Anil Misra
@ku.edu
Professor
University of Kansas
RESEARCH, TEACHING, or OTHER INTERESTS
Civil and Structural Engineering, Mechanics of Materials, Computational Mechanics
Scopus Publications
Scopus Publications
Ivan Giorgio, Francesco dell’Isola, Ugo Andreaus, and Anil Misra
Springer Science and Business Media LLC
AbstractWe propose a variational approach that employs a generalized principle of virtual work to estimate both the mechanical response and the changes in living bone tissue during the remodeling process. This approach provides an explanation for the adaptive regulation of the bone substructure in the context of orthotropic material symmetry. We specifically focus upon the crucial gradual adjustment of bone tissue as a structural material that adapts its mechanical features, such as materials stiffnesses and microstructure, in response to the evolving loading conditions. We postulate that the evolution process relies on a feedback mechanism involving multiple stimulus signals. The mechanical and remodeling behavior of bone tissue is clearly a complex process that is difficult to describe within the framework of classical continuum theories. For this reason, a generalized continuum elastic theory is employed as a proper mathematical context for an adequate description of the examined phenomenon. To simplify the investigation, we considered a two-dimensional problem. Numerical simulations have been performed to illustrate bone evolution in a few significant cases: the bending of a rectangular cantilever plate and a three-point flexure test. The results are encouraging because they can replicate the optimization process observed in bone remodeling. The proposed model provides a likely distribution of stiffnesses and accurately represents the arrangement of trabeculae macroscopically described by the orthotropic symmetry directions, as supported by experimental evidence from the trajectorial theory.
Nasser Firouzi and Anil Misra
Elsevier BV
Michele De Angelo, Nurettin Yilmaz, M. Erden Yildizdag, Anil Misra, François Hild, and Francesco dell’Isola
Elsevier BV
An Xu, Shumin Li, Jiyang Fu, Anil Misra, and Ruohong Zhao
Elsevier BV
Angelo Scrofani, Emilio Barchiesi, Bernardino Chiaia, Anil Misra, and Luca Placidi
Mathematical Sciences Publishers
José Manuel Torres Espino, Jaime Heman Espinoza Sandoval, Chuong Anthony Tran, Roberto Fedele, Emilio Turco, Francesco dell’Isola, Luca Placidi, Anil Misra, Francisco James León Trujillo, and Emilio Barchiesi
Springer International Publishing
Ivan Giorgio, Anil Misra, and Luca Placidi
Springer International Publishing
Francesco dell’Isola and Anil Misra
Cellule MathDoc/CEDRAM
Anil Misra, François Hild, and Victor A. Eremeyev
Elsevier BV
Luca Placidi, Emilio Barchiesi, Francesco dell'Isola, Valerii Maksimov, Anil Misra, Nasrin Rezaei, Angelo Scrofani, and Dmitry Timofeev
American Institute of Mathematical Sciences (AIMS)
<abstract><p>We report a continuum theory for 2D strain gradient materials accounting for a class of dissipation phenomena. The continuum description is constructed by means of a (reversible) placement function and by (irreversible) damage and plastic functions. Besides, expressions of elastic and dissipation energies have been assumed as well as the postulation of a hemi-variational principle. No flow rules have been assumed and plastic deformation is also compatible, that means it can be derived by a placement function. Strain gradient Partial Differential Equations (PDEs), boundary conditions (BCs) and Karush-Kuhn-Tucker (KKT) type conditions are derived by a hemi variational principle. PDEs and BCs govern the evolution of the placement descriptor and KKT conditions that of damage and plastic variables. Numerical experiments for the investigated homogeneous cases do not need the use of Finite Element simulations and have been performed to show the applicability of the model. In particular, the induced anisotropy of the response has been investigated and the coupling between damage and plasticity evolution has been shown.</p></abstract>
Ivan Giorgio, Francois Hild, Emaad Gerami, Francesco dell'Isola, and Anil Misra
Elsevier BV
Nasrin Rezaei, Emilio Barchiesi, Dmitry Timofeev, C. Anthony Tran, Anil Misra, and Luca Placidi
Elsevier BV
Luca Placidi, Dmitry Timofeev, Valerii Maksimov, Emilio Barchiesi, Alessandro Ciallella, Anil Misra, and Francesco dell’Isola
Elsevier BV
Mohammadamin Ezazi, Qiang Ye, Anil Misra, Candan Tamerler, and Paulette Spencer
MDPI AG
The low-viscosity adhesive that is used to bond composite restorative materials to the tooth is readily damaged by acids, enzymes, and oral fluids. Bacteria infiltrate the resulting gaps at the composite/tooth interface, demineralize the tooth, and further erode the adhesive. This paper presents the preparation and characterization of a low-crosslink-density hydrophilic adhesive that capitalizes on sol-gel reactions and free-radical polymerization to resist hydrolysis and provide enhanced mechanical properties in wet environments. Polymerization behavior, water sorption, and leachates were investigated. Dynamic mechanical analyses (DMA) were conducted using water-saturated adhesives to mimic load transfer in wet conditions. Data from all tests were analyzed using appropriate statistical tests (α = 0.05). The degree of conversion was comparable for experimental and control adhesives at 88.3 and 84.3%, respectively. HEMA leachate was significantly lower for the experimental (2.9 wt%) compared to control (7.2 wt%). After 3 days of aqueous aging, the storage and rubbery moduli and the glass transition temperature of the experimental adhesive (57.5MPa, 12.8MPa, and 38.7 °C, respectively) were significantly higher than control (7.4MPa, 4.3 MPa, and 25.9 °C, respectively). The results indicated that the autonomic sol-gel reaction continues in the wet environment, leading to intrinsic reinforcement of the polymer network, improved hydrolytic stability, and enhanced mechanical properties.
Nima Nejadsadeghi, Francois Hild, and Anil Misra
Elsevier BV
Nima Nejadsadeghi, Michele De Angelo, Anil Misra, and François Hild
Elsevier BV
E.C. Bryant, K.C. Bennett, N.A. Miller, and A. Misra
Wiley
AbstractA general framework to derive nonlinear elastic and elastoplastic material models from granular micromechanics is proposed, where a constraint‐based variational structure is introduced to classical grain contact‐based homogenization methods of hyperelasticity. Like the classical hyperelastic methods, reference solutions for closed‐form hyperelastic material models are analytically derived from the grain‐scale contact mechanics. However, unlike prior methods, the proposed homogenization framework defines closed‐form hyperelastoplastic material models that extend multiscale variational methods to granular plasticity. The proposed framework is used to develop novel granular micromechanics‐based macroscopic models for a Mises type solid, Drucker–Prager type plasticity, and grain‐contact cohesive‐debonding with a deviatorically and volumetrically coupled nonlinearly elastic response. Macroscopic plastic parameters and yield criteria are explicitly related to their microscale counterparts, for example, the friction coefficient governing intergranular slip. Numerical examples and comparison to measurements from the literature, including triaxial compaction of concrete, are provided to investigate model predictions and demonstrate calibration to experimental data.
Aviral Misra and Anil Misra
Mathematical Sciences Publishers
Paulette Spencer, Qiang Ye, Anil Misra, Josephine R. Chandler, Charles M. Cobb, and Candan Tamerler
Frontiers Media SA
By 2060, nearly 100 million people in the U.S. will be over age 65 years. One-third of these older adults will have root caries, and nearly 80% will have dental erosion. These conditions can cause pain and loss of tooth structure that interfere with eating, speaking, sleeping, and quality of life. Current treatments for root caries and dental erosion have produced unreliable results. For example, the glass-ionomer-cement or composite-resin restorations used to treat these lesions have annual failure rates of 44% and 17%, respectively. These limitations and the pressing need to treat these conditions in the aging population are driving a focus on microinvasive strategies, such as sealants and varnishes. Sealants can inhibit caries on coronal surfaces, but they are ineffective for root caries. For healthy, functionally independent elders, chlorhexidine varnish applied every 3 months inhibits root caries, but this bitter-tasting varnish stains the teeth. Fluoride gel inhibits root caries, but requires prescriptions and daily use, which may not be feasible for some older patients. Silver diamine fluoride can both arrest and inhibit root caries but stains the treated tooth surface black. The limitations of current approaches and high prevalence of root caries and dental erosion in the aging population create an urgent need for microinvasive therapies that can: (a) remineralize damaged dentin; (b) inhibit bacterial activity; and (c) provide durable protection for the root surface. Since cavitated and non-cavitated root lesions are difficult to distinguish, optimal approaches will treat both. This review will explore the multi-factorial elements that contribute to root surface lesions and discuss a multi-pronged strategy to both repair and protect root surfaces. The strategy integrates engineered peptides, novel polymer chemistry, multi-scale structure/property characterization and predictive modeling to develop a durable, microinvasive treatment for root surface lesions.
Paulette Spencer, Anil Misra, Qiang Ye, William D. Picking, Kyle Boone, Nilan Kamathewatta, Linyong Song, Rizacan Sarikaya, John H. Purk, and Candan Tamerler
Elsevier
Luca Placidi, Emilio Barchiesi, Francesco dell'Isola, Valerii Maksimov, Anil Misra, Nasrin Rezaei, Angelo Scrofani, and Dmitry Timofeev
American Institute of Mathematical Sciences (AIMS)
<abstract><p>We report a continuum theory for 2D strain gradient materials accounting for a class of dissipation phenomena. The continuum description is constructed by means of a (reversible) placement function and by (irreversible) damage and plastic functions. Besides, expressions of elastic and dissipation energies have been assumed as well as the postulation of a hemi-variational principle. No flow rules have been assumed and plastic deformation is also compatible, that means it can be derived by a placement function. Strain gradient Partial Differential Equations (PDEs), boundary conditions (BCs) and Karush-Kuhn-Tucker (KKT) type conditions are derived by a hemi variational principle. PDEs and BCs govern the evolution of the placement descriptor and KKT conditions that of damage and plastic variables. Numerical experiments for the investigated homogeneous cases do not need the use of Finite Element simulations and have been performed to show the applicability of the model. In particular, the induced anisotropy of the response has been investigated and the coupling between damage and plasticity evolution has been shown.</p></abstract>
Payam Poorsolhjouy and Anil Misra
Hosokawa Powder Technology Foundation
The grain sizes can significantly influence the granular mechano-morphology, and consequently, the macro-scale mechanical response. From a purely geometric viewpoint, changing grain size will affect the volumetric number density of grain-pair interactions as well as the neighborhood geometry. In addition, changing grain size can influence initial stiffness and damage behavior of grain-pair interactions. The granular micromechanics approach (GMA), which provides a paradigm for bridging the grain-scale to continuum models, has the capability of describing the grain size influence in terms of both geometric effects and grain-pair deformation/dissipation effects. Here the GMA based Cauchy-type continuum model is enhanced using simple power laws to simulate the effect of grain size upon the volumetric number density of grain-pair interactions, and the parameters governing grain-pair deformation and dissipation mechanisms. The enhanced model is applied to predict the macroscopic response of cohesive granular solids under conventional triaxial tests. The results show that decreasing grain-sizes can trigger brittle-to-ductile transition in failure. Grain size is found to affect the compression/dilatation behavior as well as the post-peak softening/hardening of granular materials. The macro-scale failure/yield stress is also found to have an inverse relationship with grain-sizes in consonance with what has been reported in the literature.
Nima Nejadsadeghi and Anil Misra
SAGE Publications
Granular-microstructured rods show strong dependence of grain-scale interactions in their mechanical behavior, and therefore, their proper description requires theories beyond the classical theory of continuum mechanics. Recently, the authors have derived a micromorphic continuum theory of degree n based upon the granular micromechanics approach (GMA). Here, the GMA is further specialized for a one-dimensional material with granular microstructure that can be described as a micromorphic medium of degree 1. To this end, the constitutive relationships, governing equations of motion and variationally consistent boundary conditions are derived. Furthermore, the static and dynamic length scales are linked to the second-gradient stiffness and micro-scale mass density distribution, respectively. The behavior of a one-dimensional granular structure for different boundary conditions is studied in both static and dynamic problems. The effects of material constants and the size effects on the response of the material are also investigated through parametric studies. In the static problem, the size-dependency of the system is observed in the width of the emergent boundary layers for certain imposed boundary conditions. In the dynamic problem, microstructural effects are always present and are manifested as deviations in the natural frequencies of the system from their classical counterparts.
Valerii Maksimov, Emilio Barchiesi, Anil Misra, Luca Placidi, and Dmitry Timofeev
American Society of Civil Engineers (ASCE)
Emilio Barchiesi, Anil Misra, Luca Placidi, and Emilio Turco
Wiley
AbstractAlthough the primacy and utility of higher‐gradient theories are being increasingly accepted, values of second gradient elastic parameters are not widely available due to lack of generally applicable methodologies. In this paper, we present such values for a second‐gradient continuum. These values are obtained in the framework of finite deformations using granular micromechanics assumptions for materials that have granular textures at some ‘microscopic’ scale. The presented approach utilizes so‐called Piola's ansatz for discrete‐continuum identification. As a fundamental quantity of this approach, an objective relative displacement between grain‐pairs is obtained and deformation energy of grain‐pair is defined in terms of this measure. Expressions for elastic constants of a macroscopically linear second gradient continuum are obtained in terms of the micro‐scale grain‐pair parameters. Finally, the main result is that the same coefficients, both in the 2D and in the 3D cases, have been identified in terms of Young's modulus, of Poisson's ratio and of a microstructural length.