A COUPLED EXPERIMENTAL AND NUMERICAL APPROACH TO CHARACTERIZE THE ANISOTROPIC MECHANICAL BEHAVIOR OF AORTIC TISSUES

2020 ◽  
Vol 20 (05) ◽  
pp. 2050027
Author(s):  
VERA GRAMIGNA ◽  
GIONATA FRAGOMENI ◽  
CHIARA GIULIA FONTANELLA ◽  
CESARE STEFANINI ◽  
EMANUELE LUIGI CARNIEL
Keyword(s):  
Experimental Data ◽  
Mechanical Behavior ◽  
Computational Models ◽  
Tensile Tests ◽  
Numerical Approach ◽  
Mechanical Tests ◽  
Mechanical Responses ◽  
Biomechanical Behavior ◽  
Axial Tensile ◽  
Constitutive Parameters

Nowadays, the investigation of aortic wall biomechanics is a fundamental tool in clinical research and vascular prosthesis design. This study aims at analyzing the biomechanical behavior of aortic tissues using a coupled experimental and computational approach. Considering the typical fiber-reinforced configuration of aortic tissues, uni-axial tensile tests along six different loading directions were performed on specimens from pig aorta. Starting from the obtained experimental data, a suitable constitutive framework was defined and a methodology for the identification of the constitutive parameters was developed using the inverse analysis of mechanical tests. Transversal stretch versus loading stretch and nominal stress versus loading stretch curves were evaluated, showing the anisotropic and nonlinear mechanical behavior determined by tissue conformation with fibers distributed along preferential directions. In detail, experimental data showed different mechanical responses between longitudinal and circumferential directions, with a greater tissue stiffness along the longitudinal one. The reliability of the developed constitutive framework was evaluated by the comparison between experimental data and model results. The mentioned analysis can be considered as a useful tool for the development of reliable computational models, which allow a better understanding of the pathophysiology of cardiovascular diseases and can be applied for a proper planning of surgical procedures.

ANALYSIS OF THE PASSIVE MECHANICAL BEHAVIOR OF TAENIAE COLI: EXPERIMENTAL AND NUMERICAL APPROACH

2014 ◽  
Vol 14 (02) ◽  
pp. 1450012 ◽  
Author(s):  
EMANUELE LUIGI CARNIEL ◽  
VERA GRAMIGNA ◽  
CHIARA GIULIA FONTANELLA ◽  
CESARE STEFANINI ◽  
ARTURO NICOLA NATALI
Keyword(s):  
Tensile Tests ◽  
Numerical Approach ◽  
Biological Tissues ◽  
Mechanical Tests ◽  
Fundamental Aspect ◽  
Experimental Investigations ◽  
Hyperelastic Materials ◽  
Constitutive Analysis ◽  
Surgical Devices ◽  
Constitutive Parameters

The constitutive analysis of gastrointestinal tissues represents a fundamental aspect for the biomechanical investigation of gastrointestinal structures and organs through the use of computational methods. This approach makes it possible to obtain an accurate and extensive set of results, also offering the possibility to evaluate the interaction with surgical devices. The constitutive analysis of taeniae coli tissue is performed by a multi-disciplinary approach that requires the cooperation between medical, experimental and computational competences, as common practice in biological tissues mechanics. The analysis of taeniae coli histology suggests the assumption of a transversally isotropic scheme, because of the orientation of muscular fibers along a preferential direction. Mechanical tests are designed and planned in consideration of the mentioned structural conformation, considering tensile tests imposed according to different loading directions. The results from histological and experimental investigations lead to the definition of a constitutive model in the framework of fiber-reinforced hyperelastic materials. The constitutive parameters are evaluated by the comparative analysis between experimental and numerical results by means of a minimisation of their discrepancy. The reliability of the constitutive formulation and parameters is assessed by the analysis of additional experimental data and the evaluation of satisfaction of thermo-mechanics requirements about material stability.

scholarly journals Considerations for the design of polymeric biodegradable products

2013 ◽  
Vol 33 (4) ◽  
pp. 293-302 ◽  
Author(s):  
André C. Vieira ◽  
Rui M. Guedes ◽  
Volnei Tita
Keyword(s):  
Experimental Data ◽  
Constitutive Models ◽  
Tensile Tests ◽  
Failure Criteria ◽  
Numerical Approach ◽  
Life Cycles ◽  
Strength Failure ◽  
First Order Kinetics ◽  
User Material Subroutine ◽  
Degradation Time

Abstract Several biodegradable polymers are used in many products with short life cycles. The performance of a product is mostly conditioned by the materials selection and dimensioning. Strength, maximum strain and toughness will decrease along its degradation, and it should be enough for the predicted use. Biodegradable plastics can present short-term performances similar to conventional plastics. However, the mechanical behavior of biodegradable materials, along the degradation time, is still an unexplored subject. The maximum strength failure criteria, as a function of degradation time, have traditionally been modeled according to first order kinetics. In this work, hyperelastic constitutive models are discussed. An example of these is shown for a blend composed of poly(L-lactide) acid (PLLA) and polycaprolactone (PCL). A numerical approach using ABAQUS is presented, which can be extended to other 3D geometries. Thus, the material properties of the model proposed are automatically updated in correspondence to the degradation time, by means of a user material subroutine. The parameterization was achieved by fitting the theoretical curves with the experimental data of tensile tests made on a PLLA-PCL blend (90:10) for different degradation times. The results obtained by numerical simulations are compared to experimental data, showing a good correlation between both results.

Experimental study on tissue phantoms to understand the effect of injury and suturing on human skin mechanical properties

2016 ◽  
Vol 231 (1) ◽  
pp. 80-91 ◽  
Author(s):  
Arnab Chanda ◽  
Vinu Unnikrishnan ◽  
Zachary Flynn ◽  
Kim Lackey
Keyword(s):  
Experimental Study ◽  
Mechanical Behavior ◽  
Human Skin ◽  
Computational Models ◽  
Wound Closure ◽  
Mechanical Tests ◽  
Two Dimensional ◽  
Surgical Interventions ◽  
Tissue Phantom ◽  
Tissue Phantoms

Skin injuries are the most common type of injuries occurring in day-to-day life. A skin injury usually manifests itself in the form of a wound or a cut. While a shallow wound may heal by itself within a short time, deep wounds require surgical interventions such as suturing for timely healing. To date, suturing practices are based on a surgeon’s experience and may vary widely from one situation to another. Understanding the mechanics of wound closure and suturing of the skin is crucial to improve clinical suturing practices and also to plan automated robotic surgeries. In the literature, phenomenological two-dimensional computational skin models have been developed to study the mechanics of wound closure. Additionally, the effect of skin pre-stress (due to the natural tension of the skin) on wound closure mechanics has been studied. However, in most of these analyses, idealistic two-dimensional skin geometries, materials and loads have been assumed, which are far from reality, and would clearly generate inaccurate quantitative results. In this work, for the first time, a biofidelic human skin tissue phantom was developed using a two-part silicone material. A wound was created on the phantom material and sutures were placed to close the wound. Uniaxial mechanical tests were carried out on the phantom specimens to study the effect of varying wound size, quantity, suture and pre-stress on the mechanical behavior of human skin. Also, the average mechanical behavior of the human skin surrogate was characterized using hyperelastic material models, in the presence of a wound and sutures. To date, such a robust experimental study on the effect of injury and sutures on human skin mechanics has not been attempted. The results of this novel investigation will provide important guidelines for surgical planning and validation of results from computational models in the future.

scholarly journals Hydromechanical modeling of granular soils considering internal erosion

2020 ◽  
Vol 57 (2) ◽  
pp. 157-172 ◽  
Author(s):  
Jie Yang ◽  
Zhen-Yu Yin ◽  
Farid Laouafa ◽  
Pierre-Yves Hicher
Keyword(s):  
Experimental Data ◽  
Mechanical Behavior ◽  
Fine Particles ◽  
Numerical Approach ◽  
Internal Erosion ◽  
Erosion Process ◽  
Incremental Model ◽  
Strain Relationship ◽  
Practical Model ◽  
Relationship Of

This paper attempts to formulate a coupled practical model in the framework of continuum mechanics to evaluate the phenomenon of internal erosion and its consequences on the mechanical behavior of soils. For this purpose, a four-constituent numerical approach has been developed to describe the internal erosion process. The detachment and transport of the fine particles have been described by a mass exchange formulation between the solid and fluid phases. The stress–strain relationship of the soil is represented by a nonlinear incremental model. Based on experimental data, this constitutive model has been enhanced by the introduction of a fines content–dependent critical state, which allows accounting for the influence of fines on soil deformation and strength. The applicability of the practical approach to capture the main features of the internal erosion process and its impact on the mechanical behavior of the eroded soil have been validated by comparing numerical and experimental results of internal erosion tests on Hong Kong completely decomposed granite (HK-CDG) mixtures, which demonstrated that the practical model was able to reproduce, with reasonable success, the experimental data. Furthermore, the influence of the stress state, the initial soil density, and the initial fraction of fines have been analyzed through numerical simulations using the proposed model.

scholarly journals Tensile Fracture Behavior of Corroded Pipeline: Part 1—Experimental Characterization

2020 ◽  
Vol 2020 ◽  
pp. 1-14 ◽  
Author(s):  
Yuchao Yang ◽  
Feng Liu ◽  
Feng Xi
Keyword(s):  
Experimental Data ◽  
Tensile Tests ◽  
Reduction Factor ◽  
Tensile Fracture ◽  
Experimental Characterization ◽  
Accelerated Corrosion ◽  
Continuous Increase ◽  
Fracture Patterns ◽  
Axial Tensile ◽  
Strain Relationship

The understanding of the axial tensile behavior of environmentally corroded pipelines is of great significance for the design, maintenance, and evaluation of such structures. This article presents some experimental data recorded from 210 tensile tests on pipe, which were corroded from grade of 10% to 70% by electrochemical accelerated corrosion method. The fracture modes show that, for the uncorroded pipe, the fracture frequently occurs in the middle of the specimen and then propagates perpendicular to the loading direction. However, for the corroded pipe, the crack’s position, evolution angle, and path have strong randomness. The comparative analysis based on the macroscopic stress-strain relationship shows that the rapid decrease of the yield stress, ultimate strength, and strain at the fracture for corroded pipe are correlated with the fracture patterns; i.e., the fracture patterns of pipe are changed from uniform to scattered with the continuous increase of the corrosion rate. The reduction factor based on experimental data is recommended for the consideration of the corrosion effect on the tensile strength of the steel pipe. Discussion on the tensile capacity during the service time is also presented.

A Visco-Hyperelastic Constitutive Model for Multilayer Polymer Membranes and its Application in Packaging Air Cushion

2016 ◽  
Vol 08 (05) ◽  
pp. 1650062
Author(s):  
Yingfeng Liu ◽  
Qiong Rao ◽  
Ming Chen ◽  
Xiongqi Peng ◽  
Shaoqing Shi
Keyword(s):  
Experimental Data ◽  
Constitutive Model ◽  
Mechanical Behavior ◽  
Mechanical Response ◽  
Tensile Tests ◽  
Packaging Material ◽  
Polymer Membrane ◽  
Rate Dependent ◽  
Highly Nonlinear ◽  
Air Cushion

Air cushion is an important packaging material with admirable cushion property in protecting articles from damage. Polymer membrane in air cushion renders a highly nonlinear elastic and rate dependent mechanical behavior in experimental tensile test. A visco-hyperelastic constitutive model for a polymer membrane of an air cushion is developed by additively decomposing its mechanical response into a hyperelastic portion and a viscoelastic portion. Material parameters are consecutively obtained by matching experimental data of static and dynamic uni-axial tensile tests of the membrane, respectively. Compression test of a single air column of the air cushion is conducted as a means of validation on the proposed constitutive model. By comparing simulation results with experimental data, it is shown that the proposed visco-hyperelastic model can properly characterize the mechanical behavior of the air cushion packaging material. The model can be applied to evaluate cushion performance of air cushions and their optimum design.

scholarly journals The Investigation of Microstructure and Mechanical Behavior and the Fractographic Analysis of the Ti49.1Ni50.9 Alloy in States with Different Activation Deformation Volumes

2021 ◽  
Vol 11 (7) ◽  
pp. 3052
Author(s):  
Anna Churakova ◽  
Dmitry Gunderov ◽  
Elina Kayumova
Keyword(s):  
Mechanical Behavior ◽  
Test Temperature ◽  
Elevated Temperatures ◽  
Tensile Tests ◽  
Mechanical Tests ◽  
Fractographic Analysis ◽  
Coarse Grained ◽  
Ultrafine Grained ◽  
Coarse Grained State ◽  
Different Temperatures

In this article, the microstructure and mechanical behavior of the Ti49.1Ni50.9 alloy with a high content of nickel in a coarse-grained state, obtained by quenching, ultrafine-grained (obtained through the equal-channel angular pressing (ECAP) method) and nanocrystalline (high pressure torsion (HPT) + annealing), were investigated using mechanical tensile tests at different temperatures. Mechanical tests at different strain rates for determining the parameter of strain rate sensitivity m were carried out. Analysis of m showed that with an increase in the test temperature, an increase in this parameter was observed for all studied states. In addition, this parameter was higher in the ultrafine-grained state than in the coarse-grained state. The activation deformation volume in the ultrafine-grained state was 2–3 times greater than in the coarse-grained state at similar tensile temperatures. Fractographic analysis of samples after mechanical tests was carried out. An increase in the test temperature led to a change in the nature of fracture from quasi-brittle–brittle (with small pits) at room temperature to ductile (with clear dimples) at elevated temperatures. Microstructural studies were carried out after the tensile tests at different temperatures, showing that at elevated test temperatures, the matrix was depleted in nickel with the formation of martensite twins.

UNCERTAINTY ANALYSIS OF A ONE-DIMENSIONAL CONSTITUTIVE MODEL FOR SHAPE MEMORY ALLOY THERMOMECHANICAL DESCRIPTION

2014 ◽  
Vol 06 (06) ◽  
pp. 1450067 ◽  
Author(s):  
SERGIO A. OLIVEIRA ◽  
MARCELO A. SAVI ◽  
ILMAR F. SANTOS
Keyword(s):  
Experimental Data ◽  
Shape Memory Alloy ◽  
Constitutive Model ◽  
Uncertainty Analysis ◽  
Numerical Simulations ◽  
Shape Memory ◽  
Tensile Tests ◽  
One Dimensional ◽  
Uncertainty Range ◽  
Constitutive Parameters

The use of shape memory alloys (SMAs) in engineering applications has increased the interest of the accuracy analysis of their thermomechanical description. This work presents an uncertainty analysis related to experimental tensile tests conducted with shape memory alloy wires. Experimental data are compared with numerical simulations obtained from a constitutive model with internal constraints employed to describe the thermomechanical behavior of SMAs. The idea is to evaluate if the numerical simulations are within the uncertainty range of the experimental data. Parametric analysis is also developed showing the most sensitive constitutive parameters that contribute to the uncertainty. This analysis provides the contribution of each parameter establishing the accuracy of the constitutive equations.

scholarly journals Finite element modeling of multiple density materials of bone specimens for biomechanical behavior evaluation

2021 ◽  
Vol 3 (9) ◽  
Author(s):  
Sebastián Irarrázaval ◽  
Jorge Andrés Ramos-Grez ◽  
Luis Ignacio Pérez ◽  
Pablo Besa ◽  
Angélica Ibáñez
Keyword(s):  
Finite Elements ◽  
Computational Models ◽  
Reaction Force ◽  
Elastic Stiffness ◽  
Finite Elements Method ◽  
Mechanical Resistance ◽  
Assessment Procedure ◽  
Axial Tomography ◽  
Biomechanical Behavior ◽  
Ct Data

AbstractThe finite elements method allied with the computerized axial tomography (CT) is a mathematical modeling technique that allows constructing computational models for bone specimens from CT data. The objective of this work was to compare the experimental biomechanical behavior by three-point bending tests of porcine femur specimens with different types of computational models generated through the finite elements’ method and a multiple density materials assignation scheme. Using five femur specimens, 25 scenarios were created with differing quantities of materials. This latter was applied to computational models and in bone specimens subjected to failure. Among the three main highlights found, first, the results evidenced high precision in predicting experimental reaction force versus displacement in the models with larger number of assigned materials, with maximal results being an R2 of 0.99 and a minimum root-mean-square error of 3.29%. Secondly, measured and computed elastic stiffness values follow same trend with regard to specimen mass, and the latter underestimates stiffness values a 6% in average. Third and final highlight, this model can precisely and non-invasively assess bone tissue mechanical resistance based on subject-specific CT data, particularly if specimen deformation values at fracture are considered as part of the assessment procedure.

scholarly journals A Material Model for the Orthotropic and Viscous Behavior of Separators in Lithium-Ion Batteries under High Mechanical Loads

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4585
Author(s):  
Marian Bulla ◽  
Stefan Kolling ◽  
Elham Sahraei
Keyword(s):  
Mechanical Behavior ◽  
Lithium Ion ◽  
Material Model ◽  
Tensile Tests ◽  
Element Analysis ◽  
Rate Dependent ◽  
Novel Material ◽  
Li Ion ◽  
Role Based ◽  
Drive Systems

The present study is focused on the development of a material model where the orthotropic-visco-elastic and orthotropic-visco-plastic mechanical behavior of a polymeric material is considered. The increasing need to reduce the climate-damaging exhaust gases in the automotive industry leads to an increasing usage of electric powered drive systems using Lithium-ion (Li-ion) batteries. For the safety and crashworthiness investigations, a deeper understanding of the mechanical behavior under high and dynamic loads is needed. In order to prevent internal short circuits and thermal runaways within a Li-ion battery, the separator plays a crucial role. Based on results of material tests, a novel material model for finite element analysis (FEA) is developed using the explicit solver Altair Radioss. Based on this model, the visco-elastic-orthotropic, as well as the visco-plastic-orthotropic, behavior until failure can be modeled. Finally, a FE simulation model of the separator material is performed, using the results of different tensile tests conducted at three different velocities, 0.1 mm·s−1, 1.0 mm·s−1 and 10.0 mm·s−1 and different orientations of the specimen. The purpose is to predict the anisotropic, rate-dependent stiffness behavior of separator materials in order to improve FE simulations of the mechanical behavior of batteries and therefore reduce the development time of electrically powered vehicles and consumer goods. The present novel material model in combination with a well-suited failure criterion, which considers the different states of stress and anisotropic-visco-dependent failure limits, can be applied for crashworthiness FE analysis. The model succeeded in predicting anisotropic, visco-elastic orthotropic and visco-plastic orthotropic stiffness behavior up to failure.

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