scholarly journals Numerical Simulation of Full Carburizing Process of an Automotive Gear

2021 ◽  
Author(s):  
Patrice Lasne ◽  
Philippe Bristiel ◽  
Nicolas Poulain
Keyword(s):  
Thermal Stresses ◽  
Thermal Evolution ◽  
Numerical Models ◽  
Carbon Diffusion ◽  
Phase Changes ◽  
Chemical Compositions ◽  
Relative Contribution ◽  
Temperature Boundary ◽  
Transformation Diagrams ◽  
Carburizing Process

Abstract The objective of the paper is to present material and numerical models needed to simulate with accuracy the full carburizing process of an automotive gear. The rough dimensions of the gear studied are 120mm in diameter and 45mm in height. From a numerical standpoint, as the carburizing affects only a thin layer under the surface, the mesh discretization must be adapted. Consequently, anisotropic mesh is used to describe accurately this zone. The temporal discretization must be also adapted to follow carbon diffusion and thermal evolution. The material models represent metallurgical phenomena during the complete carburizing process. The initial heating of the part induces phases transformation due to austenization. Subsequently, while holding at carburizing temperature, boundary conditions are applied to diffuse carbon into the part. While carbon content increases next to the surface, austenitic metallurgical grain growth is also modelled. A final cooling sets the properties of the carburized part. The model takes into account the phase changes using phase transformation diagrams locally adapted to chemical compositions and grain sizes. Simulation is used to predict the in-use properties of the gear at the end of the carburizing process as well as important results such as assessment of distortion and residual stresses. Thermal stresses, volume variation due to phase changes, and transformation plasticity all contribute to establish the final mechanical properties of the part. During the complete process, the material is modelled with an elasto-viscoplastic behavior and mixing methods are used to consider the relative contribution of each phase.

scholarly journals Variability of the adiabatic parameter in monoatomic thermal and non-thermal plasmas

2018 ◽  
Vol 616 ◽  
pp. A58 ◽  
Author(s):  
Miguel A. de Avillez ◽  
Gervásio J. Anela ◽  
Dieter Breitschwerdt
Keyword(s):  
Internal Energy ◽  
Impact Ionization ◽  
Thermal Evolution ◽  
Numerical Models ◽  
Linear Equations ◽  
Thermal Plasmas ◽  
Specific Heats ◽  
Partial Pivoting ◽  
Electron Distributions ◽  
Collisional Ionization

Context. Numerical models of the evolution of interstellar and integalactic plasmas often assume that the adiabatic parameter γ (the ratio of the specific heats) is constant (5/3 in monoatomic plasmas). However, γ is determined by the total internal energy of the plasma, which depends on the ionic and excitation state of the plasma. Hence, the adiabatic parameter may not be constant across the range of temperatures available in the interstellar medium. Aims. We aim to carry out detailed simulations of the thermal evolution of plasmas with Maxwell–Boltzmann and non-thermal (κ and n) electron distributions in order to determine the temperature variability of the total internal energy and of the adiabatic parameter. Methods. The plasma, composed of H, He, C, N, O, Ne, Mg, Si, S, and Fe atoms and ions, evolves under collisional ionization equilibrium conditions, from an initial temperature of 109 K. The calculations include electron impact ionization, radiative and dielectronic recombinations and line excitation. The ionization structure was calculated solving a system of 112 linear equations using the Gauss elimination method with scaled partial pivoting. Numerical integrations used in the calculation of ionization and excitation rates are carried out using the double-exponential over a semi-finite interval method. In both methods a precision of 10−15 is adopted. Results. The total internal energy of the plasma is mainly dominated by the ionization energy for temperatures lower than 8 × 104 K with the excitation energy having a contribution of less than one percent. In thermal and non-thermal plasmas composed of H, He, and metals, the adiabatic parameter evolution is determined by the H and He ionizations leading to a profile in general having three transitions. However, for κ distributed plasmas these three transitions are not observed for κ < 15 and for κ < 5 there are no transitions. In general, γ varies from 1.01 to 5/3. Lookup tables of the γ parameter are presented as supplementary material.

scholarly journals Thermo-Viscoelastic Modeling of the Aircraft Tire Cornering

2015 ◽  
Vol 1099 ◽  
pp. 80-86 ◽  
Author(s):  
Iulian Rosu ◽  
Lama Elias-Birembaux ◽  
Frederic Lebon
Keyword(s):  
Thermal Evolution ◽  
Numerical Models ◽  
Frictional Heating ◽  
Mechanical Analysis ◽  
High Speeds ◽  
Numerical Studies ◽  
Deformation Dynamics ◽  
Viscoelastic Modeling ◽  
Fully Coupled ◽  
Tread Rubber

Some numerical models are proposed for simulate the aircraft tire behaviour on the ground in critical situations. Fully coupled thermo-mechanical analysis procedures taking into account finite deformation, dynamics and frictional contact are studied; the visco-elasticity properties of the rubber were identified. A good agreement is observed at moderate speed, thus the model is extrapolated to high speeds and seems able to predict results in cases for which it is not possible to obtain realistic experimental data. In order to understand the thermal evolution of tire tread rubber materials during rolling and skidding steps, new experimental and numerical studies were also realized on tire tread rubber. The aim of this approach is to simulate and understand the effect of frictional heating on the tire behaviour.

scholarly journals Occurrence and Origin of H2S from Volcanic Reservoirs in Niudong Area of the Santanghu Basin, NW China

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Xiangxian Ma ◽  
Guodong Zheng ◽  
Minliang Liang ◽  
Dianhe Xie ◽  
Giovanni Martinelli ◽  
...  
Keyword(s):  
Thermal Evolution ◽  
Chemical Compositions ◽  
Formation Water ◽  
Main Principle ◽  
Tectonic Structures ◽  
Nw China ◽  
Genetic Process ◽  
Gas Formation ◽  
Volcanic Reservoirs ◽  
Geological Background

A series of samples including natural gas, formation water, and rocks were collected from volcanic rock reservoirs in the Niudong area of the Santanghu Oilfields and analyzed for their mineral and/or chemical compositions and sulfur and carbon isotopes in order to investigate the occurrence and origin of hydrogen sulfide (H2S). H2S was mostly dissolved in the formation water along with petroleum production in the study area. The δ34S values of on-well H2S samples varied in a range of 9.2‰ to 20.5‰, probably indicating thermochemical sulfate reduction (TSR) and/or thermal decomposition of organic sulfur-bearing compounds (TDS) as the genetic process for H2S. However, the chemical composition of formation waters from the Kalagang Formation (C2k) and their coefficient of desulfurization also revealed that TSR could be the main principle for H2S formation. Considering the regional geological background, especially the tectonic structures and thermal evolution features of the basin, it was concluded that H2S in the study area was dominantly produced by thermal genesis with TSR as a domain through interactions between hydrocarbons and aqueous sulfate dissolved from sulfate minerals.

scholarly journals Interaction of Ekman Layers and Islands

2013 ◽  
Vol 43 (5) ◽  
pp. 1028-1041 ◽  
Author(s):  
Michael A. Spall ◽  
Joseph Pedlosky
Keyword(s):  
Boundary Layers ◽  
Numerical Models ◽  
Phase Changes ◽  
Ekman Transport ◽  
Return Flow ◽  
Kelvin Wave ◽  
Density Anomaly ◽  
Depth Direction ◽  
Ekman Layers ◽  
Geostrophic Flows

Abstract The circulation induced by the interaction of surface Ekman transport with an island is considered using both numerical models and linear theory. The basic response is similar to that found for the interaction of Ekman layers and an infinite boundary, namely downwelling (upwelling) in narrow boundary layers and deformation-scale baroclinic boundary layers with associated strong geostrophic flows. The presence of the island boundary, however, allows the pressure signal to propagate around the island so that the regions of upwelling and downwelling are dynamically connected. In the absence of stratification the island acts as an effective barrier to the Ekman transport. The presence of stratification supports baroclinic boundary currents that provide an advective pathway from one side of the island to the other. The resulting steady circulation is quite complex. Near the island, both geostrophic and ageostrophic velocity components are typically large. The density anomaly is maximum below the surface and, for positive wind stress, exhibits an anticyclonic phase rotation with depth (direction of Kelvin wave propagation) such that anomalously warm water can lie below regions of Ekman upwelling. The horizontal and vertical velocities exhibit similar phase changes with depth. The addition of a sloping bottom can act to shield the deep return flow from interacting with the island and providing mass transport into/out of the surface Ekman layer. In these cases, the required transport is provided by a pair of recirculation gyres that connect the narrow upwelling/downwelling boundary layers on the eastern and western sides of the island, thus directly connecting the Ekman transport across the island.

Assessment on the Thermal Stresses of Concrete Bridge Piers under Solar Radiation

2012 ◽  
Vol 204-208 ◽  
pp. 2045-2050 ◽  
Author(s):  
Pei Song Gong ◽  
Bo Chen ◽  
Chun Fang Song ◽  
Xiu Li Li
Keyword(s):  
Temperature Distribution ◽  
Boundary Conditions ◽  
Thermal Stresses ◽  
Numerical Models ◽  
Bridge Pier ◽  
Concrete Bridge ◽  
Time Varying ◽  
Thermal Boundary Conditions ◽  
Infrared Imager ◽  
Structural Temperature

The time-varying thermal stresses of a concrete pier are actively studied in this study with the aiding of the commercial package ANSYS. Thermal boundary conditions are utilized to obtain the temperature distribution of the concrete bridge pier. The surface temperature of the pier is measured by using a thermal infrared imager at different time instants. The different boundary conditions are applied to determine the structural temperature distribution and compute the thermal deformation. The made observations demonstrate that the horizontal deformation is much larger than that in vertical deformation due to the influence of the constraints on the top and bottom sides of the pier. The thermal stresses of the example bridge pier are not very large except for the local areas on top of the piers. It is seen that the numerical models can successfully predict the structural time-varying temperature effects

scholarly journals Study on Upgradation in Carburizing Technologies for steel strength

2019 ◽  
pp. 78-84
Keyword(s):  
Surface Hardness ◽  
Carbon Diffusion ◽  
Lower Surface ◽  
Diffusion Controlled ◽  
Steel Strength ◽  
Carbon Transfer ◽  
Gas Carburizing ◽  
Kinetics Of ◽  
Plasma Carburizing ◽  
Carburizing Process

Carburizing technologies are used to provide strength on low quality metals. This technology is being developing with novel improvements significantly. The carburizing process consists of, first releasing Carbon mono-oxide from charcoal material and then transfers carbon to raw metal. There are favorable upgradation in these technologies from researchers which have a paramount industrial importance. In Vacuum gas carburizing, the steel metal is carburized with (Acetylene and Propane) gases. These gases are at low pressure and high temperature. The results show that the metal is 1.5 times harder than its raw form. There are also used mathematical models to validate the results. It used gas and solid phases for validation. In pulse carburizing, carbon diffusion on steel is investigated with heat treatment. This process includes several carburizing stages. This process is based on Darken bi velocity and drift velocity. It accounts to demonstrate the kinetics of carbon transfer on steel surface. This design is very useful by regarding carburizing time for this process design. In Plasma carburizing, the mixtures of gases are used to harden the steel. The carburizing temperature was varied in cementite and martensitic. The favorable results show that these specimens have (Lower surface roughness, higher surface hardness and Low wear rate). It is a most novel diffusion controlled novel process till the present time. The carburized metal is used in industry by including (Turbine gears and Air craft engine). Henceforth, It is of great importance to study the carburizing technologies for providing better strength on metal.

Rail Neutral Temperature Estimation Using Field Data, Numerical Models, and Machine Learning

2021 ◽  
Author(s):  
Yuning Wu ◽  
Xuan Zhu ◽  
Chi-Luen Huang ◽  
Sangmin Lee ◽  
Marcus Dersch ◽  
...  
Keyword(s):  
Machine Learning ◽  
Field Data ◽  
Thermal Stresses ◽  
Numerical Models ◽  
Estimation Method ◽  
Supervised Machine Learning ◽  
Estimation Accuracy ◽  
Optimization Approach ◽  
Neutral Temperature ◽  
Wide Range

Abstract Effective Rail Neutral Temperature (RNT) management is needed for continuous welded rail (CWR). RNT is the temperature at which the longitudinal stress of a rail is zero. Due to the lack of expansion joints, CWR develops internal tensile or compressive stresses when the rail temperature is below or above, respectively, the RNT. Mismanagement of RNT can lead to rail fracture or buckling when thermal stresses exceed the limits of rail steel. In this work, we propose an effective RNT estimation method structured around four hypotheses. The work leverages field-collected vibration test data, high-fidelity numerical models, and machine learning techniques. First, a contactless non-destructive and non-disruptive sensing technology was developed to collect real-world rail vibrational data. Second, the team established an instrumented field test site at a revenue-service line in the state of Illinois and performed multi-day data collection to cover a wide range of temperature and thermal stress levels. Third, numerical models were developed to understand and predict rail vibration behavior under the influence of temperature and longitudinal load. Excellent agreement between model and experimental results were obtained using an optimization approach. Finally, a supervised machine learning algorithm was developed to estimate RNT using the field-collected rail vibration data. Sensitivity studies and error analyses were included in this work. The system performance with field data indicates that the proposed framework can support reasonable RNT estimation accuracy when measurement or model noise is low.

Transient, Three-Dimensional Numerical Model of a Laser Cutting Process With Phase Change Consideration

2004 ◽  
Author(s):  
Gustavo Gutie´rrez ◽  
Juan Guillermo Araya
Keyword(s):  
Temperature Field ◽  
Laser Beam ◽  
Phase Change ◽  
Numerical Models ◽  
Three Dimensional ◽  
Phase Changes ◽  
Ceramic Surface ◽  
Numerical Predictions ◽  
Physical Shape ◽  
Finite Volume Approach

Phase change problems are encountered in several manufacturing and material processing applications. Such problems are computationally challenging because it is necessary to solve a non-linear heat conduction equation and take into considerations the conditions needed to produce material ablation, varying continuously the heat source position, thermo physical properties and physical shape of the domain. This research presents a numerical simulation of the temperature field and the removed material resulting from the impingement of a moving laser beam on a ceramic surface. A finite volume approach has been developed to predict the temperature field including phase changes generated during the process. The model considers heat losses by convection and radiation due to the high temperatures involved and uses a coordinate system affixed to the workpiece; therefore no quasi-steady conditions are assumed, as in the majority of previous works. Numerical predictions were compared with former three-dimensional numerical models considering a semi-infinite solid and from experimental data found in the literature. This study gives insight into the interactions between the laser beam and a silicon nitride workpiece during the cutting.

Primary deformation phases during "magma-poor" rifting with special focus on the tectono-thermal evolution during the necking process

2020 ◽  
Author(s):  
Pauline Chenin ◽  
Gianreto Manatschal ◽  
Stefan M. Schmalholz ◽  
Thibault Duretz
Keyword(s):  
Lower Crust ◽  
Thermal Evolution ◽  
Numerical Models ◽  
Pure Shear ◽  
Geothermal Gradient ◽  
Special Focus ◽  
Distal Margin ◽  
Large Variability ◽  
Rifted Margins ◽  
Morphotectonic Evolution

&lt;p&gt;Although so-called &quot;magma-poor&quot; rifted margins display a large variability on a local scale, they are characterized by a number of common primary features worldwide such as their first-order architecture (proximal, necking, hyperextended, exhumation and oceanic domains), their lithological evolution along dip and the deformation processes associated with their different rifting stages. In this contribution, we first emphasize the primary morphological and lithological architecture of magma-poor rifted margins and how they relate to specific deformation modes (pure shear thinning, mechanical necking, frictional extensional wedge, detachment faulting and seafloor spreading). Second, we focus on the necking stage of rifting, which corresponds to the first major thinning event (when the crust is thinned from its initial thickness to ~ 10 km). We display the range of possible topographic and thermal evolutions of &quot;magma-poor&quot; and &quot;sedimentary starved&quot; rift systems depending on their lithosphere rheology. Our two-dimensional thermo-mechanical numerical models suggest that extension of lithospheres where the crust and the mantle are mechanically decoupled by a weak lower crust results in a complex morphotectonic evolution of rift systems, with formation of temporary restricted sub-basins framed by uplifted parts of the future distal margin. Mechanical decoupling between the crust and the mantle controls also largely the thermal evolution of rift systems during the necking phase since for equivalent extension rates and initial geotherms: (i) weak/decoupled lithospheres have a higher geothermal gradient at the end of the necking phase than strong/coupled lithospheres; and (ii) weak/decoupled lithospheres show intense heating of the lower crust at the rift center and intense cooling of the crust on either side of the rift center, unlike strong/coupled lithospheres. These behaviors contrast with the continuous subsidence and cooling predicted by the commonly used depth-uniform thinning model.&lt;/p&gt;

scholarly journals Lessons learnt from the first EMEP intensive measurement periods

2012 ◽  
Vol 12 (17) ◽  
pp. 8073-8094 ◽  
Author(s):  
W. Aas ◽  
S. Tsyro ◽  
E. Bieber ◽  
R. Bergström ◽  
D. Ceburnis ◽  
...  
Keyword(s):  
Mineral Dust ◽  
Inorganic Compounds ◽  
Measurement Data ◽  
Chemical Compositions ◽  
Aerosol Composition ◽  
Diurnal Variability ◽  
Relative Contribution ◽  
Lessons Learnt ◽  
Pm10 And Pm2.5 ◽  
First Time

Abstract. The first EMEP intensive measurement periods were held in June 2006 and January 2007. The measurements aimed to characterize the aerosol chemical compositions, including the gas/aerosol partitioning of inorganic compounds. The measurement program during these periods included daily or hourly measurements of the secondary inorganic components, with additional measurements of elemental- and organic carbon (EC and OC) and mineral dust in PM1, PM2.5 and PM10. These measurements have provided extended knowledge regarding the composition of particulate matter and the temporal and spatial variability of PM, as well as an extended database for the assessment of chemical transport models. This paper summarise the first experiences of making use of measurements from the first EMEP intensive measurement periods along with EMEP model results from the updated model version to characterise aerosol composition. We investigated how the PM chemical composition varies between the summer and the winter month and geographically. The observation and model data are in general agreement regarding the main features of PM10 and PM2.5 composition and the relative contribution of different components, though the EMEP model tends to give slightly lower estimates of PM10 and PM2.5 compared to measurements. The intensive measurement data has identified areas where improvements are needed. Hourly concurrent measurements of gaseous and particulate components for the first time facilitated testing of modelled diurnal variability of the gas/aerosol partitioning of nitrogen species. In general, the modelled diurnal cycles of nitrate and ammonium aerosols are in fair agreement with the measurements, but the diurnal variability of ammonia is not well captured. The largest differences between model and observations of aerosol mass are seen in Italy during winter, which to a large extent may be explained by an underestimation of residential wood burning sources. It should be noted that both primary and secondary OC has been included in the calculations for the first time, showing promising results. Mineral dust is important, especially in southern Europe, and the model seems to capture the dust episodes well. The lack of measurements of mineral dust hampers the possibility for model evaluation for this highly uncertain PM component. There are also lessons learnt regarding improved measurements for future intensive periods. There is a need for increased comparability between the measurements at different sites. For the nitrogen compounds it is clear that more measurements using artefact free methods based on continuous measurement methods and/or denuders are needed. For EC/OC, a reference methodology (both in field and laboratory) was lacking during these periods giving problems with comparability, though measurement protocols have recently been established and these should be followed by the Parties to the EMEP Protocol. For measurements with no defined protocols, it might be a good solution to use centralised laboratories to ensure comparability across the network. To cope with the introduction of these new measurements, new reporting guidelines have been developed to ensure that all proper information about the methodologies and data quality is given.

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