scholarly journals Distortion-Induced Fatigue Reassessment of a Welded Bridge Detail Based on Structural Stress Methods

Metals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1952
Author(s):  
Vencislau Quissanga ◽  
Guilherme Alencar ◽  
Abílio de Jesus ◽  
Rui Calçada ◽  
José da Silva
Keyword(s):  
Hot Spot ◽  
High Stress ◽  
The Finite Element Method ◽  
Random Loads ◽  
Significant Damage ◽  
Curve Method ◽  
Structural Stresses ◽  
The Difference ◽  
Global And Local ◽  
Near Future

Typically, bridge structural systems are affected by random loads that can cause significant damage. One challenging problem in this field is the high-stress amplitude associated with distortion-induced fatigue. In this study, the hot-spot method and the master S-N curve method were validated for the evaluation of fatigue resistance induced by distortion in welded joints of steel bridges. Validation of the master S-N curve method in this research was a necessary prior step for application of the method in real case studies of road bridges, which will be subject to loads of variable amplitudes in the near future, ensuring the basis for the application. The method of validation was based on an important available full-scale fatigue test database, which was generated decades ago to serve as the foundation for the assessment of distortion-induced fatigue. Modelling was carried out based on the finite element method with the aid of ANSYS software, considering the shell and solid elements and equivalent structural stresses. The experimental results were compared with the numerical ones obtained with the two methodologies, and the difference, in terms of global and local tension, was less than 1%.

scholarly journals Fatigue Resistance and Failure Behavior of Penetration and Non-Penetration Laser Welded Lap Joints

2021 ◽  
Vol 34 (1) ◽  
Author(s):  
Xiangzhong Guo ◽  
Wei Liu ◽  
Xiqing Li ◽  
Haowen Shi ◽  
Zhikun Song
Keyword(s):  
Fatigue Resistance ◽  
Failure Modes ◽  
Plate Thickness ◽  
High Stress ◽  
Lap Joints ◽  
Failure Behavior ◽  
Passenger Cars ◽  
Plate Fracture ◽  
The Difference ◽  
Railway Passenger

AbstractPenetration and non-penetration lap laser welding is the joining method for assembling side facade panels of railway passenger cars, while their fatigue performances and the difference between them are not completely understood. In this study, the fatigue resistance and failure behavior of penetration 1.5+0.8-P and non-penetration 0.8+1.5-N laser welded lap joints prepared with 0.8 mm and 1.5 mm cold-rolled 301L plates were investigated. The weld beads showed a solidification microstructure of primary ferrite with good thermal cracking resistance, and their hardness was lower than that of the plates. The 1.5+0.8-P joint exhibited better fatigue resistance to low stress amplitudes, whereas the 0.8+1.5-N joint showed greater resistance to high stress amplitudes. The failure modes of 0.8+1.5-N and 1.5+0.8-P joints were 1.5 mm and 0.8 mm lower lap plate fracture, respectively, and the primary cracks were initiated at welding fusion lines on the lap surface. There were long plastic ribs on the penetration plate fracture, but not on the non-penetration plate fracture. The fatigue resistance stresses in the crack initiation area of the penetration and non-penetration plates calculated based on the mean fatigue limits are 408 MPa and 326 MPa, respectively, which can be used as reference stress for the fatigue design of the laser welded structures. The main reason for the difference in fatigue performance between the two laser welded joints was that the asymmetrical heating in the non-penetration plate thickness resulted in higher residual stress near the welding fusion line.

scholarly journals Effect of load sequence interaction on bond-wire lifetime due to power cycling

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Zoubir Khatir ◽  
Son-Ha Tran ◽  
Ali Ibrahim ◽  
Richard Lallemand ◽  
Nicolas Degrenne
Keyword(s):  
High Stress ◽  
Bipolar Transistors ◽  
Junction Temperature ◽  
Experimental Investigations ◽  
Power Cycling ◽  
Power Modules ◽  
Bond Wire ◽  
Load Sequence ◽  
The Difference ◽  
Heating Duration

AbstractExperimental investigations on the effects of load sequence on degradations of bond-wire contacts of Insulated Gate Bipolar Transistors power modules are reported in this paper. Both the junction temperature swing ($$\Delta T_{j}$$ Δ T j ) and the heating duration ($$t_{ON}$$ t ON ) are investigated. First, power cycling tests with single conditions (in $$\Delta T_{j}$$ Δ T j and $$t_{ON}$$ t ON ), are performed in order to serve as test references. Then, combined power cycling tests with two-level stress conditions have been done sequentially. These tests are carried-out in the two sequences: low stress/high stress (LH) and high stress/low stress (HL) for both $$\Delta T_{j}$$ Δ T j and $$t_{ON}$$ t ON . The tests conducted show that a sequencing in $$\Delta T_{j}$$ Δ T j regardless of the direction “high-low” or “low–high” leads to an acceleration of degradations and so, to shorter lifetimes. This is more pronounced when the difference between the stress levels is large. With regard to the heating duration ($$t_{ON}$$ t ON ), the effect seems insignificant. However, it is necessary to confirm the effect of this last parameter by additional tests.

Optimal control strategies for the surface hardening of steel

2004 ◽  
Vol 120 ◽  
pp. 325-335
Author(s):  
D. Hömberg ◽  
S. Volkwein ◽  
W. Weiss
Keyword(s):  
Optimal Control ◽  
Surface Hardening ◽  
Control Strategies ◽  
Hot Spot ◽  
Orthogonal Decomposition ◽  
Phase Volume ◽  
The Finite Element Method ◽  
Optimal Temperature ◽  
Real Process ◽  
Proper Orthogonal

We discuss control strategies for the surface hardening of steel with laser or electron beam. The goal is to acchieve a prescribed hardening depth avoiding surface melting. Our mathematical model consists of a system of ODEs for the phase volume fractions coupled with the heat equation. The system is solved semi-implicitely using the finite element method. For the optimal control we discuss two approaches: model reduction using POD (Proper Orthogonal Decomposition) and a feedback control of temperature. The numerical results prove that it is not sufficient to control the surface temperature in order to obtain a uniform hardening depth. Instead the best strategy should be to compute the optimal temperature in the hot spot of the beam by solving the control problem and use this temperature as the set-point for the pyrometer control of the real process.

scholarly journals Air versus water temperature of aquatic habitats in Delhi: Implications for transmission dynamics of Aedes aegypti

2018 ◽  
Vol 13 (2) ◽  
Author(s):  
Gaurav Kumar ◽  
Veena Pande ◽  
Shweta Pasi ◽  
Vijay P. Ojha ◽  
Ramesh C. Dhiman
Keyword(s):  
Water Temperature ◽  
Air Temperature ◽  
Data Loggers ◽  
Breeding Habitats ◽  
Significant Difference ◽  
The Difference ◽  
Near Future ◽  
Plastic Containers ◽  
Local Weather ◽  
Container Material

The present study was planned to characterize the microclimate experienced by Aedes larvae in different breeding habitats by determining the temperature variations in water kept in containers during different months under natural conditions. The study was conducted in three municipal zones of Delhi. In each site, four types of container material (plastic, cement, iron and ceramic) were chosen for recording the water temperature in the containers. Daily air and water temperatures (mean, maximum and minimum values) recorded by HOBO and Tidbit data loggers, respectively, were compared using analysis of variance and Tukey’s honest significant difference (HSD) tests. Mean monthly temperature of water varied from 16.9 to 33.0 °C in tin containers, 17.3 to 35.6°C in plastic containers, 14.3 to 28.5°C in ceramic pots, 23.3 to 30.4°C in cemented underground tanks (UGT) and 15.8 to 35.1°C in cemented overhead tanks (OHTs). Corresponding values for the air temperature ranged from 17.7 to 36.1°C. The difference between temperature of water in the containers and air temperature was highest for ceramic pots. Daily mean, maximum and minimum temperatures recorded by different data loggers differed significantly (P<0.05). When Tukey HSD test was applied for data analysis, the daily mean air temperature differed significantly from the water temperature in tin and ceramic pots as well as cemented OHTs. The temperature of water in the different breeding habitats investigated was lower than the air temperature. Moreover, actual air temperature as recorded by HOBO was higher than the temperature recorded by local weather stations. Considering the ongoing climate change, cemented UGT and earthen pots may be more productive breeding habitats for the Aedes mosquito in the near future, while plastic and cemented OHTs might no longer be suitable for Aedes breeding.

Study and Simulate the Air Pollution Based on the Finite Difference Method

2012 ◽  
Vol 518-523 ◽  
pp. 2820-2824
Author(s):  
Yi Ni Guo ◽  
Yan Zhang ◽  
Jian Wang ◽  
Ye Huang
Keyword(s):  
Finite Element Method ◽  
Air Pollution ◽  
Finite Difference ◽  
Finite Difference Method ◽  
Difference Method ◽  
The Finite Element Method ◽  
Liquid Diffusion ◽  
Continuous Problems ◽  
The Finite Difference Method ◽  
The Difference

The finite difference method that is the finite element method is used to solve the plane continuous problems. In this article, the theory and method of the finite difference method, as well as the application on the boundary problem are introduced. By analyzing the potential flew field equation and liquid diffusion equation, they are discreted using the difference method and the numerical analysis under certain boundary condition is conducted. In air pollution, the smoke in the diffusion is typical planar continuous problems. In this paper, the finite difference method is used to analyse and simulate the spread of the smoke.

scholarly journals Is stress an important co morbid factor for hypertension among legal professionals

2018 ◽  
Vol 5 (5) ◽  
pp. 1899
Author(s):  
L. Kannan ◽  
Praveena P.
Keyword(s):  
High Stress ◽  
Simple Random Sampling ◽  
Well Being ◽  
Cross Sectional Study ◽  
District Court ◽  
Cross Sectional ◽  
Legal Professionals ◽  
The Difference ◽  
The Right ◽  
Study Participants

Background: Stress is a mental, physical and emotional response to life demands. Long hours of work, client demands, changing laws- creates stress and eventually hypertension among advocates. Well-being of the advocates are being questioned. Hence the main objective of the study is to evaluate the relationship between stress and hypertension among practising advocates.Methods: A cross-sectional study was conducted in a sample of 300 practising advocates at Madurai district court for a period of 1 year by simple random sampling method.Results: Around 133 (44.33%) and 167 (55.66%) of study participants were in level of high stress and low stress respectively. Among high stressed participants, a majority of 113 (84.96%) were found to be hypertensives and among the low stressed participants only 10 (5.98%) were hypertensives. The difference of observation was found to be statistically significant (p=0.0000).Conclusions: In conclusion the study explains that practising advocates with high perceived stress 113 (84.96%) were found to be hypertensives. Stress has a significant association with hypertension. The right way to manage stress is to implement coping strategies.

scholarly journals The Search of Spatial Functions of Pressure in Adjustable Hydrostaticradial Bearing

2015 ◽  
Vol 9 (1) ◽  
pp. 23-26 ◽  
Author(s):  
Dmytro Fedorynenko ◽  
Sergiy Boyko ◽  
Serhii Sapon
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Elastic Deformation ◽  
Tangential Direction ◽  
The Finite Element Method ◽  
Radial Bearing ◽  
Operational Characteristics ◽  
Service Conditions ◽  
The Difference ◽  
Element Method

Abstract The analysis of spatial functions of pressure considering the geometrical deviations and the elastic deformation of conjugate surace have been considered. The analysis of spatial functions of pressure is performed by the finite element method. The difference of the size of pressure in a tangential direction of a pocket of a support under various service conditions has been investigated. A recommendation for improving of operational characteristics in regulated hydrostatic radial bearing has been developed.

scholarly journals A study on small-world characteristics of Chinaäó»s high-speed railway networks

2016 ◽  
Author(s):  
Xin Yuan ◽  
Guo Liu ◽  
Kun Hui Ye
Keyword(s):  
High Speed ◽  
Small World ◽  
Clustering Coefficient ◽  
High Speed Rail ◽  
Attribute Data ◽  
The Social ◽  
The Difference ◽  
Global And Local ◽  
The Relationship ◽  
Space Method

The small-world model provides a useful perspective and method to study the topological structure and intrinsic characteristics of high-speed rail networks (HRNs). In this paper, the P-space method is used to examine global and local HRNs in China, meanwhile the adjacency matrix is developed, then the social network analysis and visualization tool UCINET is used to calculate the spatial and attribute data of HRNs at national and local levels in China. The small-world characteristics of whole HRNs are discussed, three networks which have different properties are determined, and a comparative analysis of the small-world effect is detected. Then, the relationship between the construction of high-speed rail and regional development of China is analysed. The results show that: 1) China's HRNs have small average path length ( L ) and large clustering coefficient (C ), representing a typical small-world network; 2) Local HRNs have a certain correlation with economic development. The reasons for the difference of HRNs with respect to characteristics among regions are eventually discussed.

scholarly journals Elastic electron scattering from 17Ne and 27P exotic nuclei

2019 ◽  
Vol 13 (28) ◽  
pp. 68-81
Author(s):  
A. R. Ridha
Keyword(s):  
Electron Scattering ◽  
Form Factors ◽  
Computer Code ◽  
Exotic Nuclei ◽  
Proton Density ◽  
Elastic Electron ◽  
Elastic Electron Scattering ◽  
The Difference ◽  
Proton Form Factors ◽  
Near Future

The ground state proton, neutron and matter densities andcorresponding root mean square radii of unstable proton-rich 17Neand 27P exotic nuclei are studied via the framework of the twofrequencyshell model. The single particle harmonic oscillator wavefunctions are used in this model with two different oscillator sizeparameters core b and halo , b the former for the core (inner) orbitswhereas the latter for the halo (outer) orbits. Shell model calculationsfor core nucleons and for outer (halo) nucleons in exotic nuclei areperformed individually via the computer code OXBASH. Halostructure of 17Ne and 27P nuclei is confirmed. It is found that thestructure of 17Ne and 27P nuclei have 25 / 2 (1d ) and 1/ 2 2s -dominantconfigurations, respectively. Elastic electron scattering form factorsof these exotic nuclei are also studied using the plane wave Bornapproximation. Effects of the long tail behavior of the proton densitydistribution on the proton form factors of 17Ne and 27P areanalyzed. It is found that the difference between the proton formfactor of 17Ne and that of stable 20Ne (or of 27P and that of stable31P) comes from the difference in the proton density distribution ofthe last two protons (or of the last proton) in the two nuclei. It isconcluded that elastic electron scattering will be an efficient tool (inthe near future) to examine proton-halo phenomena of proton-richnuclei.

scholarly journals Multi-scale Method for the Crack Problem in Microstructural Materials

2010 ◽  
Vol 10 (1) ◽  
pp. 69-86 ◽  
Author(s):  
R. H. W. Hoppe ◽  
S.I. Petrova
Keyword(s):  
Finite Element ◽  
Crack Problem ◽  
Material Model ◽  
Superposition Method ◽  
The Finite Element Method ◽  
Multi Scale ◽  
Microscopic Models ◽  
Modeling Strategy ◽  
Porous Microstructures ◽  
Global And Local

AbstractThe paper deals with the numerical computation of a crack problem posed on microstructural heterogeneous materials containing multiple phases in the microstructure. The failure of such materials is a natural multi-scale effect since cracks typically nucleate in regions of defects on the microscopic scale. The modeling strategy for solving the crack problem concerns simultaneously the macroscopic and microscopic models. Our approach is based on an efficient combination of the homogenization technique and the mesh superposition method (s-version of the finite element method). The homogenized model relies on a double-scale asymptotic expansion of the displacement field. The mesh superposition method uses two independent (global and local) finite element meshes and the concept of superposing the local mesh arbitrarily on the global continuous mesh. The crack is treated by the local mesh and the homogenized material model is considered on the global mesh. Numerical experiments for problems on biomorphic microcellular ceramic templates with porous microstructures of different materials constituents are presented.

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