Sreten Mastilovic - Academia.edu (original) (raw)
Papers by Sreten Mastilovic
Engineering Failure Analysis
Engineering Failure Analysis, 2022
International Journal of Damage Mechanics, 2016
The focus of the present article is on the size effect of a transition region from the damaged to... more The focus of the present article is on the size effect of a transition region from the damaged to the fragmented phase in impact-induced breakup of a slender projectile. Molecular dynamics simulations of the classic ballistic Taylor test are performed with a simple generic model to explore an extended low-energy range. In the simulation setup, flat-ended, monocrystalline, nanoscale projectiles, with a fixed aspect ratio but 10 different diameters, collide perpendicularly with a rough rigid wall. With gradually increasing impact energy, a non-negligible projectile disintegration eventually takes place and is identified with the damage-fragmentation phase transition. These atomistic simulations offer an indispensable tool to gain an insight into damage evolution in the neighborhood of the damage-fragmentation transition resulting in the occurrence of fragmentation at the critical point. A finite size scaling analysis of the average fragment mass is carried out to determine critical ex...
International Journal of Damage Mechanics, 2007
The statistical damage model presented by the authors in the previous article of this series is u... more The statistical damage model presented by the authors in the previous article of this series is used to formulate analytical constitutive relations for the hardening and softening phases of two-dimensional lattices. An alternative approach to the classical damage parameter approach is presented here. A semi-empirical model based on extreme value theory (EVT) is offered.
DOMESTIC COLD WATER CALCULATION-CHANGE HOUSE 3. DOCUMENT IDENTIFIER (Including Rev. No.) 4. REV. NO.
Theoretical and Applied Fracture Mechanics, 2001
The present study suggests that molecular and particle dynamics simulations can provide the basis... more The present study suggests that molecular and particle dynamics simulations can provide the basis for estimates of qualitative and quantitative aspects of damage in materials with inferior cohesive strength subjected to high strain rate loading. Two examples demonstrate that the traditional continuum models are of limited value in modeling of the class of considered problems.
Mechanics of Materials, 2008
The present study focuses on the plane strain problem of medium-to-high strain-rate loading of an... more The present study focuses on the plane strain problem of medium-to-high strain-rate loading of an idealized brittle material with random microstructure. The material is represented by an ensemble of “continuum particles” forming a two-dimensional geometrically and structurally disordered lattice. Performing repeated lattice simulations for different physical realizations of the microstructural statistics offers possibility to investigate universal trends in which the
Mathematics and Mechanics of Solids, 2014
A series of molecular-dynamics simulations of the classic Taylor impact test is performed by usin... more A series of molecular-dynamics simulations of the classic Taylor impact test is performed by using a flat-ended monocrystalline nanoscale projectile made of the Lennard-Jones two-dimensional solid. The nanoprojectile striking velocities range from 0.75 to 7 km/s. These atomistic simulations offer insight into nature of fragment distributions and evolution of state parameters. According to the simulation results, the cumulative distribution of fragment sizes in the course of this non-homogeneous fragmentation process for hypervelocity impacts appears to be well represented by the bimodal-exponential distribution commonly observed during high-energy uniform fragmentation events. For more moderate impact velocities, the cumulative distribution of fragment sizes, in addition to the bimodal-exponential part, exhibits a large-fragment tail. Temporal evolutions on instantaneous kinetic temperature, stress and strain invariants are presented and discussed. Scaling relations between temperat...
Journal of Engineering Mechanics, 1996
Brittle-Ductile Transition in Porous Rocks by Cap Model By Vlado A. Lubarda,1 Sreten Mastilovic,2... more Brittle-Ductile Transition in Porous Rocks by Cap Model By Vlado A. Lubarda,1 Sreten Mastilovic,2 and Jaroslaw Knap3 Abstract: A ... expo-nential) dependence on the hydrostatic stress was also used, eg, Bresler and Pister (1958), DiMaggio and Sandler (1971), and Simo et al. ...
The statistical damage model presented by the authors in the previous paper of this series is use... more The statistical damage model presented by the authors in the previous paper of this series is used to formulate analytical constitutive relations for the hardening and softening phases of two-dimensional lattices. A proper definition of the damage parameter for the softening is introduced. The results confirm that the analytical model can be used for the study of the softening phase and failure. This research offers a seminal basis for Damage Tolerance Principles technology standards of the commercial airplane industry.
International Journal of Damage Mechanics, 2008
The disordered 2D lattices are used extensively to study damage evolution and fracture of inhomog... more The disordered 2D lattices are used extensively to study damage evolution and fracture of inhomogeneous or multi-phase systems. The present note addresses their initial elastic response during dynamic loading. Namely, a transition from short-time values of modulus of elasticity and Poisson's ratio to respective long-time values, which is not accompanied by the corresponding change of stiffness tensor components. The study is performed on three 2D truss-type lattices. It is demonstrated that the difference between the two sets of elastic properties is a result of combining effects of the initial lateral inertia and the disorder of the system.
Theoretical and Applied Mechanics
The objective of the present review is twofold. First, it aims at highlighting some sigmoid and r... more The objective of the present review is twofold. First, it aims at highlighting some sigmoid and reverse-sigmoid response patterns observed recently in the course of simulations of the high-strain-rate loading of (mostly, quasibrittle) solids. Second, it aims at reviewing various properties of two models used frequently as curve fitting tools for nonlinear and saturable phenomena. These two models-inspired by the Hill and the Weibull cumulative distribution functions-are bounded by two horizontal asymptotes with a smooth transition between the baseline and the final saturation state, characterized by a non-negative (a non-positive) derivative at each point for the sigmoid (the reverse-sigmoid) shape. Although they were used primarily for data fitting because of their flexibility and effectiveness, these nonlinear models possess other properties useful for the analysis of the irreversible, nonlinear and far-from-equilibrium phenomena. The main features of these two models are systemat...
Latin American Journal of Solids and Structures
Molecular dynamics simulations of the ballistic Taylor test are used to explore correlation betwe... more Molecular dynamics simulations of the ballistic Taylor test are used to explore correlation between the largest fragment mass and the impact energy of a projectile as well as a set of selected state variables. Flat-ended, monocrystalline, nanoscale bars collide with a rigid wall with striking velocities ranging from 0.27 km/s to 60 km/s. The investigation emphasis is on two border regions of the emerging nonlinear phenomenological model identified with two transitions: the damage-fragmentation transition and the shattering transition. In between these two nonlinear regions, the maximum fragment mass is largely inversely proportional to the impact energy, and the maximum values of the pressure, temperature, and the square of the effective strain. A reverse-sigmoid phenomenological model is proposed to capture the unifying features of this nonlinear and saturable dependence. A crystallographic orientation dependence of the damage-fragmentation transition parameters is investigated.
Engineering Fracture Mechanics, Nov 1, 1994
ABSTRACT The paper presents a rate-type constitutive analysis of damage, applicable to brittle ma... more ABSTRACT The paper presents a rate-type constitutive analysis of damage, applicable to brittle materials whose elastic properties degrade during a deformation process. Different tensile and compressive material responses are modeled incorporating positive and negative projections of the stress or strain tensors. Proposed evolution laws for the rate of compliance tensors are consistent with some of the prominent features of brittle material response. A new structure of the damage surface is introduced for a more accurate account of the effects of the hydrostatic states of stress on the overall response. Derived rate constitutive equations provide the explicit representation of the tangent compliance tenser. The proposed model is applied to uniaxial tension and compression to illustrate nonlinear relationships between stress and longitudinal, lateral, and volumetric strains. The proposed model is compared with some of the existing theories.
Journal of Applied Mechanics, Sep 1, 1999
The objective of this study is to formulate a simple, rational model for estimates of the penetra... more The objective of this study is to formulate a simple, rational model for estimates of the penetration depth of rigid long rods through materials susceptible to microcracking. The proposed is based on the target resistance estimated using the particle dynamic simulations. All material parameters of the model can be identified and measured in laboratory. The accuracy of this simple model is found to be satisfactory.
The present study focuses on the kinetic and non-deterministic aspects of the brittle to quasi-br... more The present study focuses on the kinetic and non-deterministic aspects of the brittle to quasi-brittle transition. A solid is approximated by a lattice formed by the interacting 'continuum particles' and the evolution of damage is estimated using particle dynamics. The onset of transition is measured by the rate of the change of correlation length. The proposed method is illustrated on the examples of creep rupture, strain localization and dynamic expansion of a circular void in a 'brittle' plate. Sommario. Viene posta l'attenzione sugli aspetti cinetici e non deterministici della transizione dal comportamento fragile a quello quasi-fragile. Un solido viene approssimato da un reticolo formato da particelle interagenti e l'evoluzione del danno viene stimata tramite la dinamica delle particelle. L'inizio della transizione viene misurato tramite la variazione della lunghezza di correlazione. Il metodo proposto viene illustrato su esempi di rottura per 'creep', localizzazione della deformazione e l'espansione di un foro circolare in una piastra fragile.
International Journal of Damage Mechanics, 2010
This article illuminates some general features and provides elementary interpretations of the def... more This article illuminates some general features and provides elementary interpretations of the deformation, damage, and failure of brittle solids characterized by very low fracture energy. The dynamic response of these materials is determined to a large extent by stochastic and random factors. The investigation emphasis is on the moderate-to-extremely high rate range (10 s-1, 1 × 109 s-1), explored under practically identical in-plane stress conditions. The statistical approach is based on repeated particle dynamics simulations for different physical realizations of micromechanical disorder of a 2D brittle discrete system. The proposed strategy is computationally intensive, which necessitates simplicity of the laws governing the interparticular interaction. Based on the simulation results, an expression is proposed to model the mean tensile strength dependence on the strain rate. The linearity of the rate dependence of the stress-peak macroscopic response parameters is observed and d...
Engineering Failure Analysis
Engineering Failure Analysis, 2022
International Journal of Damage Mechanics, 2016
The focus of the present article is on the size effect of a transition region from the damaged to... more The focus of the present article is on the size effect of a transition region from the damaged to the fragmented phase in impact-induced breakup of a slender projectile. Molecular dynamics simulations of the classic ballistic Taylor test are performed with a simple generic model to explore an extended low-energy range. In the simulation setup, flat-ended, monocrystalline, nanoscale projectiles, with a fixed aspect ratio but 10 different diameters, collide perpendicularly with a rough rigid wall. With gradually increasing impact energy, a non-negligible projectile disintegration eventually takes place and is identified with the damage-fragmentation phase transition. These atomistic simulations offer an indispensable tool to gain an insight into damage evolution in the neighborhood of the damage-fragmentation transition resulting in the occurrence of fragmentation at the critical point. A finite size scaling analysis of the average fragment mass is carried out to determine critical ex...
International Journal of Damage Mechanics, 2007
The statistical damage model presented by the authors in the previous article of this series is u... more The statistical damage model presented by the authors in the previous article of this series is used to formulate analytical constitutive relations for the hardening and softening phases of two-dimensional lattices. An alternative approach to the classical damage parameter approach is presented here. A semi-empirical model based on extreme value theory (EVT) is offered.
DOMESTIC COLD WATER CALCULATION-CHANGE HOUSE 3. DOCUMENT IDENTIFIER (Including Rev. No.) 4. REV. NO.
Theoretical and Applied Fracture Mechanics, 2001
The present study suggests that molecular and particle dynamics simulations can provide the basis... more The present study suggests that molecular and particle dynamics simulations can provide the basis for estimates of qualitative and quantitative aspects of damage in materials with inferior cohesive strength subjected to high strain rate loading. Two examples demonstrate that the traditional continuum models are of limited value in modeling of the class of considered problems.
Mechanics of Materials, 2008
The present study focuses on the plane strain problem of medium-to-high strain-rate loading of an... more The present study focuses on the plane strain problem of medium-to-high strain-rate loading of an idealized brittle material with random microstructure. The material is represented by an ensemble of “continuum particles” forming a two-dimensional geometrically and structurally disordered lattice. Performing repeated lattice simulations for different physical realizations of the microstructural statistics offers possibility to investigate universal trends in which the
Mathematics and Mechanics of Solids, 2014
A series of molecular-dynamics simulations of the classic Taylor impact test is performed by usin... more A series of molecular-dynamics simulations of the classic Taylor impact test is performed by using a flat-ended monocrystalline nanoscale projectile made of the Lennard-Jones two-dimensional solid. The nanoprojectile striking velocities range from 0.75 to 7 km/s. These atomistic simulations offer insight into nature of fragment distributions and evolution of state parameters. According to the simulation results, the cumulative distribution of fragment sizes in the course of this non-homogeneous fragmentation process for hypervelocity impacts appears to be well represented by the bimodal-exponential distribution commonly observed during high-energy uniform fragmentation events. For more moderate impact velocities, the cumulative distribution of fragment sizes, in addition to the bimodal-exponential part, exhibits a large-fragment tail. Temporal evolutions on instantaneous kinetic temperature, stress and strain invariants are presented and discussed. Scaling relations between temperat...
Journal of Engineering Mechanics, 1996
Brittle-Ductile Transition in Porous Rocks by Cap Model By Vlado A. Lubarda,1 Sreten Mastilovic,2... more Brittle-Ductile Transition in Porous Rocks by Cap Model By Vlado A. Lubarda,1 Sreten Mastilovic,2 and Jaroslaw Knap3 Abstract: A ... expo-nential) dependence on the hydrostatic stress was also used, eg, Bresler and Pister (1958), DiMaggio and Sandler (1971), and Simo et al. ...
The statistical damage model presented by the authors in the previous paper of this series is use... more The statistical damage model presented by the authors in the previous paper of this series is used to formulate analytical constitutive relations for the hardening and softening phases of two-dimensional lattices. A proper definition of the damage parameter for the softening is introduced. The results confirm that the analytical model can be used for the study of the softening phase and failure. This research offers a seminal basis for Damage Tolerance Principles technology standards of the commercial airplane industry.
International Journal of Damage Mechanics, 2008
The disordered 2D lattices are used extensively to study damage evolution and fracture of inhomog... more The disordered 2D lattices are used extensively to study damage evolution and fracture of inhomogeneous or multi-phase systems. The present note addresses their initial elastic response during dynamic loading. Namely, a transition from short-time values of modulus of elasticity and Poisson's ratio to respective long-time values, which is not accompanied by the corresponding change of stiffness tensor components. The study is performed on three 2D truss-type lattices. It is demonstrated that the difference between the two sets of elastic properties is a result of combining effects of the initial lateral inertia and the disorder of the system.
Theoretical and Applied Mechanics
The objective of the present review is twofold. First, it aims at highlighting some sigmoid and r... more The objective of the present review is twofold. First, it aims at highlighting some sigmoid and reverse-sigmoid response patterns observed recently in the course of simulations of the high-strain-rate loading of (mostly, quasibrittle) solids. Second, it aims at reviewing various properties of two models used frequently as curve fitting tools for nonlinear and saturable phenomena. These two models-inspired by the Hill and the Weibull cumulative distribution functions-are bounded by two horizontal asymptotes with a smooth transition between the baseline and the final saturation state, characterized by a non-negative (a non-positive) derivative at each point for the sigmoid (the reverse-sigmoid) shape. Although they were used primarily for data fitting because of their flexibility and effectiveness, these nonlinear models possess other properties useful for the analysis of the irreversible, nonlinear and far-from-equilibrium phenomena. The main features of these two models are systemat...
Latin American Journal of Solids and Structures
Molecular dynamics simulations of the ballistic Taylor test are used to explore correlation betwe... more Molecular dynamics simulations of the ballistic Taylor test are used to explore correlation between the largest fragment mass and the impact energy of a projectile as well as a set of selected state variables. Flat-ended, monocrystalline, nanoscale bars collide with a rigid wall with striking velocities ranging from 0.27 km/s to 60 km/s. The investigation emphasis is on two border regions of the emerging nonlinear phenomenological model identified with two transitions: the damage-fragmentation transition and the shattering transition. In between these two nonlinear regions, the maximum fragment mass is largely inversely proportional to the impact energy, and the maximum values of the pressure, temperature, and the square of the effective strain. A reverse-sigmoid phenomenological model is proposed to capture the unifying features of this nonlinear and saturable dependence. A crystallographic orientation dependence of the damage-fragmentation transition parameters is investigated.
Engineering Fracture Mechanics, Nov 1, 1994
ABSTRACT The paper presents a rate-type constitutive analysis of damage, applicable to brittle ma... more ABSTRACT The paper presents a rate-type constitutive analysis of damage, applicable to brittle materials whose elastic properties degrade during a deformation process. Different tensile and compressive material responses are modeled incorporating positive and negative projections of the stress or strain tensors. Proposed evolution laws for the rate of compliance tensors are consistent with some of the prominent features of brittle material response. A new structure of the damage surface is introduced for a more accurate account of the effects of the hydrostatic states of stress on the overall response. Derived rate constitutive equations provide the explicit representation of the tangent compliance tenser. The proposed model is applied to uniaxial tension and compression to illustrate nonlinear relationships between stress and longitudinal, lateral, and volumetric strains. The proposed model is compared with some of the existing theories.
Journal of Applied Mechanics, Sep 1, 1999
The objective of this study is to formulate a simple, rational model for estimates of the penetra... more The objective of this study is to formulate a simple, rational model for estimates of the penetration depth of rigid long rods through materials susceptible to microcracking. The proposed is based on the target resistance estimated using the particle dynamic simulations. All material parameters of the model can be identified and measured in laboratory. The accuracy of this simple model is found to be satisfactory.
The present study focuses on the kinetic and non-deterministic aspects of the brittle to quasi-br... more The present study focuses on the kinetic and non-deterministic aspects of the brittle to quasi-brittle transition. A solid is approximated by a lattice formed by the interacting 'continuum particles' and the evolution of damage is estimated using particle dynamics. The onset of transition is measured by the rate of the change of correlation length. The proposed method is illustrated on the examples of creep rupture, strain localization and dynamic expansion of a circular void in a 'brittle' plate. Sommario. Viene posta l'attenzione sugli aspetti cinetici e non deterministici della transizione dal comportamento fragile a quello quasi-fragile. Un solido viene approssimato da un reticolo formato da particelle interagenti e l'evoluzione del danno viene stimata tramite la dinamica delle particelle. L'inizio della transizione viene misurato tramite la variazione della lunghezza di correlazione. Il metodo proposto viene illustrato su esempi di rottura per 'creep', localizzazione della deformazione e l'espansione di un foro circolare in una piastra fragile.
International Journal of Damage Mechanics, 2010
This article illuminates some general features and provides elementary interpretations of the def... more This article illuminates some general features and provides elementary interpretations of the deformation, damage, and failure of brittle solids characterized by very low fracture energy. The dynamic response of these materials is determined to a large extent by stochastic and random factors. The investigation emphasis is on the moderate-to-extremely high rate range (10 s-1, 1 × 109 s-1), explored under practically identical in-plane stress conditions. The statistical approach is based on repeated particle dynamics simulations for different physical realizations of micromechanical disorder of a 2D brittle discrete system. The proposed strategy is computationally intensive, which necessitates simplicity of the laws governing the interparticular interaction. Based on the simulation results, an expression is proposed to model the mean tensile strength dependence on the strain rate. The linearity of the rate dependence of the stress-peak macroscopic response parameters is observed and d...