A three-dimensional numerical analysis of moisture flow in wood and of the wood’s hygro-mechanical and visco-elastic behaviour

AbstractA three-dimensional numerical model was employed in simulating nonlinear transient moisture flow in wood and the wood’s hygro-mechanical and visco-elastic behaviour under such conditions. The model was developed using the finite element software Abaqus FEA®, while taking account of the fibre orientation of the wood. The purpose of the study was to assess the ability of the model to simulate the response of wood beams to bending and to the climate of northern Europe. Four-point bending tests of small and clear wood specimens exposed to a constant temperature and to systematic changes in relative humidity were conducted to calibrate the numerical model. A validation of the model was then performed on the basis of a four-point bending test of solid timber beams subjected to natural climatic conditions but sheltered from the direct effects of rain, wind and sunlight. The three-dimensional character of the model enabled a full analysis of the effects of changes in moisture content and in fibre orientation on stress developments in the wood. The results obtained showed a clear distinction between the effects of moisture on the stress developments caused by mechanical loads and the stress developments caused solely by changes in climate. The changes in moisture that occurred were found to have the strongest effect on the stress state that developed in areas in which the tangential direction of the material was aligned with the exchange surface of the beams. Such areas were found to be exposed to high-tension stress during drying and to stress reversal brought about by the uneven drying and shrinkage differences that developed between the outer surface and the inner sections of the beams.

Download Full-text

Finite Element Method Simulating the Pipeline Mechanical Response During Reel-Lay Installation

Volume 4A: Pipeline and Riser Technology ◽

10.1115/omae2013-10555 ◽

2013 ◽

Cited By ~ 1

Author(s):

Ali A. Dawood ◽

S. Kenny

Keyword(s):

Finite Element ◽

Finite Element Modelling ◽

Continuum Model ◽

Mechanical Response ◽

Three Dimensional ◽

Bending Test ◽

Four Point Bending ◽

Physical Tests ◽

Test Frame ◽

Four Point Bending Test

Finite element modelling procedures to simulate the pipeline mechanical response during reel lay installation are calibrated from the available literature. A three-dimensional continuum model was developed to simulate the bending and straightening processes during reel lay installation and was compared with physical tests conducted within a bending rig and four-point bending test frame. A range of pipeline diameters, wall thicknesses, material grades and weld offsets are examined.

Download Full-text

Numerical characterization of residual stresses in a four-point-bending experiment of textured duplex stainless steel

Archive of Applied Mechanics ◽

10.1007/s00419-021-01931-3 ◽

2021 ◽

Author(s):

S. F. Maassen ◽

H. Erdle ◽

S. Pulvermacher ◽

D. Brands ◽

T. Böhlke ◽

...

Keyword(s):

Residual Stresses ◽

Volume Fraction ◽

Mean Field Theory ◽

Mean Field ◽

Three Dimensional ◽

Bending Test ◽

Element Analysis ◽

Austenitic Phase ◽

Four Point Bending ◽

Taylor Approximation

AbstractThe resulting shapes in production processes of metal components are strongly influenced by deformation induced residual stresses. Dual-phase steels are commonly used for industrial application of, e.g., forged or deep-drawn structural parts. This is due to their ability to handle high plastic deformations, while retaining desired stiffness for the products. In order to influence the resulting shape as well as component characteristics positively it is important to predict the distribution of phase-specific residual stresses which occur on the microscale of the material. In this contribution a comparative study is presented, where two approaches for the numerical simulation of residual stresses are applied. On the one hand a numerically efficient mean field theory is used to estimate on the grain level the total strain, the plastic strains and the eigenstrains based on macroscopic stress, strain and stiffness data. An alternative ansatz relies on a Taylor approximation for the grain level strains. Both approaches are applied to the corrosion-resistant duplex steel X2CrNiMoN22-5-3 (1.4462), which consists of a ferritic and an austenitic phase with the same volume fraction. Mean field and Taylor approximation strategies are implemented for usage in three dimensional solid finite element analysis and a geometrically exact Euler–Bernoulli beam for the simulation of a four-point-bending test. The predicted residual stresses are compared to experimental data from bending experiments for the phase-specific residual stresses/strains which have been determined by neutron diffraction over the bending height of the specimen.

Download Full-text

Investigation of the Elastic Modulus of Polymer Sleepers Under a Quasistatic and Cyclic Loading

Civil and Environmental Engineering ◽

10.2478/cee-2019-0016 ◽

2019 ◽

Vol 15 (2) ◽

pp. 125-133

Author(s):

Vít Lojda ◽

Aran van Belkom ◽

Hana Krejčiříková

Keyword(s):

Elastic Modulus ◽

Cyclic Loading ◽

Prestressed Concrete ◽

Load Level ◽

Bending Test ◽

Elastic Behaviour ◽

Loading Frequency ◽

Wheel Load ◽

Four Point Bending ◽

Four Point Bending Test

AbstractIn ballasted track, the wheel load is transmitted to the subgrade via sleepers commonly made of impregnated wood, prestressed concrete, steel or recently developed polymer sleepers. Mentioned material types of sleepers are characterized by different elastic moduli being a key parameter in any numerical model. Hence, this paper aims to determine the elastic modulus of sleepers subjected to a laboratory four-point bending test. Traffic resembling load level of 60 kN adopted from a typical axle load distributed by the rails to the sleeper was applied in a quasistatic and cyclic loading. The samples included sleepers made of polymers complemented with wood and pre-stressed concrete. The results of this paper are based on the elastic modulus investigation. Main conclusions are focused on the sleeper’s elastic modulus under changing loading frequencies. Wood and prestressed concrete sleepers indicated mainly elastic behaviour resulting in a constant elastic modulus. However, polymer sleepers showed a loading frequency dependent elastic modulus as a result of their viscous elastic behaviour. Moreover, the conclusions of this paper involve E-modulus measurements of impregnated beech sleepers in order to describe their piece by piece elasticity variation due to their natural origin.

Download Full-text

Experimental and numerical analysis of sandwich panels with hybrid core

Journal of Sandwich Structures & Materials ◽

10.1177/1099636216646789 ◽

2016 ◽

Vol 20 (3) ◽

pp. 271-286 ◽

Cited By ~ 6

Author(s):

Robert Studziński ◽

Zbigniew Pozorski

Keyword(s):

Numerical Model ◽

Polyurethane Foam ◽

Laboratory Tests ◽

Sandwich Panels ◽

Interface Layer ◽

Mineral Wool ◽

Bending Test ◽

Damage Initiation ◽

The Core ◽

Four Point Bending

The paper presents the experimental and numerical studies of sandwich panels with a hybrid core. The sandwich panel consists of external steel facings and a core, which is made of polyurethane foam or mineral wool or a combination of those two materials. The polyurethane foam material has a low weight and high thermal insulation properties, while the mineral wool material can provide high acoustic insulation and excellent fire resistance. Various proportions of the core materials are taken into account. It is assumed that a proper combination can provide the benefits of both materials. The structural behavior of a sandwich structure with a hybrid core is observed during laboratory tests. The failure mechanism is investigated in a four-point bending test. The material parameters of the core and facings are determined in standardized tests. The obtained parameters are used for FE simulations of the four-point bending tests. The criteria of damage initiation and propagation are defined in the interface layer of the numerical model. A satisfactory correlation between laboratory tests and numerical results is reported. Additionally, the sensitivity analysis of the numerical model response to the variation of the parameters of the interface is presented.

Download Full-text

Analysis of Space-Time Effect for Footage of Tunnel-Type Anchorage by Tunneling Cycle

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.501-504.1749 ◽

2014 ◽

Vol 501-504 ◽

pp. 1749-1752

Author(s):

Yi Liu ◽

Fu Quan Ji ◽

Pei Shuai Chen

Keyword(s):

Finite Element ◽

Numerical Model ◽

Three Dimensional ◽

Horizontal Displacement ◽

Vertical Displacement ◽

Space Time ◽

Time Effect ◽

Tunnel Wall ◽

Finite Element Software ◽

Construction Methods

This paper introduces a three-dimensional numerical model of simulating the tunneling cycle of tunnel-type anchorage by the large finite element software ABAQUS. With tunneling cycles, the space-time effect for footage is analyzed comparatively, which are between the tunnel in headings and tunnel in foots. There are three parameters for evaluating the construction methods, that contain vertical displacement of tunnel vault, vertical displacement of tunnel invert, and horizontal displacement of tunnel wall. The results show that all the values of the above parameters are in the control. Hence, the construction methods of the engineering are available.

Download Full-text