Effect Of Preheat Research Articles

Experimental studies of ICF indirect-drive Be and high density C candidate ablators

To validate our modeling of the macroscopic and microscopic hydrodynamic and equation of state response of these candidate ablators to NIC-relevant x-ray drive, a multi-lab experimental program has been verifying the behavior of these new ablators. First, the pressures for onset and termination of melt for both Be and HDC under single or double shock drive has been measured at the Z and OMEGA facilities. Second, the level and effect of hard x-ray preheat has been quantified in scaled experiments at the Omega facility. Third, a long planar x-ray drive has been developed to check 2D and 3D perturbation growth at the ablation front upon acceleration. The concept has been extended to study growth at and near the ablator-ice interface upon deceleration. In addition, experimental designs for validating the expected low level of perturbation seeding due to possible residual microstructure after melt during first and second shock transit in Be and HDC have been completed. Results so far suggest both Be and HDC can remain ablator choices and have guided pulse shaping designs.

Heat Flow Simulation and Evolution of Microstructure in Welding of Rail Steel

In the present study heat flow simulation was carried out to predict the microstructure and examine the effect of preheat and plate thickness on cooling rate of the weld metal. SOLIDCAST software is used for simulating thermal regime in the base metal. The results of simulation studies revealed that cooling rate and hence the evolution of microstructure along the parent metal were functions of the preheating temperature and the plate thickness. The superimposed simulated temperatures on CCT diagram indicated the absence of martensite precipitation in HAZ region and this was experimentally verified. The results also indicated the possibility of suggesting the preheating temperature for defect-free welding of plates of given thickness.

Effect of preheat, bed porosity, and charge control on thermal response of submerged arc furnace producing ferrochromium

The temperature profile inside the submerged arc furnace is a critical factor influencing the process efficiency in the production of ferroalloys. The effect of a number of critical process parameters such as the charge preheat, bed porosity, and charge chemistry on the temperature profile was analysed by means of a mathematical model. It was found that preheating of the charge had a significant influence on the profile. Higher bed porosity tended to bring the various isotherms closer to the hearth of the furnace. Low bed porosity tended to expand the high temperature zone of the furnace. This can lead to diminished process efficiency under certain circumstances. The charge chemistry also altered the profile depending on the type of changes introduced. The influence of these parameters and their significance for the operation of the process are discussed in this paper.

Effect of Preheat on Tensile and Corrosion Properties of Steel Welded Joints

Effect of Preheat on Tensile and Corrosion Properties of Steel Welded Joints

Effect of Preheat on Residual Stress Distributions in Arc-Welded Mild Steel Plates

Residual stress distribution in the longitudinal and transverse directions on a 6-mm-thick arc-welded mild steel plate was experimentally examined with and without initial preheat. Stress measurements were completed by monitoring strain changes on mounted strain gauges resulting from successive milling of the welded plate specimens. Machining stresses were also compensated for by carrying out measurements of strain changes due to milling operation of a stress-free unwelded annealed mild steel plate. High tensile residual stresses exist close to the weld line in both longitudinal and transverse stresses. Maximum longitudinal residual stress values existing close to the weld line are reduced (between 50 and 75%) due to the effect of initial metal preheat of 200 °C of the welded steel plate.

Effect of preheat on welding of ductile cast iron

The effect of preheat temperature on the microstructure obtained in the heat-affected zone (HAZ) and the carbide zone in the weld metal adjacent to HAZ has been studied in multipass welds for the as-cast and ferritic ductile cast irons. The welding was carried out with manual shielded metal arc welding using ENiFe–CI filler metal. Ultrasonic, microhardness distribution, tensile and impact tests were conducted to evaluate the quality of welded joints.

Experimental measurements of upward flame spread on a vertical wall with external radiation

Abstract The overall objective of the project is to gain an understanding of the flame spread phenomenon under simulated surrounding fire conditions. In this phase of the project, emphasis is placed on obtaining experimental data for upward flame spread with applied external radiation on practical wall materials. A second phase (not yet reported) is the development of a numerical flame spread model and the experimental results presented here will be used for comparison with model predictions. Flame height, and in some cases pyrolysis height, were recorded as functions of time for 120 cm×30 cm samples; and these data were used to quantitatively investigate the effect of external radiation on several materials. Infrared heating panels were used to supply radiant fluxes of up to 15 kW/m 2 to the sample. Many wood-based materials do not exhibit flame spread to the top of the sample when ignited without applied external flux. With moderate levels of external radiation (5–10 kW/m 2 ), many of these materials sustained flame spread to the top of the sample. With increasing external radiation levels, flame spread was also more rapid. A comprehensive series of tests was run on particle board to investigate the effect of igniter strength, preheat of the sample, and sample thickness. Igniter strength was not a significant factor and did not cause the flame spread to be sustained; the effect of preheat, even at moderate levels of radiant flux, was important; and sample thickness had a slight effect, with thicker samples burning slower. Total heat feedback to the sample was measured and the maximum values for various samples are reported. Experimental data obtained in this project will be used to aid in the development and validation of a numerical flame spread model.

Towards the development of a preheat procedure for OSL dating of quartz

Isothermal decay data for the natural optically stimulated luminescence (OSL) of a quartz sample from the Kimberley region of Western Australia are presented. These show that >99% of the initial OSL signal measured using a broad-band blue/green-light stimulation source is derived from a single trap. A lifetime at 20°C of about 850 Ma is predicted for this OSL trap. Since these measurements may be affected by charge transfer or sensitivity changes, both of which are thought to occur as a result of heating, the effects of prior heating (preheating) on the shape of the quartz OSL decay curve have been investigated. The relationship between the initial OSL (first 0.4 s), the OSL at the end of a 100 s stimulation period, and the integrated OSL (0–100 s), is presented at a constant stimulation temperature of 125°C, but following preheats at temperatures between 110°C and 380°C. It is deduced that both the natural and regenerated OSL are dominated by a single trap/luminescence centre combination for preheats up to above 300°C. There is probably a small contribution [about 1% of the natural OSL integral (0–100 s) without preheating] from traps which are not emptied by heating to 340°C, and which have a longer lifetime. Based on the observation that the initial OSL signal from 0.1 s stimulation correlates well with the net integral OSL (0–100 s), the effect of preheat on the natural and regenerated OSL is examined again using single aliquots. These curves are then corrected for changes in luminescence efficiency with preheating obtained using the 110°C thermoluminescence from a 0.1 Gy test dose, before fitting with a simple two trap model. We draw conclusions regarding the implications of this study for dating.

Study of sensitivity change of OSL signals from quartz and feldspars as a function of preheat temperature

Optically stimulated luminescence (OSL) signals from feldspar and quartz samples were studied using infrared (860 nm) and green light (420–575 nm) stimulation. A serious problem connected with the regeneration technique used for dating is associated with a change of OSL sensitivity to radiation in the course of the measurement process. A typical effect seen is a large increase of the apparent strength of our beta source when calibrated against a gamma source. If the regeneration procedure is used, it is shown that the sensitivity increases up to ∼50% during the measurement process and as a result, the equivalent dose (ED) would be underestimated. A study of sensitivity changes in feldspars and quartz was carried out with emphasis on the effect of preheat and annealing on the OSL signal. Measurement results obtained are presented, and possible elimination of errors in dating caused by sensitivity changes is discussed.

Laser-produced shock waves in aluminum-gold targets for the study of Hugoniot melting in gold

Using the technique of impedance-mismatch, we have been able to study a high-Z material at high pressures using laser-produced shock waves without the deleterious effect of radiative preheat. Furthermore, measurements of shock-induced luminescence yielded the first experimental determination of the temperature of gold above its Hugoniot melting point and the results corroborated a new equation-of-state derived from first principle, solid and liquid state theories.

Effect of heat input and preheating on hydrogen assisted weld joint cracking of a 0.13% C, 1.5% Mn, 0.032% Nb high strength steel of 50 mm plate thickness in the IRC test

The effects of preheating and heat input on hydrogen assisted weld joint cracking are investigated at a restraint intensity of 32 kN mm−2 of a 0.13% C, 1.5% Mn, 0.032% Nb high strength steel of 50 mm thickness in the IRC test, using a high hydrogen experimental electrode of 530 N mm−2 yield strength.For a heat input ranging from 0.6 to 1.05 kJ mm−1 a critical preheating temperature of 140°C for almost complete crack prevention, for a range from 1.5 to 2.05 kJ mm−1, 120°C were found respectively. Nominal stresses at the ends of the 70‐80 mm long welds at the start of extensive cracking increase with heat input and preheat, the crack propagating from the HAZ into the weld metal quickly. Under conditions without or close to cracking, however, final stresses after 18 h are reduced with heat inputs. Consequently, crack critical combinations of preheating and heat input are linked to stresses decreasing with heat input but increasing with preheat. From the established IRC‐test diagram required combinations of local preheat and heat input for either avoiding hydrogen cracking or overstressing of the weld metal can be determined. Currently used cracking prediction procedures do not consider the effect of heat input and preheat on stress sufficiently and, therefore, may provide unsafe conclusions.

The effect of preheat on the microstructure, hardness and toughness of HT-9 weldments

The welding preheat temperature is shown to significantly affect the dynamic fracture behavior of a 12CR-1Mo steel (HT-9) weld metal. A decreased preheat, effecting a faster weld metal cooling rate, results in an increased upper shelf energy and lower ductile-brittle transition temperature with no charge in weld metal. SEM examinations indicate a decreased dendrite spacing and lower interdendritic segregation with a faster cooling rate. It Is evident that the varying interdendritic ferrite content and morphology and the dendrite spacing, both controlled by the cooling rate, play a significant role on the weld metal dynamic fracture behavior. The results suggest the lowest preheat compatible with good welding practice be used for maximum benefits to weld metal fracture mechanics.

Effect of preheat on molding compounds

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEffect of preheat on molding compoundsJames W. McFarlandCite this: Ind. Eng. Chem. Prod. Res. Dev. 1982, 21, 1, 113–119Publication Date (Print):March 1, 1982Publication History Published online1 May 2002Published inissue 1 March 1982https://doi.org/10.1021/i300005a024RIGHTS & PERMISSIONSArticle Views49Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (689 KB) Get e-Alerts

Magnetohydrodynamic behavior of thermonuclear fuel in a preconditioned electron beam imploded target

Two-dimensional magnetohydrodynamic numerical calculations have been performed to study the fuel behavior of a preconditioned relativistic electron beam target in which, experimentally, a portion of the beam current prepulse entered the target to provide fuel preheat and magneto-thermoinsulation. The magnetohydrodynamic plasma model used includes radiation, thermal conduction, ionization, and resistive diffusion. The magnetohydrodynamic partial differential equations are solved by a computer code employing implicit finite-difference methods. The fuel is shown to develop counter-streaming vortices during the implosion phase. The computed neutron yield is in reasonable agreement with the experimental value, suggesting the origin of the neutrons to be thermonuclear. The effect of both magneto-thermoinsulation and preheat is examined.

Effect of Molecular Gas Radiation on a Planar, Two-Dimensional, Turbulent-Jet-Diffusion Flame

Non-gray radiation described by the exponential model for molecular gas bands was added to the numerical solution of turbulent combustion of methane in a planar, enclosed, jet-diffusion flame. The planar jet of methane is injected with velocity ufuel into a stream of air flowing with velocity uair parallel to the fuel. Diffusion-controlled combustion occurs in the mixing region of the jet. Plane-parallel, isothermal, black walls symmetrically located above and below the jet form the combustion chamber. A soot-free flame is assumed to exist so that molecular gas bands determine the thermal radiative transfer to the walls. Velocity, composition, and temperature fields and heat flux at the wall are obtained numerically. Approximately 40 percent of the requisite computation time is expended on the radiation calculation. Solutions are obtained to show the effect of channel size, air preheat, and product recirculation. Also the effect of reaction zone thickness was examined by varying an effective first Damko¨hler or mixing number which parameterizes the mixing-controlled reaction rate. It is found that a given reduction in maximum combustion temperature to reduce nitric oxide formation can be accomplished with a much less detrimental reduction on heat transfer by recirculating exhaust product into the combustion air than by reducing air preheat.

Effect of additional electric preheat on the convection of the glass body in sheet-glass tank furnaces

Effect of additional electric preheat on the convection of the glass body in sheet-glass tank furnaces

鋳鉄アーク溶接の際の予熱と焼鈍の効果

鋳鉄アーク溶接の際の予熱と焼鈍の効果

Explosion Test of High Strength Steel for Naval Ship Structures

NRL type crack starter explosion tests and explosion bulge tests of mother plate and welded specimens were conducted on 5 Japanese high strength steels, HT-50 (Mn-Si steel), HT-60 (Mn-Si steel, quenched and tempered), HT-70 (HY-80 steel type), HT-80 (T-1 steel type) and stainless clad steel (HT-50base).As a result of crack starter test, FTP temperature of HT-70 was found to be -60°C, and was considered as a sufficient material for naval ship structures.Bulge tests at room temperature and -20°C showed that welded specimens of all steels tested had almost same strength as their mother plates for explosive force. Stainless clad steel showed no superiority than 50 HT. No remarkable effect of preheat of welded specimen of HT-70 was observed. Various notch-toughness tests (2 mm V-, 2 mm U- and press notch charpy and drop weight tests) were also conducted and comparisons were made with the result of crack starter explosion test.