Three-dimensional numerical simulation of the nitriding process

2004 ◽  
Vol 120 ◽  
pp. 777-783
Author(s):  
P. Duranton ◽  
J. Devaux ◽  
M. Larreur ◽  
R. Fortunier ◽  
J.-M. Bergheau
Keyword(s):  
Numerical Simulation ◽  
Volume Expansion ◽  
Gear Tooth ◽  
Three Dimensional ◽  
Mechanical Analysis ◽  
Nitriding Process ◽  
Chromium Nitride ◽  
Elastic Behaviour ◽  
Volume Changes ◽  
Precipitation Analysis

This paper presents a three-dimensional numerical simulation of a nitriding process applied to an industrial component. The aim of the simulation is to predict the residual stresses and distortions due to volume changes induced by chromium nitride (CrN) and carbides (M23C6 et M4C3) formation. The simulation is performed in two steps. The diffusion of nitrogen and the precipitation of chrome nitride and carbides are first simulated. Then stresses and strains are calculated, assuming an elastic behaviour of the component, and using a volume expansion due to the precipitate concentration. The proposed approach is applied on a gear tooth. Small holes and details were neglected. For symmetry reasons, only half a tooth is taken into account. As the main phenomena take place through the first millimetre from the outer surface, a special attention was paid on meshing. The mesh used for the diffusion and precipitation analysis is composed of 1 130 000 nodes and 1 110 000 elements. For the mechanical analysis, a coarser mesh including only 165 000 nodes and 290 000 elements was used.

Quantifying the volume increase and chemical exchange during serpentinization

Geology ◽  
2020 ◽  
Vol 48 (6) ◽  
pp. 552-556 ◽  
Author(s):  
Frieder Klein ◽  
Véronique Le Roux
Keyword(s):  
Volume Expansion ◽  
Laboratory Experiments ◽  
Chemical Exchange ◽  
Three Dimensional ◽  
Fluid Composition ◽  
Volume Changes ◽  
Volume Increase ◽  
Increasing Process ◽  
Static Conditions ◽  
Measured Volume

Abstract Quantifying the concurrent changes in rock volume and fluid composition during serpentinization remains a major challenge in assessing its physicochemical effects during continental rifting, seafloor spreading, and subduction. Here we conducted a series of 11 hydrothermal laboratory experiments where cylindrical cores of natural dunite, harzburgite, and pyroxenite were reacted with an aqueous solution at 300 °C and 35 MPa for up to 18 months. Using three-dimensional microcomputed tomography and thermogravimetry, we show that rock volume systematically increased with time and extent of reaction, leading to a volume increase of 44% (±8%) in altered rock domains after 10–18 months of serpentinization. The volume expansion was accompanied by Mg-Ca exchange between fluid and rock, while Fe and Si were largely conserved. We find that the protolith composition (olivine/orthopyroxene ratio) plays a significant role in controlling the fluid chemistry and the proportions of hydrous secondary minerals during serpentinization. Agreement between alteration mineralogy, composition of reacting fluids, and measured volume changes suggests that serpentinization under static conditions is a volume-increasing process in spite of demonstrable mass transfer. Volume expansion implies an increased water carrying capacity and buoyancy force of serpentinite per unit mass of protolith, while Mg-Ca exchange during serpentinization may affect the Mg/Ca ratio of seawater on Earth and possibly other ocean worlds.

scholarly journals Numerical simulation of degradation of porous building materials caused by freeze-thaw cycles

2019 ◽  
Vol 282 ◽  
pp. 02090
Author(s):  
Jiří Maděra ◽  
Jaroslav Kruis
Keyword(s):  
Numerical Simulation ◽  
Building Materials ◽  
Damage Model ◽  
Mechanical Analysis ◽  
Structural Elements ◽  
Volume Changes ◽  
Porous Building Materials ◽  
Freeze Thaw ◽  
Numerical Example ◽  
Isotropic Damage

Freeze-thaw cycles in porous building materials are studied in this contribution. Degradation and durability of many building materials as well as structural elements are tightly connected with the freeze-thaw cycles. The porosimetry curve and Gibbs-Thomson equation are used for estimates of volume changes caused by the freeze-thaw cycles. The volume changes are used in mechanical analysis based on the isotropic damage model. Numerical example documents the approach proposed.

Three-dimensional numerical simulation of air flow and fiber dynamic in carding region in carding machine

2019 ◽  
Vol 89 (19-20) ◽  
pp. 3916-3926
Author(s):  
Shanshan He ◽  
Longdi Cheng ◽  
Wenliang Xue ◽  
Zhong Lu ◽  
Liguo Chen
Keyword(s):  
Mechanical Properties ◽  
Numerical Simulation ◽  
Finite Element ◽  
Flow Field ◽  
Axial Velocity ◽  
Three Dimensional ◽  
Tangential Velocity ◽  
Element Model ◽  
Mechanical Analysis ◽  
Field Simulation

Regular cylinder metallic card clothing has a limited carding efficiency. As a result of the limited dimensions, any measurement between the cylinder and flat area is difficult to make. In this study, an approach is first proposed to simulate the flow field and a fiber finite-element model on the moving surface of the teeth and produce a new design of misaligned-teeth card clothing, with the aim of improving the carding efficiency. A comparison is made between regular and misaligned-teeth card clothing types with respect to flow field simulation and fiber mechanical properties. The results show that the force resulting from the tangential velocity between the cylinder and flat is as great as 1.86 × 10−3 N, sufficient to pull fiber out of tufts, and that the tangential velocity (from 3880 to 2500 mm/s) plays a major role in this area, as opposed to the axial velocity (from 0 to 190 mm/s). Through this comparison, the misalignment design can result in a different tangential velocity distribution from that of traditional card clothing, which helps fibers between two lines of teeth move into neighboring lines of teeth, thereby increasing the likelihood that fibers will be carded. For fiber mechanical analysis, different air forces are loaded on fibers. This comparison shows that for fibers in the channel, the misalignment can help fibers move toward the teeth. Therefore, this misaligned-teeth card clothing is thought to prove more effective in practice.

Numerical Analysis of Thermal Stratification in Pressurizer Surge Line

2010 ◽  
Author(s):  
Zhanfei Qi ◽  
Xuewu Cao
Keyword(s):  
Numerical Simulation ◽  
Thermal Stratification ◽  
Three Dimensional ◽  
Simulation Method ◽  
Mechanical Analysis ◽  
Piping System ◽  
Original Design ◽  
Pressurized Water ◽  
Surge Line ◽  
The Impact

The thermal stratification is generic to un-isolable piping system in pressurized water reactor (PWR), which is not considered in original design. This effect can finally threaten the integrity of the piping system. The pressurizer surge line is affected by thermal stratification during reactor heat up and shutdown processes particularly. It’s important to investigate and mitigate thermal stratification in the surge line to meet safety requirements. In this paper, the thermal hydraulic analysis and the mechanical analysis using numerical simulation method were conducted to evaluate the impact of thermal stratification in the surge line during reactor heat up processes. The results give the three-dimensional temperature distribution and stress status of the surge line. It indicates that thermal stratification can cause stress concentration in the displacement restricts. The mitigation of thermal stratification was also studied. The numerical simulation of pressurizer surge line can put forward thermal stratification analysis.

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