Quench Temperature Research Articles

Rheological properties of polybutadiene/polyisoprene blend in the unstable and metastable regions under oscillatory shear

The rheological properties of polybutadiene (PB)/polyisoprene (PI) in the unstable and metastable regions under oscillatory shear flow has been studied. Based on the shear quench experiment, it showed that the time dependent storage modulus G′ initially increased and then decreased with time in the unstable region. The concentration fluctuation led to the increasing part and the coarsening of the bicontinuous structure led to the decreasing of the storage modulus. The rheological response of the nucleation/growth in the metastable region was similar to that of spinodal decomposition. The fluctuation-assisted nucleation theory proposed by Balsara et al. was similar to the spinodal decomposition mechanism, which led to the similar rheological response. However, the continuous nucleation led to the slow growth and the almost linear decayed rheological curve, which was different from that in the unstable region. According to this theory, the relative nucleation rate on the early stage of nucleation could be calculated, which increased exponentially with the reciprocal of quench temperature in the metastable region. The spinodal point under oscillatory shear was also determined by the difference of maximum value of the storage modulus and the bulk modulus.

Effects of cooling temperature and aging treatment on the morphology of nano‐ and micro‐porous poly(ethylene‐co‐vinyl alcohol) membranes by thermal induced phase separation method

ABSTRACTPoly(ethylene‐co‐vinyl alcohol) (EVOH 32) / 1,3‐propanediol mixtures are processed by thermally induced phase separation for the formation of porous membranes. The crystallization line was determined both by the cloud‐point and DSC methods. Two precursor solution compositions, four quench temperatures and various aging times were explored. It is found possible to generate both polymer‐crystallization controlled morphologies (for high quenches and/or sufficiently aged dopes), especially globular microporous ones, and novel nano‐scale porous morphologies dominated by intra‐binodal phase separation (for low quenches and limited or no precursor solution aging). Structural characterization of the membranes was accomplished via application of scanning electron microscopy and wide angle X‐ray diffraction. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40374.

On Various Aspects of Decomposition of Austenite in a High-Silicon Steel During Quenching and Partitioning

Using a Gleeble thermomechanical simulator, a high-silicon steel (Fe-0.2C-1.5Si-2.0Mn-0.6Cr) was laboratory hot-rolled, re-austenitized, quenched into the Ms–Mf range, retaining 15 to 40 pct austenite at the quench stop temperature (TQ), and annealed for 10 to 1000 seconds at or above TQ in order to better understand the mechanisms operating during partitioning. Dilatometer measurements, transmission electron microscopy, and calculations showed that besides carbon partitioning, isothermal martensite and bainite form at the partitioning temperature. While isothermal martensite formation starts almost immediately after quenching with the rate of volume expansion dropping all the time, the beginning of bainite formation is marked by a sudden increase in the rate of expansion. The extent of its formation depends on the partitioning temperature following TTT diagram predictions. At the highest partitioning temperatures martensite tempering competes with partitioning. Small fractions of bainite and high-carbon martensite formed on cooling from the partitioning temperature. The average carbon content of the austenite retained at room temperature as determined from XRD measurements was close to the carbon content estimated from the Ms temperature of the martensite formed during the final cooling.

Computer-aided mathematical modeling and numerical simulation and theoretical analysis of the polypropylene polymer air drawing in spunbonding nonwoven process

In this article, as a nonlinear mathematical problem, the air-drawing model and the air jet flow field model of the polymer during spunbonding process are also presented, because the continuous filament fiber not always occurs in the spunbonding process, therefore, there exists the filament fiber breakage, the broken fibers occur in the flow field of spunbonding process is a two-phase flow problem, we suggested a new model called the sphere–spring model that can best described the broken fibers movement features. At the same time, the air-drawing model of the polypropylene polymer in a spunbonding process is presented and solved by introducing the numerical computation results of the air jet flow field of aerodynamic device. The model's predictions of the filament fiber diameters, crystallinities, and birefringences are coincided well with the experimental data. The effects of the processing parameters on the filament fiber diameter are discussed. A lower polymer throughput rate, lower quench air temperature, higher polymer melt initial temperature, higher air initial temperature, higher air initial speed, medium smaller venturi gap, higher air suction speed, higher quench air pressure, higher air suction speed, higher extrusion temperature, higher quench air pressure, higher cooling air temperature, and so on can all produce finer filament fiber. The results show great prospects for this research in the field of computer-assisted design of spunbonding technology. POLYM. ENG. SCI., 54:481–492, 2014. © 2013 Society of Plastics Engineers

Designing a Novel DQ&P Process through Physical Simulation Studies

This study presents the use of physical and laboratory rolling simulations for the development of a novel direct quenching and partitioning (DQ&P) process for the development of tough ductile ultra-high strength structural steels with yield strengths ~1100 MPa and reasonable ductility and toughness. Suitable compositions were designed based on high silicon and/or aluminium content. The DQ&P parameters were established with the aid of physical simulation on a Gleeble simulator. Two types of dilatation tests were carried out: with or without prior straining in the no-recrystallization regime to establish the influence of controlled deformation on subsequent transformation structures and properties. Based on dilatation results, simulated rolling trials were conducted on a laboratory rolling mill and the rolled samples were direct quenched in water to the desired quench stop temperatures followed by partitioning in a furnace held at this temperature. Detailed microstructural examination confirmed that the desired martensite-austenite microstructures were achieved. Besides high strengths, the ductility (including uniform elongation) and impact toughness were quite improved in comparison to that of a direct quenched carbon steel in the same strength class.

MuCool Superconducting Solenoid Quench Simulations and Test Stand at FNAL

Fabrication and preparation for test of the MuCool superconducting solenoid are now in progress. The solenoid's passive quench protection system is based on cold diodes and shunt resistors. The solenoid does not have heaters, and quench propagation relies on the superconductor quenching and the subsequent “quench back” effect caused by eddy currents in the coil's Al mandrel. The solenoid has a very large inductance of ~600 H and the stored energy is 100% dissipated into the cold mass during a quench. This makes the solenoid protection a challenging task. This paper presents the quench analysis of the solenoid based on a 3-D FEA solution of the coupled transient electromagnetic and thermal properties during the quench. The simulations used the Vector Fields QUENCH code. A new test facility, the solenoid test stand (STS), is being built at Fermilab to test these coils. One of the critical issues regarding the STS is the fringe field produced by the magnet under test, which interacts with the surrounding equipment. In this paper, we present the stray-field analysis and the corresponding magnetic forces. The STS includes a sophisticated DAQ system to carefully monitor quench events and temperatures.

Design of electronic measurement and quench detection equipment for the Current Lead Test facility Karlsruhe (CuLTKa)

The Current Lead Test facility Karlsruhe (CuLTKa) is under construction at the Karlsruhe Institute of Technology (KIT) to perform acceptance tests of high temperature superconductor (HTS) current leads (CL). CuLTKa is in progress and present planning expects the completion in 2013. The data acquisition system is based on a modular design with electronic measurement and monitoring equipment covering a test voltage of 50kV DC against ground. It provides plug-in units which enable temperature and voltage measurement at high voltage potential and in addition quench detection units which detect a loss of superconductivity reliably and quickly to avoid damage of the superconducting device under test. Prototype units for quench detection, temperature and voltage measurement have been successfully tested. Six temperature measurement units are already in use in the KIT test facility TOSKA and operated reliably during the acceptance tests of the HTS current leads for Wendelstein 7-X (W7-X) in 2011/2012. CuLTKa will be used first for 26 current leads which will be built in KIT for the fusion experiment JT-60SA. The present paper gives an overview of the design of the electronic measurement and quench detection equipment.

Quenching and Partitioning (Q&P) Processing of Martensitic Stainless Steels

Austenite was stabilized in the martensitic stainless steel grade AISI 420 by means of quenching and partitioning (Q&P) processing. The effects of quenching temperature on the microstructure and mechanical properties were investigated. The specimens processed at low quench temperatures (regime I) had a microstructure consisting of tempered martensite and retained austenite. At high quench temperatures (regime II), fresh martensite was present too. The highest austenite fraction of about 0.35 was obtained at the quench temperature delineating regimes I and II. The amount of carbon in retained austenite increased as the quench temperature decreased. The carbon level of austenite was, however, much lower than the carbon concentrations expected from full partitioning assumption. This was mainly due to the extensive cementite formation in the partitioning step. Stabilization of austenite by Q&P processing was found not to be purely chemical. Austenite stabilization was also assisted by locking, because of local carbon enrichment, of potential martensite nucleation sites in the austenite/martensite boundaries and in austenite defects. The importance of the latter stabilization mechanism increased at higher martensite fractions. According to the tensile test results, the Q&P processed specimen with the highest austenite fraction was not associated with the best combination of strength and ductility. The mechanical stability of austenite was found to increase with its carbon concentration being the highest at the lowest quench temperature. The thermal stability, on the other hand, was almost inversely proportional to the retained austenite fraction, being low at intermediate quench temperatures where the retained austenite fraction was high.

Phase-field simulation of thermally induced spinodal decomposition in polymer blends

A phase-field simulation of thermally induced phase separation with various initial average concentrations under different quench depths is systematically carried out in this paper. The resultant morphology of the phase-separated materials is determined by the quench temperature and the average concentration. A detailed understanding of the effects of quench depth during the phase separation process of spinodal decomposition (SD) is presented. The coarsening mechanism with various average concentrations is investigated. In addition, hydrodynamic effects play an important role in phase separation in liquid immiscible alloys. Therefore, a systematic comparison between systems with and without hydrodynamic effects under different conditions is also considered. The model developed and the results obtained could shed light on using SD in immiscible polymer systems to obtain desired nanostructures for advanced applications.

Understanding coal/hydrocarbons pyrolysis in thermal plasma reactors by thermodynamic analysis

This work aims to improve the understanding on the principles of coal/hydrocarbons pyrolysis to acetylene (C2H2) in thermal plasma reactors by thermodynamic analysis in association with the practical operation experience at lab- and pilot-plant scale reactors. The thermodynamic predictions agree well with the experimental data in the literature and the representative data in megawatts plasma reactors. Accordingly, it is summarized that the effective mass ratio of C/H (RC/H) in the gas phase and the quench temperature are the two key factors influencing the reactor performance. The C2H2 concentration is very sensitive to the quench temperature varying around 1500–1800 K, which is therefore suggested to maintain above 1800 K for a better yield of C2H2. Higher effective mass ratio of C/H would have a more positive effect on the reactor performance in terms of C2H2 concentration. The additional input of hydrocarbons to the reaction system provides an effective means to flexibly adjust the performance of the plasma reactor for the raised RC/H. The additional water/steam helps to inhibit coking on the wall but reduce the RC/H, leading to the trend from thermal pyrolysis to gasification process.

Experimental Study of Liquid Hydrocarbons Pyrolysis to Acetylene in H2/Ar Plasma

Liquid hydrocarbons including n-hexane, cyclohexane and toluene are pyrolyzed in H2/Ar plasma to investigate the effects of feedstock properties and key operating conditions (e.g., the feedstock specific input power and residence time) on the reaction performance. The experiments verify that the non-aromatic hydrocarbons show better chemical reactivity than partially aromatic substances. Meanwhile, the straight-chain alkanes and cycloalkanes have better yields of ethylene during the pyrolysis. The results also demonstrate that the pyrolysis reactions are almost completed within the first 0.8 ms in Ar/H2 plasma independent of the feed substances (i.e., liquid hydrocarbons), where the increased feedstock specific input power enhances the reactant conversions and correspondingly raises the yields of acetylene. At a feedstock specific input power of 4.7 × 104 kJ/kg, the n-hexane conversion is over 90 % and the yield of acetylene reaches 70 %. In addition, when using n-hexane as the feedstock, very little coke is formed during the course of reaction. Comprehensive comparisons of the current experiments with the data reported in the literature are made to point out the key influencing factors, i.e., the effective mass ratio of C/H (RC/H) in the gaseous phase and the quench temperature. Both two factors would need to be enhanced in order to get a better performance. Finally, the improvements on the specific energy requirement of this process are discussed.

Inhibitory effects of arginine on the aggregation of bovine insulin.

Static and dynamic light scattering were used to investigate the effects of L-arginine, commonly used to inhibit protein aggregation, on the initial aggregation kinetics of solutions of bovine insulin in 20% acetic acid and 0.1 M NaCl as a model system for amyloidosis. Measurements were made as a function of insulin concentration (0.5–2.0 mM), quench temperature (60–85°C), and arginine concentration (10–500 mM). Aggregation kinetics under all conditions had a lag phase, whose duration decreased with increasing temperature and with increasing insulin concentration but which increased by up to a factor of 8 with increasing added arginine. Further, the initial growth rate after the lag phase also slowed by up to a factor of about 20 in the presence of increasing concentrations of arginine. From the temperature dependence of the lag phase duration, we find that the nucleation activation energy doubles from 17 ± 5 to 36 ± 3 kcal/mol in the presence of 500 mM arginine.

Optimization and Test of 120 mm LARP Nb$_{3}$Sn Quadrupole Coils Using Magnetic Mirror Structure

The US-LARP collaboration is developing a new generation of large-aperture high-field quadrupoles based on Nb Sn superconductor for the LHC upgrades. The development and implementation of this new technology involves the fabrication and testing of series of model magnets, coils and other components with various design and processing features. New 120-mm HQ coils made of Rutherford cable, one with an interlayer resistive core, and both with optimized reaction processes, were fabricated and tested using a quadrupole mirror structure under operating conditions similar to those in a real magnet. The coils were instrumented with voltage taps and strain gauges to study the mechanical and quench performance. Quench antenna and temperature gauges were installed in the mirror structure to measure the coil temperature and locate quench origins. This paper presents details of the coil design and fabrication procedures, coil assembly and pre-stress in the quadrupole mirror structure, and coil test results.

How to generate high twin densities in nano-ferroics: Thermal quench and low temperature shear

High domain boundary densities in ferroic nano materials are generated in computer simulation studies by (1) fast quench from a para-elastic into a ferroelastic phase and (2) by shear of small samples at low temperatures inside the stability field of the ferroelastic phase. Quenched samples evolve from tweed to junctions to stripe pattern. In driven systems, no tweed exists and the mesoscopic structure ‘nucleates’ rapidly when a yield stress is surpassed. The nucleated domain patterns are long-lived and change towards the single domain state only when the external strain is further increased.

Reflooding characteristics investigation and predicted models improvement for the pressurized water reactor with the tight lattice core design

The advanced pressurized water reactor with a tight hexagonal lattice core design has its potential to improve uranium utilization. With a smaller pitch-to-diameter ratio (p/d) ranging from 1.05 to 1.20, a major problem of a tight lattice core is the emergency core cooling in a loss-of-coolant accident. The NEPTUN-LWHCR and FLORESTAN reflooding experiments preformed at PSI (Paul Scherrer Institute) and KfK (Kernforschungszentrum Karlsruhe) during the verification period 1985–1990 showed that a LWHCR (light water high conversion reactors) had higher peak cladding temperatures and smaller quench rates than that of a conventional LWR (Rouge and Dreier, 1992; Erbacher and Wiehr, 1988). Furthermore, the existing system codes like RELAP5, CATHARE, TRAC may not be able to simulate the reflooding phase of a LWHCR. In this paper, the characteristics of the reflooding phase of tight lattice cores have been investigated. Then improvements to heat transfer models of precursory cooling have been introduced into RELAP5/MOD3.2. In addition, a new model has been developed to predict the heat release in the vicinity of the quench front. These modifications are assessed using selected tests of NEPTUN-LWHCR and FLORESTAN experiments. Comparisons between the calculated results and measured data indicate that the modified code can predict the peak cladding temperatures and quench temperatures relatively well. While for droplet entrainment prediction, there is still large room for improvement. Further validation is needed for the models proposed in this paper especially for a tight lattice core with a p/d ratio less than 1.10, and more efforts are required to study the droplet distribution and droplet size downstream of the quench front for higher reflooding rate tests (larger than 4.5cm/s).

Thermal shock resistance of polycrystalline cubic boron nitride

Abstract The effect of thermal shock on the flexural strength has been investigated experimentally. It was found that the variation in flexural strength with quench temperature was influenced by the CBN grain size. Polycrystalline material containing small CBN grains showed a discontinuous drop in measured flexural strength above a material dependent critical quench temperature difference, Δ T c . The sharp decrease in measured strength is accompanied by unstable crack propagation. Material containing a significantly larger CBN grain size exhibited a gradual decrease in strength above the critical quench conditions. The experimental observations agreed with an established theory developed for thermal shock of alumina. The theoretically calculated critical temperatures agree well with the observed experimental data for each material when a flaw size equal to the CBN grain size is employed.

The Influential Factors Analysis of Surface Crack Propagation Behavior of ZrB2-20%SiC-10%AlN Ceramic Subjected to Thermal Shock

The indentation-quench method for investigating surface crack propagation has been studied through both experiments and model. The influential factors for surface crack propagation such as specimen thickness, thermal fatigue property, and quench temperature difference (ΔT) and one single specimen being used throughout a whole test ΔTwere surveyed in this paper. Practical results were obtained for ZrB2-20%SiC-10%AlN (ZSA) ultra-high temperature ceramic. The percentage crack growth versus ΔTcurves showed stable crack growth in a relative low ΔTinterval and unstable crack growth above a certain ΔT, and these regimes were sensitive to the thickness. The total stress intensity factor (KI) combining residual stress and thermal stress considering dynamical behavior during the quenching test was calculated by a surface crack theoretical model, the result of calculation was analyzed influential factors and crack propagation .

Quenching and Partitioning of CMnSi Steels Containing Elevated Manganese Levels

AbstractQuenching and partitioning (Q&P) is receiving increased attention as a potential processing route to develop “Third Generation” advanced high strength steel (AHSS) properties. The Q&P process consists of quenching a steel from a reheat temperature to a pre‐determined temperature in the Ms − Mf temperature region followed by a so‐called partitioning treatment at the quench temperature or higher. The present contribution investigates the Q&P response of laboratory‐processed CMnSi alloys with 3 or 5 wt% manganese. Samples were processed at quench temperatures between 70 and 250°C with partitioning temperatures of 400 and 450°C for times up to 100 s. Scanning electron microscopy and X‐ray diffraction were utilized to evaluate the Q&P microstructures. Attractive properties were generated with tensile strength/total elongation combinations such as 1500 MPa and 17%.

CFD modeling of the melt spinning of poly (ethylene terepthalate) at low take-up velocities

In this study, a model was formulated to describe the melt spinning of Poly (ethylene terepthalate) (PET) at different quench air speeds and temperatures, mass throughputs and a low range of take-up velocities. The constitutive equations of the Newtonian model were used for modeling, which assumed the flow of polymer was viscous. To simulate the influence of the process parameters on the melt spinning process, a fiber model was used and coupled with computational fluid dynamics (CFD) calculations of the quench air flow. In the fiber model, energy, momentum and mass balance were solved for the polymer mass flow. The formulation was implemented in the Fluent Continuous Fiber Model. Numerical predictions of the model were compared with experimental data reported in the literature for PET. The take up speed, mass throughput and the temperature of melt spinning were the primary parameters of final fiber properties for both simulation and experimental results. In the simulation results, the effects of take-up speed and mass throughputs were clearly different at high take-up velocities and low mass throughputs because of viscoelastic behavior of polymers in the melt spinning. The Newtonian model was more reasonable for lower take-up speeds and higher mass throughputs. Key words: Melt spinning, poly (ethylene terepthalate), modeling, process parameters.

New routes to food gels and glasses

We describe the possibility to create solid-like protein samples whose structural and mechanical properties can be varied and tailored over an extremely large range in a very controlled way through an arrested spinodal decomposition process. We use aqueous lysozyme solutions as a model globular protein system. A combination of video microscopy, small-angle neutron and X-ray scattering and reverse Monte Carlo modeling is used to characterize the structure of the bicontinuous network with two coexisting phases of a dilute protein solution and a glassy or arrested dense protein backbone at all relevant length scales. Rheological measurements are then used to determine the complex mechanical response of these protein gels as a function of protein concentration and quench temperature. While in particular the origin of the dependence of the mechanical properties on quench depth and concentration is not well understood currently, it seems ultimately connected to the particular bicontinuous structure of the arrested spinodal network created by the interplay between the early stage of a spinodal decomposition and the position of the glass line. We then generalize this behavior and discuss how this could open up new routes to prepare gel-like food systems with adjustable structural and mechanical properties. We present results from a first feasibility study where we use a depletion interaction caused by the addition of small non-adsorbing polymers to suspensions of casein micelles in order to create food gels with tunable structural and mechanical properties through an arrested spinodal decomposition process.