scholarly journals Identification of constitutive properties of a laminated rotor at rest through a condensed modal functional

2010 ◽  
Vol 11 (5) ◽  
pp. 309-326 ◽  
Author(s):  
Guillaume Mogenier ◽  
Nouri-Baranger Thouraya ◽  
Regis Dufour ◽  
Lionel Durantay ◽  
Nicolas Barras
Keyword(s):  
Constitutive Properties

Constitutive Properties of Mitral Valve Tissues via Nanoindentation

2021 ◽  
Vol 5 (sup1) ◽  
pp. 48-48
Author(s):  
Amanda Barreto ◽  
Lia Paolino ◽  
Kazue Orikasa-Lopez ◽  
Asad Mirza ◽  
Arvind Agarwal ◽  
...  
Keyword(s):  
Mitral Valve ◽  
Constitutive Properties

Flow slide prediction method: influence of slope geometry

1998 ◽  
Vol 35 (1) ◽  
pp. 43-54 ◽  
Author(s):  
T P Stoutjesdijk ◽  
M B de Groot ◽  
J Lindenberg
Keyword(s):  
Large Scale ◽  
Prediction Method ◽  
Slope Instability ◽  
Initial Stresses ◽  
Triaxial Tests ◽  
Gradual Change ◽  
Loose Sand ◽  
Flow Slide ◽  
Flow Slides ◽  
Constitutive Properties

A quasi-two-dimensional method is presented for predicting liquefaction flow slides in a slope with saturated loose sand. The initial stresses at the start of the actual flow slide process are predicted assuming completely drained conditions during the gradual change in slope geometry caused by erosion or sedimentation. The condition for a flow slide is considered to be the presence of at least one sand element in a metastable stress state, i.e., a state in which the undrained response to any quick change in load, however small it may be, consists of a sudden large increase in pore pressure. The metastability of any sand element is predicted as a function of its constitutive properties, its location in the slope, and the slope geometry. The constitutive properties are derived from dry triaxial tests and basically describe the liquefiability (brittleness) of the sand. The metastability criterion for a soil element in a slope is different from that under triaxial loading. Flow slides observed in large-scale tests occurred at the conditions predicted with the model.Key words: loose sand, flow slides, liquefaction, collapse, slope instability.

Sensitivity of the Shear Wave Speed-Stress Relationship to Soft Tissue Material Properties and Fiber Alignment

2021 ◽  
Author(s):  
Jonathon Blank ◽  
Darryl Thelen ◽  
Matthew S. Allen ◽  
Joshua Roth
Keyword(s):  
Wave Propagation ◽  
Shear Modulus ◽  
Shear Wave ◽  
Wave Speed ◽  
Axial Stress ◽  
Beam Model ◽  
Fiber Alignment ◽  
Wave Speeds ◽  
Shear Wave Speed ◽  
Constitutive Properties

The use of shear wave propagation to noninvasively gauge material properties and loading in tendons and ligaments is a growing area of interest in biomechanics. Prior models and experiments suggest that shear wave speed primarily depends on the apparent shear modulus (i.e., shear modulus accounting for contributions from all constituents) at low loads, and then increases with axial stress when axially loaded. However, differences in the magnitudes of shear wave speeds between ligaments and tendons, which have different substructures, suggest that the tissue’s composition and fiber alignment may also affect shear wave propagation. Accordingly, the objectives of this study were to (1) characterize changes in the apparent shear modulus induced by variations in constitutive properties and fiber alignment, and (2) determine the sensitivity of the shear wave speed-stress relationship to variations in constitutive properties and fiber alignment. To enable systematic variations of both constitutive properties and fiber alignment, we developed a finite element model that represented an isotropic ground matrix with an embedded fiber distribution. Using this model, we performed dynamic simulations of shear wave propagation at axial strains from 0% to 10%. We characterized the shear wave speed-stress relationship using a simple linear regression between shear wave speed squared and axial stress, which is based on an analytical relationship derived from a tensioned beam model. We found that predicted shear wave speeds were both in-range with shear wave speeds in previous in vivo and ex vivo studies, and strongly correlated with the axial stress (R2 = 0.99). The slope of the squared shear wave speed-axial stress relationship was highly sensitive to changes in tissue density. Both the intercept of this relationship and the apparent shear modulus were sensitive to both the shear modulus of the ground matrix and the stiffness of the fibers’ toe-region when the fibers were less well-aligned to the loading direction. We also determined that the tensioned beam model overpredicted the axial tissue stress with increasing load when the model had less well-aligned fibers. This indicates that the shear wave speed increases likely in response to a load-dependent increase in the apparent shear modulus. Our findings suggest that researchers may need to consider both the material and structural properties (i.e., fiber alignment) of tendon and ligament when measuring shear wave speeds in pathological tissues or tissues with less well-aligned fibers.

Partitioned Cyclic Fatigue Damage Evolution Model for PB-Free Solder Materials

2007 ◽  
Author(s):  
Leila J. Ladani ◽  
A. Dasgupta
Keyword(s):  
Fatigue Damage ◽  
Creep Deformation ◽  
Damage Evolution ◽  
Evolution Model ◽  
Micro Scale ◽  
Elastic Plastic ◽  
Constitutive Properties ◽  
Free Solder ◽  
Cyclic Damage ◽  
Creep Deformations

This study presents an approach to predict the degree of material degradation and the resulting changes in constitutive properties during cyclic loading in viscoplastic materials in micro-scale applications. The objective in the modeling approach is to address the initiation and growth of distributed micro-damage, in the form of micro-cracks and micro-voids, as a result of cyclic, plastic and creep deformations of material. This study extends an existing micromechanics-based approach, developed for unified viscoplastic models [Wen, et al, 2001], which uses dislocation mechanics to predict damage due to distributed micro-scale fatigue crack initiation [Mura and Nakasone, 1990]. In the present study, the approach is extended to a partitioned viscoplastic framework, because the micro-scale mechanisms of deformation and damage are different for plastic and creep deformation. In this approach, the model constants for estimating cyclic damage evolution are allowed to be different for creep and plastic deformations. A partitioned viscoplastic constitutive model is coupled with an energy partitioning (E-P) damage model [Oyan and Dasgupta, 1992] to assess fatigue damage evolution due to cyclic elastic, plastic and creep deformations. Wen’s damage evolution model is extended to include damage evolution due to both plastic and creep deformations. The resulting progressive degradation of elastic, plastic and creep constitutive properties are continuously assessed and updated. The approach is implemented on a viscoplastic Pb-free solder. Dominant deformation modes in this material are dislocation slip for plasticity and diffusion-assisted dislocation climb/glide for creep. The material’s behavior shows a good correlation with the proposed damage evolution model. Damage evolution constants for plastic and creep deformation were obtained for this Pb-free solder from load drop data collected from the mechanical cycling experiments at different temperatures. The amount of cyclic damage is evaluated and compared with experiment.

Characterization of Multiaxial Constitutive Properties of Rubbery Polymers

2006 ◽  
Vol 128 (4) ◽  
pp. 489-494 ◽  
Author(s):  
V. Chakkarapani ◽  
K. Ravi-Chandar ◽  
K. M. Liechti
Keyword(s):  
Casting Process ◽  
Shear Resistance ◽  
Monotonic Loading ◽  
Tait Equation ◽  
Confined Compression ◽  
Spray Process ◽  
Volumetric Deformation ◽  
Constitutive Properties ◽  
Bulk Response

Rubbery response of polyurea is examined under monotonic loading in the confined compression, composite compression, and Arcan shear configurations. For polyurea prepared by a casting process, it is shown that while the bulk response is significantly nonlinear, and well fitted by the Tait equation, the shear resistance is extremely small. In contrast, polyurea formed by a spray process shows significant compressibility, inelastic volumetric deformation, and significantly enhanced shear resistance.

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