scholarly journals A Unified Phenomenological Model for Tensile and Compressive Response of Polymeric Foams

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Timothy R. Walter ◽  
Andrew W. Richards ◽  
Ghatu Subhash
Keyword(s):  
Phenomenological Model ◽  
Elastic Moduli ◽  
Mechanical Response ◽  
Model Parameters ◽  
Polymeric Foams ◽  
Compressive Response ◽  
Tensile Response ◽  
Tension And Compression ◽  
Engineering Parameters ◽  
Strain Responses

Tensile and compressive stress-strain responses were obtained for various densities of polymer foams. These experimental data were used to determine relevant engineering parameters (such as elastic moduli in tension and compression, ultimate tensile strength, etc.) as a function of foam density. A phenomenological model applicable for both compressive and tensile responses of polymeric foams is validated by comparing the model to the experimentally obtained compression and tensile responses. The model parameters were analyzed to determine the effect of each parameter on the mechanical response of the foam. The engineering parameters were later compared to the appropriate model parameters and a good correlation was obtained. It was shown that the model indeed captures the entire compressive and tensile response of polymeric foams effectively.

A Study of the Anisotropy and Tension/Compression Behavior of Human Cervical Tissue

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
Kristin M. Myers ◽  
Simona Socrate ◽  
Anastassia Paskaleva ◽  
Michael House
Keyword(s):  
Mechanical Response ◽  
Large Strain ◽  
Critical Role ◽  
Model Parameters ◽  
Anatomical Site ◽  
Cervical Tissue ◽  
Spontaneous Preterm Birth ◽  
Healthy Pregnancy ◽  
Tension And Compression ◽  
Cervical Stroma

The cervix plays a crucial role in maintaining a healthy pregnancy, acting as a mechanical barrier to hold the fetus in utero during gestation. Altered mechanical properties of the cervical tissue are suspected to play a critical role in spontaneous preterm birth. Both MRI and X-ray data in the literature indicate that cervical stroma contains regions of preferentially aligned collagen fibers along anatomical directions (circumferential/longitudinal/radial). In this study, a mechanical testing protocol is developed to investigate the large-strain response of cervical tissue in uniaxial tension and compression along its three orthogonal anatomical directions. The stress response of the tissue along the different orthogonal directions is captured using a minimal set of model parameters generated by fitting a one-dimensional time-dependent rheological model to the experimental data. Using model parameters, mechanical responses can be compared between samples from patients with different obstetric backgrounds, between samples from different anatomical sites, and between the different loading directions for a single specimen. The results presented in this study suggest that cervical tissue is mechanically anisotropic with a uniaxial response dependent on the direction of loading, the anatomical site of the specimen, and the obstetric history of the patient. We hypothesize that the directionality of the tissue mechanical response is primarily due to collagen orientation in the cervical stroma, and provides an interpretation of our mechanical findings consistent with the literature data on preferential collagen alignment.

scholarly journals Evaluation of phenomenological model parameters using density dependent laws for prediction of mechanical response of cellular materials

2015 ◽  
Vol 63 (1) ◽  
pp. 181-191
Author(s):  
H.S.U. Butt ◽  
P. Xue ◽  
B. Hou
Keyword(s):  
Phenomenological Model ◽  
Mechanical Response ◽  
Cellular Materials ◽  
Cellular Material ◽  
Model Parameters ◽  
Design Decision ◽  
Density Dependent ◽  
Best Fitting ◽  
A Current ◽  
Fitting Parameters

Abstract Cellular materials have found wide-spread attention in structural applications involving impact energy absorption. The choice of the most suitable density of a cellular material, for a particular impact application, is based on its mechanical response, which may be obtained through experimental tests and/or models. A current study is focused on prediction of a mechanical response of a wide range of densities of a cellular material using available experimental data of very few densities. Best fitting-parameters of four selected phenomenological models, to fit the available experimental response of three distinct aluminum foam densities, are evaluated. The relationship between the best-fitting parameters and density of the foam is established by using two types of functions. The first function is based on a power law relationship between each parameter and foam density ρ, while the second function assumes each parameter as a linear combination of ρn and ρ, where n is any real number. The former function is found reasonable in the cases of both parameter interpolation and extrapolation while the latter is found reasonable for a parameter interpolation only. The findings of a current study emphasize for a conscious approach during selection of density dependent laws for phenomenological model parameters to avoid any erroneous or misleading design decision.

scholarly journals A General Temperature-Dependent Stress–Strain Constitutive Model for Polymer-Bonded Composite Materials

Polymers ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1393
Author(s):  
Xiaochang Duan ◽  
Hongwei Yuan ◽  
Wei Tang ◽  
Jingjing He ◽  
Xuefei Guan
Keyword(s):  
Composite Materials ◽  
Constitutive Model ◽  
Model Parameters ◽  
Temperature Dependent ◽  
Stress Strain ◽  
Proposed Model ◽  
Single Temperature ◽  
Testing Data ◽  
Bonded Composite ◽  
Tension And Compression

This study develops a general temperature-dependent stress–strain constitutive model for polymer-bonded composite materials, allowing for the prediction of deformation behaviors under tension and compression in the testing temperature range. Laboratory testing of the material specimens in uniaxial tension and compression at multiple temperatures ranging from −40 ∘C to 75 ∘C is performed. The testing data reveal that the stress–strain response can be divided into two general regimes, namely, a short elastic part followed by the plastic part; therefore, the Ramberg–Osgood relationship is proposed to build the stress–strain constitutive model at a single temperature. By correlating the model parameters with the corresponding temperature using a response surface, a general temperature-dependent stress–strain constitutive model is established. The effectiveness and accuracy of the proposed model are validated using several independent sets of testing data and third-party data. The performance of the proposed model is compared with an existing reference model. The validation and comparison results show that the proposed model has a lower number of parameters and yields smaller relative errors. The proposed constitutive model is further implemented as a user material routine in a finite element package. A simple structural example using the developed user material is presented and its accuracy is verified.

Molecular dynamics study on the mechanical response and failure behaviour of graphene: performance enhancement via 5–7–7–5 defects

RSC Advances ◽  
2016 ◽  
Vol 6 (31) ◽  
pp. 26361-26373 ◽  
Author(s):  
G. Rajasekaran ◽  
Avinash Parashar
Keyword(s):  
Molecular Dynamics ◽  
Tensile Strength ◽  
Structural Properties ◽  
Elastic Moduli ◽  
Mechanical Response ◽  
Performance Enhancement ◽  
Structural Defects ◽  
Thick Sheet ◽  
Failure Behaviour ◽  
Production Techniques

A one atom-thick sheet of carbon exhibits outstanding elastic moduli and tensile strength in its pristine form but structural defects which are inevitable in graphene due to its production techniques can alter its structural properties.

scholarly journals Mechanical response and fracture dynamics of polymeric foams

2009 ◽  
Vol 42 (21) ◽  
pp. 214001 ◽  
Author(s):  
S Deschanel ◽  
L Vanel ◽  
N Godin ◽  
E Maire ◽  
G Vigier ◽  
...  
Keyword(s):  
Mechanical Response ◽  
Polymeric Foams ◽  
Fracture Dynamics

Design with Nonhomogeneous Materials—Part I: Pure Bending of Prismatic Bars

1987 ◽  
Vol 109 (1) ◽  
pp. 82-86 ◽  
Author(s):  
V. K. Stokes
Keyword(s):  
Tensile Test ◽  
Material Properties ◽  
Elastic Moduli ◽  
Mechanical Response ◽  
Mechanical Design ◽  
Beam Theory ◽  
Pure Bending ◽  
Strongly Coupled ◽  
Point To Point ◽  
Nonhomogeneous Materials

Because material properties vary from point to point in nonhomogeneous materials, there is some question as to what “properties” are measured in tests such as the tensile test, and how such “properties” can be used in the mechanical design process. In this paper, the mechanical response of nonhomogeneous prismatic bars in pure bending has been shown to depend on parameters that are strongly coupled combinations of geometry and material properties. The purely geometry based inertia tensor in homogeneous beam theory is replaced in the nonhomogeneous case by the rigidity tensor, which combines geometry and material properties. Interpretations for the average elastic moduli, which would be determined by tests on nonhomogeneous materials, have been explored. Also discussed is the usefulness of such average moduli for predicting the mechanical response of nonhomogeneous bars.

Phenomenological Modeling of Carpeted Surface for Drop Simulation of Portable Electronics

2019 ◽  
Vol 141 (2) ◽  
Author(s):  
Abhi Sirimamilla ◽  
Hua Ye ◽  
Yinan Wu
Keyword(s):  
Mechanical Response ◽  
Viscoelastic Model ◽  
Single Layer ◽  
Material Model ◽  
Impact Testing ◽  
Consumer Electronics ◽  
Model Parameters ◽  
Portable Devices ◽  
Impact Surface ◽  
The Impact

Using finite element (FE) analysis to simulate drop impact is widely adopted by the consumer electronics industry in the design process of portable devices. Most of such simulations model impact surface as a rigid or simple elastic surface. While this approach is valid for many common hard surfaces such as wood, tile, or concrete, it often does not provide a realistic risk assessment if the impact surface is a soft surface such as carpet. This paper describes a methodology to create a material model for carpeted impact surface that is suited for FE drop simulation. A multilayer hyperelastic–viscoelastic material model is used to model the mechanical response of the carpet under mechanical impact. Quasi-static and impact testing on the industrial carpet were performed to calibrate the model parameters with the help of optimization. Validation of the model was done by comparing the simulation predictions with measurements from the impact tests performed at different heights. Much better correlation between experimental measurements and simulation predictions were observed when using the multilayer hyper-viscoelastic model for carpet than using a single layer homogenous model. This approach can provide a better estimate and a more accurate representation for device drop risk on carpeted surfaces for design and development of portable products. The methodology can also be used to derive material models for other similar impact surfaces.

Micromechanics of a Planar Hybrid Fibrous Network

1997 ◽  
Vol 67 (12) ◽  
pp. 907-925 ◽  
Author(s):  
Ning Pan ◽  
Julie Chen ◽  
Moon Seo ◽  
Stanley Backer
Keyword(s):  
Elastic Moduli ◽  
Fiber Types ◽  
Statistical Distributions ◽  
Fiber Volume ◽  
Fiber Network ◽  
Tensile Response ◽  
Fibrous Network ◽  
Micromechanical Approach ◽  
Bonding Area ◽  
Orientation Distributions

A micromechanical approach is proposed in this work to predict the initial tensile response under uniaxial loading of a bonded two-dimensional fibrous network consisting of two kinds of fibers. The probabilities and statistical distributions of the hybrid bonding points and free fiber lengths between the bonding points in the structure are first derived, and the deformations of both the fiber segment and the bonding area of a typical microelement of the network are analyzed and calculated. The analysis of an arbitrary microelement is then extended statistically to an intermediate level of the structure, the mesodomain, through which the macroscopic deformations of the structure are computed. Ultimately, the general expressions of elastic moduli and Poisson's ratios for a hybrid fibrous network are obtained. A parametric study examines the relationships between fiber mechanical and dimensional properties, fiber volume fractions of the two fiber types, fiber orientation distributions and the properties of the bonding areas, and the tensile behavior of the structure for an ideal planar fiber network.

Constitutive Modeling of Corneal Tissue: Influence of Three-Dimensional Collagen Fiber Microstructure

2020 ◽  
Vol 143 (3) ◽  
Author(s):  
Shuolun Wang ◽  
Hamed Hatami-Marbini
Keyword(s):  
Extracellular Matrix ◽  
Constitutive Modeling ◽  
Mechanical Response ◽  
Thickness Distribution ◽  
Three Dimensional ◽  
Vital Role ◽  
Collagen Fibrils ◽  
Model Parameters ◽  
Corneal Tissue ◽  
Numerical Predictions

Abstract The cornea, the transparent tissue in the front of the eye, along with the sclera, plays a vital role in protecting the inner structures of the eyeball. The precise shape and mechanical strength of this tissue are mostly determined by the unique microstructure of its extracellular matrix. A clear picture of the 3D arrangement of collagen fibrils within the corneal extracellular matrix has recently been obtained from the secondary harmonic generation images. However, this important information about the through-thickness distribution of collagen fibrils was seldom taken into account in the constitutive modeling of the corneal behavior. This work creates a generalized structure tensor (GST) model to investigate the mechanical influence of collagen fibril through-thickness distribution. It then uses numerical simulations of the corneal mechanical response in inflation experiments to assess the efficacy of the proposed model. A parametric study is also done to investigate the influence of model parameters on numerical predictions. Finally, a brief comparison between the performance of this new constitutive model and a recent angular integration (AI) model from the literature is given.

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