1,721,008 research outputs found
Dataset for: Experimental validation of the sensitivity-based virtual fields for identification of anisotropic plasticity models
No full textThis dataset contains supplementary materials for the publication: 'Experimental validation of the sensitivity-based virtual fields for identification of anisotropic plasticity models', published in the journal Experimental Mechanics. (https://link.springer.com/article/10.1007%2Fs11340-019-00575-3).
It contains:
-calculateYld2000Parameters.m - A Matlab (R2018a, MathWorks) function to provide material parameters of Yld2000-2D model, given experimental measurements.</span
A nonlinear constitutive model for stress relaxation in ligaments and tendons
No full textA novel constitutive model that describes stress relaxation in transversely isotropic soft collagenous tissues such as ligaments and tendons is presented. The model is formulated within the nonlinear integral representation framework proposed by Pipkin and Rogers (J. Mech. Phys. Solids. 16:59-72, 1968). It represents a departure from existing models in biomechanics since it describes not only the strain dependent stress relaxation behavior of collagenous tissues but also their finite strains and transverse isotropy. Axial stress-stretch data and stress relaxation data at different axial stretches are collected on rat tail tendon fascicles in order to compute the model parameters. Toward this end, the rat tail tendon fascicles are assumed to be incompressible and undergo an isochoric axisymmetric deformation. A comparison with the experimental data proves that, unlike the quasi-linear viscoelastic model (Fung, Biomechanics: Mechanics of Living Tissues. Springer, New York, 1993) the constitutive law can capture the observed nonlinearities in the stress relaxation response of rat tail tendon fascicles
A three-dimensional constitutive model for the stress relaxation of articular ligaments
No full textA new nonlinear constitutive model for the three-dimensional stress relaxation of articular ligaments is proposed. The model accounts for finite strains, anisotropy, and strain-dependent stress relaxation behavior exhibited by these ligaments. The model parameters are identified using published uniaxial stress-stretch and stress relaxation data on human medial collateral ligaments (MCLs) subjected to tensile tests in the fiber and transverse to the fiber directions (Quapp and Weiss in J Biomech Eng Trans ASME 120:757-763, 1998; Bonifasi-Lista et al. in J Orthop Res 23(1):67-76, 2005). The constitutive equation is then used to predict the nonlinear elastic and stress relaxation response of ligaments subjected to shear deformations in the fiber direction and transverse to the fiber direction, and an equibiaxial extension. A direct comparison with stress relaxation data collected by subjecting human MCLs to shear deformation in the fiber direction is presented in order to demonstrate the predictive capabilities of the model
Inertial impact tests to identify the plastic properties of metals
No full textThe behavior and failure mechanisms of materials often change at high strain rates (> 100 1/s) when compared with their quasi-static response. These differences are critical when designing structures or components that will be subjected to impact or blast loads. The recent progress in ultra-high speed imaging and full-field measurement techniques provides a unique opportunity to improve the quality of high strain rate test data. The objective of the current work is to design and validate an experimental technique to identify the elastoplastic material properties of metals. The methodology uses an ultra-high speed camera and the grid method to obtain time-resolved full-field deformation data as impact induced stress waves propagate in a sample. The virtual fields method is then used to inversely identify the plastic properties of the specimen. The results for five aluminum 6082-T6 impacted at 50 m/s are presented.</p
Sheet metals characterization using the virtual fields method
No full textIn this work, a characterisation method involving a deep-notched specimen subjected to a tensile loading is introduced. This specimen leads to heterogeneous states of stress and strain, the latter being measured using a stereo DIC system (MatchID). This heterogeneity enables the identification of multiple material parameters in a single test. In order to identify material parameters from the DIC data, an inverse method called the Virtual Fields Method is employed. The method combined with recently developed sensitivity-based virtual fields allows to optimally locate areas in the test where information about each material parameter is encoded, improving accuracy of the identification over the traditional user-defined virtual fields. It is shown that a single test performed at 45°to the rolling direction is sufficient to obtain all anisotropic plastic parameters, thus reducing experimental effort involved in characterisation. The paper presents the methodology and some numerical validation.</p
Dataset for 'Development of new virtual fields for the non-linear virtual fields method'
No full textExperimental data and Matlab codes developed during the PhD project. The data contain raw images collected during experiments, the reference data for material and the VFM program used to process the data. See README file for more details.
Due to the size of the data, it isavailable on request via https://library.soton.ac.uk/datarequest</span
Extension of the sensitivity-based virtual fields to large deformation anisotropic plasticity
No full textThe virtual fields method is an approach to inversely identify material parameters using full-field deformation data. In this work, we extend the sensitivity-based virtual fields to large deformation anisotropic plasticity. The method is firstly generalized to the finite deformation framework and then tested on numerical data obtained from a finite element model of a deep-notched specimen subjected to a tensile loading. We demonstrated the feasibility of the method for two anisotropic plasticity models: Hill48 and Yld2000-2D, and showed that all the parameters could be characterise from such a test. The sensitivity-based virtual fields performed better than the currently accepted standard approach of user-defined ones in terms of accuracy and robustness. The main advantage of the sensitivity-based virtual fields comes from the automation of virtual fields generation. The process can be applied to any geometry and any constitutive law.</p
Sensitivity-based virtual fields for the non-linear virtual fields method
No full textThe virtual fields method (VFM) is an approach to inversely identify material parameters using full-field deformation data. In this manuscript, a new set of automatically-defined virtual fields for non- linear constitutive models has been proposed. These new sensitivity-based virtual fields reduce the influence of noise on the parameter identification. The sensitivity-based virtual fields were applied to a numerical example involving small strain plasticity; however, the general formulation derived for these virtual fields is applicable to any non-linear constitutive model. To quantify the improvement offered by these new virtual fields, they were compared with stiffness-based and manually defined virtual fields. The proposed sensitivity-based virtual fields were consistently able to identify plastic model parameters and outperform the stiffness-based and manually defined virtual fields when the data wascorrupted by noise.<br/
A study of the need for special libraries to serve selected groups of Negro businesses in Atlanta, Georgia, 1952
No full textAn analysis of periodical literature related to library instruction in college and university libraries, 1950-1964, 1966
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