Metal Temperature Distribution Research Articles

Research on the non-linear temperature field of molten metal shaped by an electromagnetic field in DS processing

A new directional solidification (DS) technique, combining electromagnetic shaping with liquid metal cooling, is established to confine and shape liquid metal by an electromagnetic field without the mold and carry out DS with a high-temperature gradient. The motion of the sample, heat radiation, and especially the material-property difference between the solid and the liquid, are considered for electromagnetic heating. Thereafter, a non-linear temperature model is established to calculate the position of the solid/liquid interface with respect to the furnace, the height of liquid metal and the temperature distribution in stainless-steel samples. The results of calculation are in good agreement with experimental measurements. On the basis of the model, experimental parameters, such as the intensity of cooling, and the current in the induction coils, can be further optimized so as to control the morphology of the solid/liquid interface, the temperature gradient and the axial temperature distribution in the liquid metal. A FEM approach is developed in this paper.

Thermal optimization of micro-hotplates that have a silicon island

We have performed thermal measurements and electrothermal simulations (finite element modelling) with the aim of optimizing the power consumption and the temperature distribution of micro-hotplates for gas-sensing applications. A silicon island was added underneath the membrane of the micro-hotplate to improve the temperature distribution of drop-coated metal–oxide gas sensors and to thermally isolate MOSFET gas sensors. The temperature distribution over the sensing area and the power consumption depend on the silicon island thickness, which was optimized for both applications using the software MEMCAD from Microcosm Technologies. In the optimization process, we considered the thermal conductivity of silicon and dielectric membrane, the operating temperature, the geometry and the area of the heater, and the processing of the silicon island. The thickness of the silicon island was optimized to ensure a good temperature distribution over the gas-sensing area for metal–oxide and MOSFET gas sensors with specific geometry.

Experimental and computational study of nozzle electromagnetic stirring and its effects on solidification structure

Centreline shrinkage and segregation in continuously cast billets have an adverse effect on cast product quality. Nozzle electromagnetic stirring (N-EMS) is an effective method to refine the solidification structure of continuously cast billets and thereby improve the cast product quality. The effect of N-EMS on the solidification structure of continuously cast Sn-3·5Pb alloy has been investigated by means of experiments and numerical analysis. The results show that, upon imposing N-EMS, crystal grains within the billets are refined and continuous casting can be conducted at a lower pouring temperature; the solidification structure of the resulting obtained billets is much finer than without N-EMS. The mechanism by which the solidification structure of the billets is improved is considered to be a change in the flow and temperature distribution of molten metal in the nozzle.

Mathematical modelling of metal active gas arc welding

A feasibility study has been conducted to determine whether mathematical models can be used for the numerical simulation of metal active gas (MAG) arc welding. In the present work, a three-dimensional, nonstationary thermal model for fillet welding is developed. The transient temperature distribution in the base metal is numerically analysed to estimate the molten pool size using a finite difference model based on the heat flow equation, and the theoretical configuration of the molten pool is calculated, taking account of the balance of gravity, surface tension, and arc pressure. The developed model can be applied to various welding processes such as multipass welding, lap welding, and welding with torch oscillation. To evaluate the validity of the model analysis, the calculated results are compared with experimental results for MAG welding. Good correspondence is demonstrated between experiment and calculation.

Effects of diesel/water emulsion on heat flow and thermal loading in a precombustion chamber diesel engine

An experimental investigation has been carried out to study the effects of using water/diesel emulsion fuel in an indirect injection diesel engine on the heat flux crossing liner and cylinder head, thermal loading and metal temperature distribution. A single cylinder precombustion chamber diesel engine has been used in the present work. The engine was instrumented for performance, metal temperature and heat flux measurements. The pure gas oil fuel and different ratios of water/diesel emulsion were used and their effects on the heat flux level and the injector tip temperature are studied. Two correlation were found for the heat flux crossing the liner and the cylinder head at various water/diesel emulsion ratios, fuelling rate and thermocouple probe locations. It was found that the addition of water to diesel fuel, to control the nitrogen oxides emissions, has great influence on reducing the heat flux, the metal temperatures and thermal loading of combustion chamber components.

New Model of Flour Stress under Cold-Forming Conditions

Prediction of flow stress under forming conditions is commonly based on an explicit formulation of the flow stress model: The flow stress is in this case expressed as a function of strain, strain rate, temperature, more seldom of structure. Such formulations make it difficult to predict the flow stress under forming conditions for different strain paths and also when the strain rate and/or temperature varies during the deformation. This paper is aimed at describing a new model of strain hardening applied in metal forming analysis. This model allows better prediction of flow stress under cold forming conditions. The application of the incrementally formulated flow stress model is exemplified for prediction of metal flow, loads and temperature distribution in cold forming processes (cold rolling, wire drawing, cold forging).

A parallel algorithm for the simulation of temperature distribution in metal cutting

Temperature distributions involved in some metal cutting or surface milling processes may be obtained by solving a nonlinear inverse problem. A simplified metal cutting process is considered in this paper. A problem partitioning concept is used to partition the original problem. We propose a distributed algorithm in relation to the choice of numerical schemes in order to simulate the temperature distribution of such problems. Numerical results are provided for three different materials. Efficiency analysis is provided to examine the algorithm when it is being run in a distributed computing environment. Possibilities are discussed of encapsulating the algorithm in a computer virtual design environment for metal cutting and extending the algorithm in a real time simulation system.

Finite Element Simulation of Non-Steady-State Metal Flow and Temperature Distribution in Twin Roll Strip Casting.

A coupled method for simulating non-steady-state metal flow and temperature distribution in twin roll strip casting is presented. The viscoplastic and the heat conduction finite element methods are used to calculate the metal flow and the temperature distribution, respectively, and the interaction between the metal flow and the temperature distribution is taken into consideration. In the viscoplastic finite element simulation, a spatially fixed element mesh is employed to avoid severe distortion of elements. For the temperature analysis, the effect of latent heat due to solidification of molten metal is dealt with. The calculated profiles of the boundary between the solid and liquid regions in plane-strain twin roll strip casting agree well with those obtained from a model experiment using paraffin wax. In simulation of strip casting of stainless steel, the metal flow and temperature distribution become unstable when the solidified shell between the rotating rolls begins to flow reversely to the molten Pool.

Modelling of tool/chip interface temperature distribution in metal cutting

Modelling of the tool/chip interface temperature distribution during orthogonal metal cutting is presented. To make the model more realistic, the shear plane is assumed to be inclined to the chip velocity as generally occurs. It is shown this geometrical condition can be relaxed, which results in considerable mathematical simplification. The temperature distributions obtained along the chip back (chip/air interface) from the analysis are also compared with previous results and with direct experimental data. Better agreement is found between the proposed model and the experimental evidence.

Adiabatic Shear Localization in a Liquid Lubricant Under Pressure

Experimental tests with a high-pressure flow visualization cell clearly reveal that the shear deformation in a lubricant film at elevated pressures can localize by a mechanism vastly different from previously reported mechanically-induced shear bands. Verification by numerical solution of the energy equation shows that for a stress-controlled experiment, provided that the Brinkman number is sufficiently large, the local temperature experiences a rapid rise. The rapid rise of temperature along with the local rate of shear favors an unstable temperature profile. The research provides valuable insight into the behavior of lubricants under extreme conditions since this phenomenon may be operating in the thermally dominated regime of EHD traction. Furthermore, the fact that the hot shear band is isolated from the metal boundaries by a cooler liquid, may confound recent attempts to infer the shear stress distribution in a concentrated contact from IR temperature measurement of the metal temperature distribution.

Numerical Study of Melting of Scrap Metal

A one-dimensional time-dependent heat transfer model is presented for the melting process in a circular scrap melter. The phase change problem is tackled using an enthalpy-based method, and the complex scrap geometry is described with the porosity concept, i.e., the blocking effect of the scrap is represented by a blocking factor that is a function of the scrap porosity. Flame length is represented by a flame damping factor. The numerical procedure is carried out in three stages, from initial heating to complete melting. Some typical cases are simulated. Results show that the flame damping factor can significantly influence the melting process. A lower damping factor gives better uniformity in metal temperature distribution. The melting time can be improved drastically by decreasing this factor. The convective heat transfer coefficient dominates the temperature profile. The higher the convective heat transfer, the faster the temperature increase in the lower part of the furnace. A long flame and good stir...

Finite element analysis of the three-dimensional transient temperature field in steam turbine casings

One of the important considerations going into the process of optimization of start-up schedules for steam turbines is the estimation of thermal stresses during the transients. This in turn requires prediction of the transient temperature fields. In the case of the turbine casing, the procedures are complex in view of the irregular geometrical shape. Finite element analysis offers better scope in this regard and has been employed in the present work to compute the 3-D transient temperature distribution in the casing metal. The results obtained by a code developed for a specific type of turbine casing have been compared with the values measured by experiment and have been found to validate the code. Time-temperature histories for two typical locations inside the casing metals are presented. Isotherm surfaces across the metal at a given instant are shown.

Roll pass evaluation for hot shape rolling processes

Since the complex shaped caliber rolling usually takes place in hot operation, three dimensional mechanical behavior coupled with the heat transfer in and around the billet must be taken into account for accurate evaluation of the roll pass system. In the present study, the authors propose a new simulation approach to deal with the above coupling problem: the deformation mode method for the three dimenional deformation in the steady-state rolling process, and the two dimensional boundary element method for radiation and convection heat transfer between mill stands. Furthermore, to deal with temperature history in plastic working, heat generation by plastic deformation and friction work and heat transfer between rolls and billet are both taken into account in every incremental reduction. As an example, the butterfly roll pass system is taken in the actual angle steel rolling. It is found that (1) the mechanical behavior and characteristics can be discussed by the calculated metal flow, strain and temperature distributions in the whole roll pass system, and (2) the numerically estimated cross-sectional shapes after rolling are in fairly good agreement with the experimental measurements in the actual processing. The above example demonstrates the validity and effectiveness of the present modelling even for the industrial shape rolling process.

Simulation of metal flow and heat transfer during hot rolling of bimetal plates

Coupled thermomechanical finite element model is applied to simulate metal flow and temperature distribution during hot rolling of bimetal plates. Calculations are carried out for various reductions and dimensions of the plates. Two possible versions of the boundary conditions are assumed. The first considers the case when special guides or tensions prevent bending of the sample before entering and after exit from the roll gap. The second allows free bending of the plate on both sides of the mill. Results of calculations include distributions of strain rates, strains, roll pressure, friction forces and temperatures during rolling. Calculated rolling force and torque are compared with the experimental data. Several conclusions regarding the metal flow and heat transfer in various rolling conditions are drawn.

Simulation of strip casting process by twin roll method. (1st. Report. Analysis of solidification and temperature, and the experimental verification).

A model plant of strip casting system of two roll type was developed to obtain the fundamental data on optimum operating condition for production of strip or thin slab. In this first report, mode of solidification and temperature distribution in the strip of Pb-Bi alloy with low melting temperature during steady process was simulated by solving the heat conduction equation incorporated with latent heat due to solidification when considering material flow. And, the results of analysis on the shape of the solidified shell and the temperature distribution in molten metal was compared with measured temperature data by thermocouples, and the validity of the simulation method are also discussed.

Finite‐element modelling of metal flow in three‐dimensional forming

AbstractA fully three‐dimensional elastic–plastic finite‐element program for the study of metalforming operations is described. Several applications are discussed, and the finite‐element (FE) predictions of metal flow, strain rate and temperature distributions, and the sites of initiation of ductile fracture are presented.

Reconstructing Internal Temperature Distributions From Ultrasonic Time-of-Flight Tomography And Dimensional Resonance Measurements.

Two ultrasonic techniques for reconstructing the internal temperature distribution in metal bodies-time-of-flight tomography and dimensional resonance profiling-are described. An analysis of the tomographic reconstruction of temperature (including ray refraction effects) in a cylindrical body is presented together with initial experimental results. Dimensional resonance profiling is a new technique that allows the reconstruction of a one-dimensional distribution of temperature in a structure from measurements of its resonant frequencies. While time-of-flight tomography is well suited for measuring temperature in a cylindrical geometry, a combination of dimensional resonance and (a restricted form of) tomography is the best method for measuring temperature profiles in the more practically important rectangular slab geometry.

A Numerical Finite Difference Method for Performance Evaluation of a Periodic-Flow Heat Exchanger

A numerical finite difference method is presented for calculating the fluid and metal temperature distributions for the periodic-flow type heat exchanger, accounting for the effect of heat conduction in the wall in the direction of fluid flow. Unlike previous solution techniques that use the Gauss-Seidel method based on a single element calculation, the method presented here uses a column of elements to compute the fluids and metal temperature distributions, and it allows variable or constant thermal properties (specific heats, densities, heat transfer coefficients, and thermal conductivities). Nonuniform mass flow rates and a nonuniform grid spacing may be employed. The present method reduces the computational time required for convergence and improves the numerical stability while allowing an arbitrary metal temperature distribution as a starting case. After qualifying the numerical method, illustrative results are presented for counterflow and parallel flow rotary regenerators with three different surfaces in the flow direction and variable fluid and material properties.

Temperature distribution in thin films receiving radiant energy

An expression is derived for estimating the temperature distribution in thin metal and semiconductor films locally receiving radiant energy.

Temperature field and crater wear in metal cutting using a quasi-finite element approach

SUMMARY A quasi-finite element model for the determination of steady-state thermal fields in a tool-chip-workpiece system is presented. The approach accounts for all the three modes of heat transmission. Only a few temperature measurements, at certain discrete points in the continuum, are needed as boundary conditions. The method is employed to determine the temperature distribution in an orthogonal metal cutting operation. The results agree with experimental measurements under similar cutting conditions A comparison between the computed isotherms and the experimentally determined lines of equal crater wear of the cutting tool indicates an interdependency between the two.