scholarly journals Biaxial testing of textile material - methodology and instrument assembly procedure

2021 ◽  
Vol 1209 (1) ◽  
pp. 012030
Author(s):  
N Freiherrova ◽  
M Hornakova ◽  
D Juracka ◽  
L Stulerova ◽  
L Kapolka
Keyword(s):  
Material Model ◽  
Full Potential ◽  
Biaxial Test ◽  
Nonlinear Behaviour ◽  
Membrane Structures ◽  
Biaxial Testing ◽  
Textile Materials ◽  
Biaxial Tests ◽  
Specific Material ◽  
Assembly Procedure

Abstract Membrane structures are becoming popular because of the potential usage in structures with higher aesthetic claims. For the roofing of these structures, different textile materials are used. These special materials offer an alternative to conventional roofing materials and allow, besides its lightweightness, also a possibility to roof a difficult floor plan and big span. When designing such a construction, there are some challenges related to the properties of the specific material. In order to exploit the full potential of textile membrane materials, it is necessary to choose an appropriate material model for numerical modelling, which takes into account its nonlinear behaviour. The two most important material characteristics needed for characterizing the behaviour are Young’s modulus of elasticity and Poisson’s ratio. Since the material is orthotropic in most cases, it is necessary to test the material in two directions; therefore, these characteristics need to be obtained from the biaxial test. This contribution is focused on the research of the methodology of biaxial tests and test instrument assembly procedure, which will be used for the following testing of textile materials.

scholarly journals Forming Limit Differences in Hemispherical Dome and Biaxial Test During Equibiaxial Tension on Cruciform

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Chetan P. Nikhare ◽  
Emmett Vorisek ◽  
John R. Nolan ◽  
John T. Roth
Keyword(s):  
Test Data ◽  
Testing Machine ◽  
Biaxial Stress ◽  
Dome Height ◽  
Forming Limit ◽  
Bulge Test ◽  
Biaxial Test ◽  
Biaxial Testing ◽  
Hemispherical Dome ◽  
Biaxial Tests

Traditionally, the mechanical properties of materials have been characterized using the uniaxial tension test. This test is considered adequate for simple forming operations where single axis loading is dominant. Previous studies, however, have noted that the data acquired from this type of testing are not enough and additional details in other axes under simultaneous deformation conditions are important. To analyze the biaxial strain, some studies have suggested using the limiting dome height test and bulge test. However, these tests limit the extent of using multi-axial loading and the resulting stress pattern due to contact surfaces. Therefore, researchers devised the biaxial machine which is designed specifically to provide biaxial stress components using multiple and varying loading conditions. The idea of this work is to evaluate the relationship between the dome test data and the biaxial test data. For this comparison, cruciform specimens with a diamond shaped thinner gage in the center were deformed with biaxial stretching on the biaxial testing machine. In addition, the cruciform specimens were biaxially stretched with a hemispherical punch in a conventional die-punch setting. Furthermore, in each case, the process was simulated using a three-dimensional (3D) model generated on abaqus. These models were then compared with the experimental results. The forces on each arm, strain path, forming, and formability were analyzed. The differences between the processes were detailed. It was found that biaxial tests eliminated the pressurization effect which could be found in hemispherical dome tests.

Strain Uniformity in Biaxial Specimens is Highly Sensitive to Attachment Details

2009 ◽  
Vol 131 (9) ◽  
Author(s):  
Armin Eilaghi ◽  
John G. Flanagan ◽  
G. Wayne Brodland ◽  
C. Ross Ethier
Keyword(s):  
Finite Element ◽  
Strain Field ◽  
Soft Tissues ◽  
Element Model ◽  
Biaxial Test ◽  
Biaxial Testing ◽  
Attachment Point ◽  
Biaxial Tests ◽  
Field Uniformity ◽  
Actual Geometry

Biaxial testing has been used widely to characterize the mechanical properties of soft tissues and other flexible materials, but fundamental issues related to specimen design and attachment have remained. Finite element models and experiments were used to investigate how specimen geometry and attachment details affect uniformity of the strain field inside the attachment points. The computational studies confirm that increasing the number of attachment points increases the size of the area that experiences sensibly uniform strain (defined here as the central sample region where the ratio of principal strains E11/E22<1.10), and that the strains experienced in this region are less than nominal strains based on attachment point movement. Uniformity of the strain field improves substantially when the attachment points span a wide zone along each edge. Subtle irregularities in attachment point positioning can significantly degrade strain field uniformity. In contrast, details of the apron, the region outside of the attachment points, have little effect on the interior strain field. When nonlinear properties consistent with those found in human sclera are used, similar results are found. Experiments were conducted on 6×6 mm talc-sprinkled rubber specimens loaded using wire “rakes.” Points on a grid having 12×12 bays were tracked, and a detailed strain map was constructed. A finite element model based on the actual geometry of an experiment having an off-pattern rake tine gave strain patterns that matched to within 4.4%. Finally, simulations using nonequibiaxial strains indicated that the strain field uniformity was more sensitive to sample attachment details for the nonequibiaxial case as compared to the equibiaxial case. Specimen design and attachment were found to significantly affect the uniformity of the strain field produced in biaxial tests. Practical guidelines were offered for design and mounting of biaxial test specimens. The issues addressed here are particularly relevant as specimens become smaller in size.

scholarly journals Integrated Experimental and Numerical Comparison of Different Approaches for Planar Biaxial Testing of a Hyperelastic Material

2016 ◽  
Vol 2016 ◽  
pp. 1-12 ◽  
Author(s):  
Andrea Avanzini ◽  
Davide Battini
Keyword(s):  
Standardized Testing ◽  
Imaging Techniques ◽  
Relevant Information ◽  
Testing Procedure ◽  
Hyperelastic Material ◽  
Numerical Comparison ◽  
Biaxial Test ◽  
Biaxial Testing ◽  
Comparison Of Results ◽  
Biaxial Tests

Planar biaxial testing has been applied to a variety of materials to obtain relevant information for mechanical characterization and constitutive modeling in presence of complex stress states. Despite its diffusion, there is currently no standardized testing procedure or a unique specimen design of common use. Consequently, comparison of results obtained with different configurations is not always straightforward and several types of optimized shapes have been proposed. The purpose of the present work is to develop a procedure for comprehensive comparison of results of biaxial tests carried out on the same soft hyperelastic material, using different types of gripping methods and specimen shapes (i.e., cruciform and square). Five configurations were investigated experimentally using a biaxial test rig designed and built by the authors, using digital imaging techniques to track the displacements of markers apposed in selected positions on the surfaces. Then, material parameters for a suitable hyperelastic law were determined for each configuration examined, employing an inverse method which combines numerical simulations with the finite element method (FEM) and optimization algorithms. Finally, efficiency of examined biaxial configurations was assessed comparing stress reductions factor, degree and uniformity of biaxial deformation, and operative strain ranges.

scholarly journals A numerical approach for the modelling of forming limits in hot incremental forming of AZ31 magnesium alloy

2021 ◽  
Author(s):  
Davide Campanella ◽  
Gianluca Buffa ◽  
Ernesto Lo Valvo ◽  
Livan Fratini
Keyword(s):  
Room Temperature ◽  
Incremental Forming ◽  
Material Model ◽  
Numerical Approach ◽  
Forming Limit ◽  
Material Strength ◽  
Wall Angle ◽  
Analytical Expression ◽  
The Poor ◽  
Specific Material

AbstractMagnesium alloys, because of their good specific material strength, can be considered attractive by different industry fields, as the aerospace and the automotive one. However, their use is limited by the poor formability at room temperature. In this research, a numerical approach is proposed in order to determine an analytical expression of material formability in hot incremental forming processes. The numerical model was developed using the commercial software ABAQUS/Explicit. The Johnson-Cook material model was used, and the model was validated through experimental measurements carried out using the ARAMIS system. Different geometries were considered with temperature varying in a range of 25–400 °C and wall angle in a range of 35–60°. An analytical expression of the fracture forming limit, as a function of temperature, was established and finally tested with a different geometry in order to assess the validity.

scholarly journals Study of biaxial mechanical properties of the passive pig heart: material characterisation and categorisation of regional differences

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Fulufhelo Nemavhola
Keyword(s):  
Mechanical Properties ◽  
Constitutive Model ◽  
Computational Models ◽  
Heart Diseases ◽  
Interventricular Septum ◽  
Model Material ◽  
Biaxial Test ◽  
Material Behaviour ◽  
Material Parameters ◽  
Biaxial Tests

AbstractRegional mechanics of the heart is vital in the development of accurate computational models for the pursuit of relevant therapies. Challenges related to heart dysfunctioning are the most important sources of mortality in the world. For example, myocardial infarction (MI) is the foremost killer in sub-Saharan African countries. Mechanical characterisation plays an important role in achieving accurate material behaviour. Material behaviour and constitutive modelling are essential for accurate development of computational models. The biaxial test data was utilised to generated Fung constitutive model material parameters of specific region of the pig myocardium. Also, Choi-Vito constitutive model material parameters were also determined in various myocardia regions. In most cases previously, the mechanical properties of the heart myocardium were assumed to be homogeneous. Most of the computational models developed have assumed that the all three heart regions exhibit similar mechanical properties. Hence, the main objective of this paper is to determine the mechanical material properties of healthy porcine myocardium in three regions, namely left ventricle (LV), mid-wall/interventricular septum (MDW) and right ventricle (RV). The biomechanical properties of the pig heart RV, LV and MDW were characterised using biaxial testing. The biaxial tests show the pig heart myocardium behaves non-linearly, heterogeneously and anisotropically. In this study, it was shown that RV, LV and MDW may exhibit slightly different mechanical properties. Material parameters of two selected constitutive models here may be helpful in regional tissue mechanics, especially for the understanding of various heart diseases and development of new therapies.

scholarly journals Strength characterization of glass/epoxy plain weave composite under different biaxial loading ratios

2020 ◽  
Vol 54 (19) ◽  
pp. 2549-2563
Author(s):  
A Kobeissi ◽  
P Rahme ◽  
L Leotoing ◽  
D Guines
Keyword(s):  
Biaxial Loading ◽  
Central Zone ◽  
Correlation Method ◽  
Axial Loading ◽  
Failure Criteria ◽  
Image Correlation ◽  
Biaxial Test ◽  
Cruciform Specimen ◽  
Plain Weave ◽  
Biaxial Tests

Over the past years, various studies have been investigated in order to characterize the behavior of composite materials under different multi-axial loading conditions. One of the most used biaxial techniques is the in-plane biaxial test on cruciform specimens. To achieve reliable biaxial failure results, the design of the cruciform specimen presents a crucial part. Previous studies show that there is no well-adapted cruciform geometry for the composite biaxial tests. In this paper, an optimal cruciform specimen has been defined numerically for the composite characterization test. The specimen is composed of two aluminum tabs glued on top and bottom side of the plain-weave glass/epoxy composite. Finite element simulations have been carried out in order to study the influence of the aluminum grade and thickness on the stress distribution in the composite. An experimental validation confirms the failure of the specimen in the central zone under three different biaxial tensile ratios. The experimental strains were evaluated using the digital image correlation method. The traction/traction quadrant of the failure envelop was obtained and compared with different failure criteria. The maximum strain criterion shows a good agreement with the experimental results.

COUPLED MAGNETIC FIELD AND VISCOELASTICITY OF FERROGEL

2011 ◽  
Vol 03 (02) ◽  
pp. 259-278 ◽  
Author(s):  
YI HAN ◽  
WEI HONG ◽  
LEANN FAIDLEY
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Material Model ◽  
Finite Element Code ◽  
Equilibrium Thermodynamics ◽  
Numerical Examples ◽  
Rate Dependent ◽  
The Matrix ◽  
Specific Material ◽  
Soft Polymer

Composed of a soft polymer matrix and magnetic filler particles, ferrogel is a smart material responsive to magnetic fields. Due to the viscoelasticity of the matrix, the behaviors of ferrogel are usually rate-dependent. Very few models with coupled magnetic field and viscoelasticity exist in the literature, and even fewer are capable of reliable predictions. Based on the principles of non-equilibrium thermodynamics, a field theory is developed to describe the magneto-viscoelastic property of ferrogel. The theory provides a guideline for experimental characterizations and structural designs of ferrogel-based devices. A specific material model is then selected and the theory is implemented in a finite element code. Through numerical examples, the responses of a ferrogel in uniform and non-uniform magnetic fields are analyzed. The dynamic response of a ferrogel to cyclic magnetic fields is also studied, and the prediction agrees with our experimental results. In the reversible limit, our theory recovers existing models for elastic ferrogel, and is capable of capturing some instability phenomena.

Application of a Smooth Approximation of the Schmid’s Law to a Single Crystal Gas Turbine Blade: Part 1—Theory and Governing Equations

2012 ◽  
Author(s):  
Alessandro D. Ramaglia
Keyword(s):  
Single Crystal ◽  
Constitutive Models ◽  
Material Model ◽  
Research Literature ◽  
Elastic Behaviour ◽  
Full Potential ◽  
Smooth Approximation ◽  
Suitable Material ◽  
Von Mises ◽  
Term Creep

In industrial practice, the choice of the most suitable material model does not solely rely on the ability of the model in describing the intended phenomena. Most of the choice is often based on a trade-off between a great variety of factors. Robustness, cost and time for the minimum testing campaign necessary to identify the model and pre-existing standard practices are only a few of them. This is particularly true in the case of nonlinear structural analyses because of their intrinsic difficulties and the higher level of skills needed to carefully exploit their full potential. So, despite the great progress in this field, in certain cases it is desirable to use plasticity models that are rate-independent and possess very simple hardening terms. This is for example the case in which long term creep can be an issue or when the designer may want to treat separately different phenomena contributing to inelastic deformation. If the material to be modelled is isotropic, commercial FE packages are able to deal with such problems in almost every case. On the contrary for anisotropic materials like Ni-based super-alloys cast as single crystals, the choice of the designer is more limited and despite the large amount of research literature on the subject, single crystal constitutive models remain quite difficult to handle, to implement into FE codes, to calibrate and to validate. Such difficulties, coupled with the unavoidable approximations introduced by any model, often force the practice of using oversimplifications of the material behaviour. In what follows this problem is addressed by showing how single crystal plasticity modelling can be reduced to the adoption of an anisotropic elastic behaviour with a sort of von Mises yield surface.

Pressurization and Annealing Effect Analysis Through Hole Expansion

2019 ◽  
Author(s):  
Chetan P. Nikhare
Keyword(s):  
Sustainable Manufacturing ◽  
Ductile Material ◽  
Test Machine ◽  
Biaxial Test ◽  
Effect Analysis ◽  
Hole Expansion ◽  
Biaxial Tests ◽  
Deformation Mechanics ◽  
Conical Tool ◽  
The Impact

Abstract Due to continuous push towards environmental regulations to reduce the impact on the environment by reducing the fuel consumption, and concerns on limited resources, the more sustainable manufacturing is in demand. More abundance material like iron-carbon based alloy are higher strength and easily formable but ways are research to reduce the weight of created part by reducing the thickness due to density issue. Some low dense material is the alternatives but they miss the easy to deform spot. The present study is focused on how to make the material more deformable in the process by evaluating the parameters in deformation through the hole expansion process. For this study, four tests were chosen hemispherical dome test, cylindrical tool test, conical tool test, and biaxial test. In all tests, only the biaxial test machine does not use the rigid tool to deform the hole while all other test used the rigid tool punch to deform the hole. Cruciform specimen dimension was used to make the sample, which fits in all of the considered tests. A hole was created at the center of the specimen which will be expanded in all tests. In all tests the deformation mechanics and hole expansion was studied. Force-displacement curves were plotted and discussed. In addition, tests were also performed on annealed material to understand the hole expansion in ductile material. Based on the results it was observed that biaxial tests do not provide any pressurization effect and all test which includes the rigid tool to deform the hole does. Due to the pressurization effect, the hole was expanded more. It was also noted that the hole expansion was more in ductile material and pressurization effect increases with ductile material.

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