Process systems engineering (PSE) has been an active research field for almost 50 years. Its major achievements include methodologies and tools to support process modeling, simulation and optimization (MSO). Mature, c...
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Process systems engineering (PSE) has been an active research field for almost 50 years. Its major achievements include methodologies and tools to support process modeling, simulation and optimization (MSO). Mature, commercially available technologies have been penetrating all fields of chemical engineering in academia as well as in industrial practice. MSO technologies have become a commodity, they are not a distinguishing feature of the PSE field any more. Consequently. PSE has to reassess and to reposition its future research agenda. Emphasis should be put on model-based applications in all PSE domains including product and process design, control and operations. Furthermore, systems thinking and systems problem solving have to be prioritized rather than the mere application of computational problem solving methods. This essay reflects on the past, present and future of PSE from an academic and industrial point of view. It redefines PSE as an active and future-proof research field which can play an active role in providing enabling technologies for product and process innovations in the chemical industries and beyond. (C) 2008 Elsevier Ltd. All rights reserved.
A quasianalytical method is presented for solving nonlinear, open-loop, optimal control problems. The approach combines a simple analytical, straightforward expansion from perturbation methods with powerful numerical ...
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A quasianalytical method is presented for solving nonlinear, open-loop, optimal control problems. The approach combines a simple analytical, straightforward expansion from perturbation methods with powerful numerical algorithms to solve a series of nonhomogeneous, linear, optimal control problems. In the past, the only recourse for solving such nonlinear problems relied almost exclusively on iterative numerical methods, whereas the asymptotic perturbation approach may produce accurate solutions to nonlinear problems without iteration.
This paper consists of two parts. The first one deals with the generation of an iterative algorithm to obtain an approximate solution of a linear equation of the second kind in a Banach space. This generation is based...
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This paper consists of two parts. The first one deals with the generation of an iterative algorithm to obtain an approximate solution of a linear equation of the second kind in a Banach space. This generation is based on a perturbed version of the geometric series theorem which, in particular, allows us to find a family of unisolvent linear Fredholm integral equations of the second kind, even when the associated linear operator has norm greater than or equal to 1. When we consider Fredholm equations of this type and linear Volterra integral equations of second kind, the numerical schemes obtained when appropriate Schauder bases are also introduced in the spaces where the equations operate, enable us to approximate their respective solutions iteratively. The second part of this work focuses on the design of a numerical method for solving an inverse problem associated with a linear equation of the second kind in a Banach space, a method which we apply to problems of parameter estimation related to the two classes of integral equations mentioned above. (c) 2023 The Author(s). Published by Elsevier B.V. on behalf of IMACS.
A linearized Euler solver for calculating unsteady flows in turbomachinery blade rows due to both incident gusts and vibratory blade motion is presented. Using the linearized Euler technique, one decomposes the flow i...
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The unsteady form of the full potential equation is solved in conservation form by an implicit method based on approximate factorization. At each time level, internal Newton iterations are performed to achieve time ac...
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We present simulations of 3 D dynamic fracture which suggest that a persistent elastic wave is generated in response to a localized perturbation of a propagating crack front, e.g., by a local heterogeneity of critical...
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We present simulations of 3 D dynamic fracture which suggest that a persistent elastic wave is generated in response to a localized perturbation of a propagating crack front, e.g., by a local heterogeneity of critical fracture energy. The wave propagates along the moving crack front and spreads, relative to its origin point on the fractured surface, at a speed slightly below the Rayleigh speed. The simulations were done using the spectral elastodynamic methodology of Geubelle and Rice (1995). They model failure by a displacement-weakening cohesive model, which corresponds in the singular crack limit to crack growth at a critical fracture energy. Confirmation that crack front waves with properties like in our simulation do exist has been provided by Ramanathan and Fisher (1997). Through a derivation based on the linearized perturbation analysis of dynamic singular tensile crack growth by Willis and Movchan (1995), those authors found by numerical evaluation that a transfer function thereby introduced has a simple pole at a certain omega/k ratio, corresponding to a non-dispersive wave. Further, we show that as a consequence of these persistent waves, when a crack grows through a region of small random fluctuations in fracture energy, the variances of both the local propagation velocity and the deformed slope of the crack Front increase, according to linearized perturbation theory. in direct proportion to distance of growth into the randomly heterogeneous region. That rate of disordering is more rapid than the growth of the variances with the logarithm of distance established by Perrin and Rice (1994) for a model elastodynamic fracture theory based on a scalar wave equation. That scalar case, which shows slowly decaying (as t(-1/2)) rather than persistent crack front waves, is analyzed here too. (C) 1998 Elsevier Science Ltd. All rights reserved.
This work utilizes mean-field self-consistent and full-field fast Fourier transform-based homogenizations to study the effective elastic behavior of several steels: three dual-phase (DP), DP 590, DP 980, and DP 1180, ...
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This work utilizes mean-field self-consistent and full-field fast Fourier transform-based homogenizations to study the effective elastic behavior of several steels: three dual-phase (DP), DP 590, DP 980, and DP 1180, and one martensitic (MS), MS 1700. Crystallographic textures and phase fractions of these steels are characterized using electron microscopy along with electron-backscattered diffraction to initialize the models. A comprehensive set of Young's modulus and Poisson's ratio data, measured at the ambient temperature as a function of orientation with respect to the rolling direction for each steel sheet, is used to calibrate and validate the models. The calibration of the models enabled us to estimate the single crystal elastic constants for both the martensitic phase and ferrite, while calculating the orientation dependent effective properties. Half of the data was used in the calibration. Subsequent predictions of the orientation dependent effective elastic properties for the remaining data verified that the estimated single crystal properties are reliable. As the steels exhibit a different level of anisotropy in their effective behavior, good predictions allowed us to discuss the role of texture, grain structure, phase fraction and distribution on the effective properties. The results of this work represent a significant incentive to introduce elastic anisotropy in numerical tools for simulating metal forming processes of dual-phase steels, in particular those processes involving springback, using the texture informed crystal mechanics-based models to more accurately estimate the effective elastic properties required by such simulations.
A computational procedure for the analysis of loads due to steady and oscillatory control surface deflections is presented. The numerical algorithm is based on a time accurate solution of the transonic full potential ...
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A computational procedure for the analysis of loads due to steady and oscillatory control surface deflections is presented. The numerical algorithm is based on a time accurate solution of the transonic full potential equation in a body-fitted coordinate system. Control surface deflection and motion are modeled using an equivalent body velocity that circumvents the need for generating time-dependent grids and interpolation between planes and discontinuity. Viscous effects, including mild separation, are modeled using an interactive inverse boundary layer and the transpiration velocity approach. numerical results are presented for a three-dimensional transport aircraft wing with supercritical sections, for control surfaces located at the trailing edge and the leading edge, for steady as well as oscillatory deflections. Results are compared with experimental data as well as with linear theory.
Following;(a) the observation that micro-void and micro-crack driven failure mechanisms co-exist in metallic alloys and (b) the two damage state variable definition given in Chaboche et al. (2006), two coupled porous ...
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Following;(a) the observation that micro-void and micro-crack driven failure mechanisms co-exist in metallic alloys and (b) the two damage state variable definition given in Chaboche et al. (2006), two coupled porous plasticity and continuum damage mechanics approaches to assess temperature driven ductile-to-brittle transition fracture in ferritic steels have been developed. Based on hypo-elastic formulation of Gurson-Tvergaard-Needleman (GTN) thermoplasticity to account for ductile failure following void growth, continuum damage mechanics formalism have been coupled in order to account for micro-crack driven brittle fracture. Keeping GTN thermoplasticity as a basis for ductile fracture, Leckie-Hayhurst creep rupture criterion has been modified and proposed to account for brittle damage, thus cleavage, in the first model. The second approach, which is proposed following the motivation that plasticity exists in and below the lower transition region, replaces Leckie-Hayhurst model with plasticity driven damage evolution law of Lemaitre et al. (2000). Unlike commonly used cleavage models such as Ritchie et al. (1973) and Beremin (1983), both of the proposed models have been aimed to take into account blended effects of micro-voids and micro-cracks in order to capture energy dissipation and softening accompanying and prior to brittle fracture. numerical implementation has been done for ABAQUS/Explicit and uses staggered solution based on plastic flow-damage correction structure, while its validation has been performed modeling Small Punch Fracture Experiments for P91 ferritic steel, published by Turba et al. (2011). (C) 2015 Elsevier Ltd. All rights reserved.
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