On the selection of the most plausible non-linear axial stress–strain model for railway ballast under different impulse magnitudes

2021 ◽  
pp. 147592172110339
Author(s):  
Mujib Olamide Adeagbo ◽  
Heung-Fai Lam ◽  
Qin Hu
Keyword(s):  
Small Amplitude ◽  
Model Updating ◽  
Axial Stress ◽  
Elastic Model ◽  
Stress Strain ◽  
Elasticity Limit ◽  
Non Linear ◽  
Model Class ◽  
Strain Model ◽  
Selection Of

The effective maintenance and health monitoring of ballasted railway tracks, which involves the determination of differential settlement, track support stress and stiffness, and the strain-hardening property of ballast, is essential. The vertical stress–strain behavior of the ballast layer is primarily responsible for the irrecoverable strains and settlements in tracks, leading to further track degradation. This article reports the development of a series of applicable yet simple uniaxial models and the selection of the most plausible one for capturing the behavior of vertical stresses and strains in ballasts utilizing a set of measured vibration data of the rail–sleeper–ballast system from a Bayesian perspective. From the literature, the dynamic behavior of ballast can be divided into linear and non-linear regions. Under small amplitude vibration, the stress–strain property is linear and elastic, while the behavior becomes non-linear and inelastic once the elasticity limit is exceeded. By integrating the linear phase to some well-known non-linear engineering material laws, a list of new ballast stress–strain model classes was developed. An enhanced Markov chain Monte Carlo–based Bayesian scheme was utilized to explicitly handle the uncertainties in the model updating process, while the Bayesian model class selection method was employed to select the most plausible ballast stress–strain model class under the prevailing system conditions. The proposed methodology was verified using three sets of measured acceleration data from impact hammer tests on an in situ sleeper with simulated ballast damage. The obtained results suggest that the linear-elastic model is sufficient for small amplitude vibrations, while the modified Voce model is the most plausible amongst the investigated model classes for high impact load. The results also demonstrate the importance of the non-linear ballast model in ballast damage identification and the potential applicability of the selected ballast model in field track monitoring.

A Two-Dimensional Linear Assumed Strain Triangular Element for Finite Deformation Analysis

2005 ◽  
Vol 73 (6) ◽  
pp. 970-976 ◽  
Author(s):  
Fernando G. Flores
Keyword(s):  
Finite Deformation ◽  
Degrees Of Freedom ◽  
Yield Function ◽  
Triangular Element ◽  
Deformation Analysis ◽  
Elastic Model ◽  
Stress Strain ◽  
Metric Tensor ◽  
Assumed Strain ◽  
Non Linear

An assumed strain approach for a linear triangular element able to handle finite deformation problems is presented in this paper. The element is based on a total Lagrangian formulation and its geometry is defined by three nodes with only translational degrees of freedom. The strains are computed from the metric tensor, which is interpolated linearly from the values obtained at the mid-side points of the element. The evaluation of the gradient at each side of the triangle is made resorting to the geometry of the adjacent elements, leading to a four element patch. The approach is then nonconforming, nevertheless the element passes the patch test. To deal with plasticity at finite deformations a logarithmic stress-strain pair is used where an additive decomposition of elastic and plastic strains is adopted. A hyper-elastic model for the elastic linear stress-strain relation and an isotropic quadratic yield function (Mises) for the plastic part are considered. The element has been implemented in two finite element codes: an implicit static/dynamic program for moderately non-linear problems and an explicit dynamic code for problems with strong nonlinearities. Several examples are shown to assess the behavior of the present element in linear plane stress states and non-linear plane strain states as well as in axi-symmetric problems.

Algorithms for Bayesian Model Class Selection of Higher-Dimensional Dynamic Systems

2007 ◽  
Author(s):  
Sai Hung Cheung ◽  
James L. Beck
Keyword(s):  
Bayesian Model ◽  
Model Updating ◽  
Structural Dynamic ◽  
Higher Dimensional ◽  
Significant Probability ◽  
Model Class ◽  
Updating Procedure ◽  
Model Class Selection ◽  
Dimensional Integral ◽  
Selection Of

In recent years, Bayesian model updating techniques based on measured data have been applied in structural health monitoring. Often we are faced with the problem of how to select the ‘best’ model from a set of competing candidate model classes for the system based on data. To tackle this problem, Bayesian model class selection is used, which provides a rigorous Bayesian updating procedure to give the probability of different candidate classes for a system, based on the data from the system. There may be cases where more than one model class has significant probability and each of these will give different predictions. Bayesian model class averaging provides a coherent mechanism to incorporate all the considered model classes in the probabilistic predictions for the system. However, both Bayesian model class selection and Bayesian model class averaging require the calculation of the evidence of the model class which requires the nontrivial computation of a multi-dimensional integral. In this paper, several methods for solving this computationally challenging problem of model class selection are presented, proposed and compared. The efficiency of the proposed methods is illustrated by an example involving a structural dynamic system.

scholarly journals A MULTI-AXIAL STRESS-STRAIN MODEL FOR STRUCTURAL ALUMINUM ALLOYS UNDER CYCLIC LOADS

2002 ◽  
Vol 67 (558) ◽  
pp. 227-232 ◽  
Author(s):  
Tadao NAKAGOMI ◽  
Tomohisa YAMADA ◽  
Yuichi ICHIKAWA ◽  
Atsushi SUGIE
Keyword(s):  
Aluminum Alloys ◽  
Axial Stress ◽  
Cyclic Loads ◽  
Stress Strain ◽  
Strain Model

A full-range stress-strain model for metallic materials depicting non-linear strain-hardening behavior

2020 ◽  
pp. 030932472095779
Author(s):  
Digendranath Swain ◽  
S Karthigai Selvan ◽  
Binu P Thomas ◽  
Ahmedul K Asraff ◽  
Jeby Philip
Keyword(s):  
Constitutive Model ◽  
Strain Hardening ◽  
Image Correlation ◽  
Linear Strain ◽  
Stress Strain ◽  
Material Parameters ◽  
Hardening Behavior ◽  
Non Linear ◽  
Strain Hardening Behavior ◽  
Strain Model

Ramberg-Osgood (R-O) type stress-strain models are commonly employed during elasto-plastic analysis of metals. Recently, 2-stage and 3-stage R-O variant models have been proposed to replicate stress-strain behavior under large plastic deformation. The complexity of these models increases with the addition of each stage. Moreover, these models have considered deformation till necking only. In this paper, a simplistic multi-stage constitutive model is proposed to capture the strain-hardening non-linearity shown by metals including its post necking behavior. The constitutive parameters of the proposed stress-strain model can be determined using only elastic modulus and yield strength. 3-D digital image correlation was used as an experimental tool for measuring full-field strains on the specimens, which were subsequently utilized to obtain the material parameters. Our constitutive model is demonstrated with an aerospace-grade stainless steel AISI 321 wherein deformation response averaged over the gauge length (GL) and at a local necking zone are compared. The resulting averaged and local material parameters obtained from the proposed model provide interesting insights into the pre and post necking deformation behavior. Our constitutive model would be useful for characterizing highly ductile metals which may or may not depict non-linear strain hardening behavior including their post necking deformations.

Axial Stress–Strain Model for FRCM Confinement of Masonry Columns

2021 ◽  
Vol 25 (1) ◽  
pp. 04020078
Author(s):  
Francesco Micelli ◽  
Gennaro Maddaloni ◽  
Fabio Longo ◽  
Andrea Prota
Keyword(s):  
Axial Stress ◽  
Stress Strain ◽  
Strain Model

scholarly journals Nonlinear Stress-Strain Model for Confined Well Cement

Materials ◽  
2019 ◽  
Vol 12 (16) ◽  
pp. 2626 ◽  
Author(s):  
Yan Li ◽  
Yunhu Lu ◽  
Ramadan Ahmed ◽  
Baoguo Han ◽  
Yan Jin
Keyword(s):  
Axial Stress ◽  
Confining Pressure ◽  
Oil Well ◽  
Stress Strain ◽  
Well Design ◽  
Nonlinear Stress ◽  
Uniaxial Compressive Strength Test ◽  
Ductile Behavior ◽  
Well Cement ◽  
Strain Model

The cement sheath is the key for providing the zonal isolation and integrity of the wellbore. Oil well cement works under confining pressure, so it exhibits strong nonlinear and ductile behavior which is very different from that without confining pressure. Therefore, for the accuracy of the simulation and the reliability of well construction design, a reliable compression stress–strain model is essential for confined well cement. In this paper, a new axial stress–strain model for confined well cement is developed based on uniaxial and triaxial test data, examinations of failure mechanisms, and the results of numerical analysis. A parametric study was conducted to evaluate and calibrate the model. The model is simple and suitable for direct use in simulation studies and well design. Results from this study show the nonlinear compressive behavior of confined well cement can be predicted using the traditional uniaxial compressive strength test measurements.

Axial stress–strain model developed for rectangular RC columns confined with FRP wraps and anchors

Structures ◽  
2020 ◽  
Vol 23 ◽  
pp. 779-788 ◽  
Author(s):  
Haytham F. Isleem ◽  
Muhammad Tahir ◽  
Zhenyu Wang
Keyword(s):  
Axial Stress ◽  
Stress Strain ◽  
Rc Columns ◽  
Strain Model
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