scholarly journals A Comparison of 3D and 2D FE Frictional Heating Models for Long and Variable Applications of Railway Tread Brake

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 4846
Author(s):  
Michal Kuciej ◽  
Piotr Grzes ◽  
Piotr Wasilewski
Keyword(s):  
3D Model ◽  
Frictional Heating ◽  
Fe Model ◽  
Maximum Difference ◽  
Brake Shoe ◽  
Steel Wheel ◽  
Temperature Distributions ◽  
Time Courses ◽  
2D Model

The article proposes two 3D and 2D numerical FE models of frictional heating for the estimation of temperature distributions in railway tread brake in 1xBg configuration during repeated long-term braking. The results of computations were compared with the time courses of temperature measured using thermocouples throughout the duration of the tests on a full-scale dynamometer for two different brake shoe materials in combination with a steel wheel. The resulting temperature distributions calculated using the proposed models agreed well with the experimental measurements, and the maximum difference in temperature values does not exceed 20%. It has been proven that 2D FE model can be as efficient as 3D model to estimate the temperature distribution during long-term and variable braking in the considered friction node. The differences in the calculation of the temperature values using these models did not exceed 3%, and the calculation time for the 2D model, compared to the 3D model, was shorter approximately 85 times for the braking cycle lasting 5032 s, and approximately 45 times for the braking cycle lasting 3297 s.

Design of Metallic Support for Electronic Devices Installed on the Interstage 2/3 of Vega-C Launcher

2019 ◽  
Author(s):  
F. Di Caprio ◽  
D. Cristillo ◽  
G. Giusto ◽  
A. Zallo
Keyword(s):  
Structural Component ◽  
3D Model ◽  
Electronic Devices ◽  
Numerical Procedure ◽  
Structural Performance ◽  
Manufacturing Cost ◽  
Fe Model ◽  
Final Design ◽  
Environmental Requirements ◽  
2D Model

Abstract The purpose of this paper is to provide a numerical procedure developed to obtain the best design (in terms of weight and requirement fulfillment) for a structural component subjected to a launcher environment. The component analyzed represents the support used to mount the SAD/S and DBAT equipment into the VEGA C launcher Interstage 2/3. The final design is obtained by means of an optimization process which aims to satisfy the environmental requirements prescribed by the Vega General Specifications. The developed procedure is based on generation of a fully parametric FE model that is able to switch between ANSYS and NASTRAN software. This routine allows us to execute a topometry optimization with Nastran (by using a 2D model) and to generate a full 3D model (which represents the best compromise among structural performance, manufacturing cost and weight) with Ansys. The final design shows a weight reduction about 50% with respect to the initial provided model.

Evaluation of Numerical Methods to Predict Temperature Distributions of an Experimentally Investigated Convection-Cooled Gas-Turbine Blade

2017 ◽  
Author(s):  
E. Findeisen ◽  
B. Woerz ◽  
M. Wieler ◽  
P. Jeschke ◽  
M. Rabs
Keyword(s):  
Heat Transfer ◽  
Numerical Methods ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Gas Turbines ◽  
Cooling System ◽  
Fe Model ◽  
Gas Turbine Blade ◽  
Transfer Coefficients ◽  
Temperature Distributions

This paper presents two different numerical methods to predict the thermal load of a convection-cooled gas-turbine blade under realistic operating temperature conditions. The subject of the investigation is a gas-turbine rotor blade equipped with an academic convection-cooling system and investigated at a cascade test-rig. It consists of three cooling channels, which are connected outside the blade, so allowing cooling air temperature measurements. Both methods use FE models to obtain the temperature distribution of the solid blade. The difference between these methods lies in the generation of the heat transfer coefficients along the cooling channel walls which serve as a boundary condition for the FE model. One method, referred to as the FEM1D method, uses empirical one-dimensional correlations known from the available literature. The other method, the FEM2D method, uses three-dimensional CFD simulations to obtain two-dimensional heat transfer coefficient distributions. The numerical results are compared to each other as well as to experimental data, so that the benefits and limitations of each method can be shown and validated. Overall, this paper provides an evaluation of the different methods which are used to predict temperature distributions in convection-cooled gas-turbines with regard to accuracy, numerical cost and the limitations of each method. The temperature profiles obtained in all methods generally show good agreement with the experiments. However, the more detailed methods produce more accurate results by causing higher numerical costs.

scholarly journals The significance of Gerta Vrbová's low-frequency stimulation experiment

2021 ◽  
Author(s):  
Dirk Pette
Keyword(s):  
Low Frequency ◽  
Basic Research ◽  
Contractile Properties ◽  
Scientific Cooperation ◽  
Low Frequency Stimulation ◽  
Slow Twitch Muscle ◽  
Frequency Stimulation ◽  
Time Courses ◽  
Fast Twitch

An inspiring scientific cooperation has come to an end, when Gerta Vrbová, an internationally renowned researcher in the field of neuromuscular interactions, passed away on October 2, 2020. Comparative EMG studies had led Gerta to suggest that different contractile properties of fast- and slow-twitch muscle fibers relate to specific firing patterns of their motoneurones. In support of her hypothesis, long term stimulation of fast-twitch muscles with a stimulus pattern resembling that of slow motoneurones, were shown to induce a pronounced fast-to-slow shift in contractile properties. In our cooperation which started in 1970, and also in cooperation with others, Gerta's experiment proved to be an ideal model for the study of neurally controlled changes in phenotype characteristics at various levels of molecular and cellular organization, their time courses and ranges. It has become most important in basic research on the adaptive potential or plasticity of muscle.

scholarly journals Changes in blood hemoglobin and blood gases PaO2 and PaCO2 in severe COPD over a three-year telemonitored program of long-term oxygen treatment

2012 ◽  
Vol 7 ◽  
Author(s):  
Roberto W. Dal Negro ◽  
Silvia Tognella ◽  
Luca Bonadiman ◽  
Paola Turco
Keyword(s):  
Time Course ◽  
Blood Gases ◽  
Wilcoxon Test ◽  
Background Information ◽  
First Year ◽  
Oxygen Treatment ◽  
Blood Hemoglobin ◽  
Time Courses ◽  
Severe Copd

Background: Information on the effects of long-term oxygen treatment (LTOT) on blood hemoglobin (Hb) in severe COPD are limited. The aim was to assess blood Hb values in severe COPD, and investigate the time-course of both Hb and blood gas changes during a 3-year telemetric LTOT. Methods: A cohort of 132 severe COPD patients (94 males; 71.4 years ± 8.8 sd), newly admitted to the tele-LTOT program, was investigated. Subjects were divided according to their original blood Hb: group A: <13 g/dL; group B: ≥13<15 g/dL; group C: ≥ 5<16 g/dL; group D: ≥16 g/dL. Blood Hb (g/dL), PaO2 and PaCO2 (mmHg), SaO2 (%), and BMI were measured at LTOT admission (t0), and at least quarterly over three years (t1-t3). Wilcoxon test was used to compare t0 vs. t1 values; linear regression to assess a possible Hb-BMI relationship; ANOVA to compare changes in Hb time-courses over the 3 years. Results: LTOT induced a systematic increase of PaO2, and changes were significant since the first year (from 52.1 mmHg± 6.6sd to 65.1 mmHg± 8.7 sd, p<0.001). Changes in SaO2 were quite similar. Comparable and equally significant trends were seen in all subgroups (p<0.001). PaCO2 dropped within the first year of LTOT (from 49.4 mmHg± 9.1sd to 45.9 mmHg ±7.5 sd, p<0.001): the t0-t1 comparison proved significant (p<0.01) only in subgroups with the highest basal Hb, who showed a further PaCO2 decline over the remaining two years (p<0.001). Hb tended to normalization during LTOT only in subgroups with basal Hb>15 g/dl (ANOVA p<0.001); anemic subjects (Hb<13 g/dl) ameliorated not significantly in the same period (ANOVA = 0.5). Survival was independent of the original blood Hb. Anemia and polyglobulia are differently prevalent in COPD, the latter being the most represented in our cohort. LTOT affected both conditions, but to a different extent and according to different time-courses. The most striking Hb improvement was in polyglobulic patients in whom also PaO2, PaCO2 and SaO2 dramatically improved. In anemic subjects effects were smaller and slower, oxygenation being equally ameliorated by LTOT. Conclusions: LTOT effects on Hb and PaCO2 are regulated by an Hb-dependent gradient which seems independent of the original impairment of blood gases and of effects on oxygenation.

scholarly journals Mathematical Modelling for Micropiles Embedded in Salt Rock

2016 ◽  
Vol 12 (1) ◽  
pp. 23-35
Author(s):  
Georgiana Rădan (Toader) ◽  
Nicoleta Rădulescu ◽  
Gheorghe Oancea
Keyword(s):  
Mathematical Modelling ◽  
3D Model ◽  
Three Dimensional ◽  
Salt Rock ◽  
In Situ Tests ◽  
Calibration And Validation ◽  
Plaxis 3D ◽  
2D Model ◽  
Computing Models

Abstract This study presents the results of the mathematical modelling for the micropiles foundation of an investement objective located in Slanic, Prahova county. Three computing models were created and analyzed with software, based on Finite Element Method. With Plaxis 2D model was analyzed the isolated micropile and the three-dimensional analysis was made with Plaxis 3D model, for group of micropiles. For the micropiles foundation was used Midas GTS-NX model. The mathematical models were calibrated based with the in-situ tests results for axially loaded micropiles, embedded in salt rock. The paper presents the results obtained with the three software, the calibration and validation models.

scholarly journals Optimized Spacing Of The Longitudinal Reinforcement In CRCP To Avoid Horizontal Cracking

2021 ◽  
Author(s):  
Muhammad Kashif ◽  
Pieter De Winne ◽  
Muhammad Wisal Khattak ◽  
Amelie Outtier ◽  
Hans De Backer
Keyword(s):  
Outer Region ◽  
Maintenance Cost ◽  
Fe Model ◽  
Longitudinal Reinforcement ◽  
Transverse Cracks ◽  
Field Investigations ◽  
Contraction Joints ◽  
Long Term Performance ◽  
Term Performance

Continuously reinforced concrete pavement (CRCP) is characterized by the absence of transverse contraction joints and the presence of longitudinal and transverse reinforcement. The continuous longitudinal reinforcement holds the transverse cracks, caused by the longitudinal shrinkage of concrete, tightly together and thus provides long term performance with minimal maintenance cost. Field investigations on recently constructed CRCP's in Flanders region of Belgium indicated horizontal cracking in the vicinity of the longitudinal reinforcement under the transverse cracks which eventually causes the punch-out distress at the edge of the pavement slab. This paper shows the results of a finite element (FE) study to investigate the effect of varying longitudinal reinforcement on the risk of horizontal cracking in CRCP under typical Flanders conditions. For this purpose, a (3D) FE model of CRCP is developed using a FE package Diana 10.2. The varying longitudinal reinforcement with a most narrow spacing of 125mm in the outer region of the pavement slab is applied while keeping the same CRCP reinforcement ratio. A comparison is made with the conventional longitudinal reinforcement spacing (170mm). Development of concrete stress in the vicinity of the longitudinal reinforcement is plotted against the different longitudinal steel spacing. Findings show that the stress in concrete near longitudinal reinforcement is significantly reduced up to maximum 17% when the narrow spacing is used. In addition, the steel stress in the longitudinal reinforcing is reduced up to maximum 31.75% in the outer region of the pavement slab.

Fetal weight estimation by automated three-dimensional limb volume model in late third trimester compared to two-dimensional model: a cross-sectional prospective observational study

2021 ◽  
Author(s):  
Xining Wu ◽  
Zihan Niu ◽  
Zhonghui Xu ◽  
Yuxin Jiang ◽  
Yixiu Zhang ◽  
...  
Keyword(s):  
Birth Weight ◽  
3D Model ◽  
Three Dimensional ◽  
Fetal Weight ◽  
Percentage Error ◽  
Limb Volume ◽  
Third Trimester ◽  
Volume Model ◽  
Estimated Error ◽  
2D Model

Abstract Background: Accurate estimation of fetal weight is important for prenatal care and for detection of fetal growth abnormalities. Prediction of fetal weight entails the indirect measurement of fetal biometry by ultrasound that is then introduced into formulae to calculate the estimated fetal weight. The aim of our study was to evaluate the accuracy of the automated three-dimensional(3D) fractional limb volume model to predict fetal weight in the third trimester.Methods: Prospective 2D and 3D ultrasonography were performed among women with singleton pregnancies 7 days before delivery to obtain 2D data, including fetal biparietal diameter, abdominal circumference and femur length, as well as 3D data, including the fractional arm volume (AVol) and fractional thigh volume (TVol). The fetal weight was estimated using the 2D model and the 3D fractional limb volume model respectively. Percentage error = (estimated fetal weight - actual birth weight) ÷ actual birth weight × 100. Systematic errors (accuracy) were evaluated as the mean percentage error (MPE). Random errors (precision) were calculated as±1 SD of percentage error.Results: Ultrasound examination was performed on 56 fetuses at 39.6 ± 1.4 weeks gestation. The average birth weight of the newborns was 3393 ± 530 g. The average fetal weight estimated by the 2D model was 3478 ± 467 g, and the MPE was 3.2 ± 8.9. The average fetal weights estimated by AVol and TVol of the 3D model were 3268 ± 467 g and 3250 ± 485 g, respectively, and the MPEs were -3.3 ± 6.6 and -3.9 ± 6.1, respectively. For the 3D TVol model, the proportion of fetuses with estimated error ≤ 5% was significantly higher than that of the 2D model (55.4% vs. 33.9%, p < 0.05). For fetuses with a birth weight < 3500 g, the accuracy of the AVol and TVol models were better than the 2D model (-0.8 vs. 7.0 and -2.8 vs. 7.0, both p < 0.05). Moreover, for these fetus, the proportions of estimated error ≤ 5% of the AVol and TVol models were 58.1% and 64.5%, respectively, significantly higher than that of the 2D model (19.4%) (both p < 0.05). The consistency of different examiners measuring fetal AVol and TVol were satisfactory,with the intraclass correlation coefficients of 0.921 and 0.963, respectively.Conclusion: In this cohort,the automated 3D fractional limb volume model improves the accuracy of weight estimation in most third-trimester fetuses. In particular, the 3D model estimation accuracy for fetuses with weight < 3500 g is significantly higher than that of the traditional 2D model.

Remembering Over the Short and Long Term

2020 ◽  
pp. 282-310
Author(s):  
Patricia A. Reuter-Lorenz ◽  
Alexandru D. Iordan
Keyword(s):  
Working Memory ◽  
Cognitive Neuroscience ◽  
Semantic Processing ◽  
Long Term Memory ◽  
Strategic Processing ◽  
Term Memory ◽  
Neuroscience Research ◽  
Short And Long Term ◽  
Time Courses

This chapter reviews evidence from behavioural and cognitive neuroscience research that supports a unitary view of memory whereby working memory and long-term memory phenomena arise from representations and processes that are largely shared when remembering over the short or long term. Using ‘false working memories’ as a case study, it highlights several paradoxes that cannot be explained by a multisystem view of memory in which working memory and long-term memory are structurally distinct. Instead, it is posited that behavioural memory effects over the short and long term relating to semantic processing, modality/domain-specificity, dual-task interference, strategic processing, and so on arise from the differences in activational states and availability of different representational features (e.g. sensory/perceptual, associative, action-based) that vary in their time courses and activity, attentional priority, and susceptibility to interference. Cognitive neuroscience evidence primarily from brain imaging methodologies that support this view is reviewed.

Thermo-mechanical analysis of train wheel-rail contact using a novel finite-element model

2020 ◽  
Vol 72 (5) ◽  
pp. 687-693
Author(s):  
Liuqing Yang ◽  
Ming Hu ◽  
Deming Zhao ◽  
Jing Yang ◽  
Xun Zhou
Keyword(s):  
Finite Element ◽  
Peer Review ◽  
Frictional Heating ◽  
Element Model ◽  
Mechanical Analysis ◽  
Partial Slip ◽  
Computational Time ◽  
Fe Model ◽  
Content Type ◽  
Explicit Finite Element

Purpose The purpose of this paper is to develop a novel method for analyzing wheel-rail (W-R) contact using thermo-mechanical measurements and study the effects of heating on the characteristics of W-R contact under different creepages. Design/methodology/approach This study developed an implicit-explicit finite element (FE) model which could solve both partial slip and full sliding problems by setting different angular velocities on the wheels. Based on the model, four material types under six different creepages were simulated. Findings The results showed that frictional heating significantly affected the residual stress distribution under large creepage conditions. As creepage increased, the temperature of the wheel tread and rail head rose and the peak value was located at the trailing edge of the contact patch. Originality/value The proposed FE model could reduce computational time and thus cost to about one-third of the amount commonly found in previous literature. Compared to other studies, these results are in good agreement and offer a reasonable alternative method for analyzing W-R contact under various conditions. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2019-0298

scholarly journals Evaluation of Strain Transition Properties between Cast-In Fibre Bragg Gratings and Cast Aluminium during Uniaxial Straining

Sensors ◽  
2020 ◽  
Vol 20 (21) ◽  
pp. 6276
Author(s):  
Florian Heilmeier ◽  
Robert Koos ◽  
Michael Singer ◽  
Constantin Bauer ◽  
Peter Hornberger ◽  
...  
Keyword(s):  
Bragg Gratings ◽  
Tensile Specimen ◽  
Strain Sensors ◽  
Fe Model ◽  
Plastic Strains ◽  
Closing The Gap ◽  
Optical Strain ◽  
Structural Parts ◽  
Fibre Bragg Gratings

Current testing methods are capable of measuring strain near the surface on structural parts, for example by using strain gauges. However, stress peaks often occur within the material and can only be approximated. An alternative strain measurement incorporates fibre-optical strain sensors (Fiber Bragg Gratings, FBG) which are able to determine strains within the material. The principle has already been verified by using embedded FBGs in tensile specimens. The transition area between fibre and aluminium, however, is not yet properly investigated. Therefore, strains in tensile specimens containing FBGs were measured by neutron diffraction in gauge volumes of two different sizes around the Bragg grating. As a result, it is possible to identify and decouple elastic and plastic strains affecting the FBGs and to transfer the findings into a fully descriptive FE-model of the strain transition area.We thus accomplished closing the gap between the external load and internal straining obtained from cast-in FBG and generating valuable information about the mechanisms within the strain transition area.It was found that the porosity within the casting has a significant impact on the stiffness of the tensile specimen, the generation of excess microscopic tensions and thus the formation of permanent plastic strains, which are well recognized by the FBG. The knowledge that FBG as internal strain sensors function just as well as common external strain sensors will now allow for the application of FBG in actual structural parts and measurements under real load conditions. In the future, applications for long-term monitoring of cast parts will also be enabled and are currently under development.

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