Effect Of Preheating Temperature Research Articles

Effects of time-temperature profiles on glow curves of germanium-doped optical fibre

The Germanium (Ge) doped silica optical fibres have demonstrated the great potential to be developed as a thermoluminescent (TL) dosimeter that can be used in various applications in radiotherapy, diagnostic radiology, UV dosimetry system and food irradiation industry. Different time-temperature profile (TTP) parameters of the TL reader have been employed by many researchers in various of TL studies. Nevertheless, none of those studies adequately addressed the effects of the reader's preheat temperature and heating rate on the kinetic parameters of the TL glow curve specifically, the Ge-doped silica optical fibres. This research addresses the issue of TTP parameters with special attention to the determination of the kinetic parameters of the glow curve. The glow curve responses were explored and the kinetic parameters were analyzed by the WinGCF software, to show the effect of the preheat temperature and heating rate of the reader on Ge-doped fibre irradiated with 18Gy of 6MV photons radiation. The effect of TTP parameters was discussed and compared against the commercial fibre and tailored made fibre of 6mol% Ge-doped of flat and cylindrical shape. The deconvolution of glow peaks and the kinetic parameters were obtained by the WinGCF software. This enables to fit accurately (1.5%<FOM<5.0%) for all measured glow curves. A positive, moderate linear relationship exists between the TL response and the heating rate when the specific preheat temperature was used to read commercial fibre (50°C) and cylindrical fibre (80°C and 160°C). It is found that the glow peaks of cylindrical fibre exhibit the highest peak integral as compared to flat and commercial fibres. This study revealed the possible relationship between the reader's TTP parameters and the kinetic parameters of TL glow curves for the commercial and tailored made Ge-doped silica optical fibres.

Effect of the FCAW Welding Process and Post Weld Heat Treatment on the Properties and Microstructure of the Weld Joints of Heat Treated 4330V Steel

4330V is a high strength, high toughness, heat treatable low alloy steel for application in the oil, gas and aerospace industries. It is typically used for large diameter drilling parts where high toughness and strength are required. The research describes the effect of preheat temperature, interpass temperature, heat input, and post weld heat treatment on strength, hardness, toughness, and changes to microstructure in the weld joint. Welding with the lower heat input and no post weld heat treatment resulted in optimal mechanical properties in the weld metal. Austempering at 400 °C resulted in optimal mechanical properties in the HAZ. Increasing preheat and interpass temperature from 340 °C to 420 °C did not improve Charpy V-notch values or ultimate tensile strength in the weld metal or heat affected zones. The higher temperature increased the width of the heat affected zone. Austempering at 400 °C reduced HAZ hardness to a level comparable to the base metal. Both tempering and austempering at 400 °C for 10 hours reduced toughness in the weld metal.

A Numerical Study on Generation Mechanism of Vertical Cracks in Top Coat of TBCs During APS Deposition

Clarification of crack generation mechanism in the top coat of the thermal barrier coatings (TBCs) during atmospheric plasma spray process is important to improve the reliability of TBC. In this study, finite element analyses of stress and strain during the deposition process were conducted with layer-by-layer method to understand the cracking behaviors. Stress relaxation by generation of vertical cracks was expressed as an elasto-plastic behavior of the coating. The effects of pre-heating temperature of the substrate and plasma power on crack development were analyzed by changing of the initial and atmospheric temperatures in simulation, respectively. The simulation results of radial strain explained the experimental results of crack monitoring by non-contact laser acoustic emission method.

Influence of pre-heat temperature, pre-heat holding time and high-heat temperature on fouling of reconstituted skim milk during UHT processing

The effects of pre-heat temperature (65–95°C) and holding time (5 and 25s) on fouling of reconstituted skim milk at high-heat temperatures of 135–150°C using a bench-top UHT plant were investigated. Fouling was monitored by observing the variation in overall heat transfer coefficient (OHTC) with time and consisted of an induction phase (non-fouling) and a decline phase (fouling). A significantly shorter run-time was obtained with pre-heating at 65°C than with pre-heating at 75, 85 and 95°C. A longer holding time (25s) in the pre-heating section significantly increased the run-time of the plant compared with 5s holding. The high-heat temperature also affected the OHTC and run-time; similar run-times were observed at 135, 140, 142 and 145°C but at 150°C there was no induction phase and fouling rapidly occurred. Overall, pre-heating at 85°C or 95°C for 25s, combined with a high-heat temperature of 145°C, and pre-heating at 95°C for 25s combined with high-heat temperatures of 142°C, produced the longest run-times of the bench-top UHT plant.

Effect of Pre-Heating Temperature on Microstructure and Properties of 22MnB5 Steel Hot Stamping

The hot stamping process of ultra high strength steel(UHSS) sheet is an innovative way to manufacture the components with a ultra high tensile strength. The sufficiency of martensitic transformation in formed component is affected by pre-heating temperature of blank directly. In this paper, experiments of heating UHSS blanks to 700°C, 800°C, 900°C and 1000°C were implemented to investigate the effect of pre-heating temperature on the formed component’s microstructure and mechanical properties. The results indicate that 900°C is the best pre-heating temperature for hot stamping process. The microstructure of formed component is all fine and uniform martensite. Meanwhile, tensile strength and vickers hardness raise up to 1580MPa and 450HV, respectively.

Investigating the Effects of Process Variables on the Residual Stresses of Weld and Laser Cladding

Weld cladding was investigated using a nickel alloy clad on a high strength low alloy carbon steel substrate. The effects of pre-heat temperature, clad material and post-weld heat-treatment are examined, along with the potential for thinner clad layers using laser cladding. Experimental residual stress measurements show good correlation with the simulation model. Metallurgical studies illustrate good fusion between clad and substrate materials. The potential for a fatigue-resistant cladding was demonstrated in a stainless steel clad with the possible use of post-cladding operations to enhance the outcomes for the nickel alloy clad.

Effect of Preheat Temperature on Friction Stir Welded Aluminum Alloy 5052 Joints

The effects of preheat temperature on mechanical properties and the microstructure of friction stir welded (FSW) aluminum alloy 5052 joints were studied in the present work. Heated air from Hot Gun was applied in front of the FSW tool to give the preheat on friction stir welding process. Preheat temperature was set 150°C, 250°C and 300°C. Mechanical properties were correlated and analyzed according to tensile strength, macro and microstructure. Defect free weldswere obtained at all preheat variations. The increasing preheat temperature produced the coarser grain size, it influencedthe little decrease both the tensile strength and hardness of joints.

시편 예열 온도가 FCW 용착금속의 확산성 수소량에 미치는 영향

Cold cracking of weldment is one of the most serious welding problems. A sufficient quantity of diffusible hydrogen, a residual stress, and a sensitive microstructure are the causes of cold cracking. Removal of any one of these factors can be used to prevent cold cracking. Application of flux cored arc welding process is increasing due to high productivity and easiness of welding. In addition, to prevent cold cracking in the HAZ or weldment, preheat temperature and interpass temperature have to be controlled. In this study, the effect of preheat temperature on the levels of diffusible hydrogen in the weld metal deposited using flux cored wire was examined. The levels of preheat temperature of base metal specimen were ambient temperature, 50, 100 and <TEX>$150^{\circ}C$</TEX> respectively. The result showed that the increase of preheat temperature was a linear relationship with reduction of diffusible hydrogen content in weldment.

Preparation Process of Long Fiber Reinforced Impact Polypropylene Copolymer Composites

Composites of continuous glass fiber reinforced impact polypropylene copolymer (IPC) were prepared by using a cross-head impregnation mold by a self-designed die fixed on a single screw extruder, and were chopped into Long fiber/IPC pellets approximately 12 mm in length. The effect of preheat temperature and pulling speed on the mechanical properties of the composites were studied and micrographs of fracture surface of impact specimens for the composites were investigated by scanning electron microscope (SEM). Mechanical properties of the composites were best at 200 °C of the preheated temperature, for the better interfacial adhesion between glass and matrix resin, and that proved by the SEM. Meanwhile, mechanical properties of the composites decreasing with the increasing of pulling speed, for the impregnation effect degraded.

Laminar flame speeds of transportation-relevant hydrocarbons and jet fuels at elevated temperatures and pressures

Laminar flame speeds of several fuel/air mixtures were experimentally determined over equivalence ratios of ϕ=0.7–1.3, preheat temperatures of Tu=350–470K, and pressures of P=1–3atm in a high-pressure counterflow setup. Fuels investigated in this work included neat components relevant to liquid transportation fuels, such as n-decane, n-dodecane, iso-octane, toluene, n-propylbenzene, 1,2,4-trimethylbenzene, and 1,3,5-trimethylbenzene, a conventional Jet-A labeled as POSF 4658, an alternative jet fuel, S-8, labeled as POSF 4734, and a four-component Jet-A surrogate composed of n-dodecane, iso-octane, n-propylbenzene, and 1,3,5-trimethylbenzene. The experimental results were also compared with computed values obtained by using various published kinetic models for different fuels. In general, the simulated results are in fair agreement with the experimental data, considering the uncertainties in both experiments and kinetic models. Further analysis on experimental data was conducted to assess the effects of preheat temperature on laminar flame speed and pressure on mass burning flux. From the variation of mass burning flux with pressure, the overall reaction orders of various fuels were extracted. The present flame propagation data at elevated pressures for large hydrocarbons can be used in surrogate formulation and mechanism validation for liquid transportation fuels.

Stability of IRSL signals from sedimentary K-feldspar samples

Recent work has identified IR stimulated luminescence signals at elevated temperature from both potassium- and sodium-rich feldspars that have much lower anomalous fading rates than the conventional signal measured using IR stimulation at 50°C. This paper examines the stability of these signals for potassium-rich sedimentary feldspars. We show that the natural post-IR IRSL (pIRIR) signal from a 3.6 Ma old sample is in apparent saturation on a laboratory generated dose response curve, i.e. it does not show detectable fading in nature although a low fading rate is observed on laboratory time scales. We show that the pIRIR signal has a greater thermal stability than the IRSL signal and that the trend in increasing thermal stability is mirrored by a decreasing fading rate. We also investigate the effect of preheat temperature and IR stimulation power on the decay shape and conclude that the data can be explained in terms of either a single- or multiple-trap model. We present evidence that may suggest that at least part of pIRIR signal is derived from a high temperature trap (∼550°C thermoluminescence (TL) peak), although again the data can also be explained in terms of a single-trap model. Finally, we present dose response curves and characteristic curvature constants (D0) values for various IRSL signals and conclude that the more stable signals saturate more quickly than the less stable signals and that the initial and final signals saturate at approximately the same level.

Fatigue of Laserbeam Welded Joints of High-Carbon Steel Strips

The high-carbon steel strips are one of the most widely used base materials of bandsaw blade manufacturing. These materials have sufficient strength and ductility to cope with the high fatigue load of the bandsaw blades. These endless strips are produced by welding, and therefore the weld and the heat affected zone have different mechanical properties, like tensile strength and fatigue resistance, than the base material. These properties of the weld can be influenced by preheat and post weld heat treatment. Regarding to the latest industrial requirements, the application of laserbeam welding was examined to produce higher standard bandsaw blade. The laserbeam welded joints has lower heat input and narrower heat affected zone compared to metal inert gas (MIG) welding, which is currently used in bandsaw blade manufacturing. To assure the proper mechanical properties and sufficient resistance to fatigue, an examination was carried out to determine the effect of preheat temperature and post weld heat treatment time on the mechanical properties and fatigue behaviour of the laserbeam welded joint.

Deterioration of Fats and Oils during Pan-Frying -Effects of Pre-Heating Temperatures of Pan-

Deterioration of Fats and Oils during Pan-Frying -Effects of Pre-Heating Temperatures of Pan-

Effect of compact density and preheating temperature of the Al–Ti–C preform on the fabrication of in situ Mg–TiC composites

Magnesium reinforced in situ TiC particulates was successfully synthesized by utilizing the self-propagating high temperature synthesis (SHS) process. The result showed that preform temperature and compact density have effects on the SHS reaction. It is observed that when the compact density was below 68% of the theoretical density, no SHS reaction occurred. However, with an increase in density from 68 to 72%, the successful thermal explosion reaction was observed in the Mg melt. Besides this, the effect of preheat temperature on the fabrication of Mg/TiC composite was extensively studied and found that the preheat temperature below 300 °C failed to give rise to SHS reaction. However, the preheat temperature of 450, 500, and 550 °C favors the reaction inside the liquid melt, but the temperature of 600 °C leads to the ignition reaction in the preheating furnace itself. SEM and EDX study confirms fine distribution of TiC in the matrix.

Reaction zone characterization of counter-flow diffusion flame with diluted and preheated reactants

Reaction zone characteristics were studied using hydroxy radical planar laser-induced fluorescence (OH-PLIF) technique for a counter-flow preheated (CH 4+N 2)/(Air+N 2) diluted diffusion flames. The effects of preheat temperature and dilute ratio on the reaction zone characteristics were investigated by demonstrating the OH intensity distribution and reaction zone thickness from OH-PLIF images. Under the experimental conditions of constant cold flow velocity, the results show that the OH intensity and reaction zone thickness decrease with the increase of dilute ratio at constant preheat temperature and increase with preheat temperature at fixed dilute ratio. The OH maximum intensity shifts towards the “lean” side of counter flow at constant preheat temperature, and it shifts towards the fuel side with the increase of dilute ratio of fuel stream and towards the oxidizer side with the increase of dilute ratio of oxidizer stream respectively. The feasibility of OH as a reaction zone marker in this diluted combustion is verified further. The variation of diffusion and chemical reaction rate of reactants due to preheat and dilution contributes to the reaction zone characteristics simultaneously. The effect of strain on the flame reaction zone should be included in the future work.

Numerical study on premixed hydrothermal combustion in tube reactor

Premixed hydrothermal combustion of ethanol was numerically studied as a fundamental research to develop an energy conversion system utilising biomass and low quality oil. A simulation code available for oxidation of water solution mixture under sub/super critical conditions was developed. Lee–Kesler equation was selected as the equation of state. Chemical species of ethanol, oxygen, carbon dioxide and water, were considered as reactants and products of complete reaction. Mixing laws by Chung et al. and Wilke et al. were used for transport properties and that of Plöcker et al. was used for thermal properties and Lee-Kesler equation of state. Behaviours of ethanol oxidation under sub/super critical conditions were numerically simulated. For the reaction rate, we selected Schanzenbächer et al.'s expression obtained by the experiment under supercritical condition. Effects of preheat temperature, heat loss and flow velocity were examined by simulation. The differences of preheat temperatures led to the differences of temperature increase Δ T around critical point because of the specific heat peak at the critical point. Larger flow velocity caused slower increase of ethanol conversion and temperature increase. Changes of reaction rate for different flow velocities showed that larger flow velocity caused thicker reaction zone and higher reaction peak than that for smaller one because of the fluid advection. From the calculation with different heat losses (different heat transfer rate coefficients α), two-step temperature decrease appeared for larger heat loss (α = 2.5 × 104 W· m−2· K−1) while monotonous temperature decrease appeared for smaller heat loss (α = 2.5× 103 W· m−2· K−1).

Process Variables Optimisation of Polypropylene Based Fibre-Metal Laminates Forming Using Finite Element Analysis

This study investigates the effect of preheat temperature, blank holder force and feed rate on the formability of polypropylene based Fibre-Metal Laminates. Finite element method combined with Design of Experiments was used to determine the influence of the forming process parameters. The design of experiments was used to identify the relative influence of each process parameter considered in this study. A reduced set of coupled structural-thermal simulations using Ls-Dyna were carried out using a L9 orthogonal array. Simulations were carried out on the forming of domes. It was found that the blank holder force has the greatest influence to increase the minor/major ratios followed by feed rate and pre heat temperature. A more thorough investigation of preheat temperature illustrated an optimum preheat temperature at 130 °C.

The effect of preheat temperature and inter-pass reheating on microstructure and texture evolution during hot rolling of Ti–6Al–4V

The effect of preheat temperature and inter-pass reheating on microstructure and texture evolution during unidirectional hot rolling of Ti–6Al–4V in the alpha + beta field was investigated. Three different heating schedules were used to roll plates at 10% reduction per pass to a 3:1 total reduction (true strain = 1.15): (1) preheat at 955 °C with inter-pass reheating for 3 min, (2) preheat at 955 °C without inter-pass reheating, and (3) preheat at 815 °C with inter-pass reheating for 3 min. Following rolling, each plate was air cooled to simulate production practice. The microstructures and textures were determined using electron-backscatter and X-ray diffraction techniques. The results revealed that the intensity of basal poles decreased along the rolling direction and increased along the normal and transverse directions with decreasing rolling (furnace) temperature or the elimination of reheating between passes.

EFFECT OF PRE-HEATING TEMPERATURE ON THE CHARACTERISTICS OF SOL–GEL DERIVED LEAD ZIRCONATE TITANATE FILMS

Effect of pre-heating temperature on the properties of Lead zirconate titanate (PZT) powders and films was investigated. PZT powders and films were prepared via a triol-based sol–gel route. The PZT powders prepared at various heating temperatures were characterized. The preheating temperature range of 200°C–400°C and annealing temperature of 600°C were chosen to make the films. AFM micrograph revealed the thin films with homogeneous, dense, and crack-free properties. The pre-heating temperature was found to have a significant effect on phase formation, prefer orientation, and dielectric properties of the films. Higher dielectric constant and dielectric loss were observed at higher pre-heating temperature. However, all films showed the dielectric loss less than 0.04.

Phase evolution and effect of pre-heating temperature on the characteristics of PZT thin films grown by using a triol sol--gel route

Lead zirconate titanate (PZT) films were fabricated on Pt(111)/Ti/SiO2/Si(100) using the triol sol--gel method. The effect of the pre-heating temperature on the phase transformations, microstructures, electrical properties and ferroelectric properties of the PZT thin films was investigated. Randomly-oriented PZT thin films pre-heated at 400°C for 10 min and annealed at 600°C for 30 min showed well-defined ferroelectric hysteresis loops with a remanent polarization of 26.57 µC cm−2 and a coercive field of 115.42 kV cm−1. The dielectric constant and dielectric loss of the PZT films were 621 and 0.0395, respectively. The microstructures of the thin films are dense, crack-free and homogeneous with fine grains about 15–20 nm in size.