Drawing Temperature Research Articles

Preparation of PVDF/PAR Composites with Piezoelectric Properties by Post-Treatment.

Thermoplastic composites were prepared using poly (vinylidene fluoride) (PVDF) as the matrix with piezoelectric properties and aromatic polyarylate (PAR) as the reinforcing component. The PVDF/PAR conjugate fibers were prepared by melt conjugate spinning. The PVDF/PAR composites were prepared by compression molding of the PVDF/PAR conjugate fiber laminates at various molding temperatures. Drawing and poling post-treatments of the PVDF/PAR composites were performed to increase the β crystalline phase content of the PVDF. The morphologies of the PVDF/PAR composites were observed by scanning electron microscopy, and the tensile properties were tested using an universal testing machine. The crystal structure of the PVDF/PAR composites was confirmed by Fourier transform infrared spectroscopy and X-ray diffraction. The piezoelectric properties were tested using voltmeters and multimeters. The post-treatments enhanced the content of the β crystalline phase of the PVDF matrix, thereby improving the piezoelectric properties of the composites. A molding temperature of 180 °C, drawing temperature of 90 °C, and poling voltage of 12 kV were identified as the optimal conditions for the preparation of the PVDF/PAR composite.

Perspective: Molten core optical fiber fabrication—A route to new materials and applications

The molten core method, whereby a precursor core phase melts at the draw temperature of the cladding glass that encapsulates it, has proven to be a remarkably versatile approach to realize novel optical fibers. Employed globally for both scientific inquiry and practical applications, it is arguably the only approach that leads to long lengths of novel material fiber with both crystalline and glassy cores. This article reviews the history of the process, the ever-broadening range of compositions, the unique applications that have been enabled, and provides a perspective on current challenges and future opportunities.

Modeling and measurement of temperature and draw solution concentration induced water flux increment efficiencies in the forward osmosis membrane process

Water/energy sustainability has initiated strong academic interests in the development of forward osmosis (FO) to produce clean water. High water flux is critical to operate FO efficiently in industrial applications. Operation parameters including draw solution (DS) concentration and temperature highly affect water flux. As such, we investigated impacts of DS concentration and temperature on water fluxes of one commercial thin-film composite FO membrane via theoretical analysis and experimental measurement. Solution-diffusion model was revised by incorporating all concentration/temperature-related parameters. Results demonstrated the validity of revised SD model by comparing experimental and theoretical water fluxes at a wide DS concentration/temperature range. Concentration/temperature-induced water flux increment efficiencies (CIE and TIE) were introduced to quantify utilization efficiencies of high-salinity water and heat. Results revealed that water fluxes were increased with the increase of both DS concentration (0.5–5.0 M) and temperature (18–50 °C). However, the CIE decreased with the increase of DS concentration, but increased with the increase of temperature. Furthermore, the TIE increased with the increase of both DS concentration and temperature from 25 to 47 °C. Correlation coefficient of CIE and TIE was defined and calculated to optimize the FO process efficiency through identifying favorable zones of DS concentration and temperature.

Hardware provision of electrostimulated wire drawing

The electrostimulated drawing process monitoring system (EDPMS) is considered, covering such indicators as temperature in deformation zone and drawing force, which forms control signal to generator of high-power current pulses, principally based on periodic discharge of a pre-charged capacitor to low-resistance load. In order to increase reliability and quality of electrostimulated drawing process control system (ESDPACS) is implemented, including single circle system of drawing force control, as well as delayed temperature feedback in deformation zone. Dependences of change in drawing force and temperature on frequency of pulse reproduction are obtained from the results of laboratory tests and calculations using known and original techniques. To analyze operating modes of electrostimulated drawing using automated control system, ESDPACS model was implemented in the Matlab-Simulink environment. Developed model allows to improve technical characteristics and operating modes of the system. Structural diagram of ESDPACS, its model in Matlab-Simulink environment, oscillograms of transition processes are presented in the paragraph. A single circle drawing force automated control system with flexible feedback on temperature in deformation zone allows to optimize operating modes and to increase reliability of electrostimulated deformation process.

Ternary borosilicates as potential cladding glasses for semiconductor core optical fibers

AbstractOur study advances the development of new ternary silicate glasses for use as a designed cladding for semiconductor core optical fibers using molten core draw process. In order to fabricate high‐quality hybrid fibers (homogeneous core shape, low amount of bubbles, low internal stress, no cracking), oxide glasses are the best choice as cladding materials. These glasses should be engineered with tailored thermal properties (coefficient of thermal expansion (CTE) and drawing temperature) so they match those of the semiconductor. Glasses in the system (50SiO2‐(20 − x)Na2O‐(25 + x)B2O3‐5MO) with x = 0 and 10 and MO = ZnO, TiO2, GeO2, Ga2O3, and Al2O3 and in the system 50SiO2‐10Na2O‐(40 − y)B2O3‐yTiO2 with y = 0, 1.25, 2.5, and 5 were investigated. Their thermal properties were measured and discussed with regard to the glass structure analyzed using FTIR spectroscopy. Due to their rigid network, which leads to beneficial thermal properties including low CTE (~5 ppm K−1), the Ge‐containing glass with x = 10 is a promising cladding candidate when preparing a Ge core fiber and the Ga or Zn‐ containing glasses when preparing an InAs core.

Study on Phase Transformation Behavior of Strain-induced PLLA Mesophase by Polarized Infrared Spectroscopy

The structural transformation of mesophase to crystalline phase of strain-induced poly(L-lactic acid) has been investigated by differential scanning calorimetry (DSC) and in situ temperature dependent polarized Fourier transform infrared (FTIR) spectroscopy. It is found that, as the drawing temperature increases, melting of strain-induced mesophase in the heating process can remarkably interfere the crystallization behavior subsequently. Coupling with in situ polarized FTIR, from 60 °C to 76 °C, the mesophase melts partially rather than completely melting, and changes immediately to three-dimensional ordered structure. Of particular note, through monitoring the subtle spectral change in the critical phase transformation temperature from 60 °C to 64 °C, it is clearly demonstrated that relaxation of oriented amorphous chains initially takes place prior to the melting of mesophase.

Leukocyte coping capacity chemiluminescence as an innovative tool for stress and pain assessment in calves undergoing ring castration.

Pain and stress assessment in animals is considered an imperative issue and also a difficult challenge. Unfortunately, no gold standard technique for pain and stress assessment in animals has been validated nowadays. A new tool to assess stress in animals consists of measuring the leukocyte coping capacity (LCC). The aim of this study was to evaluate the whole-blood LCC chemiluminescence as an innovative tool for stress and pain assessment in the bovine species undergoing ring castration. Twenty 2-mo-old male mix-breed Piemontese-Angus-Belgian Blue calves (Bos taurus) weighing 90 ± 4 kg were used. The animals were randomly allocated in 2 groups composed of 10 subjects each as follows: ring castration group (CAS) and sham castration group (SHAM). Blood drawing, scrotal and perineal temperature recording, scrotal lesion score, pain assessment, and LCC Chemiluminescence were performed at different time points, which were as follows: 1 h before castration/sham (-1 h), 30 min postcastration/sham (30 min), 3 d postcastration/sham (3 d), 7 d postcastration/sham (7 d), 14 d postcastration/sham (14 d). Results showed that in CAS LCC values significantly increased (P < 0.05) at 3 d and decreased at 7 d, whereas in SHAM, LCC values did not significantly vary between the study times. Significant differences in LCC values between CAS and SHAM were seen at 7 d (P < 0.0001). In the CAS group, scrotal lesion was scored as 0, 0, 3.8, 2.7, and 0.2 at -1 h, 30 min, 3 d, 7 d, and 14 d, respectively, whereas in SHAM, its score was 0 at every time point. Perineal temperatures did not vary throughout all the study times in both CAS and SHAM. Differences among the 2 groups were noted in scrotal temperatures only at 3, 7, and 14 d (P < 0.05). In CAS, the percentage of animals which obtained a pain score ≥ 1 was: 10% at -1 h, 30% at 30 min, 20% at 3 and 7 d, and 10% at 14 d, whereas in SHAM, no pain signs were noted at any time point. No significant difference between CAS and SHAM was recorded in cortisol blood level at any time point. No stress leukogram nor variation in neutrophil/lymphocyte ratio was noted at any of the time points in both CAS or SHAM. Our results suggest that ring castration might cause long-lasting pain in calves, but its magnitude is not easily detected by conventional methods. We argue that whole-blood LCC chemiluminescence might be a useful tool for detecting pain and stress in calves undergoing ring castration.

Automatic Control of Electrostimulated Drawing

A system for regulating the parameters of electrostimulated drawing (the temperature in the deformation zone and the drawing force) is considered. This system produces a control signal for the unit generating powerful current pulses. The basic operating principle is periodic discharge of a precharged capacitor to a low-resistance load. For regulation of the pulse amplitude and increase in system power, the uncontrollable dc source in the charger is replaced by two irreversible thyristor converters, which are in series and operate in the same direction. That produces a controllable voltage at the power capacitors. To optimize capacitor charging, a two-loop subordinate control system is employed: the external loop regulates the voltage, while the internal loop regulates the current that charges the capacitors. The high speed of the transient processes in electrostimulated drawing—in particular, the rapid temperature rise in the deformation zone on account of the large current pulse (up to 10 kA) and the high pulse frequency (up to 400 Hz)—means that manual control is practically impossible. To boost the reliability and quality of electrostimulated drawing using a powerful current-pulse generator, an automatic control system for electrostimulated drawing is developed. It includes a single-loop system for regulating the drawing force and also delayed temperature feedback in the deformation zone. The dependence of the drawing force and temperature on the frequency of the current pulses is established by means of laboratory research and calculations using both new and familiar methods. A model of the proposed control system in MATLAB-Simulink software permits analysis of the operating conditions in electrostimulated drawing under automated control. The model is consistent with the actual parameters obtained in research on the electroplastic effect. The proposed model permits improvement in the characteristics and operating conditions of electrostimulated drawing. The formalized structure of the system, the proposed model of the system in MATLAB-Simulink software, and the oscillograms of the transient processes are considered. The single-loop automatic control system for the drawing force, with flexible temperature feedback in the deformation zone, permits optimization of the operating conditions and improvement in the reliability of electrostimulated drawing. The proposed system is recommended for use in studying electrostimulated deformation and also for the control of wire drawing in production conditions

Analysis and study of dieless drawing process for rod based on radial direction gradient slab method

Dieless drawing is one of the most advanced processing technologies. After heating and cooling, the diameters of the wires or rubes can be reduced without drawing dies. Comparing to the traditional drawing processes, the workpiece is no longer touched with the processing equipment. The production efficiency is increased while the consumption of energy is also saved. In this paper, the dieless drawing process will be researched based on the gradient slab method. All the significant parameters in this process will be taken into the consideration, such as drawing velocities, thermal properties, and temperature conditions and geometrical parameters of material. The effects of pairwise related parameters on the final area and temperature as well as deformation length will be shown in three-dimensional diagrams. A novel analysis model of dieless drawing will also be proposed based on vertical gradient slab method. This model will be seen as a strong theoretical support for studies of dieless drawing.

On the morphologies of oxides particles in optical fibers: Effect of the drawing tension and composition

Rare-earth-doped oxide nanoparticles in the core of silica optical fibers are becoming well studied as they yield enhanced and tailorable spectroscopic and optical properties. In this paper, the evolution of particle morphology, induced by the drawing step, is studied. Indeed, during the fiber draw process, the glass flows and particles can elongate and even break-up into smaller particles through Rayleigh-Plateau instabilities. The shape of elongated particles is related to the composition as it depends on the viscosity ratio between the particle and the matrix. Moreover, a lower drawing temperature enhances the break-up phenomenon. These observations offer new possibilities for the control of the size and the shape of particles, hence performance of active optical fibers.

Low-Energy Membrane Process for Concentration of Stick Water.

This communication describes the application of forward osmosis (FO) to concentrate stick water, a nutrient-rich water byproduct of meat rendering operations. The objectives of the study were to carry out a set of batch FO runs in concentration mode to determine the maximum achievable stick water concentration and to perform a preliminary cost analysis for operating a FO/reverse osmosis membrane separation process for comparison to an evaporative concentration process. The study examined the roles of feed and draw solution stir rates, temperature, feed concentration, and draw solution ionic strength on flux using commercial cellulose triacetate membranes. Results show that FO could concentrate the stick water up to 45 wt %; however, concentrations above about 30 wt % would be difficult to process through conventional membrane configurations. Preliminary operating cost estimations show that the energy cost of the FO process is about 5.3% of the energy costs for a single-effect thermal evaporation process; and, assuming a 2-year membrane lifetime, the total operating cost using FO membranes was estimated to be about 23.1% of the operating cost using such a thermal evaporation process.

Effects of twins and precipitates at twin boundaries on Hall–Petch relation in high nitrogen stainless steel

Abstract

The Wire Drawing Mechanics of Near-Equiatomic NiTi SMA

The wire drawing mechanic of Ti-49.82Ni (at. %) Shape Memory Alloy (SMA) was investigated through the true stress-strain curves and drawing stresses. The tensile tested solution treated wire presented a four steps elongation at temperatures below the austenite finish temperature (AF), and a conventional one-step behavior above the martensite deformation temperature (MD). The tensile yield stress for the formation of detwinned martensite (DTM) or stress-induced martensite (SIM) increased as the testing temperature increased; however, for larger deformation, the behavior reversed. The efficiency of drawing work, which is the ratio of uniform work to total work, increased from 10% for 0.07 mm2.mm-2 area reduction at 25 °C to 50% for 0.21 mm2.mm-2 at 110 °C. Therefore, wire drawing temperature and area reduction should be combined to increase the efficiency, taking into account the desired properties with reasonable workability. Furthermore, transformation work should be considered on wire drawing shape memory alloys as phase transformation occurs in temperatures below MD.

An investigation into the crystalline morphology transitions in poly-L-lactic acid (PLLA) under uniaxial deformation in the quasi-solid-state regime

The mechanical behaviour, crystalline and macromorphology structure development during uniaxial deformation and annealing of poly-l-lactic acid (PLLA), with varying strain rate and draw temperatures (Td) above Tg, have been investigated using small- and wide-angle X-ray scattering (SAXS/WAXS), microscopy, thermal and mechanical techniques. The mechanical behaviour of PLLA, was strongly dependent on Td where embrittlement and eventual failure were observed as Td was increased, during uniaxial drawing of the amorphous polymer. This was mirrored in the bulk surface morphology where crazing, microvoiding and cavitation occurred with increasing Td. SAXS/WAXS data showed that strain-induced crystallization occurs on drawing, but crystallite orientation decreased with increasing Td, due to chain relaxation at temperatures ≥30 °C above Tg. However, no long-range oriented lamellar macromorphology was observed post-draw directly and only developed in the samples that were step annealed at temperatures above Td. Also, the disordered α′ crystal form was observed post-draw at Td between 60 and 80 °C, whereas Td ≥ 90 °C, resulted in the ordered α crystal form directly. However, on annealing at temperatures of ≥110 °C, the α′-α crystal transition ensued and in all samples, an oriented lamellar macromorphology developed. Therefore, Td and post-draw annealing, have a significant influence on the mechanical properties, crystallinity and crystalline phase transformation in PLLA, which in-turn, affects the polymers medical and industrial applications.

Effect of flow rate, draw solution concentration and temperature on the performance of TFC FO membrane, and the potential use of RO reject brine as a draw solution in FO–RO hybrid systems

Effect of flow rate, draw solution concentration and temperature on the performance of TFC FO membrane, and the potential use of RO reject brine as a draw solution in FO–RO hybrid systems

Optimizing parameters for continuous electrospinning of polyacrylonitrile nanofibrous yarn using the Taguchi method

In this study, the Taguchi method, analysis of variance, and principal component analysis were used to design the optimal parameters with respect to different quality characteristics for the continuous electrospinning of polyacrylonitrile nanofibrous yarn. The experiment was designed using a Taguchi L9(34) orthogonal array. The Taguchi method is a unique statistical method for efficiently evaluating optimal parameters and the effects of different factors on quality characteristics. The experimental results obtained by this method are more accurate and reliable than one-factor-at-a-time experiments. The control factors discussed in this work include the draw ratio, nozzle size, flow rate, and draw temperature. The quality characteristics taken into consideration are fiber diameter, fiber uniformity, and fiber arrangement. The parameters to optimize the different quality characteristics were obtained from the main effect plot of the signal-to-noise ratios, after which analysis of variance and confidence intervals were applied to confirm that the results were acceptable. Multiple quality characteristics were analyzed by principal component analysis from the normalized signal-to-noise ratios and the principal component score. Combining the experimental and analysis results, the optimum parameters for multiple quality characteristics were found to be a draw ratio of 2.0, a nozzle number of 22 G, a flow rate of 7 ml/h, and a draw temperature 120℃.

Rapid fabrication of microneedles using magnetorheological drawing lithography.

Microneedles have been widely applied in biomedical fields owing to their painless, minimally invasive, and convenient operation. However, most microneedle fabrication approaches are costly, time consuming, involve multiple steps, and require expensive equipment. Furthermore, most researchers have focused on the biomedical applications of microneedles but have given little attention to the optimization of the fabrication process. This research presents a novel magnetorheological drawing lithography (MRDL) method to fabricate microneedle, bio-inspired microneedle, and molding-free microneedle array. In this proposed technique, a droplet of curable magnetorheological fluid (CMRF) is drawn directly from almost any substrate to produce a 3D microneedle under an external magnetic field. This method not only inherits the advantages of thermal drawing approach without the need for a mask and light irradiation but also eliminates the requirement for drawing temperature adjustment. The MRDL method is extremely simple and can even produce the complex and multiscale structure of bio-inspired microneedle.

Light-emitting optical fibers with controllable anomalous small-angle scattering

Glow was studied from a light guide with anomalous optical losses into small-angle scattering, provided by means of the specifically modified method of chemical vapor deposition in fabricating the optical fiber. The dependence of the optical loss coefficient at a wavelength of 650 nm on the drawing temperature of fiber with 10 mol. % GeO2 in the core was investigated experimentally. Based on this dependence, a theoretical analysis was carried out in order to determine the technological parameters for fabricating a fiber with uniform glow at a length of several hundred meters. A 400 m long fiber specimen was fabricated, emitting light at a wavelength of 650 nm with a constant glowing brightness estimated at 23 μW/m and produced by a laser source with a power of 10 mW. Such fibers are proposed to be used as emergency light pointers for tunnels, corridors, stairs, and other black-out objects.

Stretching temperature dependence of the critical strain in the tensile deformation of polyethylene copolymer

The deformation behavior and structural evolution of the quenched ethylene-butene copolymer under uniaxial loading and unloading were investigated as a function of stretching temperature using step-cycle tests, in situ small angle X-ray scattering (SAXS), and wide angle X-ray diffraction (WAXD) measurements. The true stress-strain curves together with detailed analysis of SAXS results indicated that the irreversible plastic strain set in quite early at small strains as the drawing temperature was increased. The critical strain, at which the recoverable elastic strain reached the plateau region and the long period started to keep essentially constant upon stretching, was found to increase distinctly from about 0.65 at room temperature to 1.00 at 100 °C. This dependence of critical strain on the stretching temperature was directly related to the effective entanglement density of the amorphous network as derived from the Gaussian model of Haward-Thackray. Despite the considerable changes of the long period and the crystallite dimensions at identical strains upon stretching and unloading, there existed a one-to-one correspondence between the strain and the orientational order parameter of polymeric chains in the crystalline phase, irrespective of mechanical stress state. This work yielded new insight into the relationship between mechanical stability and operation temperature in industrial application of crystalline polymers.

Photorefractivity of germanosilicate light guides

In the fabrication of single-mode germanosilicate light guides, we studied how a reducing atmosphere in the high-temperature compression process of fiber preforms in a modified chemical vapor deposition process affects the photorefractive properties of the light guides. The results indicate an increase in photorefractivity and a decrease in the fiber drawing temperature with additional doping of the core of the light guide with fluorine.