Results of numerous variants of numerical simulations of casting processes serve as training and test data to teach and test artificial neural networks. The data base is generated with a commercial simulation program, MAGMASOFT. The optimization function of this software can be used to automatically generate the data needed for training and testing. In addition to suitable standard modules for data preparation, the widely used open-source programming language Python also has modules for the generation and optimization of artificial neural networks (e.g., TensorFlow). This makes it possible to build a network that makes sufficiently accurate predictions of target process variables when the relevant input parameters are fed in. With a trained network, the target variables can be obtained not only for a particular but for any variation of all input process parameters in their respective ranges. To be able to train a network in a meaningful way, the essential input process parameters affecting the target variables must be known. This limitation results from the exponential increase of variations for generating training data by means of simulation. In this work, examples of trained neural networks with up to eight input variables are presented, resulting in about ten thousand needed simulation variants. The purpose of this work is to establish methods to save computation time in numerical simulations by substituting a process phase (e.g., shot chamber filling or piston moving in high-pressure die casting) by a surrogate model. Another shown application is a porosity prediction model for gravity die-casting case, which is also shown as example.

Wood is a structural material of biological origin that undergoes thermal degradation when exposed to high temperatures. Additionally, wood shows an anisotropic behavior in terms of thermal expansion and thermal conductivity along and across fiber direction. This work reports thermophysical measurements of beech wood from room temperature up to 900 °C. The wooden material was investigated in different states: moist, dry, charred and during pyrolysis. A push-rod dilatometer was used to measure thermal expansion, from which temperature dependent density was derived. Specific heat was determined by differential scanning calorimetry. A laser flash apparatus was applied to measure thermal diffusivity. Thermal conductivity was calculated from thermal diffusivity, specific heat, and density. The measurements of thermal expansion and thermal diffusivity were performed along and across fiber direction to consider the anisotropic behavior of wooden material. The results of the thermophysical properties are reported from room temperature to 200 °C for the beech wood, during pyrolysis, and up to 900 °C for the charred material. It was found that thermal expansion of beech wood across fiber direction is greater than along fiber direction in the order of a magnitude. In contrast, thermal expansion of charred material is rather independent on fiber direction. Thermal conductivity of beech wood along fiber direction was found to be approx. 2 to 3 times higher than across fiber direction. In the case of the charred material the relative difference is smaller.

AA7075 is one of the most resistant aluminium alloys, so it is frequently used in very demanding industries as aeronautics or defence. However, the 7075 alloy falls into the non-weldable category thus hardly processable through additive manufacturing processes, and specially on laser-based DED (Directed Energy Deposition). The low absorption together with cracking behaviour remain a challenge for the industrialisation of these processes. Alloying with minor elements or addition of nano-reinforcement have been proven as a successful approach to increase its manufacturability. In this work, the feasibility of printing 7075 with nano-TiC as additive was evaluated. Two compositions with 0.5 and 2% in weight were developed by dry mixing. The powders were characterized by scanning electron microscopy (SEM) and flowability was compared with the unreinforced alloy. With the optimal laser process parameters, 3D coupons were printed to be characterized microstructurally, thermally, and mechanically. Process monitoring using thermal and high-speed cameras was carried out to gain insight into the thermal behaviour of the melt-pool and resulting process stability. After printing, aspect ratio of single tracks was measured, and dilution was also evaluated. Although addition of 0.5% of n-TiC promotes a slight improvement on the alloy, allowing it to be mechanically tested, it still presents some defects as porosity. By increasing the content up to 2%, both the quality and the mechanical performance were enhanced significantly.

NIST SRM 1155a is an AISI 316L stainless steel (Cr18–Ni12–Mo2) and Standard Reference Material (SRM) intended for use with test methods for elemental analysis. In a previous paper “Measurement of thermophysical properties of solid and liquid NIST SRM 316L stainless steel”, we already published reliable thermophysical properties of high temperature solid and of the liquid phase of this material such as temperature dependent enthalpy, density and electrical resistivity, as well as specific heat capacity for the solid and the liquid phase. In this paper, we add additional thermophysical properties obtained by ohmic pulse-heating and by the laser flash method, namely thermal conductivity and thermal diffusivity as a function of temperature. Furthermore we report surface tension measurement results of liquid SRM 1155a obtained by means of electromagnetic levitation. Simulation of processes like additive manufacturing, laser welding, laser cutting or metal casting depend on the above named quantities as input data. Ohmic pulse-heating as well as electromagnetic levitation are so called “containerless” investigation techniques and no significant chemical reactions of the hot liquid alloy with its surrounding occur. The data presented here are compared to the available literature data and are accompanied by an uncertainty analysis according to the “Guide to the Expression of Uncertainty in Measurement”.

Since March 2014, all ESA satellites and launcher upper stages which will be disposed of by atmospheric re-entry at the end of their operational life must demonstrate that the risk from fragments surviving the re-entry and causing casualties on ground is less than 1 in 10,000. This casualty risk is calculated by re-entry tools simulating the uncontrolled re-entry event using a computer aided design model of the spacecraft. The uncertainties on several parameters such as the aerothermodynamics fluxes model, the structural interfaces model, the materials model, and the level of detail of the spacecraft architecture will have an impact on the re-entry event simulation and the associated casualty risk calculations. To better understand the uncertainties associated to material modelling, five materials often used on space missions were tested in Plasma Wind Tunnels, mimicking atmospheric re-entry environment. Thermo-physical properties, thermo-optical properties and mechanical properties at high temperature were also characterized. Analysis of the samples after plasma wind tunnel tests was performed. A database compiling the materials properties measured and the plasma wind tunnel test results was created. The material properties characterised and generated during the activities will serve as inputs for the re-entry simulation events at equipment and system level.

The casting of liquid melt on a preheated substrate layer to produce a metallurgical compound represents a direct approach towards clad aluminum strips. To investigate this direct process route and the formation of a metallurgical bond at the interface, a small-scale pilot plant to cast pure aluminum on strips of aluminum alloy 7075 under controlled conditions was developed. Composite casting plates were produced at varying casting parameters (preheating temperature of the substrate, clad layer thickness, casting speed, melt temperature) and subsequently analyzed by metallographic means to classify the bond quality.Suitable thermal conditions for the melt flow in the casting device were found by numerical simulation using a commercial fluid flow and solidification software package. Additional meso- and micro-modeling of the casting and the bonding zone supported the understanding of the bonding mechanism. The heat transfer in the macro-model of the casting device was calibrated using measured temperatures obtained during compound casting experiments. A finer meshed two-dimensional meso-model of the casting device was derived from the macro-model to gain more accurate information about the temperature distribution in the vicinity of the bonding zone. This interface between the pure aluminum and the aluminum alloy was modeled in extremely high temporal and spatial resolution (micro-model) as temperatures are not accessible there by direct measurements. These simulation results show the time-resolved re-melting and re-solidification of the aluminum alloy during compound formation. The obtained simulation results correlate very well with electrochemically etched cross sections of cast bilayer aluminum strips.The experiments show that the oxide layer at the interface has to be removed completely during the casting process to obtain high quality compounds. The assumed mechanism of detachment and transport of the fractured oxide is shown schematically and necessary thermo-mechanical conditions for the removal of the oxide skin are discussed.

Water vapour in porous building materials significantly affects the heat transfer. In addition to the regular humidity, materials, such as gypsum, release water vapour when they are heated, leading to a high resistivity to fire exposure. Although the heat and water vapour transfer through porous building materials at atmospheric conditions is well investigated, no data are available for the effective diffusion coefficient or velocity of the water vapour transfer when the structure is exposed to a thermal load or fire. For this purpose, fire resistance tests were carried out for gypsum/mineral wool constructions to determine the transient heating characteristic and water vapour transfer. It was found that for thin gypsum structures up to 2.5 cm the heating from ambient temperature to 65 degrees C is mainly caused by conduction. Further heating to 100 degrees C is related to the condensation of water vapour instead of thermal heat conduction. Furthermore, a significant decrease of the effective diffusion coefficient of water vapour in the mineral wool from 33.3 mm(2)/s to 26.7 mm(2)/s was determined during fire exposure. Based on the measurement the mean velocity of the water vapour transport was determined of being between 1 and 3 mm/s. (C) 2020 Elsevier Ltd. All rights reserved.

Selected thermophysical properties of the hot work tool steel AISI H11 (1.2343) were measured in the temperature range from room temperature to the melting temperature. Thermal diffusivity was measured by the laser-flash method; heat capacity by differential scanning calorimetry; linear thermal expansion by push-rod dilatometry; and density at room temperature by an Archimedean balance. From these experimentally obtained data, thermal conductivity was calculated.Additionally, electrical resistivity of AISI H11 (1.2343) was measured by millisecond pulse-heating in the above mentioned temperature range. The measurement results of electrical resistivity as a function of specific enthalpy was combined with results of specific heat capacity measurements by differential-scanning calorimetry to obtain the relation between resistivity and temperature.Based on measured electrical resistivity and thermal conductivity, a Smith-Palmer-plot for the hot work tool steel AISI H11 (1.2343) is obtained for the ferritic and austenitic phases. No linear behaviour – as expected by the Wiedemann-Franz law – is observed in the ferritic phase region. In the high temperature austenitic region, the thermal conductivity can be computed from electrical resistivity using empirical constants of similar austenitic steels or superalloys.

Density and thermal expansion of the nickel-based superalloy INCONEL 625 were measured in the temperature range 150 °C to 1400 °C using pushrod and piston dilatometry. Commercial pushrod-dilatometers were used for the measurements. The specimens are cooled and heated slowly at controlled rates in a furnace; the expansion is transferred by a long thin rod to displacement sensors. In the high temperature range an alumina tubular body with two alumina pistons of just sufficient clearance was used to contain the specimen in the mushy region and in the liquid state The investigated material was primary heat treated at 930 °C for 1 hour. As INCONEL 625 is an age-hardening alloy, the thermophysical properties including density at elevated temperature depend slightly on heat treatment conditions. Therefore, different measurement runs with a variation of the maximum temperature in the solid state (from room temperature to 1000 °C, 1100 °C and 1250 °C) were performed to cover different heat treatments (product grades) of INCONEL 625. Due to the lack of density and thermal expansion data of INCONEL 625 in the solid and liquid states in the literature, the measured density is compared to published density data of INCONEL 718 and INCONEL 738. A detailed uncertainty analysis of the measured data in the solid and liquid state of the alloy is provided.

Selected thermophysical properties of Inconel 625 were measured in continuation of our work on the comparison between thermal conductivity and electrical resistivity for different alloys. In contrast to pure metals, alloys usually show significant deviations from the Wiedemann–Franz law using the theoretical Sommerfeld value. Two experimentally determined constants can take into account mainly lattice and electron scattering contributions (Smith–Palmer plot), re-establishing a well-defined relation between thermal and electrical conductivity. Thermal diffusivity of Inconel 625 was measured by the laser flash method in the temperature range − 120 °C to 1250 °C; heat capacity was measured by differential scanning calorimetry in the temperature range − 170 °C to 1250 °C; thermal expansion was measured by dilatometry in the temperature range − 150 °C to 1295 °C (solidus temperature). Density at room temperature was measured by an Archimedean balance. From these experimentally obtained data, thermal conductivity was calculated in a wide temperature range. Electrical resistivity of Inconel 625 was measured by millisecond pulse heating in the temperature range from room temperature to the solidus temperature. The measurement results of electrical resistivity as a function of specific enthalpy were combined with results of specific heat capacity measurements to obtain the relation between resistivity and temperature.

This work presents experimental results of thermal diffusivity and computed values of thermal conductivity of pure polycrystalline ruthenium specimens in the temperature range 200 to 1670 K for diffusivity and 250 to 1650 K for conductivity. The results of thermal diffusivity were obtained by an interlaboratory comparison using the laser flash method. A brief description of the two measuring systems applied is given. Specimens were disk shaped, 2 and 3 mm in thickness and 10 and 12.5 mm in diameter. Literature data are used to correct for thermal expansion of the specimens. All the values obtained from the individual laboratories as well as a polynomial fit to the results over the entire temperature range are presented and compared with results found in literature. By using the thermal diffusivity data and previously measured results of specific heat capacity of different pure polycrystalline ruthenium specimens, the values of ruthenium thermal conductivity are estimated and presented together with related literature data.

Electrical resistivity of stainless steel AISI 316 L was measured by millisecond pulse-heating in the temperature range from room temperature to the melting point at approximately 1400 degrees C. The measurement results of electrical resistivity as a function of specific enthalpy were combined with results of specific heat capacity measurements by differential scanning calorimetry to obtain the relation between resistivity and temperature. Additionally to electrical resistivity and specific heat capacity, thermal diffusivity, density at room temperature, and thermal expansion were measured. From these results, thermal conductivity was calculated. Using the results of thermal conductivity and electrical resistivity, a Smith-Palmer-plot was drawn. It shows a significant deviation from the Wiede-mann-Franz law with the Sommerfeld value due to the lattice component, electron scattering by solute atoms, and other smaller contributions.

The surface tension of liquid Cu–5Sn (copper with 5 wt% tin) in the temperature range from 1290 K to 1560 K was measured by an oscillating drop technique combined with electromagnetic levitation. The levitation device uses an inhomogeneous radiofrequency electromagnetic field inside a levitation coil to position and to heat metallic material. Eddy currents are induced in a specimen to heat it to the liquid phase and to exert a Lorentz force, pushing it against gravity towards regions of lower field strength. The levitating liquid specimen takes the shape of a sphere, which is rotating and oscillating. The oscillations are recorded by a high-speed camera at 600 fps ; the temperature of the specimen is measured by a fast near-infrared pyrometer. A linear fit to the measured surface tension γ of Cu–5Sn as a function of temperature T in Kelvin is given by: γ (T)(mN·m^-1)=1195-0.052· (T-1318).

A new belt casting process has been developed to cast aluminum-aluminum alloy compound strips. The first strip is cast by a conventional glass fiber belt caster. At a defined distance front the location of the primary solidification, a second casting unit is placed. The local upper surface temperature of the substrate is essential for the forming of a sound metallurgical compound. Numerical simulation models of an existing single strip belt casting process were set up and extended to describe the new double strip casting process. The influence of process parameters (cooling conditions, casting speed) and constructive modifications on the crucial surface temperature of the substrate were investigated. Temperatures measured in the casting strip and in the cooling plates were used to calibrate the simulations. Casting parameters for the new compound casting process as well as the appropriate position of the second casting unit were derived from the simulation results.

This work presents two three-dimensional solidification models, which were solved by several commercial solvers (MAGMASOFT, FLOW-3D, ProCAST, WinCast, ANSYS, and OpenFOAM). Surprisingly, the results show noticeable differences. The results are analyzed similar to a round-robin test procedure to obtain reference values for temperatures and their uncertainties at selected positions in the model. The first model is similar to an adiabatic calorimeter with an aluminum alloy solidifying in a copper block. For this model, an analytical solution for the overall temperature at steady state can be calculated. The second model implements additional heat transfer boundary conditions at outer faces. The geometry of the models, the initial and boundary conditions as well as the material properties are kept as simple as possible but, nevertheless, close to a realistic solidification situation. The gained temperature results can be used to validate self-written solidification solvers and check the accuracy of commercial solidification programs.

A thermal process window to form a stable metallurgical compound of AlSn6Cu and Al99.5 was obtained by initial experiments. A special mould system for a horizontal continuous composite casting process was developed, supported by finite element simulations. Preliminary 2D models were used to identify the main process variables influencing the temperature in the region where the compound is formed between the two layers. The thickness ratio of the layers and the initial temperature of the AlSn6Cu substrate strip were found to be the most important parameters. The special bilayer mould system was manufactured and implemented into an existing continuous casting device upgraded by a second furnace to hold the additional pure aluminium. A stable casting process was achieved. The quality of the manufactured compound was assessed by metallographic specimens cut from the obtained bilayers. Based on temperature measurements, a full 3D finite element model was developed to gain a more realistic description of the temperature and fluid flow conditions in the composite casting, especially in the margin regions.

Electrical resistivity of two grades of aluminium alloy Al-7Si-0.3Mg was measured by millisecond pulse-heating in the temperature range from room temperature to 450 C. The first grade is an industrial standard material; the second is high purity grade with a low content of Ti and Zr. The measurement of electrical resistivity as a function of specific enthalpy was combined with specific heat capacity measurements by differential-scanning calorimetry to obtain the relation between resistivity and temperature. This is necessary, since a contactless temperature measurement was not possible due to the low sensitivity of our pyrometers of the millisecond pulse-heating system. Additionally to electrical resistivity and specific heat capacity, density at room temperature, thermal diffusivity, and thermal expansion was measured. From these results, thermal conductivity was calculated. Comparing thermal conductivity to electrical resistivity, the Lorenz number can be computed for the entire temperature range. The higher purity alloy shows a significant lower electrical resistivity and an equivalent increase in thermal conductivity. Different forms of the Wiedemann-Franz law found in the literature were compared using the results of the measured thermophysical properties, showing that the use of the simplest form gives the best match for this highly conducting aluminium alloy.

Typical casting defects are known to influence the mechanical properties of castings massively. In contrast to common non-destructive test procedures computed tomography (CT) permits the detection of these defects three-dimensionally (3D). However, there is no standard for the assessment of CT data regarding 3D defect distributions and their correlation with mechanical properties so far. The present work is aimed at a standardized description of porosity in aluminium cast parts by means of CT. For this purpose material testing specimens of two different aluminium alloys were produced by high pressure die casting and scanned with a micro-focus CT facility with a resolution of 100 µm. For the volume porosity analysis a reference body with known void volume was designed permitting the determination of the adequate grey scale threshold. After the mechanical testing the CT scans were re-analysed regarding the local volume porosity at the crack. A distinct correlation between this local volume porosity and the mechanical properties of flat tensile specimens of industrial Al alloys was determined. Furthermore detailed investigations have taken into account the distance of the respective porosity to the sample surface as well as the shape of the porosity in order to account for its notch effect. First results have shown an influence of the porosity shape on the static-mechanical properties.

Two individual high-pressure die casting geometries were developed to study the influence of process parameters and alloy composition on the distortion behavior of aluminum alloy castings. These geometries, a stress lattice and a V-shaped lid, tend to form residual stress due to a difference in wall thickness and a deliberate massive gating system. Castings were produced from two alloys: AlSi12(Fe) and AlSi10MnMg. In the experimental castings, the influence of important process parameters such as die temperature, ejection time, and cooling regime was examined. The time evolution of process temperatures was measured using thermal imaging. Subsequent to casting, distortion was measured by means of a tactile measuring device at ambient temperatures. The measured results were compared against a numerical process and stress simulations of the casting, ejection, and cooling process using the commercial finite element method software ANSYS Workbench. The heat transfer coefficients were adapted to the temperature distributions of the die, and the castings were observed by thermal imaging. A survey of the results of the comparison between simulation and experiment is given for both alloys.

The results of an inter laboratory comparison of thermal diffusivity measurements on two different materials, namely a copper alloy (CuCrZr) and a polymer (PMMA), are presented here. Both materials were selected with respect to their different thermal conductivity, since the copper alloy belongs to the family of good metallic conductors whereas the polymer is characterized by a low thermal conductivity. The measurements of the thermal diffusivity have been performed within a temperature range from RT to 500°C for the copper alloy and from RT to 100°C for the PMMA, respectively.