scholarly journals Review of Soft Fluidic Actuators: Classification and Materials Modeling Analysis

2021 ◽  
Author(s):  
Amir Pagoli ◽  
Frederic Chapelle ◽  
Juan Antonio Corrales Ramón ◽  
Youcef Mezouar ◽  
Yuri Lapusta
Keyword(s):  
Material Selection ◽  
True Strain ◽  
Constitutive Models ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Small Range ◽  
Model Free ◽  
Fluidic Actuators ◽  
Strain Stress ◽  
Soft Actuators

Abstract Soft actuators can be classified into five categories: tendon-driven actuators, electroactive polymers (EAPs), shape-memory materials, soft fluidic actuators (SFAs), and hybrid actuators. The characteristics and potential challenges of each class are explained at the beginning of this review. Furthermore, recent advances especially focusing on soft fluidic actuators (SFAs) are illustrated. There are already some impressive SFA designs to be found in the literature, constituting a fundamental basis for design and inspiration. The goal of this review is to address the latest innovative designs for SFAs and their challenges and improvements with respect to previous generations, and help researchers to select appropriate materials for their application. We suggest six influential designs: pneumatic artificial muscles (PAM), PneuNet, continuum arm, universal granular gripper, origami soft structure, and vacuum-actuated muscle-inspired pneumatic (VAMPs). The hybrid design of SFAs for improved functionality and shape controllability is also considered. Modeling SFAs, based on previous research, can be classified into three main groups: analytical methods, numerical methods, and model-free methods. We demonstrate the latest advances and potential challenges in each category. Regarding the fact that the performance of soft actuators is dependent on material selection, we then focus on the behaviors and mechanical properties of the various types of silicone which can be found in the SFA literature. For a better comparison of the different constitutive models of silicone materials which have been proposed and tested in the literature, ABAQUS software is here employed to generate the engineering and true strain-stress data from the constitutive models, and compare them with standard uniaxial tensile test data based on ASTM412. Although the figures presented show that in a small range of stress-strain data, most of these models can predict the material model acceptably, few of them predict it accurately for large strain-stress values.

scholarly journals Ability of Constitutive Models to Characterize the Temperature Dependence of Rubber Hyperelasticity and to Predict the Stress-Strain Behavior of Filled Rubber under Different Defor Mation States

Polymers ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 369
Author(s):  
Xintao Fu ◽  
Zepeng Wang ◽  
Lianxiang Ma
Keyword(s):  
Experimental Data ◽  
Temperature Dependence ◽  
Mechanical Response ◽  
Constitutive Models ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Chain Model ◽  
Stress Strain ◽  
Filled Rubber ◽  
Yeoh Model

In this paper, some representative hyperelastic constitutive models of rubber materials were reviewed from the perspectives of molecular chain network statistical mechanics and continuum mechanics. Based on the advantages of existing models, an improved constitutive model was developed, and the stress–strain relationship was derived. Uniaxial tensile tests were performed on two types of filled tire compounds at different temperatures. The physical phenomena related to rubber deformation were analyzed, and the temperature dependence of the mechanical behavior of filled rubber in a larger deformation range (150% strain) was revealed from multiple angles. Based on the experimental data, the ability of several models to describe the stress–strain mechanical response of carbon black filled compound was studied, and the application limitations of some constitutive models were revealed. Combined with the experimental data, the ability of Yeoh model, Ogden model (n = 3), and improved eight-chain model to characterize the temperature dependence was studied, and the laws of temperature dependence of their parameters were revealed. By fitting the uniaxial tensile test data and comparing it with the Yeoh model, the improved eight-chain model was proved to have a better ability to predict the hyperelastic behavior of rubber materials under different deformation states. Finally, the improved eight-chain model was successfully applied to finite element analysis (FEA) and compared with the experimental data. It was found that the improved eight-chain model can accurately describe the stress–strain characteristics of filled rubber.

Kenaf Silicone Biocomposites: Synthesis and its Hyperelastic Behaviour

2017 ◽  
Vol 900 ◽  
pp. 12-16
Author(s):  
Nurul Nadiah Azmi ◽  
Ahmad Kamil Hussain ◽  
Jamaluddin Mahmud
Keyword(s):  
Tensile Test ◽  
Curve Fitting ◽  
Constitutive Models ◽  
Material Constant ◽  
Numerical Approach ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Fitting Method ◽  
Reinforcement Material ◽  
Curve Fitting Method

Silicone rubber is widely used in various fields but has low strength, whereas kenaf has higher strength. Therefore, this study aims to synthesise a new material that consists of both kenaf and silicone with three different variances and determine its properties using the three most common hyperelastic constitutive models: Neo-Hookean, Mooney-Rivlin and Ogden. In order to obtain the material constant of kenaf silicone biocomposite, experimental and numerical approaches are adapted. The xperimental approach involves synthesising of kenaf silicone biocomposite and uniaxial tensile test, while the numerical approach involves curve fitting method using an excel programme. Curve fitting method was used because the raw data from tensile test alone could not determine the material constant of agar silicone biocomposite. The results show that the numerical value of the material constant increases as the percentage of the reinforcement material (kenaf) increases. However, the tensile strength of the material decreases as the reinforcement material increases.

In Pursuit of an Integrated Methodology for Accurate Elevated Temperature and Superplastic Tensile Testing

2010 ◽  
Author(s):  
Fadi Abu-Farha ◽  
Joshua Sabo ◽  
Craig Herring
Keyword(s):  
Elevated Temperature ◽  
Tensile Testing ◽  
Constitutive Models ◽  
Testing Procedure ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Materials Testing ◽  
Unique Type ◽  
Ambient Temperatures ◽  
The Impact

Hydro and pneumatic sheet metal forming operations are commonly carried out at warm and elevated temperature; hence for modelling the behaviours of the formed materials, testing at such temperatures is necessary. The uniaxial tensile test is the most universally-adopted mechanical testing procedure for material characterisation purposes; yet in spite of its simplicity and standardisation for room temperature testing, the test is problematic at higher than-ambient-temperatures. Perhaps that explains the disagreements between different researchers in the field on some of the most critical aspects of the test. Crucially, any inaccuracies in warm and elevated temperature tensile testing have direct impact on the accuracy of the constitutive models and finite element simulations, which we rely on in running and optimising hydro/pneumatic forming operations. This work presents a comprehensive testing methodology that aims at resolving the most critical of issues encountered in this unique type of testing. The methodology is centred about quick-mount grips that tackle the thermal issues by facilitating mounting the test specimen in a very short time. A testing procedure is devised accordingly, and preliminary testing results are presented to demonstrate the impact of the methodology on the accuracy of the results. In addition, the effect of the specimen geometry on the test outcome is investigated using a wide variety of geometries; an optimised geometry is derived based on the obtained experimental results. The methodology is validated by testing AZ31B-H24 magnesium alloy specimens at different temperatures and strain rates.

scholarly journals True Stress-True Strain Models for Structural Steel Elements

2011 ◽  
Vol 2011 ◽  
pp. 1-11 ◽  
Author(s):  
P. Arasaratnam ◽  
K. S. Sivakumaran ◽  
M. J. Tait
Keyword(s):  
Numerical Analysis ◽  
Tensile Test ◽  
Structural Steel ◽  
Deformation Behavior ◽  
True Strain ◽  
True Stress ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Strain Relationship ◽  
Strain Model

A standard uniaxial tensile test, which establishes the engineering stress-strain relationship, in general, provides the basic mechanical properties of steel required by a structural designer. Modern numerical analysis techniques used for analysis of large strain problems such as failure analysis of steel structures and elements metal forming, metal cutting, and so forth, will require implementation and use of true stress-true strain material characterization. This paper establishes a five stage true stress-strain model for A992 and 350W steel grades, which can capture the behavior of structural steel, including the postultimate behavior of steel, until fracture. The proposed model uses a power law in strain hardening range and a weighted power law in the postultimate range. The true stress-true strain model parameters were established through matching of numerical analysis results with the corresponding standard uniaxial tensile test experimental results. The material constitutive relationship so derived was then applied to predict the load-deformation behavior of coupons with a hole in the middle region subjected to direct tension loading. The predicted load-deformation behavior of perforated tension coupons agreed well with the corresponding test results validating the proposed characterization of the true stress-true strain relationship for structural steel.

Effect of Deformation Temperatures on High Temperature Tensile Instability of Austenitic Stainless Steel

2014 ◽  
Vol 33 (5) ◽  
pp. 463-468
Author(s):  
Hongxia Bian ◽  
Liang Zhu ◽  
Hui Zhou ◽  
Peng Tu
Keyword(s):  
Stainless Steel ◽  
High Temperature ◽  
True Strain ◽  
Rate Sensitivity ◽  
Uniaxial Tensile ◽  
Strain Hardening Exponent ◽  
Uniaxial Tensile Test ◽  
Strain And Strain Rate ◽  
Instability Strain ◽  
High Temperature Tensile

AbstractThe characteristics of instability have been investigated on two low nickel austenite stainless steel at the temperatures of 950–1200 °C through the uniaxial tensile test and tensile unload test. The results show geometrical instability is not concurrent with load instability in high temperature tensile. The deformation of specimens are uniform before the load instability, then appear non-uniform in some local area of specimen but they do not directly lead to the geometric instability. With the increase of deformation temperature, load instability strain and strain hardening exponent n are both no obvious variation, and load instability true strain is close to n and depends on n. The geometric instability strain and strain rate sensitivity coefficient m both increase with the increase of temperature, and the strain between load instability and geometric instability depends on m and is the main part of the geometric instability strain.

Investigation on Elastic Behaviour of DP800 Dual Phase Steel

2015 ◽  
Vol 1134 ◽  
pp. 109-115
Author(s):  
Noraishah Mohamad Noor ◽  
Haryanti Samekto ◽  
Ahmad Razlan Yusoff ◽  
Rasool Mohideen ◽  
Nazrul Idzham Kasim ◽  
...  
Keyword(s):  
Tensile Test ◽  
Power Law ◽  
Dual Phase Steel ◽  
Piecewise Linear ◽  
True Strain ◽  
True Stress ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Dual Phase ◽  
Plasticity Model

The elastic relaxation behavior of dual phase steel DP800 is studied in this investigation, based on experimental and numerical methods the true stress-true strain curve obtained from a standard uniaxial tensile test differs according to angular rolling direction The relationship between true stress and true strain are presented in the form of power law equation. This form of material constitutive model shows that the strength coefficient and strain hardening exponent vary significantly in describing the nonlinear true stress-true strain relationship of the material. Finite Element (FE) calculations with Belytschko-Lin-Tsay shell element formulation are performed using the non-linear FE code Ls-Dyna to predict the plastic deformation of the material. Power Law Isotropic Plasticity criterion is adopted for these numerical analyses. The local strains in plastic deformations zone and true stress-strains characteristics obtained by experiment are compared. Using the same parameter the simulation was applied in different modes which are known as Isotropic Elastic-Plastic Model and Piecewise Linear Isotropic Plasticity Model providd in Ls-Dyna simulation for comparison. In general, good agreement in results is obtained between Power Law Isotropic Plasticity Model is obtained compared to Isotropic Elastic-Plastic Model and Piecewise Linear Isotropic Plasticity Model. It is demonstratedthat the behavior of the strain and the Power law criterion can be determined from uniaxial tensile test with the aid of non-linear FE analyses.

scholarly journals Impact of DIC biases on the selection process of a unique test for anisotropic plasticity characterization

2021 ◽  
Vol 250 ◽  
pp. 01001
Author(s):  
Jean-David Thoby ◽  
Thomas Fourest ◽  
Bertrand Langrand ◽  
Delphine Notta-Cuvier ◽  
Eric Markiewicz
Keyword(s):  
Selection Process ◽  
Constitutive Models ◽  
Field Measurements ◽  
Image Correlation ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Elastoplastic Material ◽  
Anisotropic Plasticity ◽  
Measurement Biases ◽  
Stress States

The exploitation of field measurements with inverse identification methods may reduce the number of required tests to characterize complex material constitutive models, provided that the generated stress field is sensitive enough to the targeted material parameters. For anisotropic elastoplastic material, the objective is to generate various stress states in the specimen through a single test. In this study, the effect of Digital Image Correlation measurement biases on the selection of the most suitable specimen geometry for characterisation of a complex anisotropic plasticity criterion using a unique uniaxial tensile test is investigated. To this aim, finite element (FE) based synthetic images are generated and DIC is used on these images. The biases in DIC measurement result in biased stress states that may cause errors in identification results.

A new pseudo-energy function to simulate the Mullins effect

2017 ◽  
Vol 50 (6) ◽  
pp. 554-575
Author(s):  
Eduardo Guilherme Mötke Wrubleski ◽  
Rogério Marczak
Keyword(s):  
Experimental Data ◽  
Pure Shear ◽  
Constitutive Models ◽  
Constitutive Law ◽  
Hyperelastic Material ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Mullins Effect ◽  
Softening Effect ◽  
Material Models

Several authors have proposed different parameters to include the softening effect in hyperelastic models; however, for a number of materials, softening parameters could be further improved. This article proposes a new softening parameter to include Mullins effect in hyperelastic material models. The methodology employed can be also used in cases with hysteresis or damage in a hyperelastic material, however this methodology modifies the behavior of the material differently from damage theories. Common hyperelastic constitutive models do not include dissipation effects and so the present work intends to fill this gap. Experimental data for silicone in uniaxial tensile test, equibiaxial, and pure shear tests were modeled in order to calibrate the models. The softening parameters essentially changes the constitutive law from the loading to the unloading path. Therefore, it is still necessary to use a hyperelastic model, and here Ogden and Hoss-Marczak material models were used. The obtained results show good agreement with experimental data even when simulating with a compressible finite element code and it can model isotropic Mullins effect.

scholarly journals Dimethicone Crosspolymer Effect on Bio Pad Material

2020 ◽  
Vol 9 (3) ◽  
pp. 2806-2813
Keyword(s):  
Constitutive Models ◽  
Numerical Approach ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Material Constants ◽  
Hyper Elastic ◽  
The Subject ◽  
Stretch Response

Bio pad wound dressing is one of the current material in wound healing technology. This aim of this paper is to study the effects of dimethicone cross polymer on the biomaterial and to investigate the mechanical properties of the bio pad by the integration of experimental and numerical approach. In vitro uniaxial tensile test was performed to compute the stress-stretch response of the materials using ASTM D412 standard. The determination of material constants for the materials via numerical approach can be done by comparing with two hyper elastic constitutive models (Ogden and Neo-Hookean). The results show that Ogden’s exponent and coefficient for the subject estimated to be (μ = 0.434 MPa, α = 1.299) for Sample 1, (μ = 0.428 MPa, α = 1.424) for Sample 2, (μ = 0.463 MPa, α = 1.256) for Sample 3 and (μ = 0.633 MPa, α = 1.001) for Sample 4 respectively. Meanwhile, value of material constants for Neo-Hookeen were estimated to be (C1 = 0.00814 MPa), (C2 = 0.0121 MPa), (C3 = 0.00597 MPa) and (C4 = 0.00739 MPa) for Sample 1, Sample 2, Sample 3 and Sample 4 respectively. Therefore, this study could be useful in future studies in analysis of healing especially in dermatology area.

scholarly journals Biomechanical-Structural Correlation of Chordae tendineae in Animal Models: A Pilot Study

Animals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1678
Author(s):  
Justyn Gach ◽  
Izabela Janus ◽  
Agnieszka Mackiewicz ◽  
Tomasz Klekiel ◽  
Agnieszka Noszczyk-Nowak
Keyword(s):  
Mitral Valve ◽  
Complex Structure ◽  
Future Research ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Histopathological Analysis ◽  
Papillary Muscles ◽  
Chordae Tendineae ◽  
Structural Correlation ◽  
Ring Valve

The mitral valve apparatus is a complex structure consisting of the mitral ring, valve leaflets, papillary muscles and chordae tendineae (CT). The latter are mainly responsible for the mechanical functions of the valve. Our study included investigations of the biomechanical and structural properties of CT collected from canine and porcine hearts, as there are no studies about these properties of canine CT. We performed a static uniaxial tensile test on CT samples and a histopathological analysis in order to examine their microstructure. The results were analyzed to clarify whether the changes in mechanical persistence of chordae tendineae are combined with the alterations in their structure. This study offers clinical insight for future research, allowing for an understanding of the process of chordae tendineae rupture that happens during degenerative mitral valve disease—the most common heart disease in dogs.

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