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1

Novel rheological modelling of thermosets and unidirectional monotropic fibre-reinforced thermoset matrix composites

Klasztorny Marian, Nycz Daniel B.

Composites Theory and Practice

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2023

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R. 23, nr 1

3--21

EN

A refined, fully analytical rheological modelling of thermosetting polymers and unidirectional monotropic fibre-reinforced thermoset matrix (UFRT) composites is presented. New polymers and composites under normal conditions, fully relaxed from curing and post-curing stresses, are modelled. The theory includes quasi-static short-term/medium-term/long-term reversible rheological processes. Thermosets are isotropic materials exhibiting linearly viscoelastic shear strains and linearly elastic bulk strains. Fibres are monotropic (transversely isotropic) and linearly elastic materials. A generic function well reproducing the viscoelastic characteristics of thermosets and UFRT composites is a Mittag-Leffler fractional exponential function in an integral form. Coupled/uncoupled standard/inverse constitutive equations of linear rheology are formulated for thermosets and UFRT composites. The equations are mutually analytically transformable. New rheological models (coded H-R/H) for thermosets and UFRT composites are described by the smallest possible number of material constants. The thermoset is described by two independent elastic constants and three independent viscoelastic constants. The homogenized UFRT composite is described by five independent elastic constants and four independent viscoelastic constants, whereby two visco-elastic constants are common to the matrix and the composite. An improved homogenization theory of UFRT composites, based on analytical solutions of the selected tasks of the theory of linear elasticity, is formulated for monotropic fibres and positively validated experimentally. The viscoelastic constants of the thermoset are calculated analytically in an iterative loop using a long-term unidirectional tension creep experimental test. The viscoelastic constants of the UFRT composite are calculated analytically employing H-R/H shear/quasi-shear storage compliances and VECP (the viscoelastic-elastic correspondence principle) shear/quasi-shear storage compliances. The H-R/H rheological model was validated numerically for selected UFRT composites. The validation tests were performed on the enhanced reliability UFRT composites reported by Soden, Hinton, and Kaddour (Composites Science and Technology, 1998, 2002).

2

Numerical modelling of post-ground subsystem in road safety barrier crash tests

Klasztorny Marian, Nycz Daniel Bronisław, Dziewulski Paweł, Gieleta Roman, Stankiewicz Michał, Zielonka Karol

Engineering Transactions

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2019

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Vol. 67, iss. 4

513--534

EN

A new analytical algorithm for determining the elastoplastic parameters for soft, medium and hard plastic cohesive soils, corresponding to *MAT_005_SOIL_AND_FOAM material model available LS-Dyna FE code, was formulated. The numerical modelling of the post-soil subsystem, applicable in the modelling of road safety barrier crash tests using this material model of the roadside dehydrated ground, was developed. The methodology was presented on the example of a Sigma-100 steel post partly driven into the soil and subjected to a static flexural-torsional test using a horizontal tensioned rope. The experimental validation of the numerical modelling and simulation was carried out on the testing site at the Automotive Industry Institute, Warsaw, Poland. The simulations were carried out for numerical models with soil solid elements with reduced integration (ELFORM_1) and full integration (ELFORM_2). The simulation results are in the form of graphs of the rope tension vs. displacement of the upper measurement point of the post and in the form of deformation of the post-soil system. It was shown that the validation experiment was carried out on the post embedded in hydrated soft plastic cohesive soil.

3

New open-source ANSYS-SolidWorks-FLAC3D geometry conversion programs

Bock S.

Journal of Sustainable Mining

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2015

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Vol. 14, iss. 3

124--132

EN

Numerical calculations are used increasingly often to obtain a stress-strain state in many engineering problems. A popular program for this type of calculation which makes use of the finite difference method (a continuous method) is Itasca's FLAC3D. However, an important limitation of FLAC3D is the difficulty of geometry creation. This paper presents new open-source programs allowing the preparation of numerical models in a third-party software (ANSYS, SolidWorks) and their conversion to internal FLAC3D geometry files. The converters have been written in BASH-scripting language and published under the terms of the GNU General Public License, which allows the free distribution and/or modification of the software with some limitations.

4

Numerical modelling of a void behind shaft lining using FDM with a concrete spalling algorithm

Bock S.

Journal of Sustainable Mining

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2014

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Vol. 13, iss. 2

14--21

EN

Purpose: The aim of the research presented in this paper was to determine the impact of voids behind the lining on shaft stability. Methods: This paper presents an example of extending the FLAC3D with the possibility of the simulation of concrete detachment and separation under specific conditions by means of a developed FISH routine. Results: The appearance of voids and cavities behind the lining has been repeatedly observed in active shafts in Polish coal mines and can lead to the emergence of tensile forces in the lining. The study included 366 models of shafts using the rock mass properties of typical shale stone, coal, and sandstone found in the Upper Silesian Coal. Practical implications: The presented concrete spalling algorithm may be used, especially, for the stability evaluation of locally damaged shaft lining or when there is a suspicion of void behind the lining. Originality/ value: An important limitation of all continuous methods is the inability (except when using some additional tools) to simulate the rotations of predefined elements (blocks) and their separation from the rest of the object. The concrete spalling algo-rithm presented extends the capabilities of FLAC3D with the possibility of simulating the detachment and separation of destroyed lining fragments.

5

3D elasto-plastic FEM analysis of the sheet drawing of anisotropic steel sheet

Trzepieciński T.

Archives of Civil and Mechanical Engineering

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2010

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Vol. 10, no 4

95-106

EN

The article presents the experimental and numerical results of rectangular cup drawing of DC03 coldrolled steel sheet. The aim of the experimental study was to analyse material behaviour under deformation. The received numerical results were further verified by experimental results. A 3D parametric finite element model was built using the commercial package ABAQUS. If the material and friction anisotropy are taken into account in the numerical model, this approach undoubtedly gives the most approximate numerical results to real processes.

PL

W pracy przedstawiono wyniki badań eksperymentalnych oraz symulacji numerycznych procesu kształtowania wytłoczek z blachy stalowej głębokotłocznej. Celem badań eksperymentalnych była analiza płynięcia materiału pod wpływem deformacji plastycznej. Otrzymane wyniki symulacji numerycznych zostały zweryfikowane z wynikami eksperymentalnymi. Model numeryczny 3D, bazujący na metodzie elementów skończonych, zbudowano w programie ABAQUS. Uwzględnienie w modelu numerycznym anizotropii plastycznej materiału oraz anizotropii tarcia warunkuje otrzymanie wyników bardziej zbliżonych do wyników rzeczywistego procesu kształtowania.

6

On Finite Element Modelling of Architectural Fabrics for Ganging Roofs

Ambroziak A., Kłosowski P., Woźnica K.

Machine Dynamics Problems

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2006

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Vol. 30, No. 2

7-17

EN

This paper deals with the constitutive modelling and identification of coated woven fabrics properties. The authors give brief characterization of the constitutive models used for the material modelling and discuss in details the fundamental equations of the dense net model. The special identification method of the non-linear elastic properties of the coated fabric is presented. The material parameters are determined on the base of uniaxial tensile tests in the warp and weft directions. For the identification process, techniques using the least squares method are applied. Additionally, the results of the uniaxial tension tests are compared with biaxial tension tests.

7

Mechanical modelling of quasi-brittle shear failure

Hoiseth K. V.

International Journal of Applied Mechanics and Engineering

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2002

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Vol. 7, no 1

221-243

EN

The present paper deals with masonry subjected to combined compression and shear. The purpose of the study was to demonstrate the capability of numerical simulations to reproduce the essential mechanical behaviour, as observed by experiments. A coarse 3-dimensional element mesh was used to study the mechanical behaviour of the Fixed Smeared Crack model, in combination with various shear retention descriptions, and the Rotating Smeared Crack model. The obtained shear-stress/deformation relationships, before onset of cracking, showed that the applied elastic stiffness was somewhat too low, when compared to the average of the test results. This was not due to the geometric modelling, as a coarse mesh should yield a too stiff behaviour. The reason was likely that Young's modulus was taken from uniaxial tests with specimens of another batch than the ones used in the combined compression and shear experiments. With the Rotating Smeared Crack model, a limit load and subsequent global softening was obtained. In the first instance, this was due to rotation of the crack directions, such that increasing shear stress produced crack-planes in the joint element which approached the horizontal orientation, i.e. parallel to the interface between units and joint. Subsequently, the softening behaviour was achieved by a realistic description for compressive states of stress.

8

A method of material modelling with the use of strength hypothesis of inner equilibrium stability

Wegner T. M.

Mechanics and Mechanical Engineering

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2000

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Vol. 4, nr 2

139--148

EN

The paper formulates a nonlinear model of physical properties of material, assuming its small strains. Based on strength hypothesis of stability of inner equilibrium the theoretical values of yield point and tensile strength have been determined for the material. The relationships obtained in the work served for determining material constants of the assumed model of the material.

9

Material modelling for structures subjected to impulsive loading

Cichocki K., Adamczyk R., Ruchwa M.

Computer Assisted Mechanics and Engineering Sciences

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1999

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Vol. 6, No. 2

231-244

EN

The main results of numerical analyses of a possible design configuration of a submerged structure subjected to impulsive loading due to explosion, performed for various material models assumed for a plain concrete are presented and discussed. Three different models were considered - the modified Drucker-Prager plasticity model, brittle cracking model and the elastoplastic model with damage. The present study suggests problems and possible solutions to be applied into numerical analysis of such structures by means of available finite element computer codes.