scholarly journals An Ordinary State-Based Peridynamic Model for Fatigue Cracking of Ferrite and Pearlite Wheel Material

2020 ◽  
Vol 10 (12) ◽  
pp. 4325
Author(s):  
Junzhao Han ◽  
Wenhua Chen
Keyword(s):  
Fatigue Crack Initiation ◽  
Fatigue Cracking ◽  
Relaxation Method ◽  
Static Solution ◽  
Experimental Results ◽  
Model Parameters ◽  
Finite Radius ◽  
Peridynamic Model ◽  
Fatigue Model ◽  
Wheel Material

To deal with a new-developed ferrite and pearlite wheel material named D1, an alternative ordinary state-based peridynamic model for fatigue cracking is introduced due to cyclic loading. The proposed damage model communicates across the microcrack initiation to the macrocrack growth and does not require additional criteria. Model parameters are verified from experimental data. Each bond in the deformed material configuration is built as a fatigue specimen subjected to variable amplitude loading. Fatigue crack initiation and crack growth developed naturally over many loading cycles, which is controlled by the parameter “node damage” within a region of finite radius. Critical damage factors are also imposed to improve efficiency and stability for the fatigue model. Based on the improved adaptive dynamic relaxation method, the static solution is obtained in every loading cycle. Convergence analysis is presented in smooth fatigue specimens at different loading levels. Experimental results show that the proposed peridynamic fatigue model captures the crack sensitive location well without extra criteria and the fatigue life obtained from the simulation has a good correlation with the experimental results.

Holdup and holdup profiles in the reciprocating plate extractor VPE

1990 ◽  
Vol 55 (11) ◽  
pp. 2648-2661 ◽  
Author(s):  
Helena Sovová ◽  
Vladislav Bízek ◽  
Jaroslav Procházka
Keyword(s):  
Steady State ◽  
Experimental Results ◽  
Model Parameters ◽  
Dispersed Phase ◽  
Pulse Form ◽  
Sieve Plates

In this work measurements of mean holdup of dispersed phase, of axial holdup profiles and of flooding points in a reciprocating plate contactor with both the VPE-type plates and the sieve plates were carried out. The experimental results were compared with a monodisperse model of steady-state column hydrodynamics and the model parameters were evaluated. Important differences in the behaviour of the two plate types could be identified. Comparison was also made between two reciprocating drives of different pulse form.

scholarly journals Characterization of Moisture Diffusion in Cured Concrete Slabs at Early Ages

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Xiao Zhang ◽  
Hongduo Zhao
Keyword(s):  
Process Model ◽  
Model Simulation ◽  
Moisture Diffusion ◽  
Experimental Results ◽  
Concrete Slabs ◽  
Model Parameters ◽  
Early Age ◽  
Water Curing ◽  
Early Age Concrete

The objective of this paper is to investigate the characterization of moisture diffusion inside early-age concrete slabs subjected to curing. Time-dependent relative humidity (RH) distributions of three mixture proportions subjected to three different curing methods (i.e., air curing, water curing, and membrane-forming compounds curing) and sealed condition were measured for 28 days. A one-dimensional nonlinear moisture diffusion partial differential equation (PDE) based on Fick’s second law, which incorporates the effect of curing in the Dirichlet boundary condition using a concept of curing factor, is developed to simulate the diffusion process. Model parameters are calibrated by a genetic algorithm (GA). Experimental results show that the RH reducing rate inside concrete under air curing is greater than the rates under membrane-forming compound curing and water curing. It is shown that the effect of water-to-cement (w/c) ratio on self-desiccation is significant. Lower w/c ratio tends to result in larger RH reduction. RH reduction considering both effect of diffusion and self-desiccation in early-age concrete is not sensitive to w/c ratio, but to curing method. Comparison between model simulation and experimental results indicates that the improved model is able to reflect the effect of curing on moisture diffusion in early-age concrete slabs.

scholarly journals Peridynamic model for fatigue cracking.

2014 ◽  
Author(s):  
Stewart Andrew Silling ◽  
Abe Askari
Keyword(s):  
Fatigue Cracking ◽  
Peridynamic Model

Shear strength and yield surface of a partially saturated sandy silt under generalized stress states

2021 ◽  
Author(s):  
Rodrigo Carreira Weber ◽  
Enrique E. Romero Morales ◽  
Antonio Lloret
Keyword(s):  
Shear Strength ◽  
Yield Surface ◽  
Experimental Results ◽  
Model Parameters ◽  
Hollow Cylinder Apparatus ◽  
Clayey Silt ◽  
Lode Angle ◽  
Yield Surfaces ◽  
Stress States ◽  
Deviatoric Stresses

This paper studies the hydromechanical behavior of a slightly compacted mixture of sand and clayey silt (30%/70%) under a generalized stress state. The experimental study focused on analyzing the yielding response and shear strength behavior at different stress states (characterized by the intermediate principal stress parameter b, or Lode angle) and at different initial total suctions (as-compacted state). For the investigation, a hollow cylinder apparatus was used. The shear strength results allowed defining the variation of the critical state line with the Lode angle and the suction. Different models were proposed for isotropic and anisotropic yield surfaces, and their shape and rotation were calibrated with experimental results. The modeled yield surfaces fitted reasonably well the experimental results, considering their inclination and dependence on the suction, mean and deviatoric stresses and Lode angle. In addition, some relationships between the stresses and the model parameters were proposed to normalize the yield surface equation.

Prediction of Fatigue Crack Initiation Life Based on the Extended Cyclic Plasticity Model

2012 ◽  
Author(s):  
Seiichiro Tsutsumi
Keyword(s):  
Cyclic Loading ◽  
Kinematic Hardening ◽  
Fatigue Crack Initiation ◽  
Fatigue Cracking ◽  
Carbon Steels ◽  
Cyclic Plasticity ◽  
Plasticity Model ◽  
Hardening Law ◽  
Crack Initiation Life ◽  
Cyclic Plasticity Model

In order to simulate mechanical fatigue phenomena under macroscopically elastic condition, the plastic stretching within a yield surface has to be described, whilst the plastic strain is induced remarkably as the stress approaches the dominant yielding state. In this study, a phenomenological plasticity model, proposed for the description of the cyclic loading behavior observed for typical carbon steels during the high-cycle fatigue subjected to stresses lower than the yield stress, is applied for the prediction of fatigue initiation life. The model is formulated based on the unconventional plasticity model and is applied for materials obeying isotropic and kinematic hardening law. The mechanical responses under cyclic loading conditions are examined briefly. Finally, the initiation life of fatigue cracking is discussed based on the proposed model with the damage counting parameter.

Thermal Fatigue Testing and Analysis of a Thick Perforated Ring

2007 ◽  
Author(s):  
T. M. Damiani ◽  
J. E. Holliday ◽  
M. J. Zechmeister ◽  
R. D. Reinheimer ◽  
D. P. Jones
Keyword(s):  
Crack Initiation ◽  
Thermal Fatigue ◽  
Fatigue Testing ◽  
Fatigue Crack Initiation ◽  
Three Dimensional ◽  
Fatigue Cracking ◽  
Forced Flow ◽  
Test Loop ◽  
Rapid Changes ◽  
Oxygenated Water

Thermal fatigue cracking has been observed for thick perforated spacer rings used as part of a thermal fatigue test loop operating at Bechtel Bettis, Inc. The perforated rings are used for instrumentation access to the fluid flow at the test specimen inlet and outlet, and are subject to alternating hot and cold forced flow, low oxygenated water every three minutes so that rapid changes in water temperature impart a thermal shock event to the inner wall of the rings. Thermal and structural three dimensional elastic and elastic-plastic finite element analyses (FEA) were conducted for the ring and the results used to predict fatigue crack initiation using strain-based fatigue-life algorithms. Predicted cycles-to-crack initiation agreed well with the observed cracking when alternating shear strain intensity analogous to the Tresca stress was used. This analysis qualifies the use of FEA for thermal fatigue assessments of complicated three-dimensional components.

European Project ATLAS+: Evaluation of a Shear Modified Gurson Model by Comparison to Experimental Fracture Tests on SENT Fracture Specimens

2019 ◽  
Author(s):  
Tobias Bolinder ◽  
Dominique Moinereau ◽  
Patrick Le Delliou ◽  
Anna Dahl ◽  
Jacques Besson
Keyword(s):  
Large Scale ◽  
Stress Triaxiality ◽  
Experimental Results ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Model Parameters ◽  
Coupled Models ◽  
Gurson Model ◽  
Ductile Tearing ◽  
Fracture Tests

Abstract This paper will assess the capability of the shear modified Gurson model developed by Nahshon and Hutchinson which is used by Kiwa Inspecta within the ATLAS+ project. This is done by comparison to experimental results from SENT fracture tests performed by EDF and ARMINES. The procedure for parameter identification for the standard and shear modified Gurson model is also summarized. The work presented in this paper is part of Work Package 3 within the ATLAS+ project. WP3 focus mainly on ductile tearing predictions for large defects in components. Models exists to accurately predict ductile tearing and to consider phenomena such as stress triaxiality effects. These advanced models include local approach coupled models or advanced energetic approaches. However, there is a need to validate these models for use in industrial applications. This will be done within the ATLAS+ project by predicting the results of the large scale component tests where input to the models are given from small size laboratory specimens. Within the paper a description of the shear modified Gurson model is given, as developed by Nashson and Hutchinson [1]. Furthermore, the procedure in determining the material model parameters is discussed. To determine the material parameters for the shear modified Gurson model a uniaxial tensile test, a fracture test and shear tests are used. The material that is used is the ferritic steel WB 36 (15 NiCuMoNb 5) which will be used for the large scale component tests within the ATLAS+ project. The procedure is also evaluated by comparing predictions done with the shear modified Gurson model to experimental results from SENT specimens performed by EDF and ARMINES. A comparison of the capability in predicting the ductile tearing in the SENT experiments between the standard Gurson model and the shear modified Gurson model is also presented within the paper.

FATIGUE TEST OF STEEL GIRDER WEB PENETRATION DETAILS WITH A SLIT

2014 ◽  
Vol 1 (1) ◽  
Author(s):  
Naoto Yoshida ◽  
Masahiro Sakano ◽  
Hideyuki Konishi ◽  
Takashi Fujii
Keyword(s):  
Fatigue Strength ◽  
Fatigue Behavior ◽  
Fatigue Crack Initiation ◽  
Fatigue Cracking ◽  
Highway Bridges ◽  
Strength Properties ◽  
Fatigue Tests ◽  
Bottom Surface ◽  
Steel Girder ◽  
Propagation Behavior

Fatigue cracking in steel girder web penetration details is so dangerous that it can break steel girders. A one-meter-long crack was detected in Yamazoe Bridge in 2006. Since a number of highway bridges with such web penetration details may exist in Japan, it is of urgent importance to understand these fatigue-strength properties. However, few fatigue tests have been reported on steel girder web penetration details. The purpose of this study is to clarify fatigue behavior of steel girder web penetration details with a slit through fatigue tests of specimens with these details. We designed and fabricated girder specimens that have steel girder web penetration details, in which cross-beam bottom flanges are connected to each top or bottom surface of a slit by welding. First, we conducted static loading tests to understand the stress distributions around web penetration details. Second, we conducted fatigue tests to examine fatigue crack initiation and propagation behavior and fatigue strength.

Nanoscale Friction Dynamic Modeling

2009 ◽  
Vol 131 (6) ◽  
Author(s):  
Fakhreddine Landolsi ◽  
Fathi H. Ghorbel ◽  
Jun Lou ◽  
Hao Lu ◽  
Yuekai Sun
Keyword(s):  
Friction Model ◽  
Experimental Results ◽  
Atomic Scale ◽  
Model Parameters ◽  
Large Set ◽  
Asperity Contact ◽  
State Variables ◽  
Stick Slip ◽  
Proposed Model ◽  
Nanoscale Friction

Friction and system models are fundamentally coupled. In fact, the success of models in predicting experimental results depends highly on the modeling of friction. This is true at the atomic scale where the nanoscale friction depends on a large set of parameters. This paper presents a novel nanoscale friction model based on the bristle interpretation of single asperity contact. This interpretation is adopted after a review of dynamic friction models representing stick-slip motion in macrotribology literature. The proposed model uses state variables and introduces a generalized bristle deflection. Jumping mechanisms are implemented in order to take into account the instantaneous jumps observed during 2D stick-slip phenomena. The model is dynamic and Lipchitz, which makes it suitable for future control implementation. Friction force microscope scans of a muscovite mica sample were conducted in order to determine numerical values of the different model parameters. The simulated and experimental results are then compared in order to show the efficacy of the proposed model.

Study of Flow and Thrust in Nozzle-Flapper Valves

1975 ◽  
Vol 97 (1) ◽  
pp. 39-50 ◽  
Author(s):  
S. Hayashi ◽  
T. Matsui ◽  
T. Ito
Keyword(s):  
Approximate Formula ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Relaxation Method ◽  
Experimental Results ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Vena Contracta ◽  
Radial Gap ◽  
Good Agreement

The Navier-Stokes equations and the equation of continuity describing the flow in the flat-faced nozzle-flapper valve are numerically solved by the iterative relaxation method and the effect of the flow contraction (vena contracta) occurring in the radial gap in the valve is investigated. Furthermore, an approximate formula for the flow force acting on the flapper is derived on the basis of the numerical solutions. The formula for the flow force is in good agreement with experimental results.

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