RHEOLOGICAL MODELING OF THE STRESS-STRAIN IN FLAT COMPACTION OF COMPOSITE MATERIALS

2020 ◽  
pp. 78-86
Author(s):  
Б. М. Кумицкий ◽  
Н. А. Саврасова ◽  
А. В. Николайчик ◽  
Е. С. Аралов
Keyword(s):  
Continuous Medium ◽  
Uniaxial Stress ◽  
Two Dimensions ◽  
Inertial Effects ◽  
Stress Strain ◽  
Pressing Process ◽  
Relaxation Of Stresses ◽  
Deformed State ◽  
Rheological Modeling ◽  
Coefficient Of Viscosity

Постановка задачи. В статье исследуется деформационное поведение композиционного материала в процессе его плоского прессования. Для решения этой проблемы предложена реологическая модель, в основе которой лежат явления, протекающие в вязкой (ньютоновской) несжимаемой жидкости, занимающей объем между двумя сближающимися с малой скоростью абсолютно жесткими параллельными плоскостями конечных размеров прямоугольной формы. В рамках механики сплошной среды в условиях плоского деформированного состояния решается задача в двух измерениях о медленном течении в отсутствии объемных сил и инерционных эффектов. При этом решение уравнения движения с условиями неразрывности сводится к известному уравнению Лапласа. Кроме того, на основе модели линейной вязкоупругости и одноосного напряженного состояния предпринята попытка описания релаксационных явлений, протекающих в затвердевающем композите по окончании процесса активного прессования. Результаты и выводы. Получены аналитические зависимости силовых параметров напряженно-деформированного состояния прессуемого композита; получены соотношения для кинематических характеристик процесса прессования; получено выражение для релаксации напряжений в процессе технологической выдержки материала под давлением после окончания активного прессования. Результаты исследования позволяют экспериментально определять численные значения динамического коэффициента вязкости и времени релаксации напряжения, которые являются важными характеристиками при управлении процессами прессования. Statement of the problem. The article investigates the deformation behavior of a composite material in the process of its flat pressing. To solve this problem, a rheological model is proposed which is based on the phenomena occurring in a viscous (Newtonian) incompressible fluid that occupies the volume between two absolutely rigid parallel planes of finite dimensions of rectangular shape approaching at a low speed. Within the framework of mechanics of a continuous medium under conditions of a plane deformed state, the problem is addressed in two dimensions about a slow flow in the absence of volume forces and inertial effects. In this case, the solution of the equation of motion with continuity conditions is reduced to the well-known Laplace equation. In addition, based on the model of linear viscoelasticity and uniaxial stress, an attempt has been made to describe the relaxation phenomena occurring in the solidifying composite at the end of the active pressing process. Results and conclusions. Analytical dependences of the power parameters of the stress-strain of the compressed composite are obtained; relations for the kinematic characteristics of the pressing process are identified; an expression is designed for the relaxation of stresses during the technological holding of the material under pressure following the end of active pressing. The results of the study make it possible to experimentally determine the numerical values of the dynamic coefficient of viscosity and stress relaxation time which are important characteristics in controlling the pressing processes.

scholarly journals RHEOLOGICAL MODELING OF THE STRESS-STRAIN STATE IN FLAT COMPACTION OF COMPOSITE MATERIALS

2021 ◽  
pp. 21-30
Author(s):  
B. M. Kumitsky ◽  
N. A. Savrasova ◽  
A. V. Nikolaichik ◽  
E. S. Aralov
Keyword(s):  
Strain State ◽  
Uniaxial Stress ◽  
Two Dimensions ◽  
Stress Strain ◽  
Stress Strain State ◽  
Pressing Process ◽  
Relaxation Of Stresses ◽  
Deformed State ◽  
Rheological Modeling ◽  
Coefficient Of Viscosity

Statement of the problem. The article investigates the deformation behavior of a composite material in the process of its flat pressing. To solve this problem, a rheological model is proposed, which is based on the phenomena occurring in a viscous (Newtonian) incompressible fluid, which occupies the volume between two absolutely rigid parallel planes of finite dimensions of rectangular shape approaching at a low speed. Within the framework of mechanics of a continuous medium under conditions of a plane deformed state, the problem is solved in two dimensions about a slow flow in the absence of volume forces and inertial effects. In this case, the solution of the equation of motion with continuity conditions is reduced to the well-known Laplace equation. In addition, on the basis of the model of linear viscoelasticity and uniaxial stress state, an attempt has been made to describe the relaxation phenomena occurring in the solidifying composite at the end of the active pressing process. Results and Conclusions. Analytical dependences of the power parameters of the stress-strain state of the compressed composite are obtained; relations for the kinematic characteristics of the pressing process are obtained; an expression is obtained for the relaxation of stresses during the technological holding of the material under pressure after the end of active pressing. The results of the study make it possible to experimentally determine the numerical values of the dynamic coefficient of viscosity and stress relaxation time, which are important characteristics in controlling the pressing processes.

Delamination in the scoring and folding of paperboard

TAPPI Journal ◽  
2012 ◽  
Vol 11 (1) ◽  
pp. 61-66 ◽  
Author(s):  
DOEUNG D. CHOI ◽  
SERGIY A. LAVRYKOV ◽  
BANDARU V. RAMARAO
Keyword(s):  
Finite Element ◽  
Plane Deformation ◽  
Strain Analysis ◽  
Local Strain ◽  
Uniaxial Stress ◽  
Material Model ◽  
Element Model ◽  
Plastic Behavior ◽  
Stress Strain ◽  
Strain Fields

Delamination between layers occurs during the creasing and subsequent folding of paperboard. Delamination is necessary to provide some stiffness properties, but excessive or uncontrolled delamination can weaken the fold, and therefore needs to be controlled. An understanding of the mechanics of delamination is predicated upon the availability of reliable and properly calibrated simulation tools to predict experimental observations. This paper describes a finite element simulation of paper mechanics applied to the scoring and folding of multi-ply carton board. Our goal was to provide an understanding of the mechanics of these operations and the proper models of elastic and plastic behavior of the material that enable us to simulate the deformation and delamination behavior. Our material model accounted for plasticity and sheet anisotropy in the in-plane and z-direction (ZD) dimensions. We used different ZD stress-strain curves during loading and unloading. Material parameters for in-plane deformation were obtained by fitting uniaxial stress-strain data to Ramberg-Osgood plasticity models and the ZD deformation was modeled using a modified power law. Two-dimensional strain fields resulting from loading board typical of a scoring operation were calculated. The strain field was symmetric in the initial stages, but increasing deformation led to asymmetry and heterogeneity. These regions were precursors to delamination and failure. Delamination of the layers occurred in regions of significant shear strain and resulted primarily from the development of large plastic strains. The model predictions were confirmed by experimental observation of the local strain fields using visual microscopy and linear image strain analysis. The finite element model predicted sheet delamination matching the patterns and effects that were observed in experiments.

Three Types of Stress-Strain Relationship’s Comparison of Circular Tubed Reinforced Concrete in FEA

2012 ◽  
Vol 204-208 ◽  
pp. 930-933
Author(s):  
Xiao Hu ◽  
Zhen Lin Chen
Keyword(s):  
Finite Element ◽  
Reinforced Concrete ◽  
Uniaxial Stress ◽  
Steel Tube ◽  
Finite Element Analyses ◽  
Stress Strain ◽  
Concrete Filled Steel Tube ◽  
Bearing Analysis

The paper introduces 3 types of uniaxial stress-strain relationships of concrete filled steel tube by Pan Youguang, Susantha and Saenz, and performs finite element analyses of the axial strengths of 18 CTRC columns, studies the characters of three models, and comprises between the axial strengths from FEA and existed experiments. Results show these 3 types of model are all suitable for bearing analysis, but Pan’s model is more accurate.

scholarly journals Dynamic Testing of Lime-Tree (Tilia Europoea) and Pine (Pinaceae) for Wood Model Identification

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5261
Author(s):  
Anatoly Bragov ◽  
Leonid Igumnov ◽  
Francesco dell’Isola ◽  
Alexander Konstantinov ◽  
Andrey Lomunov ◽  
...  
Keyword(s):  
Dynamic Testing ◽  
Model Identification ◽  
Uniaxial Stress ◽  
Compression Tests ◽  
Stress Strain ◽  
Kolsky Method ◽  
Gas Gun ◽  
Lime Tree ◽  
First Case ◽  
Wood Model

The paper presents the results of dynamic testing of two wood species: lime-tree (Tilia europoea) and pine (Pinaceae). The dynamic compressive tests were carried out using the traditional Kolsky method in compression tests. The Kolsky method was modified for testing the specimen in a rigid limiting holder. In the first case, stress–strain diagrams for uniaxial stress state were obtained, while in the second, for uniaxial deformation. To create the load a gas gun was used. According to the results of the experiments, dynamic stress–strain diagrams were obtained. The limiting strength and deformation characteristics were determined. The fracture energy of lime and pine depending on the type of test was also obtained. The strain rates and stress growth rates were determined. The influence of the cutting angle of the specimens relative to the grain was noted. Based on the results obtained, the necessary parameters of the wood model were determined and their adequacy was assessed by using a special verification experiment.

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