About

Craig Maloney is an Associate Professor and Associate Chair for Undergraduate Education in the Department of Mechanical and Industrial Engineering at Northeastern University College of Engineering. His research focuses on the theory, simulation, and modeling of disordered materials and soft matter systems. He has been recognized with the NSF CAREER Award in 2011 and is a member of professional societies including the American Physical Society, American Society of Mechanical Engineers, Materials Research Society, The Minerals Metals and Materials Society, and Society of Rheology. His work includes principal investigator roles on projects such as the NSF CAREER: Plasticity and Jamming and the NSF CDSE: A Data-driven Statistical Approach to Aging and Elasticity in Colloidal Glasses. Maloney's research has contributed to understanding avalanches, thresholds, diffusion in mesoscale amorphous plasticity, and the mechanical response of patchy rods, among other topics.

Research topics

• Chemistry
• Physics
• Materials science
• Crystallography
• Composite material
• Quantum mechanics
• Condensed matter physics
• Computer Science
• Atomic physics
• Statistics
• Mathematics
• Mathematical analysis
• Statistical physics
• Thermodynamics

Selected publications

• Anomalous Softness in Amorphous Matter in the Reversible Plastic Regime

  Physical Review Letters · 2025-04-11 · 1 citations

  articleSenior author

  We study an elastoplastic model of an amorphous solid subject to athermal quasistatic cyclic shear strain. We focus on cycling amplitudes in the so-called reversible-plastic regime where, after a transient, the system locks into a hysteretic limit cycle and returns to the same microscopic configuration after one or more strain cycles. We show that the ground state energy of the terminal limit cycle decreases with increasing cycling amplitude. In analogy to an annealed alloy or an aged colloidal glass, one would expect the states with lower energy to be mechanically harder and to require larger stresses and strains to trigger microscopic rearrangements. However, we show the opposite result: the systems with lower energy cycled at higher strain amplitude are mechanically softer and begin to exhibit plastic rearrangements at smaller stresses and strains within the cycle. We explain this anomaly quantitatively in terms of Eshelby inclusion theory where an inclusion is subjected to a particular negative stress value after it undergoes a yielding event. These results point the way toward measurements to be conducted in experiments and particle-based computer simulations on cyclically sheared amorphous solids.

  PublisherDOI

• A multi-body finite element model for hydrogel packings: linear response to shear

  Soft Matter · 2025-01-01

  articleOpen accessSenior author

  We study a multi-body finite element model of a packing of hydrogel particles using the Flory–Rehner constitutive law to model the deformation of the swollen polymer network.

  PublisherOA PDFDOI

• A multi-body finite element model for hydrogel packings: Linear response to shear

  arXiv (Cornell University) · 2024-07-19

  preprintOpen accessSenior author

  We study a multi-body finite element model of a packing of hydrogel particles using the Flory-Rehner constitutive law to model the deformation of the swollen polymer network. We show that while the dependence of the pressure, $Π$, on the effective volume fraction, $ϕ$, is virtually identical to a monolithic Flory material, the shear modulus, $μ$, behaves in a non-trivial way. $μ$ increases monotonically with $Π$ from zero and remains below about $80\%$ of the monolithic Flory value at the largest $Π$ we study here. The local shear strain in the particles has a large spatial variation. Local strains near the centers of the particles are all roughly equal to the applied shear strain, but the local strains near the contact facets are much smaller and depend on the orientation of the facet. We show that the slip between particles at the facets depends strongly on the orientation of the facet and is, on average, proportional to the component of the applied shear strain resolved onto the facet orientation. This slip screens the stress transmission and results in a reduction of the shear modulus relative to what one would obtain if the particles were welded together at the facet. Surprisingly, given the reduction in the shear modulus arising from the facet slip, and the spatial variations in the local shear strain inside the particles themselves, the deformation of the particle centroids is rather homogeneous with the strains of the Delaunay triangles having fluctuations of only order $\pm 5\%$. These results should open the way to construction of quantitative estimates of the shear modulus in highly compressed packings via mean-field, effective-medium type approaches.

  PublisherOA PDFDOI

• Mechanical excitation and marginal triggering during avalanches in sheared amorphous solids

  Physical review. E · 2023 · 6 citations

  Senior authorCorresponding
  • Materials science
  • Physics
  • Condensed matter physics

  We study plastic strain during individual avalanches in overdamped particle-scale molecular dynamics (MD) and mesoscale elastoplastic models (EPM) for amorphous solids sheared in the athermal quasistatic limit. We show that the spatial correlations in plastic activity exhibit a short length scale that grows as t^{3/4} in MD and ballistically in EPM, which is generated by mechanical excitation of nearby sites not necessarily close to their stability thresholds, and a longer lengthscale that grows diffusively for both models and is associated with remote marginally stable sites. These similarities in spatial correlations explain why simple EPMs accurately capture the size distribution of avalanches observed in MD, though the temporal profiles and dynamical critical exponents are quite different.

  PublisherOA PDFDOI

• Mapping out the glassy landscape of a mesoscopic elastoplastic model

  The Journal of Chemical Physics · 2022 · 27 citations

  • Materials science
  • Composite material
  • Condensed matter physics

  We develop a mesoscopic model to study the plastic behavior of an amorphous material under cyclic loading. The model is depinning-like and driven by a disordered thresholds dynamics that is coupled by long-range elastic interactions. We propose a simple protocol of "glass preparation" that allows us to mimic thermalization at high temperatures as well as aging at vanishing temperature. Various levels of glass stabilities (from brittle to ductile) can be achieved by tuning the aging duration. The aged glasses are then immersed into a quenched disorder landscape and serve as initial configurations for various protocols of mechanical loading by shearing. The dependence of the plastic behavior upon monotonous loading is recovered. The behavior under cyclic loading is studied for different ages and system sizes. The size and age dependence of the irreversibility transition is discussed. A thorough characterization of the disorder-landscape is achieved through the analysis of the transition graphs, which describe the plastic deformation pathways under athermal quasi-static shear. In particular, the analysis of the stability ranges of the strongly connected components of the transition graphs reveals the emergence of a phase-separation like process associated with the aging of the glass. Increasing the age and, hence, the stability of the initial glass results in a gradual break-up of the landscape of dynamically accessible stable states into three distinct regions: one region centered around the initially prepared glass phase and two additional regions characterized by well-separated ranges of positive and negative plastic strains, each of which is accessible only from the initial glass phase by passing through the stress peak in the forward and backward, respectively, shearing directions.

  PublisherOA PDFDOI

• Mechanical excitation and marginal triggering during avalanches in sheared amorphous solids

  arXiv (Cornell University) · 2022-02-11

  preprintOpen accessSenior author

  We study plastic strain during individual avalanches in overdamped particle-scale molecular dynamics (MD) and meso-scale elasto-plastic models (EPM) for amorphous solids sheared in the athermal quasi-static limit. We show that the spatial correlations in plastic activity exhibit a short lengthscale that grows as $t^{3/4}$ in MD and ballistically in EPM, and is generated by mechanical excitation of nearby sites not necessarily close to their stability thresholds, and a longer lengthscale that grows diffusively for both models and is associated with remote marginally stable sites. These similarities in spatial correlations explain why simple EPMs accurately capture the size distribution of avalanches observed in MD, though the temporal profiles and dynamical critical exponents are quite different.

  PublisherOA PDFDOI

• Anomalous softness in amorphous matter in the reversible plastic regime

  arXiv (Cornell University) · 2022-12-20 · 2 citations

  preprintOpen accessSenior author

  We study an integer automaton elasto-plastic model of an amorphous solid subject to cyclic shear of amplitude $Γ$. We focus on the reversible plastic regime at intermediate $Γ_0<Γ<Γ_y$, where, after a transient, the system settles into a periodic limit cycle with hysteretic, dissipative plastic events which repeat after an integer number of cycles. We study the plastic strain rate, $\frac{dε}{dγ}$, (where $γ$ is the applied strain and $ε$ is the plastic strain) during the terminal limit cycles and show that it consists of a creeping regime at low $γ$ with very low $\frac{dε}{dγ}$ followed by a sharp transition at a characteristic strain, $γ_*$, and stress, $σ_*$, to a flowing regime with higher $\frac{dε}{dγ}$. We show that while increasing $Γ$ above $Γ_0$ results in lower terminal ground state energy, $U_{\text{min}}$, and a correspondingly narrower distribution of stresses, it, surprisingly, results in lower $γ_*$, and $σ_*$. The stress distribution, $P(σ)$, also becomes skewed for $Γ>Γ_0$. That is, the systems in the RPR are anomalously soft and mechanically polarized. We relate this to an emergent characteristic feature in the stress distribution, $P(σ)$, at a value, $σ_0$, which is independent of $Γ$ and show that $σ_0$ implies a relation between the $Γ$ dependence of $σ_*$, $γ_*$, and the amplitude of plastic strain, $ε_p$. We show that the onset of hysteresis is characterized by a power-law scaling, indicative of a second order transition with $ε_p\propto (Γ-Γ_0)^{1.2\pm0.1}$. We argue that $σ_0$ and, correspondingly, the onset of the RPR at $Γ=Γ_0$, is simply set by the so-called Eshelby-stress. Furthermore, we show that cycling at $Γ_0$ results in a maximally hardened state.

  PublisherOA PDFDOI

• Yielding in an Integer Automaton Model for Amorphous Solids under Cyclic Shear

  Physical Review Letters · 2021 · 35 citations

  Senior authorCorresponding
  • Computer Science
  • Mathematics
  • Physics

  We present results on an automaton model of an amorphous solid under cyclic shear. After a transient, the steady state falls into one of three cases in order of increasing strain amplitude: (i) pure elastic behavior with no plastic activity, (ii) limit cycles where the state recurs after an integer period of strain cycles, and (iii) irreversible plasticity with longtime diffusion. The number of cycles N required for the system to reach a periodic orbit diverges as the amplitude approaches the yielding transition between regimes (ii) and (iii) from below, while the effective diffusivity D of the plastic strain field vanishes on approach from above. Both of these divergences can be described by a power law. We further show that the average period T of the limit cycles increases on approach to yielding.

  PublisherDOI

• Super-Flory scaling in compressed micro-gel packings

  Bulletin of the American Physical Society · 2020-03-04

  articleSenior author
  Publisher

• Driving and assembling magnetic particles with incoherent fields

  APS March Meeting Abstracts · 2019-01-01

  articleSenior author
  Publisher

Recent grants

• CAREER: Plasticity and Jamming

  NSF · $450k · 2011–2018

• Collaborative Research: A Data-Driven Statistical Approach to Aging and Elasticity in Colloidal Glasses

  NSF · $177k · 2017–2018

• Homogeneous Dislocation Nucleation

  NSF · $300k · 2011–2014

• Collaborative Research: A Data-Driven Statistical Approach to Aging and Elasticity in Colloidal Glasses

  NSF · $360k · 2012–2018

Frequent coauthors

• Anaël Lemaı̂tre

  Laboratoire Ville Mobilité Transport

  30 shared

• Damien Vandembroucq

  27 shared

• Mark O. Robbins

  16 shared

• Botond Tyukodi

  Babeș-Bolyai University

  15 shared

• Kamran Karimi

  National Centre for Nuclear Research

  12 shared

• Asad Hasan

  Missouri University of Science and Technology

  11 shared

• K. Michael Salerno

  Johns Hopkins University Applied Physics Laboratory

  9 shared

• Rasam Soheilian

  8 shared

Awards & honors

• 2011 NSF CAREER Award