scholarly journals Identification of Material Parameters of a Hyper-Elastic Body With Unknown Boundary Conditions

2018 ◽  
Vol 85 (5) ◽  
Author(s):  
M. Hajhashemkhani ◽  
M. R. Hematiyan ◽  
S. Goenezen
Keyword(s):  
Boundary Conditions ◽  
Elastic Material ◽  
Material Properties ◽  
Soft Tissues ◽  
Material Model ◽  
Unknown Boundary ◽  
Material Parameters ◽  
Hyper Elastic ◽  
Unknown Boundary Conditions

Identification of material properties of hyper-elastic materials such as soft tissues of the human body or rubber-like materials has been the subject of many works in recent decades. Boundary conditions generally play an important role in solving an inverse problem for material identification, while their knowledge has been taken for granted. In reality, however, boundary conditions may not be available on parts of the problem domain such as for an engineering part, e.g., a polymer that could be modeled as a hyper-elastic material, mounted on a system or an in vivo soft tissue. In these cases, using hypothetical boundary conditions will yield misleading results. In this paper, an inverse algorithm for the characterization of hyper-elastic material properties is developed, which takes into consideration unknown conditions on a part of the boundary. A cost function based on measured and calculated displacements is defined and is minimized using the Gauss–Newton method. A sensitivity analysis is carried out by employing analytic differentiation and using the finite element method (FEM). The effectiveness of the proposed method is demonstrated through numerical and experimental examples. The novel method is tested with a neo–Hookean and a Mooney–Rivlin hyper-elastic material model. In the experimental example, the material parameters of a silicone based specimen with unknown boundary condition are evaluated. In all the examples, the obtained results are verified and it is observed that the results are satisfactory and reliable.

Modeling the Inflation Response of C57BL/6 Mouse Sclera

2011 ◽  
Author(s):  
Kristin M. Myers ◽  
Thao D. Nguyen
Keyword(s):  
Material Properties ◽  
Soft Tissues ◽  
Ganglion Cells ◽  
The United States ◽  
Small Rodent ◽  
Tissue Samples ◽  
Tissue Microstructure ◽  
Material Parameters ◽  
Meaningful Material

Small rodent models have become increasingly useful to investigate how the mechanical properties of soft tissues may influence disease development. These animal models allow access to aged, diseased, or genetically-altered tissue samples, and through comparisons with wild-type or normal tissue it can be explored how each of these variables influence tissue function. The challenges to deriving meaningful material parameters for these small tissue samples include designing physiologically-relevant mechanical testing protocols and interpreting the experimental load-displacement data in an appropriate constitutive framework to quantify material parameters. This study was motivated by determining the possible role of scleral material properties in the development of glaucomatous damage to the retinal ganglion cells (RGC). Glaucoma is one of the leading causes of blindness in the United States and in the world with an estimate of 60 million people affected by this year [1]. Through exploring mouse models, the overall goal of our work is to determine the role of scleral material properties and scleral tissue microstructure in the pathogenesis of glaucoma.

Viscoelastic Characterization of Perfused Liver: Indentation Testing and Preliminary Modeling

2007 ◽  
Author(s):  
Amy E. Kerdok ◽  
Robert D. Howe ◽  
Simona Socrate
Keyword(s):  
Constitutive Model ◽  
Multiple Testing ◽  
Mechanical Response ◽  
Ex Vivo ◽  
Unknown Boundary ◽  
Abdominal Organs ◽  
Rheological Modeling ◽  
Unknown Boundary Conditions ◽  
Surgical Manipulation

Computer-aided medical technologies are currently restricted by the limited understanding of the mechanical response of solid abdominal organs to finite loading conditions typical of surgical manipulation [5]. This limitation is a result of the difficulty in acquiring the necessary data on whole organs. To develop a constitutive model capable of predicting complex surgical scenarios, multiple testing modalities need to be simultaneously obtained to capture the fundamental nature of the tissue’s behavior under such conditions. In vivo tests are essential to obtain a realistic response, but their inherent difficulty and unknown boundary conditions makes them an impractical approach. Ex vivo tests are easy to control, but the response is unrealistic. A perfusion apparatus was previously developed that obtained near in vivo conditions for whole livers while allowing the ease of ex vivo testing [3]. This work presents the results from complete viscoelastic testing of whole-perfused livers with surgically relevant time-dependant indentation loading profiles to 35% nominal strain. These results will aid in the development of a constitutive model for the liver whose parameters can be related to the physical constituents of the tissue. As an intermediate modeling step, a 1D rheological modeling tool was used to identify the form and initial parameters for a constitutive model.

A Study on Dynamic Characteristics of Hyper-Elastic Shock Programmer with Truncated Conical Shape

2013 ◽  
Vol 871 ◽  
pp. 240-246
Author(s):  
Tae Ho Yang ◽  
Young Shin Lee ◽  
Yoon Jae Kim ◽  
Tae Hyeong Kim ◽  
Chang Won Shul ◽  
...  
Keyword(s):  
Elastic Material ◽  
Impact Test ◽  
Time History ◽  
Material Model ◽  
Wave Shape ◽  
Time Duration ◽  
Conical Shape ◽  
Design Variables ◽  
Hyper Elastic ◽  
The Impact

Polyurethane (PU) S80A was used as the material of the elastomer of the shock programmer in this paper. To validate Ogden hyper-elastic material model in simulation, the small impact test was performed. As the comparison for the time history of the acceleration between the impact test and simulation was performed. Using the cylindrical shock programmer, the constant used in Ogden hyper-elastic material model was calculated. The wave shape of the acceleration was obtained with the noised sign. To clearly obtain the wave shape of the acceleration the cylindrical shock programmer, the truncated conical shock programmer was used. Using the Ogden hyper-elastic material model, design variables of the shock programmer with the truncated conical shape was studied. Using the shock programmer with truncated conical shape the range on the level and time duration of the acceleration in simulation was from 494.9 m/s2 to 10941 m/s2 and from 1.3 msec to 23.5 msec, respectively.

scholarly journals Retrospective Evaluation and Framework Development of Bone Anisotropic Material Behavior Compared with Elastic, Elastic-Plastic, and Hyper-Elastic Properties

2021 ◽  
Vol 9 (1) ◽  
pp. 9
Author(s):  
Farah Hamandi ◽  
James T. Tsatalis ◽  
Tarun Goswami
Keyword(s):  
Bone Tissue ◽  
Material Properties ◽  
Anisotropic Material ◽  
Material Behavior ◽  
Imaging Data ◽  
Premature Failure ◽  
Elastic Plastic ◽  
Significant Difference ◽  
Hyper Elastic

The main motivation for studying damage in bone tissue is to better understand how damage develops in the bone tissue and how it progresses. Such knowledge may help in the surgical aspects of joint replacement, fracture fixation or establishing the fracture tolerance of bones to prevent injury. Currently, there are no standards that create a realistic bone model with anisotropic material properties, although several protocols have been suggested. This study seeks to retrospectively evaluate the damage of bone tissue with respect to patient demography including age, gender, race, body mass index (BMI), height, and weight, and their role in causing fracture. Investigators believe that properties derived from CT imaging data to estimate the material properties of bone tissue provides more realistic models. Quantifying and associating damage with in vivo conditions will provide the required information to develop mathematical equations and procedures to predict the premature failure and potentially mitigate problems before they begin. Creating a realistic model for bone tissue can predict the premature failure(s), provide preliminary results before getting the surgery, and optimize the design of orthopaedic implants. A comparison was performed between the proposed model and previous efforts, where they used elastic, hyper- elastic, or elastic-plastic properties. Results showed that there was a significant difference between the anisotropic material properties of bone when compared with unrealistic previous methods. The results showed that the density is 50% higher in male subjects than female subjects. Additionally, the results showed that the density is 47.91% higher in Black subjects than Mixed subjects, 53.27% higher than Caucasian subjects and 57.41% higher than Asian. In general, race should be considered during modeling implants or suggesting therapeutic techniques.

Mechanics-based algorithms to determine the current state of a bridge using quasi-static loading and strain measurement

2018 ◽  
Vol 18 (5-6) ◽  
pp. 1874-1888 ◽  
Author(s):  
Pandi Pitchai ◽  
U Saravanan ◽  
Rupen Goswami
Keyword(s):  
Boundary Conditions ◽  
Young’S Modulus ◽  
Material Properties ◽  
High Performance ◽  
High Performance Concrete ◽  
Young's Modulus ◽  
Moving Load ◽  
Material Parameters ◽  
Current State ◽  
Slow Moving

Knowing the current state of a bridge is of interest for a variety of reasons. Some parameters that determine the current state of a bridge are the material properties and boundary conditions. Using strain measurements obtained from a slow-moving vehicle on a bridge, the boundary condition and material properties are determined through a mechanistic-based approach. Observing that the sign of the curvature would change at locations near the support when a load passes over a bridge with end rotational restraints, a methodology for determining the boundary conditions is proposed and validated. The linear elastic properties of the material that the bridge is made up of is determined from the strain measured at locations where the stress is independent of the material property. In this procedure, the structure is analyzed assuming some material properties and the stress at the measured point is determined. Then, the material parameters in the isotropic Hooke’s law are determined so that the stress estimated from the experimentally determined strains agrees with that obtained from the analysis with arbitrarily assumed material parameters. A prestressed high-performance concrete pi-shaped girder tested under a three-axle slow-moving load with strains measured at different locations is used to bring out the efficacy and appropriateness of the proposed methodologies. The mean value of Young’s modulus of the prestressed concrete bridge agrees well with the experimentally determined Young’s modulus.

scholarly journals An inverse method for design and characterisation of acoustic materials

2019 ◽  
Vol 304 ◽  
pp. 02002
Author(s):  
Huina Mao ◽  
Romain Rumpler ◽  
Peter Göransson
Keyword(s):  
Elastic Material ◽  
Material Properties ◽  
Inverse Method ◽  
Measurement Data ◽  
Experimental Tests ◽  
Material Model ◽  
Full Field ◽  
Inverse Estimation ◽  
Anisotropic Elastic ◽  
Anisotropic Elastic Material

This paper presents applications of an inverse method for the design and characterisation of anisotropic elastic material properties of acoustic porous materials. Full field 3D displacements under static surface loads are used as targets in the inverse estimation to fit a material model of an equivalent solid to the measurement data. Test cases of artificial open-cell foams are used, and the accuracy of the results are verified. The method is shown to be able to successfully characterise both isotropic and anisotropic elastic material properties. The paper demonstrates a way to reduce costs by characterising material properties based on the design model without a need for manufacturing and additional experimental tests.

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