17 results on '"Duarte, Camilo A."'
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2. An Eulerian crystal plasticity framework for modeling large anisotropic deformations in energetic materials under shocks.
- Author
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Sen, Oishik, Duarte, Camilo A., Rai, Nirmal Kumar, Koslowski, Marisol, and Udaykumar, H. S.
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DEFORMATIONS (Mechanics) , *CRYSTAL orientation , *CRYSTALS , *POROUS materials , *ELASTOPLASTICITY , *SHEARING force - Abstract
This paper demonstrates a novel Eulerian computational framework for modeling anisotropic elastoplastic deformations of organic crystalline energetic materials (EM) under shocks. While Eulerian formulations are advantageous for handling large deformations, constitutive laws in such formulations have been limited to isotropic elastoplastic models, which may not fully capture the shock response of crystalline EM. The present Eulerian framework for high-strain rates, large deformation material dynamics of EM incorporates anisotropic isochoric elasticity via a hypo-elastic constitutive law and visco-plastic single-crystal models. The calculations are validated against atomistic calculations and experimental data and benchmarked against Lagrangian (finite element) crystal plasticity computations for shock-propagation in a monoclinic organic crystal, octahydro-1,3,5,7-tetranitro-1,3,5,7 tetrazocine (β-HMX). The Cauchy stress components and the resolved shear stresses calculated using the present Eulerian approach are shown to be in good agreement with the Lagrangian computations for different crystal orientations. The Eulerian framework is then used for computations of shock-induced inert void collapse in β-HMX to study the effects of crystal orientations on hotspot formation under different loading intensities. The computations show that the hotspot temperature distributions and the collapse profiles are sensitive to the crystal orientations at lower impact velocities (viz., 500 m/s); when the impact velocity is increased to 1000 m/s, the collapse is predominantly hydrodynamic and the role of anisotropy is modest. The present methodology will be useful to simulate energy localization in shocked porous energetic material microstructures and other situations where large deformations of single and polycrystals govern the thermomechanical response. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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3. P- 17 LIVER TESTS ABNORMALITIES AS PROGNOSTIC MARKERS OF DEATH IN PATIENTS HOSPITALISED BY COVID-19. A COHORT STUDY
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Rodriguez-Gutierrez, Andrés Fernando, Moreno, Sergio Mauricio, and Duarte, Camilo Andrés
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- 2024
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4. Failure analysis of the wall tubes of a water-tube boiler
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Duarte, Camilo A., Espejo, Edgar, and Martinez, Juan Carlos
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- 2017
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5. Continuum and molecular dynamics simulations of pore collapse in shocked β-tetramethylene tetranitramine (β-HMX) single crystals.
- Author
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Duarte, Camilo A., Li, Chunyu, Hamilton, Brenden W., Strachan, Alejandro, and Koslowski, Marisol
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SINGLE crystals , *MOLECULAR dynamics , *TEMPERATURE distribution , *MATERIAL plasticity , *VISCOPLASTICITY , *HIGH temperatures - Abstract
The collapse of pores plays an essential role in the shock initiation of high energy (HE) materials. When these materials are subjected to shock loading, energy is localized in hot-spots due to various mechanisms, including void collapse. Depending on the void size and shock strength, the resulting hot-spots may quench or evolve into a self-sustained deflagration wave that consequently can cause detonation. We compare finite element (FE) and non-reactive molecular dynamic (MD) simulations to study the formation of hot-spots during the collapse of an 80 nm size void in a β -tetramethylene tetranitramine energetic crystal. The crystal is shocked normal to the crystallographic plane (010) , applying boundary velocities of 0.5 km/s, 1.0 km/s, and 2.0 km/s. The FE simulations capture the transition from viscoelastic collapse for relatively weak shocks to a hydrodynamic regime, the overall temperature distributions, especially at scales relevant for the initiation of HE materials, and the rate of pore collapse. A detailed comparison of velocity and temperature fields shows that the MD simulations exhibit more localization of plastic deformation, which results in higher temperature spikes but localized to small volumes. The void collapse rate and temperature field are strongly dependent on the plasticity model in the FE results, and we quantify these effects. [ABSTRACT FROM AUTHOR]
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- 2021
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6. Suppression of Nonlinear Rotary Slosh Dynamics Using the SLS Adaptive Augmenting Control System Demonstration on a Quadcopter Testbed
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Pei, Jing, Puetz, Andrew, Duarte, Camilo, Miller, Luke, and Rothhaar, Paul
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Spacecraft Design, Testing And Performance - Abstract
Liquid propellant makes up a significant portion of the total weight for large launch vehicles such as Saturn V, Space Shuttle, and the Space Launch System. Careful attention must be given to the influence of fuel slosh motion on the stability of the vehicle in the design of the Flight Control System (FCS). Historically, there have been instances where a poorly designed FCS in addition to a lack of passive damping have caused the slosh mass to drive the launch vehicle unstable. The dynamics behind controlling a quadcopter/hanging mass configuration is analogous to that of controlling the attitude of a rocket with a single propellant tank. The quadcopter/hanging mass configuration offers a reasonably accurate platform for assessing the real-time effectiveness of the SLS Adaptive Augmenting Controller in suppressing slosh instability. Flight test experiments were carried out at the NASA Langley Research Center's Autonomy Incubator. During both simulation and flight test, the hanging mass was intentionally made unstable and the adaptive algorithm successfully suppressed the instability as expected.
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- 2019
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7. Dynamic fracture and frictional heating due to periodic excitation in energetic materials.
- Author
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Duarte, Camilo A., Kohler, Rachel, and Koslowski, Marisol
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FRACTURE mechanics , *FRICTION , *HEATING , *EXCITATION equipment , *MICROSTRUCTURE , *ENERGY dissipation - Abstract
Mechanical stimulus may lead to localized temperature increase due to the concentration of energy dissipation at microstructural features. Mechanically induced heating occurs, for example, when materials are subjected to periodic excitation. This is a particular concern in energetic materials where ignition may start a deflagration. In this study, finite element simulations are performed on a single β -HMX particle in a polymer matrix subjected to mechanical periodic excitation. Different initial defects, such as cracks and interface debonding, are included to control the location of hot-spots nucleation. The model accounts for damage evolution and heat generation due to friction at cracks. The results indicate that hot-spots nucleate preferentially at the particle/binder interface, and therefore, the temperature rate is higher when the particle is initially debonded than when it is perfectly attached to the polymer. [ABSTRACT FROM AUTHOR]
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- 2018
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8. Deep $\mathcal{L}^1$ Stochastic Optimal Control Policies for Planetary Soft-landing
- Author
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Pereira, Marcus A., Duarte, Camilo A., Exarchos, Ioannis, and Theodorou, Evangelos A.
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FOS: Computer and information sciences ,Computer Science - Machine Learning ,Artificial Intelligence (cs.AI) ,Computer Science - Artificial Intelligence ,FOS: Electrical engineering, electronic engineering, information engineering ,Systems and Control (eess.SY) ,Electrical Engineering and Systems Science - Systems and Control ,Machine Learning (cs.LG) - Abstract
In this paper, we introduce a novel deep learning based solution to the Powered-Descent Guidance (PDG) problem, grounded in principles of nonlinear Stochastic Optimal Control (SOC) and Feynman-Kac theory. Our algorithm solves the PDG problem by framing it as an $\mathcal{L}^1$ SOC problem for minimum fuel consumption. Additionally, it can handle practically useful control constraints, nonlinear dynamics and enforces state constraints as soft-constraints. This is achieved by building off of recent work on deep Forward-Backward Stochastic Differential Equations (FBSDEs) and differentiable non-convex optimization neural-network layers based on stochastic search. In contrast to previous approaches, our algorithm does not require convexification of the constraints or linearization of the dynamics and is empirically shown to be robust to stochastic disturbances and the initial position of the spacecraft. After training offline, our controller can be activated once the spacecraft is within a pre-specified radius of the landing zone and at a pre-specified altitude i.e., the base of an inverted cone with the tip at the landing zone. We demonstrate empirically that our controller can successfully and safely land all trajectories initialized at the base of this cone while minimizing fuel consumption.
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- 2021
9. Phase Contrast X‐Ray Imaging of the Collapse of an Engineered Void in Single‐Crystal HMX.
- Author
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Blum‐Sorensen, Christian J., Duarte, Camilo A., Drake, Jonathan D., Kerschen, Nicholas E., Fezzaa, Kamel, Koslowski, Marisol, Chen, Weinong W., and Son, Steven F.
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X-ray imaging ,SINGLE crystals ,NORMALIZED measures ,GOVERNMENT laboratories ,EXPLOSIVES ,DETONATORS - Abstract
Imaging the collapse of a single void that creates a hot spot initiation site in an otherwise defect‐free explosive is challenging given the spatial and temporal scales involved in explosive systems. This work presents our attempt to examine a single hot spot mode (void collapse) in single‐crystal octahydro‐l,3,5,7‐tetranitro‐l,3,5,7‐tetrazocine (HMX) embedded in Sylgard. The hot spot heating mechanisms involved with pore collapse include adiabatic heating, jetting, and viscoplastic dissipation. Quantifying the dynamics of a pore collapse is a crucial step to understanding which mechanisms dominate during ignition events. Our experiments were conducted with a single‐stage, light‐gas gun at Argonne National Laboratory's Advanced Photon Source, applying the phase contrast imaging technique while collecting high‐speed video. The details of HMX single crystal production, defect (pore) engineering, and sample construction, along with experimental results are presented here. These results demonstrate that detailed collapse dynamics can be obtained from homogeneous, single‐crystal explosives with this approach. Qualitative comparisons are made with simulation data which show good agreement in the transition between a quasi‐symmetric pore collapse and an asymmetric collapse with jetting across the pore as measured with normalized pore area and pore circularity. [ABSTRACT FROM AUTHOR]
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- 2022
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10. Effect of initial damage variability on hot-spot nucleation in energetic materials.
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Duarte, Camilo A., Grilli, Nicolò, and Koslowski, Marisol
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NUCLEATION , *MICROSTRUCTURE , *CRACK propagation (Fracture mechanics) , *HEAT transfer , *FRACTURE mechanics - Abstract
Mechanical insult may be able to produce chemical transformations in solids when the energy is released in highly localized regions. This phenomenon is responsible for the nucleation of hot-spots that are responsible for ignition of energetic materials. The concentration of energy at microstructural defects leads to the probabilistic nature of ignition. The effect of the microstructure of the energetic particles, specifically the influence of the initial crack distribution on the sensitivity to ignition, is studied for a particle embedded in a polymeric matrix at impact velocities 100 m/s and 400 m/s with finite element simulations that couple fracture dynamics and heat transport. A phase field damage model that includes heat sources due to frictional heating at the crack surfaces and heat dissipation during crack propagation is developed and verified. These heat sources are compared and, in the range of impact velocities studied, heat generation due to friction is more important than dissipation due to crack propagation. Hot-spots nucleated at 100 m/s do not reach the critical temperature while conditions consistent with the Lee-Tarver criterion for ignition are observed at 400 m/s impact velocity. The variability observed due to the stochasticity of the initial crack distribution is studied and it increases with a higher impact velocity. In particular, regions of high temperature develop close to cracks intersecting the particle polymer interface. Therefore, controlling the surface quality of the energetic particles may lead to a reduction on the sensitivity uncertainty in polymer-bonded explosives. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
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11. Adaptive Risk Sensitive Model Predictive Control with Stochastic Search
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Wang, Ziyi, So, Oswin, Lee, Keuntaek, Duarte, Camilo A., and Theodorou, Evangelos A.
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FOS: Computer and information sciences ,Computer Science - Robotics ,Optimization and Control (math.OC) ,FOS: Mathematics ,Robotics (cs.RO) ,Mathematics - Optimization and Control - Abstract
We present a general framework for optimizing the Conditional Value-at-Risk for dynamical systems using stochastic search. The framework is capable of handling the uncertainty from the initial condition, stochastic dynamics, and uncertain parameters in the model. The algorithm is compared against a risk-sensitive distributional reinforcement learning framework and demonstrates outperformance on a pendulum and cartpole with stochastic dynamics. We also showcase the applicability of the framework to robotics as an adaptive risk-sensitive controller by optimizing with respect to the fully nonlinear belief provided by a particle filter on a pendulum, cartpole, and quadcopter in simulation.
- Published
- 2020
12. Space-mapping optimization of lossy coupled-resonator filters exploiting rational approximation models
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Gómez-Duarte, Camilo
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Maquinaria eléctrica ,Guías de ondas ,Ingeniería ,Lossy filter ,Space mapping ,Filter Optimization ,Resonadores eléctricos ,Filtros electrónicos ,Substrate Integrated Waveguide - Abstract
Space mapping is a useful method for optimization of microwave structures using full-wave electromagnetic simulations. This paper proposes an efficient and robust implementation of the space mapping algorithm for lossy coupled resonator filters. The method makes use of a circuital-parameter-based coarse model that presents numerous advantages over traditional coarse model such as 1) the ability to model cross-coupling and losses; 2) direct correction/calibration of the coarse model in order to include parasitic interactions extracted from the fine model; and 3) improved parameter extraction (PE) through estimation of rational polynomials. A numerical examples of the proposed methodology corresponding to a 4th order substrate integrated waveguide (SIW) filter with transmission zeros is presented in order to demonstrate the performance and versatility of the method. Magíster en Ingeniería Electrónica y de Computadores Maestría
- Published
- 2018
13. Void Collapse in Shocked β ‐HMX Single Crystals: Simulations and Experiments.
- Author
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Duarte, Camilo A., Hamed, Ahmed, Drake, Jonathan D., Sorensen, Christian J., Son, Steven F., Chen, Weynong W., and Koslowski, Marisol
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SINGLE crystals ,MECHANICAL shock measurement ,VOIDS (Crystallography) ,MECHANICAL shock ,MORPHOLOGY - Abstract
Heat generation in the vicinity of a void during shock compression plays a key role in the initiation of energetic materials. The shock response of a single β ‐HMX crystal with a single void is studied with simulations that include plasticity and heat transport. The numerical results are validated with an experiment in which a 500 μ m void is machined in an HMX single crystal and impacted. Experiments and simulations of the dynamical evolution of the morphology of the void during the collapse and the rate of the area are in very good agreement for weak shocks. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
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14. Erratum: Continuum and molecular dynamics simulations of pore collapse in shocked β-tetramethylene tetranitramine (β-HMX) single crystals. [J. Appl. Phys. 129, 015904 (2021)].
- Author
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Duarte, Camilo A., Li, Chunyu, Hamilton, Brenden W., Strachan, Alejandro, and Koslowski, Marisol
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MOLECULAR dynamics , *SINGLE crystals , *DISLOCATION density - Abstract
This error does not alter the results, discussion, and conclusion because the correct values were used in the simulations. Erratum: Continuum and molecular dynamics simulations of pore collapse in shocked -tetramethylene tetranitramine ( -HMX) single crystals. There is an error in the density of mobile dislocations reported in the first paragraph in Sec. [Extracted from the article]
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- 2021
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15. Digital Frequency Modulation Spectroscopy to Interrogate Passive Resonant Devices.
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Diaz Bautista, Luis Carlos, Gomez-Duarte, Camilo, Pulido Suarez, David Sebastian, Velasquez Suarez, Sebastian, Bohorquez Reyes, Juan Carlos, Segura-Quijano, Fredy Enrique, and Pena Traslavina, Nestor Misael
- Abstract
This paper presents the design and implementation of a passive resonant sensor interrogator. The interrogator implements frequency modulation spectroscopy (FMS) using a digital modulation technique, such as binary frequency shift keying. The implementation of a digital modulation technique allows for accurate interrogation of high-Q resonant sensors in the microwave spectrum. FMS is capable of detecting the absorption and dispersion curves of a passive resonant sensor; consequently, the resonance frequency is obtained. The interrogator is successfully simulated using Mathworks MATLAB and implemented in a software-defined radio platform. The interrogation scheme was tested on a resonant cavity filter with a resonance frequency of 589.85 MHz. The interrogator achieved the resonance detection with an error of 0.025%. [ABSTRACT FROM PUBLISHER]
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- 2017
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16. Dynamic fracture and hot-spot modeling in energetic composites.
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Grilli, Nicolò, Duarte, Camilo A., and Koslowski, Marisol
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DELTA-functional potential , *CRACK propagation (Fracture mechanics) , *POTENTIAL well , *FINITE square well , *QUANTUM confinement effects , *POTENTIAL barrier - Abstract
Defects such as cracks, pores, and particle-matrix interface debonding affect the sensitivity of energetic materials by reducing the time-to-ignition and the threshold pressure to initiate an explosion. Frictional sliding of preexisting cracks is considered to be one of the most important causes of localized heating. Therefore, understanding the dynamic fracture of crystalline energetic materials is of extreme importance to assess the reliability and safety of polymer-bonded explosives. Phase field damage model simulations, based on the regularization of the crack surface as a diffuse delta function, are used to describe crack propagation in cyclotetramethylene-tetranitramine crystals embedded in a Sylgard matrix. A thermal transport model that includes heat generation by friction at crack interfaces is coupled to the solution of crack propagation. 2D and 3D dynamic compression simulations are performed with different boundary velocities and initial distributions of cracks and interface defects to understand their effect on crack propagation and heat generation. It is found that, at an impact velocity of 400 m/s, localized damage at the particle-binder interface is of key importance and that the sample reaches temperatures high enough to create a hot-spot that will lead to ignition. At an impact velocity of 10 m/s, preexisting cracks advanced inside the particle, but the increase of temperature will not cause ignition. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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17. A Practical Design Approach to Custom mmWave SMT Packages.
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GOMEZ-DUARTE, CAMILO, KAHTAN, BENJAMIN, and VAISMAN, AARON
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DIRECT currents , *5G networks , *INTEGRATED circuits , *ELECTRIC industries , *SURFACE mount technology - Abstract
The article offers information on ingredients which can be used for developing customized Surface-mo that will ultimately achieve good electrical performance from direct current (dc) to 50 GHz. It mentions that the advent of fifth generation (5G) has brought about an increase in development of integrated circuits (ICs) to meet the requirements forhigh-frequency applications.
- Published
- 2019
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