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Supplementary neutron-flux calculations for the ORNL Pool Critical Assembly Pressure Vessel Facility

Description: A three-dimensional Monte Carlo calculation using the MORSE code was performed to validate a procedure previously adopted in the ORNL discrete ordinate analysis of measurements made in the ORNL Pool Critical Assembly Pressure Vessel Facility. The results of these flux calculations agree, within statistical undertainties of about 5%, with those obtained from a discrete ordinate analysis employing the same procedure. This study therefore concludes that the procedure for combining several one- and… more
Date: January 1, 1982
Creator: Maudlin, P. J. & Maerker, R. E.
Partner: UNT Libraries Government Documents Department
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Surface density representation of critical configurations of U(5)O/sub 2/ planar and linear arrays

Description: A criticality data base for planar and linear arrays of low enriched damp uranium dioxide powder contained in cylindrical units is generated with the Monte Carlo criticality program KENO-IV. This information is correlated with the Limiting Surface Density model, sigma(m) = c/sub 2/(m/sub 0/-m), refining the bulky KENO data base into a simple table of correlation constants c/sub 2/ and m/sub 0/. A solid angle representation of the KENO data base is provided. The solid angles were analytically de… more
Date: June 1, 1980
Creator: Maudlin, P.J. & Thomas, J.T.
Partner: UNT Libraries Government Documents Department
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Fuel models and results from the TRAC-PF1/MIMAS TMI-2 accident calculation

Description: A brief description of several fuel models used in the TRAC-PF1/MIMAS analysis of the TMI-2 accident is presented, and some of the significant fuel-rod behavior results from this analysis are given. Peak fuel-rod temperatures, oxidation heat production, and embrittlement and failure behavior calculated for the TMI-2 accident are discussed. Other aspects of fuel behavior, such as cladding ballooning and fuel-cladding eutectic formation, were found not to significantly affect the accident progres… more
Date: January 1, 1983
Creator: Schwegler, E.C. & Maudlin, P.J.
Partner: UNT Libraries Government Documents Department
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Thermal-hydraulic differential sensitivity theory. [LMFBR]

Description: Differential sensitivity theory is applied to a nonlinear, three-dimensional space- and time-dependent description of the thermal-hydraulic conservation equations. The resulting sensitivity equations, which are derived using adjoint functions, can be readily utilized for input parameter sensitivity analysis of large or long-running thermal-hydraulic computer codes without any prior engineering judgement. The procedure for applying this sensitivity theory is illustrated using several classical a… more
Date: September 1, 1981
Creator: Maudlin, P.J.; Parks, C.V. & Weber, C.F.
Partner: UNT Libraries Government Documents Department
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Application of differential sensitivity theory to transients with scram. [LMFBR]

Description: Differential sensitivity theory (DST) based on adjoint functions has been applied to various reactor safety problems. The most comprehensive application of DST sensitivity analysis has addressed the coupled thermal-hydraulic equations of the MELT-III fast reactor safety code, where a power ramp was imposed to eliminate the neutron point kinetics equations. In extending the above work to include realistic neutronic coupling, a DST procedure was developed for dealing with parameter discontinuitie… more
Date: January 1, 1980
Creator: Parks, C.V.; Maudlin, P.J. & Weber, C.F.
Partner: UNT Libraries Government Documents Department
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Differential sensitivity theory applied to movement of maxima responses. [LMFBR]

Description: Differential sensitivity theory (DST) is a recently developed methodology to evaluate response derivatives dR/d..cap alpha.. by using adjoint functions which correspond to the differentiated (with respect to an arbitrary parameter ..cap alpha..) linear or nonlinear physical system of equations. However, for many problems, where responses of importance are local maxima such as peak temperature, power, or heat flux, changes in the phase space location of the peak itself are of interest. This summ… more
Date: January 1, 1981
Creator: Maudlin, P. J.; Parks, C. V. & Cacuci, D. G.
Partner: UNT Libraries Government Documents Department
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Investigation of accuracy and computation time of a hierarchy of growth rate definitions. [LMFBR; PuO/sub 2/-UO/sub 2/]

Description: A numerical illustration of the hierarchy of four logically different procedures for the calculation of the asymptotic growth of fast breeder fuel is presented. Each hierarchy level is analyzed in terms of accuracy and computational effort. Using the first procedure as reference, the fourth procedure, which incorporates the isotopic breeding worths, w vector*, requires a minimum amount of effort with a negligible decrease in accuracy.
Date: July 1, 1977
Creator: Maudlin, P. J.; Borg, R. C. & Ott, K. O.
Partner: UNT Libraries Government Documents Department
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Evolution of plastic anisotropy for high-strain-rate computations

Description: A model for anisotropic material strength, and for changes in the anisotropy due to plastic strain, is described. This model has been developed for use in high-rate, explicit, Lagrangian multidimensional continuum-mechanics codes. The model handles anisotropies in single-phase materials, in particular the anisotropies due to crystallographic texture--preferred orientations of the single-crystal grains. Textural anisotropies, and the changes in these anisotropies, depend overwhelmingly no the cr… more
Date: December 1, 1994
Creator: Schiferl, S. K. & Maudlin, P. J.
Partner: UNT Libraries Government Documents Department
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Metal cutting simulation of 4340 steel using an accurate mechanical description of meterial strength and fracture

Description: Strength and fracture constitutive relationships containing strain rate dependence and thermal softening are important for accurate simulation of metal cutting. The mechanical behavior of a hardened 4340 steel was characterized using the von Mises yield function, the Mechanical Threshold Stress model and the Johnson- Cook fracture model. This constitutive description was implemented into the explicit Lagrangian FEM continuum-mechanics code EPIC, and orthogonal plane-strain metal cutting calcula… more
Date: September 1, 1996
Creator: Maudlin, P.J. & Stout, M.G.
Partner: UNT Libraries Government Documents Department
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AUTOMATIC DIFFERENTIATION OF AN EULERIAN HYDROCODE

Description: Automatic differentiation (AD) is applied to a two-dimensional Eulerian hydrodynamics computer code (hydrocode) to provide gradients that will be used for design optimization and uncertainty analysis. We examine AD in both the forward and adjoint (reverse) mode using Automatic Differentiation of Fortran (ADIFOR, version 3.0). Setup time, accuracy, and run times are described for three problems. The test set consists of a one-dimensional shock-propagation problem, a two-dimensional metal-jet-for… more
Date: November 1, 2000
Creator: HENNINGER, R.; CARLE, A. & MAUDLIN, P.
Partner: UNT Libraries Government Documents Department
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HYDROCODE SENSITIVITIES BY MEANS OF AUTOMATIC DIFFERENTIATION

Description: The purpose of this project has been to provide sensitivities of results from an Eulerian hydrodynamics computer code (hydrocode) for use in design-optimization and uncertainty analyses. We began by applying an equation-based sensitivity technique used successfully in the early eighties that was applied to reactor-safety thermal-hydraulics problems, which is called Differential Sensitivity Theory (DST). The methodology is as follows: the system of partial differential equations (the forward or … more
Date: January 1, 2001
Creator: HENNINGER, R.; CARLE, A. & MAUDLIN, P.
Partner: UNT Libraries Government Documents Department
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Differential Sensitivity Theory applied to the MESA code for high pressure interactions

Description: A technique called Differential Sensitivity Theory (DST) is applied to the system of equations solved by the MESA hydrocode. DST uses adjoint techniques to determine exact sensitivity derivatives, i.e., if R is a calculational result of interest (response R) and {alpha}{sub i} is a calculational input (parameter {alpha}{sub i}), then {partial_derivative}R/{partial_derivative}{alpha}{sub i} is defined as the sensitivity. The advantage of using DST is that for an n-parameter problem all n sensiti… more
Date: July 1, 1993
Creator: Maudlin, P. J.; Henninger, R. J. & Harstad, E. N.
Partner: UNT Libraries Government Documents Department
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Implementation and assessment of the mechanical-threshold-stress model using the EPIC2 and PINON computer codes

Description: A flow-stress constitutive model based on dislocation mechanics has been implemented in the EPIC2 and PINON continuum mechanics modes. This model provides a better understanding of the plastic deformation process for ductile materials by using an internal state variable called the mechanical threshold stress. This kinematic quantity tracks the evolution of the material's microstructure along some arbitrary strain, strain-rate, and temperature-dependent path using a differential form that balanc… more
Date: September 1, 1990
Creator: Maudlin, P. J.; Davidson, R. F. & Henninger, R. J.
Partner: UNT Libraries Government Documents Department
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Effects of anisotropy on dynamic tensile behavior

Description: A stability analysis for an anisotropic stretching rod is presented. We consider the particular case of a rapidly stretching titanium jet using a continuum code to examine anisotropic plastic response in the finite-neck regime. It was found that the classical analysis (yield strength is inversely proportional to stability) is insufficient; anisotropic jets can be more or less stable than their maximum or minimum yield strengths, depending on initial perturbations and the orientation of the anis… more
Date: January 1, 1991
Creator: Schifert, S. K.; Davidson, R. F. & Maudlin, P. J.
Partner: UNT Libraries Government Documents Department
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Modeling anisotropic plasticity: Eulerian hydrocode applications of high strain-rate deformation processes

Description: Previously developed constitutive models and solution algorithms for anisotropic elastoplastic material strength are implemented in the two-dimensional MESA hydrodynamics code. Quadratic yield functions fitted from polycrystal simulations for a metallic hexagonal-close-packed structure are utilized. An associative flow strength formulation incorporating these yield functions is solved using a geometric normal return method. A stretching rod problem is selected to investigate the effects of mate… more
Date: May 1, 1997
Creator: Clancy, S. P.; Burkett, M. W. & Maudlin, P. J.
Partner: UNT Libraries Government Documents Department
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On the modeling of the Taylor cylinder impact test for orthotropic textured materials: Calculations and experiments

Description: Taylor impact tests using specimens cut from a rolled plate of Ta were conducted. The Ta was well-characterized in terms of flow stress and crystallographic texture. A piece-wise yield surface was interrogated from this orthotropic texture, and used in EPIC-95 3D simulations of the Taylor test. Good agreement was realized between the calculations and the post-test geometries in terms of major and minor side profiles and impact-interface footprints.
Date: April 1, 1997
Creator: Maudlin, P.J.; Bingert, J.F. & House, J.W.
Partner: UNT Libraries Government Documents Department
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Differential sensitivity theory applied to the MESA2D code for multi-material problems

Description: The technique called Differential Sensitivity Theory (DST) is extended to the multi-component system of equations solved by the MESA2D hydrocode. DST uses adjoint techniques to determine exact sensitivity derivatives, i.e., if R is a calculation result of interest (response R) and {alpha}{sub i} is a calculation input (parameter {alpha}{sub i}), then {partial_derivative}R/{partial_derivative}{alpha}{sub i} is defined as the sensitivity. The advantage of using DST is that for an n-parameter prob… more
Date: September 1995
Creator: Henninger, R. J.; Maudlin, P. J. & Harstad, E. N.
Partner: UNT Libraries Government Documents Department
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An application of multisurface plasticity theory: Yield surfaces of textured materials

Description: Directionally dependent descriptions of the yield behavior of metals as determined by polycrystal plasticity computations are discrete in nature and, in principle, are available for use in large-scale application calculations employing multi-dimensional continuum mechanics codes. However, the practical side of using such detailed yield surfaces in application calculations contains some challenges in terms of algorithm development and computational efficiency. Discrete representations of yield a… more
Date: September 1, 1995
Creator: Maudlin, P.J.; Wright, S.I. & Kocks, U.F.
Partner: UNT Libraries Government Documents Department
open access

Modeling anisotropic plasticity: Eulerian hydrocode applications of high strain-rate deformation processes

Description: Previously developed constitutive models and solution algorithms for anisotropic elastoplastic material strength are implemented in the two dimensional MESA hydrodynamics code. Quadratic yield functions fitted from polycrystal simulations for a metallic hexagonal-close-packed structure are utilized. An associative flow strength formulation incorporating these yield functions is solved using a geometric normal return method. A stretching rod problem is selected to investigate the effects of mate… more
Date: February 1, 1998
Creator: Clancy, S. P.; Burkett, M. W. & Maudlin, P. J.
Partner: UNT Libraries Government Documents Department
open access

Constitutive modeling using the Taylor impact test

Description: The Taylor test can be conveniently divided into three fairly distinct stages: (1) initial transient behavior after impact characterized by nonlinear plastic wave propagation. (2) quasi-steady propagation of the plastic wave front. The duration of this stage is a function of specimen caliber and material. (3) terminal transient behavior, during which most of the deceleration of the undeformed section takes place. After the initial transient is complete, which varies with the strain at which the… more
Date: September 1, 1995
Creator: Jones, S.E.; Maudlin, P.J. & Foster, J.C. Jr.
Partner: UNT Libraries Government Documents Department
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