bluuebunny/crossref_metadata_2025_split huggingface dataset:
Constitutive model of the TWIP effect in a polycrystalline high manganese content austenitic steel
Authors: Allain Sébastien , Chateau Jean‐Philippe , Bouaziz Olivier 
Published: December 2016

The TEM study of our steel with a high manganese content reveals that mechanical twining (TWIP effect) occurs during the deformation at room temperature. Microtwins are organised into parallel stacks and two systems are sequentially activated in each grain. They participate to the deformation and they are strong obstacles for the dislocations and for other twins, leading to the decrease of the effective grain size. Thus, TWIP provides our alloy a very good ductility and a high hardening rate.Our constitutive modelling deduced from a model proposed by Bouaziz and Guelton [4] integrates this typical organisation of microtwins. Twinning is quantified in each grain by the partial volume fraction of twins in each system. A nucleation law for the microtwins is introduced which depends on the local stress and the stress relaxation due to pre‐existing twins. The flow stress is deduced from the dislocation density, which evolves with the dynamical recovery and the decrease of the mean free path (MFP). The MFP takes into account the grain and twin boundaries and the forest dislocations. The strain is calculated by adding the contributions of dislocation glide and twinning accounting the orientation of the grain. To treat the polycristal, the behaviours of different grain orientations are mixed by assuming at each strain step that the increment of elastic energy stored is the same in each grain.The model was successfully applied to describe the mechanical properties of our alloy, for two different grain sizes. Some microstructural parameters are yet fitted. This leads to an insufficient prediction of the evolution of the microstructure. In further developments, we expect to introduce numerical simulation results on local characteristics of microtwins (thickness, critical resolved shear stress for twinning) and experimental results on the rate of twin nucleation.
Bubble Entrapment on Solidified Shell caused by Unsteady Steel Flow in Mold
Authors: Miki Yuji , Takeuchi Shuji 
Published: December 2016

The molten steel flow in the continuous casting mold and entrapment of inclusions and bubbles on the inner surface of the solidified shell are examined to clarify the mechanism of internal defects in steel products. Defects on steel sheets are caused by bubbles and inclusions entrapped on the solidified shell during casting. It was found that bubbles penetrate deeply due to an unbalanced time‐dependent flow. This phenomenon can be explained by the Large Eddy Simulation model, which can predict the time‐dependent flow.The number of inclusions increases as the bubble diameter and the distance of the position of entrapment from the top free surface increase. This indicates that bubbles collect inclusions while traveling in the molten steel in the continuous caster. A simple mathematical model is presented to explain the mechanism by which inclusions become attached to bubbles.
Effects of Solute Elements on Primary and Secondary Dendrite Arm Spacings in Fe‐based Alloys
Authors: Kudoh Masayuki , Wo Bo 
Published: December 2016

There have been many experiments and theoretical studies of primary dendrites, and most of which have focused on the effects of extrinsic factors such as solidification rate and temperature gradient. However, intrinsic factors such as the kind of solute element and initial solute concentration are also considered to be important for controlling the spacing of primary dendrites.In this study, the effects of intrinsic factors on primary and secondary arm spacings of dendrites were investigated, and changes in a microsegregation index with changes in primary arm spacings and equilibrium distribution coefficient of each solute element were also examined. Fe‐Cr‐C, Fe‐C‐Cr, Fe‐C‐Cr‐Mo, Fe‐C‐Cr‐Mo‐V and Fe‐C‐Cr‐Mo‐V‐W alloys were solidified unidirectionally and water‐quenched. The primary arm spacing increased with increase in initial solute concentration in all alloys because the range of solidification temperature increased with increase in solute concentration. On the other hand, the secondary arm spacing in all alloys decreased with increase in initial solute concentration, and it was proportional to about the one‐third root of local solidification time. The microsegregation index increased with increasing primary arm spacing and with decreasing equilibrium distribution coefficient.
Modelling of EAF Off‐Gas Post Combustion in Dedusting Systems using CFD Methods
Authors: Tang Xin , Kirschen Marcus , Abel Markus , Pfeifer Herbert 
Published: December 2016

To comply with the increasingly strict environmental regulations, the poisonous off‐gas species, e. g. carbon monoxide (CO), produced in the electric arc furnace (EAF) must be treated in the dedusting system. In this work, gas flow patterns of the off‐gas post combustion in three different dedusting system units were simulated with a computational fluid dynamics (CFD) code: (1) post combustion in a horizontal off‐gas duct, (2) post combustion in a water cooled post combustion chamber without additional energy supply (no gas or air/oxygen injectors) and (3) post combustion in a post combustion chamber with additional energy input (gas, air injectors and ignition burner, case study of VAI‐Fuchs GmbH).All computational results are illustrated with gas velocity, temperature distribution and chemical species concentration fields for the above three cases. In case 1, the effect of different false air volume flow rates at the gap between EAF elbow and exhaust gas duct on the external post combustion of the off‐gas was investigated. For case 2, the computed temperature and chemical composition (CO, CO2 and O2) of the off‐gas at the post chamber exit are in good agreement with additional measurements. Various operating conditions for case 3 have been studied, including different EAF off‐gas temperatures and compositions, i. e. CO content, in order to optimize oxygen and burner gas flow rates. Residence time distributions in the external post combustion chambers have been calculated for cases 2 and 3. Derived temperature fields of the water cooled walls yield valuable information on thermally stressed parts of post combustion units.The results obtained in this work may also gain insight to future investigation of combustion of volatile organic components (VOC) or formation of nitrogenoxide (NOx) and permit the optimization of the operation and design of the off‐gas dedusting system units.
Softening Behaviour after Deformation in the Austenite‐Ferrite Two‐Phase‐Region
Authors: Bleck Wolfgang , Herzig Caroline , Venkatraman Mahadevan 
Published: December 2016

Detailed knowledge of the material behaviour during austenite decomposition is of great importance for the development of new strategies in hot strip rolling, like direct and hot charging or ferritic rolling, as well as for the development of new steel grades. Especially the influence on flow curves, precipitation behaviour and microstructure in the hot strip is relevant.Two steels were investigated with regard to their softening behaviour in ferrite, ferriteaustenite and austenite region. An Avrami type modelling approach, based on the experimental softening results and the microstructural investigation was applied to model the softening in the two‐phase‐region. Thus the quantitative prediction of the softening can be found as a function of temperature, strain rate and interpass time.
Prediction of Material Spreading in Hot Open‐Die Forging
Authors: Knap Matjaž , Kugler Goran , Palkowski Heinz , Turk Radomir 
Published: December 2016

Prediction of spreading during the hot open‐die forging process is a key issue in the optimal control of forging technology. Exact measurements of the cross‐sectional shape and dimensional changes during forging in industry are very complicated and demand large financial investment, but on the other hand, their contribution to optimization during the forging phase is not essential. Hence the only reasonable choice is to make optimization during the technological planning stage, i.e. before the actual forging. The use of physical simulations and results from forging in the laboratory has confirmed that the ratio between the contact area length and work piece width is not the only influence on material spreading. Additionally, two geometrical parameters, the ratio between the width and the height of the cross‐section and the relative deformation, as well as the temperature of the forged piece must be considered. It is important to treat each material in the model separately.For prediction of spreading two approaches were chosen, i.e. description in the form of a function in which the coefficients are specific for each grade of steel, and prediction by the application of the neuronal network approach (CAE NN – Conditional Average Estimator, Neural Networks). Each of the approaches has its own characteristics: prediction with CAE NN is more accurate than the description in the form of a function, but the latter is more suitable for modelling hot open‐die forging technology.
Recycling of By‐Product Pellets as Burden in the Blast Furnace Process: A Lab and Pilot Scale Investigation
Authors: Robinson Ryan , Sundqvist Ökvist Lena 
Published: December 2016

Cold bonded by‐product briquettes have been recycled in the blast furnace at SSAB Tunnplåt in Luleå since 1993. Recently, much effort has been made to increase the recycling of by‐products. One such project deals with the development of a cold bonded by‐product pellet (CBP) agglomerated from very fine dusts. The pellets used in these tests are produced from a blend containing BF flue dust, filter dust, briquette fines and BOF coarse dust as well as cement binder.The pellets were tested in the laboratory by reduction tests, softening and melting tests, thermo gravimetric analysis, differential thermo analysis, and mass spectrometry measurements. The test results indicate that the CBPs can disintegrate during reduction in the BF shaft, are self‐reducing to a high extent and, as a supplement to the normal ferrous burden, they show quite good softening and melting properties. A pilot scale test in LKAB's experimental blast furnace was performed. CBPs were charged with rates of 150 kg/tHM, 299 kg/tHM and 344 kg/tHM respectively during test periods 1, 2 and 3. The blast furnace operation was very stable during test period 1 with 150 kg CBP/tHM, but the burden descent and gas distribution were disturbed during the periods with greater CBP burden content. The rate of reducing agents was significantly decreased and slag amount was increased when CBPs were charged.
One Modified FE‐model to Simulate the Process Chain of Forming and Welding
Authors: Zaeh Michael F. , Roeren Sven 
Published: December 2016

This paper presents a possibility of creating a virtual process chain consisting of forming and welding. Independent of any manufacturing process, a variable Finite Element model is introduced. This model can be an input for more than one simulation by means of the Finite Element Method (FEM). The process chain forming and welding is chosen to demonstrate the need and the importance to simulate a process chain in comparison to a single process simulation.Each simulation has its own specifications and intentions. Therefore, an FE‐model for a forming simulation is different from a model for a welding simulation. In this paper a way is shown how to keep the model and the results of a forming simulation for the succeeding simulation of welding. The results of the forming simulation remain as an initial state in the welding simulation. Thereby, a spring‐back behaviour can be modelled. A few adjustments have to be done to satisfy the specifications of the welding simulation. The used material for the integrated simulation is a DC 04 steel. Therefore, metallurgical phases must be considered to achieve sufficient results. For reasons of further industrial applications commercial FE‐solvers are used for calculations.The method of integration is applied to different examples. The verified results are presented and discussed. The simulated transient distortional behaviour of a formed and welded part is presented and compared to a mere welding simulation. A significant improvement of the distortion as a result of the welding simulation is reached by consideration of a previous forming simulation.
Viscosities of Slags ‐ an Overview
Authors: Seetharaman Seshadri , Mukai Kusuhiro , Sichen Du 
Published: December 2016

Viscosities of slags constitute an important physical property needed for an understanding of the mass transfer phenomena in metallurgical processes. Viscosity is also the key that leads to a better understanding of the structure of slags. It is well‐known that the viscosities of silicate slags decrease with the addition of basic oxides due to the breaking of the silicate network.The measurements of slag viscosities often pose experimental challenges, especially with respect to the choice of materials. This paper takes up the experimental problems and the various techniques adopted. Dynamic viscosity measurement, as a powerful tool towards an understanding of the kinetics of some high temperature reactions is brought out.A number of semi‐empirical models have been developed to estimate the slag viscosities in the case of multicomponent slags. A critical survey of these models is presented in this paper. Earlier models by Riboud et al., Urbain et al. and Mills et al. have been developed further into a new generation of models. Some of the current important models are, (1) Model by lida et al., (2) CSIRO model, (3) Pyroresearch Model, (4) Model by Tanaka et al., (5) Model approach by Reddy et al., and (6) KTH‐model. The predictions and capabilities of the various models are compared. Estimations of viscosities from thermodynamic data and prediction of liquidus temperatures from viscosities are presented. The concept of surface viscosities with reference to slags and viscosities of two‐phase mixtures are also taken up in the presentation.
The Thermodynamic Properties of Fe‐Mn‐C Melt at Reduced Pressure
Authors: Wang Haichuan , Wang Shijun , Zhou Yun , Gao Li , Dong Yuanchi , Sun Haiping 
Published: December 2016

The solubility of carbon in the Fe‐Mn‐C system was measured under reduced pressure of 1 Pa at 1573 K and 1673 K, respectively. The carbon solubility in terms of mole fraction in the iron based solution was found varying with manganese mole fraction in the solution and with temperature, as xC= 0.1819 + 0.2531 xMn at 1573 K and xC = 0.1981 + 0.2515xMn at 1673K. Manganese has a stronger influence on the carbon solubility at lower pressure than it has at higher pressure. The pressure was found to have an insignificant effect on the carbon solubility when manganese in the melt was absent.The activity interaction parameters between manganese and carbon in the alloy were determined from carbon solubilities at 1573 and 1673 K. Analysis of the experimental results showed that under vacuum conditions, the activity interaction parameter of manganese with carbon is higher than that at atmospheric pressure.
Finite‐Element Implementation of a Self‐consistent Texture Model with a Hardening Law Based on Dislocation Densities
Authors: Walde Tom , Gumbsch Peter , Riedel Hermann 
Published: December 2016

A self‐consistent texture model is implemented in the finite‐element code ABAQUS/Explicit®. Hardening of the slip systems is described by evolution laws for dislocation densities, and the Bauschinger effect is included. With these ingredients the cold rolling of an IF‐steel is simulated and the evolution of texture and anisotropy is examined. The use of the dislocation based hardening law is found to have a significant effect on the evolution of the anisotropic yield surface, but only very little influence on the texture.Furthermore, the hardening model is used to investigate the evolution of dislocation densities in differently oriented grains during plane strain compression. It is found that the dislocation density varies greatly depending on orientation, an observation which can help to explain the orientation dependence of recrystallization.
Weld Quality Assessment and Actions
Authors: Jonsson Bertil , Samuelsson Jack 
Published: December 2016

Since 1989, Nordic industries, organizations and universities have co‐operated in numerous projects related to the design and fabrication of welded structures. In a current ongoing project, QFAB, over 20 participants are working together to improve the design, fabrication and cost effectiveness of complex welded structures.This paper describes the background to this project and will also discuss the process of quality assessment of welded construction machinery. The main part of the supporting framework on vehicles consists of welded steel structures. These welds contain defects and imperfections from the weld process itself and when severe load conditions are present, a finite life is at hand. The competition among manufacturers towards higher productivity and lower fuel consumption drives the engineers to design lighter structures preferably in high strength material. Such a design requires a higher weld quality and calls special attention to design and manufacturing of welds. A major issue is thus to form a scientific and consistent base which can be used when analysis and design is integrated with production and quality inspection of components. The goal is to build world class vehicles for operation without failures in service during the economic life.
Numerical Assessment of Rectangular Straight/Reverse Mufflers at High-Order-Modes
Authors: Chang Y. C. , Lin D. Y. , Cheng H. C. , Chiu M. C. 
Published: December 2016

AbstractThere has been wide-spread use of plane wave theory in muffler design in industry. However, This has led to an underestimation of acoustical performances at higher frequencies. To overcome the above drawback, the finite element and boundary element methods have been developed. Nevertheless, the time consumed in calculating the noise level is unacceptable. Moreover, considering the acoustical effect and necessity of space-constrained situation in industry, a compact design of reverse mufflers which may improve the acoustical efficiency is then proposed.In this paper, a numerical assessment of rectangular mufflers hybridized with straight/reverse chambers using eigen function, four-pole matrix, and genetic algorithm under limited space is developed. Before the optimization is performed, an accuracy check of the mathematical models for the muffler will be carried out. Results reveal that the noise reduction will increase when the number of chambers increases. In addition, the acoustical performance of the mufflers is reversely proportional to the diameter of the inlet/outlet tubes. Also, the TL of the mufflers will be improved when using more number of target tones in the objective function. Consequently, a successful approach in searching optimal shaped rectangular straight/reverse mufflers using an eigen function and a genetic algorithm method within a constrained space has been demonstrated.
Modelling durum wheat (Triticum turgidum L. var. durum) grain protein concentration
Authors: ORLANDO F. , MANCINI M. , MOTHA R. , QU J.J. , ORLANDINI S. , DALLA MARTA A. 
Published: December 2016

SUMMARYThe goal of the present study was to improve the CERES-wheat model simulation of grain protein concentration (GPC) for winter durum wheat and to use the model as a basis for the development of a GPC Simplified Forecasting Index (SFIpro). The performances of CERES-wheat, which is one of the most widespread crop simulation models, with (i) its standard GPC routine and (ii) a novel equation developed to improve the model GPC simulation for durum wheat, were assessed through comparison with field data. Subsequently, CERES-wheat was run for a 56-year period in order to identify the most important status and forcing variables affecting GPC simulation. The number of dry days during the early growth stages and the leaf area index (LAI; green leaf area per unit ground surface area) at heading stage (LAI5) were identified as the main variables positively correlated with CERES-wheat predicted GPC, and so included in the SFIpro. At validation against observed data SFIpro was found to perform differently on the basis of observed plant LAI. In fact, SFIpro was able to forecast GPC variability for intermediate values of LAI5 ranging from 1 to 2, while it totally failed when LAI5 was outside this range (LAI5 < 1 or LAI5 > 2). The results suggest that the relationship between LAI and GPC is not linear and that the model assumptions for GPC simulation in CERES-wheat are only partially confirmed, being valid for an intermediate range of LAI.
Risk of gestational diabetes mellitus in relation to maternal dietary calcium intake
Authors: Osorio-Yáñez Citlalli , Qiu Chunfang , Gelaye Bizu , Enquobahrie Daniel A , Williams Michelle A 
Published: December 2016

AbstractObjectiveThe present study sought to examine the association between dietary Ca intake and risk of gestational diabetes mellitus (GDM).DesignWe assessed periconceptional (i.e. before conception and early pregnancy) Ca intake and consumption of foods rich in Ca using an FFQ among 3414 participants in a prospective cohort study. Diagnoses of GDM were abstracted from medical records. We used multivariable generalized linear regression models to derive estimates of relative risk (RR) for GDM and 95 % confidence intervals.SettingA prospective cohort of women in Seattle and Tacoma, WA, USA.SubjectsWomen (n 3414).ResultsA total of 169 GDM incident cases were identified in the cohort (4·96 %). Higher dietary Ca intake was inversely, although not statistically significantly, associated with GDM risk. After adjusting for confounders, the RR (95 % CI) for GDM according to successive increasing quartile of Ca intake was 1·00, 0·63 (0·41, 0·98), 0·66 (0·39, 1·11) and 0·57 (0·27, 1·21), respectively, with the lowest quartile as the reference (Ptrend=0·131). Compared with women in the first quartile for Ca intake, women in the higher three quartiles (≥795 v. <795 mg/d) had a 42 % (RR=0·58; 95 % CI 0·38, 0·90; P=0·015) lower GDM risk. GDM risk was inversely associated with low-fat dairy (Ptrend=0·032) and whole grains (Ptrend=0·019) consumption.ConclusionsThese findings suggest that higher levels of periconceptional Ca intake, particularly intake of Ca-rich low-fat dairy products and whole grains, are associated with lower GDM risk.
Supplemental Nutrition Assistance Progam benefits and emergency room visits for hypoglycaemia
Authors: Heflin Colleen , Hodges Leslie , Mueser Peter 
Published: December 2016

AbstractObjectiveThe present study examines the connection between the timing and size of Supplemental Nutrition Assistance Program (SNAP) benefits and the occurrence of emergency room (ER) visits for hypoglycaemia, a condition that is highly sensitive to short-term changes in nutritional intake.DesignWe used administrative data from Missouri SNAP and Medicaid to identify the timing of issuance and the benefit size of SNAP and the timing of ER claims for hypoglycaemia. We estimated the probability of submitting an ER claim for hypoglycaemia as a function of the calendar week, SNAP benefit week and the size of the SNAP benefit in models that controlled for individual demographic characteristics.SettingMissouri SNAP caseload from January 2010 to December 2013 linked to adult Medicaid claims data for the same time period.SubjectsER claims submitted to Medicaid (n 6 508 061).ResultsThe results indicated no evidence of a SNAP benefit cycle or monthly cycle to ER claims for hypoglycaemia. However, the analysis did find that ER claims for hypoglycaemia are related to the size of the SNAP benefit.ConclusionsThese results suggest that more generous SNAP benefits help households avoid nutritional fluctuations in the quality and quantity of food that might result in low blood sugar, thus necessitating fewer ER visits for hypoglycaemia.