRT). In fact increasing SRT from 5 days to 8 days phosphorus removal and reactor performance increase but overcoming this SRT value a decreasing in reactor efficiency was recorded. (orig.) With 6 figs., 3 tabs., 18 refs.

  15. Opel 2.0-l biturbo diesel engine with two-stage intercooling; 2,0-L-Biturbo-Dieselmotor von Opel mit Zweistufen-Ladeluftkuehlung

    Energy Technology Data Exchange (ETDEWEB)

    Wartha, Jens; Westin, Fredrik; De Marco, Mirco [GM Powertrain Europe, Turin (Italy); Leu, Alexander [Adam Opel AG, Ruesselsheim (Germany)

    2012-07-15

    Opel has developed a 2.0-l biturbo diesel engine that features two-stage charging, piezo injection technology and a closed-loop combustion system for low emissions and a good fuel economy. All these measures in combination with a first time applied two-stage intercooling lead to high power and torque density and allow a further improvement in transient response. (orig.)

  16. Stirring-induced bifurcation driven by the chaotic regime in the Belousov—Zhabotinsky reaction in a CSTR

    Science.gov (United States)

    Strizhak, Peter E.

    1995-09-01

    The stirring-induced bifurcation at low stirring rate S 0 = 23 rpm of the reaction volume has been observed for the chaotic regime in the Belousov—Zhabotinsky oscillating chemical reaction (malonic acidbromatecerium(III)sulfuric acid) in a continuously stirred tank reactor in premixing mode. This bifurcation is characterized by a stepwise growth of the macroscopic spatial concentration gradients that is shown by the use of the time dependencies of the potential difference between two platinum electrodes.

  17. Deformation During Friction Stir Welding

    Science.gov (United States)

    White, Henry J.

    2002-01-01

    Friction Stir Welding (FSW) is a solid state welding process that exhibits characteristics similar to traditional metal cutting processes. The plastic deformation that occurs during friction stir welding is due to the superposition of three flow fields: a primary rotation of a radially symmetric solid plug of metal surrounding the pin tool, a secondary uniform translation, and a tertiary ring vortex flow (smoke rings) surrounding the tool. If the metal sticks to the tool, the plug surface extends down into the metal from the outer edge of the tool shoulder, decreases in diameter like a funnel, and closes up beneath the pin. Since its invention, ten years have gone by and still very little is known about the physics of the friction stir welding process. In this experiment, an H13 steel weld tool (shoulder diameter, 0.797 in; pin diameter, 0.312 in; and pin length, 0.2506 in) was used to weld three 0.255 in thick plates. The deformation behavior during friction stir welding was investigated by metallographically preparing a plan view sections of the weldment and taking Vickers hardness test in the key-hole region.

  18. Modelling of baffled stirred tanks

    Energy Technology Data Exchange (ETDEWEB)

    Ahlstedt, H.; Lahtinen, M. [Tampere Univ. of Technology (Finland). Energy and Process Engineering

    1996-12-31

    The three-dimensional flow field of a baffled stirred tank has been calculated using four different turbulence models. The tank is driven by a Rushton-type impeller. The boundary condition for the impeller region has been given as a source term or by calculating the impeller using the sliding mesh technique. Calculated values have been compared with measured data. (author)

  19. Stirring and biomass starter influences the anaerobic digestion of different substrates for biogas production

    Energy Technology Data Exchange (ETDEWEB)

    Rojas, Christian; Fang, Sheng; Uhlenhut, Frank; Borchert, Axel; Stein, Ingo; Schlaak, Michael [Institut fuer Umwelttechnik EUTEC, Fachbereich Technik, Fachhochschule Emden/Leer, Emden (Germany)

    2010-08-15

    Here, we present the results of lab-scale experiments conducted in a batch mode to determine the biogas yield of lipid-rich waste and corn silage under the effect of stirring. Further semi-continuous experiments were carried out for the lipid-rich waste with/without stirring. Additionally, it was analyzed how the starter used for the batch experiment influences the digestion process. The results showed a significant stirring effect on the anaerobic digestion only when seed sludge from a biogas plant was used as a starter. In this case, the experiments without stirring yielded only about 50% of the expected biogas for the investigated substrates. The addition of manure slurry to the batch reactor as part of the starter improved the biogas production. The more diluted media in the reactor allowed a better contact between the bacteria and the substrates making stirring not necessary. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  20. 用数值模拟方法分析混合和导流筒对搅拌槽中沉淀硫酸钡的影响%Computational Fluid Dynamics Approach to the Effect of Mixing and Draft Tube on the Precipitation of Barium Sulfate in a Continuous Stirred Tank

    Institute of Scientific and Technical Information of China (English)

    王正; 毛在砂; 杨超; 沈湘黔

    2006-01-01

    The effect of mixing on the precipitation of barium sulfate in a continuous stirred tank is simulated numerically with different feeding location, feed concentration, impeller speed and residence time through solving the standard momentum and mass transport equations in combination with the moment equations for crystal population balance. The numerical method was validated with the literature data. The simulation results including the distribution of the local supersaturation ratio distribution in the precipitator, mean crystal size and coefficient of variation under different operating conditions compared well with experimental data in the literature. The effect of the presence of a draft tube on precipitation were also investigated, and it is suggested that the installation of a draft tube increased the mean crystal size, in general agreement with experimental work in the literature.

  1. New Tool Creates a Big Stir

    Science.gov (United States)

    2001-01-01

    A new self-adjusting, retractable pin tool for friction stir welding is now used in the manufacturing of components for NASA Space Shuttles. Friction stir welding is a process that makes straight-line welds without bringing the parent material to a liquid state. This is accomplished through high-speed rotation, which generates frictional heat between the welding tool and the piece being welded. This heat causes the material to soften to the point of plasticity without allowing it to melt. The plasticized material is then transferred from the front edge of the welding tool to the trail edge, where it joins the pieces being welded. However, a major flaw of this method is its reliance on a single-piece pin tool. The weld is left unfinished and a hole remains where the pin was inserted. The hole must be covered with a rivet in order to preserve the integrity of the weld. The NASA-developed pin tool, however, eliminates the need for this finishing step, as its retraction allows continuous rewelding at lesser depths, until the hole is completely closed. With this NASA technology, welding of higher strength alloys, as well as non-planer and variable thickness structures can be achieved.

  2. Friction Stir Process Mapping Methodology

    Science.gov (United States)

    Kooney, Alex; Bjorkman, Gerry; Russell, Carolyn; Smelser, Jerry (Technical Monitor)

    2002-01-01

    In FSW (friction stir welding), the weld process performance for a given weld joint configuration and tool setup is summarized on a 2-D plot of RPM vs. IPM. A process envelope is drawn within the map to identify the range of acceptable welds. The sweet spot is selected as the nominal weld schedule. The nominal weld schedule is characterized in the expected manufacturing environment. The nominal weld schedule in conjunction with process control ensures a consistent and predictable weld performance.

  3. Pulsed ultrasonic stir welding system

    Science.gov (United States)

    Ding, R. Jeffrey (Inventor)

    2013-01-01

    An ultrasonic stir welding system includes a welding head assembly having a plate and a rod passing through the plate. The rod is rotatable about a longitudinal axis thereof. During a welding operation, ultrasonic pulses are applied to the rod as it rotates about its longitudinal axis. The ultrasonic pulses are applied in such a way that they propagate parallel to the longitudinal axis of the rod.

  4. Friction Stir Welding: A Review

    OpenAIRE

    Jain, Sumit; Gupta, Rajat; Singh, Arvinder; Sharma, Neeraj

    2013-01-01

    Friction stir welding (FSW) is a solid state joining process in which a rotating tool is used to join the two metal parts. The rotating tool is inserted in between two metal parts and the frictional energy is used to join the metal. In this research paper a review has been presented on FSW. The previous literature has been discussed along with the future aspects included in the field of FSW.

  5. Modelling of friction stir welding

    OpenAIRE

    Colegrove, Paul Andrew

    2004-01-01

    This thesis investigates the modelling of friction stir welding (FSW). FSW is a relatively new welding process where a rotating non-consumable tool is used to join two materials through high temperature deformation. The aim of the thesis is the development of a numerical model to improve process understanding and to assist in the design of new tools. The early part of the thesis describes the process, defines the modelling problem and describes why a computational fluid dynamics package (FLUE...

  6. Ozone absorption in a mechanically stirred reactor

    Directory of Open Access Journals (Sweden)

    LJILJANA TAKIC

    2007-08-01

    Full Text Available Ozone absorption in water was investigated in a mechanically stirred reactor, using both the semi-batch and continuous mode of operation. A model for the precise determination of the volumetric mass transfer coefficient in open tanks without the necessity of the measurement the ozone concentration in the outlet gas was developed. It was found that slow ozone reactions in the liquid phase, including the decomposition of ozone, can be regarded as one pseudo-first order reaction. Under the examined operating conditions, the liquid phase was completely mixed, while mixing in a gas phase can be described as plug flow. The volumetric mass transfer coefficient was found to vary with the square of the impeller speed.

  7. Flexible Friction Stir Joining Technology

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Zhili [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Lim, Yong Chae [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Mahoney, Murray [MegaStir Technologies LLC, Orem, UT (United States); Sanderson, Samuel [MegaStir Technologies LLC, Orem, UT (United States); Larsen, Steve [MegaStir Technologies LLC, Orem, UT (United States); Steel, Russel [MegaStir Technologies LLC, Orem, UT (United States); Fleck, Dale [MegaStir Technologies LLC, Orem, UT (United States); Fairchild, Doug P [ExxonMobil, Upstream Research Company (URC), Houston, TX (United States); Wasson, Andrew J [ExxonMobil, Upstream Research Company (URC), Houston, TX (United States); Babb, Jon [MegaStir Technologies LLC, Orem, UT (United States); Higgins, Paul [MegaStir Technologies LLC, Orem, UT (United States)

    2015-07-23

    Reported herein is the final report on a U.S. Department of Energy (DOE) Advanced Manufacturing Office (AMO) project with industry cost-share that was jointly carried out by Oak Ridge National Laboratory (ORNL), ExxonMobil Upstream Research Company (ExxonMobil), and MegaStir Technologies (MegaStir). The project was aimed to advance the state of the art of friction stir welding (FSW) technology, a highly energy-efficient solid-state joining process, for field deployable, on-site fabrications of large, complex and thick-sectioned structures of high-performance and high-temperature materials. The technology innovations developed herein attempted to address two fundamental shortcomings of FSW: 1) the inability for on-site welding and 2) the inability to weld thick section steels, both of which have impeded widespread use of FSW in manufacturing. Through this work, major advance has been made toward transforming FSW technology from a “specialty” process to a mainstream materials joining technology to realize its pervasive energy, environmental, and economic benefits across industry.

  8. Friction Stir Spot Welding of DP780 Carbon Steel

    Energy Technology Data Exchange (ETDEWEB)

    Santella, Michael L [ORNL; Hovanski, Yuri [ORNL; Frederick, David Alan [ORNL; Grant, Glenn J [ORNL; Dahl, Michael E [ORNL

    2010-01-01

    Friction stir spot welds were made in uncoated and galvannealed DP780 sheets using polycrystalline boron nitride stir tools. The tools were plunged at either a single continuous rate or in two segments consisting of a relatively high rate followed by a slower rate of shorter depth. Welding times ranged from 1 to 10 s. Increasing tool rotation speed from 800 to 1600 rev min{sup -1} increased strength values. The 2-segment welding procedures also produced higher strength joints. Average lap shear strengths exceeding 10 {center_dot} 3 kN were consistently obtained in 4 s on both the uncoated and the galvannealed DP780. The likelihood of diffusion and mechanical interlocking contributing to bond formation was supported by metallographic examinations. A cost analysis based on spot welding in automobile assembly showed that for friction stir spot welding to be economically competitive with resistance spot welding the cost of stir tools must approach that of resistance spot welding electrode tips.

  9. Læremiddelevaluering af web 2.0 læremidler

    DEFF Research Database (Denmark)

    Falkesgaard Slot, Marie; Gissel, Stig Toke

    2014-01-01

    Kapitlet etablerer og afprøver et analyseapparat, der bidrager til at højne kvaliteten af de valg, som foretages af web 2.0-læremidler i danskfaget. I kapitlet fokuseres der på læremiddel evaluering af nogle af de funktioner, som typisk tilskrives web 2.0-værktøjerne, ligesom der gives eksempler på...

  10. The new 2.0 l TDI {sup registered} to fulfill American emission standards in Volkswagens new Passat; Der neue 2,0l TDI {sup registered} zur Erfuellung der amerikanischen Emissionsgesetze in Volkswagens neuem Passat

    Energy Technology Data Exchange (ETDEWEB)

    Kahrstedt, Joern; Dorenkamp, Richard; Kuiken, Sander; Greiner, Michael; Kuehne, Ingo; Nigro, Giampaolo; Duesterdiek, Thorsten; Veldeten, Burkhard; Thoem, Norbert [Volkswagen AG, Wolfsburg (Germany)

    2011-07-01

    Volkswagen introduced the all-new Passat in 2011 at the Detroit Motor Show in the USA. It is a new midsize sedan designed exclusively for the American market and will be built at a completely new plant in Chattanooga, Tennessee. The second-generation 2.0l TDI {sup registered} engine familiar from Europe was extensively modified and further developed for the new Passat, in order to comply with the American BIN5/ULEV emission limits. For this purpose the engine's untreated emissions had to be lowered and, in combination with exhaust emission control by selective catalytic reduction (SCR), compliance with the emission limits throughout the car's operating life ensured. An effective measure for lowering the engine's untreated emissions has proved to be the low-pressure EGR system (LP EGR) [1] introduced on the first-generation 2.0l TDI {sup registered} BIN5 engine. In the course of ongoing development of the LP EGR system, work continued on reducing pressure losses in the system, and charge-air cooling was converted from air to water cooling. Water-cooled charge-air cooling enables intake pipe temperature control independent of ambient temperature, and due to the elimination of throttling and the associated reduction in volume improves road dynamics. Systematic elimination of throttling restrictions in the gas system, combined with improved turbocharging, led to a significant drop in fuel consumption and optimal road performance. As a means of stabilizing untreated emissions in the engine, cylinder-pressure control of combustion was carried-over from the first-generation 2.0l TDI BIN5 engine. Thanks to the closed-loop control of the indicated mean pressure and the centre of combustion with the pressure sensor integrated into the glow-plug, it was possible to minimize the influences of fluctuating fuel quality and component tolerances. The exhaust system was completely revised in order to achieve maximum NOX conversion in the SCR catalytic converter. The

  11. Friction Stir Processing of Cast Superalloys Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This SBIR Phase I effort examines the feasibility of an innovative fabrication technology incorporating sand casting and friction stir processing (FSP) for...

  12. Friction Stir Processing of Cast Superalloys Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This SBIR effort examines the feasibility of an innovative fabrication technology incorporating sand casting and friction stir processing (FSP) for producing...

  13. File list: Oth.ALL.20.L3MBTL2.AllCell [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available Oth.ALL.20.L3MBTL2.AllCell hg19 TFs and others L3MBTL2 All cell types SRX059371,SRX...059372 http://dbarchive.biosciencedbc.jp/kyushu-u/hg19/assembled/Oth.ALL.20.L3MBTL2.AllCell.bed ...

  14. Studies of stirred jujube yogurt

    Institute of Scientific and Technical Information of China (English)

    郑强强; 薛菊兰; 刘亚丽; 秦婷婷

    2014-01-01

    Jujube is a delicious sweet fruits, with the functions of anti-tumor, anti-cancer, anti-aging, reducing blood pressure, improving immunity and so on [1]. Yogurt is a kind of high nutritional value and special flavor drinks. Its protein is easily digested and absorbed, especial y calcium. In this experiment, dry jujube and fresh milk as the main material to obtain solidified yoghurt. Then researched how the amounts of solidified yoghurt, sugar, jujube slurry to effect the yogurt quality. The results showed that: the best proportion of stirred yogurt: jujube slurry 15%, sugar 4%and yoghurt85%.

  15. Pulsed ultrasonic stir welding method

    Science.gov (United States)

    Ding, R. Jeffrey (Inventor)

    2013-01-01

    A method of performing ultrasonic stir welding uses a welding head assembly to include a plate and a rod passing through the plate. The rod is rotatable about a longitudinal axis thereof. In the method, the rod is rotated about its longitudinal axis during a welding operation. During the welding operation, a series of on-off ultrasonic pulses are applied to the rod such that they propagate parallel to the rod's longitudinal axis. At least a pulse rate associated with the on-off ultrasonic pulses is controlled.

  16. Gimbaled-shoulder friction stir welding tool

    Science.gov (United States)

    Carter, Robert W. (Inventor); Lawless, Kirby G. (Inventor)

    2010-01-01

    A gimbaled-shoulder friction stir welding tool includes a pin and first and second annular shoulders coupled to the pin. At least one of the annular shoulders is coupled to the pin for gimbaled motion with respect thereto as the tool is rotated by a friction stir welding apparatus.

  17. Stirring a Bose-Einstein condensate

    Energy Technology Data Exchange (ETDEWEB)

    Damski, Bogdan [Instytut Fizyki Imienia Mariana Smoluchowskiego, Uniwersytet Jagiellonski, Cracow (Poland); Institut fuer Theoretische Physik, Universitaet Hannover, Hannover (Germany); Sacha, Krzysztof; Zakrzewski, Jakub [Instytut Fizyki Imienia Mariana Smoluchowskiego, Uniwersytet Jagiellonski, Cracow (Poland)

    2002-10-14

    By shining a tightly focused laser light on a Bose-Einstein condensate (BEC) and moving the centre of the beam along a spiral path one may stir the BEC and create vortices. It is shown that one can induce rotation of the BEC in the direction opposite to the direction of stirring. (author)

  18. Effects of mechanical force on grain structures of friction stir welded oxide dispersion strengthened ferritic steel

    Energy Technology Data Exchange (ETDEWEB)

    Han, Wentuo, E-mail: hanwentuo@hotmail.com [Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Kimura, Akihiko [Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Tsuda, Naoto [Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Serizawa, Hisashi [Joining and Welding Research Institute, Osaka University, Ibaraki, Osaka 567-0047 (Japan); Chen, Dongsheng [Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Je, Hwanil [Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Fujii, Hidetoshi [Joining and Welding Research Institute, Osaka University, Ibaraki, Osaka 567-0047 (Japan); Ha, Yoosung [Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Morisada, Yoshiaki [Joining and Welding Research Institute, Osaka University, Ibaraki, Osaka 567-0047 (Japan); Noto, Hiroyuki [Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan)

    2014-12-15

    The weldability of oxide dispersion strengthened (ODS) ferritic steels is a critical obstructive in the development and use of these steels. Friction stir welding has been considered to be a promising way to solve this problem. The main purpose of this work was to reveal the effects of mechanical force on grain structures of friction stir welded ODS ferritic steel. The grain appearances and the misorientation angles of grain boundaries in different welded zones were investigated by the electron backscatter diffraction (EBSD). Results showed that the mechanical force imposed by the stir tool can activate and promote the recrystallization characterized by the transformation of boundaries from LABs to HABs, and contribute to the grain refinement. The type of recrystallization in the stir zone can be classified as the continuous dynamic recrystallization (CDRX)

  19. Friction Stir Welding and Processing

    Energy Technology Data Exchange (ETDEWEB)

    Hovanski, Yuri; Carsley, John; Clarke, Kester D.; Krajewski, Paul E.

    2015-05-01

    With nearly twenty years of international research and collaboration in friction stir welding (FSW) and processing industrial applications have spread into nearly every feasible market. Currently applications exist in aerospace, railway, automotive, personal computers, technology, marine, cutlery, construction, as well as several other markets. Implementation of FSW has demonstrated diverse opportunities ranging from enabling new materials to reducing the production costs of current welding technologies by enabling condensed packaging solutions for traditional fabrication and assembly. TMS has sponsored focused instruction and communication in this technology area for more than fifteen years, with leadership from the Shaping and Forming Committee, which organizes a biannual symposium each odd year at the annual meeting. A focused publication produced from each of these symposia now comprises eight volumes detailing the primary research and development activities in this area over the last two decades. The articles assembled herein focus on both recent developments and technology reviews of several key markets from international experts in this area.

  20. Macrostructure of Friction Stir Welds

    Science.gov (United States)

    Aloor, S.; Nowak, B.; Vargas, R.; McClure, J. C.; Murr, L. E.; Nunes, A. C.; Munafo, Paul M. (Technical Monitor)

    2002-01-01

    This paper will discuss two of the well know large scale features of friction stir welds: the "onion rings" seen in transverse sections, and the striations on the surface of the work piece. It will be shown that the surface features (sometimes called "tool marks") are the result of irregularities on the rotating shoulder of the pin tool and disappear when the shoulder is polished. The "onion ring" structure seen in transverse cross sections is formed by parts of the "carousel", the zone of material adjacent to and rotating with the pin tool, that are shed off in each rotation. The relation between the carousel and the "ring vortex", a rotational flow extending both in and out of the carousel and resembling a smoke-ring with the hole centered on the pin tool, will be discussed.

  1. Modeling of material flow in friction stir welding process

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    This paper presents a 3D numerical model to study the material flow in the friction stir welding process. Results indicate that the material in front of the pin moves upwards due to the extrusion of the pin, and then the upward material rotates with the pin. Behind the rotating tool, the material starts to move downwards and to deposit in the wake. This process is the real cause to make friction stir welding process continuing successfully. The tangent movement of the material takes the main contribution to the flow of the material in friction stir welding process. There exists a swirl on the advancing side and with the increase of the translational velocity the inverse flow of the material on the advancing side becomes faster. The shoulder can increase the velocity of material flow in both radial direction and tangent direction near the top surface. The variations of process parameters do have an effect on the velocity field near the pin, especially in the region in which the material flow is faster.

  2. Recent Developments in Friction Stir Welding of Al-alloys

    Science.gov (United States)

    Çam, Gürel; Mistikoglu, Selcuk

    2014-06-01

    The diversity and never-ending desire for a better life standard result in a continuous development of the existing manufacturing technologies. In line with these developments in the existing production technologies the demand for more complex products increases, which also stimulates new approaches in production routes of such products, e.g., novel welding procedures. For instance, the friction stir welding (FSW) technology, developed for joining difficult-to-weld Al-alloys, has been implemented by industry in manufacturing of several products. There are also numerous attempts to apply this method to other materials beyond Al-alloys. However, the process has not yet been implemented by industry for joining these materials with the exception of some limited applications. The microstructures and mechanical properties of friction stir welded Al-alloys existing in the open literature will be discussed in detail in this review. The correlations between weld parameters used during FSW and the microstructures evolved in the weld region and thus mechanical properties of the joints produced will be highlighted. However, the modeling studies, material flow, texture formation and developments in tool design are out of the scope of this work as well as the other variants of this technology, such as friction stir spot welding (FSSW).

  3. Torque Control of Friction Stir Welding Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Longhurst Engineering, PLC and Vanderbilt University propose the innovation of torque control of friction stir welding (FSW) as a replacement to force control of...

  4. Investigation of Friction Stir Spot Welding Method

    OpenAIRE

    MERT, Şenol; MERT, Sevda

    2013-01-01

    The Friction Stir Spot Welding (FSSW) method is a derivative of the Friction Stir Welding (FSW) process, which is a new process that recently has received considerable attention from the automotive and other industries. In both methods, the joining mechanism is the same. However, there are several important differences between the applications. The most obvious difference FSSW than FSW that there is no translation of the tool in the vertical direction during the welding. The FSSW process cons...

  5. pH对发酵系统的产甲烷活性抑制及产氢强化%Enhancement of the fermentative hydrogen production in a continuous-flow stirred tank reactor by decreasing pH to inhibit methanogenesis

    Institute of Scientific and Technical Information of China (English)

    李建政; 苏晓煜; 昌盛; 张立国; 于泽

    2012-01-01

    To develop a feasible method for inhibiting methanogenesis while enhancing fermentative hydrogen production in anaerobic organic wastewater fermentation process, a continuous - flow stirred tank reactor (CSTR) a methane production feature was introduced and used as the base-line condition. The CSTR was op- erated at (35 ± 1 )℃ with an influent COD 7 000 mg/L and a hydraulic retention time (HRT) 8 h throughout the performance test. When the pH in the CSTR decreased from 6. 5 - 7.2 to 6. 0 - 6. 5, the methane yield decreased remarkably and could not be inspected in the biogas at last, while the percentage of hydrogen in bio- gas kept at a low level less than 3 %. When the CSTR operated with a lower pH 4. 0 -5.0, the acidogenesis was further enhanced with a total organic intermediate of 2 052 rag/L, dominated by ethanol and acetic acid, indicating a typical ethanol-type fermentation established in the CSTR. During the ethanol-type fermentation process, a biogas yield of 26 L/d was obtained with a hydrogen percentage about 45%. The specific hydrogen producing rate of the anaerobic activated sludge reached at 1.67 L/( g · d) averagely. Key words: organic wastewater; methanogenesis; fermentative hydrogen production; pH adjustment; continu- ous-flow stirred tank reactor (CSTR)%为抑制厌氧发酵系统的产甲烷活性,强化其发酵产氢性能,采用逐级降低pH的调控方法,探讨连续流搅拌槽式反应器(CSTR)从具有显著甲烷发酵特征的厌氧发酵系统向发酵产氢系统转变的运行特征.在进水COD7000mg/L、水力停留时间(HRT)8h条件下,发酵体系在pH由6.5~7.2降低到6.0~6.5时,虽然发酵气中的甲烷体积分数逐渐减少乃至消失,但氢气体积分数一直在3%以下;当pH下降到4.0~5.0时,系统中的产酸发酵作用得到了进一步强化,挥发性发酵产物总量平均为2052mg/L,呈现为典型的乙醇型发酵

  6. Robust Nonlinear Control of Continuous Stirred Tank Reactors

    Institute of Scientific and Technical Information of China (English)

    1998-01-01

    1IntroductionRobustcontrolofuncertainsystemsisacentralissueincontroltheory.Inthepastfewyearsmuchinteresthasbeendevotedtothede...

  7. Gimballed Shoulders for Friction Stir Welding

    Science.gov (United States)

    Carter, Robert; Lawless, Kirby

    2008-01-01

    In a proposed improvement of tooling for friction stir welding, gimballed shoulders would supplant shoulders that, heretofore, have been fixedly aligned with pins. The proposal is especially relevant to self-reacting friction stir welding. Some definitions of terms, recapitulated from related prior NASA Tech Briefs articles, are prerequisite to a meaningful description of the proposed improvement. In friction stir welding, one uses a tool that includes (1) a rotating shoulder on top (or front) of the workpiece and (2) a pin that rotates with the shoulder and protrudes from the shoulder into the depth of the workpiece. In conventional friction stir welding, the main axial force exerted by the tool on the workpiece is reacted through a ridged backing anvil under (behind) the workpiece. When conventional friction stir welding is augmented with an auto-adjustable pin-tool (APT) capability, the depth of penetration of the pin into the workpiece is varied in real time by a position- or forcecontrol system that extends or retracts the pin as needed to obtain the desired effect. In self-reacting (also known as self-reacted) friction stir welding as practiced heretofore, there are two shoulders: one on top (or front) and one on the bottom (or back) of the workpiece. In this case, a threaded shaft protrudes from the tip of the pin to beyond the back surface of the workpiece. The back shoulder is held axially in place against tension by a nut on the threaded shaft. Both shoulders rotate with the pin and remain aligned coaxially with the pin. The main axial force exerted on the workpiece by the tool and front shoulder is reacted through the back shoulder and the threaded shaft into the friction-stir-welding machine head, so that a backing anvil is no longer needed. A key transmits torque between the bottom shoulder and the threaded shaft, so that the bottom shoulder rotates with the shaft. This concludes the prerequisite definitions of terms.

  8. ISG20L1 is a p53 family target gene that modulates genotoxic stress-induced autophagy

    Directory of Open Access Journals (Sweden)

    Johnson Kimberly N

    2010-04-01

    Full Text Available Abstract Background Autophagy is characterized by the sequestration of cytoplasm and organelles into multimembrane vesicles and subsequent degradation by the cell's lysosomal system. It is linked to many physiological functions in human cells including stress response, protein degradation, organelle turnover, caspase-independent cell death and tumor suppression. Malignant transformation is frequently associated with deregulation of autophagy and several tumor suppressors can modulate autophagic processes. The tumor suppressor p53 can induce autophagy after metabolic or genotoxic stress through transcriptionally-dependent and -independent mechanisms. In this study we expand on the former mechanism by functionally characterizing a p53 family target gene, ISG20L1 under conditions of genotoxic stress. Results We identified a p53 target gene, ISG20L1, and show that transcription of the gene can be regulated by all three p53 family members (p53, p63, and p73. We generated an antibody to ISG20L1 and found that it localizes to the nucleolar and perinucleolar regions of the nucleus and its protein levels increase in a p53- and p73-dependent manner after various forms of genotoxic stress. When ectopically expressed in epithelial cancer-derived cell lines, ISG20L1 expression decreased clonogenic survival without a concomitant elevation in apoptosis and this effect was partially rescued in cells that were ATG5 deficient. Knockdown of ISG20L1 did not alter 5-FU induced apoptosis as assessed by PARP and caspase-3 cleavage, sub-G1 content, and DNA laddering. Thus, we investigated the role of ISG20L1 in autophagy, a process commonly associated with type II cell death, and found that ISG20L1 knockdown decreased levels of autophagic vacuoles and LC3-II after genotoxic stress as assessed by electron microscopy, biochemical, and immunohistochemical measurements of LC3-II. Conclusions Our identification of ISG20L1 as a p53 family target and discovery that modulation

  9. Deterministic Chaos in Open Well-stirred Bray-Liebhafsky Reaction System

    Science.gov (United States)

    Kolar-Anić, Ljiljana; Vukojević, Vladana; Pejić, Nataša; Grozdić, Tomislav; Anić, Slobodan

    2004-12-01

    Dynamics of the Bray-Liebhafsky (BL) oscillatory reaction is analyzed in a Continuously-fed well-Stirred Thank Reactor (CSTR). Deterministic chaos is found under different conditions, when temperature and acidity are chosen as control parameters. Dynamic patterns observed in real experiments are also numerically simulated.

  10. Stirring effects and bistability in the iodate-arsenous acid reaction: Premixed vs segregated flows

    Science.gov (United States)

    Hannon, L.; Horsthemke, W.

    1987-01-01

    Using a coalescence-dispersion model of the continuous flow-stirred tank reactor (CSTR), we study the effect of premixed vs nonpremixed reactant flows on chemical bistability. The region of bistability is smaller for segregated feed streams than for a fully premixed feed stream. The transition from flow branch to thermodynamic branch is particularly sensitive to the feed stream configuration.

  11. Mitigating Abnormal Grain Growth for Friction Stir Welded Al-Li 2195 Spun Formed Domes

    Science.gov (United States)

    Chen, Po-Shou; Russell, Carolyn

    2012-01-01

    Formability and abnormal grain growth (AGG) are the two major issues that have been encountered for Al alloy spun formed dome development using friction stir welded blanks. Material properties that have significant influence on the formability include forming range and strain hardening exponent. In this study, tensile tests were performed for two 2195 friction stir weld parameter sets at 400 F to study the effects of post weld anneal on the forming range and strain hardening exponent. It was found that the formability can be enhanced by applying a newly developed post weld anneal to heat treat the friction stir welded panels. This new post weld anneal leads to a higher forming range and much improved strain hardening exponent. AGG in the weld nugget is known to cause a significant reduction of ductility and fracture toughness. This study also investigated how AGG may be influenced by the heating rate to the solution heat treatment temperature. After post-weld annealing, friction stir welds were strained to 15% and 39% by compression at 400 F before they were subjected to SHT at 950 F for 1 hour. Salt bath SHT is very effective in reducing the grain size as it helps arrest the onset of AGG and promote normal recrystallization and grain growth. However, heat treating a 18 ft dome using a salt bath is not practical. Efforts are continuing at Marshall Space Flight Center to identify the welding parameters and heat treating parameters that can help mitigate the AGG in the friction stir welds.

  12. Acclimation of Methane-fermenting Anaerobic Flocs in a Continuous Flow Stirred Tank Reactor for Treating Beet-sugar Processing Wastewater%制糖废水CSTR甲烷发酵系统的污泥驯化与运行特征

    Institute of Scientific and Technical Information of China (English)

    李建政; 叶菁菁; 王卫娜; 马超; 昌盛

    2008-01-01

    与厌氧颗粒污泥相比,絮状悬浮活性污泥具有传质界面大、速度快的突出优点,但要形成具有完整甲烷发酵过程的微生物生态系统则比较困难.采用连续搅拌槽式反应器(Continuous flow Stirred-Tank Reactor,CSTR),探讨了制糖废水厌氧生物处理系统的絮状污泥驯化与运行特征.研究表明,以有机废水好氧处理工艺的剩余污泥为种泥,在接种量MLVSS为8.52g/L,温度为(35±1)℃,COD浓度为4000mg/L,HRT为18 h,系统pH值保持在6.5~7.5等条件下,CSTR可在84d左右形成具有完整甲烷发酵过程的絮状是浮厌氧活性污泥系统.CSTR甲烷发酵系统对负荷冲击表现出了良好的调节能力,在有机负荷从5.3 kg COD/(m3·d)提高到9.33 kg COD/(m3·d)时,反应系统可在16d内重新达到稳定运行状态,其出水COD可稳定在1100mg/L左右,COD去除率和产气量平均为84%和38L/d,发酵气中的CO2和CH4含量分别为41%和48%.

  13. A fundamental study on the structural integrity of magnesium alloys joined by friction stir welding

    Science.gov (United States)

    Rao, Harish Mangebettu

    The goal of this research is to study the factors that influence the physical and mechanical properties of lap-shear joints produced using friction stir welding. This study focuses on understanding the effect of tool geometry and weld process parameters including the tool rotation rate, tool plunge depth and dwell time on the mechanical performance of similar magnesium alloy and dissimilar magnesium to aluminum alloy weld joints. A variety of experimental activities were conducted including tensile and fatigue testing, fracture surface and failure analysis, microstructure characterization, hardness measurements and chemical composition analysis. An investigation on the effect of weld process conditions in friction stir spot welding of magnesium to magnesium produced in a manner that had a large effective sheet thickness and smaller interfacial hook height exhibited superior weld strength. Furthermore, in fatigue testing of friction stir spot welded of magnesium to magnesium alloy, lap-shear welds produced using a triangular tool pin profile exhibited better fatigue life properties compared to lap-shear welds produced using a cylindrical tool pin profile. In friction stir spot welding of dissimilar magnesium to aluminum, formation of intermetallic compounds in the stir zone of the weld had a dominant effect on the weld strength. Lap-shear dissimilar welds with good material mixture and discontinues intermetallic compounds in the stir zone exhibited superior weld strength compared to lap-shear dissimilar welds with continuous formation of intermetallic compounds in the stir zone. The weld structural geometry like the interfacial hook, hook orientation and bond width also played a major role in influencing the weld strength of the dissimilar lap-shear friction stir spot welds. A wide scatter in fatigue test results was observed in friction stir linear welds of aluminum to magnesium alloys. Different modes of failure were observed under fatigue loading including crack

  14. Microstructures of AZ91D alloy solidified during electromagnetic stirring

    Institute of Scientific and Technical Information of China (English)

    MAO Wei-min; ZHEN Zi-sheng; CHEN Hong-tao

    2005-01-01

    With the help of an electromagnetic stirring device self-made and alloy melt quenching technology,the effect of electromagnetic stirring parameters on the microstructures of semi-solid AZ91D alloy was mainly studied at the stirring frequency of 200 Hz.The experimental results show that when the stirring power rises,the primary α-Mg rosettes in the semi-solid melt will bear stronger man-made temperature fluctuation and the root remelting effect of the dendritic arms is promoted so that the spherical primary α-Mg grains become much more and rounder.If the stirring frequency is 200 Hz,the ideal semi-solid microstructure of AZ91D magnesium alloy can be obtained when the stirring power is increased to 6.0 kW.If the stirring frequency is 200 Hz and the stirring power is 6.0 kW,it is found that the lower cooling rate is favorable for the spherical primary α-Mg grains to be developed during the electromagnetic stirring stage.If the AZ91D magnesium alloy billet prepared during electromagnetic stirring at the stirring frequency of 200 Hz and the stirring power of 6.0 kW is reheated to the solidus and liquidus temperature region,the primary α-Mg grain's shape will get more spherical,so it is very advantageous to the semi-solid thixoforming process.

  15. Optimal stirring strategies for passive scalar mixing

    CERN Document Server

    Lin, Zhi; Doering, Charles R

    2011-01-01

    We address the challenge of optimal incompressible stirring to mix an initially inhomogeneous distribution of passive tracers. As a quantitative measure of mixing we adopt the $H^{-1}$ norm of the scalar fluctuation field, equivalent to the (square-root of the) variance of a low-pass filtered image of the tracer concentration field. First we establish that this is a useful gauge even in the absence of molecular diffusion: its vanishing as $t --> \\infty$ is evidence of the stirring flow's mixing properties in the sense of ergodic theory. Then we derive absolute limits on the total amount of mixing, as a function of time, on a periodic spatial domain with a prescribed instantaneous stirring energy or stirring power budget. We subsequently determine the flow field that instantaneously maximizes the decay of this mixing measure---when such a flow exists. When no such `steepest descent' flow exists (a possible but non-generic situation) we determine the flow that maximizes the growth rate of the $H^{-1}$ norm's de...

  16. Stirring the Ashes of Public Discourse.

    Science.gov (United States)

    Marinara, Martha

    Sylvia Plath's confessional poem, "Lady Lazarus" can be used to illustrate a connection between autobiography and social critique. "You poke and stir" among the institutions that form social relations--the educational system, the court system, the economic system--to find individuals whose lives, whose joys and pains, and struggles for survival…

  17. Friction Stir Welding of Aluminum Alloys

    Institute of Scientific and Technical Information of China (English)

    FU Zhi-hong; HE Di-qiu; WANG Hong

    2004-01-01

    Friction stir welding(FSW), a new solid-state welding technology invited in the early 1990s,enables us weld aluminum alloys and titanium alloys etc. The processing of FSW, the microstructure in FSW alloysand the factors influencing weld quality are introduced. The complex factors affecting the properties are researched.

  18. Assessment Of Joints Using Friction Stir Welding And Refill Friction Stir Spot Welding Methods

    OpenAIRE

    Lacki P.; Więckowski W.; Wieczorek P.

    2015-01-01

    FSW (Friction Stir Welding) and RFSSW (Refill Friction Stir Spot Welding) joints have been increasingly used in industrial practice. They successfully replace fusion-welded, riveted or resistance-welded joints. In the last two decades, dynamic development of this method has stimulated investigations of the fast methods for joint diagnostics. These methods should be non-destructive and easy to be used in technological processes. The methods of assessment of joint quality are expected to detect...

  19. Ferrous friction stir weld physical simulation

    Science.gov (United States)

    Norton, Seth Jason

    2006-04-01

    Traditional fusion welding processes have several drawbacks associated with the melting and solidification of metal. Weld defects associated with the solidification of molten metal may act as initiation sites for cracks. Segregation of alloying elements during solidification may cause local changes in resistance to corrosion. The high amount of heat required to produce the molten metal in the weld can produce distortion from the intended position on cooling. The heat from the electric arc commonly used to melt metal in fusion welds may also produce metal fumes which are a potential health hazard. Friction stir welding is one application which has the potential to make full thickness welds in a single pass, while eliminating fume, reducing distortion, and eliminating solidification defects. Currently the friction stir welding process is used in the aerospace industry on aluminum alloys. Interest in the process by industries which rely on iron and its alloys for structural material is increasing. While friction stir welding has been shown to be feasible with iron alloys, the understanding of friction stir welding process effects on these materials is in its infancy. This project was aimed to better that understanding by developing a procedure for physical simulation of friction stir welding. Friction stir weld material tracer experiments utilizing stainless steel markers were conducted with plates of ingot iron and HSLA-65. Markers of 0.0625" diameter 308 stainless steel worked well for tracing the end position of material moved by the friction stir welding tool. The markers did not produce measurable increases in the loading of the tool in the direction of travel. Markers composed of 0.25" diameter 304 stainless steel did not perform as well as the smaller markers and produced increased loads on the friction stir welding tool. The smaller markers showed that material is moved in a curved path around the tool and deposited behind the tool. Material near the surface

  20. The new 2,0-l high performance four-cylinder motor from Mercedes-AMG; Der neue 2,0-L-Hochleistungs-Vierzylindermotor von Mercedes-AMG

    Energy Technology Data Exchange (ETDEWEB)

    Gindele, Joerg; Ramsteiner, Thomas; Fischer, Juergen; Tschamon, Bertram [Mercedes-AMG GmbH, Affalterbach (Germany)

    2013-09-15

    To mark its entry into the compact class, Mercedes-AMG has developed a new 2.0-l four-cylinder gasoline engine based on the modular architecture of the Mercedes-Benz BlueDirect family of four-cylinder power units. Achieving the high power density of 133 kW/l required extensive modifications to be made, for example to the basic engine, air management, turbocharging and the exhaust system. (orig.)

  1. Friction Stir Welding of Shipbuilding Steel with Primer

    Directory of Open Access Journals (Sweden)

    José Azevedo

    2016-03-01

    Full Text Available Abstract Friction Stir Welding has proven its merits for welding of aluminium alloys and is focused in expanding its material database to steel and titanium and also to assess new joint configurations. The use of welded structures in shipbuilding industry has a long tradition and continuously seeks for innovation in terms of materials and processes maintaining, or even, reducing costs. Several studies have been performed in the past years on FSW of steel. However, just recently were reported defect-free welds, free of martensite with stable parameters in steel without Primer. FSW of steel with primer has not been addressed. This work aims to fulfil a knowledge gap related to the use of friction stir for welding shipbuilding steel by analysing the effect of welding parameters on the metallurgical characteristics and mechanical properties of welds obtained with an innovative FSW tool in joining steel plates with a primer. Welds were performed in 4mm thick GL-A36 steel plates painted with a zinc based primer followed by a detailed microscopic, chemical and mechanical analysis. The results that matching fatigue properties are obtained using this technique, in FSW of shipbuilding steel with Primer.

  2. Friction Stir Lap Welding: material flow, joint structure and strength

    Directory of Open Access Journals (Sweden)

    Z.W. Chen

    2012-12-01

    Full Text Available Friction stir welding has been studied intensively in recent years due to its importance in industrial applications. The majority of these studies have been based on butt joint configuration and friction stir lap welding (FSLW has received considerably less attention. Joining with lap joint configuration is also widely used in automotive and aerospace industries and thus FSLW has increasingly been the focus of FS research effort recently. number of thermomechancal and metallurgical aspects of FSLW have been studied in our laboratory. In this paper, features of hooking formed during FSLW of Al-to-Al and Mg-to-Mg will first be quantified. Not only the size measured in the vertical direction but hook continuity and hooking direction have been found highly FS condition dependent. These features will be explained taking into account the effects of the two material flows which are speed dependent and alloy deformation behaviour dependent. Strength values of the welds will be presented and how strength is affected by hook features and by alloy dependent local deformation behaviours will be explained. In the last part of the paper, experimental results of FSLW of Al-to-steel will be presented to briefly explain how joint interface microstructures affect the fracturing process during mechanical testing and thus the strength. From the results, tool positioning as a mean for achieving maximum weld strength can be suggested.

  3. 升流式厌氧污泥床和连续流搅拌槽式反应器的废水处理效能及产甲烷菌群组成的对比分析%Comparative Analysis of the Efficiency and the Methanogens Composition in Upflow Anaerobic Sludge Blanket and Continuous Stirred-Tank Reactor

    Institute of Scientific and Technical Information of China (English)

    张立国; 李建政; 班巧英; 许一平

    2012-01-01

    分别运行升流式厌氧污泥床(UASB)反应器和连续流搅拌槽式反应器(CSTR)并使其达到稳定运行状态,在有机负荷率(OLR)均为6.0kg·m-3·d-1的条件下,对比分析了二者在稳定期的运行特性和产甲烷菌群的组成.结果表明,UASB的化学需氧量(COD)去除率为95%,显著高于CSTR的COD去除率(84%).然而,CSTR系统中的活性污泥的比产甲烷速率(315L·kg-1·d-1)和比COD去除率(0.85kg·kg-1·d-1)则显著高于UASB的260L·kg-1·d-1和0.67kg·kg-1·d-1.采用聚合酶链式反应-变性梯度凝胶电泳(PCR-DGGE)指纹分析技术对系统稳定期的活性污泥进行分析的结果表明,UASB系统的优势产甲烷菌为Methanosaeta concilii 和 Methanospirillum hungatei,而CSTR系统中的优势产甲烷菌为Methanosarcina mazeii和Methanobacterium formicicum.污泥微生物群落组成及其代谢特征的不同是造成厌氧处理系统效能差异的内在原因.UASB和CSTR在COD去除效能和污泥比活性方面各有所长,在实际应用中,须根据废水水质和预期处理程度合理选用.%The efficiency and the methanogens composition in an Upflow Anaerobic Sludge Blanket (UASB) reactor and a Continuous Stirred-Tank Reactor (CSTR) are investigated after achieving steady states at the same Organic Loading Rate (OLR) of 6.0kg· m-3 · d-1. The results show that the average removal rate of COD reaches 95% in the UASB, significantly higher than 84% of the CSTR. However, the specific methane production rate and the specific COD removal rate of the activated sludge are SlSL·kg-1·d-1 and 0.85kg·kg-1·d-1, respectively, in the CSTR, notably higher than those of the UASB of 260L·kg-1·d-1 and 0.67kg· kg-1·d-1, respectively. The analysis of the methanogens composition of the activated sludge by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) indicates that Methanosaeta concilii and Methanospirillum hungatei are the dominant methanogens in the UASB, while

  4. Friction stir processing on carbon steel

    Energy Technology Data Exchange (ETDEWEB)

    Tarasov, Sergei Yu., E-mail: tsy@ispms.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055, Russia and National Research Tomsk Polytechnic University, Tomsk, 634050 (Russian Federation); Melnikov, Alexander G., E-mail: melnikov-ag@tpu.ru [National Research Tomsk Polytechnic University, Tomsk, 634050 (Russian Federation); Rubtsov, Valery E., E-mail: rvy@ispms.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation)

    2014-11-14

    Friction stir processing of medium carbon steel samples has been carried out using a milling machine and tools made of cemented tungsten carbide. Samples have been machined from 40 and 40X steels. The tools have been made in the shape of 5×5×1.5 mm and 3×3×1.5 mm tetrahedrons. The microstructure of stirred zone has been obtained using the smaller tool and consists of fine recrystallized 2-3 μm grains, whereas the larger tool has produced the 'onion-like' structures comprising hard quenched 'white' 500-600 MPa layers with 300-350 MPa interlayers of bainite needles. The mean values of wear intensity obtained after measuring the wear scar width were 0.02 mm/m and 0.001 mm/m for non-processed and processed samples, respectively.

  5. Friction Stir Spot Welding of Polymer Materials

    OpenAIRE

    Bekir ÇEVİK

    2014-01-01

    Polymer materials are engineering materials used for various industrial fields. Polymer processing and fabrication techniques have developed with the advancement of technology. Friction Stir Spot Welding (FSSW) is a solid-state process in joining thermoplastic materials. In the present work, the polymeric material (Polyethylene) has been made to join by FSSW process. 3 mm thickness polyethylene materials were used in the experiments. Welding process was carried out by rotating 460 and 900 rpm...

  6. Fuel property effects in stirred combustors

    Science.gov (United States)

    1980-01-01

    Soot formation in strongly backmixed combustion was investigated using the jet-stirred combustor (JSC). This device provided a combustion volume in which temperature and combustion were uniform. It simulated the recirculating characteristics of the gas turbine primary zone; it was in this zone where mixture conditions were sufficiently rich to produce soot. Results indicate that the JSC allows study of soot formation in an aerodynamic situation revelant to gas turbines.

  7. Ultrasonic stir welding process and apparatus

    Science.gov (United States)

    Ding, R. Jeffrey (Inventor)

    2009-01-01

    An ultrasonic stir welding device provides a method and apparatus for elevating the temperature of a work piece utilizing at least one ultrasonic heater. Instead of relying on a rotating shoulder to provide heat to a workpiece an ultrasonic heater is utilized to provide ultrasonic energy to the workpiece. A rotating pin driven by a motor assembly performs the weld on the workpiece. A handheld version can be constructed as well as a fixedly mounted embodiment.

  8. Thermal modelling of friction stir welding

    DEFF Research Database (Denmark)

    Schmidt, Henrik Nikolaj Blicher; Hattel, Jesper Henri

    2008-01-01

    The objective of the present work is to present the basic elements of the thermal modelling of friction stir welding as well as to clarify some of the uncertainties in the literature regarding the different contributions to the heat generation. Some results from a new thermal pseudomechanical model...... in which the temperature-dependent yield stress of the weld material controls the heat generation are also presented....

  9. Microstructure characterization of the stir zone of submerged friction stir processed aluminum alloy 2219

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Xiuli, E-mail: feng.97@osu.edu [Welding Engineering Program, Department of Materials Science and Engineering, The Ohio State University, Columbus, OH 43221 (United States); State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001 (China); Liu, Huijie, E-mail: liuhj@hit.edu.cn [State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001 (China); Lippold, John C., E-mail: lippold.1@osu.edu [Welding Engineering Program, Department of Materials Science and Engineering, The Ohio State University, Columbus, OH 43221 (United States)

    2013-08-15

    Aluminum alloy 2219-T6 was friction stir processed using a novel submerged processing technique to facilitate cooling. Processing was conducted at a constant tool traverse speed of 200 mm/min and spindle rotation speeds in the range from 600 to 800 rpm. The microstructural characteristics of the base metal and processed zone, including grain structure and precipitation behavior, were studied using optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Microhardness maps were constructed on polished cross sections of as-processed samples. The effect of tool rotation speed on the microstructure and hardness of the stir zone was investigated. The average grain size of the stir zone was much smaller than that of the base metal, but the hardness was also lower due to the formation of equilibrium θ precipitates from the base metal θ′ precipitates. Stir zone hardness was found to decrease with increasing rotation speed (heat input). The effect of processing conditions on strength (hardness) was rationalized based on the competition between grain refinement strengthening and softening due to precipitate overaging. - Highlights: • SZ grain size (∼ 1 μm) is reduced by over one order of magnitude relative to the BM. • Hardness in the SZ is lower than that of the precipitation strengthened BM. • Metastable θ′ in the base metal transforms to equilibrium θ in the stir zone. • Softening in the SZ results from a decrease of precipitation strengthening.

  10. Microstructure characterization of the stir zone of submerged friction stir processed aluminum alloy 2219

    International Nuclear Information System (INIS)

    Aluminum alloy 2219-T6 was friction stir processed using a novel submerged processing technique to facilitate cooling. Processing was conducted at a constant tool traverse speed of 200 mm/min and spindle rotation speeds in the range from 600 to 800 rpm. The microstructural characteristics of the base metal and processed zone, including grain structure and precipitation behavior, were studied using optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Microhardness maps were constructed on polished cross sections of as-processed samples. The effect of tool rotation speed on the microstructure and hardness of the stir zone was investigated. The average grain size of the stir zone was much smaller than that of the base metal, but the hardness was also lower due to the formation of equilibrium θ precipitates from the base metal θ′ precipitates. Stir zone hardness was found to decrease with increasing rotation speed (heat input). The effect of processing conditions on strength (hardness) was rationalized based on the competition between grain refinement strengthening and softening due to precipitate overaging. - Highlights: • SZ grain size (∼ 1 μm) is reduced by over one order of magnitude relative to the BM. • Hardness in the SZ is lower than that of the precipitation strengthened BM. • Metastable θ′ in the base metal transforms to equilibrium θ in the stir zone. • Softening in the SZ results from a decrease of precipitation strengthening

  11. Enhancement of the performance of an anaerobic sequencing batch reactor treating low-strength wastewater through implementation of a variable stirring rate program

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, J.A.D.; Pinto, A.G.; Ratusznei, S.M.; Gedraite, R. [Instituto Maua de Tecnologia (IMT), Sao Caetano do Sul, SP (Brazil). Escola de Engenharia. Dept. de Engenharia Quimica e de Alimentos]. E-mail: rodrigues@maua.br; Zaiat, M. [Sao Paulo Univ., Sao Carlos, SP (Brazil). Escola de Engenharia. Dept. de Hidraulica e Saneamento

    2004-09-01

    This work focuses on enhancement of the performance of an anaerobic sequencing batch reactor with a six-vertical-blade-disk-turbine impeller, containing granulated biomass treating low-strength synthetic wastewater, through a study of the feasibility of implementing a variable stirring rate program. The reactor was operated at 30 deg C and a six-hour cycle was used to treat approximately 2.0 L of the synthetic substrate with a chemical oxygen demand (COD) of nearly 500 mg/L. Two different stirring rate program were implemented: a constant rate of 50 rpm and a variable rate consisting of 75 rpm for one hour, 50 rpm for four hours and 25 rpm for 0.5 hour. The last 0.5 hour of the cycle was used for the settling step. In both cases, a very short start-up period and unfiltered and filtered substrate removal efficiencies of 81% and 88%, respectively, were attained. However, use of the variable stirring rate enhanced efficiency of the reactor dynamics without impairing biomass morphology, thus resulting in a reduction in the total cycle time and a possible decrease in energy consumption. Additionally, a simplified model of the anaerobic metabolic activity, using apparent kinetic parameters, was proposed as a consecutive first-order kinetic model with substrate and total volatile acid residual concentrations in order to analyze how the variable stirring rate affects reactor performance. (author)

  12. Enhancement of the performance of an anaerobic sequencing batch reactor treating low-strength wastewater through implementation of a variable stirring rate program

    Directory of Open Access Journals (Sweden)

    Rodrigues J. A. D.

    2004-01-01

    Full Text Available This work focuses on enhancement of the performance of an anaerobic sequencing batch reactor with a six-vertical-blade-disk-turbine impeller, containing granulated biomass treating low-strength synthetic wastewater, through a study of the feasibility of implementing a variable stirring rate program. The reactor was operated at 30ºC and a six-hour cycle was used to treat approximately 2.0 L of the synthetic substrate with a chemical oxygen demand (COD of nearly 500 mg/L. Two different stirring rate program were implemented: a constant rate of 50 rpm and a variable rate consisting of 75 rpm for one hour, 50 rpm for four hours and 25 rpm for 0.5 hour. The last 0.5 hour of the cycle was used for the settling step. In both cases, a very short start-up period and unfiltered and filtered substrate removal efficiencies of 81% and 88%, respectively, were attained. However, use of the variable stirring rate enhanced efficiency of the reactor dynamics without impairing biomass morphology, thus resulting in a reduction in the total cycle time and a possible decrease in energy consumption. Additionally, a simplified model of the anaerobic metabolic activity, using apparent kinetic parameters, was proposed as a consecutive first-order kinetic model with substrate and total volatile acid residual concentrations in order to analyze how the variable stirring rate affects reactor performance.

  13. Numerical simulation of friction stir welding

    Directory of Open Access Journals (Sweden)

    Mijajlović Miroslav

    2014-01-01

    Full Text Available Friction stir welding is a solid-state welding technique that utilizes thermo-mechanical influence of the rotating welding tool on parent material resulting with monolith joint-weld. On the contact of welding tool and parent material, significant stirring and deformation of parent material appears, and during this process mechanical energy is partially transformed into heat. The paper describes the software for the numerical simulation of friction stir welding developed at Mechanical Engineering Faculty, University of Nis. Numerical solution for estimation of welding plates temperature is estimated using finite difference method-explicit scheme with adaptive grid, considering influence of temperature on material's conductivity, contact conditions between welding tool and parent material, material flow around welding tool etc. The calculated results are in good agreement with the experimental results. [Projekat Ministarstva nauke Republike Srbije, br. TR35034: The research of modern non-conventional technologies application in manufacturing companies with the aim of increase efficiency of use, product quality, reduce of costs and save energy and materials

  14. Analysis and Comparison of Friction Stir Welding and Laser Assisted Friction Stir Welding of Aluminum Alloy

    OpenAIRE

    Sabina Luisa Campanelli; Giuseppe Casalino; Caterina Casavola; Vincenzo Moramarco

    2013-01-01

    Friction Stir Welding (FSW) is a solid-state joining process; i.e., no melting occurs. The welding process is promoted by the rotation and translation of an axis-symmetric non-consumable tool along the weld centerline. Thus, the FSW process is performed at much lower temperatures than conventional fusion welding, nevertheless it has some disadvantages. Laser Assisted Friction Stir Welding (LAFSW) is a combination in which the FSW is the dominant welding process and the laser pre-heats the we...

  15. Influence of vibrational treatment on thermomechanical response of material under conditions identical to friction stir welding

    Energy Technology Data Exchange (ETDEWEB)

    Konovalenko, Ivan S., E-mail: ivkon@ispms.tsc.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation); Konovalenko, Igor S., E-mail: igkon@ispms.tsc.ru; Kolubaev, Evgeniy A., E-mail: eak@ispms.tsc.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation); National Research Tomsk Polytechnic University, Tomsk, 634050 (Russian Federation); Dmitriev, Andrey I., E-mail: dmitr@ispms.tsc.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation); National Research Tomsk Polytechnic University, Tomsk, 634050 (Russian Federation); National Research Tomsk State University, Tomsk, 634050 (Russian Federation); Psakhie, Sergey G., E-mail: sp@ms.tsc.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation); National Research Tomsk State University, Tomsk, 634050 (Russian Federation)

    2015-10-27

    A molecular dynamics model was constructed to describe material loading on the atomic scale by the mode identical to friction stir welding. It was shown that additional vibration applied to the tool during the loading mode provides specified intensity values and continuous thermomechanical action during welding. An increase in additional vibration intensity causes an increase both in the force acting on the workpiece from the rotating tool and in temperature within the welded area.

  16. In-Space Friction Stir Welding Machine Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Longhurst Engineering, PLC, and Vanderbilt University propose an in-space friction stir welding (FSW) machine for joining complex structural aluminum components....

  17. Automated multisyringe stir bar sorptive extraction using robust montmorillonite/epoxy-coated stir bars.

    Science.gov (United States)

    Ghani, Milad; Saraji, Mohammad; Maya, Fernando; Cerdà, Víctor

    2016-05-01

    Herein we present a simple, rapid and low cost strategy for the preparation of robust stir bar coatings based on the combination of montmorillonite with epoxy resin. The composite stir bar was implemented in a novel automated multisyringe stir bar sorptive extraction system (MS-SBSE), and applied to the extraction of four chlorophenols (4-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol) as model compounds, followed by high performance liquid chromatography-diode array detection. The different experimental parameters of the MS-SBSE, such as sample volume, selection of the desorption solvent, desorption volume, desorption time, sample solution pH, salt effect and extraction time were studied. Under the optimum conditions, the detection limits were between 0.02 and 0.34μgL(-1). Relative standard deviations (RSD) of the method for the analytes at 10μgL(-1) concentration level ranged from 3.5% to 4.1% (as intra-day RSD) and from 3.9% to 4.3% (as inter-day RSD at 50μgL(-1) concentration level). Batch-to-batch reproducibility for three different stir bars was 4.6-5.1%. The enrichment factors were between 30 and 49. In order to investigate the capability of the developed technique for real sample analysis, well water, wastewater and leachates from a solid waste treatment plant were satisfactorily analyzed. PMID:27062720

  18. Stir zone microstructure and strain rate during Al 7075-T6 friction stir spot welding

    Science.gov (United States)

    Gerlich, A.; Avramovic-Cingara, G.; North, T. H.

    2006-09-01

    The factors determining the temperature, heating rate, microstructure, and strain rate in Al 7075-T6 friction stir spot welds are investigated. Stir zone microstructure was examined using a combination of transmission electron microscopy (TEM) and electron backscattered diffraction (EBSD) microscopy, while the strain rate during spot welding was calculated by incorporating measured temperatures and the average subgrain dimensions in the Zener-Hollomon relation. The highest temperature during friction stir spot welding (527 °C) was observed in spot welds made using a tool rotational speed of 3000 rpm. The stir zone regions comprised fine-grained, equiaxed, fully recrystallized microstructures. The calculated strain rate in Al 7075-T6 spot welds decreased from 650 to about 20 s-1 when the tool rotational speed increased from 1000 to 3000 rpm. It is suggested that the decrease in strain rate results when tool slippage occurs when the welding parameter settings facilitate transient local melting during the spot welding operation. Transient local melting and tool slippage are produced when the welding parameters produce sufficiently high heating rates and temperatures during spot welding. However, transient local melting and tool slippage is not produced in Al 7075-T6 spot welds made using a rotational speed of 1000 rpm since the peak temperature is always less than 475 °C.

  19. Automated multisyringe stir bar sorptive extraction using robust montmorillonite/epoxy-coated stir bars.

    Science.gov (United States)

    Ghani, Milad; Saraji, Mohammad; Maya, Fernando; Cerdà, Víctor

    2016-05-01

    Herein we present a simple, rapid and low cost strategy for the preparation of robust stir bar coatings based on the combination of montmorillonite with epoxy resin. The composite stir bar was implemented in a novel automated multisyringe stir bar sorptive extraction system (MS-SBSE), and applied to the extraction of four chlorophenols (4-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol) as model compounds, followed by high performance liquid chromatography-diode array detection. The different experimental parameters of the MS-SBSE, such as sample volume, selection of the desorption solvent, desorption volume, desorption time, sample solution pH, salt effect and extraction time were studied. Under the optimum conditions, the detection limits were between 0.02 and 0.34μgL(-1). Relative standard deviations (RSD) of the method for the analytes at 10μgL(-1) concentration level ranged from 3.5% to 4.1% (as intra-day RSD) and from 3.9% to 4.3% (as inter-day RSD at 50μgL(-1) concentration level). Batch-to-batch reproducibility for three different stir bars was 4.6-5.1%. The enrichment factors were between 30 and 49. In order to investigate the capability of the developed technique for real sample analysis, well water, wastewater and leachates from a solid waste treatment plant were satisfactorily analyzed.

  20. Tristability in the iodate-As(III) chemical system arising from a model of stirring and mixing effects

    Science.gov (United States)

    Ganapathisubramanian, N.

    1991-08-01

    The iodate-As(III) system which exhibits bistability in an ideal continuous flow stirred tank reactor (CSTR), exhibits tristability when subjected to the mixing model of Kumpinsky and Epstein [J. Chem. Phys. 82, 53 (1985)]. The cross flow between the major and minor reactors influences the system's lower hysteresis limit more than its upper hysteresis limit.

  1. Start-up of semi-continously operated and completely stirred dry fermentation pilot-scale biogas reactor

    OpenAIRE

    Virkkunen, Elina

    2009-01-01

    In the year 2008, MTT Agrifood Research Finland built a pilot scale biogas reactor of 4.5 cubic meters situated in Sotkamo research station. The aim is to develop a completely stirred and semi-continuously operated biogas reactor that handles solid biomass.

  2. Modelling of friction stir spot welding

    OpenAIRE

    Reilly, Aidan

    2013-01-01

    Friction stir spot welding (FSSW) is a solid-state welding process which is especially useful for joining precipitation-hardened aluminium alloys that undergo adverse property changes during fusion welding. It also has potential as an effective method for solid-state joining of dissimilar alloys. In FSSW, heat generation and plastic flow are strongly linked, and the scale of the process in time and space is such that it is difficult to separate and control the influence of all the relevant in...

  3. Friction stir welding of single crystal aluminium

    DEFF Research Database (Denmark)

    Fonda, Richard Warren; Wert, John A.; Reynolds, A.P.;

    2007-01-01

    Friction stir welds were prepared in different orientations in an aluminium single crystal. The welds were quenched to preserve the microstructure surrounding the tool and then electron backscattered diffraction was used to reveal the generation of grain boundaries and the evolution...... of crystallographic texture around the tool in each weld. The extent of both dynamic recrystallisation and conventional recrystallisation varied considerably as a function of weld orientation. As the base plate begins to interact with the deformation field surrounding the tool, regions of the single crystal rotate...

  4. Microstructure Characteristics and Apparent Viscosity of Hypereutectic Al-24%Si Alloy Melt During Semi-solid State Stirring

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The microstructural evolution and apparent viscosity of hypereutectic Al-24%Si alloy during semi-solid state shearing were studied with a Searte type viscometer. When the alloy melt was continuously stirred from 720℃ to eutectic temperature, the primary Si crystals were gradually changed from elongated platelets to near-spherical shapes. It was found that some nondendritic  -phase formed when the melt was stirred below 585℃. The experiment showed that the semi-solid stirring had strong effect on inhibiting the anisotropic growth of Si crystals during solidification. The apparent viscosity of the alloy melt increased slowly with the decreasing of temperature before the formation of nondendritic  -phase, which caused the dramatic increase of apparent viscosity.

  5. Friction Stir Welding at MSFC: Kinematics

    Science.gov (United States)

    Nunes, A. C., Jr.

    2001-01-01

    In 1991 The Welding Institute of the United Kingdom patented the Friction Stir Welding (FSW) process. In FSW a rotating pin-tool is inserted into a weld seam and literally stirs the faying surfaces together as it moves up the seam. By April 2000 the American Welding Society International Welding and Fabricating Exposition featured several exhibits of commercial FSW processes and the 81st Annual Convention devoted a technical session to the process. The FSW process is of interest to Marshall Space Flight Center (MSFC) as a means of avoiding hot-cracking problems presented by the 2195 aluminum-lithium alloy, which is the primary constituent of the Lightweight Space Shuttle External Tank. The process has been under development at MSFC for External Tank applications since the early 1990's. Early development of the FSW process proceeded by cut-and-try empirical methods. A substantial and complex body of data resulted. A theoretical model was wanted to deal with the complexity and reduce the data to concepts serviceable for process diagnostics, optimization, parameter selection, etc. A first step in understanding the FSW process is to determine the kinematics, i.e., the flow field in the metal in the vicinity of the pin-tool. Given the kinematics, the dynamics, i.e., the forces, can be targeted. Given a completed model of the FSW process, attempts at rational design of tools and selection of process parameters can be made.

  6. Friction Stir Welding Technology: Adapting NASA's Retractable Pin Tool

    OpenAIRE

    ECT Team, Purdue

    2007-01-01

    In late 1991, The Welding Institute (TWI), a British research and technology organization, invented and patented a welding process named Friction Stir Welding (FSW). Friction Stir Welding is a highly significant advancement in aluminum welding technology that can produce stronger, lighter, and more efficient welds than any previous process.

  7. Damage Tolerance Behavior of Friction Stir Welds in Aluminum Alloys

    Science.gov (United States)

    McGill, Preston; Burkholder, Jonathan

    2012-01-01

    Friction stir welding is a solid state welding process used in the fabrication of various aerospace structures. Self-reacting and conventional friction stir welding are variations of the friction stir weld process employed in the fabrication of cryogenic propellant tanks which are classified as pressurized structure in many spaceflight vehicle architectures. In order to address damage tolerance behavior associated with friction stir welds in these safety critical structures, nondestructive inspection and proof testing may be required to screen hardware for mission critical defects. The efficacy of the nondestructive evaluation or the proof test is based on an assessment of the critical flaw size. Test data describing fracture behavior, residual strength capability, and cyclic mission life capability of friction stir welds at ambient and cryogenic temperatures have been generated and will be presented in this paper. Fracture behavior will include fracture toughness and tearing (R-curve) response of the friction stir welds. Residual strength behavior will include an evaluation of the effects of lack of penetration on conventional friction stir welds, the effects of internal defects (wormholes) on self-reacting friction stir welds, and an evaluation of the effects of fatigue cycled surface cracks on both conventional and selfreacting welds. Cyclic mission life capability will demonstrate the effects of surface crack defects on service load cycle capability. The fracture data will be used to evaluate nondestructive inspection and proof test requirements for the welds.

  8. Validation of the revised STI-r method

    NARCIS (Netherlands)

    Steeneken, H.J.M.; Houtgast, T.

    2002-01-01

    The revised model for the speech transmission index (STIr, Speech Communication 28 (1999) 109), was validated with an independent set of 68 test conditions. For a subset of 18 conditions, including only additive noise and band-pass limiting, it was veri.ed that the STIr provides a good prediction of

  9. Steady-shear viscosity of stirred yogurts with varying ropiness

    NARCIS (Netherlands)

    Marle, van M.E.; Ende, van den D.; Kruif, de C.G.; Mellema, J.

    1999-01-01

    Stirred yogurt was viewed as a concentrated dispersion of aggregates consisting of protein particles. The steady-shear behavior of three types of stirred yogurt with varying ropiness was investigated experimentally. To describe the shear-dependent viscosity, a microrheological model was used which w

  10. Fluidization of potato starch in a stirred vibrating fluidized bed

    NARCIS (Netherlands)

    Kuipers, N.J M; Stamhuis, Eize; Beenackers, A.A C M

    1996-01-01

    A novel gas-solid reactor for cohesive C-powders such as potato starch is introduced, designed and characterized, the so-called stirred vibrating fluidized bed. The effects of a sinusoidal vibration of the gas distributor and/or stirring of the bed are investigated. The fluidization index, bed expan

  11. Gas hold-up in stirred tank reactors

    NARCIS (Netherlands)

    Yawalkar, A.A.; Pangarkar, V.G.; Beenackers, A.A C M

    2002-01-01

    Based on a study of the gas hold-up data for stirred tank reactor generated in the present work and the data available in the literature for large stirred tank reactors (T = 0.57 m to 2.7 m) equipped with disc turbines and pitched blade downflow turbines a correlation is presented which reliably pre

  12. Friction stir method for forming structures and materials

    Science.gov (United States)

    Feng, Zhili; David, Stan A.; Frederick, David Alan

    2011-11-22

    Processes for forming an enhanced material or structure are disclosed. The structure typically includes a preform that has a first common surface and a recess below the first common surface. A filler is added to the recess and seams are friction stir welded, and materials may be stir mixed.

  13. Certification of a weld produced by friction stir welding

    Energy Technology Data Exchange (ETDEWEB)

    Obaditch, Chris; Grant, Glenn J

    2013-10-01

    Methods, devices, and systems for providing certification of friction stir welds are disclosed. A sensor is used to collect information related to a friction stir weld. Data from the sensor is compared to threshold values provided by an extrinsic standard setting organizations using a certification engine. The certification engine subsequently produces a report on the certification status of the weld.

  14. Influence of Using Parameters on Stirring Uniformity of Mixer

    Institute of Scientific and Technical Information of China (English)

    LIU Honghai; MA Dengeheng

    2011-01-01

    Stirring uniformity of mixture depends not only on structural parameters of the mixer,motion parameters, but also to a large extent on the using parameters.Based on the analysis of the structure and working principle of mixer,these factors that affecting mixer performance was studied.The mathematical model of mixer performance characteristics was established by theoretical analysis,which associated with the mechanical structure, motion parameters and using parameters. According to the mathematical model,the effects of the mixer filling rate, stirring time,and other using parameters on the uniformity were studied. In each stirring cycle, the minimum number of revolutions formula for shaft was obtained. In addition,in different filling rates,the relationship between stirring shaft rotation laps and stirring uniformity was obtained too.Finally,full-scale experimental verification was conducted.

  15. High-Powered, Ultrasonically Assisted Thermal Stir Welding

    Science.gov (United States)

    Ding, Robert

    2013-01-01

    This method is a solid-state weld process capable of joining metallic alloys without melting. The weld workpieces to be joined by thermal stir welding (TSW) are drawn, by heavy forces, between containment plates past the TSW stir tool that then causes joining of the weld workpiece. TSW is similar to friction stir welding (FSW) in that material is heated into a plastic state (not melted) and stirred using a stir rod. The FSW pin tool is an integrated geometrical structure consisting of a large-diameter shoulder, and a smaller-diameter stir pin protruding from the shoulder. When the pin is plunged into a weld workpiece, the shoulder spins on the surface of the weld workpiece, thus inducing frictional heat into the part. The pin stirs the fraying surfaces of the weld joint, thus joining the weld workpiece into one structure. The shoulder and stir pin of the FSW pin tool must rotate together at a desired rotational speed. The induced frictional energy control and stir pin control of the pin tool cannot be de-coupled. The two work as one integrated unit. TSW, on the other hand, de-couples the heating and stirring of FSW, and allows for independent control of each process element. A uniquely designed induction coil heats the weld workpiece to a desired temperature, and once heated, the part moves into a stir rod whose RPM is also independently controlled. As the weld workpiece moves into the stir rod, the piece is positioned, or sandwiched, between upper and lower containment plates. The plate squeezes together, thus compressing the upper and lower surfaces of the weld workpiece. This compressive force, also called consolidation force, consolidates the plastic material within the weld nugget material as it is being stirred by the stir rod. The stir rod is positioned through the center of the top containment plate and protrudes midway through the opposite lower containment plate where it is mechanically captured. The upper and lower containment plates are separated by a

  16. Evolution of microstructure and mechanical properties in naturally aged 7050 and 7075 Al friction stir welds

    International Nuclear Information System (INIS)

    The microstructural and mechanical property evolution of friction stir welded 7050-T7651 and 7075-T651 Al alloys were examined as a function of room temperature (natural) aging for up to 67,920 h. During the range of aging times studied, transverse tensile strengths continuously increased, and are still increasing, with improvements of 24% and 29% measured for the 7050-T7651 and 7075-T651 Al alloy friction stir welds, respectively. Microstructural evolution within the weld nugget and heat-affected zone was evaluated with both transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). Formation of a high volume fraction of GP(II) zones produced a majority of the strength improvement within the weld nugget and HAZ regions. The rational for the microstructural changes are discussed in light of the mechanical properties.

  17. Simulation of 3D material flow in friction stir welding of AA6061-T6

    Institute of Scientific and Technical Information of China (English)

    Zhang Zhao; Zhang Hongwu

    2008-01-01

    This paper reports the numerical simulation of the 3D material flow in friction stir welding process by using finite element methods based on solid mechanics. It is found that the material flow behind the pin is much faster than that in front of the pin. The material in front of the pin moves upwards and then rotates with the pin due to the effect of the rotating tool. Behind of the pin, the material moves downwards. This process of material movement is the real cause to make the friction stir welding process continuing successfully. With the increase of the translational velocity or the rotational velocity of the pin, the material flow becomes faster.

  18. Horizontal stirring in the global ocean

    CERN Document Server

    Hernández-Carrasco, I; Hernández-García, E; Turiel, A

    2011-01-01

    Horizontal mixing and the distribution of coherent structures in the global ocean are analyzed using Finite-Size Lyapunov Exponents (FSLE), computed for the surface velocity field derived from the Ocean general circulation model For the Earth Simulator (OFES). FSLEs measure horizontal stirring and dispersion; additionally, the transport barriers which organize the oceanic flow can roughly be identified with the ridges of the FSLE field. We have performed a detailed statistical study, particularizing for the behaviour of the two hemispheres and different ocean basins. The computed Probability Distributions Functions (PDFs) of FSLE are broad and asymmetric. Horizontal mixing is generally more active in the northern hemisphere than in the southern one. Nevertheless the Southern Ocean is the most active ocean, and the Pacific the less active one. A striking result is that the main currents can be classified in two 'activity classes': Western Boundary Currents, which have broad PDFs with large FSLE values, and Eas...

  19. Ultrasonically-assisted Thermal Stir Welding System

    Science.gov (United States)

    Ding, R. Jeffrey (Inventor)

    2014-01-01

    A welding head assembly has a work piece disposed between its containment plates' opposing surfaces with the work piece being maintained in a plastic state thereof at least in a vicinity of the welding head assembly's stir rod as the rod is rotated about its longitudinal axis. The welding head assembly and the work piece experience relative movement there between in a direction perpendicular to the rod's longitudinal axis as the work piece is subjected to a compressive force applied by the containment plates. A first source coupled to the first containment plate applies a first ultrasonic wave thereto such that the first ultrasonic wave propagates parallel to the direction of relative movement. A second source coupled to the second containment plate applies a second ultrasonic wave thereto such that the second ultrasonic wave propagates parallel to the direction of relative movement.propagates parallel to the direction of relative movement.

  20. Thermomechanical Modelling of Friction Stir Welding

    DEFF Research Database (Denmark)

    Hattel, Jesper Henri; Schmidt, Henrik Nikolaj Blicher; Tutum, Cem Celal

    2009-01-01

    Friction Stir Welding (FSW) is a fully coupled thermomechanical process and should in general be modelled as such. Basically, there are two major application areas of thermomechanical models in the investigation of the FSW process: i) Analysis of the thermomechanical conditions such as e.g. heat...... generation and local material deformation (often referred to as flow) during the welding process itself. ii) Prediction of the residual stresses that will be present in the joint structure post to welding. While the former in general will call for a fully-coupled thermomechanical procedure, however...... for the FSW process at hand, the heat generation must either be prescribed analytically or based on a fully coupled analysis of the welding process itself. Along this line, a recently proposed thermal-pseudo-mechanical model is presented in which the temperature dependent yield stress of the weld material...

  1. Friction stir welding of copper alloys

    Institute of Scientific and Technical Information of China (English)

    Liu Shuhua; Liu Meng; Wang Deqing; Xu Zhenyue

    2007-01-01

    Copper plates,brass plates and copper/brass plates were friction stir welded with various parameters. Experimental results show that the microstructure of the weld is characterized by its much finer grains as contrasted with the coarse grains of parent materials and the heat-affected zones are very narrow. The microhardness of the copper weld is a little higher than that of parent plate. The microhardness of brass weld is about 25% higher than that of parent material. The tensile strength of copper joints increases with increasing welding speed in the test range. The range of parameters to obtain good welds for copper is much wider than that for brass. When different materials were welded, the position of copper plate before welding affected the quality of FSW joints. If the copper plate was put on the advancing side of weld, the good quality of weld could be got under proper parameters.

  2. Fundamentals of friction stir spot welding

    Science.gov (United States)

    Badarinarayan, Harsha

    The recent spike in energy costs has been a major contributor to propel the use of light weight alloys in the transportation industry. In particular, the automotive industry sees benefit in using light weight alloys to increase fuel efficiency and enhance performance. In this context, light weight design by replacing steel with Al and/or Mg alloys have been considered as promising initiatives. The joining of structures made of light weight alloys is therefore very important and calls for more attention. Friction Stir Spot Welding (FSSW) is an evolving technique that offers several advantages over conventional joining processes. The fundamentals aspects of FSSW are systematically studied in this dissertation. The effects and influence of process inputs (weld parameters and tool geometry) on the process output (weld geometry and static strength) is studied. A Design of Experiments (DoE) is carried out to identify the effect of each process parameter on weld strength. It is found that the tool geometry, and in particular the pin profile has a significant role in determining the weld geometry (hook, stir zone size etc.) which in turn influences the failure mode and weld strength. A novel triangular pin tool geometry is proposed that suppresses the hook formation and produces welds with twice the static strength as those produced with conventional cylindrical pin tools. An experimental and numerical approach is undertaken to understand the effect of pin geometry on the material flow and failure mechanism of spot welds. In addition, key practical issues have been addressed such as quantification of tool life and a methodology to control tool plunge depth during welding. Finally, by implementing the findings of this dissertation, FSSW is successfully performed on a closure panel assembly for an automotive application.

  3. Textures in Single-Crystal Aluminum Friction Stir Spot Welds

    Science.gov (United States)

    Shibayanagi, Toshiya; Gerlich, Adrian P.; Kashihara, Keizo; North, Thomas H.

    2009-04-01

    The present article examines the textural features produced during friction stir spot welding of single-crystal aluminum sheet. The crystal has the {111} plane perpendicular to the normal direction (ND) of the sheet, and the leftFriction stir spot welding was carried out using a rotation speed of 1500 rpm and a dwell time of 2 seconds, and completed spot welds were characterized using a combination of optical microscopy and electron backscatter diffraction (EBSD). The EBSD measurements indicate there are no significant changes in orientation in locations more than 840 μm from the stir-zone extremity. The orientation distribution in the thermomechanically-affected zone (TMAZ) region conformed with the {110}⊥ND orientation within 580 μm of the stir-zone extremity. In the location immediately adjacent to the stir-zone extremity, there was a deviation from the {110}//ND orientation due to a combination of compressive loading perpendicular to the stir-zone boundary and shear loading in the direction of tool rotation. It is suggested a {111}⊥ND texture in the stir zone is associated with material flow imposed by the thread on the rotating pin.

  4. In-process discontinuity detection during friction stir welding

    Science.gov (United States)

    Shrivastava, Amber

    The objective of this work is to develop a method for detecting the creation of discontinuities (e.g., voids) during friction stir welding. Friction stir welding is inherently cost-effective, however, the need for significant weld inspection can make the process cost-prohibitive. A new approach to weld inspection is required -- where an in-situ characterization of weld quality can be obtained, reducing the need for post-process inspection. Friction stir welds with discontinuity and without discontinuity were created. In this work, discontinuities are generated by reducing the friction stir tool rotation frequency and increasing the tool traverse speed in order to create "colder" welds. During the welds, forces are measured. Discontinuity sizes for welds are measured by computerized tomography. The relationship between the force transients and the discontinuity sizes indicate that the force measurement during friction stir welding can be effectively used for detecting discontinuities in friction stir welds. The normalized force transient data and normalized discontinuity size are correlated to develop a criterion for discontinuity detection. Additional welds are performed to validate the discontinuity detection method. The discontinuity sizes estimated by the force measurement based method are in good agreement with the discontinuity sizes measured by computerized tomography. These results show that the force measurement based discontinuity detection model method can be effectively used to detect discontinuities during friction stir welding.

  5. Friction stir processing on high carbon steel U12

    Energy Technology Data Exchange (ETDEWEB)

    Tarasov, S. Yu., E-mail: tsy@ispms.ru; Rubtsov, V. E., E-mail: rvy@ispms.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation); National Research Tomsk Polytechnic University, Tomsk, 634050 (Russian Federation); Melnikov, A. G., E-mail: melnikov-ag@tpu.ru [National Research Tomsk Polytechnic University, Tomsk, 634050 (Russian Federation)

    2015-10-27

    Friction stir processing (FSP) of high carbon steel (U12) samples has been carried out using a milling machine and tools made of cemented tungsten carbide. The FSP tool has been made in the shape of 5×5×1.5 mm. The microstructural characterization of obtained stir zone and heat affected zone has been carried out. Microhardness at the level of 700 MPa has been obtained in the stir zone with microstructure consisting of large grains and cementitte network. This high-level of microhardness is explained by bainitic reaction developing from decarburization of austenitic grains during cementite network formation.

  6. Applications of Friction Stir Processing during Engraving of Soft Materials

    Directory of Open Access Journals (Sweden)

    V. Kočović

    2015-12-01

    Full Text Available Friction stir processing has extensive application in many technological operations. Application area of friction stir processing can be extended to the processing of non-metallic materials, such as wood. The paper examines the friction stir processing contact between a specially designed hard and temperature-resistant rotating tool and workpiece which is made of wood. Interval of speed slip and temperature level under which the combustion occurs and carbonization layer of soft material was determined. The results of the research can be applied in technological process of wood engraving operations which may have significant technological and aesthetic effects.

  7. Friction stir processing on high carbon steel U12

    International Nuclear Information System (INIS)

    Friction stir processing (FSP) of high carbon steel (U12) samples has been carried out using a milling machine and tools made of cemented tungsten carbide. The FSP tool has been made in the shape of 5×5×1.5 mm. The microstructural characterization of obtained stir zone and heat affected zone has been carried out. Microhardness at the level of 700 MPa has been obtained in the stir zone with microstructure consisting of large grains and cementitte network. This high-level of microhardness is explained by bainitic reaction developing from decarburization of austenitic grains during cementite network formation

  8. Stir frit microextraction: an approach for the determination of volatile compounds in water by headspace-gas chromatography/mass spectrometry.

    Science.gov (United States)

    Roldán-Pijuán, M; Alcudia-León, M C; Lucena, R; Cárdenas, S; Valcárcel, M

    2012-08-17

    In this article, a novel extraction approach, called stir frit microextraction (SFME), is presented. The new approach combines the extractive capability of a commercial polyethylene frit (20 μm of pore size) with the stirring in the same device. The proposed extraction procedure allows the determination of benzene, toluene, ethylbenzene, xylene isomers and styrene (BTEX-S) in water samples. The analytes are extracted on the frit, previously conditioned with methanol, under continuous magnetic stirring. Once the extraction is performed, the frit is transferred to a headspace vial where the volatile compounds are desorbed from the frit (90 °C, 30 min) in a headspace module and analyzed by gas chromatography/mass spectrometry. Headspace conditions (time and temperature) as well as extraction conditions (ionic strength, type of stirring, extraction time, stirring rate and sample volume) have been systematically evaluated. The method was characterized on the basis of its linearity, sensitivity and precision. Limits of detection were in the range from 18 ng/L (o-xylene) to 65 ng/L (benzene). The repeatability of the proposed method, expressed as relative standard deviation (RSD) varied between 3.8% (toluene) and 8.2% (m- and p-xylene). The recovery study carried out in different water samples provided an average recovery of 94%, which demonstrated the applicability of the stir frit microextraction for the analytical problem selected in this article. PMID:22771255

  9. Friction-Stir-Welded and Spin-Formed End Domes for Cryogenic Tanks

    Science.gov (United States)

    Hales, S. J.; Tayon, W. A.; Domack, M. S.

    2012-01-01

    Manufacturing of single-piece end domes for cryogenic tanks employing spin forming of tailored, friction-stir-welded blanks of Al-Li alloy 2195 plate offers cost and reliability benefits. The introduction of plastic deformation into a friction stir weld is a unique feature of the proposed manufacturing route. This investigation addressed abnormal grain growth [AGG] within the friction stir weldments during postfabrication processing of a prototype dome. The phenomenon of AGG was observed during the solution heat treatment [SHT] phase of T8 tempering and is a major concern for meeting specifications. Such abrupt microstructural transitions can be detrimental to notch-sensitive mechanical properties, such as ductility and/or fracture toughness. If the issue of AGG cannot be resolved, then the acceptance of this approach as a viable manufacturing route may be in jeopardy. The innovative approach adopted in this investigation was the insertion of a stand-alone, Intermediate Annealing Treatment [IAT] between the spin forming and T8 processing operations. A simple, recovery annealing step was deemed to be the most readily-scalable solution when fabricating thin-walled, ellipsoidal domes. The research effort culminated in the development of an effective IAT, which resulted in a significant decrease in AGG following SHT. The processing philosophy adopted in designing the IAT is outlined and the microstructural reasons for success are discussed. The analytical results presented are consistent with promoting continuous grain growth during the IAT, thereby suppressing AGG during the SHT.

  10. The Effect of Tool Position for Aluminum and Copper at High Rotational Friction Stir Welding

    Directory of Open Access Journals (Sweden)

    Recep Çakır

    2015-12-01

    Full Text Available Friction Stir Welding (FSW is a solid state welding process used for welding similar and dissimilar materials. This welding technique allows welding of Aluminum alloys which present difficulties in fusion joining and allows different material couples to be welded continuously. In this study, 1050 aluminum alloy and commercially pure copper to increase heat input were produced at high rotation rate (2440 rev/min with four different pin position (0-1-1.5-2 mm and three different weld speeds (20-30-50 mm/min by friction stir welding. The influence of welding parameters on microstructure and mechanical properties of the joints was investigated. Tensile and bending tests and microhardness measurements were used to determine of mechanical properties. Nugget zone microstructures were investigated by optical microscope and scanning electron microscope (SEM and were analyzed in energy-dispersive X-ray spectroscopy (EDX. Depending on the XRD analysis results intermetallic phase was observed to form in the interfacial region. In the tensile test results, 83.55% weld performance was obtained in the friction stir welding merge of Al-Cu.

  11. A novel milliliter-scale chemostat system for parallel cultivation of microorganisms in stirred-tank bioreactors.

    Science.gov (United States)

    Schmideder, Andreas; Severin, Timm Steffen; Cremer, Johannes Heinrich; Weuster-Botz, Dirk

    2015-09-20

    A pH-controlled parallel stirred-tank bioreactor system was modified for parallel continuous cultivation on a 10 mL-scale by connecting multichannel peristaltic pumps for feeding and medium removal with micro-pipes (250 μm inner diameter). Parallel chemostat processes with Escherichia coli as an example showed high reproducibility with regard to culture volume and flow rates as well as dry cell weight, dissolved oxygen concentration and pH control at steady states (n=8, coefficient of variation bioreactor on a liter-scale. Thus, parallel and continuously operated stirred-tank bioreactors on a milliliter-scale facilitate timesaving and cost reducing steady state studies with microorganisms. The applied continuous bioreactor system overcomes the drawbacks of existing miniaturized bioreactors, like poor mass transfer and insufficient process control.

  12. Friction stir processing (FSP: refining microstructures and improving properties

    Directory of Open Access Journals (Sweden)

    McNelley, T. R.

    2010-12-01

    Full Text Available FSP is reviewed as an allied technology of friction stir welding (FSW and additional considerations such as processing pattern and step over distance are introduced. The application of FSP to continuously cast AA5083 material in the as-cast condition is described and the extent of grain refinement and homogenization of microstructure is documented. The FSP-induced superplastic response of this material is compared to the response of conventionally processed AA5083 and the improved ductility of the FSP material is related to grain refinement and microstructure homogenization.

    Se revisa el procesado por fricción batida (FSP como un aliado tecnológico de la soldadura por fricción batida (FSW y se introducen consideraciones adicionales tales como el patrón de procesado y el paso en función de la distancia. Se describe la aplicación de FSP al material AA5083 por colada continua en la condición de colada y se documenta el grado de afino de grano y homogeneización de la microestructura. La respuesta de superplasticidad inducida por FSP se compara con la respuesta de la aleación AA5083 procesada convencionalmente y la mejora de ductilidad del material FSP se relaciona con el afino de grano y la homogeneización de la microestructura.

  13. Continuous wok-frying of vegetables:

    DEFF Research Database (Denmark)

    Adler-Nissen, Jens

    2007-01-01

    A new process for continuous stir-frying in industrial scale has been developed for producing convenience high-quality vegetables. The understanding of the dynamics of heat and mass transfer during stir-frying is crucial for up-scaling and controlling the process. The effect of different factors...... of loosely bound water from the vegetables allows the products to be frozen and re-heated without drip loss, and it is also an advantage when using them as ingredients in composite foods, such as pâtés. Examples developed by a professional chef indicate that he saved up to half of the cooking time compared...

  14. Reconstruction of Clear-PEM data with STIR

    CERN Document Server

    Martins, M V; Rodrigues, P; Trindade, A; Oliveira, N; Correia, M; Cordeiro, H; Ferreira, N C; Varela, J; Almeida, P

    2006-01-01

    The Clear-PEM scanner is a device based on planar detectors that is currently under development within the Crystal Clear Collaboration, at CERN. The basis for 3D image reconstruction in Clear-PEM is the software for tomographic image reconstruction (STIR). STIR is an open source object-oriented library that efficiently deals with the 3D positron emission tomography data sets. This library was originally designed for the traditional cylindrical scanners. In order to make its use compatible with planar scanner data, new functionalities were introduced into the library's framework. In this work, Monte Carlo simulations of the Clear-PEM scanner acquisitions were used as input for image reconstruction with the 3D OSEM algorithm available in STIR. The results presented indicate that dual plate PEM data can be accurately reconstructed using the enhanced STIR framework.

  15. STIR applied to the evaluation of dermatologic lesions

    International Nuclear Information System (INIS)

    This paper reports on the evaluation of dermatologic disorders using the short-inversion time-inversion-recovery (STIR) technique. The series included 20 cases, including five cavernous hemangiomas, three lymphangiomas, three melanomas, and nine others. Pulse sequences for STIR were TR/IR/TE = 1,500/100/30--40 (repetition time/inversion-recovery time/echo time, msec) 0.5 and 0.6 T) and TR/IR/TE = 1,500--2,000/200/22 (1.5 T). The images were evaluated for the extent and nature of the lesions. In all cases, STIR was valuable in discriminating lesions from subcutaneous fat tissues; in all cases of cavernous hemangioma and lymphangioma (in which lesions were shown by areas of high intensity) and in children (in whom Gd-DTPA studies were not applicable). Two melanomas were isointense in STIR as well as in T1- and T2-weighted images

  16. Low temperature friction stir welding of P91 steel

    Directory of Open Access Journals (Sweden)

    Prasad Rao Kalvala

    2016-08-01

    Full Text Available Bead-on-plate friction stir welds were made on P91 alloy with low and high rotational speeds (100 and 1000 RPM to study their effects on weld microstructural changes and impression creep behavior. Temperatures experienced by the stir zone were recorded at the weld tool tip. Different zones of welds were characterized for their microstructural changes, hardness and creep behavior (by impression creep tests. The results were compared with submerged arc fusion weld. Studies revealed that the stir zone temperature with 100 RPM was well below Ac1 temperature of P91 steel while it was above Ac3 with 1000 RPM. The results suggest that the microstructural degradation in P91 welds can be controlled by low temperature friction stir welding technique.

  17. Friction Stir Processing for Efficient Manufacturing

    Energy Technology Data Exchange (ETDEWEB)

    Mr. Christopher B. Smith; Dr. Oyelayo Ajayi

    2012-01-31

    Friction at contacting surfaces in relative motion is a major source of parasitic energy loss in machine systems and manufacturing processes. Consequently, friction reduction usually translates to efficiency gain and reduction in energy consumption. Furthermore, friction at surfaces eventually leads to wear and failure of the components thereby compromising reliability and durability. In order to reduce friction and wear in tribological components, material surfaces are often hardened by a variety of methods, including conventional heat treatment, laser surface hardening, and thin-film coatings. While these surface treatments are effective when used in conjunction with lubrication to prevent failure, they are all energy intensive and could potentially add significant cost. A new concept for surface hardening of metallic materials and components is Friction Stir Processing (FSP). Compared to the current surface hardening technologies, FSP is more energy efficient has no emission or waste by products and may result in better tribological performance. FSP involves plunging a rotating tool to a predetermined depth (case layer thickness) and translating the FSP tool along the area to be processed. This action of the tool produces heating and severe plastic deformation of the processed area. For steel the temperature is high enough to cause phase transformation, ultimately forming hard martensitic phase. Indeed, FSP has been used for surface modification of several metals and alloys so as to homogenize the microstructure and refine the grain size, both of which led to improved fatigue and corrosion resistance. Based on the effect of FSP on near-surface layer material, it was expected to have beneficial effects on friction and wear performance of metallic materials. However, little or no knowledge existed on the impact of FSP concerning friction and wear performance the subject of the this project and final report. Specifically for steel, which is the most dominant

  18. Fatigue Strength of Friction Stir Welded Joints in Aluminium

    OpenAIRE

    Ericsson, Mats

    2005-01-01

    Solid state Friction stir welding (FSW) is of major interest in the welding of aluminium since it improves the joint properties. Many applications where Al-alloys are used are subject to varying load conditions, making fatigue failure a critical issue. In the scope of this thesis, the fatigue performance of friction stir welded AlMgSi-alloy 6082 has been investigated. Static and dynamic properties of different joint configurations and welds produced with varying process parameters have been d...

  19. Friction stir processing / welding of NiAl bronzes

    OpenAIRE

    McNelley, Terry; Menon, Sarath

    2016-01-01

    Research Project Friction stir processing (FSP) of as-cast NiAl bronzes converts the as-cast microstructure to a wrought condition in the volume of materials subjected to the process. This results in improved properties in the absence of component shape change. With the development of portable systems, friction stir processing may enable in situ repair of defective components such as propellers and thus avoid expensive procedures such as dry docking for such repairs.

  20. The effect of mechanical stirring on horizontal convection

    OpenAIRE

    R. Tailleux; Rouleau, L

    2010-01-01

    An important experimental result, as yet poorly understood, is that mechanical stirring can significantly enhance the strength of horizontal convection. A contentious issue is whether this necessarily implies that the mechanical stirring replaces the buoyancy forcing as the main source of energy driving the observed overturning circulation, as has been suggested for the Atlantic meridional overturning circulation (AMOC). In this paper, rigorous energetics considerations and idealized numerica...

  1. Magnetic Properties of Friction Stir Processed Composite

    Science.gov (United States)

    Das, Shamiparna; Martinez, Nelson Y.; Das, Santanu; Mishra, Rajiv S.; Grant, Glenn J.; Jana, Saumyadeep; Polikarpov, Evgueni

    2016-07-01

    Of the many existing inspection or monitoring systems, each has its own advantages and drawbacks. These systems are usually comprised of semi-remote sensors that frequently cause difficulty in reaching complex areas of a component. This study proposes to overcome that difficulty by developing embedded functional composites, so that embedding can be achieved in virtually any component part and periodically can be interrogated by a reading device. The "reinforcement rich" processed areas can then be used to record properties such as strain, temperature, and stress state, to name a few, depending on the reinforcement material. Friction stir processing was used to fabricate a magnetostrictive composite by embedding galfenol particles into a nonmagnetic aluminum matrix. The aim was to develop a composite that produces strain in response to a varying magnetic field. Reinforcements were distributed uniformly in the matrix. Magnetization curves were studied using a vibrating sample magnetometer. A simple and cost-effective setup was developed to measure the magnetostrictive strain of the composites. Important factors affecting the magnetic properties were identified and the processing route was modified to improve the magnetic response.

  2. Impeller Submergence Depth for Stirred Tanks

    Directory of Open Access Journals (Sweden)

    Thiyam T. Devi

    2011-11-01

    Full Text Available Impeller submergence governs the performance of mixing tanks employed in oxygen transfer operation. Present work experimentally investigates the effect of impeller submergence depths on oxygen transfer and corresponding power consumption. It has been found that at higher range of impeller submergence, mixing tanks consume less power and gives higher values of oxygen transfer coefficient. Optimal range of submergence depth is 0.7 to 0.9 times the impeller diameter. Copyright ©2011 BCREC UNDIP. All rights reserved.(Received: 4th March 2011; Revised: 12nd July 2011; Accepted: 14th July 2011[How to Cite: T.T. Devi, A.P. Sinha, M. Thakre, and B. Kumar. (2011. Impeller Submergence Depth for Stirred Tanks. Bulletin of Chemical Reaction Engineering & Catalysis, 6 (2: 123-128. doi:10.9767/bcrec.6.2.826.123-128][How to Link / DOI: http://dx.doi.org/10.9767/bcrec.6.2.826.123-128 || or local: http://ejournal.undip.ac.id/index.php/bcrec/article/view/826] | View in 

  3. Inspecting Friction Stir Welding using Electromagnetic Probes

    Science.gov (United States)

    Kinchen, David G.

    2004-01-01

    A report describes the use of advanced electromagnetic probes to measure the dimensions, the spatial distribution of electrical conductivity, and related other properties of friction stir welds (FSWs) between parts made of the same or different aluminum alloy(s). The probes are of the type described in in another Tech Brief. To recapitulate: A probe of this type is essentially an eddy-current probe that includes a primary (driver) winding that meanders and multiple secondary (sensing) windings that meander along the primary winding. Electrical conductivity is commonly used as a measure of heat treatment and tempering of aluminum alloys, but prior to the development of these probes, the inadequate sensitivity and limited accuracy of electrical-conductivity probes precluded such use on FSWs between different aluminum alloys, and the resolution of those probes was inadequate for measurement of FSW dimensions with positions and metallurgical properties. In contrast, the present probes afford adequate accuracy and spatial resolution for the purposes of measuring the dimensions of FSW welds and correlating spatially varying electrical conductivities with metallurgical properties, including surface defects.

  4. Nondestructive Ultrasonic Inspection of Friction Stir Welds

    Science.gov (United States)

    Tabatabaeipour, M.; Hettler, J.; Delrue, S.; Van Den Abeele, K.

    Friction Stir Welding (FSW) is a relatively new solid-state welding procedure developed at The Welding Institute (TWI-UK) and the technique is widely employed for welding aluminum alloys in various applications. In order to examine the quality of the welds and to detect a variety of welding flaws such as wormholes and root-flaws, it is required to develop a methodical inspection technique that can be used for the identification and localization of such defects. The most prevalent and risky defect in this type of welding is the barely visible root flaw with a length varying from 100-700 μm. Due to the extreme characteristics of the flaw, off-the-shelf ultrasonic weld inspection methods are not always able to readily detect this type of minute defect feature. Here, we propose a novel approach to characterize root flaws using an oblique incident ultrasonic C-scan backscattering analysis. The implementation consists of an immersion ultrasonic testing method in pulse echo (i.e. backscatter) mode with a 3.5 MHz transducer, and makes use of an empirical procedure to engender of a shear wave dominated excitation at the root surface, and to properly gate the received signal for root flaw examination. By scanning the surface above the welded component, a C-scan image displaying the backscatter response from the root surface of the nugget zone can be obtained which allows a simple interpretation of the root flaw status of the weld.

  5. Effect of Friction Stir Welding Parameters on the Mechanical and Microstructure Properties of the Al-Cu Butt Joint

    Directory of Open Access Journals (Sweden)

    Sare Celik

    2016-05-01

    Full Text Available Friction Stir Welding (FSW is a solid-state welding process used for welding similar and dissimilar materials. FSW is especially suitable to join sheet Al alloys, and this technique allows different material couples to be welded continuously. In this study, 1050 Al alloys and commercially pure Cu were produced at three different tool rotation speeds (630, 1330, 2440 rpm and three different tool traverse speeds (20, 30, 50 mm/min with four different tool position (0, 1, 1.5, 2 mm by friction stir welding. The influence of the welding parameters on the microstructure and mechanical properties of the joints was investigated. Tensile and bending tests and microhardness measurements were used to determine the mechanical properties. The microstructures of the weld zone were investigated by optical microscope and scanning electron microscope (SEM and were analyzed in an energy dispersed spectrometer (EDS. Intermetallic phases were detected based on the X-ray diffraction (XRD analysis results that evaluated the formation of phases in the weld zone. When the welding performance of the friction stir welded butt joints was evaluated, the maximum value obtained was 89.55% with a 1330 rpm tool rotational speed, 20 mm/min traverse speed and a 1 mm tool position configuration. The higher tensile strength is attributed to the dispersion strengthening of the fine Cu particles distributed over the Al material in the stir zone region.

  6. Texture Analyses of Ti/Al2O3 Nanocomposite Produced Using Friction Stir Processing

    Science.gov (United States)

    Shafiei-Zarghani, Aziz; Kashani-Bozorg, Seyed Farshid; Gerlich, Adrian P.

    2016-11-01

    The texture evolution of Ti/Al2O3 nanocomposite fabricated using friction stir processing (FSP) was investigated at both macroscopic and microscopic levels employing X-ray diffraction and electron backscattering diffraction techniques. The developed textures were compared with ideal shear textures of hexagonal close-packed (hcp) structure, revealing that the fabricated nanocomposite is dominated by the P 1 hcp (fiber { 10bar{1}1} continuous dynamic recrystallization as well as increasing the fraction of high-angle grain boundaries within the developed microstructure.

  7. Assessment Of Joints Using Friction Stir Welding And Refill Friction Stir Spot Welding Methods

    Directory of Open Access Journals (Sweden)

    Lacki P.

    2015-09-01

    Full Text Available FSW (Friction Stir Welding and RFSSW (Refill Friction Stir Spot Welding joints have been increasingly used in industrial practice. They successfully replace fusion-welded, riveted or resistance-welded joints. In the last two decades, dynamic development of this method has stimulated investigations of the fast methods for joint diagnostics. These methods should be non-destructive and easy to be used in technological processes. The methods of assessment of joint quality are expected to detect discontinuities in the structures welded using FSW and FSSW methods. Reliable detection of flaws would substantially extend the range of applications of FSW joints across many sectors of industry, including aviation. The investigations carried out in this paper allowed for characterization of defects present in FSW and RFSSW joints. Causes of these defects were also stressed. An overview of the methodologies for assessment of joint quality was presented. Results of assessment of the quality of joints made of 2024T6 aluminium sheet metal using FSW and RFSSW method were presented.

  8. Analysis and Comparison of Friction Stir Welding and Laser Assisted Friction Stir Welding of Aluminum Alloy

    Directory of Open Access Journals (Sweden)

    Sabina Luisa Campanelli

    2013-12-01

    Full Text Available Friction Stir Welding (FSW is a solid-state joining process; i.e., no melting occurs. The welding process is promoted by the rotation and translation of an axis-symmetric non-consumable tool along the weld centerline. Thus, the FSW process is performed at much lower temperatures than conventional fusion welding, nevertheless it has some disadvantages. Laser Assisted Friction Stir Welding (LAFSW is a combination in which the FSW is the dominant welding process and the laser pre-heats the weld. In this work FSW and LAFSW tests were conducted on 6 mm thick 5754H111 aluminum alloy plates in butt joint configuration. LAFSW is studied firstly to demonstrate the weldability of aluminum alloy using that technique. Secondly, process parameters, such as laser power and temperature gradient are investigated in order to evaluate changes in microstructure, micro-hardness, residual stress, and tensile properties. Once the possibility to achieve sound weld using LAFSW is demonstrated, it will be possible to explore the benefits for tool wear, higher welding speeds, and lower clamping force.

  9. Thermal Stir Welding Development at Marshall Space Flight Center

    Science.gov (United States)

    Ding, Robert J.

    2008-01-01

    Solid state welding processes have become the focus of welding process development at NASA's Marshall Space Flight Center. Unlike fusion weld processes such as tungsten inert gas (TIG), variable polarity plasma arc (VPPA), electron beam (EB), etc., solid state welding processes do not melt the material during welding. The resultant microstructure can be characterized as a dynamically recrystallized morphology much different than the casted, dentritic structure typical of fusion weld processes. The primary benefits of solid state processes over fusion weld processes include superior mechanic properties and the elimination of thermal distortion and residual stresses. These solid state processes attributes have profoundly influenced the direction of advanced welding research and development within the NASA agency. Thermal Stir Welding (TSW) is a new solid state welding process being developed at the Marshall Space Flight Center. Unlike friction stir welding, the heating, stirring and forging elements of the weld process can be decoupled for independent control. An induction coil induces energy into a workpiece to attain a desired plastic temperature. An independently controlled stir rod, captured within non-rotating containment plates, then stirs the plasticized material followed by forging plates/rollers that work the stirred weld joint. The independent control (decoupling) of heating, stirring and forging allows, theoretically, for the precision control of microstructure morphology. The TSW process is being used to evaluate the solid state joining of Haynes 230 for ARES J-2X applications. It is also being developed for 500-in (12.5 mm) thick commercially pure grade 2 titanium for navy applications. Other interests include Inconel 718 and stainless steel. This presentation will provide metallurgical and mechanical property data for these high melting temperature alloys.

  10. Friction Stir Processing of Particle Reinforced Composite Materials

    Directory of Open Access Journals (Sweden)

    Daniel Solomon

    2010-01-01

    Full Text Available The objective of this article is to provide a review of friction stir processing (FSP technology and its application for microstructure modification of particle reinforced composite materials. The main focus of FSP was on aluminum based alloys and composites. Recently, many researchers have investigated this technology for treating other alloys and materials including stainless steels, magnesium, titanium, and copper. It is shown that FSP technology is very effective in microstructure modification of reinforced metal matrix composite materials. FSP has also been used in the processing and structure modification of polymeric composite materials. Compared with other manufacturing processes, friction stir processing has the advantage of reducing distortion and defects in materials. The layout of this paper is as follows. The friction stir processing technology will be presented first. Then, the application of this technology in manufacturing and structure modification of particle reinforced composite materials will be introduced. Future application of friction stir processing in energy field, for example, for vanadium alloy and composites will be discussed. Finally, the challenges for improving friction stir processing technology will be mentioned.

  11. Mechanistic Models of Friction Stir Welding

    Science.gov (United States)

    Stewart, Michael B.

    1998-01-01

    Friction stir welding is a welding process developed at The Welding Institute (TWI) in England. The method uses very large strain plastic deformation of the material to join two pieces of metal together. The material is deformed using a tool which is forced between the two pieces which rotates causing a bond. Beyond this, very little is actually known although many people working in the field are willing to speculate on the detailed mechanisms involved. Some measurements made using sacrificial thermocouples at the weld joint indicate that the maximum temperature during the weld process is on the order of 370C - well below the melting temperature of the material. However, at this temperature, the material properties are highly temperature dependent, and the yield stress is approximately an order of magnitude less at this temperature than it is at room temperature. As expected, there are many interpretations of the physical mechanisms occurring during the weld process. Although there is very little published concerned with FSW, some of the anecdotal theories will be described. One describes the primary mechanism as frictional heating at the front of the tool caused by slip between the tool and the material. At elevated temperatures, the weld material becomes soft and deforms around the tool but not essentially altered by the tool rotation, similar to an extrusion. As the material meets again at the rear of the tool, the temperatures and pressures are sufficient to cause the material to bond. All other structures seen are secondary and unimportant. Another theory examined last summer at NASA's Marshall Space Flight Center (MSFC) was that there was no slip between the tool and the material resulting in a rotating mass of plastic weld material traveling at a variety of angular velocities - the greatest at the tool surface diminishing to zero at the outer edge of the plastic mass surrounding the tool. This conceptual model was followed by simplified calculations which

  12. Nanoscale magnetic stirring bars for heterogeneous catalysis in microscopic systems.

    Science.gov (United States)

    Yang, Shuliang; Cao, Changyan; Sun, Yongbin; Huang, Peipei; Wei, Fangfang; Song, Weiguo

    2015-02-23

    Nanometer-sized magnetic stirring bars containing Pd nanoparticles (denoted as Fe3 O4 -NC-PZS-Pd) for heterogeneous catalysis in microscopic system were prepared through a facile two-step process. In the hydrogenation of styrene, Fe3 O4 -NC-PZS-Pd showed an activity similar to that of the commercial Pd/C catalyst, but much better stability. In microscopic catalytic systems, Fe3 O4 -NC-PZS-Pd can effectively stir the reaction solution within microdrops to accelerate mass transfer, and displays far better catalytic activity than the commercial Pd/C for the hydrogenation of methylene blue in an array of microdroplets. These results suggested that the Fe3 O4 -NC-PZS-Pd could be used as nanoscale stirring bars in nanoreactors.

  13. Weld Nugget Temperature Control in Thermal Stir Welding

    Science.gov (United States)

    Ding, R. Jeffrey (Inventor)

    2014-01-01

    A control system for a thermal stir welding system is provided. The control system includes a sensor and a controller. The sensor is coupled to the welding system's containment plate assembly and generates signals indicative of temperature of a region adjacent and parallel to the welding system's stir rod. The controller is coupled to the sensor and generates at least one control signal using the sensor signals indicative of temperature. The controller is also coupled to the welding system such that at least one of rotational speed of the stir rod, heat supplied by the welding system's induction heater, and feed speed of the welding system's weld material feeder are controlled based on the control signal(s).

  14. A Brief Introduction to the Theory of Friction Stir Welding

    Science.gov (United States)

    Nunes, Arthur C., Jr.

    2008-01-01

    Friction stir welding (FSW) is a solid state welding process invented in 1991 at The Welding Institute in the United Kingdom. A weld is made in the FSW process by translating a rotating pin along a weld seam so as to stir the sides of the seam together. FSW avoids deleterious effects inherent in melting and is already an important welding process for the aerospace industry, where welds of optimal quality are demanded. The structure of welds determines weld properties. The structure of friction stir welds is determined by the flow field in the weld metal in the vicinity of the weld tool. A simple kinematic model of the FSW flow field developed at Marshall Space Flight Center, which enables the basic features of FSW microstructure to be understood and related to weld process parameters and tool design, is explained.

  15. Wet gringing of zeolite in stirred media mill

    Science.gov (United States)

    Mucsi, G.; Bohács, K.

    2016-04-01

    In the present study the results of systematic experimental series are presented with the specific goal of optimizing the zeolite nanoparticles' production using a wet stirred media mill. The diameter of the grinding media as well as the rotor velocity were varied in the experiments. Particle size distribution and "outer" specific surface area of the ground samples were measured by a laser particle size analyser. Additionally, BET, XRD and FT-IR analyses were performed for the characterization of the "total" specific surface area as well as the crystalline and material structure, respectively. Based on the results of the laboratory experiments it was found that wet stirred media milling provided significant reductions in the particle size of zeolite. Furthermore, the crystallinity of the samples also decreased, so not only the physical but the mineralogical characteristics of zeolite can be controlled by stirred media milling.

  16. MICROSTRUCTURAL STUDIES OF FRICTION STIR WELDED AZ31 MAGNESIUM ALLOY

    Institute of Scientific and Technical Information of China (English)

    H.Zhang; S.B.Lin; L.Wu; J.C.Feng

    2004-01-01

    Friction stir welding achieves the weld in solid phase by locally introducing frictional heating and plastic flow arising from rotation of the welding tool, which results in changes in the local microstructure of magnesium alloy. The purpose in the paper is to study the microstructures of friction stir welded AZ3I magnesium alloy. Residual microstructures,including dynamic re-crystallization zone and nugget structures have been systematically investigated utilizing optical microscopy (OM), scanning electric microscopy (SEM),transmission electron microscopy (TEM) with energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and micro-hardness. AZ31 magnesium alloy has been successfully friction stir welded and exhibits the variations of microstructure including dynamically recrystallized,equaxied grains in the weld nugget. Residual hardness in the nugget was found slightly lower than the parent but not too obvious.

  17. Microstructure Evolution during Friction Stir Spot Welding of TRIP Steel

    DEFF Research Database (Denmark)

    Lomholt, Trine Colding; Pantleon, Karen; Somers, Marcel A. J.

    2010-01-01

    In this study, the feasibility of friction stir spot welding of TRIP steel is investigated. In addition to manufacturing successful welds, the present study aims at a fundamental understanding of the mechanisms occurring at the (sub)micron scale during friction stir spot welding. As one of the main...... parameters to control friction stir welding, the influence of the rotational speed of the tool was investigated. Three different rotational speeds (500 rpm, 1000 rpm and 1500 rpm, respectively) were applied. The microstructure of the welded samples was investigated with reflected light microscopy, scanning...... electron microscopy, and electron backscatter diffraction. Microhardness measurements and lap-shear tensile tests completed the investigations of the welded samples and allow evaluation of the quality of the welds....

  18. The effect of mechanical stirring on buoyancy-driven circulations

    OpenAIRE

    Tailleux, Remi; Rouleau, Lucie

    2009-01-01

    The theoretical analysis of the energetics of mechanically-stirred horizontal convection for a Boussinesq fluid yields the formula: G(APE) = \\gamma_{mixing} G(KE) + (1+\\gamma_{mixing}) W_{r,laminar} where G(APE) and G(KE) are the work rate done by the buoyancy and mechanical forcing respectively, \\gamma_{mixing} is the mixing efficiency, and W_{r,laminar} is the background rate of increase in gravitational potential energy due to molecular diffusion. The formula shows that mechanical stirring...

  19. Seam-Tracking for Friction Stir Welded Lap Joints

    Science.gov (United States)

    Fleming, Paul A.; Hendricks, Christopher E.; Cook, George E.; Wilkes, D. M.; Strauss, Alvin M.; Lammlein, David H.

    2010-11-01

    This article presents a method for automatic seam-tracking in friction stir welding (FSW) of lap joints. In this method, tracking is accomplished by weaving the FSW tool back-and-forth perpendicular to the direction of travel during welding and monitoring force and torque signals. Research demonstrates the ability of this method to automatically track weld seam positions. Additionally, tensile and S-bend test result comparisons demonstrate that weaving most likely does not reduce weld quality. Finally, benefits of this weave-based method to FSW of lap joints are discussed and methods for incorporating it into existing friction stir welding control algorithms (such as axial load control) are examined.

  20. Numerical optimisation of friction stir welding: review of future challenges

    DEFF Research Database (Denmark)

    Tutum, Cem Celal; Hattel, Jesper Henri

    2011-01-01

    During the last decade, the combination of increasingly more advanced numerical simulation software with high computational power has resulted in models for friction stir welding (FSW), which have improved the understanding of the determining physical phenomena behind the process substantially....... This has made optimisation of certain process parameters possible and has in turn led to better performing friction stir welded products, thus contributing to a general increase in the popularity of the process and its applications. However, most of these optimisation studies do not go well beyond manual...

  1. Friction stir weld tools having fine grain structure

    Energy Technology Data Exchange (ETDEWEB)

    Grant, Glenn J.; Frye, John G.; Kim, Jin Yong; Lavender, Curt A.; Weil, Kenneth Scott

    2016-03-15

    Tools for friction stir welding can be made with fewer process steps, lower cost techniques, and/or lower cost ingredients than other state-of-the-art processes by utilizing improved compositions and processes of fabrication. Furthermore, the tools resulting from the improved compositions and processes of fabrication can exhibit better distribution and homogeneity of chemical constituents, greater strength, and/or increased durability. In one example, a friction stir weld tool includes tungsten and rhenium and is characterized by carbide and oxide dispersoids, by carbide particulates, and by grains that comprise a solid solution of the tungsten and rhenium. The grains do not exceed 10 micrometers in diameter.

  2. Process optimization of friction stir welding based on thermal models

    DEFF Research Database (Denmark)

    Larsen, Anders Astrup

    2010-01-01

    This thesis investigates how to apply optimization methods to numerical models of a friction stir welding process. The work is intended as a proof-of-concept using different methods that are applicable to models of high complexity, possibly with high computational cost, and without the possibility...... information of the high-fidelity model. The optimization schemes are applied to stationary thermal models of differing complexity of the friction stir welding process. The optimization problems considered are based on optimizing the temperature field in the workpiece by finding optimal translational speed...

  3. Interfacial and Mechanical Behavior of AA5456 Filling Friction-Stir-Welded Lap Joints Using Similar and Dissimilar Pins

    Science.gov (United States)

    Behmand, Saleh Alaei; Mirsalehi, Seyyed Ehsan; Omidvar, Hamid; Safarkhanian, Mohammad Ali

    2016-06-01

    In this article, filling friction stir welding (FFSW) of the remaining exit holes of AA5456 alloy friction-stir-welded lap joints was studied. For this purpose, the influences of different rotating speeds, holding times, and pin materials, AA5456 and AA2024, on the metallurgical structure and joint strength were investigated. The observations showed that defect-free lap joints are successfully obtainable by this method using similar and dissimilar consumable pins. The results indicated that the higher rotating speed and holding time adversely affect the weld performance. The best result was achieved for 30 seconds holding time, 500 rpm rotating speed, and AA2024 consumable pin. In this condition, a lap shear strength of 10 pct higher than that of the nonfilled joint, equivalent to about 94 pct of the original defect-free FSW joint, was obtained, whereas the GTAW filled joint showed only approximately 87 pct of the continuous FSW joint strength.

  4. Interfacial and Mechanical Behavior of AA5456 Filling Friction-Stir-Welded Lap Joints Using Similar and Dissimilar Pins

    Science.gov (United States)

    Behmand, Saleh Alaei; Mirsalehi, Seyyed Ehsan; Omidvar, Hamid; Safarkhanian, Mohammad Ali

    2016-10-01

    In this article, filling friction stir welding (FFSW) of the remaining exit holes of AA5456 alloy friction-stir-welded lap joints was studied. For this purpose, the influences of different rotating speeds, holding times, and pin materials, AA5456 and AA2024, on the metallurgical structure and joint strength were investigated. The observations showed that defect-free lap joints are successfully obtainable by this method using similar and dissimilar consumable pins. The results indicated that the higher rotating speed and holding time adversely affect the weld performance. The best result was achieved for 30 seconds holding time, 500 rpm rotating speed, and AA2024 consumable pin. In this condition, a lap shear strength of 10 pct higher than that of the nonfilled joint, equivalent to about 94 pct of the original defect-free FSW joint, was obtained, whereas the GTAW filled joint showed only approximately 87 pct of the continuous FSW joint strength.

  5. Numeric simulations of a liquid metal model of a bloom caster under the effect of rotary electromagnetic stirring

    Science.gov (United States)

    Barna, M.; Javurek, M.; Willers, B.; Eckert, S.; Reiter, J.

    2016-07-01

    At the voestalpine Stahl Donawitz GmbH the continuous casting of round steel blooms is commonly supported by electromagnetically induced stirring of the liquid steel flow. A number of beneficial effects are attributed to electromagnetic stirring in the mould region (M-EMS), e.g. the enhanced transition from columnar to equiaxed solidification, the homogenization of the liquid steel flow or the reduction of surface and subsurface defects. Although the positive effects of M-EMS can be seen on the blooms (e.g. in etchings), the link between electromagnetic stirring of the steel melt and the quality of the solidified bloom is not sufficiently understood. Theoretical considerations are often limited to general cases and their results are therefore not directly applicable to real continuous casting geometries. On the other hand, plant measurements can only be performed to a limited extent due to the harsh conditions and other restrictions (e.g. safety regulations). In this work an alternative approach is used to investigate the steel flow in a round bloom caster under the influence of M-EMS. In a 1:3 scale Perspex model of a round bloom strand, measurements of the flow under the influence of a rotating magnetic field can be conducted. These measurements provide a validation benchmark for the numeric simulations. A numeric model of the before mentioned 1:3 scale model is implemented, encompassing the strand, the submerged entry nozzle as well as the M-EMS device. In the modelling approach, the bidirectional coupling between liquid steel flow and the electromagnetic field/forces has to be considered because otherwise the resulting tangential velocities will be overestimated. With the validated modelling approach, simulations of real casting machines can then be conducted, stirring parameter influences can be shown and conclusions for the real casting process can be drawn.

  6. Temporarily alloying titanium to facilitate friction stir welding

    Energy Technology Data Exchange (ETDEWEB)

    Hovanski, Yuri [Washington State Univ., Pullman, WA (United States)

    2009-05-01

    While historically hydrogen has been considered an impurity in titanium, when used as a temporary alloying agent it promotes beneficial changes to material properties that increase the hot-workability of the metal. This technique known as thermohydrogen processing was used to temporarily alloy hydrogen with commercially pure titanium sheet as a means of facilitating the friction stir welding process. Specific alloying parameters were developed to increase the overall hydrogen content of the titanium sheet ranging from commercially pure to 30 atomic percent. Each sheet was evaluated to determine the effect of the hydrogen content on process loads and tool deformation during the plunge phase of the friction stir welding process. Two materials, H-13 tool steel and pure tungsten, were used to fabricate friction stir welding tools that were plunged into each of the thermohydrogen processed titanium sheets. Tool wear was characterized and variations in machine loads were quantified for each tool material and weld metal combination. Thermohydrogen processing was shown to beneficially lower plunge forces and stabilize machine torques at specific hydrogen concentrations. The resulting effects of hydrogen addition to titanium metal undergoing the friction stir welding process are compared with modifications in titanium properties documented in modern literature. Such comparative analysis is used to explain the variance in resulting process loads as a function of the initial hydrogen concentration of the titanium.

  7. The Care Tradition: Beyond "Add Women and Stir."

    Science.gov (United States)

    Noddings, Nel

    2001-01-01

    Examines problems of curricular inclusion, emphasizing ways of including the interests and contributions of women in social studies curricula. After describing the inadequacy of the "add women and stir" approach to inclusion, the paper discusses the tradition of care long identified with female life, then explores ways to preserve and extend this…

  8. Stirring and mixing of liquids using acoustic radiation force.

    Science.gov (United States)

    Sarvazyan, Armen; Ostrovsky, Lev

    2009-06-01

    The possibility of using acoustic radiation force in standing waves for stirring and mixing small volumes of liquids is theoretically analyzed. The principle of stirring considered in this paper is based on moving the microparticles suspended in a standing acoustic wave by changing the frequency so that one standing wave mode is replaced by the other, with differently positioned minima of potential energy. The period-average transient dynamics of solid microparticles and gas microbubbles is considered, and simple analytical solutions are obtained for the case of standing waves of variable amplitude. It is shown that bubbles can be moved from one equilibrium position to another two to three orders of magnitude faster than solid particles. For example, radiation force in a standing acoustic wave field may induce movement of microbubbles with a speed of the order of a few m/s at a frequency of 1 MHz and ultrasound pressure amplitude of 100 kPa, whereas the speed of rigid particles does not exceed 1 cms under the same conditions. The stirring effect can be additionally enhanced due to the fact that the bubbles that are larger and smaller than the resonant bubbles move in opposite directions. Possible applications of the analyzed stirring mechanism, such as in microarrays, are discussed. PMID:19507936

  9. Numerical Simulation of Laminar Flow Field in a Stirred Tank

    Institute of Scientific and Technical Information of China (English)

    范茏; 王卫京; 杨超; 毛在砂

    2004-01-01

    Stirred tanks are used extensively in process industry and one of the most commonly used impellers in stirred tanks is the R.ushton disk turbine. Surprisingly few data are available regarding flow and mixing in stirred-tank reactors with Rushton turbine in the laminar regime, in particular the laminar flow in baffled tanks.In this paper, the laminar flow field in a baffled tank stirred by a standard R.ushton turbine is simulated with the improved inner-outer iterative method. The non-inertial coordinate system is used for the impeller region, which is in turn used as the boundary conditions for iteration. It is found that the simulation results are in good agreement with previous experiments. In addition, the flow number and impeller power number calculated from the simulated flow field are in satisfactory agreement with experimental data. This numerical method allows prediction of flow structure requiring no experimental data as the boundary conditions and has the potential of being used to scale-up and design of related process equipment.

  10. Imaging myocardial carcinoid with T2-STIR CMR

    OpenAIRE

    Baker Christopher; Schiavone William A; Prasad Sanjay K

    2008-01-01

    Abstract We used T2-STIR (Short Tau Inversion Recovery) cardiovascular magnetic resonance to demonstrate carcinoid tumor metastases to the heart and liver in a 64-year-old woman with a biopsy-proven ileal carcinoid tumor who was referred because of an abnormal echocardiogram.

  11. Stop Tobacco in Restaurants: Fifth Grade Students STIR City Hall

    Science.gov (United States)

    Morris, Ronald Vaughan

    2008-01-01

    This article discusses a campaign called STIR: Stop Tobacco in Restaurants, that was started by fourth and fifth grade students. The goal was to end smoking in public places, including restaurants, bowling alleys, sports bars, and pool halls. For two years they motivated their peers, coordinated an information campaign to urge kids and adults to…

  12. Auto-Adjustable Tool for Self-Reacting and Conventional Friction Stir Welding

    Science.gov (United States)

    Carter, Robert W. (Inventor)

    2002-01-01

    A friction stir welding dcvice that is configured to perform convention friction stir welding as well as self-reacting friction stir welding is described. A pin passes hrough an upper shoulder and can selectively attach 10 and detach from a lower shoulder in a preferred embodiment. A controller maintains thc discrete position of, and/or force applied by, the upper and lower shoulders during self-reacting friction stir welding, or maintains the pin at a desired depth and/or applied force during conventional friction stir welding.

  13. StirMark Benchmark: audio watermarking attacks based on lossy compression

    Science.gov (United States)

    Steinebach, Martin; Lang, Andreas; Dittmann, Jana

    2002-04-01

    StirMark Benchmark is a well-known evaluation tool for watermarking robustness. Additional attacks are added to it continuously. To enable application based evaluation, in our paper we address attacks against audio watermarks based on lossy audio compression algorithms to be included in the test environment. We discuss the effect of different lossy compression algorithms like MPEG-2 audio Layer 3, Ogg or VQF on a selection of audio test data. Our focus is on changes regarding the basic characteristics of the audio data like spectrum or average power and on removal of embedded watermarks. Furthermore we compare results of different watermarking algorithms and show that lossy compression is still a challenge for most of them. There are two strategies for adding evaluation of robustness against lossy compression to StirMark Benchmark: (a) use of existing free compression algorithms (b) implementation of a generic lossy compression simulation. We discuss how such a model can be implemented based on the results of our tests. This method is less complex, as no real psycho acoustic model has to be applied. Our model can be used for audio watermarking evaluation of numerous application fields. As an example, we describe its importance for e-commerce applications with watermarking security.

  14. Vitrification of simulated radioactive Rocky Flats plutonium containing waste ash with a stir-melter system

    International Nuclear Information System (INIS)

    A demonstration trial has been completed in which a simulated Rocky Flats ash consisting of an industrial fly-ash material doped with cerium oxide was vitrified in an alloy tank Stir-Melter trademark System. The cerium oxide served as a substitute for plutonium oxide present in the actual Rocky Flats waste stream. The glass developed falls within the SiO2 +Al2O3 / ΣAlkali / B2O3 System. The glass batch contained approximately 40 wt % of ash, the ash was modified to contain ∼5 wt % CeO2 to simulate plutonium chemistry in the glass. The ash simulant was mixed with water and fed to the Stir-Melter as a slurry with a 60 wt % water to 40 wt % solids ratio. Glass melting temperature was maintained at approximately 1050 degrees C during the melting trials. Melting rates as functions of impeller speed and slurry feed rate were determined. An optimal melting rate was established through a series of evolutionary variations of the control variables' settings. The optimal melting rate condition was used for a continuous six hour steady state run of the vitrification system. Glass mass flow rates out of the melter were measured and correlated with the slurry feed mass flow. Melter off-gas was sampled for particulate and volatile species over a period of four hours during the steady state run. Glass composition and durability studies were run on samples collected during the steady state run

  15. Continuous Cultivation of Photosynthetic Bacteria for Fatty Acids Production

    DEFF Research Database (Denmark)

    Kim, Dong-Hoon; Lee, Ji-Hye; Hwang, Yuhoon;

    2013-01-01

    In the present work, we introduced a novel approach for microbial fatty acids (FA) production. Photosynthetic bacteria, Rhodobacter sphaeroides KD131, were cultivated in a continuous-flow, stirred-tank reactor (CFSTR) at various substrate (lactate) concentrations.At hydraulic retention time (HRT)...

  16. MRI of lymphedema using short-TI-IR (STIR)

    Energy Technology Data Exchange (ETDEWEB)

    Fujii, Koichi; Ishida, Osamu; Mabuchi, Norihisa; Shindou, Hiroshi; Yoshioka, Hiroyasu; Kumano, Machiko; Hamada, Tatsumi; Ohkuma, Moriya (Kinki Univ., Osaka (Japan). School of Medicine)

    1990-01-01

    Thirty four cases with lymphedema of the extremities were examined with MRI at 0.5 tesla. On T1-weighted image, the enlarged subcutaneous tissue and the subcutaneous trabecular structures were seen in all cases. Moreover, the trabecular structures in the enlarged subcutaneous tissue showed low signal intensity on T1-weighted image and high signal intensity on T2-weighted image in all cases. Additionally, in 12 of 15 cases examined by Short-TI-IR (STIR) image, the trabecular structures and fluid collections in the subcutaneous tissue were shown more definitely in high signal intensity than by T2-weighted image. We consider MRI using STIR is to be useful in the evaluation of edematous disease. (author).

  17. Effects of electromagnetic stirring on microstructures of solidified aluminum alloys

    Institute of Scientific and Technical Information of China (English)

    时海芳; 张伟强

    2003-01-01

    Al-20%Cu, Al-33%Cu and Al-7%Si alloys were solidified with electromagnetic stirring(EMS). The fluid flow induced by electromagnetic stirring leads to the increases of the lamellar spacing of Al-CuAl2 and Al-Si eutectics and the secondary dendritic arm spacing. Rod-like eutectic structure plus pro-eutectic α(Al) are observed in Al-Cu eutectic alloy when the agitating voltage is increased over 130 V, and in the hypoeutectic alloys, globular grains of proeutectic α(Al) grains may form when the magnetic field is strong enough. The Si flakes in the Al-Si eutectic are also coarsened by applying forced flow during solidification, which is always related to the depression of their branching in the growth by the forced convection.

  18. CFD simulation of particle suspension in a stirred tank

    Institute of Scientific and Technical Information of China (English)

    Nana Qi; Hu Zhang; Kai Zhang; Gang Xu; Yongping Yang

    2013-01-01

    Particle suspension characteristics are predicted computationally in a stirred tank driven by a Smith turbine.In order to verify the hydrodynamic model and numerical method,the predicted power number and flow pattern are compared with designed values and simulated results from the literature,respectively.The effects of particle density,particle diameter,liquid viscosity and initial solid loading on particle suspension behavior are investigated by using the Eulerian-Eulerian two-fluid model and the standard k-ε turbulence model.The results indicate that solid concentration distribution depends on the flow field in the stirred tank.Higher particle density or larger particle size results in less homogenous distribution of solid particles in the tank.Increasing initial solid loading has an adverse impact on the homogeneous suspension of solid particles in a low-viscosity liquid,whilst more uniform particle distribution is found in a high-viscositv liauid.

  19. Friction stir welding of AZ31 magnesium alloy

    Institute of Scientific and Technical Information of China (English)

    林三宝; 张华; 吴林; 冯吉才; 戴鸿滨

    2003-01-01

    Friction stir welding (FSW) is an new solid-phase joining technology which has more advantages over fusion welding methods in welding of aluminum and other non-ferrous metals. The effects of welding parameters on mechanical properties and microstructure during friction stir welding of AZ31 magnesium alloy were studied in this paper. Microstructures and mechanical properties of the joints were investigated by means of optical microscopy, scanning electric microscopy (SEM), micro-hardness analysis, and tensile test. Experimental results show that the magnesium alloy can be successfully welded by FSW method, and the ultimate tensile strength (UTS) of FSW joint reaches up to 90 percent of base metal. The microstructures of welded joints exhibit the variation from dynamically recrystallized fine grains to greatly deformed grains. Hardness in nugget zone was found lower than the base metal but not too obvious.

  20. Structural response of superaustenitic stainless steel to friction stir welding

    International Nuclear Information System (INIS)

    Highlights: → Grain structure evolution was mainly governed by discontinuous recrystallization. → The recrystallization was static in nature and occurred during weld cooling cycle. → Material flow was mainly induced by the tool shoulder. → The texture was a superposition of {1 1 1} and {h k l} partial simple-shear fibers. - Abstract: Electron backscattering diffraction was employed to study grain structure development and texture evolution during friction stir welding (FSW) of a low stacking fault energy material, S31254 superaustenitic stainless steel. Formation of the final stir zone (SZ) microstructure was deduced to be primarily governed by discontinuous recrystallization occurring during the FSW cooling cycle. The textural pattern formed in the SZ was interpreted in the terms of {1 1 1} and {h k l} partial simple shear fiber textures.

  1. FRICTION STIR LAP WELDING OF ALUMINUM - POLYMER USING SCRIBE TECHNOLOGY

    Energy Technology Data Exchange (ETDEWEB)

    Upadhyay, Piyush; Hovanski, Yuri; Fifield, Leonard S.; Simmons, Kevin L.

    2015-02-16

    Friction Stir Scribe (FSS) technology is a relatively new variant of Friction Stir Welding (FSW) which enables lap joining of dissimilar material with very different melting points and different high temperature flow behaviors. The cutter scribe attached at the tip of FSW tool pin effectively cuts the high melting point material such that a mechanically interlocking feature is created between the dissimilar materials. The geometric shape of this interlocking feature determines the shear strength attained by the lap joint. This work presents first use of scribe technology in joining polymers to aluminum alloy. Details of the several runs of scribe welding performed in lap joining of ~3.175mm thick polymers including HDPE, filled and unfilled Nylon 66 to 2mm thick AA5182 are presented. The effect of scribe geometry and length on weld interlocking features is presented along with lap shear strength evaluations.

  2. Effect of friction stir welding parameters on defect formation

    Science.gov (United States)

    Tarasov, S. Yu.; Rubtsov, V. E.; Eliseev, A. A.; Kolubaev, E. A.; Filippov, A. V.; Ivanov, A. N.

    2015-10-01

    Friction stir welding is a perspective method for manufacturing automotive parts, aviation and space technology. One of the major problems is the formation of welding defects and weld around the welding zone. The formation of defect is the main reason failure of the joint. A possible way to obtain defect-free welded joints is the selection of the correct welding parameters. Experimental results describing the effect of friction stir welding process parameters on the defects of welded joints on aluminum alloy AMg5M have been shown. The weld joint defects have been characterized using the non-destructive radioscopic and ultrasound phase array methods. It was shown how the type and size of defects determine the welded joint strength.

  3. Feasibility of underwater friction stir welding of HY-80 steel

    OpenAIRE

    Stewart, William Chad

    2011-01-01

    Approved for public release; distribution is unlimited. The purpose of this thesis is to determine the feasibility of underwater friction stir welding (FSW) of high-strength; quench and temper low carbon steels that are susceptible to hydrogen-assisted cracking (HAC). The specific benefits of underwater FSW would be weld repairs of ship and submarine control surfaces and hulls without the need for drydocking and extensive environmental control procedures. A single tool of polycrystallin...

  4. Feasibility of underwater friction stir welding of hardenable alloy steel

    OpenAIRE

    Overfield, Norman E.

    2010-01-01

    Approved for public release; distribution is unlimited The objective of this thesis is to determine whether friction stir welding (FSW) is a feasible welding process for steels in an underwater environment. Specific benefits would be underwater weld repairs on steel alloy piping systems and/or structures, and crack repairs on control surfaces of submarines without the need for strict environment controls or in the submarine's case, for drydocking. A single tool made of polycrystaline cub...

  5. Knowledge based process development of bobbin tool friction stir welding

    OpenAIRE

    Hilgert, Jakob

    2012-01-01

    Over the last twenty years Friction Stir Welding (FSW) has proven to be a very promising new joining technique. Especially high strength aluminium alloys can be welded with large advantages as compared to conventional fusion welding processes. For some joint configurations and desired applications bobbin tool welding is a process variant that can circumvent limitations arising from the high process forces in conventional tool FSW. As bobbin tools are highly mechanically loaded, in-depth under...

  6. CFD SIMULATION OF A STIRRED DISHED BOTTOM VESSEL

    OpenAIRE

    Petr Vlček; Jan Skočilas; Tomáš Jirout

    2013-01-01

    This paper deals with simulation of the fluid flow in a stirred curved-bottom vessel equipped with three curved blade impellers. The power number and the impeller flow rate number are dimensionless characteristics of the system determined from simulation results and compared with relevant experimental data or data from the literature. The model of the system was created in the conventional Gambit and Fluent program. The system is solved for two designs — for an unbaffled vessel, and for a baf...

  7. CFD simulation of solids suspension in stirred tanks: Review

    OpenAIRE

    Ochieng Aoyi; Onyango Mrice S.

    2010-01-01

    Many chemical reactions are carried out using stirred tanks, and the efficiency of such systems depends on the quality of mixing, which has been a subject of research for many years. For solid-liquid mixing, traditionally the research efforts were geared towards determining mixing features such as off-bottom solid suspension using experimental techniques. In a few studies that focused on the determination of solids concentration distribution, some methods that have been used have not be...

  8. Friction stir welding (FSW) of aluminium foam sandwich panels

    OpenAIRE

    M. Bušić; Kožuh, Z.; D. Klobčar; Samardžić, I.

    2016-01-01

    The article focuses on the influence of welding speed and tool tilt angle upon the mechanical properties at the friction stir welding of aluminium foam sandwich panels. Double side welding was used for producing butt welds of aluminium sandwich panels applying insertion of extruded aluminium profile. Such insertion provided lower pressure of the tool upon the aluminium panels, providing also sufficient volume of the material required for the weldment formation. Ultimate tensile strength and f...

  9. Recrystallization Phenomena During Friction Stir Processing of Hypereutectic Aluminum-Silicon Alloy

    Science.gov (United States)

    Rao, A. G.; Ravi, K. R.; Ramakrishnarao, B.; Deshmukh, V. P.; Sharma, A.; Prabhu, N.; Kashyap, B. P.

    2013-03-01

    Microstructural evolution and related dynamic recrystallization phenomena were investigated in overlapping multipass friction stir processing (FSP) of hypereutectic Al-30 pct Si alloy. FSP resulted in the elimination of porosities along with the refinement of primary silicon particles and alpha aluminum grains. These alpha aluminum grains predominantly exhibit high angle boundaries with various degrees of recovered substructure and dislocation densities. The substructure and grain formation during FSP take place primarily by annihilation and reorganization of dislocations in the grain interior and at low angle grain boundary. During multipass overlap FSP, small second phase particles were observed to form, which are accountable for pinning the grain boundaries and thus restricting their growth. During the multipass overlap FSP, the microstructure undergoes continuous dynamic recrystallization by formation of the subgrain boundary and subgrain growth to the grain structure comprising of mostly high angle grain boundaries.

  10. Macro-instability: a chaotic flow component in stirred tanks.

    Science.gov (United States)

    Hasal, Pavel; Jahoda, Milan; Fort, Ivan

    2008-02-13

    Chaotic features of the macro-instability (MI) of flow patterns in stirred tanks are studied in this paper. Datasets obtained by measuring the axial component of the fluid velocity and the tangential force affecting the baffles are used. Two geometrically identical, flat-bottomed cylindrical mixing tanks (diameter of 0.3m) stirred with either pitched blade turbine impellers or Rushton turbine impeller are used in the experiments, and water and aqueous glycerol solutions are used as the working liquids. First, the presence of the MI component in the data is examined by spectral analysis. Then, the MI components are identified in the data using the proper orthogonal decomposition (POD) technique. The attractors of the macro-instability are reconstructed using either the POD eigenmodes or a method of delays and finally the attractor invariants are evaluated. The dependence of the correlation dimension and maximum Lyapunov exponent on the vessel operational conditions is determined together with their distribution within the tank. No significant spatial variability of the correlation dimension value is observed. Its value is strongly influenced by impeller speed and by the vessel-impeller geometry. More profound spatial distribution is displayed by the maximum Lyapunov exponent taking distinctly positive values. These two invariants, therefore, can be used to locate distinctive regions with qualitatively different MI dynamics within the stirred tank. PMID:17673415

  11. Thermo-Mechanical Processing in Friction Stir Welds

    Science.gov (United States)

    Schneider, Judy

    2003-01-01

    Friction stir welding is a solid-phase joining, or welding process that was invented in 1991 at The Welding Institute (TWI). The process is potentially capable of joining a wide variety of aluminum alloys that are traditionally difficult to fusion weld. The friction stir welding (FSW) process produces welds by moving a non-consumable rotating pin tool along a seam between work pieces that are firmly clamped to an anvil. At the start of the process, the rotating pin is plunged into the material to a pre-determined load. The required heat is produced by a combination of frictional and deformation heating. The shape of the tool shoulder and supporting anvil promotes a high hydrostatic pressure along the joint line as the tool shears and literally stirs the metal together. To produce a defect free weld, process variables (RPM, transverse speed, and downward force) and tool pin design must be chosen carefully. An accurate model of the material flow during the process is necessary to guide process variable selection. At MSFC a plastic slip line model of the process has been synthesized based on macroscopic images of the resulting weld material. Although this model appears to have captured the main features of the process, material specific interactions are not understood. The objective of the present research was to develop a basic understanding of the evolution of the microstructure to be able to relate it to the deformation process variables of strain, strain rate, and temperature.

  12. Friction stir welding characteristics of two aluminum alloys

    Institute of Scientific and Technical Information of China (English)

    刘会杰; 藤井英俊; 前田将克; 野城清

    2003-01-01

    The friction stir welding characteristics of the strain-hardened AA1050-H24 and precipitate-hardened AA2017-T351 aluminum alloys were examined in order to reveal the effects of the alloy properties on the friction stir welding behavior of the base materials. The results show that (1) for AA1050-H24, the weld possesses a smooth surface and clear ripples, there is no elliptical weld nugget in the weld, there is not discernible interface between the stir zone and the thermo-mechanically affected zone(TMAZ), and the internal defect of the weld looks like a long crack and is located in the lower part of the weld; (2) for AA2017-T351, the weld usually possesses a rough surface and visible ripples, the elliptical weld nugget clearly exists in the weld and there is obvious plastic flow and a discernible interface between the nugget and the TMAZ, and the internal defect of the weld is composed of many voids and distributed in the middle part of the weld; (3) the effective ranges of the welding parameters for AA1050-H24 and AA2017-T351 are both narrow, especially for the latter; and (4) the tensile strength efficiencies of the joints for the two typical alloys are similar, i e 79% for AA1050-H24 and 82% for AA2017-T351.

  13. Effects of Friction Stir Welding Speed on AA2195 alloy

    Directory of Open Access Journals (Sweden)

    Lee Ho-Sung

    2016-01-01

    Full Text Available The application of friction stir welding (FSW to aerospace has grown rapidly due to the high efficiency and environmental friendly nature of the process. FSW is achieved by plastic flow of frictionally heated material in solid state and offers many advantages of avoiding hot cracking and limiting component distortion. Recently low density, high modulus and high strength AA2195 are used as substitute for conventional aluminum alloys since the weight saving is critical in aerospace applications. One of the problems for this alloy is weld metal porosity formation leading to hot cracking. Combination of FSW and AA2195 provides synergy effect to improve mechanical properties and weight saving of aerospace structure such as cryogenic fuel tanks for launch systems. The objective of this paper is to investigate the effect of friction stir welding speed on mechanical and microstructural properties of AA2195. The friction stir welded materials were joined with four different tool rotation speeds (350~800 rpm and five welding speeds (120~360 mm/min, which are the two prime welding parameters in this process.

  14. Repair welding process of friction stir welding groove defect

    Institute of Scientific and Technical Information of China (English)

    LIU Hui-jie; ZHANG Hui-jie

    2009-01-01

    The groove defect formed in the friction stir welding dramatically deteriorates weld appearances and mechanical properties of the joints owing to its larger size and penetration. Therefore, the friction stir repair welding was utilized to remove such a groove defect, and the focus was placed on the mechanical properties and microstructural characteristics of the repair joints so as to obtain an optimum repair welding process. The experimental results indicate that the groove defect can be removed by friction stir repair welding, and the offset repair welding process is superior to the symmetrical repair welding process. In the symmetrical repair welding process, a large number of fine cavity defects and an obvious aggregation of hard-brittle phase Al2Cu occur, accordingly the mechanical properties of the repair joint are weakened, and the fracture feature of repair joint is partially brittle and partially plastic. A good-quality repair joint can be obtained by the offset repair welding process, and the repair joint is fractured near the interface between the weld nugget zone and thermal-mechanically affected zone.

  15. Friction Stir Welding of Al 5052 with Al 6061 Alloys

    Directory of Open Access Journals (Sweden)

    N. T. Kumbhar

    2012-01-01

    Full Text Available Friction stir welding (FSW, a solid-state joining technique, is being extensively used in similar as well as dissimilar joining of Al, Mg, Cu, Ti, and their alloys. In the present study, friction stir welding of two aluminium alloys—AA6061 and AA5052—was carried out at various combinations of tool rotation speeds and tool traverse speeds. The transverse cross-section of the weld was used for optical as well as electron microscopy observations. The microstructural studies were used to get an indication of the extent of material mixing both at the macro- and microscales. It was observed that, at the interface region, both materials exhibited similar texture despite the nonrigorous mixing of the materials in the nugget. The extent of interdiffusion of alloying elements at the interface was studied using electron probe microanalysis. The tensile testing evaluation of these specimens showed good mechanical properties. The interdiffusion of alloying elements and development of similar orientations in the nugget could have contributed to the better tensile properties of the friction-stir-welded AA5052-AA6061 specimens.

  16. Friction stir welding of 5052 aluminum alloy plates

    Institute of Scientific and Technical Information of China (English)

    Yong-Jai KWON; Seong-Beom SHIM; Dong-Hwan PARK

    2009-01-01

    Friction stir welding between 5052 aluminum alloy plates with a thickness of 2 mm was performed. The tool for welding was rotated at speeds ranging from 500 to 3 000 r/min under a constant traverse speed of 100 mm/min. The results show that at all tool rotation speeds, defect-free welds are successfully obtained. Especially at 1 000, 2 000 and 3 000 r/min, the welds exhibit very smooth surface morphologies. At 500, 1 000, and 2 000 r/min, onion ring structure is clearly observed in the friction-stir-welded zone (SZ). In addition, the onion ring structure region becomes wider as the tool rotation speed is increased. The gain size in the SZ is smaller than that in the base metal, and is decreased with a decrease of the tool rotation speed. In all tool rotation speeds, the SZ exhibits higher average hardness than the base metal. Especially at 500 r/min, the average hardness of the SZ reaches a level about 33% greater than that of the base metal. At 500, 1 000 and 2 000 r/min, the tensile strength of the friction stir welded (FSWed) plates is similar to that of the base metal (about 204 Mpa). The elongation of the FSWed plates is lower than that of the base metal (about 22%). However, it is noticeable that the maximum elongation of about 21% is obtained at 1 000 r/min.

  17. Microstructural Characterization of Friction Stir Welded Aluminum-Steel Joints

    Science.gov (United States)

    Patterson, Erin E.; Hovanski, Yuri; Field, David P.

    2016-06-01

    This work focuses on the microstructural characterization of aluminum to steel friction stir welded joints. Lap weld configuration coupled with scribe technology used for the weld tool have produced joints of adequate quality, despite the significant differences in hardness and melting temperatures of the alloys. Common to friction stir processes, especially those of dissimilar alloys, are microstructural gradients including grain size, crystallographic texture, and precipitation of intermetallic compounds. Because of the significant influence that intermetallic compound formation has on mechanical and ballistic behavior, the characterization of the specific intermetallic phases and the degree to which they are formed in the weld microstructure is critical to predicting weld performance. This study used electron backscatter diffraction, energy dispersive spectroscopy, scanning electron microscopy, and Vickers micro-hardness indentation to explore and characterize the microstructures of lap friction stir welds between an applique 6061-T6 aluminum armor plate alloy and a RHA homogeneous armor plate steel alloy. Macroscopic defects such as micro-cracks were observed in the cross-sectional samples, and binary intermetallic compound layers were found to exist at the aluminum-steel interfaces of the steel particles stirred into the aluminum weld matrix and across the interfaces of the weld joints. Energy dispersive spectroscopy chemical analysis identified the intermetallic layer as monoclinic Al3Fe. Dramatic decreases in grain size in the thermo-mechanically affected zones and weld zones that evidenced grain refinement through plastic deformation and recrystallization. Crystallographic grain orientation and texture were examined using electron backscatter diffraction. Striated regions in the orientations of the aluminum alloy were determined to be the result of the severe deformation induced by the complex weld tool geometry. Many of the textures observed in the weld

  18. Physical Simulation of New Desulphurization Technology Using Pulsed and Rotary Stirring-Injection

    Institute of Scientific and Technical Information of China (English)

    WU Wei; HU Yan-bin; LIU Liu; DING Yong-liang

    2008-01-01

    The contrast experiment of different stirring modes, which includes a new type of stirring-injection with the method of pulse and rotation, and the initial one-way stirring method, is done through physical simulation in the laboratory. The stirring methods of pulse and rotation are of two kinds. One is pulsed and rotary stirrer with positive and opposite directions. The other is pulsed and rotary stirrer with rotation-stop-rotation. The results show that the stirring mode of pulse and rotation has better effects than the one-way stirring method. The specific effects are that the mixing time of the melting bath is apparently shortened, the number of grains involved in the liquid surface is increased, and the residence time of air bubble in water is doubled.

  19. Numerical Bifurcation Analysis of Delayed Recycle Stream in a Continuously Stirred Tank Reactor

    Science.gov (United States)

    Gangadhar, Nalwala Rohitbabu; Balasubramanian, Periyasamy

    2010-10-01

    In this paper, we present the stability analysis of delay differential equations which arise as a result of transportation lag in the CSTR-mechanical separator recycle system. A first order irreversible elementary reaction is considered to model the system and is governed by the delay differential equations. The DDE-BIFTOOL software package is used to analyze the stability of the delay system. The present analysis reveals that the system exhibits delay independent stability for isothermal operation of the CSTR. In the absence of delay, the system is dynamically unstable for non-isothermal operation of the CSTR, and as a result of delay, the system exhibits delay dependent stability.

  20. MULTI-LOOP CONTROL DESIGN IN MULTIVARIABLE (2X2 CONTINUOUS STIRRED TANK REACTOR

    Directory of Open Access Journals (Sweden)

    Abdul Wahid

    2015-06-01

    Full Text Available With this study, the design and tuning of multi-loop for multivariable (2x2 CSTR will be made in order to achieve optimum CSTR control performance. This study used Bequette model reactor and MATLAB software and is expected to be able to cope with disturbances in the reactor so that the reactor system is able to stabilize quickly despite the distractions. In this study, the design will be made using multi-loop approach, along with PI controller as the next step. Then, BLT and auto-tune tuning method will be used in PI controller and given disturbances to both of tuning method. The controller performances are then compared. Results of the study are then analyzed for discussions and conclusions. Results from this study have shown that in terms of disturbance rejection, BLT is better than auto-tune based on comparison between both of controller performances. For IAE for the case of temperature, BLT is 30% better than auto-tune, but it is almost the same for the case of concentration. For settling time for the case of concentration, BLT is 30% better than auto-tune, and for the case of temperature, BLT is 18% better than auto-tune. For rise time for the case of concentration and temperature, BLT is 30% better than auto-tune.

  1. Perancangan dan Simulasi MRAC untui Proses Pengendalian Temperatur pada Continuous Stirred Tank Reactor (CSTR

    Directory of Open Access Journals (Sweden)

    Amelia Sylvia

    2014-03-01

    Full Text Available Temperatur merupakan salah satu variabel proses dasar yang dikendalikan untuk menjaga suhu cairan di dalam reaktor. Model Reference Adaptive Controller (MRAC dengan MIT rule dipilih untuk mencapai spesifikasi respon yang diinginkan pada CSTR. Beban yang bervariasi berupa debit aliran likuid yang masuk ke dalam reaktor dapat menyebabkan perubahan parameter yang mempengaruhi perubahan temperatur output produk pada CSTR. Sebuah simulasi dilakukan dengan menggunakan MATLAB dan hasilnya dianalisa. Respon plant dapat melakukan adaptasi parameter – parameter kontrolernya cukup baik pada nilai gain adaptasi dengan rentang 0.00000010000 sampai 0.00000000001. Waktu yang dibutuhkan untuk mengatasi beban yang bervariasi berupa debit aliran yang masuk ke dalam reaktor dengan nilai yang maksimal (1.5 m^3/min menghasilkan respon plant lebih cepat 42 detik dari pada debit aliran masuk dengan nilai yang nominal (1 m^3/min 63 detik dan minimal (0.5 m^3/min 75 detik.

  2. Feasibility of Underwater Friction Stir Welding and Its Optimization Using Taguchi Method

    OpenAIRE

    Prof. Mohd Abbas1; , Neha mehani2; Atishey Mittal*

    2014-01-01

    In this paper we are approaching to the feasibility of underwater friction stir welding of aluminum alloy which widely has the various applications where strength to density ratio plays a crucial role such as in marine, aircraft and automobile industries. The problems associated with joining of parts through conventional welding method is overcome by use of friction stir welding process yet the friction stir welding encloses the problems such as rapid tool wear especially duri...

  3. CFD simulation of flow patterns in unbaffled stirred tank with CD-6 impeller

    OpenAIRE

    Devi Tamphasana Thiyam; Kumar Bimlesh

    2012-01-01

    Understanding the flow in stirred vessels can be useful for a wide number of industrial applications. There is a wealth of numerical simulations of stirring vessels with standard impeller such as Rushton turbine and pitch blade turbine. Here, a CFD study has been performed to observe the spatial variations (angular, axial and radial) of hydrodynamics (velocity and turbulence field) in unbaffled stirred tank with Concave-bladed Disc turbine (CD-6) impeller. Three speeds (N=296, 638 &...

  4. Investigation of the Microstructure of Joints of Aluminum Alloys Produced by Friction Stir Welding

    Science.gov (United States)

    Kolubaev, E. A.

    2015-02-01

    Special features of the microstructure of joints of aluminum-magnesium and aluminum-copper alloys produced by friction stir welding are analyzed. It is demonstrated that a layered structure with ultradisperse grains is produced by friction stir welding at the center of the weld joint. An analogy is drawn between the microstructures of joints produced by friction stir welding and surface layer produced by sliding friction.

  5. CFD simulation of flow patterns in unbaffled stirred tank with CD-6 impeller

    Directory of Open Access Journals (Sweden)

    Devi Tamphasana Thiyam

    2012-01-01

    Full Text Available Understanding the flow in stirred vessels can be useful for a wide number of industrial applications. There is a wealth of numerical simulations of stirring vessels with standard impeller such as Rushton turbine and pitch blade turbine. Here, a CFD study has been performed to observe the spatial variations (angular, axial and radial of hydrodynamics (velocity and turbulence field in unbaffled stirred tank with Concave-bladed Disc turbine (CD-6 impeller. Three speeds (N=296, 638 & 844.6 rpm have been considered for this study. The angular variations of hydrodynamics of stirred tank were found very less as compared to axial and radial variations.

  6. Laser beam welding and friction stir welding of 6013-T6 aluminium alloy sheet

    International Nuclear Information System (INIS)

    Butt welds of 1.6 mm thick 6013-T6 sheet were produced using laser beam welding and friction stir welding processes. Employing the former joining technique, filler powders of the alloys Al-5%Mg and Al-12%Si were used. Microstructure, hardness profiles, tensile properties and the corrosion behaviour of the welds in the as-welded condition were investigated. The hardness in the weld zone was lower compared to that of the base material in the peak-aged temper. Hardness minima were measured in the fusion zone and in the thermomechanically affected zone for laser beam welded and friction stir welded joints, respectively. Metallographic and fractographic examinations revealed pores in the fusion zone of the laser beam welds. Porosity was higher in welds made using the filler alloy Al-5%Mg than using the filler metal Al-12%Si. Transmission electron microscopy indicated that the β'' (Mg2Si) hardening precipitates were dissolved in the weld zone due to the heat input of the joining processes. Joint efficiencies achieved for laser beam welds depended upon the filler powders, being about 60 and 80% using the alloys Al-5%Mg and Al-12%Si, respectively. Strength of the friction stir weld approached over 80% of the ultimate tensile strength of the 6013-T6 base material. Fracture occurred in the region of hardness minima unless defects in the weld zone led to premature failure. The heat input during welding did not cause a degradation of the corrosion behaviour of the welds, as found in continuous immersion tests in an aqueous chloride-peroxide solution. In contrast to the 6013-T6 parent material, the weld zone was not sensitive to intergranular corrosion. Alternate immersion tests in 3.5% NaCl solution indicated high stress corrosion cracking resistance of the joints. For laser beam welded sheet, the weld zone of alternately immersed specimens suffered severe degradation by pitting and intergranular corrosion, which may be associated with galvanic coupling of filler metal and

  7. Retractable Pin Tools for the Friction Stir Welding Process

    Science.gov (United States)

    1998-01-01

    Two companies have successfully commercialized a specialized welding tool developed at the Marshall Space Flight Center (MSFC). Friction stir welding uses the high rotational speed of a tool and the resulting frictional heat created from contact to crush, 'stir' together, and forge a bond between two metal alloys. It has had a major drawback, reliance on a single-piece pin tool. The pin is slowly plunged into the joint between two materials to be welded and rotated as high speed. At the end of the weld, the single-piece pin tool is retracted and leaves a 'keyhole,' something which is unacceptable when welding cylindrical objects such as drums, pipes and storage tanks. Another drawback is the requirement for different-length pin tools when welding materials of varying thickness. An engineer at the MSFC helped design an automatic retractable pin tool that uses a computer-controlled motor to automatically retract the pin into the shoulder of the tool at the end of the weld, preventing keyholes. This design allows the pin angle and length to be adjusted for changes in material thickness and results in a smooth hole closure at the end of the weld. Benefits of friction stir welding, using the MSFC retractable pin tool technology, include the following: The ability to weld a wide range of alloys, including previously unweldable and composite materials; provision of twice the fatigue resistance of fusion welds and no keyholes; minimization of material distortion; no creation of hazards such as welding fumes, radiation, high voltage, liquid metals, or arcing; automatic retraction of the pin at the end of the weld; and maintaining full penetration of the pin.

  8. Friction Stir Spot Welding of Advanced High Strength Steels

    Energy Technology Data Exchange (ETDEWEB)

    Hovanski, Yuri; Santella, M. L.; Grant, Glenn J.

    2009-12-28

    Friction stir spot welding was used to join two advanced high-strength steels using polycrystalline cubic boron nitride tooling. Numerous tool designs were employed to study the influence of tool geometry on weld joints produced in both DP780 and a hot-stamp boron steel. Tool designs included conventional, concave shouldered pin tools with several pin configurations; a number of shoulderless designs; and a convex, scrolled shoulder tool. Weld quality was assessed based on lap shear strength, microstructure, microhardness, and bonded area. Mechanical properties were functionally related to bonded area and joint microstructure, demonstrating the necessity to characterize processing windows based on tool geometry.

  9. Friction Stir Processing of Aluminium-Silicon Alloys

    OpenAIRE

    Chun Yip Chan

    2011-01-01

    Friction Stir Processing (FSP) has the potential for locally enhancing the properties of Al-Si alloy castings, for demanding applications within the automotive industry. In this thesis, the effect of FSP has been examined on three different cast Al-Si alloys:i) A Hypoeutectic Al-8.9wt%Si Alloyii) A Hypereutectic Al-12.1wt%Si Alloyiii) A Hypereutectic Al-12.1wt%Si-2.4wt%Ni AlloyThe influence of different processing parameters has been investigated at a fundamental level. Image analysis of part...

  10. Friction stir welding (FSW of aluminium foam sandwich panels

    Directory of Open Access Journals (Sweden)

    M. Bušić

    2016-07-01

    Full Text Available The article focuses on the influence of welding speed and tool tilt angle upon the mechanical properties at the friction stir welding of aluminium foam sandwich panels. Double side welding was used for producing butt welds of aluminium sandwich panels applying insertion of extruded aluminium profile. Such insertion provided lower pressure of the tool upon the aluminium panels, providing also sufficient volume of the material required for the weldment formation. Ultimate tensile strength and flexural strength for three-point bending test have been determined for samples taken from the welded joints. Results have confirmed anticipated effects of independent variables.

  11. Friction stir welding tool and process for welding dissimilar materials

    Energy Technology Data Exchange (ETDEWEB)

    Hovanski, Yuri; Grant, Glenn J; Jana, Saumyadeep; Mattlin, Karl F

    2013-05-07

    A friction stir welding tool and process for lap welding dissimilar materials are detailed. The invention includes a cutter scribe that penetrates and extrudes a first material of a lap weld stack to a preselected depth and further cuts a second material to provide a beneficial geometry defined by a plurality of mechanically interlocking features. The tool backfills the interlocking features generating a lap weld across the length of the interface between the dissimilar materials that enhances the shear strength of the lap weld.

  12. Friction Stir Processing of ODS and FM Steels

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Suk Hoon; Chun, Young Bum; Noh, Sang Hoon; Jang, Jin Sung; Kim, Tae Kyu [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2013-10-15

    In ODS steels, it is well known that uniform nano-oxide dispersoids act as pinning points to obstruct dislocation and grain boundary motion, however, those advantages will be disappeared while the material is subjected to the high temperature of conventional fusion welding. Rotary friction welding, also referred to as friction stir welding (FSW), has shown great promise as a method for welding traditionally difficult to weld materials such as aluminum alloys. This relatively new technology has more recently been applied to higher melting temperature alloys such as steels, nickel-based and titanium alloys. Friction stir processing (FSP) is a method of changing the properties of a metal through intense, localized plastic deformation. FSW is the precursor of the FSP technique. When ideally implemented, this process mixes the material without changing the phase and creates a microstructure with fine, equiaxed grains. This homogeneous grain structure, separated by high-angle boundaries, allows some alloys to take on superplastic properties. In this study, FSW is used as a substitutive welding process between FMS tube and ODS parts. The dimension of tube is 7.0 OD, 0.5 T. During the FSW, dynamic-recrystallized grains are developed; the uniform oxides dispersion is preserved in the metal matrix. The microstructure and microtexture of the material near the stir zone is found to be influenced by the rotational behavior of the tool. The additive effect from FSP on sample surface is considered. Since the mechanical alloying (MA) and FSP commonly apply extreme shear deformation on materials, the dispersion of oxide particle in ODS steels is very active during both processes. Friction stir welding appears to be a very promising technique for the welding of FMS and ODS steels in the form of sheet and tube. FSW could successfully produce defect-free welds on FMS tubes and ODS ring assembly. FSW produces a fine grain structure consisting of ferrite and martensite, and the oxide

  13. Hybrid Friction Stir Welding of High-carbon Steel

    Institute of Scientific and Technical Information of China (English)

    Don-Hyun Choi; Seung-Boo Jung; Chang-Yong Lee; Byung-Wook Ahn; Jung-Hyun Choi; Yun-Mo Yeon; Keun Song; Seung-Gab Hong; Won-Bae Lee; Ki-Bong Kang

    2011-01-01

    A high-carbon steel joint, SK5 (0.84 wt% C), was successfully welded by friction stir welding (FSW), both without and with a gas torch, in order to control the cooling rate during welding. After welding, the weld zone comprised gray and black regions, corresponding to microstructural variation: a martensite structure and a duplex structure of ferrite and cementite, respectively. The volume fraction of the martensite structure and the Vickers hardness in the welds were decreased with the using of the gas torch, which was related with the lower cooling rate.

  14. Developing Friction Stir Welding Process Model for ICME Application

    Science.gov (United States)

    Yang, Yu-Ping

    2015-01-01

    A framework for developing a product involving manufacturing processes was developed with integrated computational materials engineering approach. The key component in the framework is a process modeling tool which includes a thermal model, a microstructure model, a thermo-mechanical, and a property model. Using friction stir welding (FSW) process as an example, development of the process modeling tool was introduced in detail. The thermal model and the microstructure model of FSW of steels were validated with the experiment data. The model can predict reasonable temperature and hardness distributions as observed in the experiment. The model was applied to predict residual stress and joint strength of a pipe girth weld.

  15. Fatigue Crack Growth in Peened Friction Stir Welds

    Science.gov (United States)

    Forth, Scott C.; Hatamleh, Omar

    2008-01-01

    Friction stir welding induces residual stresses that accelerates fatigue crack growth in the weld nugget. Shot peening over the weld had little effect on growth rate. Laser peening over the weld retarded the growth rate: Final crack growth rate was comparable to the base, un-welded material. Crack tunneling evident from residual compressive stresses. 2195-T8 fracture surfaces were highly textured. Texturing makes comparisons difficult as the material system is affecting the data as much as the processing. Material usage becoming more common in space applications requiring additional work to develop useful datasets for damage tolerance analyses.

  16. Fractal Continuation

    OpenAIRE

    Barnsley, Michael F.; Vince, Andrew

    2012-01-01

    A fractal function is a function whose graph is the attractor of an iterated function system. This paper generalizes analytic continuation of an analytic function to continuation of a fractal function.

  17. Friction stir welding of nuclear grade dissimilar steels

    International Nuclear Information System (INIS)

    SA508 Class 3 low alloy Mn-Mo-Ni steel is a reactor pressure vessel material, widely used in the world. In the reactors, fuel is arranged in a row of fuel pins and linked with portable control rods. The fuel is in a SA 508 steel container through which water is pumped at a high pressure into reactor vessel via cold lag pipeline. The water to act as both a coolant and a moderator. After absorbing the heat from the core of reactor, pressurised water is passed on a steam generator, via hot lag pipeline. Both hot lag and cold lag pipe lines are made of SS 304 LN steel. These both steels are generally welded by common arc welding process which may causes carbon migration, thermal stress, metallurgical deterioration, residual stress, etc. Friction stir welding (FSW) is a new solid state welding process develop by TWI in 1991 (UK) which generally removed all type of solidification problem. In this study Friction stir welding is performed for welding of SA 508 and SS 304 LN dissimilar steels. Defect free sound weld were produced having strength more than the SS 304 LN steel and toughness more than the SA 508. Microstructure and hardness represents the formation of martensite formation in weld nugget. (author)

  18. Modified Mathematical Model For Neutralization System In Stirred Tank Reactor

    Directory of Open Access Journals (Sweden)

    Ahmmed Saadi Ibrehem

    2011-05-01

    Full Text Available A modified model for the neutralization process of Stirred Tank Reactors (CSTR reactor is presented in this study. The model accounts for the effect of strong acid [HCL] flowrate and strong base [NaOH] flowrate with the ionic concentrations of [Cl-] and [Na+] on the Ph of the system. In this work, the effect of important reactor parameters such as ionic concentrations and acid and base flowrates on the dynamic behavior of the CSTR is investigated and the behavior of mathematical model is compared with the reported models for the McAvoy model and Jutila model. Moreover, the results of the model are compared with the experimental data in terms of pH dynamic study. A good agreement is observed between our model prediction and the actual plant data. © 2011 BCREC UNDIP. All rights reserved(Received: 1st March 2011, Revised: 28th March 2011; Accepted: 7th April 2011[How to Cite: A.S. Ibrehem. (2011. Modified Mathematical Model For Neutralization System In Stirred Tank Reactor. Bulletin of Chemical Reaction Engineering & Catalysis, 6(1: 47-52. doi:10.9767/bcrec.6.1.825.47-52][How to Link / DOI: http://dx.doi.org/10.9767/bcrec.6.1.825.47-52 || or local:  http://ejournal.undip.ac.id/index.php/bcrec/article/view/825 ] | View in 

  19. Friction Stir Weld Restart+Reweld Repair Allowables

    Science.gov (United States)

    Clifton, Andrew

    2008-01-01

    A friction stir weld (FSW) repair method has been developed and successfully implemented on Al 2195 plate material for the Space Shuttle External Fuel Tank (ET). The method includes restarting the friction stir weld in the termination hole of the original weld followed by two reweld passes. Room temperature and cryogenic temperature mechanical properties exceeded minimum FSW design strength and compared well with the development data. Simulated service test results also compared closely to historical data for initial FSW, confirming no change to the critical flaw size or inspection requirements for the repaired weld. Testing of VPPA fusion/FSW intersection weld specimens exhibited acceptable strength and exceeded the minimum design value. Porosity, when present at the intersection was on the root side toe of the fusion weld, the "worst case" being 0.7 inch long. While such porosity may be removed by sanding, this "worst case" porosity condition was tested "as is" and demonstrated that porosity did not negatively affect the strength of the intersection weld. Large, 15-inch "wide panels" FSW repair welds were tested to demonstrate strength and evaluate residual stresses using photo stress analysis. All results exceeded design minimums, and photo stress analysis showed no significant stress gradients due to the presence of the restart and multi-pass FSW repair weld.

  20. Simulation of Friction Stir Processing in 304L Stainless Steel

    Directory of Open Access Journals (Sweden)

    MilesM.P.

    2016-01-01

    Full Text Available A major dilemma facing the nuclear industry is repair or replacement of stainless steel reactor components that have been exposed to neutron irradiation. When conventional fusion welding is used for weld repair, the high temperatures and thermal stresses inherent in the process enhance the growth of helium bubbles, causing intergranular cracking in the heat-affected zone (HAZ. Friction stir processing (FSP has potential as a weld repair technique for irradiated stainless steel, because it operates at much lower temperatures than fusion welding, and is therefore less likely to cause cracking in the HAZ. Numerical simulation of the FSP process in 304L stainless steel was performed using an Eulerian finite element approach. Model input required flow stresses for the large range of strain rates and temperatures inherent in the FSP process. Temperature predictions in three locations adjacent to the stir zone were accurate to within 4% of experimentally measure values. Prediction of recrystallized grain size at a location about 6mm behind the tool center was less accurate, because the empirical model employed for the prediction did not account for grain growth that occurred after deformation in the experiment was halted.

  1. Mixing Study in an Unbaffled Stirred Precipitator Using LES Modelling

    Directory of Open Access Journals (Sweden)

    Murielle Bertrand

    2012-01-01

    Full Text Available This paper describes the CFD modelling of a reactor operating in the nuclear industry using LES approach. The reactor consists of an unbaffled stirred tank reactor in which plutonium precipitation reactions are carried out. The flow generated in such a precipitator is complex and there is very little information available in the literature about unbaffled reactors stirred with magnetic rod. That is why a hydrodynamic modelling has been developed using computational fluid dynamics (CFD in order to get accurate description of mixing phenomena inside the precipitator and therefore to be able to predict the solid particle properties. Due to the strong turbulence anisotropy, the turbulence transport simulation is achieved by a large eddy simulation (LES approach which gives unsteady solutions. The numerical simulations are performed in 3D using the Trio_U code developed at the Commissariat à l'Énergie Atomique. The predictive performances of the modelling are analysed through a mixing phenomena study. Both experimental and numerical studies are performed. This work shows how hydrodynamics inside the reactor can have a noticeable effect on the precipitate properties and how LES modelling is a very effective tool for the process control.

  2. Effect of cryogenic cooling on corrosion of friction stir welded AA7010-T7651

    DEFF Research Database (Denmark)

    Jariyaboon, Manthana; Davenport, A. J.; Ambat, Rajan;

    2010-01-01

    Purpose - The purpose of this paper is to study how cryogenic CO2 cooling during the welding process affects corrosion behaviour of friction stir welding (FSW) AA7010-T7651. Design/methodology/approach - Friction stir welded AA7010-17651 was produced with a rotation speed of 288 rpm and a travel ...

  3. Multi-Criteria Optimization in Friction Stir Welding Using a Thermal Model with Prescribed Material Flow

    DEFF Research Database (Denmark)

    Tutum, Cem Celal; Deb, Kalyanmoy; Hattel, Jesper Henri

    2013-01-01

    Friction stir welding (FSW) is an innovative solid-state joining process providing products with superior mechanical properties. It utilizes a rotating tool being submerged into the joint line and traversed while stirring the two pieces of metal together to form the weld. The temperature distribu...

  4. EFFECT OF BAKELITE INTERLAYER POWDER ON FRICTION STIR SPOT WELDING OF THERMOPLASTIC POLYMERS

    OpenAIRE

    Bekir ÇEVİK

    2014-01-01

    In this study, effect of bakelite interlayer powder on friction stir spot welding of polyethylene materials were investigated. 3 mm thick polyethylene materials were used in the experiments. 900 rpm rotational speed, 70, 100 and 130 seconds stirring time and 60 second waiting time were selected for the welding processes. Tensile-shear tests were applied on welded specimens and mechanical performances were determined

  5. Strong sensitivity of Southern Ocean carbon uptake and nutrient cycling to wind stirring

    Directory of Open Access Journals (Sweden)

    K. B. Rodgers

    2013-09-01

    Full Text Available Here we test the hypothesis that winds have an important role in determining the rate of exchange of CO2 between the atmosphere and ocean through wind stirring over the Southern Ocean. This is tested with a sensitivity study using an ad hoc parameterization of wind stirring in an ocean carbon cycle model. The objective is to identify the way in which perturbations to the vertical density structure of the planetary boundary in the ocean impacts the carbon cycle and ocean biogeochemistry. Wind stirring leads to reduced uptake of CO2 by the Southern Ocean over the period 2000–2006, with differences of order 0.9 Pg C yr−1 over the region south of 45° S. Wind stirring impacts not only the mean carbon uptake, but also the phasing of the seasonal cycle of carbon and other species associated with ocean biogeochemistry. Enhanced wind stirring delays the seasonal onset of stratification, and this has large impacts on both entrainment and the biological pump. It is also found that there is a strong sensitivity of nutrient concentrations exported in Subantarctic Mode Water (SAMW to wind stirring. This finds expression not only locally over the Southern Ocean, but also over larger scales through the impact on advected nutrients. In summary, the large sensitivity identified with the ad hoc wind stirring parameterization offers support for the importance of wind stirring for global ocean biogeochemistry, through its impact over the Southern Ocean.

  6. Effects of Laser Peening, and Shot Peening, on Friction Stir Welding

    Science.gov (United States)

    Hatamleh, Omar; Hackel, Lloyd; Rankin, Jon; Truong, Chanh; Walter, Matt

    2006-01-01

    A viewgraph presentation describing the effects of laser peening and shot peening on friction stir welding is shown. The topics include: 1) Background; 2) Friction Stir Welding (FSW); 3) Microstructure; 4) Laser & Shot Peening; 5) Residual Stresses; 6) Tensile Behavior; 7) Fatigue Life & Surface Roughness; 8) Crack Growth; and 9) Benefits.

  7. Gas-solid hydroxyethylation of potato starch in a stirred vibrating fluidized bed reactor

    NARCIS (Netherlands)

    Kuipers, N.J M; Stamhuis, Eize; Beenackers, A.A C M

    1996-01-01

    A novel reactor for modifying cohesive C-powders such as in the gas-solid hydroxyethylation of semidry potato starch is characterized, the so-called stirred vibrating fluidized bed reactor. Good fluidization characteristics are obtained in this reactor for certain combinations of stirring and vibrat

  8. Colosed-Loop Control of the Thermal Stir Welding Process to Enable Rapid Process/Ppart Qualification Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Thermal Stir Welding (TSW) provides advancement over the more conventional Friction Stir Welding (C-FSW) process because it separates the primary processes...

  9. Closed-Loop Control of the Thermal Stir Welding Process to Enable Rapid Process/Part Qualification Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Thermal Stir Welding (TSW) provides advancement over the more conventional Friction Stir Welding (C-FSW) process because it separates the primary processes...

  10. ZnS thin film deposited with chemical bath deposition process directed by different stirring speeds

    International Nuclear Information System (INIS)

    In this combined film thickness, scanning electron microscopy (SEM), X-ray diffraction and optical properties study, we explore the effects of different stirring speeds on the growth and optical properties of ZnS film deposited by CBD method. From the disclosed changes of thickness of ZnS film, we conclude that film thickness is independent of the stirring speeds in the heterogeneous process (deposition time less than 40 min), but increases with the stirring speeds and/or deposition time increasing in the homogeneous process. Grazing incident X-ray diffraction (GIXRD) and the study of optical properties disclosed that the ZnS films grown with different stirring speeds show partially crystallized film and exhibit good transmittance (70-88% in the visible region), but the stirring speeds cannot give much effects on the structure and optical properties in the homogeneous process.

  11. The Effect of Premixed Al-Cu Powder on the Stir Zone in Friction Stir Welding of AA3003-H18

    Science.gov (United States)

    Abnar, B.; Kazeminezhad, M.; Kokabi, A. H.

    2015-02-01

    In this research, 3-mm-thick AA3003-H18 non-heat-treatable aluminum alloy plates were joined by friction stir welding (FSW). It was performed by adding pure Cu and premixed Cu-Al powders at various rotational speeds of 800, 1000, and 1200 rpm and constant traveling speeds of 100 mm/min. At first, the powder was filled into the gap (0.2 or 0.4 mm) between two aluminum alloy plates, and then the FSW process was performed in two passes. The microstructure, mechanical properties, and formation of intermetallic compounds were investigated in both cases of using pure Cu and premixed Al-Cu powders. The results of using pure Cu and premixed Al-Cu powders were compared in the stir zone at various rotational speeds. The copper particle distribution and formation of Al-Cu intermetallic compounds (Al2Cu and AlCu) in the stir zone were desirable using premixed Al-Cu powder into the gap. The hardness values were significantly increased by formation of Al-Cu intermetallic compounds in the stir zone and it was uniform throughout the stir zone when premixed Al-Cu powder was used. Also, longitudinal tensile strength from the stir zone was higher when premixed Al-Cu powder was used instead of pure Cu powder.

  12. Numerical simulation of temperature distribution using finite difference equations and estimation of the grain size during friction stir processing

    Energy Technology Data Exchange (ETDEWEB)

    Arora, H.S. [School of Mechanical, Material and Energy Engineering, Indian Institute of Technology Ropar, Rupnagar, Punjab 140001 (India); Singh, H., E-mail: harpreetsingh@iitrpr.ac.in [School of Mechanical, Material and Energy Engineering, Indian Institute of Technology Ropar, Rupnagar, Punjab 140001 (India); Dhindaw, B.K. [School of Materials and Mineral Resources, Universiti Sains Malaysia, Engineering Campus, Nibong Tebal, Pulau Penang 14300 (Malaysia)

    2012-05-01

    Highlights: Black-Right-Pointing-Pointer Magnesium alloy AE42 was friction stir processed under different cooling conditions. Black-Right-Pointing-Pointer Heat flow model was developed using finite difference heat equations. Black-Right-Pointing-Pointer Generalized MATLAB code was developed for solving heat flow model. Black-Right-Pointing-Pointer Regression equation for estimation of grain size was developed. - Abstract: The present investigation is aimed at developing a heat flow model to simulate temperature history during friction stir processing (FSP). A new approach of developing implicit form of finite difference heat equations solved using MATLAB code was used. A magnesium based alloy AE42 was friction stir processed (FSPed) at different FSP parameters and cooling conditions. Temperature history was continuously recorded in the nugget zone during FSP using data acquisition system and k type thermocouples. The developed code was validated at different FSP parameters and cooling conditions during FSP experimentation. The temperature history at different locations in the nugget zone at different instants of time was further utilized for the estimation of grain growth rate and final average grain size of the FSPed specimen. A regression equation relating the final grain size, maximum temperature during FSP and the cooling rate was developed. The metallurgical characterization was done using optical microscopy, SEM, and FIB-SIM analysis. The simulated temperature profiles and final average grain size were found to be in good agreement with the experimental results. The presence of fine precipitate particles generated in situ in the investigated magnesium alloy also contributed in the evolution of fine grain structure through Zener pining effect at the grain boundaries.

  13. Stir-bar supported micro-solid-phase extraction for the determination of polychlorinated biphenyl congeners in serum samples.

    Science.gov (United States)

    Sajid, Muhammad; Basheer, Chanbasha

    2016-07-15

    In present work, a new configuration of micro-solid phase extraction was introduced and termed as stir-bar supported micro-solid-phase extraction (SB-μ-SPE). A tiny stir-bar was packed inside the porous polypropylene membrane along with sorbent material and the edges of membrane sheet were heat sealed to secure the contents. The packing of stir-bar inside the μ-SPE device does not allow the device to stick with the wall or any corner of the sample vial during extraction, which is, however, a frequent observation in routine μ-SPE. Moreover, it enhances effective surface area of the sorbent exposed to sample solution through continuous agitation (motion and rotation). It also completely immerses the SB-μ-SPE device in the sample solution even for non-polar sorbents. Polychlorinated biphenyls (PCBs) were selected as model compounds and the method performance was evaluated in human serum samples. After extraction, samples were analyzed by gas chromatography mass spectrometry (GC-MS). The factors that affect extraction efficiency of SB-μ-SPE were optimized. Under optimum conditions, a good linearity (0.1-100ngmL(-1)) with coefficients of determinations ranging from 0.9868 to 0.9992 was obtained. Limits of detections were ranged between 0.003 and 0.047ngmL(-1). Acceptable values for inter-day (3.2-9.1%) and intra-day (3.1-7.2%) relative standard deviations were obtained. The optimized method was successfully applied to determine the concentration of PCB congeners in human serum samples. PMID:27291862

  14. Tool for Two Types of Friction Stir Welding

    Science.gov (United States)

    Carter, Robert

    2006-01-01

    A tool that would be useable in both conventional and self-reacting friction stir welding (FSW) has been proposed. The tool would embody both a prior tooling concept for self-reacting FSW and an auto-adjustable pin-tool (APT) capability developed previously as an augmentation for conventional FSW. Some definitions of terms are prerequisite to a meaningful description of the proposed tool. In conventional FSW, depicted in Figure 1, one uses a tool that includes (1) a rotating shoulder on top (or front) of the workpiece and (2) a rotating pin that protrudes from the shoulder into the depth of the workpiece. The main axial force exerted by the tool on the workpiece is reacted through a ridged backing anvil under (behind) the workpiece. When conventional FSW is augmented with an APT capability, the depth of penetration of the pin into the workpiece is varied in real time by a position- or force-control system that extends or retracts the pin as needed to obtain the desired effect. In self-reacting (also known as self-reacted) friction stir welding (SR-FSW), there are two rotating shoulders: one on top (or front) and one on the bottom (or back) of the workpiece. In this case, a threaded shaft protrudes from the tip of the pin to beyond the back surface of the workpiece. The back shoulder is held axially in place against tension by a nut on the threaded shaft. The main axial force exerted on the workpiece by the tool and front shoulder is reacted through the back shoulder and the threaded shaft, back into the FSW machine head, so that a backing anvil is no longer needed. A key transmits torque between the bottom shoulder and the threaded shaft, so that the bottom shoulder rotates with the shaft. A tool for SRFSW embodying this concept was reported in "Mechanism for Self-Reacted Friction Stir Welding" (MFS-31914), NASA Tech Briefs, Vol. 28, No. 10 (October 2004), page 53. In its outward appearance, the proposed tool (see Figure 2) would fit the above description of an SR

  15. Friction Stir Spot Welding of 6061 Aluminum-to-Copper

    Science.gov (United States)

    Heideman, Robert J.

    Friction stir spot welding (FSSW) between 1.5mm thick 6061 Al on top and 1.5mm thick Cu at bottom was conducted. First, weld parameters and the weld macrostructure that were necessary to form good quality welds, as determined using lap shear weld strength, were identified. Tool rotation speed and tool pin length are key variables that control weld strength. To obtain high quality strong welds, a Cu ring extruded upward from the lower Cu sheet into the upper 6061 Al-sheet, which promoted bonding and interlocking between the sheets, and an Al-rich stir zone between Cu ring and weld keyhole were both necessary. Second, a technique where the tool remained in the sample after FSSW helped determine the material flow that takes place during high quality weld formation and the functions of the welding tool features. The tool threads cause 6061 Al from the upper sheet to move downward into the region near the threads. The tool shoulder causes a counter flow movement of 6061 Al that results in the formation of the Al-rich stir zone and also causes the upward extrusion of the lower Cu sheet. This technique also identified that a Cu-rich material forms on the tool tip, that this material sheds and rebuilds during subsequent welds, and that this material can form large Cu-rich particles that can completely fill the tool threads, impede proper material flow and lead to a low strength, poor quality weld. Third, to further understand welding parameters, weld temperatures, torque, and vertical forces were measured. Temperature data was collected using a tool holder that permitted wireless thermocouple data collection. Through these measurements, rotational plunge weld energy was recognized as important in determining if a quality weld formed, and weld plunge rate was identified as the welding parameter that significantly impacted rotational weld plunge energy. The final phase of research was to improve weld quality consistency. Through repetitive trials with a single tool

  16. Mixing-Structure Relationship in Jet-Stirred Reactors

    KAUST Repository

    Ayass, Wassim W.

    2016-05-26

    In this study, measurements were performed to assess the overall mixing in jet-stirred reactors (JSRs) passively agitated by feed nozzles. The reactor diameter, nozzle shape, and nozzle diameter were varied to determine the effects of these geometrical parameters on mixing. The mixing was studied at ambient conditions using laser absorption spectroscopy to follow the exit concentration of a tracer gas, carbon dioxide, after a step change in its input flow. The results indicate that the use of a JSR of diameter D = 40 mm, having inclined or crossed nozzles of diameter d = 1 mm is recommended for low residence times up to 0.4 sec, while at moderate/high residence times 0.5-5 sec the use of a JSR of D = 56 mm and d = 0.3 mm having crossed nozzles is suggested.

  17. Electrical process tomography: seeing "without eyes" inside stirred vessels

    Institute of Scientific and Technical Information of China (English)

    MANN R.

    2005-01-01

    Body-scanning exploiting 3-D imaging has revolutionised diagnostics and treatment in medicine. Process engineers would like to be similarly able to image chemical process units in 3-D, but without the £multi-million price tag. UMIST and Leeds University have together, through the Virtual Centre for Industrial Process Tomography (http://www. vcipt.org), pioneered several electrical process tomography techniques and used them in a variety of applications. Illustrations are presented to show how electrical resistance tomography (ERT) has been developed for typical stirred vessels widely encountered in batch process manufacturing. The technique is potentially fast and inexpensive and capable of imaging both dynamic and pseudo-stationary processes. Examples from UMIST's two-tonne vessel will be presented for miscible tracer mixing, as well as gas-liquid and solid-liquid mixing.

  18. Friction Stir Welding of ODS and RAFM Steels

    Science.gov (United States)

    Yu, Zhenzhen; Feng, Zhili; Hoelzer, David; Tan, Lizhen; Sokolov, Mikhail A.

    2015-09-01

    Advanced structural materials such as oxide dispersion strengthened steels and reduced-activation ferritic/martensitic steels are desired in fusion reactors as primary candidate materials for first wall and blanket structures, due to their excellent radiation and high-temperature creep resistance. However, their poor fusion weldability has been the major technical challenge limiting practical applications. For this reason, solid-state friction stir welding (FSW) has been considered for such applications. In this work, the effect of FSW parameters on joining similar and dissimilar advanced structural steels was investigated. Scanning electron microscopy and electron backscatter diffraction methods were used to reveal the effects of FSW on grain size, micro-texture distribution, and phase stability. Hardness mapping was performed to evaluate mechanical properties. Post weld heat treatment was also performed to tailor the microstructure in the welds in order to match the weld zone mechanical properties to the base material.

  19. Material Flow during Friction Stir Welding of HSLA 65 Steel

    Science.gov (United States)

    Young, John; Field, David; Nelson, Tracy

    2013-07-01

    Material flow during friction stir welding of HSLA-65 steel was investigated by crystallographic texture analysis. During the welding process, the steel deforms primarily by local shear deformation in the austenite phase and then transforms upon cooling. Texture data from three weld specimens were compared to theoretical textures calculated using ideal Euler angles for shear in face centered cubic (FCC) structures transformed by the Kurdjumov-Sacks (KS) relationship. These theoretical textures show similarities to the experimental textures. Texture data from the weld specimens revealed a rotation of the shear direction corresponding to the tangent of the weld tool on both the area directly under the weld tool shoulder and weld cross sections. In addition, texture data showed that while the shear plane of the area under the weld tool shoulder remained constant, the shear plane of the weld cross sections is influenced by the weld tool pin.

  20. Grain size reduction by electromagnetic stirring inside gold alloys

    Science.gov (United States)

    Ernst, R.; Mangelinck-Noël, N.; Hamburger, J.; Garnier, C.; Ramoni, P.

    2005-06-01

    The final properties of cast materials depend greatly on the solidification process undergone by the material. In this paper, we study gold alloys dedicated to the watch industry and jewellery in the framework of a research collaboration with the Metalor Company. The aim is to improve the concentration homogeneity of the ingots by controlling the solidification step. It can be achieved by reducing segregations by a decrease in the grain size. For this purpose, we set up a multiphase electromagnetic stirring of the melt to favour the growth of finer grains and improve the homogeneity of the composition. We first design an electromagnetic stirrer by numerical simulation. The stirrer is then implemented on a model experiment. Eventually, the alloys are characterised by metallography and etching to evidence the grain structure. As expected, we obtain a substantial reduction of the grain size although, some work remains to be done to attain the final goal of even finer grains.

  1. The Stirred Tank Reactor Polymer Electrolyte Membrane Fuel Cell

    CERN Document Server

    Benziger, J; Karnas, E; Moxley, J; Teuscher, C; Kevrekidis, Yu G; Benziger, Jay

    2003-01-01

    The design and operation of a differential Polymer Electrolyte Membrane (PEM) fuel cell is described. The fuel cell design is based on coupled Stirred Tank Reactors (STR); the gas phase in each reactor compartment was well mixed. The characteristic times for reactant flow, gas phase diffusion and reaction were chosen so that the gas compositions at both the anode and cathode are uniform. The STR PEM fuel cell is one-dimensional; the only spatial gradients are transverse to the membrane. The STR PEM fuel cell was employed to examine fuel cell start- up, and its dynamic responses to changes in load, temperature and reactant flow rates. Multiple time scales in systems response are found to correspond to water absorption by the membrane, water transport through the membrane and stress-related mechanical changes of the membrane.

  2. Prolegomena to the Study of Friction Stir Welding

    Science.gov (United States)

    Nunes, Arthur C., Jr.

    2010-01-01

    The literature contains many approaches toward modeling of the friction stir welding (FSW) process with varying treatments of the weld metal properties. It is worthwhile to consider certain fundamental features of the process before attempting to interpret FSW phenomena: Because of the unique character of metal deformation (as opposed to, say, viscous deformation) a velocity "discontinuity" or shear surface occurs in FSW and determines much of the character of the welding mechanism. A shear surface may not always produce a sound bond. Balancing mechanical power input against conduction and convection heat losses yields a relation, a "temperature index", between spindle speed and travel speed to maintain constant weld temperature. But many process features are only weakly dependent upon temperature. Thus, unlike modeling of metal forming processes, it may be that modeling the FSW process independently of the material conditions has some merit.

  3. Pin Tool Geometry Effects in Friction Stir Welding

    Science.gov (United States)

    Querin, J. A.; Rubisoff, H. A.; Schneider, J. A.

    2009-01-01

    In friction stir welding (FSW) there is significant evidence that material can take one of two different flow paths when being displaced from its original position in front of the pin tool to its final position in the wake of the weld. The geometry of the pin tool, along with the process parameters, plays an important role in dictating the path that the material takes. Each flow path will impart a different thermomechanical history on the material, consequently altering the material microstructure and subsequent weld properties. The intention of this research is to isolate the effect that different pin tool attributes have on the flow paths imparted on the FSWed material. Based on published weld tool geometries, a variety of weld tools were fabricated and used to join AA2219. Results from the tensile properties and microstructural characterization will be presented.

  4. Micro friction stir welding of copper electrical contacts

    Directory of Open Access Journals (Sweden)

    D. Klobčar

    2014-10-01

    Full Text Available The paper presents an analysis of micro friction stir welding (μFSW of electrolytic tough pitch copper (CuETP in a lap and butt joint. Experimental plan was done in order to investigate the influence of tool design and welding parameters on the formation of defect free joints. The experiments were done using universal milling machine where the tool rotation speed varied between 600 and 1 900 rpm, welding speed between 14 and 93 mm/min and tilt angle between 3° and 5°. From the welds samples for analysis of microstructure and samples for tensile tests were prepared. The grain size in the nugget zone was greatly reduced compared to the base metal and the joint tensile strength exceeded the strength of the base metal.

  5. Improving heat transfer in stirred tanks cooled by helical coils

    Directory of Open Access Journals (Sweden)

    Pedrosa S.M.C.P.

    2003-01-01

    Full Text Available Stirred Tank Reactors are extensively used in chemical industries. When they are used for highly exothermic reactions, jackets or coils are employed for heat removal. Internal coils can be either helical or axial and they considerably affect the flow inside the reactor because they impose an additional resistance to flow circulation. The aim of this work is to show that the design of vessels cooled by helical coils can be further improved. The design of these reactors follows very much the geometry proposed by Oldshue and Gretton (1954, and some minor modifications in the coil arrangements are likely to improve internal circulation inside these vessels mainly in the region between coils and wall of the vessel. Results show a gain in performance when small alterations are made specially in the shape of the coil arrangement.

  6. Modelling the Thermomechanical Conditions in Friction Stir Welding

    DEFF Research Database (Denmark)

    Schmidt, Henrik Nikolaj Blich

    Friction Stir Welding is a solid-state welding process invented by TWI in 1991. The FSW process is unique in the sense that joining of un-weldable alloys readily can be made. The thermomechanical conditions present in the workpiece during the welding process are of great interest since...... these control the properties of the weld. In the present work, a set of experimental, analytical and numerical analyses are carried out in order to evaluate the thermomechanical conditions descriptive for welding of aluminium, in this case AA2024-T3, under a specific set of welding parameters. Despite...... these specific data, the developed models can be applied for other alloys and welding parameters as well. A detailed experiment is carried out which constitutes the basis for the development and validation of the numerical and analytical models presented in this work. The contact condition at the tool...

  7. Friction stir welding (FSW process of copper alloys

    Directory of Open Access Journals (Sweden)

    M. Miličić

    2016-01-01

    Full Text Available The present paper analyzes the structure of the weld joint of technically pure copper, which is realized using friction stir welding (FSW. The mechanism of thermo-mechanical processes of the FSW method has been identified and a correlation between the weld zone and its microstructure established. Parameters of the FSW welding technology influencing the zone of the seam material and the mechanical properties of the resulting joint were analyzed. The physical joining consists of intense mixing the base material along the joint line in the “doughy” phase. Substantial plastic deformations immediately beneath the frontal surface of tool provide fine-grained structure and a good quality joint. The optimum shape of the tool and the optimum welding regime (pressure force, rotation speed and the traverse speed of the tool in the heat affected zone enable the achievement of the same mechanical properties as those of the basic material, which justifies its use in welding reliable structures.

  8. Metal cutting analogy for establishing Friction Stir Welding process parameters

    Science.gov (United States)

    Stafford, Sylvester Allen

    A friction stir weld (FSW) is a solid state joining operation whose processing parameters are currently determined by lengthy trial and error methods. To implement FSWing rapidly in various applications will require an approach for predicting process parameters based on the physics of the process. Based on hot working conditions for metals, a kinematic model has been proposed for calculating the shear strain and shear strain rates during the FSW process, validation of the proposed model with direct measuring is difficult however. Since the shear strain and shear strain rates predicted for the FSW process, are similar to those predicted in metal cutting, validation of the FSW algorithms with microstructural studies of metal chips may be possible leading to the ability to predict FSW processing parameters.

  9. Microstructure characterization of Friction Stir Spot Welded TRIP steel

    DEFF Research Database (Denmark)

    Lomholt, Trine Colding; Adachi, Yoshitaka; Peterson, Jeremy;

    2012-01-01

    Transformation Induced Plasticity (TRIP) steels have not yet been successfully joined by any welding technique. It is desirable to search for a suitable welding technique that opens up for full usability of TRIP steels. In this study, the potential of joining TRIP steel with Friction Stir Spot...... Welding (FSSW) is investigated. The aim of the study is to investigate whether acceptable welds can be produced, and additionally, to obtain an understanding of the microstructural changes during welding. The microstructure was investigated with a combination of microscopical techniques with the aim...... of identifying the transformations occurring during welding. Reflected light microscopy, scanning electron microscopy, and electron backscatter diffraction were among the methods applied for detailed investigations. The microstructure adjacent to the welds can generally be subdivided in two thermo...

  10. Comparison of fatigue property between friction stir and TIG welds

    Institute of Scientific and Technical Information of China (English)

    Xunhong Wang; Kuaishe Wang; Yang Shen; Kai Hu

    2008-01-01

    The alloy 5052 was welded by friction stir welding (FSW) and tungsten inert gas (TIG) welding. The effect of welding processes (FSW and TIG) on the fatigue properties of 5052 aluminum-welded joints was analyzed based on fatigue testing, and the S-N curve of the joints were established. The results show that the fatigue properties of FSW welded joints are better than those of TIG welded joints. The fatigue strength is determined as 65 Mpa under 106 cycling of fatigue life. The microstructure of joints is fine grains and narrow HAZ zone in FSW welds, which inhibit the growth of cracks and produce high fatigue life compared with that of TIG welds. Fracture morphologies also show that the fatigue fracture results from weld defects.

  11. Interfacial Reaction during Friction Stir Welding of Al and Cu

    Science.gov (United States)

    Genevois, C.; Girard, M.; Huneau, B.; Sauvage, X.; Racineux, G.

    2011-08-01

    Commercially pure copper was joined to a 1050 aluminum alloy by friction stir welding. A specific configuration where the tool pin was fully located in the aluminum plate was chosen. In such a situation, there is no mechanical mixing between the two materials, but frictional heating gives rise to a significant thermally activated interdiffusion at the copper/aluminum interface. This gives rise to the formation of defect-free joints where the bonding is achieved by a very thin intermetallic layer at the Cu/Al interface. Nanoscaled grains within this bonding layer were characterized using transmission electron microscopy (TEM). Two phases were identified, namely, Al2Cu and Al4Cu9 phases. The nucleation and growth of these two phases are discussed and compared to the standard reactive interdiffusion reactions between Cu and Al.

  12. Versatile Friction Stir Welding/Friction Plug Welding System

    Science.gov (United States)

    Carter, Robert

    2006-01-01

    A proposed system of tooling, machinery, and control equipment would be capable of performing any of several friction stir welding (FSW) and friction plug welding (FPW) operations. These operations would include the following: Basic FSW; FSW with automated manipulation of the length of the pin tool in real time [the so-called auto-adjustable pin-tool (APT) capability]; Self-reacting FSW (SRFSW); SR-FSW with APT capability and/or real-time adjustment of the distance between the front and back shoulders; and Friction plug welding (FPW) [more specifically, friction push plug welding] or friction pull plug welding (FPPW) to close out the keyhole of, or to repair, an FSW or SR-FSW weld. Prior FSW and FPW systems have been capable of performing one or two of these operations, but none has thus far been capable of performing all of them. The proposed system would include a common tool that would have APT capability for both basic FSW and SR-FSW. Such a tool was described in Tool for Two Types of Friction Stir Welding (MFS- 31647-1), NASA Tech Briefs, Vol. 30, No. 10 (October 2006), page 70. Going beyond what was reported in the cited previous article, the common tool could be used in conjunction with a plug welding head to perform FPW or FPPW. Alternatively, the plug welding head could be integrated, along with the common tool, into a FSW head that would be capable of all of the aforementioned FSW and FPW operations. Any FSW or FPW operation could be performed under any combination of position and/or force control.

  13. Auto-adjustable pin tool for friction stir welding

    Science.gov (United States)

    Ding, R. Jeffrey (Inventor); Oelgoetz, Peter A. (Inventor)

    1999-01-01

    An auto-adjusting pin tool for friction stir welding is presented wherein the pin tool automatically adjusts for welding materials of varying thicknesses, and the pin can be incrementally withdrawn from the workpieces thus eliminating any crater or keyhole in the weld. The inventive apparatus is comprised of a welding head housing a motor connected to a controller instrument package and an arbor supported by bearings. The arbor forms an interior cylinder and is encircled by a stationary slip ring though which are ported hydraulic passageways into the interior cylinder of the arbor such that a piston housed therein may be moved axially. Coupled to the piston is a pin tool which is treaded on its lower end and which is moveably seated in, and extending through, a shoulder housing having concave lower face. When welding, the rotating treaded end of the pin enters and stirs the workpieces while the lower face of the shoulder housing compacts the workpieces. As the welding head traverses the shoulder housing the controller senses any rising pressure on the lower face of the shoulder housing and withdraws the arbor to keep the pressure constant. At the same time, the piston moves towards the workpieces thus extending the pin further from the shoulder. This keeps the pin at a proper depth in the workpieces regardless of their thicknesses. As the weld terminates this same operation can be used to incrementally withdraw the pin during the final part of the traverse, thus eliminating any keyhole or crater that would otherwise be created.

  14. Friction stir joining of dissimilar ferritic ODS steels

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Suk Hoon; Jang, Jin Sung; Noh, Sang Hoon; Kim, Tae Kyu [Nuclear Materials Division, Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2012-10-15

    Application of the latest developments in materials technology may greatly aid in the successful pursuit of next generation reactor and transmutation technologies. Oxide dispersion strengthened (ODS) ferritic steels are expected to be used as a long life cladding in the future advanced fast reactor. Comparing to the other steels, ODS steels have excellent resistance to creep and swelling as well as superior mechanical strength. Applications of ODS steels grow faster in nuclear engineering society; however, not so many studies have been made for improving weld properties. In ODS steels, it is well known that uniform nano oxide depressed act as pinning points to obstruct dislocation and grain boundary motion, however, those advantages will be disappeared while the material is subjected to the high temperature of conventional fusion welding. Rotary friction welding, also referred to as friction stir welding (FSW), has shown great promise as a method for joining traditionally difficult to join materials such as aluminum alloys. This relatively new technology, first developed in 1991, has more recently been applied to higher melting temperature alloys such as steels, nickel-based and titanium alloys. In this study, FSW is used as a substitutive welding process for ferritic ODS steels, solid state microstructure modification is performed. During the FSW, dynamic recrystallized grains are developed; the uniform oxides dispersion is preserved in the metal matrix. The microstructure and micro texture of the material near the stir zone was found to be influenced by the rotational behavior of the tool. The response of material for different process variables have been discussed in terms of plastic deformation amount and heat input.

  15. Additional merit of coronal STIR imaging for MR imaging of lumbar spine

    Directory of Open Access Journals (Sweden)

    Ranjana Gupta

    2015-01-01

    Full Text Available Introduction: Back pain is a common clinical problem and is the frequent complaint for referral of lumbar spine magnetic resonance imaging (MRI. Coronal short tau inversion recovery sequence (STIR can provide diagnostically significant information in small percentage of patients. Materials and Methods: MRI examinations of a total of 350 patients were retrospectively included in the study. MR sequences were evaluated in two settings. One radiologist evaluated sagittal and axial images only, while another radiologist evaluated all sequences, including coronal STIR sequence. After recording the diagnoses, we compared the MRI findings in two subsets of patients to evaluate additional merit of coronal STIR imaging. Results: With addition of coronal STIR imaging, significant findings were observed in 24 subjects (6.8%. Twenty-one of these subjects were considered to be normal on other sequences and in three subjects diagnosis was changed with the addition of coronal STIR. Additional diagnoses on STIR included sacroiliitis, sacroiliac joint degenerative disease, sacral stress/insufficiency fracture/Looser′s zones, muscular sprain and atypical appendicitis. Conclusion: Coronal STIR imaging can provide additional diagnoses in a small percentage of patients presenting for lumbar spine MRI for back pain. Therefore, it should be included in the routine protocol for MR imaging of lumbar spine.

  16. Effects of cutting intensity and stirring speed on syneresis and curd losses during cheese manufacture.

    Science.gov (United States)

    Everard, C D; O'Callaghan, D J; Mateo, M J; O'Donnell, C P; Castillo, M; Payne, F A

    2008-07-01

    Recombined whole milk was renneted under constant conditions of pH, temperature, and added calcium, and the gel was cut at a constant firmness. The effects of cutting and stirring on syneresis and curd losses to whey were investigated during cheese making using a factorial design with 3 cutting modes designed to provide 3 different cutting intensity levels (i.e., total cutting revolutions), 3 levels of stirring speed, and 3 replications. These cutting intensities and stirring speeds were selected to give a wide range of curd grain sizes and curd shattering, respectively. Both factors affected curd losses, and correct selection of these factors is important in the cheesemaking industry. Decreased cutting intensity and increased stirring speed significantly increased the losses of fines and fat from the curd to the whey. Cutting intensities and stirring speeds in this study did not show significant effects on curd moisture content over the course of syneresis. Levels of total solids, fines, and fat in whey were shown to change significantly during syneresis. It is believed that larger curd particles resulting from low cutting intensities coupled with faster stirring speeds resulted in a higher degree of curd shattering during stirring, which caused significant curd losses.

  17. Design and evaluation of improved magnetic stir bars for single-mode microwave reactors.

    Science.gov (United States)

    Obermayer, David; Damm, Markus; Kappe, C Oliver

    2013-08-14

    Magnetic stirring in sealed cylindrical vessels designed for use in single-mode microwave instruments is typically less than optimal, and is not comparable to the efficient agitation that can be generally obtained in a round-bottomed flask fitted with a suitable magnetic stir bar or using overhead mechanical stirring systems. A new "vertical blade" stir bar design that improves the stirring performance in the very narrow, flow-constricting microwave vessels has been developed and evaluated for several different transformations where stirring and efficient agitation are known to be of importance. The better performance of these novel stirrers compared to the traditional cylindrical stir bar design is not only due to the geometry of the stirrer but also to the utilization of a magnetic material with a stronger magnetic transmission force (Sm2Co17) compared to standard ferrite or AlNiCo alloys. For all three tested cases involving solid/liquid, liquid/liquid and highly viscous reaction systems, the new vertical blade stirrers showed a distinctively improved performance resulting in higher conversions and/or product yields. PMID:23797332

  18. Physical Simulation of a Duplex Stainless Steel Friction Stir Welding by the Numerical and Experimental Analysis of Hot Torsion Tests

    Science.gov (United States)

    da Fonseca, Eduardo Bertoni; Santos, Tiago Felipe Abreu; Button, Sergio Tonini; Ramirez, Antonio Jose

    2016-07-01

    Physical simulation of friction stir welding (FSW) by means of hot torsion tests was performed on UNS S32205 duplex stainless steel. A thermomechanical simulator Gleeble 3800® with a custom-built liquid nitrogen cooling system was employed to reproduce the thermal cycle measured during FSW and carry out the torsion tests. Microstructures were compared by means of light optical microscopy and electron backscatter diffraction. True strain and strain rate were calculated by numerical simulation of the torsion tests. Thermomechanically affected zone (TMAZ) was reproduced at peak temperature of 1303 K (1030 °C), rotational speeds of 52.4 rad s-1 (500 rpm) and 74.5 rad s-1 (750 rpm), and 0.5 to 0.75 revolutions, which represent strain rate between 10 and 16 s-1 and true strain between 0.5 and 0.8. Strong grain refinement, similar to the one observed in the stir zone (SZ), was attained at peak temperature of 1403 K (1130 °C), rotational speed of 74.5 rad s-1 (750 rpm), and 1.2 revolution, which represent strain rate of 19 s-1 and true strain of 1.3. Continuous dynamic recrystallization in ferrite and dynamic recrystallization in austenite were observed in the TMAZ simulation. At higher temperature, dynamic recovery of austenite was also observed.

  19. Physical Simulation of a Duplex Stainless Steel Friction Stir Welding by the Numerical and Experimental Analysis of Hot Torsion Tests

    Science.gov (United States)

    da Fonseca, Eduardo Bertoni; Santos, Tiago Felipe Abreu; Button, Sergio Tonini; Ramirez, Antonio Jose

    2016-09-01

    Physical simulation of friction stir welding (FSW) by means of hot torsion tests was performed on UNS S32205 duplex stainless steel. A thermomechanical simulator Gleeble 3800® with a custom-built liquid nitrogen cooling system was employed to reproduce the thermal cycle measured during FSW and carry out the torsion tests. Microstructures were compared by means of light optical microscopy and electron backscatter diffraction. True strain and strain rate were calculated by numerical simulation of the torsion tests. Thermomechanically affected zone (TMAZ) was reproduced at peak temperature of 1303 K (1030 °C), rotational speeds of 52.4 rad s-1 (500 rpm) and 74.5 rad s-1 (750 rpm), and 0.5 to 0.75 revolutions, which represent strain rate between 10 and 16 s-1 and true strain between 0.5 and 0.8. Strong grain refinement, similar to the one observed in the stir zone (SZ), was attained at peak temperature of 1403 K (1130 °C), rotational speed of 74.5 rad s-1 (750 rpm), and 1.2 revolution, which represent strain rate of 19 s-1 and true strain of 1.3. Continuous dynamic recrystallization in ferrite and dynamic recrystallization in austenite were observed in the TMAZ simulation. At higher temperature, dynamic recovery of austenite was also observed.

  20. Business continuity

    International Nuclear Information System (INIS)

    This presentation deals with the following keypoints: Information Technology (IT) Business Continuity and Recovery essential for any business; lessons learned after Sept. 11 event; Detailed planning, redundancy and testing being the key elements for probability estimation of disasters

  1. Continuing Care

    Science.gov (United States)

    ... Care Obesity at Midlife May Speed Alzheimer’s Onset Hello from my mom Easing the Behavior Problems of ... Managers Continuing Care FOR MORE ARTICLES CLICK HERE Hello from my mom Common Estate Planning Errors Alzheimer’s ...

  2. Analysis of Mixing Characteristics of Batch Stirred Vessels Using the Networks-of-Zones Model

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Batch stirred vessels, being devoid of through flow, cannot be assessed by the classical response technique. However, visible inert tracers can be readily observed in a batch or semi-batch stirred vessel. Visible images of the mixing and dispersion of the tracer present a picture in both space and time of the mixing process. Axi-symmetric networks of backmixed zones were used in an image reconstruction approach to analytically characterize the mixing. Computer generated images were compared with experimental results. The qualitative agreement between the observed and calculated images suggests that the analysis of batch stirred reactors can be used to guide operational strategies to control internal concentration fields.

  3. Grain refinement of AZ31 magnesium alloy by electromagnetic stirring under effect of grain-refiner

    Indian Academy of Sciences (India)

    S Y Gao; Q C Le; Z Q Zhang; J Z Cui

    2012-08-01

    The effects of electromagnetic stirring and Al4C3 grain refiner on the grain refinement of semicontinuously cast AZ31 magnesium alloy were discussed in this investigation. The results indicate that electromagnetic stirring has an effective refining effect on the grain size of AZ31 magnesium alloy under the effect of Al4C3 grain refiner. Electromagnetic stirring can `activate’ the Al4C3 particles, resulting in more heterogeneous nucleation sites for the primary -Mg grains. But, longer holding time can `deactivate’ the Al4C3 particles and poison the grain refining effect.

  4. Effect of cooling rate on microstructure of friction-stir welded AA1100 aluminum alloy

    Science.gov (United States)

    Yi, D.; Mironov, S.; Sato, Y. S.; Kokawa, H.

    2016-06-01

    In this work, the microstructural changes occurring during cooling of friction-stir welded aluminum alloy AA1100 were evaluated. To this end, friction-stir welding (FSW) was performed in a wide range of cooling rates of 20-62 K/s and the evolved microstructures were studied by using electron backscatter diffraction. Below 0.6 Tm (Tm being the melting point), the stir zone material was found to experience no significant changes during cooling. At higher FSW temperatures, however, notable changes occurred in the welded material, including grain growth, sharpening of texture, reduction of the fraction of high-angle boundaries and material softening.

  5. Ultrasonic-assisted friction stir welding on V95AT1 (7075) aluminum alloy

    Science.gov (United States)

    Tarasov, S. Yu.; Rubtsov, V. Ye.; Kolubaev, E. A.; Ivanov, A. N.; Fortuna, S. V.; Eliseev, A. A.

    2015-10-01

    Ultrasonic-assisted friction stir butt welding on aluminum alloy V95AT1 (7075) has been carried out. Samples have been characterized using metallography, microhardness and XRD. As shown, ultrasonic treatment during welding provides extra plasticizing of metal and better stirring efficiency. The latter serves for elimination of defects, such as root flaw and grain refining in the stir zone. The stress state in the welded joint is characterized by tensile stress in the direction of the weld seam centerline and compression in the transversal direction. The ultrasonic treatment was shown to increase the compression stress and relieve the tensile one.

  6. Effects of Fusion Tack Welds on Self-Reacting Friction Stir Welds

    Science.gov (United States)

    Nunes, A. C., Jr.; Pendleton, M. L.; Brooke, S. A.; Russell, C. K.

    2012-01-01

    In order to know whether fusion tack welds would affect the strength of self-reacting friction stir seam welds in 2195-T87 aluminum alloy, the fracture stresses of 144 tensile test coupons cut from 24 welded panels containing segments of friction stir welds were measured. Each of the panels was welded under unique processing conditions. A measure of the effect of the tack welds for each panel was devised. An analysis of the measures of the tack weld effect supported the hypothesis that fusion tack welds do not affect the strength of self-reacting friction stir welds to a 5% level of confidence.

  7. Optimization of Friction Stir Welding Tool Advance Speed via Monte-Carlo Simulation of the Friction Stir Welding Process

    Directory of Open Access Journals (Sweden)

    Kirk A. Fraser

    2014-04-01

    Full Text Available Recognition of the friction stir welding process is growing in the aeronautical and aero-space industries. To make the process more available to the structural fabrication industry (buildings and bridges, being able to model the process to determine the highest speed of advance possible that will not cause unwanted welding defects is desirable. A numerical solution to the transient two-dimensional heat diffusion equation for the friction stir welding process is presented. A non-linear heat generation term based on an arbitrary piecewise linear model of friction as a function of temperature is used. The solution is used to solve for the temperature distribution in the Al 6061-T6 work pieces. The finite difference solution of the non-linear problem is used to perform a Monte-Carlo simulation (MCS. A polynomial response surface (maximum welding temperature as a function of advancing and rotational speed is constructed from the MCS results. The response surface is used to determine the optimum tool speed of advance and rotational speed. The exterior penalty method is used to find the highest speed of advance and the associated rotational speed of the tool for the FSW process considered. We show that good agreement with experimental optimization work is possible with this simplified model. Using our approach an optimal weld pitch of 0.52 mm/rev is obtained for 3.18 mm thick AA6061-T6 plate. Our method provides an estimate of the optimal welding parameters in less than 30 min of calculation time.

  8. Texture Analyses of Ti/Al2O3 Nanocomposite Produced Using Friction Stir Processing

    Science.gov (United States)

    Shafiei-Zarghani, Aziz; Kashani-Bozorg, Seyed Farshid; Gerlich, Adrian P.

    2016-08-01

    The texture evolution of Ti/Al2O3 nanocomposite fabricated using friction stir processing (FSP) was investigated at both macroscopic and microscopic levels employing X-ray diffraction and electron backscattering diffraction techniques. The developed textures were compared with ideal shear textures of hexagonal close-packed (hcp) structure, revealing that the fabricated nanocomposite is dominated by the P 1 hcp (fiber { 10bar{1}1} textures. The analyses of macro- and microtextures showed that the presence of nanosized Al2O3 particles activated the pyramidal { 10bar{1}1} < bar{1}bar{1}23rangle slip system in addition to dominant { 10bar{1}0} < 1bar{2}10rangle prism, basal { {0002} }< 1bar{2}10rangle, and pyramidal { 10bar{1}1} < 1bar{2}10rangle slip systems which normally govern plastic deformation during FSP of commercially pure titanium alloy. Moreover, the presence of nanoparticles promoted the occurrence of continuous dynamic recrystallization as well as increasing the fraction of high-angle grain boundaries within the developed microstructure.

  9. Stationary-state and oscillatory combustion of hydrogen in a well-stirred flow reactor

    Energy Technology Data Exchange (ETDEWEB)

    Baulch, D.L.; Griffiths, J.F.; Pappin, A.J.; Sykes, A.F.

    1988-08-01

    The existence of stationary-state and oscillatory ignition phenomena is established in hydrogen oxidation in a jet-stirred, Pyrex glass reactor (0.55 dm/sup 3/). The experimental observations and their numerical interpretation from a detailed kinetic mechanism are reported. Compositions containing 2H/sub 2/ + O/sub 2/, H/sub 2/ + O/sub 2/, and H/sub 2/ + 2O/sub 2/ were investigated at total pressures mainly in the range 10-20 Torr, with brief excursions up to 80 Torr. The vessel temperature was varied between 670 and 790K and mean residence times were controlled in the range 0.7-8.0 s. Reactant temperatures were measured using a very fine thermocouple in the vessel and light output was monitored by photomultiplier. The experimental conditions straddle events at the second limit. Thus criticality and ignition occurs as the vessel temperature is raised under continuous flow of reactants. Ignition is an oscillatory phenomenon at low pressures, and adiabatic temperature changes occur momentarily during it. Increases of vessel temperature cause oscillatory amplitudes to fall and their frequencies to rise. Eventually the oscillations dwindle to a stable stationary state. In certain circumstances there can be an abrupt transition from low frequency to high frequency oscillations. Detailed investigations show that there can be reaction multiplicity and even birhythmicity in the vicinity of these transition points. The dependences of oscillatory reaction on pressure, temperature, and composition are investigated.

  10. Fluid Flow Behavior of Liquid in Cylindrical Vessels Stirred by One or Two Air Jets

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Based on the two-phase model (Eulerian-Eulerian model), the three dimensional fluid flow in water and that liquid steel systems stirred by one or two multiple gas jets are simulated. In the Eulerian-Eulerian two-phase model, the gas and the liquid phase are considered to be two different continuous fluids interacting with each other through the finite inter-phase areas. The exchange between the phases is represented by source terms in conversation equations. Turbulence is assumed to be a property of the liquid phase. A new turbulence modification - model is introduced to consider the bubbles movement contribution to and . The dispersion of phases due to turbulence is represented by introducing a diffusion term in mass conservation equation. The mathematical simulation agrees well with the experiment results. The study results indicate that the distance of two nozzles has big effect on fluid flow behavior in the vessel. Using two gas injection nozzles at the half radii of one diameter of the bottom generates a much better mixing than with one nozzle under the condition of the same total gas flow rate.

  11. Liquation Cracking in Arc and Friction-Stir Welding of Mg-Zn Alloys

    Science.gov (United States)

    Wagner, Dustin C.; Chai, Xiao; Tang, Xin; Kou, Sindo

    2015-01-01

    As compared to Al alloys, which are known to be susceptible to liquation ( i.e., liquid formation) and liquation-induced cracking, most Mg alloys have a lower eutectic temperature and thus are likely to be even more susceptible. The present study was conducted to study liquation and liquation cracking in Mg alloys during arc welding and friction-stir welding (FSW). Binary Mg-Zn alloys were selected as a model material in view of their very low eutectic temperature of 613 K (340 °C). Mg-Zn alloys with 2, 4, and 6 wt pct of Zn were cast and welded in the as-cast condition by both gas-tungsten arc welding (GTAW) and FSW. A simple test for liquation cracking was developed, which avoided interference by solidification cracking in the nearby fusion zone. Liquation and liquation cracking in GTAW were found to be in the decreasing order of Mg-6Zn, Mg-4Zn, and Mg-2Zn. Liquation cracking occurred in FSW of Mg-6Zn but not Mg-4Zn or Mg-2Zn. Instead of a continuous ribbon-like flash connected to the weld edge, small chips, and powder covered the weld surface of Mg-6Zn. The results from GTAW and FSW were discussed in light of the binary Mg-Zn phase diagram and the curves of temperature vs fraction solid during solidification.

  12. Continuity theory

    CERN Document Server

    Nel, Louis

    2016-01-01

    This book presents a detailed, self-contained theory of continuous mappings. It is mainly addressed to students who have already studied these mappings in the setting of metric spaces, as well as multidimensional differential calculus. The needed background facts about sets, metric spaces and linear algebra are developed in detail, so as to provide a seamless transition between students' previous studies and new material. In view of its many novel features, this book will be of interest also to mature readers who have studied continuous mappings from the subject's classical texts and wish to become acquainted with a new approach. The theory of continuous mappings serves as infrastructure for more specialized mathematical theories like differential equations, integral equations, operator theory, dynamical systems, global analysis, topological groups, topological rings and many more. In light of the centrality of the topic, a book of this kind fits a variety of applications, especially those that contribute to ...

  13. Counterrotating-Shoulder Mechanism for Friction Stir Welding

    Science.gov (United States)

    Nunes, Arthur C., Jr.

    2007-01-01

    A counterrotating-shoulder mechanism has been proposed as an alternative to the mechanism and fixtures used in conventional friction stir welding. The mechanism would internally react most or all of the forces and torques exerted on the workpiece, making it unnecessary to react the forces and torques through massive external fixtures. In conventional friction stir welding, a rotating pin tool is inserted into, and moved along, a weld seam. As the pin tool moves, it stirs together material from the opposite sides of the seam to form the weld. A large axial plunge force must be exerted upon the workpiece through and by the pin tool and a shoulder attached above the pin tool in order to maintain the pressure necessary for the process. The workpiece is secured on top of an anvil, which supports the workpiece against the axial plunge force and against the torque exerted by the pin tool and shoulder. The anvil and associated fixtures must be made heavy (and, therefore, are expensive) to keep the workpiece stationary. In addition, workpiece geometries must be limited to those that can be accommodated by the fixtures. The predecessor of the proposed counterrotating-shoulder mechanism is a second-generation, self-reacting tool, resembling a bobbin, that makes it possible to dispense with the heavy anvil. This tool consists essentially of a rotating pin tool with opposing shoulders. Although the opposing shoulders maintain the necessary pressure without need to externally apply or react a large plunge force, the torque exerted on the workpiece remains unreacted in the absence of a substantial external fixture. Depending on the RPM and the thickness of the workpiece, the torque can be large. The proposed mechanism (see figure) would include a spindle attached to a pin tool with a lower shoulder. The spindle would be coupled via splines to the upper one of three bevel gears in a differential drive. The middle bevel gear would be the power-input gear and would be coupled to the

  14. Thermal Stir Welding of High Strength and High Temperature Alloys for Aerospace Applications Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The Keystone and MSU team propose to demonstrate the feasibility of solid-state joining high strength and temperature alloys utilizing the Thermal Stir Welding...

  15. Equipment for Solid State Stir Welding of High Temperature Materials Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Stir welding generates high-quality joints in fabricated structure and is the baseline joining process for most NASA aluminum alloy structures such as cryogenic...

  16. Improvement of lipase production at different stirring speeds and oxygen levels

    Directory of Open Access Journals (Sweden)

    F.O.M. Alonso

    2005-03-01

    Full Text Available Lipase production by a Brazilian wild strain of Yarrowia lipolytica at different stirring speeds and air flow rates was studied. The relationship among lipid consumption, cell growth and lipase production by this microorganism is presented. The most pronounced effect of oxygen on lipase production was determined by stirring speed. Maximum lipase activity was detected in the late stationary phase at 200 rpm and an air flow rate of 1-2 dm³/min (0.8-1.7 vvm when the lipid source had been fully consumed. Higher stirring speeds resulted in mechanical and/or oxidative stress, while lower stirring speeds seemed to limit oxygen levels. An increase in the availability of oxygen at higher air flow rates led to faster lipid uptake and anticipation of enzyme release into the culture medium. The highest lipase production was obtained at 200 rpm and 1 dm³/min (0.8 vvm.

  17. The Analysis of a Vibrator Oil-stirring Phnomenon and Study on a New Structure

    Institute of Scientific and Technical Information of China (English)

    HAN Bing-bing; ZHANG Gong-xue

    2012-01-01

    The deep vibrator is an important equipment of foundation improvement. It works through eccentric masses with high-speed. But the traditional eccentric structure will stir the oil around it, and it will result in the loss of motor power. The paper analyzed the stirring phenomenon, and got the level and specific data of stirring and swirling through fluent software. After principle analysis, a new type of anti-churning eccentric structure was put forward, which can effectively avoid stirring phenomenon. Otherwise, the new structure will also not produce irregular vibration because of swirling, then it can work with a better performance. In addition, the contrast of dynamic performance between a traditional and new structure was carried out in the paper and proved that the new structure has a better working performance. Modeling data in the paper is from surveying and mapping, so the conclusion can be taken as guidance for vibrator designing.

  18. Nonlinear Time Reversal Acoustic Method of Friction Stir Weld Assessment Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The goal of the project is demonstration of the feasibility of Friction Stir Weld (FSW) assessment by novel Nonlinear Time Reversal Acoustic (TRA) method. Time...

  19. Continuity check

    Energy Technology Data Exchange (ETDEWEB)

    Woof, M.

    2002-10-01

    This paper looks into both safety and technological developments in continuous mining. Manufacturers covered include Hydraphase, Eimco, Deilmann-Haniel, DBT and Joy. A recent Health and Safety Executive report mentioned three in incidents of frictional ignition of flammable gas by cutting equipment in a five year period to April 1999. 4 photos.

  20. Simulation of the Effectiveness of Dynamic Cooling for Controlling Residual Stresses in Friction Stir Welds

    OpenAIRE

    D.G. Richards, P.B. Prangnell, P.J. Withers, S.W. Williams, A. Wescott, E.C Oliver

    2008-01-01

    An FE model has been used to study the effect of localised dynamic cooling on the residual stresses developed during friction stir welding. The main aim of the work was to see if the cooling power and source positions required, to achieve significant residual stress reductions in friction stir welds, were compatible with the FSW process and recent developments in CO2 cooling systems. Comparisons were made between welds produced with a single cold spot placed over the weld line, either ahead o...

  1. Numerical simulation of material flow in AA6082 during friction stir spot welding

    OpenAIRE

    Gao, Zeng; Wang, Peng; CHENG, DONGFENG; Niu, Jitai; Sommitsch, Christof

    2015-01-01

    Friction stir spot welding (FSSW) is a new solid state joining technology based on the linear friction stir welding which can be used to replace the conventional resistance spot welding as well as riveting. However, some key problems such as heat transfer and thermoplastic material flow have not yet been studied sufficiently and block the application of this advanced technology. This paper presents the coupled thermo-mechanical viscoplastic finite element formulation based on the character of...

  2. Friction Stir Spot Welding: A Review on Joint Macro- and Microstructure, Property, and Process Modelling

    OpenAIRE

    Yang, X.W.; Fu, T; Li, W. Y.

    2014-01-01

    Friction stir spot welding (FSSW) is a very useful variant of the conventional friction stir welding (FSW), which shows great potential to be a replacement of single-point joining processes like resistance spot welding and riveting. There have been many reports and some industrial applications about FSSW. Based on the open literatures, the process features and variants, macro- and microstructural characteristics, and mechanical properties of the resultant joints and numerical simulations of t...

  3. Effect of tool geometry on friction stir spot welding of polypropylene sheets

    OpenAIRE

    M. K. Bilici

    2012-01-01

    The effects of tool geometry and properties on friction stir spot welding properties of polypropylene sheets were studied. Four different tool pin geometries, with varying pin angles, pin lengths, shoulder diameters and shoulder angles were used for friction stir spot welding. All the welding operations were done at the room temperature. Lap-shear tensile tests were carried out to find the weld static strength. Weld cross section appearance observations were also done. From the experiments th...

  4. Effect of process parameters on mechanical properties of friction stir spot welded magnesium to aluminum alloys

    International Nuclear Information System (INIS)

    Highlights: • Lap-shear failure load of ∼2.5 kN was achieved in dissimilar Mg to Al spot welds. • Failure load depends on both welding geometrical features and IMCs formation. • Thin and discontinuous IMCs formed in stir zone are beneficial for weld strength. • Low heat input and good material mixing/interlocking is essential for high strength. - Abstract: Friction stir spot welding was applied to dissimilar cast magnesium (Mg) alloy AM60B and wrought aluminum (Al) alloy 6022-T4 under various welding conditions. The influence of tool rotation rate and shoulder plunge depth on lap-shear failure load was examined. Welds were made at four different tool rotation rates of 1000, 1500, 2000 and 2500 revolution per minute (rpm) and various tool shoulder plunge depths from 0 mm to 0.9 mm. The cross section of each weld exhibited the formation of intermetallic compounds (IMCs) in the stir zone. An increase in tool rotation rate decreased the width of the stir zone and resulted in lower lap-shear failure loads. The stir zone width increased and interlocking of IMCs was observed with an increase in tool shoulder plunge depth at 1000 rpm. High lap-shear failure loads were achieved in welds having a large stir zone width with formation of discontinuous IMCs at the tip of the interfacial hook. An average lap-shear failure load of 2.5 kN was achieved for welds made at 1000 rpm and 0.9 mm shoulder plunge. The present study suggests that the mechanical properties of friction stir spot welded dissimilar alloys are greatly influenced by the stir zone width, interfacial hooks and IMCs which are all weld process dependent

  5. Investigation on the Joinability of Al 6061 Al-Alloy Plates with Friction Stir Welding

    OpenAIRE

    İlker EKER; SEVİM, İbrahim

    2009-01-01

    In this study, the microhardness and mechanical properties of welding zones of cast aluminum sheets welded by friction stir welding method have been examined with variable parameters. During welding, rotational speed of the welding stir tool and welding speed were chosen as the variable parameters. A welding tool made of case hardened steel (material number being SAE 8620) was employed in the welding of aluminum plates. Four different welding speeds are considered at constant rotational speed...

  6. Friction Stir.Welding is an advance metal joining process: A Review

    OpenAIRE

    Umasankar Das,; Dr. Vijay Toppo

    2015-01-01

    The friction stir welding is recently developed solid state welding process which overcome the problem associated with fusion welding technology. The properties achieved by friction stir welding is better than that achieve by fusion welding technique It has been invented as a solid-state joining technique and initially applied to aluminum alloys. FSW is used to replace rivets joints in the aeronautical industry. Recently the aircraft and military industries widely have been using ...

  7. Corrosion Behaviour of Friction Stir Welded AA5xxx Aluminium Alloys

    OpenAIRE

    Abuaisha, Ramadan R

    2013-01-01

    Friction stir welding (FSW) is a well recognised method for joining aluminium alloys and other engineering materials at a temperature below their melting point. However, the microstructure of the alloys may be modified during the welding process due to frictional heat and severe plastic deformation.In this study, the microstructures of friction stir welded AA5754-H111 and AA5083-O aluminium alloys have been investigated using optical microscopy, transmission and scanning electron microscopy e...

  8. Effect of processing parameters on the corrosion behaviour of friction stir processed AA 2219 aluminum alloy

    Science.gov (United States)

    Surekha, K.; Murty, B. S.; Prasad Rao, K.

    2009-04-01

    The effect of processing parameters (rotation speed and traverse speed) on the corrosion behaviour of friction stir processed high strength precipitation hardenable AA 2219-T87 alloy was investigated. The results indicate that the rotation speed has a major influence in determining the rate of corrosion, which is attributed to the breaking down and dissolution of the intermetallic particles. Corrosion resistance of friction stir processed alloy was studied by potentiodynamic polarization, electrochemical impedance spectroscopy, salt spray and immersion tests.

  9. Composite Aluminum-Copper Sheet Material by Friction Stir Welding and Cold Rolling

    OpenAIRE

    Kahl, S.; Osikowicz, W.

    2013-01-01

    An aluminum alloy and a pure copper material were butt-joined by friction stir welding and subsequently cold rolled. The cold-rolling operation proved to be very advantageous because small voids present after friction stir welding were closed, the interface area per material thickness was enlarged, a thin intermetallic layer was partitioned, and the joint was strengthened by strain hardening. Tensile test specimens fractured in the heat-affected zone in the aluminum material; tensile strength...

  10. STUDY ON THE TEXTURE OF A FRICTION STIR WELDED Mg-Al-Ca ALLOY

    Institute of Scientific and Technical Information of China (English)

    D.T. Zhang; M. Suzuki; K. Maruyama

    2006-01-01

    Macro-texture of an Mg-Al-Ca alloy prepared by friction stir welding (FSW) was investigated through pole figure measurement and X-ray diffraction (XRD) pattern analysis. It was found that at the top and bottom surfaces of friction stir zone (FSZ), (0002) basal planes of magnesium tend to be arranged parallel to the plate surface. In the cross section of FSZ, no obvious texture had evolved and (0002) basal planes showed a random distribution.

  11. Strain Rates and Grain Growth in Al 5754 and Al 6061 Friction Stir Spot Welds

    Science.gov (United States)

    Gerlich, A.; Yamamoto, M.; North, T. H.

    2007-06-01

    The stir zone temperature and microstructures are compared in friction stir spot welds produced in Al 5754 and Al 6061 alloys. Electron backscattered diffraction was used to determine the relationship between tool rotation speed during welding and final stir zone grain size. Comparison of the grain sizes in rapidly quenched welds with those in air-cooled joints confirmed that grain growth occurred only in Al 6061 spot welds. There was no evidence of abnormal grain growth in the stir zones of Al 6061 welds; the final grain size could be represented using an Arrhenius equation. The strain rates during welding were determined by incorporating the stir zone temperature and average subgrain sizes in quenched spot welds in the Zener-Hollomon relation. When the tool rotation speed increased from 750 to 3000 RPM, the strain rate values ranged from 180 to 497 s-1 in Al 5754 spot welds and from 55 to 395 s-1 in Al 6061 spot welds. It is suggested that a no-slip boundary condition may be appropriate during numerical modeling of Al 5754 and 6061 friction stir spot welding. This is not the case during Al 7075, Al 2024, and Mg-alloy AZ91 spot welding because spontaneous melting facilitates slippage at the tool contact interface.

  12. Microstructural formation of semi-solid AZ91D alloy stirred by electromagnetic field

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    With the help of an electromagnetic stirring device, alloy melt quenching and EBSD (electron back scatter diffraction)analysis technology, the microstructure of the semi-solid AZ91D magnesium alloy slurry stirred by rotational electromagnetic field under different stirring power conditions has been studied. The results show that the size of primary α-Mg phase is reduced obviously when the solidifying alloy melt is stirred by rotational electromagnetic field, moreover, the primary α-Mg grains are changed to fine rosette grains or spherical grains which are proved to belong to the different grains in three-dimension by the EBSD analysis technology. The results also show that the stirring power is an important processing parameter in the preparation of the semi-solid AZ91D magnesium alloy slurry. The larger the stirring power, the finer the primary α-Mg grains, the less the rosette primary α-Mg grains, and the more the spherical primary α-Mg grains. Theoretical analysis indicates that a stronger flow motion leads to a more even temperature field and solute field and a stronger man-made temperature fluctuation in the alloy melt so that the specially fine rosette and/or spherical primary α-Mg grains are formed in the semi-solid AZ91D magnesium alloy slurry.

  13. Experimental Study on Aqueous Phase Entrainment in a Mixer-settler with Double Stirring Mode

    Institute of Scientific and Technical Information of China (English)

    Wang Shuchan; Zhang Tingan; Zhao Qiuyue; Liu Yan; Wu Qiuyang

    2013-01-01

    The mixer-settler is a core device of solvent extraction for separating rare earth elements. There are some adverse effects like high rare earth accumulation and poor production efifciency during industrial production. Current researches usually focus on changing the structure of the mixer-settler without making a breakthrough towards gravity clariifcation. In this paper, in order to improve the efifciency of clariifcation, a mixer-settler with double stirring mode was designed and manufactured by adding a stirring device in the settler after reducing the volume of the settler. The innovation of this research involves adopting the ultraviolet-visible spectrophotometer to investigate the quantity of aqueous phase entrainment at the settler outlet in order to measure the clariifcation degree. Experimental results show that the clariifcation effect with stirring is better than that without stirring. The clariifcation effect is ameliorated as the stirring speed increases. Generally, the clariifcation effect shows a best condition when the offset distance is 12.5 cm, making the phase entrainment reduced to less than 0.1%. When the clearance over the tank bottom is 7 cm and 10 cm, respectively, the quantity of aqueous phase entrainment is better than the case with a clearance of 4 cm. The results show that the stirring paddle close to the mixed phase zone can better promote the two-phase separation.

  14. Friction stir welding of F82H steel for fusion applications

    Science.gov (United States)

    Noh, Sanghoon; Ando, Masami; Tanigawa, Hiroyasu; Fujii, Hidetoshi; Kimura, Akihiko

    2016-09-01

    In the present study, friction stir welding was employed to join F82H steels and develop a potential joining technique for a reduced activation ferritic/martensitic steel. The microstructures and mechanical properties on the joint region were investigated to evaluate the applicability of friction stir welding. F82H steel sheets were successfully butt-joined with various welding parameters. In welding conditions, 100 rpm and 100 mm/min, the stirred zone represented a comparable hardness distribution with a base metal. Stirred zone induced by 100 rpm reserved uniformly distributed precipitates and very fine ferritic grains, whereas the base metal showed a typical tempered martensite with precipitates on the prior austenite grain boundary and lath boundary. Although the tensile strength was decreased at 550 °C, the stirred zone treated at 100 rpm showed comparable tensile behavior with base metal up to 500 °C. Therefore, friction stir welding is considered a potential welding method to preserve the precipitates of F82H steel.

  15. Microstructural characterizations and mechanical properties in underwater friction stir welding of aluminum and magnesium dissimilar alloys

    International Nuclear Information System (INIS)

    Highlights: • Aluminum and magnesium alloys were joined by underwater friction stir welding. • Underwater FSW was conducted to improve properties of joint with lower heat input. • Microstructures and mechanical properties of dissimilar joint were investigated. • Intermetallic compounds developed in the fracture interface were analyzed. • Fracture features of the tensile samples were analyzed. - Abstract: Formation of intermetallic compounds in the stir zone of dissimilar welds affects the mechanical properties of the joints significantly. In order to reduce heat input and control the amount and morphological characteristics of brittle intermetallic compounds underwater friction stir welding of 6013 Al alloy and AZ31 Mg alloy was carried out. Microstructures, mechanical properties, elements distribution, and the fracture surface of the joints were analyzed by optical microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy, etc. The result shows that sound dissimilar joint with good mechanical properties can be obtained by underwater friction stir welding. Al and Mg alloys were stirred together and undergone the process of recrystallization, forming complex intercalated flow patterns in the stir zone. Tensile strength of the dissimilar joint was up to 152.3 MPa. Maximum hardness (142HV) appeared in the middle of the centerline of the specimen. Intermetallic compounds layer consisting of Al3Mg2 and Mg17Al12 formed in the Al/Mg interface and resulted in the fracture of the joint

  16. Effects of stir-fry cooking with different edible oils on the phytochemical composition of broccoli.

    Science.gov (United States)

    Moreno, Diego A; López-Berenguer, Carmen; García-Viguera, Cristina

    2007-01-01

    Numerous epidemiological studies indicate that Brassica vegetables in general and broccoli in particular protect humans against cancer; they are rich sources of glucosinolates and possess a high content on flavonoids, vitamins, and mineral nutrients. The contents of total intact glucosinolates, total phenolics, vitamin C, and minerals (potassium, sodium, calcium, magnesium, iron, manganese, zinc, and copper) in the edible portions of freshly harvested broccoli (florets), which was subjected to stir-frying treatments, were evaluated. In the present work, the stir-fry cooking experiments were carried out using different edible oils from plant origin (refined olive oil, extra virgin olive oil, sunflower oil, peanut oil, soyabean oil, and safflower oil) known and used worldwide. Results showed that during stir-frying, phenolics and vitamin C were more affected than glucosinolates and minerals. Stir-fry cooking with extra virgin olive, soybean, peanut, or safflower oil did not reduce the total glucosinolate content of the cooked broccoli compared with that of the uncooked sample. The vitamin C content of broccoli stir-fried with extra virgin olive or sunflower oil was similar to that of the uncooked sample, but greater than those samples stir-fried with other oils. PMID:17995900

  17. Full-Scale Continuous Mini-Reactor Setup for Heterogeneous Grignard Alkylation of a Pharmaceutical Intermediate

    DEFF Research Database (Denmark)

    Pedersen, Michael Jønch; Holm, Thomas; Rahbek, Jesper P.;

    2013-01-01

    A reactor setup consisting of two reactors in series has been implemented for a full-scale, heterogeneous Grignard alkylation. Solutions pass from a small filter reactor into a static mixer reactor with multiple side entries, thus combining continuous stirred tank reactor (CSTR) and plug flow...

  18. Continuation calculus

    Directory of Open Access Journals (Sweden)

    Bram Geron

    2013-09-01

    Full Text Available Programs with control are usually modeled using lambda calculus extended with control operators. Instead of modifying lambda calculus, we consider a different model of computation. We introduce continuation calculus, or CC, a deterministic model of computation that is evaluated using only head reduction, and argue that it is suitable for modeling programs with control. It is demonstrated how to define programs, specify them, and prove them correct. This is shown in detail by presenting in CC a list multiplication program that prematurely returns when it encounters a zero. The correctness proof includes termination of the program. In continuation calculus we can model both call-by-name and call-by-value. In addition, call-by-name functions can be applied to call-by-value results, and conversely.

  19. A coupled thermo-mechanical model of friction stir welding

    Directory of Open Access Journals (Sweden)

    Veljić Darko M.

    2012-01-01

    Full Text Available A coupled thermo-mechanical model was developed to study the temperature fields, the plunge force and the plastic deformations of Al alloy 2024-T351 under different rotating speed: 350, 400 and 450 rpm, during the friction stir welding (FSW process. Three-dimensional FE model has been developed in ABAQUS/Explicit using the arbitrary Lagrangian-Eulerian formulation, the Johnson-Cook material law and the Coulomb’s Law of friction. Numerical results indicate that the maximum temperature in the FSW process is lower than the melting point of the welding material. The temperature filed is approximately symmetrical along the welding line. A lower plastic strain region can be found near the welding tool in the trailing side on the bottom surface. With increasing rotation speed, the low plastic strain region is reduced. When the rotational speed is increased, the plunge force can be reduced. Regions with high equivalent plastic strains are observed which correspond to the nugget and the flow arm.

  20. Friction Stir Additive Manufacturing: Route to High Structural Performance

    Science.gov (United States)

    Palanivel, S.; Sidhar, H.; Mishra, R. S.

    2015-03-01

    Aerospace and automotive industries provide the next big opportunities for additive manufacturing. Currently, the additive industry is confronted with four major challenges that have been identified in this article. These challenges need to be addressed for the additive technologies to march into new frontiers and create additional markets. Specific potential success in the transportation sectors is dependent on the ability to manufacture complicated structures with high performance. Most of the techniques used for metal-based additive manufacturing are fusion based because of their ability to fulfill the computer-aided design to component vision. Although these techniques aid in fabrication of complex shapes, achieving high structural performance is a key problem due to the liquid-solid phase transformation. In this article, friction stir additive manufacturing (FSAM) is shown as a potential solid-state process for attaining high-performance lightweight alloys for simpler geometrical applications. To illustrate FSAM as a high-performance route, manufactured builds of Mg-4Y-3Nd and AA5083 are shown as examples. In the Mg-based alloy, an average hardness of 120 HV was achieved in the built structure and was significantly higher than that of the base material (97 HV). Similarly for the Al-based alloy, compared with the base hardness of 88 HV, the average built hardness was 104 HV. A potential application of FSAM is illustrated by taking an example of a simple stiffener assembly.

  1. Stirring and hydraulic retention time in biogas plant digesters

    Energy Technology Data Exchange (ETDEWEB)

    Kamarad, L.; Bochmann, G.; Kirchmayr, R. [University of Natural Resources and Life Sciences Vienna, Tulln (Austria). Dept. IFA; Pohn, S.; Harasek, M. [Vienna Univ. of Technology (Austria). Inst. of Chemical Engineering

    2010-07-01

    The quality of the mixing affects directly the hydraulic residence time of the feed substrates in the digester, homogeneity of the agitated material, biogas yield and total energy consumption of biogas plants. In practice, in most of the biogas plants the own energy demand is 4-10 % of the total produced electric energy. The majority of this energy (>60%) is needed only for running the agitators. Generally two basic types of stirrer systems are used in agricultural biogas plants. The high speed stirrers (typically propeller-stirrers) are applied for digesters with lower total solids content. Common application is for substrates like maize silage and manure. If the total solids content in the biogas slurry rises (e.g. over 10% TS) or if substrates with fibrous material and a tendency to form a surface layer are used it is preferable to install slow speed stirrers (typically paddle-stirrers) with a horizontal or vertical axis of rotation. In practice, both types are often combined to get a larger range of operating possibilities. Operating experiences showed that slow speed stirrers are less energy demanding than high speed stirrers (Laaber et al., 2007). The objective of this study is to investigate the real retention time of substrate material in anaerobic digesters by two biogas plants using different stirring systems, substrates, operation temperatures and total solids content (TS) in the biogas slurry.

  2. EFFECT OF THICKENERS ON THE TEXTURE OF STIRRED YOGURT

    Directory of Open Access Journals (Sweden)

    D. GONÇALVEZ

    2009-03-01

    Full Text Available

    The effect of the addition of gelatin and starch on the rheological properties of sweetened plain stirred yogurt was studied by manufacturing six samples: two with gelatin (3000 and 6000 ppm, three with starch (1000, 5000, 10000 ppm and a sample without thickener (control. Rheological characterization of the samples was performed using a coaxial cylinder Haake VT500 viscometer. Yield stress ( and hysteresis were also determined. Syneresis (% was measured by centrifugation at 1100 rpm for 10 minutes. Sensory characterization was performed with a panel of trained sensory assessors, who evaluated the following texture attributes: viscosity, ropiness, creaminess and mouthfeel. All samples showed thixotropic and pseudoplastic behaviour. Since the upward curve did not fit a unique model, it was divided in two regions. The first one fitted Herschel-Bulkley’s model. The addition of gelatine decreased flow behaviour index (n, whereas yield stress significantly increased with the addition of both thickeners. Gelatine was more efficient in reducing syneresis than starch. The addition of thickeners significantly increased all the studied sensory texture attributes. Non-oral and oral parameters were highly correlated witch each other and witch rheological parameters. KEYWORDS: Yogurt; texture; thickeners.

  3. Manual adjustable probe tool for friction stir welding

    Science.gov (United States)

    Oelgoetz, Peter A. (Inventor); Ding, Jeff (Inventor)

    2000-01-01

    A friction stir welding tool is provided generally comprising three parts: a rotatable welding tool body (22) that has an outer threaded surface (32) and a probe (24) extending from a distal end of the body, a shoulder (26), which has a threaded inner surface (40) and a bore (36) at a distal end of the shoulder, and a jam nut (28), which has a threaded inner surface (42). The shoulder is threaded onto the tool body such that the probe extends from the shoulder through the bore by a preferred length. The jam nut is then threaded onto the tool body to secure the shoulder. The tool is operatively connected to a drive motor for rotating the tool body. The shoulder may include a knife edge projecting from the distal end (38) thereof adjacent the bore. The knife edge inhibits the weld material from migrating along the probe to intrude inside the shoulder, where it may prevent separation of the tool body and the shoulder when readjustment of the tool is necessary.

  4. Heat generation during plunge stage in friction stir welding

    Directory of Open Access Journals (Sweden)

    Veljić Darko M.

    2013-01-01

    Full Text Available This paper deals with the heat generation in the Al alloy Al2024-T3 plate under different rotating speeds and plunge speeds during the plunge stage of friction stir welding (FSW. A three-dimensional finite element model (FEM is developed in the commercial code ABAQUS/Explicit using the arbitrary Lagrangian-Eulerian formulation, the Johnson-Cook material law and Coulomb’s Law of friction. The heat generation in FSW can be divided into two parts: frictional heat generated by the tool and heat generated by material deformation near the pin and the tool shoulder region. Numerical results obtained in this work indicate a more prominent influence from the friction-generated heat. The slip rate of the tool relative to the workpiece material is related to this portion of heat. The material velocity, on the other hand, is related to the heat generated by plastic deformation. Increasing the plunging speed of the tool decreases the friction-generated heat and increases the amount of deformation-generated heat, while increasing the tool rotating speed has the opposite influence on both heat portions. Numerical results are compared with the experimental ones, in order to validate the numerical model, and a good agreement is obtained.

  5. MOTIONS OF ALLOYING ADDITIONS IN GAS STIRRED LADLES

    Institute of Scientific and Technical Information of China (English)

    S.C. Fan,; B.K. Li; J.C. He

    2001-01-01

    A mathematical model has been developed to analyze the flow patterns and subsurface trajectories of spherical shaped particles (alloy additions) in gas stirring ladles. First,a numerical method to solve fluid flow problems in conjunction with a curvilinear coordinate system is proposed. The internal boundary in flow field, which must be designated in the cylindrical polar coordinate system, can be avoided by using bodyfitted coordinate system (BFC). Consequently, computed flow of molten steel and paths of alloying additions are able to cross smoothly the geometric centerline of cylindrical vessel. Second, motion of particles is calculated in the three-dimensional coordinate system, the modification of parameters, such as the drag coefficient and density in the gas plume region, is examined. When the density of sphere is closer and closer to that of fluid, the path of motion is longer and longer. If the plug is moved off-centered to the half of radius, the path of sphere is prolonged, and the sphere may go through the geometric centerline of vessel, reach the deeper region. The immersed depths increase with increasing entry velocities.``

  6. CFD simulation of solids suspension in stirred tanks: Review

    Directory of Open Access Journals (Sweden)

    Ochieng Aoyi

    2010-01-01

    Full Text Available Many chemical reactions are carried out using stirred tanks, and the efficiency of such systems depends on the quality of mixing, which has been a subject of research for many years. For solid-liquid mixing, traditionally the research efforts were geared towards determining mixing features such as off-bottom solid suspension using experimental techniques. In a few studies that focused on the determination of solids concentration distribution, some methods that have been used have not been accurate enough to account for some small scale flow mal-distribution such as the existence of dead zones. The present review shows that computational fluid dynamic (CFD techniques can be used to simulate mixing features such as solids off-bottom suspension, solids concentration and particle size distribution and cloud height. Information on the effects of particle size and particle size distribution on the solids concentration distribution is still scarce. Advancement of the CFD modeling is towards coupling the physical and kinetic data to capture mixing and reaction at meso- and micro-scales. Solids residence time distribution is important for the design; however, the current CFD models do not predict this parameter. Some advances have been made in recent years to apply CFD simulation to systems that involve fermentation and anaerobic processes. In these systems, complex interaction between the biochemical process and the hydrodynamics is still not well understood. This is one of the areas that still need more attention.

  7. CFD SIMULATION OF A STIRRED DISHED BOTTOM VESSEL

    Directory of Open Access Journals (Sweden)

    Petr Vlček

    2013-12-01

    Full Text Available This paper deals with simulation of the fluid flow in a stirred curved-bottom vessel equipped with three curved blade impellers. The power number and the impeller flow rate number are dimensionless characteristics of the system determined from simulation results and compared with relevant experimental data or data from the literature. The model of the system was created in the conventional Gambit and Fluent program. The system is solved for two designs — for an unbaffled vessel, and for a baffled vessel.The vessel is filled with water and the impeller speed            is 100 min−1. Three turbulent models were used for the solution: k-ε, k-ω and RSM. The results were compared with experimental data or data from the literature. The k-ε model had the smallest demands on processor time, and the results compared satisfactorily with the experimental data. The model provides comprehensive information about the characteristics of the system.

  8. Changes of Resistance During Polyelectrolyte-enhanced Stirred Batch Ultrafiltration

    Institute of Scientific and Technical Information of China (English)

    ZHU Xin-Sheng; Kwang-Ho CHOO

    2007-01-01

    The permeation flux or the resistance in the ultrafiltration process is mainly limited by osmotic pressure,and it may originate from various kinds of polymer interactions. However, the real origin of permeation resistance hasn't been clarified yet in the light of polymer solution nature. The removal of nitrate contamination by polyelectrolytes was carried out with stirred batch ultrafiltration. The polyelectrolyte concentrations both in permeate and retentate were analyzed with total organic carbon analyzer and permeate mass was acquired by electronic balance connected with computer. The total resistance was calculated and interpreted based on the osmotic pressures in three concentration regimes. In the dilute region, the resistance was proportional to polymer concentration; in the semidilute region, the resistance depended on polymer concentration in the parabolic relationship; in the highly concentrated solution regime, the osmotic pressure factor (OPF) would dominate the total resistance; and the deviation from OPF control could come from the electrostatic repulsion between the tightly compacted and charged polyelectrolyte particles at extremely concentrated solution regime. It was first found that dilute and semidilute concentration regions can be easily detected by plotting the log-log curves of the polymer concentration versus the ratio of the total resistance to polymer concentration. The new concept OPF was defined and did work well at highly concentrated regime.

  9. Design of Friction Stir Welding Tool for Avoiding Root Flaws

    Directory of Open Access Journals (Sweden)

    Shude Ji

    2013-12-01

    Full Text Available In order to improve material flow behavior during friction stir welding and avoid root flaws of weld, a tool with a half-screw pin and a tool with a tapered-flute pin are suggested. The effect of flute geometry in tool pins on material flow velocity is investigated by the software ANSYS FLUENT. Numerical simulation results show that high material flow velocity appears near the rotational tool and material flow velocity rapidly decreases with the increase of distance away from the axis of the tool. Maximum material flow velocity by the tool with the tapered-flute pin appears at the beginning position of flute and the velocity decreases with the increase of flow length in flute. From the view of increasing the flow velocity of material near the bottom of the workpiece or in the middle of workpiece, the tool with the half-screw pin and the tool with the tapered-flute pin are both better than the conventional tool.

  10. CFD simulation of an unbaffled stirred tank reactor driven by a magnetic rod: assessment of turbulence models.

    Science.gov (United States)

    Li, Jiajia; Deng, Baoqing; Zhang, Bing; Shen, Xiuzhong; Kim, Chang Nyung

    2015-01-01

    A simulation of an unbaffled stirred tank reactor driven by a magnetic stirring rod was carried out in a moving reference frame. The free surface of unbaffled stirred tank was captured by Euler-Euler model coupled with the volume of fluid (VOF) method. The re-normalization group (RNG) k-ɛ model, large eddy simulation (LES) model and detached eddy simulation (DES) model were evaluated for simulating the flow field in the stirred tank. All turbulence models can reproduce the tangential velocity in an unbaffled stirred tank with a rotational speed of 150 rpm, 250 rpm and 400 rpm, respectively. Radial velocity is underpredicted by the three models. LES model and RNG k-ɛ model predict the better tangential velocity and axial velocity, respectively. RNG k-ɛ model is recommended for the simulation of the flow in an unbaffled stirred tank with magnetic rod due to its computational effort. PMID:26465300

  11. Continuous fermentative hydrogen production in different process conditions

    Energy Technology Data Exchange (ETDEWEB)

    Nasirian, N. [Islamic Azad Univ., Shoushtar (Iran, Islamic Republic of). Dept. of Agricultural Mechanization; Almassi, M.; Minaee, S. [Islamic Azad Univ., Tehran (Iran, Islamic Republic of). Dept. of Agricultural Mechanization; Widmann, R. [Duisburg-Essen Univ., Essen (Germany). Dept. of Environmental Engineering, Waste and Water

    2010-07-01

    This paper reported on a study in which hydrogen was produced by fermentation of biomass. A continuous process using a non-sterile substrate with a readily available mixed microflora was used on heat treated digested sewage sludge from a wastewater treatment plant. Hydrogen was produced from waste sugar at a pH of 5.2 and a temperature of 37 degrees C. An experimental setup of three 5.5 L working volume continuously stirred tank reactors (CSTR) in different stirring speeds were constructed and operated at 7 different hydraulic retention times (HRTs) and different organic loading rates (OLR). Dissolved organic carbon was examined. The results showed that the stirring speed of 135 rpm had a beneficial effect on hydrogen fermentation. The best performance was obtained in 135 rpm and 8 h of HRT. The amount of gas varied with different OLRs, but could be stabilized on a high level. Methane was not detected when the HRT was less than 16 h. The study identified the reactor in which the highest specific rate of hydrogen production occurred.

  12. Normal Brachial Plexus Magnetic Resonance Neurography: Comparison of DWIBS and STIR-EPI%正常臂丛神经MRI技术:DWIBS与STIR-EPI的比较

    Institute of Scientific and Technical Information of China (English)

    曹开明; 郝楠馨; 王葳; 王轶彬; 宗根林

    2010-01-01

    目的 探讨MR背景信号抑制扩散加权成像(DWIBS)序列及短恢复时间反转恢复回波平面成像(STIR-EPI)序列对臂丛神经成像的可行性.资料与方法 利用3.0 T磁共振仪对27名自愿者行臂丛神经MRI,采用DWIBS及STIR-EPI序列.结果 在DWIBS及STIR-EPI图像上臂丛神经根、神经节、锁骨上神经及锁骨下神经均呈高信号;DWIBS对锁骨下神经显示效果较好,而STIR-EPI对于臂丛神经根显示较好,两者对于神经节及锁骨上神经都能很好显示.结论 结合两种序列能够准确显示臂丛神经解剖形态,对于臂丛神经病变的诊断和治疗可提供一定的帮助.

  13. Continuous ethanol production under acidic conditions

    Energy Technology Data Exchange (ETDEWEB)

    1983-09-06

    Gelatinized starch is treated with saccharifying enzymes and immobilized EtOH-producing microorganisms (e.g., Saccharomyces, Candida, Zymomonas) at pH less than or equal to 3.4 to produce EtOH continuously. At this pH, no contamination occurs. Thus, a 25% slurry of cassava powder was heated at 120/sup 0/ for 20 min and mixed with ..cap alpha..-amylase 0.6 and CaCl/sub 2/ 2 g/l. The mixture was stirred at 90/sup 0/ for 30 min, cooled to room temperature, filtered, and the filtrate mixed with 1 g (NH/sub 4/)/sub 2/SO/sub 4/ and adjusted to pH 2.8. A mixture of wine and bakers' yeast (500 g) immobilized on alginate was continuously contacted with the saccharified starch solution to yield 77-90 g EtOH/l.

  14. A design algorithm for batch stirred tank transesterification reactors

    International Nuclear Information System (INIS)

    Highlights: ► Simplified algorithm for batch biodiesel reactor design was developed. ► C Sharp software tool for implementing the algorithm was also developed. ► 50 L/batch reactor was constructed and used to process neem oil biodiesel. ► Results showed that the produced neem biodiesel is a fuel grade product. ► Scale-up of the reactor was carried out using the developed software. - Abstract: A 50 L per batch, stirred tank reactor, suitable for carrying out transesterification of vegetable oils was designed and constructed. The major design assumptions included stainless steel plate thickness of 2 mm, reaction temperature of 60–65 °C and an initial/final fluid temperature of 25/70 °C. The calculated impeller Reynolds number was in the mixed regime zone of 10–104; the power number was varied between 1 and 5, while a typical propeller speed of 22.5 rev/s (or 1350 rev/min) was adopted. The limiting design conditions were maximum reactor diameter of 1.80 m, straight side height-to-diameter ratio in the range of 0.75–1.5 and minimum agitator motor power of 746 W (1 Hp). Based upon the design, a simple algorithm was developed and interpreted into Microsoft C Sharp computer programming language to enable scale up of the reactor. Performance testing of the realized reactor was carried out while using it to produce Neem oil biodiesel via base – catalyzed methanolysis, which yielded high quality fuel product.

  15. Stir Friction Welding Used in Ares I Upper Stage Fabrication

    Science.gov (United States)

    2007-01-01

    Under the goals of the Vision for Space Exploration, Ares I is a chief component of the cost-effective space transportation infrastructure being developed by NASA's Constellation Program. This transportation system will safely and reliably carry human explorers back to the moon, and then onward to Mars and other destinations in the solar system. The Ares I effort includes multiple project element teams at NASA centers and contract organizations around the nation, and is managed by the Exploration Launch Projects Office at NASA's Marshall Space Flight Center (MFSC). ATK Launch Systems near Brigham City, Utah, is the prime contractor for the first stage booster. ATK's subcontractor, United Space Alliance of Houston, is designing, developing and testing the parachutes at its facilities at NASA's Kennedy Space Center in Florida. NASA's Johnson Space Center in Houston hosts the Constellation Program and Orion Crew Capsule Project Office and provides test instrumentation and support personnel. Together, these teams are developing vehicle hardware, evolving proven technologies, and testing components and systems. Their work builds on powerful, reliable space shuttle propulsion elements and nearly a half-century of NASA space flight experience and technological advances. Ares I is an inline, two-stage rocket configuration topped by the Crew Exploration Vehicle, its service module, and a launch abort system. This HD video image depicts the preparation and placement of a confidence ring for friction stir welding used in manufacturing aluminum panels that will fabricate the Ares I upper stage barrel. The aluminum panels are manufactured and subjected to confidence tests during which the bent aluminum is stressed to breaking point and thoroughly examined. The panels are manufactured by AMRO Manufacturing located in El Monte, California. (Highest resolution available)

  16. Deconvoluting the Friction Stir Weld Process for Optimizing Welds

    Science.gov (United States)

    Schneider, Judy; Nunes, Arthur C.

    2008-01-01

    In the friction stir welding process, the rotating surfaces of the pin and shoulder contact the weld metal and force a rotational flow within the weld metal. Heat, generated by the metal deformation as well as frictional slippage with the contact surface, softens the metal and makes it easier to deform. As in any thermo-mechanical processing of metal, the flow conditions are critical to the quality of the weld. For example, extrusion of metal from under the shoulder of an excessively hot weld may relax local pressure and result in wormhole defects. The trace of the weld joint in the wake of the weld may vary geometrically depending upon the flow streamlines around the tool with some geometry more vulnerable to loss of strength from joint contamination than others. The material flow path around the tool cannot be seen in real time during the weld. By using analytical "tools" based upon the principles of mathematics and physics, a weld model can be created to compute features that can be observed. By comparing the computed observations with actual data, the weld model can be validated or adjusted to get better agreement. Inputs to the model to predict weld structures and properties include: hot working properties ofthe metal, pin tool geometry, travel rate, rotation and plunge force. Since metals record their prior hot working history, the hot working conditions imparted during FSW can be quantified by interpreting the final microstructure. Variations in texture and grain size result from variations in the strain accommodated at a given strain rate and temperature. Microstructural data from a variety of FSWs has been correlated with prior marker studies to contribute to our understanding of the FSW process. Once this stage is reached, the weld modeling process can save significant development costs by reducing costly trial-and-error approaches to obtaining quality welds.

  17. Stir Friction Welding Used in Ares I Upper Stage Fabrication

    Science.gov (United States)

    2007-01-01

    Under the goals of the Vision for Space Exploration, Ares I is a chief component of the cost-effective space transportation infrastructure being developed by NASA's Constellation Program. This transportation system will safely and reliably carry human explorers back to the moon, and then onward to Mars and other destinations in the solar system. The Ares I effort includes multiple project element teams at NASA centers and contract organizations around the nation, and is managed by the Exploration Launch Projects Office at NASA's Marshall Space Flight Center (MFSC). ATK Launch Systems near Brigham City, Utah, is the prime contractor for the first stage booster. ATK's subcontractor, United Space Alliance of Houston, is designing, developing and testing the parachutes at its facilities at NASA's Kennedy Space Center in Florida. NASA's Johnson Space Center in Houston hosts the Constellation Program and Orion Crew Capsule Project Office and provides test instrumentation and support personnel. Together, these teams are developing vehicle hardware, evolving proven technologies, and testing components and systems. Their work builds on powerful, reliable space shuttle propulsion elements and nearly a half-century of NASA space flight experience and technological advances. Ares I is an inline, two-stage rocket configuration topped by the Crew Exploration Vehicle, its service module, and a launch abort system. This HD video image depicts friction stir welding used in manufacturing aluminum panels that will fabricate the Ares I upper stage barrel. The panels are subjected to confidence tests in which the bent aluminum is stressed to breaking point and thoroughly examined. The panels are manufactured by AMRO Manufacturing located in El Monte, California. (Highest resolution available)

  18. Mixing In Jet-Stirred Reactors With Different Geometries

    KAUST Repository

    Ayass, Wassim W.

    2013-12-01

    This work offers a well-developed understanding of the mixing process inside Jet- Stirred Reactors (JSR’s) with different geometries. Due to the difficulty of manufacturing these JSR’s made in quartz, existing JSR configurations were assessed with certain modifications and optimal operating conditions were suggested for each reactor. The effect of changing the reactor volume, the nozzle diameter and shape on mixing were both studied. Two nozzle geometries were examined in this study, a crossed shape nozzle and an inclined shape nozzle. Overall, six reactor configurations were assessed by conducting tracer experiments - using the state-of-art technologies of high-speed cameras and laser absorption spectroscopy- and Computational Fluid Dynamics (CFD) simulations. The high-speed camera tracer experiment gives unique qualitative information – not present in the literature – about the actual flow field. On the other hand, when using the laser technique, a more quantitative analysis emerges with determining the experimental residence time distribution (RTD) curves of each reactor. Comparing these RTD curves with the ideal curve helped in eliminating two cases. Finally, the CFD simulations predict the RTD curves as well as the mixing levels of the JSR’s operated at different residence times. All of these performed studies suggested the use of an inclined nozzle configuration with a reactor diameter D of 40mm and a nozzle diameter d of 1mm as the optimal choice for low residence time operation. However, for higher residence times, the crossed configuration reactor with D=56mm and d=0.3mm gave a nearly perfect behavior.

  19. Ethylene oxidation chemistry in a well-stirred reactor

    Energy Technology Data Exchange (ETDEWEB)

    Marinov, N. [Lawrence Livermore National Lab., CA (United States); Malte, P. [Univ. of Washington, Seattle, WA (United States). Dept. of Mechanical Engineering

    1994-09-01

    Ethylene is an important intermediate in the combustion of methane, larger aliphatic hydrocarbons, and aromatics. Detailed fuel-lean C{sub 2}H{sub 4}H{sub 2}O/air well-stirred reactor data by Thornton were used to analyze reported combustion chemistry mechanisms and the development of this study`s ethylene oxidation mechanism. The data set had been obtained for the temperature range 1,003 to 1,253 K and ethylene-oxygen equivalence ratio range 0.086 to 0.103, at atmospheric pressure. Mechanisms were derived from reaction sets of Westbrook and Pitz, and Dagaut, Cathonnet and Boettner. Examination of each reported mechanism indicated unusually large kinetic rates for the vinyl decomposition reaction were used in order to obtain agreement with the Thornton data set. An ethylene oxidation model was developed in order to address the mechanistic problems of the previous models. This study`s mechanism well simulated the overall rate of ethylene oxidation and concentration profiles of CO, CO{sub 2}, H{sub 2}, CH{sub 2}O, C{sub 2}H{sub 2}, CH{sub 3}OH, CH{sub 4}, and C{sub 2}H{sub 6}. Successful predictions by the model were dependent on a new high temperature vinyl oxidation reaction route, C{sub 2}H{sub 3} + O{sub 2} = CH{sub 2}CHO + O with a branching ratio of 1.19--1.21 at 1,053 K to 1.63--2.47 at 1,253 K. The branching ratio values were dependent upon the extent of fall-off for the C{sub 2}H{sub 3} + O{sub 2} = CH{sub 2}O + HCO reaction. 132 refs.

  20. Continuous Low Cost Transesterification Process for the Production of Coconut Biodiesel

    Directory of Open Access Journals (Sweden)

    Chandra P. Singh

    2010-01-01

    Full Text Available Biodiesel, or alkyl ester, is an alternative renewable, biodegradable, and non-toxic diesel fuel produced by the catalytic transesterification of vegetable oil. Here we characterize a system for continuous transesterification of vegetable oil using five continuous stirring tank reactors (5CSTRs. We tested residence times of 16–43min, stirring speeds of 200–800rpm, a catalyst concentration (KOH of 0.25–1 wt% of oil (in gram, different total flow rates of the oil and MeOH, and on the production performance of the 5 stage continuous reactor for transesterification of vegetable oil. Using a molar ratio of oil:methanol of 1:7 and a reaction temperature of 65 °C, we show that a high stirring speed increased the reaction rate, but an excessive stir speed decreased the reaction rate and conversion to biodiesel. Furthermore, a higher catalyst percentage significantly increased the reaction rate and production capacity. A catalyst percentage of 1 wt% of oil gave the best conversion; 99.04 ± 0.05%. The resulting biodiesel esters were characterized for their physical and fuel properties including density, viscosity, iodine volume, acid volume, cloud point, pure point, gross heat of combustion, and volatility. The purity and conversion of the biodiesel was analyzed by HPLC.

  1. Local melting and tool slippage during friction stir spot welding of aluminum alloys

    Science.gov (United States)

    Gerlich, Adrian Piotr

    Local melting and tool slippage during friction stir spot welding of different aluminum alloys is examined using a combination of detailed microscopy and temperature measurement. It has been widely accepted that friction stir welding is a solid-state process and does not involve melting. The present research indicates that local melting is an inherent feature when Al 7075 and Al 2024 alloys are spot welded, and produces tool slippage at the tool contact interface. In contrast, intermetallic particles contained in the Al 5754 and Al 6061 as-received materials do not melt and a no-slip condition is maintained. A combination of data acquisition of key welding parameters (axial force, torque and tool displacement), high-speed imaging, temperature measurement and metallography are employed to study the tool penetration stage and the subsequent dwell period during spot welding. A methodology is developed for reliably determining the stir zone temperature using thermocouples embedded within the tool itself. Tool slippage is investigated by determining the strain rate in stir zone material adjacent to the rotating tool. The strain rate is estimated by substituting stir zone temperature and subgrain size measurements into the Zener-Hollomon equation. Tool penetration early in the friction stir spot welding process can be explained as a progression of wear events from mild (delamination) wear, through to severe wear, and finally to melt wear in the material located immediately under the tip of the rotating pin. The stir zone peak temperature during welding is limited by either the solidus temperature of the alloy in question, or by local melting of intermetallic particles contained in the base material such as Al 7075 or Al 2024 alloys. Melted films dissolve rapidly in the high temperature stir zone, and as the weld cools to room temperature. Metallographic evidence confirming local melting and cracking is observed in Al 7075 and Al 2024 alloy friction stir spot welds made

  2. Physical Simulation of Friction Stir Welding and Processing of Nickel-Base Alloys Using Hot Torsion

    Science.gov (United States)

    Rule, James R.; Lippold, John C.

    2013-08-01

    The Gleeble hot torsion test was utilized in an attempt to simulate the friction stir-processed microstructure of three Ni-base alloys: Hastelloy X, Alloy 625, and Alloy 718. The simulation temperatures were based on actual thermal cycles measured by embedded thermocouples during friction stir processing of these alloys. Peak process temperatures were determined to be approximately 1423 K (1150 °C) for Hastelloy X and Alloy 625 K and 1373 K (352 °C and 1100 °C) for Alloy 718. The peak temperature and cooling rates were programed into the Gleeble™ 3800 thermo-mechanical simulator to reproduce the stir zone and thermo-mechanically affected zone (TMAZ) microstructures. The TMAZ was successfully simulated using this technique, but the stir zone microstructure could not be accurately reproduced, with hot torsion samples exhibiting larger grain size than actual friction stir processing trials. Shear stress and strain rates as a function of temperature were determined for each material using hot torsion simulation.

  3. Stirring in massive, young debris discs from spatially resolved Herschel images

    CERN Document Server

    Moór, A; Ábrahám, P; Apai, D; Balog, Z; Grady, C; Henning, Th; Juhász, A; Kiss, Cs; Krivov, A V; Pawellek, N; Szabó, Gy M

    2014-01-01

    A significant fraction of main-sequence stars are encircled by dusty debris discs, where the short-lived dust particles are replenished through collisions between planetesimals. Most destructive collisions occur when the orbits of smaller bodies are dynamically stirred up, either by the gravitational effect of locally formed Pluto-sized planetesimals (self-stirring scenario), or via secular perturbation caused by an inner giant planet (planetary stirring). The relative importance of these scenarios in debris systems is unknown. Here we present new Herschel Space Observatory imagery of 11 discs selected from the most massive and extended known debris systems. All discs were found to be extended at far-infrared wavelengths, five of them being resolved for the first time. We evaluated the feasibility of the self-stirring scenario by comparing the measured disc sizes with the predictions of the model calculated for the ages of our targets. We concluded that the self-stirring explanation works for seven discs. How...

  4. Post Process Characterization of Friction Stir Welded Components Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Luna Innovations Incorporated proposes in this STTR Phase II project to continue development and validation of Luna's amplitude-dependent, nonlinear ultrasonic...

  5. Fundamental Study of Material Flow in Friction Stir Welds

    Science.gov (United States)

    Reynolds, Anthony P.

    1999-01-01

    The presented research project consists of two major parts. First, the material flow in solid-state, friction stir, butt-welds as been investigated using a marker insert technique. Changes in material flow due to welding parameter as well as tool geometry variations have been examined for different materials. The method provides a semi-quantitative, three-dimensional view of the material transport in the welded zone. Second, a FSW process model has been developed. The fully coupled model is based on fluid mechanics; the solid-state material transport during welding is treated as a laminar, viscous flow of a non-Newtonian fluid past a rotating circular cylinder. The heat necessary for the material softening is generated by deformation of the material. As a first step, a two-dimensional model, which contains only the pin of the FSW tool, has been created to test the suitability of the modeling approach and to perform parametric studies of the boundary conditions. The material flow visualization experiments agree very well with the predicted flow field. Accordingly, material within the pin diameter is transported only in the rotation direction around the pin. Due to the simplifying assumptions inherent in the 2-D model, other experimental data such as forces on the pin, torque, and weld energy cannot be directly used for validation. However, the 2-D model predicts the same trends as shown in the experiments. The model also predicts a deviation from the "normal" material flow at certain combinations of welding parameters, suggesting a possible mechanism for the occurrence of some typical FSW defects. The next step has been the development of a three-dimensional process model. The simplified FSW tool has been designed as a flat shoulder rotating on the top of the workpiece and a rotating, cylindrical pin, which extends throughout the total height of the flow domain. The thermal boundary conditions at the tool and at the contact area to the backing plate have been varied

  6. Process parameters optimization for friction stir welding of RDE-40 aluminium alloy using Taguchi technique

    Institute of Scientific and Technical Information of China (English)

    A.K.LAKSHMINARAYANAN; V.BALASUBRAMANIAN

    2008-01-01

    Taguchi approach was applied to determine the most influential control factors which will yield better tensile strength of the joints of friction stir welded RDE-40 aluminium alloy. In order to evaluate the effect of process parameters such as tool rotational speed, traverse speed and axial force on tensile strength of friction stir welded RDE-40 aluminium alloy, Taguchi parametric design and optimization approach was used. Through the Taguchi parametric design approach, the optimum levels of process parameters were determined. The results indicate that the rotational speed, welding speed and axial force are the significant parameters in deciding the tensile strength of the joint. The predicted optimal value of tensile strength of friction stir welded RDE-40 aluminium alloy is 303 MPa. The results were confirmed by further experiments.

  7. Numerical Simulation of Linear Electromagnetic Stirring in Secondary Cooling Region of Slab Caster

    Institute of Scientific and Technical Information of China (English)

    HUANG Jun-tao; WANG En-gang; HE Ji-cheng

    2003-01-01

    According to the theory of alternating magnetohydrodynamics and magnetic boundary renewal method, mathematical models were proposed for electromagnetic stirring in secondary cooling region (SEMS) of slab caster. The magnetic fields and flow fields of melt were simulated with SEMS. It′s shown that the electromagnetic forces with inward and sidelong components produced by travel magnetic field at the wide faces of slab make the melt whirling in horizontal section, and the convection of the melt is strengthened obviously there. In addition, magnetic flux density attenuates from the edge to the center of slab, and the profile of the melt velocity along slab thickness in the center of the horizontal section takes a two-opposite-peak configuration. Ultimately, the stirring intensity and features are determined by the electromagnetic parameters, coil arrangement and stirring types.

  8. Finite Element Simulation in Superplastic forming of Friction Stir Welded Aluminium Alloy 6061-T6

    Directory of Open Access Journals (Sweden)

    P Ganesh

    2011-09-01

    Full Text Available Superplasticity in materials is the ability of materials to achieve large elongation only under specific conditions of temperature and strain rate. Superplastic Forming (SPF is an important industrial process that has found application in sheet metal forming in the aerospace and automotive industries. Friction Stir Welding (FSW is a solid state joining process that can alter the grain structure of the parent material. FSW process is an effective tool to refine the grain structure of the sheet metal and enhance their Superplasticity. Friction Stir Welding was used to join Superplastic AA 6061-T6 sheets. The Finite Element Simulation was performed for the Superplastic Forming of the Friction Stir Welded joints to evaluate the thinning and formability of AA 6061-T6 for hemispherical shape. The commercially available Finite Element Software ABAQUS was used to execute these simulations.

  9. Mechanism of removing inclusions from molten aluminum by stirring active molten flux

    Institute of Scientific and Technical Information of China (English)

    周鸣; 李克; 孙宝德; 疏达; 倪红军; 王俊; 张佼

    2003-01-01

    Removal of inclusions from industrial pure molten aluminum(A01) by stirring active molten flux wasstudied. Wettability of nonmetallic inclusions in the molten aluminum was worse than that in active molten flux. Ac-cording to the surface renewal model, the inclusions were easily transferred into molten active flux from fine alumi-num droplets and then reacted chemically when molten aluminum was dispersed into fine aluminum droplets in stir-ring active molten flux. Tensile tests show that tensile strength of purified tensile sample(as-cast) increases by8.59%. SEM photographs show that the fracture cracks of purified tensile sample are homogeneous, and the dim-ples are small and homogeneous. From metallographs and statistic results of Leco analysis software, it is found thatthe quantities and sizes of the inclusions in purified sample are obviously fewer and smaller than in unpurified tensilesample(as-cast).

  10. Temperature comparison of initial, middle and final point of polypropylene friction stir welded

    Science.gov (United States)

    Kusharjanta, Bambang; Raharjo, Wahyu P.; Triyono

    2016-03-01

    Friction Stir Welding is known as a new solid state joining process. This process is applied in thermoplastic polymers material recently. One of member thermoplastic polymer is polypropylene. Polypropylene sheet 6 mm thick was friction stir welded with a cone cut steel pin. Tool rotation, travelling speed, and plunge depth, as welding parameters were 620 rpm, 7.3 mm/minutes and 0.02 mm respectively. Temperature at the initial, middle, and final point of advance side working piece were measured and compared. Measurement were done by thermocouple and recorded by data acquisition. Based on this research, it is concluded that temperature at the initial, middle and final point of friction stir welding process are different. The highest temperature peak reach at the middle point on the advance side which affects face bending strength.

  11. Preparation of CuCr alloys by thermit-reduction electromagnetic stirring

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The influences of the additive CaF2, different molds, mold pre-heating temperature, electromagnetic stirring, and alloying elements on CuCr have been investigated respectively during the preparation of CuCr alloys by thermit-reduction electromagnetic cation point of slags to improve the metal separating efficiency from slags; the crystal particles become thinner because of the high cooling velocity in the metal mold; while casting in the graphite mold, the casting properties of CuCr improve with the increase of pre-heating temperature; the compact alloys are prepared at 500℃; electromagnetic stirring can prevent the growth of dendrite crystal into refine crystal particles, as well as homogenize Cu and Cr to improve the CuCr properties; the optimal stirring time is 7 min;when the alloying elements Ni and Co are added to the reactants, elements Cu and Cr can distribute evenly but the crystal particles become thick.

  12. Microstructural and Mechanical Characteristics of Aluminum Alloy AA5754 Friction Stir Spot Welds

    Science.gov (United States)

    Mahmoud, T. S.; Khalifa, T. A.

    2014-03-01

    In the present investigation, friction stir spot welding on annealed aluminum alloy AA5754 sheets was performed. The influences of the tool rotational speed and tool stirring (dwell) time on the weld structure and static strength of welds were evaluated. The results revealed that the width of the completely metallurgical-bonded region increases with the increasing tool rotational speed and/or the dwell time up to certain levels. Increasing such parameters beyond these levels slightly reduces the width of the bonding region. The stirred zone exhibited higher microhardness than that of the base material. The tensile-shear force was found to increase with the increasing tool rotational speed and/or dwell time up to a certain level (9s). Higher tool rotational speeds and/or prolonged dwell times slightly reduce(s) the tensile-shear force.

  13. Processing-Microstructure Relationships in Friction Stir Welding of MA956 Oxide Dispersion Strengthened Steel

    Science.gov (United States)

    Baker, Bradford W.; Menon, E. Sarath K.; McNelley, Terry R.; Brewer, Luke N.; El-Dasher, Bassem; Farmer, Joseph C.; Torres, Sharon G.; Mahoney, Murray W.; Sanderson, Samuel

    2014-12-01

    A comprehensive set of processing-microstructure relationships is presented for friction stir welded oxide dispersion strengthened MA956 steel. Eight rotational speed/traverse speed combinations were used to produce friction stir welds on MA956 plates using a polycrystalline cubic boron nitride tool. Weld conditions with high thermal input produced defect-free, full-penetration welds. Electron backscatter diffraction results showed a significant increase in grain size, a persistent body centered cubic torsional texture in the stir zone, and a sharp transition in grain size across the thermo-mechanically affected zone sensitive to weld parameters. Micro-indentation showed an asymmetric reduction in hardness across a transverse section of the weld. This gradient in hardness was greatly increased with higher heat inputs. The decrease in hardness after welding correlates directly with the increase in grain size and may be explained with a Hall-Petch type relationship.

  14. Effect of tool geometry on friction stir spot welding of polypropylene sheets

    Directory of Open Access Journals (Sweden)

    M. K. Bilici

    2012-10-01

    Full Text Available The effects of tool geometry and properties on friction stir spot welding properties of polypropylene sheets were studied. Four different tool pin geometries, with varying pin angles, pin lengths, shoulder diameters and shoulder angles were used for friction stir spot welding. All the welding operations were done at the room temperature. Lap-shear tensile tests were carried out to find the weld static strength. Weld cross section appearance observations were also done. From the experiments the effect of tool geometry on friction stir spot weld formation and weld strength were determined. The optimum tool geometry for 4 mm thick polypropylene sheets were determined. The tapered cylindrical pin gave the biggest and the straight cylindrical pin gave the lowest lap-shear fracture load.

  15. Effect of Tool Shoulder and Pin Probe Profiles on Friction Stirred Aluminum Welds - a Comparative Study

    Institute of Scientific and Technical Information of China (English)

    H. K. Mohanty; M. M. Mahapatra; P. Kumar; P. Biswas; N. R. Mandal

    2012-01-01

    In marine application,marine grade steel is generally used for haul and superstructures.However,aluminum has also become a good choice due to its lightweight qualities,while rusting of aluminum is minimal compared to steel.In this paper a study on friction stir welding of aluminum alloys was presented.The present investigation deals with the effects of different friction stir welding tool geometries on mechanical strength and the microstructure properties of aluminum alloy welds.Three distinct tool geometries with different types of shoulder and tool probe profiles were used in the investigation according to the design matrix.The effects of each tool shoulder and probe geometry on the weld was evaluated.It was also observed that the friction stir weld tool geometry has a significant effect on the weldment reinforcement,microhardness,and weld strength.

  16. Mechanical properties of friction stir butt-welded Al-5086 H32 plate

    Directory of Open Access Journals (Sweden)

    G. Çam

    2008-10-01

    Full Text Available Purpose: The purpose of the paper is to study Al-5086 H32 plates with a thickness of 3 mm friction stir butt-welded using different welding speeds at a tool rotational speed of 1600 rpm. Design/methodology/approach: The effect of welding speed on the weld performance of the joints was investigated by conducting optical microscopy, microhardness measurements and mechanical tests (i.e. tensile and bend tests. The effect of heat input during friction stir welding on the microstructure, and thus mechanical properties, of cold-rolled Al- 5086 plates was also determined.Findings: The experimental results indicated that the maximum tensile strength of the joints, which is about 75% that of the base plate, was obtained with a traverse speed of 200 mm/min at the tool rotational speed used, e.g. 1600 rpm, and the maximum bending angle of the joints can reach 180º. The maximum ductility performance of the joints was, on the other hand, relatively low, e.g. about 20%. These results are not unexpected due to the loss of the cold-work strengthening in the weld region as a result of the heat input during welding, and thus the confined plasticity within the stirred zone owing to strength undermatching. Higher joint performances can also be achieved by increasing the penetration depth of the stirring probe in butt-friction stir welding of Al-5086 H32 plates.Research limitations/implications: The results suggest that both strength and ductility performances can be increased by optimizing the tool penetration depth.Originality/value: Examination of mechanical properties of friction stir butt-welded Al-5086 H32 plate.

  17. Numerical Simulation of Gas—Liquid Flow in a Stirred Tank with a Rushton Impeller

    Institute of Scientific and Technical Information of China (English)

    WANGWeijing; MAOZaisha

    2002-01-01

    The gas-liquid flow field in a stirred tank with a Rushton disk turbine,including the impeller region,was numerically simulated using the improved inner-outer iterative procedure.The characteristic features of the strirred tank,such as gas cavity and accumulation of gas at the two sides of wall baffles,can be captured by the simulation.The simulated results agree well with available experimental data.Since the improved inner-outer iterative algorithm demands no empirical formula and experimental data for the impeller region,and the approach seems generally applicable for simulating gas-liquid stirred tanks.

  18. Acute hematogenous osteomyelitis - exclusion by means of turbo-STIR sequence?

    International Nuclear Information System (INIS)

    The timely diagnosis and early initiation of antibiotic therapy determine the clinical course of an acute hematogenous osteomyelitis. Consequently, a fast and efficient MRI examination protocol is crucial. We retrospectively evaluated various MR sequences used in the examination of 8 children having osteomyelitis. The examinations were conducted using a 0.5 T MR machine. All patients had a high signal intensity of the lesion in the IR sequence with fat suppression (turbo-STIR). An acute osteomyelitis can be excluded in the absence of signal intensity increase in the turbo-STIR sequence without the necessity of having to perform additional sequences. (orig.)

  19. Design and Fabrication of a Stir Casting Furnace Set-Up

    Directory of Open Access Journals (Sweden)

    Manabhanjan Sahoo

    2015-07-01

    Full Text Available Now-a-days a large variety of heating techniques/furnaces are available. There may be many method for supplying heat to the work but heat is produced either by combustion of fuel or electric resistance heating. Taking into consideration the effect of cost, safety, simplicity and ease of construction we are going for an electrical resistance heating furnace with indirect heating provisions. The stir casting furnace has two main parts that enable to perform all its operations, they are: Furnace Elements and Control Panel. This paper shows the design and fabrication of stir-casting furnace and aluminium melted and casted to form.

  20. Friction Stir Spot Welding: A Review on Joint Macro- and Microstructure, Property, and Process Modelling

    Directory of Open Access Journals (Sweden)

    X. W. Yang

    2014-01-01

    Full Text Available Friction stir spot welding (FSSW is a very useful variant of the conventional friction stir welding (FSW, which shows great potential to be a replacement of single-point joining processes like resistance spot welding and riveting. There have been many reports and some industrial applications about FSSW. Based on the open literatures, the process features and variants, macro- and microstructural characteristics, and mechanical properties of the resultant joints and numerical simulations of the FSSW process were summarized. In addition, some applications of FSSW in aerospace, aviation, and automobile industries were also reviewed. Finally, the current problems and issues that existed in FSSW were indicated.

  1. Numerical Simulation of Macroscopic Mixing in a Rushton Impeller Stirred Tank

    Institute of Scientific and Technical Information of China (English)

    王正; 毛在砂; 沈湘黔

    2006-01-01

    The macroscopic mixing in a stirred tank with different tracer injection locations, impeller speeds and impeller positions is simulated numerically by solving the transport equation of the tracer based on the whole flow field in the baffled tank with a Rushton disk turbine numerically resolved using the improved inner-outer iterative procedure. Predicted mixing time is compared well with the literature correlations. The predicted residence time distribution of the stirred tank is very close to the present experimental results. The effect of the installation of a draft tube on the mixing time and residence time distributions is addressed.

  2. Microstructural Evolution and Wear Resistance of Friction Stir-Processed AISI 52100 Steel

    Science.gov (United States)

    Seraj, R. A.; Abdollah-zadeh, A.; Hajian, M.; Kargar, F.; Soltanalizadeh, R.

    2016-07-01

    Friction stir processing (FSP) was successfully applied on AISI 52100 steel. The influence of process parameters on the microstructure and mechanical properties of the material was evaluated. It was observed that the initial ferritic-pearlitic microstructure of the base metal is transformed to the martensitic microstructure with retained austenite in the stir zone. The results also showed that microhardness and wear resistance of the FSP samples are, respectively, at least 2 and 15 times higher than those of the base metal. The improvement of the mechanical properties of FSP samples was attributed to their microstructural characteristics. The mechanisms controlling the wear behavior of the base metal and FSP samples were also discussed.

  3. Multiple Crack Growth Prediction in AA2024-T3 Friction Stir Welded Joints, Including Manufacturing Effects

    DEFF Research Database (Denmark)

    Carlone, Pierpaolo; Citarella, Roberto; Sonne, Mads Rostgaard;

    2016-01-01

    A great deal of attention is currently paid by several industries toward the friction stir welding process to realize lightweight structures. Within this aim, the realistic prediction of fatigue behavior of welded assemblies is a key factor. In this work an integrated finite element method - dual...... boundary element method (FEM-DBEM) procedure, coupling the welding process simulation to the subsequent crack growth assessment, is proposed and applied to simulate multiple crack propagation, with allowance for manufacturing effects. The friction stir butt welding process of the precipitation hardened AA...

  4. Spindle-shaped nanoscale yolk/shell magnetic stirring bars for heterogeneous catalysis in macro- and microscopic systems.

    Science.gov (United States)

    Yang, Shuliang; Cao, Changyan; Peng, Li; Huang, Peipei; Sun, Yongbin; Wei, Fang; Song, Weiguo

    2016-01-28

    A new type of spindle-shaped nanoscale yolk/shell magnetic stirring bar containing noble metal nanoparticles was prepared. The as-synthesized Pd-Fe@meso-SiO2 not only showed impressive activity and stability as a heterogeneous catalyst in a macroscopic flask system, but also acted as an efficient nanoscale magnetic stir bar in a microscopic droplet system.

  5. Spin-echo and STIR MR imaging of sports-related muscle injuries at 1.5 T

    International Nuclear Information System (INIS)

    This paper assesses the value of T2-weighted and short T1 inversion recovery (Stir 1,800,170,27) sequences in the MR diagnosis and follow-up of muscle strain injuries. Fifty-six athletes with clinically diagnosed traumatic muscular damage were studied at 1.5 T with SE T1-weighted, double T2-weighted, and STIR techniques. Images were evaluated in order to detect the presence of muscle tear with associated edema, muscle hemorrhage (focal or diffuse), and perimuscular hemorrhage. The relative conspicuity of muscle injuries on T2-weighted and STIR images was assessed. All acute and subacute muscle injuries were detected on both SE T2-weighted and STIR images, muscle edema and subacute hemorrhage appearing hyperintense to normal muscle. Acute hemorrhage could appear hypointense on T2-weighted images but was always hyperintense on STIR images

  6. Interface and properties of the friction stir welded joints of titanium alloy Ti6Al4V with aluminum alloy 6061

    International Nuclear Information System (INIS)

    Highlights: • Friction stir butt welding of titanium alloy Ti6Al4V and aluminum alloy A6061-T6. • Welding parameters affect interfacial microstructure of the joint. • Welding parameters affect the mechanical property of joint and fracture position. • Joining mechanism of Ti6Al4V/A6061 dissimilar alloys by FSW is investigated. - Abstract: Titanium alloy Ti6Al4V and aluminum alloy 6061 dissimilar material joints were made with friction stir welding (FSW) method. The effects of welding parameters, including the stir pin position, the rotating rate and the travel speed of the tool, on the interface and the properties of the joints were investigated. The macrostructure of the joints and the fracture surfaces of the tensile test were observed with optical microscope and scanning electron microscope (SEM). The interface reaction layer was investigated with transmission electron microscopy (TEM). The factors affecting the mechanical properties of the joints were discussed. The results indicated that the tensile strength of the joints and the fracture location are mainly dependent on the rotating rate, and the interface and intermetallic compound (IMC) layer are the governing factor. There is a continuous 100 nm thick TiAl3 IMC at the interface when the rotating rate is 750 rpm. When the welding parameters were appropriate, the joints fractured in the thermo-mechanically affected zone (TMAZ) and the heat affected zone (HAZ) of the aluminum alloy and the strength of the joints could reach 215 MPa, 68% of the aluminum base material strength, as well as the joint could endure large plastic deformation

  7. Friction stir welding - an alternative method for sealing nuclear waste storage canisters

    Energy Technology Data Exchange (ETDEWEB)

    Andrews, R.E. [TWI Ltd, Cambridge (United Kingdom)

    2004-12-01

    When welding 50 mm thick copper a very high heat input is required to combat the high thermal diffusivity and only the Electron Beam Welding (EBW) process had this capability when this copper canister concept was conceived. Despite the encouraging results achieved using EBW with thick section copper, SKB felt that it would be prudent to assess other joining methods. This assessment concluded that friction welding, could also provide very high quality welds to satisfy the service life requirements of the SKB canister design. A friction welding variant called Friction Stir Welding (FSW) was shown to have the capability of welding 3 mm thick copper sheet with excellent integrity and reproducibility. This later provided sufficient encouragement for SKB to consider the potential of FSW as a method for joining thick section copper, using relatively simple machine tool based technology. It was thought that FSW might provide an alternative or complementary method for welding lids, or bases to canisters. In 1997 an FSW development programme started at TWI, focussed on the feasibility of welding 10 mm thick copper plate. Once this task was successfully completed, work continued to demonstrate that progressively thicker plate, up to 50 mm thick, could be joined. At this stage, with process viability established, a full size experimental FSW canister machine was designed and built. Work with this machine finished in January 2003, when it had been shown that FSW could definitely be used to weld lids to full size canisters. This report summarises the TWI development of FSW for SKB from 1997 to January 2003. It also highlights the important aspects of the process and the project milestones that will help to ensure that SKB has a welding technology that can be used with confidence for production fabrication of copper waste storage canisters in the future. The overall conclusion to this FSW development is that there is no doubt that the FSW process could be used to produce full

  8. Modeling and simulation of large scale stirred tank

    Science.gov (United States)

    Neuville, John R.

    The purpose of this dissertation is to provide a written record of the evaluation performed on the DWPF mixing process by the construction of numerical models that resemble the geometry of this process. There were seven numerical models constructed to evaluate the DWPF mixing process and four pilot plants. The models were developed with Fluent software and the results from these models were used to evaluate the structure of the flow field and the power demand of the agitator. The results from the numerical models were compared with empirical data collected from these pilot plants that had been operated at an earlier date. Mixing is commonly used in a variety ways throughout industry to blend miscible liquids, disperse gas through liquid, form emulsions, promote heat transfer and, suspend solid particles. The DOE Sites at Hanford in Richland Washington, West Valley in New York, and Savannah River Site in Aiken South Carolina have developed a process that immobilizes highly radioactive liquid waste. The radioactive liquid waste at DWPF is an opaque sludge that is mixed in a stirred tank with glass frit particles and water to form slurry of specified proportions. The DWPF mixing process is composed of a flat bottom cylindrical mixing vessel with a centrally located helical coil, and agitator. The helical coil is used to heat and cool the contents of the tank and can improve flow circulation. The agitator shaft has two impellers; a radial blade and a hydrofoil blade. The hydrofoil is used to circulate the mixture between the top region and bottom region of the tank. The radial blade sweeps the bottom of the tank and pushes the fluid in the outward radial direction. The full scale vessel contains about 9500 gallons of slurry with flow behavior characterized as a Bingham Plastic. Particles in the mixture have an abrasive characteristic that cause excessive erosion to internal vessel components at higher impeller speeds. The desire for this mixing process is to ensure the

  9. Formation of Oxides in the Interior of Friction Stir Welds

    Science.gov (United States)

    Schneider, Judy; Chen, Po; Nunes, Arthur C., Jr.

    2016-01-01

    In friction stir welding (FSWing) the actual solid state joining takes place between the faying surfaces which form the weld seam. Thus the seam trace is often investigated for clues when the strength of the weld is reduced. Aluminum and its alloys are known to form a native, protective oxide on the surface. If these native surface oxides are not sufficiently broken up during the FSW process, they are reported to remain in the FSW interior and weaken the bond strength. This type of weld defect has been referred to as a lazy "S", lazy "Z", joint line defect, kissing bond, or residual oxide defect. Usually these defects are mitigated by modification of the process parameters, such as increased tool rotation rate, which causes a finer breakup of the native oxide particles. This study proposes that there may be an alternative mechanism for formation of oxides found within the weld nugget. As the oxidation rate increases at elevated temperatures above 400ºC, it may be possible for enhanced oxidation to occur on the interior surfaces during the FSW process from entrained air entering the seam gap. Normally, FSWs of aluminum alloys are made without a purge gas and it is unknown how process parameters and initial fit up could affect a potential air path into the interior during the processing. In addition, variations in FSW parameters, such as the tool rotation, are known to have a strong influence on the FSW temperature which may affect the oxidation rate if internal surfaces are exposed to entrained air. A series of FSWs were made in 3 different thickness panels of AA2219 (0.95, 1.27 and 1.56 cm) at 2 different weld pitches. As the thickness of the panels increased, there was an increased tendency for a gap to form in advance of the weld tool. If sufficient air is able to enter the workpiece gap prior to consolidation, the weld temperature can increase the oxidation rate on the interior surfaces. These oxidation rates would also be accelerated in areas of localized

  10. A temperature dependent slip factor based thermal model for friction stir welding of stainless steel

    Indian Academy of Sciences (India)

    M Selvaraj

    2013-12-01

    This paper proposes a new slip factor based three-dimensional thermal model to predict the temperature distribution during friction stir welding of 304L stainless steel plates. The proposed model employs temperature and radius dependent heat source to study the thermal cycle, temperature distribution, power required, the effect of process parameters on heat generation per mm length of the weld and peak temperature during the friction stir welding process. Simulations of friction stir welding process were carried out on 304L stainless steel workpieces for various rotational and welding speeds. The predicted thermal cycle, power required and temperature distributions were found to be in good agreement with the experimental results. The heat generation per mm length of weld and peak temperature were found to be directly proportional to rotational speed and inversely proportional to welding speed. The rate of increase in heat generation per mm length of the weld and peak temperature are found to be higher at lower rotational speeds and lower at higher rotational speed. The heat generation during friction stir welding was found to be 80.8 % at shoulder, 16.1 % at pin side and 3.1 % at the bottom of the pin.

  11. Behavior of Liquid-Liquid Dispersions in a Stirred Vessel——Part 1:Uniformity Property

    Institute of Scientific and Technical Information of China (English)

    LIU Jinchen; CHEN Jian; KAWASAKI Junjiro

    2001-01-01

    The conductivity of liquid-liquid dispersions in a stirred vessel was measured at different sampling positions inside the vessel.The results showed that both O/W dispersions and W/O dispersions are not spatially uniform inside the vessel,especially the W/O dispersions.The results provide further understanding of the properties of the liquid-liquid dispersions.

  12. Systematic investigation of the fatigue performance of a friction stir welded low alloy steel

    International Nuclear Information System (INIS)

    Highlights: • The fatigue behaviour of a friction stir welded low alloy steel has been assessed. • The welds’ fatigue lives outperform the International Institute of Welding’s recommendations for fusion welds. • The slow weld exhibits the best fatigue performance of the investigated welds. • Fracture surface analysis shows that minor embedded flaws do not offer crack initiation sites. • Process-related surface breaking flaws have a significant effect on the fatigue life. - Abstract: A comprehensive fatigue performance assessment of friction stir welded DH36 steel has been undertaken to address the relevant knowledge gap for this process on low alloy steel. A detailed set of experimental procedures specific to friction stir welding has been put forward, and the consequent study extensively examined the weld microstructure and hardness in support of the tensile and fatigue testing. The effect of varying welding parameters was also investigated. Microstructural observations have been correlated to the weldments’ fatigue behaviour. The typical fatigue performance of friction stir welded steel plates has been established, exhibiting fatigue lives well above the weld detail class of the International Institute of Welding even for tests at 90% of yield strength, irrespective of minor instances of surface breaking flaws which have been identified. An understanding of the manner in which these flaws impact on the fatigue performance has been established, concluding that surface breaking irregularities such as these produced by the tool shoulder’s features on the weld top surface can be the dominant factor for crack initiation under fatigue loading

  13. Muscle MRI STIR signal intensity and atrophy are correlated to focal lower limb neuropathy severity

    Energy Technology Data Exchange (ETDEWEB)

    Deroide, N.; Mambre, L.; Kubis, Nathalie [Service de Physiologie Clinique-Explorations Fonctionnelles, AP-HP, Hopital Lariboisiere, Paris (France); Universite Paris Diderot, Sorbonne Paris Cite France, Paris (France); Bousson, V.; Laredo, J.D. [Universite Paris Diderot, Sorbonne Paris Cite France, Paris (France); Radiologie Osteo-articulaire, AP-HP, Hopital Lariboisiere, Paris (France); Vicaut, E. [Universite Paris Diderot, Sorbonne Paris Cite France, Paris (France); URC, AP-HP, Hopital Lariboisiere, Paris (France)

    2014-09-26

    The objective is to determine if muscle MRI is useful for assessing neuropathy severity. Clinical, MRI and electromyography (EMG) examinations were performed in 17 patients with focal lower limb neuropathies. MRI Short Tau Inversion Recovery (STIR) signal intensity, amyotrophy, and muscle fatty infiltration measured after T1-weighted image acquisition, EMG spontaneous activity (SA), and maximal voluntary contraction (MVC) were graded using semiquantitative scores and quantitative scores for STIR signal intensity and were correlated to the Medical Research Council (MRC) score for testing muscle strength. Within this population, subgroups were selected according to severity (mild versus severe), duration (subacute versus chronic), and topography (distal versus proximal) of the neuropathy. EMG SA and MVC MRI amyotrophy and quantitative scoring of muscle STIR intensity were correlated with the MRC score. Moreover, MRI amyotrophy was significantly increased in severe, chronic, and proximal neuropathies along with fatty infiltration in chronic lesions. Muscle MRI atrophy and quantitative evaluation of signal intensity were correlated to MRC score in our study. Semiquantitative evaluation of muscle STIR signal was sensitive enough for detection of topography of the nerve lesion but was not suitable to assess severity. Muscle MRI could support EMG in chronic and proximal neuropathy, which showed poor sensitivity in these patients. (orig.)

  14. Microstructure and optical appearance of anodized friction stir processed Al - Metal oxide surface composites

    DEFF Research Database (Denmark)

    Gudla, Visweswara Chakravarthy; Jensen, Flemming; Bordo, Kirill;

    2014-01-01

    Multiple-pass friction stir processing (FSP) was employed to impregnate Ti, Y and Ce oxide powders into the surface of an Aluminium alloy. The FSP processed surface composite was subsequently anodized with an aim to develop optical effects in the anodized layer owing to the presence of incorporated...

  15. A technology of floating type stirring%一种浮动式搅拌技术

    Institute of Scientific and Technical Information of China (English)

    罗娟; 赵立欣; 董保成; 陈羚; 宋成军; 万小春

    2012-01-01

    综述了搅拌对厌氧消化过程的影响.通过比较,分析目前沼气工程中应用的3种机械搅拌方式,针对秸秆厌氧消化过程中易发生布料不均匀、挂壁、结壳等造成消化率低、容积产气率低、使用寿命短的问题,开发了一种能够适应浮动物料、实现垂直空间大范围搅拌的搅拌技术,介绍了其工作原理并展望了在沼气工程中的应用前景.%The impact of stirring on anaerobic digestion process was discussed in this paper. Through the comparison, analysised three kinds of mechanical stirring methods which used in current biogas plans. According to the problems such as low digestibility value, low volumetric biogas production rate and short life performance resulting from uneven distributed material, wall sticking and encrustation, a stirring technology of floating type which can adapt to floating raw materials and realize vertical large-area stirring has been developed. The working principle of this technology was introduced, and its application prospects in biogas plans were proposed.

  16. LABORATORY AND NUMERICAL INVESTIGATIONS OF RESIDENCE TIME DISTRIBUTION OF FLUIDS IN LAMINAR FLOW STIRRED ANNULAR PHOTOREACTOR

    Science.gov (United States)

    Laboratory and Numerical Investigations of Residence Time Distribution of Fluids in Laminar Flow Stirred Annular PhotoreactorE. Sahle-Demessie1, Siefu Bekele2, U. R. Pillai11U.S. EPA, National Risk Management Research LaboratorySustainable Technology Division,...

  17. Optimization of the Process Parameters for Controlling Residual Stress and Distortion in Friction Stir Welding

    DEFF Research Database (Denmark)

    Tutum, Cem Celal; Schmidt, Henrik Nikolaj Blicher; Hattel, Jesper Henri

    2008-01-01

    In the present paper, numerical optimization of the process parameters, i.e. tool rotation speed and traverse speed, aiming minimization of the two conflicting objectives, i.e. the residual stresses and welding time, subjected to process-specific thermal constraints in friction stir welding, is i...

  18. CFD SIMULATION OF THE HYDRODYNAMICS AND MIXING TIME IN A STIRRED TANK

    Directory of Open Access Journals (Sweden)

    AOYI OCHIENG

    2010-12-01

    Full Text Available Hydrodynamics and mixing efficiency in stirred tanks influence power draw and are therefore important for the design of many industrial processes. In the present study, both experimental and simulation methods were employed to determine the flow fields in different mixing tank configurations in a single phase system. Laser Doppler velocimetry (LDV and computational fluid dynamics (CFD techniques were used to determine the flow fields in systems with and without a draft tube. There was reasonable agreement between the simulation and experimental results. It was shown that the use of a draft tube with a Rushton turbine and hydrofoil impeller resulted in a reduction in the homogenization energy by 19.2 and 17.7%, respectively. This indicates that a reduction in the operating cost can be achieved with the use of a draft tube in a stirred tank and there would be a greater cost reduction in a system stirred by the Rushton turbine compared to that stirred by a propeller.

  19. Structure and properties of fixed joints formed by ultrasonic-assisted friction-stir welding

    Energy Technology Data Exchange (ETDEWEB)

    Fortuna, S. V., E-mail: s-fortuna@ispms.ru; Ivanov, K. V., E-mail: ikv@ispms.ru; Eliseev, A. A., E-mail: alan@ispms.ru [Institute of Strength Physics and Materials ScienceTomsk, 634055 (Russian Federation); Tarasov, S. Yu., E-mail: tsy@ispms.ru; Ivanov, A. N., E-mail: ivan@ispms.ru; Rubtsov, V. E., E-mail: rvy@ispms.ru; Kolubaev, E. A., E-mail: eak@ispms.ru [Institute of Strength Physics and Materials ScienceTomsk, 634055 (Russian Federation); National Research Tomsk Polytechnic University, Tomsk, 634050 (Russian Federation)

    2015-10-27

    This paper deals with structure and properties of aluminum alloy 7475 and its joints obtained by friction stir welding including under ultrasonic action. Microhardness measurements show that ultrasonic action increases strength properties of the joints. Optical and transmission electron microscopy reveals that this effect is related to the precipitation of tertiary coherent S-and T-phase particles.

  20. STUDY OF ELECTROMAGNETIC STIRRING REFINING MICRO- STRUCTURES OF PIPE-LINE STEEL SAW DEPOSITS

    Institute of Scientific and Technical Information of China (English)

    Y. Zhang; B.N. Qian; X.M. Guo

    2002-01-01

    The effects of electromagnetic stirring on the microstructures of pipe-line steel SAWdeposited metal were investigated. The results showed that electromagnetic stirringincreased the number density of inclusions with 0.2-0.6μm in diameter and promotedthe formation and refining of acicular ferrite within austenite grains. The low tem-perature toughness of deposited metal was improved.

  1. Friction stir processed Al - Metal oxide surface composites: Anodization and optical appearance

    DEFF Research Database (Denmark)

    Gudla, Visweswara Chakravarthy; Jensen, Flemming; Canulescu, Stela;

    2014-01-01

    Multiple-pass friction stir processing (FSP) was employed to impregnate metal oxide (TiO2, Y2O3 and CeO2) particles into the surface of an Aluminium alloy. The surface composites were then anodized in a sulphuric acid electrolyte. The effect of anodizing parameters on the resulting optical...

  2. Feasibility of treating partially soluble wastewater in anaerobic sequencing batch biofilm reactor (ASBBR) with mechanical stirring.

    Science.gov (United States)

    Pinho, Samantha Cristina; Ratusznei, Suzana Maria; Rodrigues, José Alberto Domingues; Foresti, Eugenio; Zaiat, Marcelo

    2005-03-01

    This work reports on the treatment of partially soluble wastewater in an anaerobic sequencing batch biofilm reactor, containing biomass immobilized on polyurethane matrices and stirred mechanically. The results showed that agitation provided optimal mixing and improved the overall organic matter consumption rates. The system showed to be feasible to enhance the treatment of partially soluble wastewaters. PMID:15491835

  3. Precipitate evolution in friction stir welding of 2219-T6 aluminum alloys

    International Nuclear Information System (INIS)

    Precipitate evolution in friction stir welding of 2219-T6 aluminum alloys was characterized by transmission electron microscopy. In the weld nugget zone and the thermo-mechanically affected zone some metastable precipitates overaged to equilibrium phase while others solutionized into the aluminum solid solution. In the heat-affected zone the precipitates coarsened.

  4. Gas–liquid flow in stirred reactors: Trailing vortices and gas accumulation behind impeller blades

    NARCIS (Netherlands)

    Ranade, Vivek V.; Deshpande, Vaibhav R.

    1999-01-01

    In a gas–liquid stirred reactor, gas tends to accumulate in low-pressure regions behind the impeller blades. Such gas accumulation significantly alters impeller performance characteristics. We have computationally investigated gas–liquid flow generated by a Rushton (disc) turbine. Rotating Rushton t

  5. Kinetic Study of COS with Tertiary Alkanolamine Solutions. 1. Experiments in an Intensely Stirred Batch Reactor

    NARCIS (Netherlands)

    Littel, Rob J.; Versteeg, Geert F.; Swaaij, Wim P.M. van

    1992-01-01

    The reaction between COS and various tertiary alkanolamines in aqueous solutions has been studied in an intensely stirred batch reactor. Experiments for TEA, DMMEA, and DEMEA were carried out at 303 K; the reaction between COS and aqueous MDEA has been studied at temperatures ranging from 293 to 323

  6. Microstructure of electromagnetic stirred semi-solid AZ91D alloy

    Institute of Scientific and Technical Information of China (English)

    毛卫民; 甄子胜; 陈洪涛; 钟雪友

    2004-01-01

    The microstructures of semi-solid AZ91D alloy stirred by rotationally electromagnetic field were studied.The shape of primary α-Mg phase is dendrite under conventional solidification condition and the primary α-Mg grains are changed to the fine rosette-like or granular grains under electromagnetic stirring condition. If the electromagnetic stirring frequencies are low, there are a large amount of fine rosette-like primary α-Mg grains and the fine rosettelike primary α-Mg grain in two dimensions belongs to a single grain in three dimensions; there are also many spherical primary α-Mg grains, they may belong to a single grain in three dimensions and the orientation differences of the grains between them are very small. If the electromagnetic stirring frequencies are high, a lot of the fine rosette-like primary α-Mg grains disappear and are converted into granular grains, and moreover, most of these granular grains belong to different grains in three dimensions.

  7. Heat source models in simulation of heat flow in friction stir welding

    DEFF Research Database (Denmark)

    Schmidt, Henrik Nikolaj Blich; Hattel, Jesper

    2004-01-01

    The objective of the present paper is to investigate the effect of including the tool probe and the material flow in the numerical modelling of heat flow in friction stir welding (FSW). The contact condition at the interface between the tool and workpiece controls the heat transfer mechanisms...

  8. Fatigue Behavior of Friction Stir-Welded Joints Repaired by Grinding

    Science.gov (United States)

    Vidal, C.; Infante, V.

    2014-04-01

    Fatigue is undoubtedly the most important design criterion in aeronautic structures. Although friction stir-welded joints are characterized by a high mechanical performance, they can enclose some defects, especially in their root. These defects along with the relatively low residual stresses of the friction stir-welding thermomechanical cycle can turn into primary sources of crack initiation. In this context, this article deals with the fatigue behavior of friction stir-welded joints subjected to surface smoothing by grinding improvement technique. The 4-mm-thick aluminum alloy 2024-T351 was used in this study. The fatigue strength of the base material, joints in the as-welded condition, and the sound and defective friction stir-welded joints improved by grinding were investigated in detail. The tests were carried out with a constant amplitude loading and with a stress ratio of R = 0. The fatigue results show that an improvement in fatigue behavior was obtained in the joints repaired by superficial grinding technique. The weld grinding technique is better especially for lower loads and increases the high cycle fatigue strength. The fatigue strength of the improved welded joints was higher than that of the base material.

  9. Heat Source Models in Simulation of Heat Flow in Friction Stir Welding

    DEFF Research Database (Denmark)

    Schmidt, Henrik Nikolaj Blich; Hattel, Jesper

    2004-01-01

    The objective of the present paper is to investigate the effect of including the tool probe and the material flow in the numerical modelling of heat flow in Friction Stir Welding (FSW). The contact condition at the interface between the tool and workpiece controls the heat transfer mechanisms...

  10. Robust Optimization of Thermal Aspects of Friction Stir Welding Using Manifold Mapping Techniques

    DEFF Research Database (Denmark)

    Larsen, Anders Astrup; Lahaye, Domenico; Schmidt, Henrik Nikolaj Blicher;

    2008-01-01

    The aim of this paper is to optimize a friction stir welding process taking robustness into account. The optimization problems are formulated with the goal of obtaining desired mean responses while reducing the variance of the response. We restrict ourselves to a thermal model of the process...

  11. Optimum condition by mechanical characteristic evaluation in friction stir welding for 5083-O Al alloy

    Institute of Scientific and Technical Information of China (English)

    Min-Su HAN; Seung-Jun LEE; Jae-Cheul PARK; Seok-Cheol KO; Yong-Bin WOO; Seong-Jong KIM

    2009-01-01

    The mechanical characteristics for friction stir welding (FSW) of 5083-O Al alloy were evaluated. The results show that in FSW at 800 r/min and 124 mm/min, a weld defect is observed at the start point. However, the button shape at the end point is good and the stir zone has a soft appearance. At 267 mm/min, a void occurs at the button. A slight weld defect and rough stir zone are seen both at the start and end points at 342 mm/min. Moreover, at the bottom, a tunnel-type void is observed from an early stage to the end point, and at 1 800 r/min, a weld defect can be found from an early stage to the end point. These defects are rough with imperfect joining due to excessive rotation speed and high physical force. Weld fractures relative to rotational and travel speeds are observed at the stir zone. The optimum FSW conditions are a welding speed of 124 mm/min and a rotational speed of 800 r/min.

  12. Microstructure of AA 2024 fixed joints formed by friction stir welding

    Science.gov (United States)

    Eliseev, A. A.; Kalashnikova, T. A.; Tarasov, S. Yu.; Rubtsov, V. E.; Fortuna, S. V.; Kolubaev, E. A.

    2015-10-01

    Friction stir welded butt joints on 2024T3 alloy have been obtained using different process parameters. The microstructures of all the weld joint zones have been examined and such structural parameters as grain size, particle size and volume content of particles have been determined in order to find correlations with the microhardness of the corresponding zones of the weld.

  13. An analytical model for the heat generation in friction stir welding

    DEFF Research Database (Denmark)

    Schmidt, Henrik Nikolaj Blich; Hattel, Jesper; Wert, John

    2004-01-01

    The objective of this work is to establish an analytical model for heat generation by friction stir welding (FSW), based on different assumptions of the contact condition between the rotating tool surface and the weld piece. The material flow and heat generation are characterized by the contact...

  14. Optimization of Thermal Aspects of Friction Stir Welding – Initial Studies Using a Space Mapping Technique

    DEFF Research Database (Denmark)

    Larsen, Anders Astrup; Bendsøe, Martin P.; Schmidt, Henrik Nikolaj Blicher;

    2007-01-01

    The aim of this paper is to optimize a thermal model of a friction stir welding process. The optimization is performed using a space mapping technique in which an analytical model is used along with the FEM model to be optimized. The results are compared to traditional gradient based optimization...

  15. Strain hardening and damage in 6xxx series aluminum alloy friction stir welds

    DEFF Research Database (Denmark)

    Simar, Aude; Nielsen, Kim Lau; de Meester, Bruno;

    2010-01-01

    A friction stir weld in 6005A-T6 aluminum alloy has been prepared and analyzed by micro-hardness measurements, tensile testing and scanning electron microscopy (SEM). The locations of the various weld zones were determined by micro-hardness indentation measurements. The flow behavior of the vario...

  16. LARGE EDDY SIMULATIONS OF THE TURBULENT FLOW IN A STIRRED TANK

    DEFF Research Database (Denmark)

    Fan, Jianhua; Wang, Yundong; Fei, Weiyang

    Computational fluid dynamics (CFD) simulations of the fluid flow in a baffled, stirred tank with a single Rushton turbine are performed. The simulations are carried out on the “Shengcao-21C” supercomputer via commercial CFD software CFX5, using k-ε and large eddy simulation (LES) turbulence model...

  17. LARGE EDDY SIMULATIONS OF THE TURBULENT FLOW IN A STIRRED TANK

    DEFF Research Database (Denmark)

    Fan, Jianhua; Wang, Yundong; Fei, Weiyang

    2005-01-01

    Computational fluid dynamics (CFD) simulations of the fluid flow in a baffled, stirred tank with a single Rushton turbine are performed. The simulations are carried out on the “Shengcao-21C” supercomputer via commercial CFD software CFX5, using k-ε and large eddy simulation (LES) turbulence model...

  18. Anaerobic digestion of blackwater from vacuum toilets and kitchen refuse in a continuous stirred tank reactor (CSTR).

    Science.gov (United States)

    Wendland, C; Deegener, S; Behrendt, J; Toshev, P; Otterpohl, R

    2007-01-01

    The objective of this research was mesophilic anaerobic digestion of blackwater from vacuum toilets (BW) and kitchen refuse (KR) in a CSTR within an ecological sanitation system. A detailed investigation of the BW characteristics was carried out. Research on anaerobic digestion was performed with CSTR of 101 volume at HRT of 10, 15 and 20 days. The digestion of BW at 20 days HRT showed stable performance without inhibition effects, in spite of relatively high ammonium concentrations. The removal of total and particulate COD was 61% and 53%, respectively, and the methane yield 10/CH4/cap/day. The addition of kitchen refuse (KR) improved the performance of the CSTR in terms of COD removal efficiency and methane yield. At 20 days HRT the removal of total and particulate COD increased up to 71% and 67%, respectively, and the methane yield to 27/CH4/cap/day. The results at 15 days HRT showed similar performance. At HRT of 10 days, the anaerobic treatment was limited but reached steady state conditions at higher VFA concentrations in the effluent, with a decrease of COD removal of 30 to 33% and of methane yields of 19 to 21%.

  19. Design of an Adaptive PID Neural Controller for Continuous Stirred Tank Reactor based on Particle Swarm Optimization

    Directory of Open Access Journals (Sweden)

    Khulood A. Dagher

    2013-12-01

    Full Text Available A particle swarm optimization algorithm and neural network like self-tuning PID controller for CSTR system is presented. The scheme of the discrete-time PID control structure is based on neural network and tuned the parameters of the PID controller by using a particle swarm optimization PSO technique as a simple and fast training algorithm. The proposed method has advantage that it is not necessary to use a combined structure of identification and decision because it used PSO. Simulation results show the effectiveness of the proposed adaptive PID neural control algorithm in terms of minimum tracking error and smoothness control signal obtained for non-linear dynamical CSTR system.

  20. Co-digestion of food and garden waste with mixed sludge from wastewater treatment in continuously stirred tank reactors.

    Science.gov (United States)

    Fitamo, T; Boldrin, A; Boe, K; Angelidaki, I; Scheutz, C

    2016-04-01

    Co-digestions of urban organic waste were conducted to investigate the effect of the mixing ratio between sludge, food waste, grass clippings and green waste at different hydraulic retention times (HRTs). Compared to the digestion of 100% sludge, the methane yield increased by 48% and 35%, when co-digesting sludge with food waste, grass clippings and garden waste with a corresponding %VS of 10:67.5:15.75:6.75 (R1) and 10:45:31.5:13.5 (R2), respectively. The methane yield remained constant at around 425 and 385 NmL CH4/g VS in R1 and R2, respectively, when the reactors were operated at HRTs of 15, 20 and 30 days. However, the methane yield dropped significantly to 356 (R1) and 315 (R2) NmL CH4/g VS when reducing the HRT to 10 days, indicating that the process was stressed. Since the methane production rate improved significantly with decreasing HRT, the trade-off between yield and productivity was obtained at 15 days HRT. PMID:26866760

  1. Biogas Upgrading via Hydrogenotrophic Methanogenesis in Two-Stage Continuous Stirred Tank Reactors at Mesophilic and Thermophilic Conditions

    DEFF Research Database (Denmark)

    Bassani, Ilaria; Kougias, Panagiotis; Treu, Laura;

    2015-01-01

    This study proposes an innovative setup composed by two stage reactors to achieve biogas upgrading coupling the CO2 in the biogas with external H2 and subsequent conversion into CH4 by hydrogenotrophic methanogenesis. In this configuration, the biogas produced in the first reactor was transferred...... to the second one, where H2 was injected. This configuration was tested at both mesophilic and thermophilic conditions. After H2 addition, the produced biogas was upgraded to average CH4 content of 89% in the mesophilic reactor and 85% in the thermophilic. At thermophilic conditions, a higher efficiency of CH4...

  2. Biogas upgrading by injection of hydrogen in a two-stage Continuous Stirred-Tank Reactor system

    DEFF Research Database (Denmark)

    Bassani, Ilaria; Kougias, Panagiotis; Treu, Laura;

    An innovative method for biogas upgrading (i.e. CH4 content more than 90%) combines the coupling of H2, which could be produced by water electrolysis using surplus renewable electricity produced from wind mills, with the CO2 of the biogas. CO2 is biologically converted to CH4 by hydrogenotrophic...... methanogens. In this study, a novel serial biogas reactor system is presented, in which the produced biogas from the first stage reactor was introduced in the second stage, where also H2 was injected. The effects of the H2 addition on the process performance and on the microbial community were investigated...

  3. Co-digestion of food and garden waste with mixed sludge from wastewater treatment in continuously stirred tank reactors

    DEFF Research Database (Denmark)

    Fitamo, Temesgen Mathewos; Boldrin, Alessio; Boe, Kanokwan;

    2016-01-01

    Co-digestions of urban organic waste were conducted to investigate the effect of the mixing ratio between sludge, food waste, grass clippings and green waste at different hydraulic retention times (HRTs). Compared to the digestion of 100% sludge, the methane yield increased by 48% and 35%, when co......-digesting sludge with food waste, grass clippings and garden waste with a corresponding % VS of 10:67.5:15.75:6.75 (R1) and 10:45:31.5:13.5 (R2), respectively. The methane yield remained constant at around 425 and 385 NmL CH4/g VS in R1 and R2, respectively, when the reactors were operated at HRTs of 15, 20 and 30...

  4. Biogas Upgrading via Hydrogenotrophic Methanogenesis in Two-Stage Continuous Stirred Tank Reactors at Mesophilic and Thermophilic Conditions.

    Science.gov (United States)

    Bassani, Ilaria; Kougias, Panagiotis G; Treu, Laura; Angelidaki, Irini

    2015-10-20

    This study proposes an innovative setup composed by two stage reactors to achieve biogas upgrading coupling the CO2 in the biogas with external H2 and subsequent conversion into CH4 by hydrogenotrophic methanogenesis. In this configuration, the biogas produced in the first reactor was transferred to the second one, where H2 was injected. This configuration was tested at both mesophilic and thermophilic conditions. After H2 addition, the produced biogas was upgraded to average CH4 content of 89% in the mesophilic reactor and 85% in the thermophilic. At thermophilic conditions, a higher efficiency of CH4 production and CO2 conversion was recorded. The consequent increase of pH did not inhibit the process indicating adaptation of microorganisms to higher pH levels. The effects of H2 on the microbial community were studied using high-throughput Illumina random sequences and full-length 16S rRNA genes extracted from the total sequences. The relative abundance of archaeal community markedly increased upon H2 addition with Methanoculleus as dominant genus. The increase of hydrogenotrophic methanogens and syntrophic Desulfovibrio and the decrease of aceticlastic methanogens indicate a H2-mediated shift toward the hydrogenotrophic pathway enhancing biogas upgrading. Moreover, Thermoanaerobacteraceae were likely involved in syntrophic acetate oxidation with hydrogenotrophic methanogens in absence of aceticlastic methanogenesis.

  5. L-glutamic acid production in a continuous stirred tank bioreactor using coimmobilized bio-catalyst using a fluorosensor.

    Science.gov (United States)

    Prabhu, N; Babu, J Sarat Chandra; Sundaram, S

    2002-01-01

    The production of L-Glutamic acid has been studied using coimmobilized whole cells of pseudomonas reptilivora and micrococcus glutamicus in a two litre Tokyo Rikakikai fermentor using glucose as selected production medium. The process was carried out at an optimum temperature of 32 degree Celsius and a pH of 7.2. The progress of the reaction was recorded using Dr. Ingold fluorosensor. The effect of initial substrate concentration, speed of agitation, volume ofcalcium alginate beads and aeration rate on the yield of glutamic acid has been investigated. It has been found that the acid production increases exponentially with substrate concentration, and mass transfer co-efficient varied linearly with aeration rate. The kinetic parameters also had been estimated.

  6. Microstructure and Low-Cycle Fatigue of a Friction-Stir-Welded 6061 Aluminum Alloy

    Science.gov (United States)

    Feng, A. H.; Chen, D. L.; Ma, Z. Y.

    2010-10-01

    Strain-controlled low-cycle fatigue (LCF) tests and microstructural evaluation were performed on a friction-stir-welded 6061Al-T651 alloy with varying welding parameters. Friction stir welding (FSW) resulted in fine recrystallized grains with uniformly distributed dispersoids and dissolution of primary strengthening precipitates β″ in the nugget zone (NZ). Two low-hardness zones (LHZs) appeared in the heat-affected zone (HAZ) adjacent to the border between the thermomechanically-affected zone (TMAZ) and HAZ, with the width decreasing with increasing welding speed. No obvious effect of the rotational rate on the LHZs was observed. Cyclic hardening of the friction-stir-welded joints was appreciably stronger than that of base metal (BM), and it also exhibited a two-stage character where cyclic hardening of the friction-stir-welded 6061Al-T651 alloy at higher strain amplitudes was initially stronger followed by an almost linear increase of cyclic stress amplitudes on the semilog scale. Fatigue life, cyclic yield strength, cyclic strain hardening exponent, and cyclic strength coefficient all increased with increasing welding speed, but were nearly independent of the rotational rate. Most friction-stir-welded joints failed along the LHZs and exhibited a shear fracture mode. Fatigue crack initiation was observed to occur from the specimen surface, and crack propagation was mainly characterized by the characteristic fatigue striations. Some distinctive tiremark patterns arising from the interaction between the hard dispersoids/inclusions and the relatively soft matrix in the LHZ under cyclic loading were observed to be present in-between the fatigue striations.

  7. Molecularly imprinted polymeric stir bar: Preparation and application for the determination of naftopidil in plasma and urine samples.

    Science.gov (United States)

    Peng, Jun; Xiao, Deli; He, Hua; Zhao, Hongyan; Wang, Cuixia; Shi, Tian; Shi, Kexin

    2016-01-01

    In this study, molecularly imprinting technology and stir bar absorption technology were combined to develop a microextraction approach based on a molecularly imprinted polymeric stir bar. The molecularly imprinted polymer stir bar has a high performance, is specific, economical, and simple to prepare. The obtained naftopidil-imprinted polymer-coated bars could simultaneously agitate and adsorb naftopidil in the sample solution. The ratio of template/monomer/cross-linker and conditions of template removal were optimized to prepare a stir bar with highly efficient adsorption. Fourier transform infrared spectroscopy, scanning electron microscopy, selectivity, and extraction capacity experiments showed that the molecularly imprinted polymer stir bar was prepared successfully. To utilize the molecularly imprinted polymer stir bar for the determination of naftopidil in complex body fluid matrices, the extraction time, stirring speed, eluent, and elution time were optimized. The limits of detection of naftopidil in plasma and urine sample were 7.5 and 4.0 ng/mL, respectively, and the recoveries were in the range of 90-112%. The within-run precision and between-run precision were acceptable (relative standard deviation performance liquid chromatography was a convenient, rapid, efficient, and specific method for the precise determination of trace naftopidil in clinical analysis. PMID:26541792

  8. Monoterpenoid oxindole alkaloid production by Uncaria tomentosa (Willd) D.C. cell suspension cultures in a stirred tank bioreactor.

    Science.gov (United States)

    Trejo-Tapia, Gabriela; Cerda-García-Rojas, Carlos M; Rodríguez-Monroy, Mario; Ramos-Valdivia, Ana C

    2005-01-01

    Cell growth, monoterpenoid oxindole alkaloid (MOA) production, and morphological properties of Uncaria tomentosa cell suspension cultures in a 2-L stirred tank bioreactor were investigated. U. tomentosa (cell line green Uth-3) was able to grow in a stirred tank at an impeller tip speed of 95 cm/s (agitation speed of 400 rpm), showing a maximum biomass yield of 11.9 +/- 0.6 g DW/L and a specific growth rate of 0.102 d(-1). U. tomentosa cells growing in a stirred tank achieved maximum volumetric and specific MOA concentration (467.7 +/- 40.0 microg/L, 44.6 +/- 5.2 microg/g DW) at 16 days of culture. MOA chemical profile of cell suspension cultures growing in a stirred tank resembled that of the plant. Depending on culture time, from the total MOA produced, 37-100% was found in the medium in the bioreactor culture. MOA concentration achieved in a stirred tank was up to 10-fold higher than that obtained in Erlenmeyer flasks (agitated at 110 rpm). In a stirred tank, average area of the single cells of U. tomentosa increased up to 4-fold, and elliptical form factor increased from 1.40 to 2.55, indicating enlargement of U. tomentosa single cells. This work presents the first report of U. tomentosa green cell suspension cultures that grow and produce MOA in a stirred tank bioreactor.

  9. Mechanical Properties and Microstructure of Dissimilar Friction Stir Welds of 11Cr-Ferritic/Martensitic Steel to 316 Stainless Steel

    Science.gov (United States)

    Sato, Yutaka S.; Kokawa, Hiroyuki; Fujii, Hiromichi T.; Yano, Yasuhide; Sekio, Yoshihiro

    2015-12-01

    Dissimilar joints between ferritic and austenitic steels are of interest for selected applications in next generation fast reactors. In this study, dissimilar friction-stir welding of an 11 pct Cr ferritic/martensitic steel to a 316 austenitic stainless steel was attempted and the mechanical properties and microstructure of the resulting welds were examined. Friction-stir welding produces a stir zone without macroscopic weld-defects, but the two dissimilar steels are not intermixed. The two dissimilar steels are interleaved along a sharp zigzagging interface in the stir zone. During small-sized tensile testing of the stir zone, this sharp interface did not act as a fracture site. Furthermore, the microstructure of the stir zone was refined in both the ferritic/martensitic steel and the 316 stainless steel resulting in improved mechanical properties over the adjacent base material regions. This study demonstrates that friction-stir welding can produce welds between dissimilar steels that contain no macroscopic weld-defects and display suitable mechanical properties.

  10. Generalized Continued Logarithms and Related Continued Fractions

    OpenAIRE

    Borwein, Jonathan M.; Hare, Kevin G.; Lynch, Jason G.

    2016-01-01

    We study continued logarithms as introduced by Bill Gosper and studied by J. Borwein et. al.. After providing an overview of the type I and type II generalizations of binary continued logarithms introduced by Borwein et. al., we focus on a new generalization to an arbitrary integer base $b$. We show that all of our so-called type III continued logarithms converge and all rational numbers have finite type III continued logarithms. As with simple continued fractions, we show that the continued ...

  11. The effect of postprocessing on tensile property and microstructure evolution of friction stir welding aluminum alloy joint

    International Nuclear Information System (INIS)

    Friction stir welding is an efficient manufacturing method for joining aluminum alloy and can dramatically reduce grain size conferring excellent plastic deformation properties. Consequently, friction stir welding is used to manufacture tailor welded blanks to optimize weight or performance in the final component. In the study, the microstructural evolution and mechanical properties of friction stir welding joint during plastic forming and subsequent heat treatment were investigated. The microstructural characteristics of the friction stir welding joints were studied by Electron Backscattered Diffraction and Transmission Electron Microscopy. The mechanical properties were evaluated by tensile and microhardness tests. It is found that the tensile and yield strengths of friction stir welding joints are significantly improved after severe plastic deformation due to the grain refinement. Following heat treatment, the strength of the friction stir welding joints significantly decrease due to the obvious abnormal grain growth. Careful attention must be given to the processing route of any friction stir welding joint intended for plastic forming, especially the annealing between forming passes. Severe plastic deforming of the friction stir welding joint leads to a high level of stored energy/dislocation density, which causes the abnormal grain growth during subsequent heat treatment, and consequently reduce the mechanical properties of the friction stir welding joint. - Highlights: • Great changes are observed in the microstructure of FSW joint after postprocessing. • Postprocessing shows great effect on the microstructure stability of FSW joint. • The weld shows more significant decrease in strength than the BM due to the AGG. • Attention must be given to the processing route of FSW joint for plastic forming

  12. The effect of postprocessing on tensile property and microstructure evolution of friction stir welding aluminum alloy joint

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Z.L., E-mail: zhilihuhit@163.com [Hubei Key Laboratory of Advanced Technology of Automobile Parts, Wuhan University of Technology, Wuhan 430070 (China); State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001 (China); State Key Laboratory of Materials Processing and Die & Mould Technology, Huazhong University of Science and Technology (China); Wang, X.S. [State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001 (China); Pang, Q. [School of Mechanical and Electrical Engineering, Wuhan Donghu University, Wuhan 430070 (China); Huang, F.; Qin, X.P.; Hua, L. [Hubei Key Laboratory of Advanced Technology of Automobile Parts, Wuhan University of Technology, Wuhan 430070 (China)

    2015-01-15

    Friction stir welding is an efficient manufacturing method for joining aluminum alloy and can dramatically reduce grain size conferring excellent plastic deformation properties. Consequently, friction stir welding is used to manufacture tailor welded blanks to optimize weight or performance in the final component. In the study, the microstructural evolution and mechanical properties of friction stir welding joint during plastic forming and subsequent heat treatment were investigated. The microstructural characteristics of the friction stir welding joints were studied by Electron Backscattered Diffraction and Transmission Electron Microscopy. The mechanical properties were evaluated by tensile and microhardness tests. It is found that the tensile and yield strengths of friction stir welding joints are significantly improved after severe plastic deformation due to the grain refinement. Following heat treatment, the strength of the friction stir welding joints significantly decrease due to the obvious abnormal grain growth. Careful attention must be given to the processing route of any friction stir welding joint intended for plastic forming, especially the annealing between forming passes. Severe plastic deforming of the friction stir welding joint leads to a high level of stored energy/dislocation density, which causes the abnormal grain growth during subsequent heat treatment, and consequently reduce the mechanical properties of the friction stir welding joint. - Highlights: • Great changes are observed in the microstructure of FSW joint after postprocessing. • Postprocessing shows great effect on the microstructure stability of FSW joint. • The weld shows more significant decrease in strength than the BM due to the AGG. • Attention must be given to the processing route of FSW joint for plastic forming.

  13. CONTINUOSLY STIRRED TANK REACTOR PARAMETERS THAT AFFECT SLUDGE BATCH 6 SIMULANT PROPERTIES

    Energy Technology Data Exchange (ETDEWEB)

    Newell, J.; Lambert, D.; Stone, M.; Fernandez, A.

    2010-05-28

    The High Level Radioactive Waste (HLW) Sludge in Savannah River Site (SRS) waste tanks was produced over a period of over 60 years by neutralizing the acidic waste produced in the F and H Separations Canyons with sodium hydroxide. The HLW slurries have been stored at free hydroxide concentrations above 1 M to minimize the corrosion of the carbon steel waste tanks. Sodium nitrite is periodically added as a corrosion inhibitor. The resulting waste has been subjected to supernate evaporation to minimize the volume of the stored waste. In addition, some of the waste tanks experienced high temperatures so some of the waste has been at elevated temperatures. Because the waste is radioactive, the waste is transforming through the decay of shorter lived radioactive species and the radiation damage that the decay releases. The goal of the Savannah River National Laboratory (SRNL) simulant development program is to develop a method to produce a sludge simulant that matches both the chemical and physical characteristics of the HLW without the time, temperature profile, chemical or radiation exposure of that of the real waste. Several different approaches have been taken historically toward preparing simulated waste slurries. All of the approaches used in the past dozen years involve some precipitation of the species using similar chemistry to that which formed the radioactive waste solids in the tank farm. All of the approaches add certain chemical species as commercially available insoluble solid compounds. The number of species introduced in this manner, however, has varied widely. All of the simulant preparation approaches make the simulated aqueous phase by adding the appropriate ratios of various sodium salts. The simulant preparation sequence generally starts with an acidic pH and ends up with a caustic pH (typically in the 10-12 range). The current method for making sludge simulant involves the use of a temperature controlled continuously stirred tank reactor (CSTR

  14. Friction Stir Weld Application and Tooling Design for the Multi-purpose Crew Vehicle Stage Adapter

    Science.gov (United States)

    Alcorn, John

    2013-01-01

    The Multi-Purpose Crew Vehicle (MPCV), commonly known as the Orion capsule, is planned to be the United States' next manned spacecraft for missions beyond low earth orbit. Following the cancellation of the Constellation program and creation of SLS (Space Launch System), the need arose for the MPCV to utilize the Delta IV Heavy rocket for a test launch scheduled for 2014 instead of the previously planned Ares I rocket. As a result, an adapter (MSA) must be used in conjunction with the MPCV to account for the variation in diameter of the launch vehicles; 5.5 meters down to 5.0 meters. Prior to ight article fabrication, a path nder (test article) will be fabricated to ne tune the associated manufacturing processes. The adapter will be comprised of an aluminum frustum (partial cone) that employs isogrid technology and circumferential rings on each end. The frustum will be fabricated by friction stir welding (FSW) three individual panels together on a Vertical Weld Tool (VWT) at NASA Marshall Space Flight Center. Subsequently, each circumferential ring will be friction stir welded to the frustum using a Robotic Weld Tool (RWT). The irregular geometry and large mass of the MSA require that extensive tooling preparation be put into support structures for the friction stir weld. The tooling on the VWT will be comprised of a set of conveyors mounted on pre-existing stanchions so that the MSA will have the ability to be rotated after each of the three friction stir welds. The tooling requirements to friction stir weld the rings with the RWT are somewhat more demanding. To support the mass of the MSA and resist the load of the weld tool, a system of mandrels will be mounted to stanchions and assembled in a circle. The goal of the paper will be to explain the design, fabrication, and assembly of the tooling, to explain the use of friction stir welding on the MSA path nder, and also to discuss the lessons learned and modi cations made in preparation for ight article fabrication

  15. PRELIMINARY DESIGN OF OSCILLATORY FLOW BIODIESEL REACTOR FOR CONTINUOUS BIODIESEL PRODUCTION FROM JATROPHA TRIGLYCERIDES

    OpenAIRE

    AZHARI T. I. MOHD. GHAZI; M. F. M. GUNAM RESUL; R. YUNUS; T. C. SHEAN YAW

    2008-01-01

    The concept of a continuous process in producing biodiesel from jatropha oil by using an Oscillatory Flow Biodiesel Reactor (OFBR) is discussed in this paper. It has been recognized that the batch stirred reactor is a primary mode used in the synthesis of biodiesel. However, pulsatile flow has been extensively researcehed and the fundamental principles have been successfully developed upon which its hydrodynamics are based. Oscillatory flow biodiesel reactor offers precise control of mixing b...

  16. The Effect of Effluent Recirculation in a Semi-Continuous Two-Stage Anaerobic Digestion System

    OpenAIRE

    Karthik Rajendran; Azam Jeihanipour; Taherzadeh, Mohammad J.; Solmaz Aslanzadeh

    2013-01-01

    The effect of recirculation in increasing organic loading rate (OLR) and decreasing hydraulic retention time (HRT) in a semi-continuous two-stage anaerobic digestion system using stirred tank reactor (CSTR) and an upflow anaerobic sludge bed (UASB) was evaluated. Two-parallel processes were in operation for 100 days, one with recirculation (closed system) and the other without recirculation (open system). For this purpose, two structurally different carbohydrate-based substrates were used; st...

  17. Effect of ultrasonic stirring on temperature distribution and grain refinement in Al- 1.65% Si alloy melt

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A series of experiments were conducted for Al-1.65%Si (mass fraction) alloy melt to study the formation of grain refining structure with ultrasonic stirring. The cooling curves of ingots with ultrasonic were measured and compared with those without ultrasonic. At the same time, the effect of the time of ultrasonic stirring on solidification structure of ingots was investigated. The influence of ultrasonic on the grain-refining efficiency of ingots was analyzed. In order to well understand the melts behavior under ultrasonic, by using ammonium chloride solution, the simulation experiment was carried out and the temperature distribution in ingot with or without ultrasonic was compared. The results indicate that the ultrasonic reduces the temperature inhomogeneity of melt, i.e.the ultrasonic helps to homogenize the melt temperature. The effect of stirring and heat generation in ingot start to occur with increasing the time of ultrasonic stirring.

  18. A Study of Friction Stir Welded 2195 Al-Li Alloy by the Scanning Reference Electrode Technique

    Science.gov (United States)

    Donford, M. D.; Ding, R. J.

    1998-01-01

    A study of the corrosion of friction stir welded 2195 Al-Li alloy has been carried out using the scanning reference electrode technique (SRET). The results are compared to those obtained from a study of heterogeneously welded samples.

  19. HEAT INPUT AND POST WELD HEAT TREATMENT EFFECTS ON REDUCED-ACTIVATION FERRITIC/MARTENSITIC STEEL FRICTION STIR WELDS

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Wei [ORNL; Chen, Gaoqiang [ORNL; Chen, Jian [ORNL; Yu, Xinghua [ORNL; Frederick, David Alan [ORNL; Feng, Zhili [ORNL

    2015-01-01

    Reduced-activation ferritic/martensitic (RAFM) steels are an important class of structural materials for fusion reactor internals developed in recent years because of their improved irradiation resistance. However, they can suffer from welding induced property degradations. In this paper, a solid phase joining technology friction stir welding (FSW) was adopted to join a RAFM steel Eurofer 97 and different FSW parameters/heat input were chosen to produce welds. FSW response parameters, joint microstructures and microhardness were investigated to reveal relationships among welding heat input, weld structure characterization and mechanical properties. In general, FSW heat input results in high hardness inside the stir zone mostly due to a martensitic transformation. It is possible to produce friction stir welds similar to but not with exactly the same base metal hardness when using low power input because of other hardening mechanisms. Further, post weld heat treatment (PWHT) is a very effective way to reduce FSW stir zone hardness values.

  20. Modeling the Effects of Tool Shoulder and Probe Profile Geometries on Friction Stirred Aluminum Welds Using Response Surface Methodology

    Institute of Scientific and Technical Information of China (English)

    H.K.Mohanty; M.M.Mahapatra; P.Kumar; P.Biswas; N.R.Mandal

    2012-01-01

    The present paper discusses the modeling of tool geometry effects on the friction stir aluminum welds using response surface methodology.The friction stir welding tools were designed with different shoulder and tool probe geometries based on a design matrix.The matrix for the tool designing was made for three types of tools,based on three types of probes,with three levels each for defining the shoulder surface type and probe profile geometries.Then,the effects of tool shoulder and probe geometries on friction stirred aluminum welds were experimentally investigated with respect to weld strength,weld cross section area,grain size of weld and grain size of thermo-mechanically affected zone.These effects were modeled using multiple and response surface regression analysis.The response surface regression modeling were found to be appropriate for defining the friction stir weldment characteristics.

  1. Control of Structure in Conventional Friction Stir Welds through a Kinematic Theory of Metal Flow

    Science.gov (United States)

    Rubisoff, H.A.; Schneider, J.A.; Nunes, A.C.

    2009-01-01

    In friction stir welding (FSW), a rotating pin is translated along a weld seam so as to stir the sides of the seam together. Metal is prevented from flowing up the pin, which would result in plowing/cutting instead of welding, by a shoulder on the pin. In conventional FSW, the weld metal rests on an "anvil", which supports the heavy "plunge" load on the tool. In this study, both embedded tungsten wires along and copper plating on the faying surfaces were used to trace the flow of AA2219 weld metal around the C-FSW tool. The effect of tool rotational speed, travel speed, plunge load, and pin thread pitch on the resulting weld metal flow was evaluated. Plan, longitudinal, and transverse section x-ray radiographs were examined to trace the metal flow paths. The results are interpreted in terms of a kinematic theory of metal flow in FSW.

  2. Effect of Process Parameters of Friction Stir Welded Joint for Similar Aluminium Alloys H30

    Directory of Open Access Journals (Sweden)

    Vanita S. Thete

    2015-05-01

    Full Text Available In this paper the effect of process parameters of friction stir welded joint for similar aluminium alloys H30 was studied. Taper cylindrical with three flutes all made of High speed steel was used for the friction stir welding (FSW aluminium alloy H30 and the tensile test of the welded joint were tested by universal testing method. The optimization done using detailed mathematical model is simulated by Minitab17. In this investigation, an effective approach based on Taguchi method, has been developed to determine the optimum conditions leading to higher tensile strength. Experiments were conducted on varying rotational speed, transverse speed, and axial force using L9 orthogonal array of Taguchi method. The present study aims at optimizing process parameters to achieve high tensile strength.

  3. Microstructures and Mechanical Properties of Friction Stir Spot Welded Aluminum Alloy AA2014

    Science.gov (United States)

    Babu, S.; Sankar, V. S.; Janaki Ram, G. D.; Venkitakrishnan, P. V.; Madhusudhan Reddy, G.; Prasad Rao, K.

    2013-01-01

    Friction stir spot welding (FSSW) is a relatively recent development, which can provide a superior alternative to resistance spot welding and riveting for fabrication of aluminum sheet metal structures. In the current work, FSSW experiments were conducted in 3-mm thick sheets of aluminum alloy 2014 in T4 and T6 conditions, with and without Alclad layers. The effects of tool geometry and welding process parameters on joint formation were investigated. A good correlation between process parameters, bond width, hook height, joint strength, and fracture mode was observed. The presence of Alclad layers and the base metal temper condition were found to have no major effect on joint formation and joint strength. Friction stir spot welds produced under optimum conditions were found to be superior to riveted joints in lap-shear and cross-tension tests. The prospects of FSSW in aluminum sheet metal fabrication are discussed.

  4. Metallurgical Evaluation of AZ31B-H24 Magnesium Alloy Friction Stir Welds

    Science.gov (United States)

    Pareek, M.; Polar, A.; Rumiche, F.; Indacochea, J. E.

    2007-10-01

    Friction Stir welding of 3.175 mm (0.125 in.) thick plates of AZ31-H24 magnesium alloy was performed using several travel velocities and tool-rotation speeds. After production the welds were cross-sectioned and a metallurgical characterization was performed using optical microscopy, and scanning electron microscopy. Assessment of the weld nugget or “stirred zone” shows evidence of dynamic recrystallization and the start of grain growth in some spots of this region compared to the parent metal. Recrystallization was identified in the thermomechanically affected zone (TAZ) as well. The mechanical properties of the weld are correlated with the corresponding microstructures present in the weld nugget and TMAZ. Corrosion resistance of the weld was assessed using Electrochemical Impedance Spectroscopy (EIS) techniques and immersion tests in a corrosive environment; it showed better corrosion resistance than the base metal.

  5. Mechanism of Off—Bottom Suspension of Solid Particles in a Mechanical Stirred Tank

    Institute of Scientific and Technical Information of China (English)

    BAOYuyun; HUANGXiongbin; 等

    2002-01-01

    The minimum fluid velocity to maintain particles just suspended was deduced,and the theoretical analysis shows that the minimum velocity is influenced by the properties of the solid and liquid,not by the operational conditions. For justification,the local minimum velocity at the bottom of the tank was measured by a bi-electrode conductivity probe,in a square-sectioned stirred tank (0.75m×0.75m×1.0m) with the glass beads-water system. The experiments showed that the fluid velocities for the same suspension state were identical despite that the power dissipated per unit mass was not the same under different configuration and operation.Both theoretical analysis and experimental results indicate that the off-bottom suspension is controlled by the local fluid flow over the bottom of the stirred tank.

  6. EFFECT OF TOOL FEATURE ON THE JOINT STRENGTH OF DISSIMILAR FRICTION STIR LAP WELDS

    Energy Technology Data Exchange (ETDEWEB)

    Jana, Saumyadeep; Hovanski, Yuri; Grant, Glenn J.; Mattlin, Karl F.

    2011-04-25

    Several variations of friction stir tools were used to investigate the effects on the joint strengths of dissimilar friction stir lap welds. In the present lap weld configuration the top sheet was a 2.32 mm thick Mg (AZ 31) alloy. The bottom sheet consisted of two different steels, a (i) 0.8 mm thick electro-galvanized (EG) mild steel, or a (ii) 1.5 mm thick hot dip galvanized (HDG) high strength low alloy (HSLA) steel. Initially the tool shape was modified to accommodate the material, at which point the tool geometry was fixed. With a fixed tool geometry an additional feature was added to the pin bottom on one of the tools by incorporating a short hard insert, which would act as a stronger bottom sheet cutter. The effects of such modification on the unguided lap shear strength, and associated microstructural changes are discussed in this study.

  7. Strengthening Mechanisms in NiAl Bronze: Hot Deformation by Rolling and Friction-Stir Processing

    Science.gov (United States)

    Menon, Sarath K.; Pierce, Frank A.; Rosemark, Brian P.; Oh-Ishi, Keiichiro; Swaminathan, Srinivasan; McNelley, Terry R.

    2012-10-01

    Microstructures produced by isothermal hot rolling of a NiAl bronze material were evaluated by quantitative microscopy methods and parameters describing the contributions of precipitate dispersions, grain size, solute content, and dislocation density to the yield strengths of the individual constituents of microstructure were determined. Models for the strengths of the individual constituents were combined to predict the temperature dependence of the yield strength as a function of hot rolling temperature, and the prediction was found to be in good agreement with measured yield strengths. The models were applied to microstructures in a stir zone produced by multipass friction-stir processing (FSP) and, again, found to predict measured yield strengths with high accuracy. Such models may aid in assessing the role of microstructure gradients produced during FSP and other processes.

  8. Hydrogen and helium recycling from stirred liquid lithium under steady state plasma bombardment

    Energy Technology Data Exchange (ETDEWEB)

    Hirooka, Yoshi, E-mail: hirooka.yoshihiko@nifs.ac.jp [National Institute for Fusion Science, 322-6 Oroshi, Toki, Gifu 509-5292 (Japan); The Graduate School for Advanced Studies, 322-6 Oroshi, Toki, Gifu 509-5292 (Japan); Zhou, Haishan [The Graduate School for Advanced Studies, 322-6 Oroshi, Toki, Gifu 509-5292 (Japan); Ono, Masa [Princeton Plasma Physics Laboratory, PO Box 451, Princeton, NJ 08543 (United States)

    2014-12-15

    For improved core performance via edge plasma-wall boundary control, solid and liquid lithium has been used as a plasma-facing material in a number of confinement experiments over the past several decades. Unfortunately, it is unavoidable that lithium is saturated in the surface region with implanted hydrogenic species as well as oxygen-containing impurities. For steady state operation, a flowing liquid lithium divertor with forced convection would probably be required. In the present work, the effects of liquid stirring to simulate forced convection have been investigated on the behavior of hydrogen and helium recycling from molten lithium at temperatures up to ∼350 °C. Data indicate that liquid stirring reactivates hydrogen pumping via surface de-saturation and/or uncovering impurity films, but can also induce helium release via surface temperature change.

  9. A Review: Welding Of Dissimilar Metal Alloys by Laser Beam Welding & Friction Stir Welding Techniques

    Directory of Open Access Journals (Sweden)

    Ms. Deepika Harwani

    2014-12-01

    Full Text Available Welding of dissimilar metals has attracted attention of the researchers worldwide, owing to its many advantages and challenges. There is no denial in the fact that dissimilar welded joints offer more flexibility in the design and production of the commercial and industrial components. Many welding techniques have been analyzed to join dissimilar metal combinations. The objective of this paper is to review two such techniques – Laser welding and Friction stir welding. Laser beam welding, a high power density and low energy-input process, employs a laser beam to produce welds of dissimilar materials. Friction stir welding, a solid-state joining process, is also successfully used in dissimilar welding applications like aerospace and ship building industries. This paper summarizes the trends and advances of these two welding processes in the field of dissimilar welding. Future aspects of the study are also discussed.

  10. Experimental Investigation and Prediction of Mechanical Properties of Friction Stir Welded Aluminium Metal Matrix Composite Plates

    Directory of Open Access Journals (Sweden)

    Yahya BOZKURT

    2012-12-01

    Full Text Available Friction stir welding (FSW is a relatively contemporary solid state welding process and has been employed in aerospace, railway, automotive and marine industries for joining of aluminum, magnesium, zinc, titanium, copper alloys, dissimilar metals and thermoplastics. The FSW process parameters such as tool rotation speed, tool traverse speed and tilt angle play an important role in deciding the joining quality. The present study defines the effect of FSW process on the tensile properties of the AA2124/SiC/25p metal matrix composite (MMC plates. Obtained results showed that the joint efficiency decreases by increasing the tool traverse speed while tool rotation speed was kept constant. Second contribution of this study is the application of decision tree technique to predict the tensile properties of friction stir welded MMC plates. It is seen that methodology can be applied with great accuracy.DOI: http://dx.doi.org/10.5755/j01.ms.18.4.3092

  11. A review of literature from the First International Conference on Friction Stir Welding

    Energy Technology Data Exchange (ETDEWEB)

    Bowyer, W.H. [Meadow End Farm, Farnham (United Kingdom)

    2000-06-15

    The papers from the first international conference on Friction Stir Welding (FSW) have been reviewed. Taken together the papers provide a very optimistic picture for the development and application of friction stir welding in general and to the case of the copper canister in particular. Whilst a considerable development effort is in progress the process has been industrialised for joining of aluminium sheet and it is accepted by Lloyds register for this purpose. Development of procedures and equipment to weld thicker materials and a wider range of materials is progressing ahead of the research activity to aid the understanding of the process at this stage. Nevertheless, well-established weld assessment procedures are being applied to experimental welds with very encouraging results. Summaries of the key papers are presented in an appendix.

  12. Microstructure and corrosion property of AZ61 magnesium alloy by electromagnetic stirring

    Institute of Scientific and Technical Information of China (English)

    FANG Can-feng; ZHANG Xing-guo; JI Shou-hua; JIN Jun-ze; CHANG Yu-bao

    2005-01-01

    The influence of permanent-magnet-driven stirring during solidification on the microstructure and corrosion property of AZ61 magnesium alloy was investigated. The corrosion behaviour of AZ61 was studied in 3.5mol/L NaCl by measuring electrochemical polarization. The results show that the permanent-magnet stirring refines the microstructure of AZ61 magnesium alloy, which improves the precipitation amount and distribution uniformity of β phase and decreases the content of hydrogen, but it has less influence on the distribution uniformity of Zn. The change of precipitation amount of β phase influences the corrosive nature of the matrix, and it has no direct proportion with the corrosion resistance of the matrix.

  13. EFFECTS OF LINEAR ELECTROMAGNETIC STIRRING ON THE SOLIDIFICATION STRUCTURE OF BILLET

    Institute of Scientific and Technical Information of China (English)

    H.L. Zhang; E.G. Wang; G.L. Jia; J.C. He

    2001-01-01

    The effects of linear electromagnetic stirring (EMS) on the solidification steacture of billet were investigated by experiments, and the electromagnetic fields and flow fields during the stirring process were analyzed by numerical simulation. The results show that the billet of almost 100% equiaxed grains can be obtained by applying linear EMS at the maximum intensity of 1414A.Hz1/2, while the maximum electromagnetic force and the maximum velocity in the molten steel are 6386N-m-3 and 0.22m.s-1,respectively. It is presented that the pulsating electromagnetic force perpendicular to the movement of the molten steel, is an important factor of increasing the equiaxed zone ratio in the solidification structure, which further prevents the appearance of white band and internal defects.

  14. Homogeneity of Mechanical Properties of Underwater Friction Stir Welded 2219-T6 Aluminum Alloy

    Science.gov (United States)

    Liu, H. J.; Zhang, H. J.; Yu, L.

    2011-11-01

    Underwater friction stir welding (FSW) has been demonstrated to be available for the improvement in tensile strength of normal FSW joints. In order to illuminate the intrinsic reason for strength improvement through underwater FSW, a 2219 aluminum alloy was underwater friction stir welded and the homogeneity of mechanical properties of the joint was investigated by dividing the joint into three layers. The results indicate that the tensile strength of the three layers of the joint is all improved by underwater FSW, furthermore, the middle and lower layers have larger extent of strength improvement than the upper layer, leading to an increase in the homogeneity of mechanical properties of the joint. The minimum hardness value of each layer, especially the middle and lower layers, is improved under the integral water cooling effect, which is the intrinsic reason for the strength improvement of underwater joint.

  15. Comparison of corrosion behaviour of friction stir processed and laser melted AA 2219 aluminium alloy

    International Nuclear Information System (INIS)

    Highlights: → Poor corrosion resistance of AA 2219 can be improved by surface treatments. → FSP and LM leads to dissolution of second phase particles. → No literature available on comparison of corrosion behaviour after FSP and LM. → The study implies FSP is as good as LM in improving the corrosion resistance of AA 2219. -- Abstract: Dissolution of second phase particles (CuAl2) present in AA 2219 aluminium improves the corrosion resistance of the alloy. Two surface treatment techniques, viz., solid state friction stir processing and fusion based laser melting lead to the reduction in CuAl2 content and the effect of these processes on the corrosion behaviour of the alloy is compared in this study. Potentiodynamic polarization and electrochemical impedance spectroscopy tests were carried out to compare corrosion behaviour. The corrosion resistance achieved by friction stir processing is comparable to that obtained by the laser melting technique.

  16. Microstructure and anisotropic mechanical behavior of friction stir welded AA2024 alloy sheets

    International Nuclear Information System (INIS)

    The anisotropic mechanical properties of friction stir welded (FSW) AA2024-T3 alloy joints were investigated based on the uniaxial tensile tests. The joint microstructure was examined by using electron back-scattered diffraction and transmission electron microscope. Results show that the evident anisotropic failure and yielding are present in the FSW joints. With the increase of loading angle from 0° to 90° the ultimate tensile strength and elongation of the specimens consistently decrease, or at first decrease and then increase, depending on the FSW process parameters. The specimen cut from the weld direction, i.e. a loading angle of 0°, exhibits the highest strength and elongation. - Highlights: • Microstructure and anisotropy of friction stir welded joints were studied. • The evident anisotropic failure and yielding are present in joints. • The lowest yield stress and UTS are at 45° and 60° loadings, respectively. • Rotation speed heavily impact on the anisotropy of joints

  17. Characterization And Study of Friction Stir Welding of AA6101 Aluminum Alloy

    Directory of Open Access Journals (Sweden)

    S. K. Aditya

    2016-05-01

    Full Text Available Friction stir welding (FSW combines two plates by frictional heating at the interface with the localized plastic deformation within the material. In friction stir welding heat is generated by the friction between rotating tool shoulder and the plates to be welded. The heat thus generated results in thermal softening of the material. The softened material is then forced to flow by the translation of the tool from the front to the back of the pin. There it cools, consolidates and results in joint formation. In the process, strength of the joint and percentage elongation varies from the parent material. AA6101 is equivalent to AA 6061 and AA6063. At present AA6101 is used by the electrical industries only. A detailed experimental study has been done on AA 6101 to its utility as an Aluminum alloy for structural fabrication

  18. The Mechanical Behavior of Friction-Stir Spot Welded Aluminum Alloys

    Science.gov (United States)

    Güler, Hande

    2014-10-01

    Aluminum and alloys are widely used in the automotive industry due to the light weight, good formability, and malleability. Spot welding is the most commonly used joining method of these materials, but the high current requirements and the inconsistent quality of the final welds make this process unsuitable. An alternative welding technique, the friction-stir spot welding process, can also be successfully used in joining of aluminum and alloys. In this study, 1-mm-thick AA5754 Al-alloy plates in the H-111 temper conditions were joined by friction-stir spot welding using two different weld parameters such as tool rotational speed and dwell time. Mechanical properties of the joints were obtained with extensive hardness measurements and tensile shear tests. The effect of these parameters on the failure modes of welded joints was also determined.

  19. A Study on Friction Stir Welding of 12mm Thick Aluminum Alloy Plates

    Institute of Scientific and Technical Information of China (English)

    Deepati Anil Kumar; Pankaj Biswas; Sujoy Tikader; M. M. Mahapatra; N. R. Mandal

    2013-01-01

    Most of the investigations regarding friction stir welding (FSW) of aluminum alloy plates have been limited to about 5 to 6 mm thick plates. In prior work conducted the various aspects concerning the process parameters and the FSW tool geometry were studied utilizing friction stir welding of 12 mm thick commercial grade aluminum alloy. Two different simple-to-manufacture tool geometries were used. The effect of varying welding parameters and dwell time of FSW tool on mechanical properties and weld quality was examined. It was observed that in order to achieve a defect free welding on such thick aluminum alloy plates, tool having trapezoidal pin geometry was suitable. Adequate tensile strength and ductility can be achieved utilizing a combination of high tool rotational speed of about 2000 r/min and low speed of welding around 28 mm/min. At very low and high dwell time the ductility of welded joints are reduced significantly.

  20. Thermal Management in Friction-Stir Welding of Precipitation-Hardening Aluminum Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Upadhyay, Piyush; Reynolds, Anthony

    2015-05-25

    Process design and implementation in FSW is mostly dependent on empirical information gathered through experience. Basic science of friction stir welding and processing can only be complete when fundamental interrelationships between process control parameters and response variables and resulting weld microstructure and properties are established to a reasonable extent. It is known that primary process control parameters like tool rotation and translation rate and forge axis force have complicated and interactive relationships to the process response variables such as peak temperature, time at temperature etc. Of primary influence to the other process response parameters are temperature and its gradient at the deformation and heat affected zones. Through review of pertinent works in the literature and some experimental results from boundary condition work performed in precipitation hardening aluminum alloys this paper will partially elucidate the nature and effects of temperature transients caused by variation of thermal boundaries in Friction Stir Welding.