Automatic Generation of User Material Subroutines for Biomechanical Growth Analysis
Young, Jonathan M.; Yao, Jiang; Ramasubramanian, Ashok; Taber, Larry A.; Perucchio, Renato
2010-01-01
Background The analysis of the biomechanics of growth and remodeling in soft tissues requires the formulation of specialized pseudoelastic constitutive relations. The nonlinear finite element analysis (FEA) package Abaqus allows the user to implement such specialized material responses through the coding of a user material subroutine called UMAT. However, hand coding UMAT subroutines is a challenge even for simple pseudoelastic materials and requires substantial time to debug and test the code. Method To resolve this issue, we develop an automatic UMAT code generation procedure for pseudoelastic materials using the symbolic mathematics package Mathematica, and extend the UMAT generator to include continuum growth. The performance of the automatically coded UMAT is tested by simulating the stress–stretch response of a material defined by a Fung-Orthotropic strain energy function, subject to uniaxial stretching, equibiaxial stretching, and simple shear in Abaqus. The Mathematica UMAT generator is then extended to include continuum growth, by adding a growth subroutine to the automatically generated UMAT. Results The Mathematica UMAT generator correctly derives the variables required in the UMAT code, quickly providing a ready-to-use UMAT. In turn, the UMAT accurately simulates the pseudoelastic response. In order to test the growth UMAT we simulate the growth-based bending of a bilayered bar with differing fiber directions in a non-growing passive layer. The anisotropic passive layer, being topologically tied to the growing isotropic layer, causes the bending bar to twist laterally. Conclusions The results of simulations demonstrate the validity of the automatically coded UMAT, used in both standardized tests of hyperelastic materials and for biomechanical growth analysis. PMID:20887023
Using ABAQUS Scripting Interface for Materials Evaluation and Life Prediction
NASA Technical Reports Server (NTRS)
Powers, Lynn M.; Arnold, Steven M.; Baranski, Andrzej
2006-01-01
An ABAQUS script has been written to aid in the evaluation of the mechanical behavior of viscoplastic materials. The purposes of the script are to: handle complex load histories; control load/displacement with alternate stopping criteria; predict failure and life; and verify constitutive models. Material models from the ABAQUS library may be used or the UMAT routine may specify mechanical behavior. User subroutines implemented include: UMAT for the constitutive model; UEXTERNALDB for file manipulation; DISP for boundary conditions; and URDFIL for results processing. Examples presented include load, strain and displacement control tests on a single element model. The tests are creep with a life limiting strain criterion, strain control with a stress limiting cycle and a complex interrupted cyclic relaxation test. The techniques implemented in this paper enable complex load conditions to be solved efficiently with ABAQUS.
NASA Astrophysics Data System (ADS)
Chen, S.; Al-Muntasheri, G.; Abousleiman, Y. N.
2014-12-01
The critical state concept based bounding surface model is one of the most widely used elastoplastic constitutive models for geomaterials, attributed mainly to its essential feature of allowing plastic deformation to occur for stress points within the bounding surface and thus the capability to represent the realistic non-recoverable behaviour of soils and rocks observed under the cyclic loading. This paper develops an implicit integration algorithm for the bounding surface model, using the standard return mapping approach (elastic predictor-plastic corrector), to obtain the updated stresses for the given strain increments. The formulation of the constitutive integration requires the derivation of a supplementary differential equation to describe the evolution of a key variable, i.e., the ratio between the image stress and the current stress quantities. It is essentially an extension of the integration scheme presented in an earlier work used for the simple bounding surface version of modified Cam Clay associated with a substantially simplified hardening rule. The integration algorithm for the bounding surface model is implemented into the finite element analysis commercial program, ABAQUS, through the material interface of UMAT (user defined material subroutine), and then used for the analysis of wellbore stability problem. The predictions from the ABAQUS simulations are generally in excellent agreement with the available analytical solutions, thus demonstrating the accuracy and robustness of the proposed integration scheme.
A Weibull brittle material failure model for the ABAQUS computer program
Bennett, J.
1991-08-01
A statistical failure theory for brittle materials that traces its origins to the Weibull distribution function is developed for use in the general purpose ABAQUS finite element computer program. One of the fundamental assumptions for this development is that Mode 1 microfractures perpendicular to the direction of the principal stress contribute independently to the fast fracture. The theory is implemented by a user subroutine for ABAQUS. Example problems illustrating the capability and accuracy of the model are given. 24 refs., 12 figs.
Subroutines For Image Processing
NASA Technical Reports Server (NTRS)
Faulcon, Nettie D.; Monteith, James H.; Miller, Keith W.
1988-01-01
Image Processing Library computer program, IPLIB, is collection of subroutines facilitating use of COMTAL image-processing system driven by HP 1000 computer. Functions include addition or subtraction of two images with or without scaling, display of color or monochrome images, digitization of image from television camera, display of test pattern, manipulation of bits, and clearing of screen. Provides capability to read or write points, lines, and pixels from image; read or write at location of cursor; and read or write array of integers into COMTAL memory. Written in FORTRAN 77.
NASA Technical Reports Server (NTRS)
Schiess, J. R.
1994-01-01
Scientific data often contains random errors that make plotting and curve-fitting difficult. The Rational-Spline Approximation with Automatic Tension Adjustment algorithm lead to a flexible, smooth representation of experimental data. The user sets the conditions for each consecutive pair of knots:(knots are user-defined divisions in the data set) to apply no tension; to apply fixed tension; or to determine tension with a tension adjustment algorithm. The user also selects the number of knots, the knot abscissas, and the allowed maximum deviations from line segments. The selection of these quantities depends on the actual data and on the requirements of a particular application. This program differs from the usual spline under tension in that it allows the user to specify different tension values between each adjacent pair of knots rather than a constant tension over the entire data range. The subroutines use an automatic adjustment scheme that varies the tension parameter for each interval until the maximum deviation of the spline from the line joining the knots is less than or equal to a user-specified amount. This procedure frees the user from the drudgery of adjusting individual tension parameters while still giving control over the local behavior of the spline The Rational Spline program was written completely in FORTRAN for implementation on a CYBER 850 operating under NOS. It has a central memory requirement of approximately 1500 words. The program was released in 1988.
A parameter estimation subroutine package
NASA Technical Reports Server (NTRS)
Bierman, G. J.; Nead, M. W.
1978-01-01
Linear least squares estimation and regression analyses continue to play a major role in orbit determination and related areas. In this report we document a library of FORTRAN subroutines that have been developed to facilitate analyses of a variety of estimation problems. Our purpose is to present an easy to use, multi-purpose set of algorithms that are reasonably efficient and which use a minimal amount of computer storage. Subroutine inputs, outputs, usage and listings are given along with examples of how these routines can be used. The following outline indicates the scope of this report: Section (1) introduction with reference to background material; Section (2) examples and applications; Section (3) subroutine directory summary; Section (4) the subroutine directory user description with input, output, and usage explained; and Section (5) subroutine FORTRAN listings. The routines are compact and efficient and are far superior to the normal equation and Kalman filter data processing algorithms that are often used for least squares analyses.
Seismic transducer modeling using ABAQUS
Stephen R. Novascone
2004-05-01
A seismic transducer, known as an orbital vibrator, consists of a rotating imbalance driven by an electric motor. When suspended in a liquid-filled wellbore, vibrations of the device are coupled to the surrounding geologic media. In this mode, an orbital vibrator can be used as an efficient rotating dipole source for seismic imaging. Alternately, the motion of an orbital vibrator is affected by the physical properties of the surrounding media. From this point of view, an orbital vibrator can be used as a stand-alone sensor. The reaction to the surroundings can be sensed and recorded by geophones inside the orbital vibrator. These reactions are a function of the media’s physical properties such as modulus, damping, and density, thereby identifying the rock type. This presentation shows how the orbital vibrator and surroundings were modeled with an ABAQUS acoustic FEM. The FEM is found to compare favorably with theoretical predictions. A 2D FEM and analytical model are compared to an experimental data set. Each model compares favorably with the data set.
A parameter estimation subroutine package
NASA Technical Reports Server (NTRS)
Bierman, G. J.; Nead, M. W.
1978-01-01
Linear least squares estimation and regression analyses continue to play a major role in orbit determination and related areas. A library of FORTRAN subroutines were developed to facilitate analyses of a variety of estimation problems. An easy to use, multi-purpose set of algorithms that are reasonably efficient and which use a minimal amount of computer storage are presented. Subroutine inputs, outputs, usage and listings are given, along with examples of how these routines can be used. The routines are compact and efficient and are far superior to the normal equation and Kalman filter data processing algorithms that are often used for least squares analyses.
Energy Science and Technology Software Center (ESTSC)
2004-02-02
The software is an ABAQUS/Standard UMAT (user defined material behavior subroutine) that implements the constitutive model for shape-memory alloy materials developed by Jannetti et. al. (2003a) using a fully implicit time integration scheme to integrate the constitutive equations. The UMAT is used in conjunction with ABAQUS/Standard to perform a finite-element analysis of SMA materials.
Basic Scientific Subroutines, Volume II.
ERIC Educational Resources Information Center
Ruckdeschel, F. R.
This book, second in a series dealing with scientific programing in the BASIC language, provides students, engineers, and scientists with a documented library of subroutines for scientific applications. Subjects of the eight chapters include: (1) least-squares approximation of functions and smoothing of data; (2) approximating functions by series…
Multi Platform Graphics Subroutine Library
Energy Science and Technology Software Center (ESTSC)
1992-02-21
DIGLIB is a collection of general graphics subroutines. It was designed to be small, reasonably fast, device-independent, and compatible with DEC-supplied operating systems for VAXes, PDP-11s, and LSI-11s, and the DOS operating system for IBM PCs and IBM-compatible machines. The software is readily usable by casual programmers for two-dimensional plotting.
2013-01-01
Background Entry from secondary school to Australian and New Zealand undergraduate medical schools has since the late 1990’s increasingly relied on the Undergraduate Medicine and Health Sciences Admission Test (UMAT) as one of the selection factors. The UMAT consists of 3 sections – logical reasoning and problem solving (UMAT-1), understanding people (UMAT-2) and non-verbal reasoning (UMAT-3). One of the goals of using this test has been to enhance equity in the selection of students with the anticipation of an increase in the socioeconomic diversity in student cohorts. However there has been limited assessment as to whether UMAT performance itself might be influenced by socioeconomic background. Methods Between 2000 and 2012, 158,909 UMAT assessments were completed. From these, 118,085 cases have been identified where an Australian candidate was sitting for the first time during that period. Predictors of the total UMAT score, UMAT-1, UMAT-2 and UMAT-3 scores were entered into regression models and included gender, age, school type, language used at home, deciles for the Index of Relative Socioeconomic Advantage and Disadvantage score, the Accessibility/Remoteness Index of Australia (ARIA), self-identification as being of Aboriginal or Torres Strait Islander origin (ATSI) and current Australian state or territory of abode. Results A lower UMAT score was predicted by living in an area of relatively higher social disadvantage and lower social advantage. Other socioeconomic indicators were consistent with this observation with lower scores in those who self-identified as being of ATSI origin and higher scores evident in those from fee-paying independent school backgrounds compared to government schools. Lower scores were seen with increasing age, female gender and speaking any language other than English at home. Divergent effects of rurality were observed, with increased scores for UMAT-1 and UMAT-2, but decreasing UMAT-3 scores with increasing ARIA score
Abaqus Simulations of Rock Response to Dynamic Loading
Steedman, David W.; Coblentz, David
2012-08-15
The LANL Geodynamics Team has been applying Abaqus modeling to achieve increasingly complex simulations. Advancements in Abaqus model building and simulation tools allows this progress. We use Lab-developed constitutive models, the fully coupled CEL Abaqus and general contact to simulate response of realistic sites to explosively driven shock.
The Computer Subroutine in Information Handling.
ERIC Educational Resources Information Center
Riggs, Donald E.
Generalized computational subroutines can reduce programing repetitions and wasteful computer storage use. The most useful are those that are flexible enough to handle a wide variety of situations. Subroutines may have details open to change in order to blend into the main program. They may be built into the computer library or supplied by the…
Credit Documentation and the Mark 15 Subroutine
McAllister, J.E.
2001-08-16
This report documents the rewrite of the heat transfer subroutine. Part of the process of preparing the Mark 15 assembly for production operation is the development of thermal-hydraulic limits for the assembly. These limits require, among other items, the development of a Mark 15 assembly subroutine for the CREDIT code.
NASA Technical Reports Server (NTRS)
Arnold, S. M.; Saleeb, A. F.; Wilt, T. E.; Trowbridge, D.
2000-01-01
be incorporated directly into a structural finite element code like ABAQUS for cost-effective, micromechanics based, large-scale component design and analysis. Our primary objective here is to report on these recent works conducted over the past decade, in the context of their incorporation into ABAQUS through the various user subroutines. Representative results will be shown to demonstrate the features of the developed schemes.
MEAM interatomic force calculation subroutine for LAMMPS
Energy Science and Technology Software Center (ESTSC)
2010-10-25
Interatomic force and energy calculation subroutine tobe used with the molecular dynamics simulation code LAMMPS (Ref a.). The code evaluates the total energy and atomic forces (energy gradient) according to cubic spine-based variant (Ref b.) of the Modified Embedded Atom Method (MEAM).
Writing SUBROUTINE HOWFAR for EGS4
Nelson, W.R.; Jenkins, T.M.
1988-08-31
The purpose of this note is to provide guidance, in addition to that given in SLAC-265, in writing SUBROUTINE HOWFAR for both simple and complex geometrical situations. Since most complex geometries can be represented in terms of blocks of simpler geometries, a number of geometry subprograms have been created for use within HOWFAR. They are provided as part of the EGS4 Code System, which means that they are located in files on the EGS4 disk under VM/SP at SLAC. They are also on the EGS4 Distribution Tape that is given out on request by the SLAC Radiation Physics Group. What we hope to accomplish with this note is to show how to create EGS4 geometries in a modular fashion, with particular emphasis on using the macro equivalents of the subroutines in order to gain efficiency. It is assumed that the reader is already familiar with EGS4 and understands the role of the variables USTEP, IDISC, and IRNEW as they apply to SUBROUTINE HOWFAR. If not, then the reader is advised to study Appendix 2 of SLAC-265 first. The tutorial chapter may also provide some insight. 5 refs., 10 figs.
Input/Output Subroutine Library Program
NASA Technical Reports Server (NTRS)
Collier, James B.
1988-01-01
Efficient, easy-to-use program moved easily to different computers. Purpose of NAVIO, Input/Output Subroutine Library, provides input/output package of software for FORTRAN programs that is portable, efficient, and easy to use. Implemented as hierarchy of libraries. At bottom is very small library containing only non-portable routines called "I/O Kernel." Design makes NAVIO easy to move from one computer to another, by simply changing kernel. NAVIO appropriate for software system of almost any size wherein different programs communicate through files.
Modeling ductile dynamic fracture with ABAQUS/explicit
Anderson, C.A.; Turner, C.
1996-05-01
This paper illustrates the use of advanced constitutive models in ABAQUS/Explicit together with highly focused finite element meshes to simulate the propagation of a fracture in a ductile medium. A double edge-cracked specimen under far field dynamic tensile loading is analyzed, and shows both rectilinear motion or unstable oscillatory motion of the crack depending on the material property constraints. Results are also presented for a simulation of ASTM`s standard fracture test E399. Comparisons of ABAQUS/Explicit results with experiments or other analytical/numerical results are made.
Input Files and Procedures for Analysis of SMA Hybrid Composite Beams in MSC.Nastran and ABAQUS
NASA Technical Reports Server (NTRS)
Turner, Travis L.; Patel, Hemant D.
2005-01-01
A thermoelastic constitutive model for shape memory alloys (SMAs) and SMA hybrid composites (SMAHCs) was recently implemented in the commercial codes MSC.Nastran and ABAQUS. The model is implemented and supported within the core of the commercial codes, so no user subroutines or external calculations are necessary. The model and resulting structural analysis has been previously demonstrated and experimentally verified for thermoelastic, vibration and acoustic, and structural shape control applications. The commercial implementations are described in related documents cited in the references, where various results are also shown that validate the commercial implementations relative to a research code. This paper is a companion to those documents in that it provides additional detail on the actual input files and solution procedures and serves as a repository for ASCII text versions of the input files necessary for duplication of the available results.
Comparison between FEBio and Abaqus for biphasic contact problems.
Meng, Qingen; Jin, Zhongmin; Fisher, John; Wilcox, Ruth
2013-09-01
Articular cartilage plays an important role in the function of diarthrodial joints. Computational methods have been used to study the biphasic mechanics of cartilage, and Abaqus has been one of the most widely used commercial software packages for this purpose. A newly developed open-source finite element solver, FEBio, has been developed specifically for biomechanical applications. The aim of this study was to undertake a direct comparison between FEBio and Abaqus for some practical contact problems involving cartilage. Three model types, representing a porous flat-ended indentation test, a spherical-ended indentation test, and a conceptual natural joint contact model, were compared. In addition, a parameter sensitivity study was also performed for the spherical-ended indentation test to investigate the effects of changes in the input material properties on the model outputs, using both FEBio and Abaqus. Excellent agreement was found between FEBio and Abaqus for all of the model types and across the range of material properties that were investigated. PMID:23804955
Comparison between FEBio and Abaqus for biphasic contact problems
Jin, Zhongmin; Fisher, John; Wilcox, Ruth
2013-01-01
Articular cartilage plays an important role in the function of diarthrodial joints. Computational methods have been used to study the biphasic mechanics of cartilage, and Abaqus has been one of the most widely used commercial software packages for this purpose. A newly developed open-source finite element solver, FEBio, has been developed specifically for biomechanical applications. The aim of this study was to undertake a direct comparison between FEBio and Abaqus for some practical contact problems involving cartilage. Three model types, representing a porous flat-ended indentation test, a spherical-ended indentation test, and a conceptual natural joint contact model, were compared. In addition, a parameter sensitivity study was also performed for the spherical-ended indentation test to investigate the effects of changes in the input material properties on the model outputs, using both FEBio and Abaqus. Excellent agreement was found between FEBio and Abaqus for all of the model types and across the range of material properties that were investigated. PMID:23804955
IBM-1620 monitor 2-D disk-storage subroutines
NASA Technical Reports Server (NTRS)
Krejci, H. F.
1969-01-01
Set of subroutines provides the FORTRAN user with protected, permanent, disk storage of data on an IBM 1620 Monitor 11-D system. The program consists of a set of four subroutines and a utility program. It allows block data to be transferred directly between assigned core locations and disk storage.
The observational environment of astronomical satellites and related software subroutines
NASA Technical Reports Server (NTRS)
West, D. K.; Greville, E. M.
1972-01-01
Methods are described for calculating significant factors in the observational environment of orbiting astronomical satellites. These factors must be considered in the process of scheduling observations and in data reduction. Subroutines which perform these calculations are described.
Visualizing MCNP Tally Segment Geometry and Coupling Results with ABAQUS
J. R. Parry; J. A. Galbraith
2007-11-01
The Advanced Graphite Creep test, AGC-1, is planned for irradiation in the Advanced Test Reactor (ATR) in support of the Next Generation Nuclear Plant program. The experiment requires very detailed neutronics and thermal hydraulics analyses to show compliance with programmatic and ATR safety requirements. The MCNP model used for the neutronics analysis required hundreds of tally regions to provide the desired detail. A method for visualizing the hundreds of tally region geometries and the tally region results in 3 dimensions has been created to support the AGC-1 irradiation. Additionally, a method was created which would allow ABAQUS to access the results directly for the thermal analysis of the AGC-1 experiment.
Modeling micro-electronics drill bit behavior with ABAQUS Standard
Anderson, C.A.; Ricketson, E.
1997-06-01
Modeling of drill bit behavior under applied forces as well as modeling of the drilling process itself can aid in the understanding of the relative importance of the various drill bit process parameters and can eventually lead to improved drill bit designs. In this paper the authors illustrate the application of ABAQUS Standard to the stress and deformation analysis of micro-electronics drill bits that are used in manufacturing printed circuit boards. Effects of varying point geometry, web taper and flute length on the stress and deformation in a drill bit are illustrated.
Calibrating the Abaqus Crushable Foam Material Model using UNM Data
Schembri, Philip E.; Lewis, Matthew W.
2014-02-27
Triaxial test data from the University of New Mexico and uniaxial test data from W-14 is used to calibrate the Abaqus crushable foam material model to represent the syntactic foam comprised of APO-BMI matrix and carbon microballoons used in the W76. The material model is an elasto-plasticity model in which the yield strength depends on pressure. Both the elastic properties and the yield stress are estimated by fitting a line to the elastic region of each test response. The model parameters are fit to the data (in a non-rigorous way) to provide both a conservative and not-conservative material model. The model is verified to perform as intended by comparing the values of pressure and shear stress at yield, as well as the shear and volumetric stress-strain response, to the test data.
NASA Astrophysics Data System (ADS)
Carroll, K. C.; Nguyen, B. N.; Fang, Y.; Richmond, M. C.; Murray, C. J.
2011-12-01
Geomechanical alteration of porous media is generally ignored for most shallow subsurface applications, whereas CO2 injection, migration, and trapping in deep saline aquifers will be controlled by coupled multifluid flow, energy transfer, geomechanical, and geochemical processes. The accurate assessment of the risks associated with potential leakage of injected CO2 and the design of effective injection systems requires that we represent these coupled processes within numerical simulators. The objective of this study was to examine the coupling of hydraulic and geomechanical processes for simulation of CO2 injection into the subsurface for carbon sequestration. The impact of nonisothermal multifluid flow and porous media deformation mechanics on CO2 migration and storage was evaluated. We present a sequentially coupled approach for multifluid and geomechanical simulation using STOMP and ABAQUS that has been developed and validated through comparison to the solutions for benchmark problems that were solved with a coupled TOUGH-FLAC simulator. The poroelastic model was implemented with user-subroutines in ABAQUS. We also compare the STOMP-ABAQUS simulator to a new version of STOMP that includes the fully coupled poroelastic simulation within the multifluid flow and transport simulator. The poroelastic model computes stiffness, stresses, and strains using aqueous and gas pressures as well as saturations from STOMP output, and provides STOMP with the updated permeability, porosity, and capillary pressure over time during the simulation. The hydraulic only (uncoupled from mechanics) simulation and the hydrogeomechanical (coupled) simulation results using STOMP-ABAQUS were comparable to the previous results of a TOUGH-FLAC simulator. Results from the STOMP-ABAQUS coupled simulator were essentially identical to the fully coupled STOMP hydrogeomechanical simulator when the sequential coupling occurred at small time steps, and deviations between results increased with
NASA Technical Reports Server (NTRS)
Allen Phillip A.; Wilson, Christopher D.
2003-01-01
The development of a pressure-dependent constitutive model with combined multilinear kinematic and isotropic hardening is presented. The constitutive model is developed using the ABAQUS user material subroutine (UMAT). First the pressure-dependent plasticity model is derived. Following this, the combined bilinear and combined multilinear hardening equations are developed for von Mises plasticity theory. The hardening rule equations are then modified to include pressure dependency. The method for implementing the new constitutive model into ABAQUS is given.
Subroutines GEORGE and DRASTC simplify operation of automatic digital plotter
NASA Technical Reports Server (NTRS)
Englel, F., III; Gray, W. H.; Richard, P. J.
1967-01-01
FORTRAN language subroutines enable the production of a tape for a 360-30 tape unit that controls the CALCOMP 566 Digital Incremental Plotter. This provides the plotter with instructions for graphically displaying data points with the proper scaling of axes, numbering, lettering, and tic marking.
FORTRAN plotting subroutines for the space plasma laboratory
NASA Technical Reports Server (NTRS)
Williams, R.
1983-01-01
The computer program known as PLOTRW was custom made to satisfy some of the graphics requirements for the data collected in the Space Plasma Laboratory at the Johnson Space Center (JSC). The general requirements for the program were as follows: (1) all subroutines shall be callable through a FORTRAN source program; (2) all graphs shall fill one page and be properly labeled; (3) there shall be options for linear axes and logarithmic axes; (4) each axis shall have tick marks equally spaced with numeric values printed at the beginning tick mark and at the last tick mark; and (5) there shall be three options for plotting. These are: (1) point plot, (2) line plot and (3) point-line plot. The subroutines were written in FORTRAN IV for the LSI-11 Digital equipment Corporation (DEC) Computer. The program is now operational and can be run on any TEKTRONICX graphics terminal that uses a DEC Real-Time-11 (RT-11) operating system.
Algorithm-Based Fault Tolerance for Numerical Subroutines
NASA Technical Reports Server (NTRS)
Tumon, Michael; Granat, Robert; Lou, John
2007-01-01
A software library implements a new methodology of detecting faults in numerical subroutines, thus enabling application programs that contain the subroutines to recover transparently from single-event upsets. The software library in question is fault-detecting middleware that is wrapped around the numericalsubroutines. Conventional serial versions (based on LAPACK and FFTW) and a parallel version (based on ScaLAPACK) exist. The source code of the application program that contains the numerical subroutines is not modified, and the middleware is transparent to the user. The methodology used is a type of algorithm- based fault tolerance (ABFT). In ABFT, a checksum is computed before a computation and compared with the checksum of the computational result; an error is declared if the difference between the checksums exceeds some threshold. Novel normalization methods are used in the checksum comparison to ensure correct fault detections independent of algorithm inputs. In tests of this software reported in the peer-reviewed literature, this library was shown to enable detection of 99.9 percent of significant faults while generating no false alarms.
Thermal and flow analysis subroutines for the SINDA-version 9 computer routine
NASA Technical Reports Server (NTRS)
Oren, J. A.; Williams, D. R.
1973-01-01
Fluid flow analysis, special thermal analysis and input/output capabilities of the MOTAR routine were incorporated into the SINDA routine. All the capabilities were added in the form of user subroutines so that they may be added to different versions of SINDA with a minimum of programmer effort. Two modifications were made to the existing subroutines of SINDA/8 to incorporate the above subroutines. These were: (1) A modification to the preprocessor to permit actual values of array numbers, conductor numbers, node numbers or constant numbers supplied as array data to be converted to relative numbers. (2) Modifications to execution subroutine CNFAST to make it compatible with the radiant interchange user subroutine, RADIR. This modified version of SINDA has been designated SINDA/version 9. A detailed discussion of the methods used for the capabilities added is presented. The modifications for the SINDA subroutines are described, as well as user subroutines. All subroutines added or modified are listed.
AMPHION: Specification-based programming for scientific subroutine libraries
NASA Technical Reports Server (NTRS)
Lowry, Michael; Philpot, Andrew; Pressburger, Thomas; Underwood, Ian; Waldinger, Richard; Stickel, Mark
1994-01-01
AMPHION is a knowledge-based software engineering (KBSE) system that guides a user in developing a diagram representing a formal problem specification. It then automatically implements a solution to this specification as a program consisting of calls to subroutines from a library. The diagram provides an intuitive domain oriented notation for creating a specification that also facilitates reuse and modification. AMPHION'S architecture is domain independent. AMPHION is specialized to an application domain by developing a declarative domain theory. Creating a domain theory is an iterative process that currently requires the joint expertise of domain experts and experts in automated formal methods for software development.
A simple pharmacokinetics subroutine for modeling double peak phenomenon.
Mirfazaelian, Ahmad; Mahmoudian, Massoud
2006-04-01
Double peak absorption has been described with several orally administered drugs. Numerous reasons have been implicated in causing the double peak. DRUG-KNT--a pharmacokinetic software developed previously for fitting one and two compartment kinetics using the iterative curve stripping method--was modified and a revised subroutine was incorporated to solve double-peak models. This subroutine considers the double peak as two hypothetical doses administered with a time gap. The fitting capability of the presented model was verified using four sets of data showing double peak profiles extracted from the literature (piroxicam, ranitidine, phenazopyridine and talinolol). Visual inspection and statistical diagnostics showed that the present algorithm provided adequate curve fit disregarding the mechanism involved in the emergence of the secondary peaks. Statistical diagnostic parameters (RSS, AIC and R2) generally showed good fitness in the plasma profile prediction by this model. It was concluded that the algorithm presented herein provides adequate predicted curves in cases of the double peak phenomenon. PMID:16400712
NASA Technical Reports Server (NTRS)
Wohlen, R. L.
1976-01-01
A listing of the source deck of each finite element FORMA subroutine is given to remove the 'black-box' aura of the subroutines so that the analyst may better understand the detailed operations of each subroutine. The FORTRAN 4 programming language is used in all finite element FORMA subroutines.
Developing an Abaqus *HYPERFOAM Model for M9747 (4003047) Cellular Silicone Foam
Siranosian, Antranik A.; Stevens, R. Robert
2012-04-26
This report documents work done to develop an Abaqus *HYPERFOAM hyperelastic model for M9747 (4003047) cellular silicone foam for use in quasi-static analyses at ambient temperature. Experimental data, from acceptance tests for 'Pad A' conducted at the Kansas City Plant (KCP), was used to calibrate the model. The data includes gap (relative displacement) and load measurements from three locations on the pad. Thirteen sets of data, from pads with different serial numbers, were provided. The thirty-nine gap-load curves were extracted from the thirteen supplied Excel spreadsheets and analyzed, and from those thirty-nine one set of data, representing a qualitative mean, was chosen to calibrate the model. The data was converted from gap and load to nominal (engineering) strain and nominal stress in order to implement it in Abaqus. Strain computations required initial pad thickness estimates. An Abaqus model of a right-circular cylinder was used to evaluate and calibrate the *HYPERFOAM model.
NASA Technical Reports Server (NTRS)
Arnold, Steven M.; Bednarcyk, Brett A.; Hussain, Aquila; Katiyar, Vivek
2010-01-01
A unified framework is presented that enables coupled multiscale analysis of composite structures and associated graphical pre- and postprocessing within the Abaqus/CAE environment. The recently developed, free, Finite Element Analysis--Micromechanics Analysis Code (FEAMAC) software couples NASA's Micromechanics Analysis Code with Generalized Method of Cells (MAC/GMC) with Abaqus/Standard and Abaqus/Explicit to perform micromechanics based FEA such that the nonlinear composite material response at each integration point is modeled at each increment by MAC/GMC. The Graphical User Interfaces (FEAMAC-Pre and FEAMAC-Post), developed through collaboration between SIMULIA Erie and the NASA Glenn Research Center, enable users to employ a new FEAMAC module within Abaqus/CAE that provides access to the composite microscale. FEA IAC-Pre is used to define and store constituent material properties, set-up and store composite repeating unit cells, and assign composite materials as sections with all data being stored within the CAE database. Likewise FEAMAC-Post enables multiscale field quantity visualization (contour plots, X-Y plots), with point and click access to the microscale i.e., fiber and matrix fields).
Vande Geest, Jonathan P; Simon, B R; Rigby, Paul H; Newberg, Tyler P
2011-04-01
Finite element models (FEMs) including characteristic large deformations in highly nonlinear materials (hyperelasticity and coupled diffusive/convective transport of neutral mobile species) will allow quantitative study of in vivo tissues. Such FEMs will provide basic understanding of normal and pathological tissue responses and lead to optimization of local drug delivery strategies. We present a coupled porohyperelastic mass transport (PHEXPT) finite element approach developed using a commercially available ABAQUS finite element software. The PHEXPT transient simulations are based on sequential solution of the porohyperelastic (PHE) and mass transport (XPT) problems where an Eulerian PHE FEM is coupled to a Lagrangian XPT FEM using a custom-written FORTRAN program. The PHEXPT theoretical background is derived in the context of porous media transport theory and extended to ABAQUS finite element formulations. The essential assumptions needed in order to use ABAQUS are clearly identified in the derivation. Representative benchmark finite element simulations are provided along with analytical solutions (when appropriate). These simulations demonstrate the differences in transient and steady state responses including finite deformations, total stress, fluid pressure, relative fluid, and mobile species flux. A detailed description of important model considerations (e.g., material property functions and jump discontinuities at material interfaces) is also presented in the context of finite deformations. The ABAQUS-based PHEXPT approach enables the use of the available ABAQUS capabilities (interactive FEM mesh generation, finite element libraries, nonlinear material laws, pre- and postprocessing, etc.). PHEXPT FEMs can be used to simulate the transport of a relatively large neutral species (negligible osmotic fluid flux) in highly deformable hydrated soft tissues and tissue-engineered materials. PMID:21428686
NASA Astrophysics Data System (ADS)
Williamson, R. L.
2011-08-01
A powerful multidimensional fuels performance analysis capability, applicable to both steady and transient fuel behavior, is developed based on enhancements to the commercially available ABAQUS general-purpose thermomechanics code. Enhanced capabilities are described, including: UO 2 temperature and burnup dependent thermal properties, solid and gaseous fission product swelling, fuel densification, fission gas release, cladding thermal and irradiation creep, cladding irradiation growth, gap heat transfer, and gap/plenum gas behavior during irradiation. This new capability is demonstrated using a 2D axisymmetric analysis of the upper section of a simplified multipellet fuel rod, during both steady and transient operation. Comparisons are made between discrete and smeared-pellet simulations. Computational results demonstrate the importance of a multidimensional, multipellet, fully-coupled thermomechanical approach. Interestingly, many of the inherent deficiencies in existing fuel performance codes (e.g., 1D thermomechanics, loose thermomechanical coupling, separate steady and transient analysis, cumbersome pre- and post-processing) are, in fact, ABAQUS strengths.
Toward high-speed 3D nonlinear soft tissue deformation simulations using Abaqus software.
Idkaidek, Ashraf; Jasiuk, Iwona
2015-12-01
We aim to achieve a fast and accurate three-dimensional (3D) simulation of a porcine liver deformation under a surgical tool pressure using the commercial finite element software Abaqus. The liver geometry is obtained using magnetic resonance imaging, and a nonlinear constitutive law is employed to capture large deformations of the tissue. Effects of implicit versus explicit analysis schemes, element type, and mesh density on computation time are studied. We find that Abaqus explicit and implicit solvers are capable of simulating nonlinear soft tissue deformations accurately using first-order tetrahedral elements in a relatively short time by optimizing the element size. This study provides new insights and guidance on accurate and relatively fast nonlinear soft tissue simulations. Such simulations can provide force feedback during robotic surgery and allow visualization of tissue deformations for surgery planning and training of surgical residents. PMID:26530842
Enhancing the ABAQUS Thermomechanics Code to Simulate Steady and Transient Fuel Rod Behavior
R. L. Williamson; D. A. Knoll
2009-09-01
A powerful multidimensional fuels performance capability, applicable to both steady and transient fuel behavior, is developed based on enhancements to the commercially available ABAQUS general-purpose thermomechanics code. Enhanced capabilities are described, including: UO2 temperature and burnup dependent thermal properties, solid and gaseous fission product swelling, fuel densification, fission gas release, cladding thermal and irradiation creep, cladding irradiation growth , gap heat transfer, and gap/plenum gas behavior during irradiation. The various modeling capabilities are demonstrated using a 2D axisymmetric analysis of the upper section of a simplified multi-pellet fuel rod, during both steady and transient operation. Computational results demonstrate the importance of a multidimensional fully-coupled thermomechanics treatment. Interestingly, many of the inherent deficiencies in existing fuel performance codes (e.g., 1D thermomechanics, loose thermo-mechanical coupling, separate steady and transient analysis, cumbersome pre- and post-processing) are, in fact, ABAQUS strengths.
NASA Technical Reports Server (NTRS)
Wohlen, R. L.
1976-01-01
A listing of the source deck of each dense FORMA subroutine is given to remove the 'black-box' aura of the subroutines so that the analyst may better understand the detail operations of each subroutine. The FORTRAN 4 programming language is used throughout.
Goodman and Kruskal's TAU-B Statistics: A Fortran-77 Subroutine.
ERIC Educational Resources Information Center
Berry, Kenneth J.; Mielke, Paul W., Jr.
1986-01-01
An algorithm and associated FORTRAN-77 computer subroutine are described for computing Goodman and Kruskal's tau-b statistic along with the associated nonasymptotic probability value under the null hypothesis tau=O. (Author)
On testing a subroutine for the numerical integration of ordinary differential equations
NASA Technical Reports Server (NTRS)
Krogh, F. T.
1973-01-01
This paper discusses how to numerically test a subroutine for the solution of ordinary differential equations. Results obtained with a variable order Adams method are given for eleven simple test cases.-
Sullivan, W. N.; Leonard, T. M.
1980-11-01
An important aspect of structural design of the Darrieus rotor is the determination of aerodynamic blade loads. This report describes a load generator which has been used at Sandia for quasi-static and dynamic rotor analyses. The generator is based on the single streamtube aerodynamic flow model and is constructed as a FORTRAN IV subroutine to facilitate its use in finite element structural models. Input and output characteristics of the subroutine are described and a complete listing is attached as an appendix.
Computer subroutines for estimation of human exposure to radiation in low Earth orbit
NASA Technical Reports Server (NTRS)
Cucinotta, F. A.; Wilson, J. W.
1985-01-01
Computer subroutines to calculate human exposure to trapped radiations in low Earth orbit (LEO) on the basis of a simple approximation of the human geometry by spherical shell shields of varying thickness are presented and detailed. The subroutines calculate the dose to critical body organs and the fraction of exposure limit reached as a function of altitude of orbit, degree of inclination, shield thickness, and days in mission. Exposure rates are compared with current exposure limits.
NASA Astrophysics Data System (ADS)
Li, Wenya; Wang, Feifan; Shi, Shanxiang; Ma, Tiejun
2013-11-01
In order to investigate the complicated thermomechanically coupled process of linear friction welding (LFW), three different numerical methods were developed using the ABAQUS software. LFW steel and Ti-6Al-4V were calculated by using a 2D model with the explicit and implicit methods, respectively, and the calculated results were validated by experiments. In addition, a 3D model for LFW Ti-5Al-2Sn-2Zr-4Mo-4Cr was firstly acquired by using the newly developed explicit-implicit alternate method and the calculated flash seemed more like the real one. Furthermore, a few open questions and perspectives in LFW modeling are discussed and concluded.
NASA Technical Reports Server (NTRS)
Wilson, J. W.; Khandelwal, G. S.
1976-01-01
Calculational methods for estimation of dose from external proton exposure of arbitrary convex bodies are briefly reviewed. All the necessary information for the estimation of dose in soft tissue is presented. Special emphasis is placed on retaining the effects of nuclear reaction, especially in relation to the dose equivalent. Computer subroutines to evaluate all of the relevant functions are discussed. Nuclear reaction contributions for standard space radiations are in most cases found to be significant. Many of the existing computer programs for estimating dose in which nuclear reaction effects are neglected can be readily converted to include nuclear reaction effects by use of the subroutines described herein.
Binorm-a fortran subroutine to calculate the percentiles of a standardized binormal distribution
McCammon, R.B.
1977-01-01
BINORM is a FORTRAN subroutine for calculating the percentiles of a standardized binormal distribution. By using a linear transformation, the percentiles of a binormal distribution can be obtained. The percentiles of a binormal distribution are useful for plotting purposes, for establishing confidence intervals, and for sampling from a mixed population that consists of two normal distributions. ?? 1977.
Cauble, R.; Rozmus, W.
1993-10-21
A FORTRAN subroutine for the calculation of the ac electrical conductivity in two-temperature, strongly coupled, overdense plasma is presented. The routine is the result of a model calculation based on classical transport theory with application to plasmas created by the interaction of short pulse lasers and solids. The formulation is analytic and the routine is self-contained.
Performance Analysis of Memory Transfers and GEMM Subroutines on NVIDIA Tesla GPU Cluster
Allada, Veerendra, Benjegerdes, Troy; Bode, Brett
2009-08-31
Commodity clusters augmented with application accelerators are evolving as competitive high performance computing systems. The Graphical Processing Unit (GPU) with a very high arithmetic density and performance per price ratio is a good platform for the scientific application acceleration. In addition to the interconnect bottlenecks among the cluster compute nodes, the cost of memory copies between the host and the GPU device have to be carefully amortized to improve the overall efficiency of the application. Scientific applications also rely on efficient implementation of the BAsic Linear Algebra Subroutines (BLAS), among which the General Matrix Multiply (GEMM) is considered as the workhorse subroutine. In this paper, they study the performance of the memory copies and GEMM subroutines that are critical to port the computational chemistry algorithms to the GPU clusters. To that end, a benchmark based on the NetPIPE framework is developed to evaluate the latency and bandwidth of the memory copies between the host and the GPU device. The performance of the single and double precision GEMM subroutines from the NVIDIA CUBLAS 2.0 library are studied. The results have been compared with that of the BLAS routines from the Intel Math Kernel Library (MKL) to understand the computational trade-offs. The test bed is a Intel Xeon cluster equipped with NVIDIA Tesla GPUs.
Fitting: Subroutine to fit four-moment probability distributions to data
Winterstein, S.R.; Lange, C.H.; Kumar, S.
1995-01-01
FITTING is a Fortran subroutine that constructs a smooth, generalized four-parameter probability distribution model. It is fit to the first four statistical moments of the random variable X (i.e., average values of X, X{sup 2}, X{sup 3}, and X{sup 4}) which can be calculated from data using the associated subroutine CALMOM. The generalized model is produced from a cubic distortion of the parent model, calibrated to match the first four moments of the data. This four-moment matching is intended to provide models that are more faithful to the data in the upper tail of the distribution. Examples are shown for two specific cases.
Attitude dynamics simulation subroutines for systems of hinge-connected rigid bodies
NASA Technical Reports Server (NTRS)
Fleischer, G. E.; Likins, P. W.
1974-01-01
Several computer subroutines are designed to provide the solution to minimum-dimension sets of discrete-coordinate equations of motion for systems consisting of an arbitrary number of hinge-connected rigid bodies assembled in a tree topology. In particular, these routines may be applied to: (1) the case of completely unrestricted hinge rotations, (2) the totally linearized case (all system rotations are small), and (3) the mixed, or partially linearized, case. The use of the programs in each case is demonstrated using a five-body spacecraft and attitude control system configuration. The ability of the subroutines to accommodate prescribed motions of system bodies is also demonstrated. Complete listings and user instructions are included for these routines (written in FORTRAN V) which are intended as multi- and general-purpose tools in the simulation of spacecraft and other complex electromechanical systems.
NASA Technical Reports Server (NTRS)
Fleischer, G. E.; Likins, P. W.
1975-01-01
Three computer subroutines designed to solve the vector-dyadic differential equations of rotational motion for systems that may be idealized as a collection of hinge-connected rigid bodies assembled in a tree topology, with an optional flexible appendage attached to each body are reported. Deformations of the appendages are mathematically represented by modal coordinates and are assumed small. Within these constraints, the subroutines provide equation solutions for (1) the most general case of unrestricted hinge rotations, with appendage base bodies nominally rotating at a constant speed, (2) the case of unrestricted hinge rotations between rigid bodies, with the restriction that those rigid bodies carrying appendages are nominally nonspinning, and (3) the case of small hinge rotations and nominally nonrotating appendages. Sample problems and their solutions are presented to illustrate the utility of the computer programs.
Galluzzi, L; Vitale, I; Abrams, J M; Alnemri, E S; Baehrecke, E H; Blagosklonny, M V; Dawson, T M; Dawson, V L; El-Deiry, W S; Fulda, S; Gottlieb, E; Green, D R; Hengartner, M O; Kepp, O; Knight, R A; Kumar, S; Lipton, S A; Lu, X; Madeo, F; Malorni, W; Mehlen, P; Nuñez, G; Peter, M E; Piacentini, M; Rubinsztein, D C; Shi, Y; Simon, H-U; Vandenabeele, P; White, E; Yuan, J; Zhivotovsky, B; Melino, G; Kroemer, G
2012-01-01
In 2009, the Nomenclature Committee on Cell Death (NCCD) proposed a set of recommendations for the definition of distinct cell death morphologies and for the appropriate use of cell death-related terminology, including ‘apoptosis', ‘necrosis' and ‘mitotic catastrophe'. In view of the substantial progress in the biochemical and genetic exploration of cell death, time has come to switch from morphological to molecular definitions of cell death modalities. Here we propose a functional classification of cell death subroutines that applies to both in vitro and in vivo settings and includes extrinsic apoptosis, caspase-dependent or -independent intrinsic apoptosis, regulated necrosis, autophagic cell death and mitotic catastrophe. Moreover, we discuss the utility of expressions indicating additional cell death modalities. On the basis of the new, revised NCCD classification, cell death subroutines are defined by a series of precise, measurable biochemical features. PMID:21760595
Utility subroutine package used by Applied Physics Division export codes. [LMFBR
Adams, C.H.; Derstine, K.L.; Henryson, H. II; Hosteny, R.P.; Toppel, B.J.
1983-04-01
This report describes the current state of the utility subroutine package used with codes being developed by the staff of the Applied Physics Division. The package provides a variety of useful functions for BCD input processing, dynamic core-storage allocation and managemnt, binary I/0 and data manipulation. The routines were written to conform to coding standards which facilitate the exchange of programs between different computers.
The inverse of winnowing: a FORTRAN subroutine and discussion of unwinnowing discrete data
Bracken, Robert E.
2004-01-01
This report describes an unwinnowing algorithm that utilizes a discrete Fourier transform, and a resulting Fortran subroutine that winnows or unwinnows a 1-dimensional stream of discrete data; the source code is included. The unwinnowing algorithm effectively increases (by integral factors) the number of available data points while maintaining the original frequency spectrum of a data stream. This has utility when an increased data density is required together with an availability of higher order derivatives that honor the original data.
Development of a CMAQ Subroutine for Wind-blown Dust Emission Calculation
NASA Astrophysics Data System (ADS)
Park, S.
2011-12-01
A subroutine for calculating the wind-blown dust emission in the framework of the Community Multiscale Air Quality Modeling System (CMAQ) has been developed. This new subroutine, called WDEMIS, is analogous in its use to the recently added sea-salt emission subroutine SSEMIS. To make use of WDEMIS, the subroutine AERO_EMIS has to be modified so that WDEMIS (just like SSEMIS) is called by AERO_EMIS. The threshold friction velocity for smooth dry surface, the drag partitioning effect by non-erodible surface roughness elements, the soil moisture effect, the positive feedback of the saltating soil particles to the friction velocity, the saltation scheme calculating the horizontal soil flux, and the sandblasting scheme calculating the vertical dust emission flux are accounted for in WDEMIS. In order to supply soil characteristics required for wind-blown dust emission calculation, i.e., soil moisture content, land use fraction, and soil texture, the Pleim-Xiu land-surface model [Xiu and Pleim, 2001] is used by the Fifth-Generation NCAR/Penn State Mesoscale Model (MM5) combined with MCIP version 3.6. CMAQ modelling using WDEMIS was performed to simulate an Asian dust storm episode that occurred in April 2006 to evaluate the wind-blown dust emission prediction by WDEMIS. Sensitivity analysis showed that the accuracy of land use data and soil property supplied to WDEMIS is critical to performance of WDEMIS. Appropriate size fractioning is considered one of the most important improvement required in the future. Xiu, A., and J.E. Pleim, Development of a land surface model. Part I: Application in a mesoscale meteorology model, Journal of Applied Meteorology, 40, 192-209, 2001.
Coupled field-structural analysis of HGTR fuel brick using ABAQUS
Mohanty, S.; Jain, R.; Majumdar, S.; Tautges, T. J.; Srinivasa, M.
2012-07-01
High-temperature, gas-cooled reactors (HTGRs) are usually helium-gas cooled, with a graphite core that can operate at reactor outlet temperatures much higher than can conventional light water reactors. In HTGRs, graphite components moderate and reflect neutrons. During reactor operation, high temperature and high irradiation cause damage to the graphite crystal and grains and create other defects. This cumulative structural damage during the reactor lifetime leads to changes in graphite properties, which can alter the ability to support the designed loads. The aim of the present research is to develop a finite-element code using commercially available ABAQUS software for the structural integrity analysis of graphite core components under extreme temperature and irradiation conditions. In addition, the Reactor Geometry Generator tool-kit, developed at Argonne National Laboratory, is used to generate finite-element mesh for complex geometries such as fuel bricks with multiple pin holes and coolant flow channels. This paper presents the proposed concept and discusses results of stress analysis simulations of a fuel block with H-451 grade material properties. (authors)
Analysis of SMA Hybrid Composite Structures in MSC.Nastran and ABAQUS
NASA Technical Reports Server (NTRS)
Turner, Travis L.; Patel, Hemant D.
2005-01-01
A thermoelastic constitutive model for shape memory alloy (SMA) actuators and SMA hybrid composite (SMAHC) structures was recently implemented in the commercial finite element codes MSC.Nastran and ABAQUS. The model may be easily implemented in any code that has the capability for analysis of laminated composite structures with temperature dependent material properties. The model is also relatively easy to use and requires input of only fundamental engineering properties. A brief description of the model is presented, followed by discussion of implementation and usage in the commercial codes. Results are presented from static and dynamic analysis of SMAHC beams of two types; a beam clamped at each end and a cantilever beam. Nonlinear static (post-buckling) and random response analyses are demonstrated for the first specimen. Static deflection (shape) control is demonstrated for the cantilever beam. Approaches for modeling SMAHC material systems with embedded SMA in ribbon and small round wire product forms are demonstrated and compared. The results from the commercial codes are compared to those from a research code as validation of the commercial implementations; excellent correlation is achieved in all cases.
A subroutine for rounding of numbers. Program in BASIC and for programmable calculators.
Brodthagen, U A
1987-01-01
The present programs were developed to compensate for the poor precision of some microcomputer-BASICs, and to avoid printing of the non-significant figures of a numerical result. The program will round any number to a user defined number of significant digits. The subroutine is well suited for statistical programs. It enables the programmer to control the precision and format of numerical output. The program is given in two versions, one in BASIC and one for the programmable calculator TI-59. PMID:3816164
A general purpose subroutine for fast fourier transform on a distributed memory parallel machine
NASA Technical Reports Server (NTRS)
Dubey, A.; Zubair, M.; Grosch, C. E.
1992-01-01
One issue which is central in developing a general purpose Fast Fourier Transform (FFT) subroutine on a distributed memory parallel machine is the data distribution. It is possible that different users would like to use the FFT routine with different data distributions. Thus, there is a need to design FFT schemes on distributed memory parallel machines which can support a variety of data distributions. An FFT implementation on a distributed memory parallel machine which works for a number of data distributions commonly encountered in scientific applications is presented. The problem of rearranging the data after computing the FFT is also addressed. The performance of the implementation on a distributed memory parallel machine Intel iPSC/860 is evaluated.
UNAERO: A package of FORTRAN subroutines for approximating unsteady aerodynamics in the time domain
NASA Technical Reports Server (NTRS)
Dunn, H. J.
1985-01-01
This report serves as an instruction and maintenance manual for a collection of CDC CYBER FORTRAN IV subroutines for approximating the unsteady aerodynamic forces in the time domain. The result is a set of constant-coefficient first-order differential equations that approximate the dynamics of the vehicle. Provisions are included for adjusting the number of modes used for calculating the approximations so that an accurate approximation is generated. The number of data points at different values of reduced frequency can also be varied to adjust the accuracy of the approximation over the reduced-frequency range. The denominator coefficients of the approximation may be calculated by means of a gradient method or a least-squares approximation technique. Both the approximation methods use weights on the residual error. A new set of system equations, at a different dynamic pressure, can be generated without the approximations being recalculated.
Radiology PRICER 2. 0 subroutine installation guide, Volume 1 and Volume 2
Kowaleski, R.
1989-04-01
Radiology pricing subroutine (PRICER 2.0) is furnished by the Health Care Financing Administration to process the payment of Outpatient Medicare claims with discharges on or after April 1, 1989. Volumes 1 and 2 contain the installation and operation guidelines necessary to install PRICER 2.0 in an IBM 3090 environment. The installation requires that the receiver be familiar with COBOL/VS, OS JCL, and that an interface module has been previously installed. The installation tape contains the program source code and data files necessary to completely install Radiology PRICER 2.0. Volume 2 contains Appendix A through G: Appendix A - RADMAIN (driver) source listing; Appendix B - RADPRICE source listing; Appendix C - listing of the Provider File; Appendix D - listing of the HCPCS Code File; Appendix E - listing of the Prevailing Charge/Fee Schedule File; Appendix F - listing of the bill test file; Appendix G - listing of the expected test results.
An ASCII FORTRAN subroutine for computing the electromagnetic radiation scattered by a sphere
NASA Astrophysics Data System (ADS)
Milham, M. E.
1981-11-01
This report describes the ASCMIE subroutine for performing Mie scattering calculations by means of the downward recursion algorithm developed by J. V. Dave. ASCMIE is written in UNIVAC 1100 series ASCII FORTRAN language. The ASCII FORTRAN compiler is a modern, state-of-the-art compiler which implements the ANSI FORTRAN 77 standard; this compiler is intended as a future replacement for the UNIVAC 1100 series FORTRAN V compiler. Rather than carry out a straightforward conversion of the FORTRAN V Mie scattering routine to ASCII FORTRAN, the code was completely rewritten in order to incorporate new ASCII FORTRAN language elements. The result is a more structured, modular, Mie scattering code which executes faster than the FORTRAN V code.
Simulating Initial and Progressive Failure of Open-Hole Composite Laminates under Tension
NASA Astrophysics Data System (ADS)
Guo, Zhangxin; Zhu, Hao; Li, Yongcun; Han, Xiaoping; Wang, Zhihua
2016-06-01
A finite element (FE) model is developed for the progressive failure analysis of fiber reinforced polymer laminates. The failure criterion for fiber and matrix failure is implemented in the FE code Abaqus using user-defined material subroutine UMAT. The gradual degradation of the material properties is controlled by the individual fracture energies of fiber and matrix. The failure and damage in composite laminates containing a central hole subjected to uniaxial tension are simulated. The numerical results show that the damage model can be used to accurately predicte the progressive failure behaviour both qualitatively and quantitatively.
Choi, Shi-Hoon; Kim, Dae-Wan; Yang, Hoe-Seok; Han, Seong-Ho; Yoon, Jeong Whan
2010-06-15
Planar anisotropy and cup-drawing behavior were investigated for high-strength steel sheets containing different volume fractions of martensite. Macrotexture analysis using XRD was conducted to capture the effect of crystallographic orientation on the planar anisotropy of high-strength steel sheets. A phenomenological yield function, Yld96, which accounts for the anisotropy of yield stress and r-values, was implemented into ABAQUS using the user subroutine UMAT. Cup drawing of high-strength steel sheets was simulated using the FEM code. The profiles of earing and thickness strain were compared with the experimentally measured results.
NASA Astrophysics Data System (ADS)
Choi, Shi-Hoon; Kim, Dae-Wan; Yang, Hoe-Seok; Han, Seong-Ho; Yoon, Jeong Whan
2010-06-01
Planar anisotropy and cup-drawing behavior were investigated for high-strength steel sheets containing different volume fractions of martensite. Macrotexture analysis using XRD was conducted to capture the effect of crystallographic orientation on the planar anisotropy of high-strength steel sheets. A phenomenological yield function, Yld96, which accounts for the anisotropy of yield stress and r-values, was implemented into ABAQUS using the user subroutine UMAT. Cup drawing of high-strength steel sheets was simulated using the FEM code. The profiles of earing and thickness strain were compared with the experimentally measured results.
NASA Astrophysics Data System (ADS)
Yi, Guilian; Sui, Yunkang; Du, Jiazheng
2011-06-01
To reduce vibration and noise, a damping layer and constraint layer are usually pasted on the inner surface of a gearbox thin shell, and their thicknesses are the main parameters in the vibration and noise reduction design. The normal acceleration of the point on the gearbox surface is the main index that can reflect the vibration and noise of that point, and the normal accelerations of different points can reflect the degree of the vibration and noise of the whole structure. The K-S function is adopted to process many points' normal accelerations as the comprehensive index of the vibration characteristics of the whole structure, and the vibration acceleration level is adopted to measure the degree of the vibration and noise. Secondary development of the Abaqus preprocess and postprocess on the basis of the Python scripting programming automatically modifies the model parameters, submits the job, and restarts the analysis totally, which avoids the tedious work of returning to the Abaqus/CAE for modifying and resubmitting and improves the speed of the preprocess and postprocess and the computational efficiency.
A Model for Simulating the Response of Aluminum Honeycomb Structure to Transverse Loading
NASA Technical Reports Server (NTRS)
Ratcliffe, James G.; Czabaj, Michael W.; Jackson, Wade C.
2012-01-01
A 1-dimensional material model was developed for simulating the transverse (thickness-direction) loading and unloading response of aluminum honeycomb structure. The model was implemented as a user-defined material subroutine (UMAT) in the commercial finite element analysis code, ABAQUS(Registered TradeMark)/Standard. The UMAT has been applied to analyses for simulating quasi-static indentation tests on aluminum honeycomb-based sandwich plates. Comparison of analysis results with data from these experiments shows overall good agreement. Specifically, analyses of quasi-static indentation tests yielded accurate global specimen responses. Predicted residual indentation was also in reasonable agreement with measured values. Overall, this simple model does not involve a significant computational burden, which makes it more tractable to simulate other damage mechanisms in the same analysis.
NASA Astrophysics Data System (ADS)
Cauble, R.; Rozmus, W.
1993-10-01
A FORTRAN subroutine for the calculation of the ac electrical conductivity in two-temperature, strongly coupled, overdense plasma is presented. The routine is the result of a model calculation based on classical transport theory with application to plasmas created by the interaction of short pulse lasers and solids. The formulation is analytic and the routine is self-contained.
ERIC Educational Resources Information Center
Gales, Larry
These materials were designed to be used by life science students for instruction in the application of physical theory to ecosystem operation. Most modules contain computer programs which are built around a particular application of a physical process. PRNT3D is a subroutine package which generates a variety of printed plot displays. The displays…
ERIC Educational Resources Information Center
Gales, Larry
This module is part of a series designed to be used by life science students for instruction in the application of physical theory to ecosystem operation. Most modules contain computer programs which are built around a particular application of a physical process. PLOT3D is a subroutine package which generates a variety of three dimensional hidden…
ERIC Educational Resources Information Center
Gales, Larry; Anderson, Lougenia
These materials were designed to be used by life science students for instruction in the application of physical theory to ecosystem operation. Most modules contain computer programs which are built around a particular application of a physical process. FFORM is a portable format-free input subroutine package which simplifies the input of values…
ERIC Educational Resources Information Center
Gales, Larry
This module is part of a series designed to be used by life science students for instruction in the application of physical theory to ecosystem operation. Most modules contain computer programs which are built around a particular application of a physical process. PLOT3D is a subroutine package which generates a variety of three-dimensional hidden…
ERIC Educational Resources Information Center
Gales, Larry
These materials were designed to be used by life science students for instruction in the application of physical theory to ecosystem operation. Most modules contain computer programs which are built around a particular application of a physical process. PRNT3D is a subroutine package which generates a variety of printer plot displays. The displays…
Documentation for subroutine REDUC3, an algorithm for the linear filtering of gridded magnetic data
Blakely, Richard J.
1977-01-01
Subroutine REDUC3 transforms a total field anomaly h1(x,y) , measured on a horizontal and rectangular grid, into a new anomaly h2(x,y). This new anomaly is produced by the same source as h1(x,y) , but (1) is observed at a different elevation, (2) has a source with a different direction of magnetization, and/or (3) has a different direction of residual field. Case 1 is tantamount to upward or downward continuation. Cases 2 and 3 are 'reduction to the pole', if the new inclinations of both the magnetization and regional field are 90 degrees. REDUC3 is a filtering operation applied in the wave-number domain. It first Fourier transforms h1(x,y) , multiplies by the appropriate filter, and inverse Fourier transforms the result to obtain h2(x,y). No assumptions are required about the shape of the source or how the intensity of magnetization varies within it.
EzGET: A library of FORTRAN subroutines to facilitate data retrieval
Taylor, K.E.
1996-04-01
The software described in this document is designed to facilitate retrieval of modeled and observed climate data stored in popular formats including DRS, net CDF, GrADS, and, if a control file is supplied, GRIB. You can specify how the data should be structured and whether it should undergo a grid transformation before you receive it, even when you know little about the structure of the stored data (i.e.. its dimension order, grid, and domain). The software is referred to here as EzGet (pronounced {open_quotes}easy-get{close_quotes}) and it comprise a set of subroutines that can be linked to any FORTRAN program. EzGet reads files through the cdunif interface which is available from the Program for Climate Model Diagnosis and Intercomparison (PCMDI), but use of EzGet does not require familiarity the cdunif. The main advantages of using this software instead of the lower level cdunif library include: Substantial error trapping capabilities and detailed error messages; Versatile capability of conveniently selecting data. from specified regions (e.g.. oceans, North America, all land areas north of 45 degrees latitude, etc.); Ability to map data to a new grid at the time it is retrieved by EzGet; Automatic creation of {open_quotes}weights{close_quotes} for use in subsequent averaging or masking of data; Increased control in specifying the domain. grid and structure of the retrieved data. Taken together these capabilities will simplify the process of writing programs for accessing data stored in different formats and structures, including all the observed data sets and the model output from various model intercomparison projects (AMIP, PMIP, CMIP, etc.) archived at PCMDI.
NASA Technical Reports Server (NTRS)
Ashbaugh, J. B.; Roland, D. P.; Laird, L. F.
1978-01-01
DSPOBJ is a FORTRAN subroutine to control the display of three-dimensional line networks on a stand-alone, general-purpose, interactive computer graphics system. The program controls the creation and manipulation of transformation matrices for the display and control of multiple sets of line networks. It provides advanced graphics features such as independent and global scaling, rotation and translation, cross-sectioning, reflection, and simultaneous display of four views.
NASA Astrophysics Data System (ADS)
Liu, P. F.; Yang, Y. H.; Gu, Z. P.; Zheng, J. Y.
2015-12-01
Interaction mechanism between the intralaminar damage and interlaminar delamination of composite laminates is always a challenging issue. It is important to consider the progressive failure and strain softening behaviors simultaneously during the damage modeling and numerical simulation of composites using FEA. This paper performs three-dimensional finite element analysis of the progressive failure and strain localization of composites using FEA. An intralaminar progressive failure model based on the strain components is proposed and the nonlinear cohesive model is used to predict the delamination growth. In particular, the nonlocal integral theory which introduces a length scale into the governing equations is used to regularize the strain localization problems of composite structures. Special finite element codes are developed using ABAQUS to predict the intralaminar and interlaminar damage evolution of composites simultaneously. The carbon fiber/epoxy composite laminates with a central hole demonstrates the developed theoretical models and numerical algorithm by discussing the effects of the mesh sizes and layups patterns. It is shown the strain localization problem can be well solved in the progressive failure analysis of composites when the energy dissipation due to the damage of the fiber, matrix and interface occurs at a relatively wide area.
NASA Technical Reports Server (NTRS)
Blakely, R. L.
1973-01-01
A G189A simulation of the shuttle orbiter EC/lSS was prepared and used to study payload support capabilities. Two master program libraries of the G189A computer program were prepared for the NASA/JSC computer system. Several new component subroutines were added to the G189A program library and many existing subroutines were revised to improve their capabilities. A number of special analyses were performed in support of a NASA/JSC shuttle orbiter EC/LSS payload support capability study.
Finite element based damage assessment of composite tidal turbine blades
NASA Astrophysics Data System (ADS)
Fagan, Edward M.; Leen, Sean B.; Kennedy, Ciaran R.; Goggins, Jamie
2015-07-01
With significant interest growing in the ocean renewables sector, horizontal axis tidal current turbines are in a position to dominate the marketplace. The test devices that have been placed in operation so far have suffered from premature failures, caused by difficulties with structural strength prediction. The goal of this work is to develop methods of predicting the damage level in tidal turbines under their maximum operating tidal velocity. The analysis was conducted using the finite element software package Abaqus; shell models of three representative tidal turbine blades are produced. Different construction methods will affect the damage level in the blade and for this study models were developed with varying hydrofoil profiles. In order to determine the risk of failure, a user material subroutine (UMAT) was created. The UMAT uses the failure criteria designed by Alfred Puck to calculate the risk of fibre and inter-fibre failure in the blades. The results show that degradation of the stiffness is predicted for the operating conditions, having an effect on the overall tip deflection. The failure criteria applied via the UMAT form a useful tool for analysis of high risk regions within the blade designs investigated.
NASA Astrophysics Data System (ADS)
Jin, BoCheng
2011-12-01
Organic and inorganic fiber reinforced composites with innumerable fiber orientation distributions and fiber geometries are abundantly available in several natural and synthetic structures. Inorganic glass fiber composites have been introduced to numerous applications due to their economical fabrication and tailored structural properties. Numerical characterization of such composite material systems is necessitated due to their intrinsic statistical nature, which renders extensive experimentation prohibitively time consuming and costly. To predict various mechanical behavior and characterizations of Uni-Directional Fiber Composites (UDFC) and Random Fiber Composites (RaFC), we numerically developed Representative Volume Elements (RVE) with high accuracy and efficiency and with complex fiber geometric representations encountered in uni-directional and random fiber networks. In this thesis, the numerical simulations of unidirectional RaFC fiber strand RVE models (VF>70%) are first presented by programming in ABAQUS PYTHON. Secondly, when the cross sectional aspect ratios (AR) of the second phase fiber inclusions are not necessarily one, various types of RVE models with different cross sectional shape fibers are simulated and discussed. A modified random sequential absorption algorithm is applied to enhance the volume fraction number (VF) of the RVE, which the mechanical properties represents the composite material. Thirdly, based on a Spatial Segment Shortest Distance (SSSD) algorithm, a 3-Dimentional RaFC material RVE model is simulated in ABAQUS PYTHON with randomly oriented and distributed straight fibers of high fiber aspect ratio (AR=100:1) and volume fraction (VF=31.8%). Fourthly, the piecewise multi-segments fiber geometry is obtained in MATLAB environment by a modified SSSD algorithm. Finally, numerical methods including the polynomial curve fitting and piecewise quadratic and cubic B-spline interpolation are applied to optimize the RaFC fiber geometries
Numerical Analysis of Deflections of Multi-Layered Beams
NASA Astrophysics Data System (ADS)
Biliński, Tadeusz; Socha, Tomasz
2015-03-01
The paper concerns the rheological bending problem of wooden beams reinforced with embedded composite bars. A theoretical model of the behaviour of a multi-layered beam is presented. The component materials of this beam are described with equations for the linear viscoelastic five-parameter rheological model. Two numerical analysis methods for the long-term response of wood structures are presented. The first method has been developed with SCILAB software. The second one has been developed with the finite element calculation software ABAQUS and user subroutine UMAT. Laboratory investigations were conducted on sample beams of natural dimensions in order to validate the proposed theoretical model and verify numerical simulations. Good agreement between experimental measurements and numerical results is observed.
Damage Simulation in Non-Crimp Fabric Composite Plates Subjected to Impact Loads
NASA Technical Reports Server (NTRS)
Satyanarayana, Arunkumar; Bogert, Philip B.; Aitharaju, Venkat; Aashat, Satvir; Kia, Hamid
2014-01-01
Progressive failure analysis (PFA) of non-crimp fabric (NCF) composite laminates subjected to low velocity impact loads was performed using the COmplete STress Reduction (COSTR) damage model implemented through VUMAT and UMAT41 user subroutines in the frame works of the commercial finite element programs ABAQUS/Explicit and LS-DYNA, respectively. To validate the model, low velocity experiments were conducted and detailed correlations between the predictions and measurements for both intra-laminar and inter-laminar failures were made. The developed material and damage model predicts the peak impact load and duration very close with the experimental results. Also, the simulation results of delamination damage between the ply interfaces, in-plane matrix damages and fiber damages were all in good agreement with the measurements from the non-destructive evaluation data.
NASA Astrophysics Data System (ADS)
Mamen, B.; Song, J.; Barriere, T.; Gelin, J.-C.
2013-05-01
Powder injection molding (PIM) is a suitable technology for manufacturing of complex shapes with tungsten powders and has a great potential in many applications. Sintering is one of the most important steps in Powder Injection Molding process. The sintering behaviour of tungsten injection moulded components, under pure hydrogen atmosphere at temperature up to 1700°C using fine 0.4μm and coarse powders 7.0 μm, is investigated by means of the beam bending and dilatometric tests in the Setaram{copyright, serif} analyser. To simulate the shrinkage and shape distortion of tungsten injection moulded components during the sintering process using finite element methods, viscoplastic constitutive law is implemented in ABAQUS software as user subroutine UMAT and incorporated with the identified parameters. Comparison between the numerical simulations results and experimental ones, in term of shrinkages and sintered densities, shows good agreement between the two.
NASA Astrophysics Data System (ADS)
Vidal-Sallé, Emmanuelle; Chassagne, Pierre
2007-06-01
This paper presents a nonlinear viscoelastic orthotropic constitutive equation applied to wood material. The proposed model takes into account mechanical and mechanosorptive creep via a 3D stress ratio and moisture change rate for a cylindrical orthotropic material. Orthotropic frame is based on the grain direction (L), radial (R) and hoop (T) directions, which are natural wood directions. Particular attention is taken to ensure the model to fulfill the necessary dissipation conditions. It is based on a rheological generalized Maxwell model with two elements in parallel in addition with a single linear spring taking into account the long term response. The proposed model is implemented in the finite element code ABAQUS/Standard® via a user subroutine UMAT and simple example is shown to demonstrate the capability of the proposed model. Future works would deal with damage and fracture prediction for wooden structures submitted to climate variations and mechanical loading.
User-Defined Material Model for Progressive Failure Analysis
NASA Technical Reports Server (NTRS)
Knight, Norman F. Jr.; Reeder, James R. (Technical Monitor)
2006-01-01
An overview of different types of composite material system architectures and a brief review of progressive failure material modeling methods used for structural analysis including failure initiation and material degradation are presented. Different failure initiation criteria and material degradation models are described that define progressive failure formulations. These progressive failure formulations are implemented in a user-defined material model (or UMAT) for use with the ABAQUS/Standard1 nonlinear finite element analysis tool. The failure initiation criteria include the maximum stress criteria, maximum strain criteria, the Tsai-Wu failure polynomial, and the Hashin criteria. The material degradation model is based on the ply-discounting approach where the local material constitutive coefficients are degraded. Applications and extensions of the progressive failure analysis material model address two-dimensional plate and shell finite elements and three-dimensional solid finite elements. Implementation details and use of the UMAT subroutine are described in the present paper. Parametric studies for composite structures are discussed to illustrate the features of the progressive failure modeling methods that have been implemented.
PC Basic Linear Algebra Subroutines
Energy Science and Technology Software Center (ESTSC)
1992-03-09
PC-BLAS is a highly optimized version of the Basic Linear Algebra Subprograms (BLAS), a standardized set of thirty-eight routines that perform low-level operations on vectors of numbers in single and double-precision real and complex arithmetic. Routines are included to find the index of the largest component of a vector, apply a Givens or modified Givens rotation, multiply a vector by a constant, determine the Euclidean length, perform a dot product, swap and copy vectors, andmore » find the norm of a vector. The BLAS have been carefully written to minimize numerical problems such as loss of precision and underflow and are designed so that the computation is independent of the interface with the calling program. This independence is achieved through judicious use of Assembly language macros. Interfaces are provided for Lahey Fortran 77, Microsoft Fortran 77, and Ryan-McFarland IBM Professional Fortran.« less
Micromechanics and constitutive modeling of connective soft tissues.
Fallah, A; Ahmadian, M T; Firozbakhsh, K; Aghdam, M M
2016-07-01
In this paper, a micromechanical model for connective soft tissues based on the available histological evidences is developed. The proposed model constituents i.e. collagen fibers and ground matrix are considered as hyperelastic materials. The matrix material is assumed to be isotropic Neo-Hookean while the collagen fibers are considered to be transversely isotropic hyperelastic. In order to take into account the effects of tissue structure in lower scales on the macroscopic behavior of tissue, a strain energy density function (SEDF) is developed for collagen fibers based on tissue hierarchical structure. Macroscopic response and properties of tissue are obtained using the numerical homogenization method with the help of ABAQUS software. The periodic boundary conditions and the proposed constitutive models are implemented into ABAQUS using the DISP and the UMAT subroutines, respectively. The existence of the solution and stable material behavior of proposed constitutive model for collagen fibers are investigated based on the poly-convexity condition. Results of the presented micromechanics model for connective tissues are compared and validated with available experimental data. Effects of geometrical and material parameters variation at microscale on macroscopic mechanical behavior of tissues are investigated. The results show that decrease in collagen content of the connective tissues like the tendon due to diseases leads 20% more stretch than healthy tissue under the same load which can results in connective tissue malfunction and hypermobility in joints. PMID:26807767
PROCESS SIMULATION OF COLD PRESSING OF ARMSTRONG CP-Ti POWDERS
Sabau, Adrian S; Gorti, Sarma B; Peter, William H; Yamamoto, Yukinori
2010-01-01
A computational methodology is presented for the process simulation of cold pressing of Armstrong CP-Ti Powders. The computational model was implemented in the commercial finite element program ABAQUSTM. Since the powder deformation and consolidation is governed by specific pressure-dependent constitutive equations, several solution algorithms were developed for the ABAQUS user material subroutine, UMAT. The solution algorithms were developed for computing the plastic strain increments based on an implicit integration of the nonlinear yield function, flow rule, and hardening equations that describe the evolution of the state variables. Since ABAQUS requires the use of a full Newton-Raphson algorithm for the stress-strain equations, an algorithm for obtaining the tangent/linearization moduli, which is consistent with the return-mapping algorithm, also was developed. Numerical simulation results are presented for the cold compaction of the Ti powders. Several simulations were conducted for cylindrical samples with different aspect ratios. The numerical simulation results showed that for the disk samples, the minimum von Mises stress was approximately half than its maximum value. The hydrostatic stress distribution exhibits a variation smaller than that of the von Mises stress. It was found that for the disk and cylinder samples the minimum hydrostatic stresses were approximately 23 and 50% less than its maximum value, respectively. It was also found that the minimum density was noticeably affected by the sample height.
NASA Astrophysics Data System (ADS)
Shrivastava, Sachin; Mohite, P. M.
2015-01-01
The minimization of weight and maximization of payload is an ever challenging design procedure for air vehicles. The present study has been carried out with an objective to redesign control surface of an advanced all-metallic fighter aircraft. In this study, the structure made up of high strength aluminum, titanium and ferrous alloys has been attempted to replace by carbon fiber composite (CFC) skin, ribs and stiffeners. This study presents an approach towards development of a methodology for optimization of first-ply failure index (FI) in unidirectional fibrous laminates using Genetic-Algorithms (GA) under quasi-static loading. The GAs, by the application of its operators like reproduction, cross-over, mutation and elitist strategy, optimize the ply-orientations in laminates so as to have minimum FI of Tsai-Wu first-ply failure criterion. The GA optimization procedure has been implemented in MATLAB and interfaced with commercial software ABAQUS using python scripting. FI calculations have been carried out in ABAQUS with user material subroutine (UMAT). The GA's application gave reasonably well-optimized ply-orientations combination at a faster convergence rate. However, the final optimized sequence of ply-orientations is obtained by tweaking the sequences given by GA's based on industrial practices and experience, whenever needed. The present study of conversion of an all metallic structure to partial CFC structure has led to 12% of weight reduction. Therefore, the approach proposed here motivates designer to use CFC with a confidence.
NASA Astrophysics Data System (ADS)
Settimi, Alessandro; Pietrella, Marco; Pezzopane, Michael; Zolesi, Bruno; Bianchi, Cesidio; Scotto, Carlo
2014-01-01
The present paper proposes to discuss the ionospheric absorption, assuming a quasi-flat layered ionospheric medium, with small horizontal gradients. A recent complex eikonal model (Settimi et al., 2013b) is applied, useful to calculate the absorption due to the ionospheric D-layer, which can be approximately characterized by a linearized analytical profile of complex refractive index, covering a short range of heights between h1 = 50 km and h2 = 90 km. Moreover, Settimi et al. (2013c) have already compared the complex eikonal model for the D-layer with the analytical Chapman's profile of ionospheric electron density; the corresponding absorption coefficient is more accurate than Rawer's theory (1976) in the range of middle critical frequencies. Finally, in this paper, the simple complex eikonal equations, in quasi-longitudinal (QL) approximation, for calculating the non-deviative absorption coefficient due to the propagation across the D-layer are encoded into a so called COMPLEIK (COMPLex EIKonal) subroutine of the IONORT (IONOspheric Ray-Tracing) program (Azzarone et al., 2012). The IONORT program, which simulates the three-dimensional (3-D) ray-tracing for high frequencies (HF) waves in the ionosphere, runs on the assimilative ISP (IRI-SIRMUP-P) discrete model over the Mediterranean area (Pezzopane et al., 2011). As main outcome of the paper, the simple COMPLEIK algorithm is compared to the more elaborate semi-empirical ICEPAC formula (Stewart, undated), which refers to various phenomenological parameters such as the critical frequency of E-layer. COMPLEIK is reliable just like the ICEPAC, with the advantage of being implemented more directly. Indeed, the complex eikonal model depends just on some parameters of the electron density profile, which are numerically calculable, such as the maximum height.
NASA Astrophysics Data System (ADS)
Settimi, Alessandro; Pietrella, Marco; Pezzopane, Michael; Zolesi, Bruno; Bianchi, Cesidio; Scotto, Carlo
2014-05-01
The present study proposes to discuss the ionospheric absorption, assuming a quasi-flat layered ionospheric medium, with small horizontal gradients. A recent complex eikonal model [Settimi et al., 2013b] is applied, useful to calculate the absorption due to the ionospheric D-layer, which can be approximately characterized by a linearized analytical profile of complex refractive index, covering a short range of heights between h1= 50 km and h2= 90 km. Moreover, Settimi et al. [2013c] have already compared the complex eikonal model for the D-layer with the analytical Chapman's profile of ionospheric electron density; the corresponding absorption coefficient is more accurate than Rawer's theory [1976] in the range of middle critical frequencies. Finally, in this study, the simple complex eikonal equations, in quasi-longitudinal (QL) approximation, for calculating the non-deviative absorption coefficient due to the propagation across the D-layer are encoded into a so called COMPLEIK (COMPLex EIKonal) subroutine of the IONORT (IONOspheric Ray-Tracing) program [Azzarone et al., 2012]. The IONORT program, which simulates the three-dimensional (3-D) ray-tracing for high frequencies (HF) waves in the ionosphere, runs on the assimilative ISP (IRI-SIRMUP-P) discrete model over the Mediterranean area [Pezzopane et al., 2011]. As main outcome of the study, the simple COMPLEIK algorithm is compared to the more elaborate semi-empirical ICEPAC formula [Stewart, undated], which refers to various phenomenological parameters such as the critical frequency of E-layer. COMPLEIK is reliable just like the ICEPAC, with the advantage of being implemented more directly. Indeed, the complex eikonal model depends just on some parameters of the electron density profile, which are numerically calculable, such as the maximum height.
NASA Technical Reports Server (NTRS)
Pineda, Evan, J.; Bednarcyk, Brett, A.; Arnold, Steven, M.
2012-01-01
A mesh objective crack band model is implemented in the generalized method of cells (GMC) micromechanics model to predict failure of a composite repeating unit cell (RUC). The micromechanics calculations are achieved using the MAC/GMC core engine within the ImMAC suite of micromechanics codes, developed at the NASA Glenn Research Center. The microscale RUC is linked to a macroscale Abaqus/Standard finite element model using the FEAMAC multiscale framework (included in the ImMAC suite). The effects of the relationship between the characteristic length of the finite element and the size of the microscale RUC on the total energy dissipation of the multiscale model are investigated. A simple 2-D composite square subjected to uniaxial tension is used to demonstrate the effects of scaling the dimensions of the RUC such that the length of the sides of the RUC are equal to the characteristic length of the finite element. These results are compared to simulations where the size of the RUC is fixed, independent of the element size. Simulations are carried out for a variety of mesh densities and element shapes, including square and triangular. Results indicate that a consistent size and shape must be used to yield preserve energy dissipation across the scales.
Li, Kai; Xin, Haitao; Zhao, Yanfang; Zhang, Zhiyuan; Wu, Yulu
2016-05-01
The objective of this study was to investigate the process of mandibular bone remodeling induced by implant-supported overdentures. computed tomography (CT) images were collected from edentulous patients to reconstruct the geometry of the mandibular bone and overdentures supported by implants. Based on the theory of strain energy density (SED), bone remodeling models were established using the user material subroutine (UMAT) in abaqus. The stress distribution in the mandible and bone density change was investigated to determine the effect of implant number on the remodeling of the mandibular bone. The results indicated that the areas where high Mises stress values were observed were mainly situated around the implants. The stress was concentrated in the distal neck region of the distal-most implants. With an increased number of implants, the biting force applied on the dentures was almost all taken up by implants. The stress and bone density in peri-implant bone increased. When the stress reached the threshold of remodeling, the bone density began to decrease. In the posterior mandible area, the stress was well distributed but increased with decreased implant numbers. Changes in bone density were not observed in this area. The computational results were consistent with the clinical data. The results demonstrate that the risk of bone resorption around the distal-most implants increases with increased numbers of implants and that the occlusal force applied to overdentures should be adjusted to be distributed more in the distal areas of the mandible. PMID:26963740
Analysis of interfacial debonding in shape memory alloy wire-reinforced composites
NASA Astrophysics Data System (ADS)
Miramini, A.; Kadkhodaei, M.; Alipour, A.; Mashayekhi, M.
2016-01-01
One of the common types of failure in shape memory alloy (SMA) wire-reinforced composites is interfacial debonding between the fiber and the matrix. In this paper, a three dimensional finite element model for an SMA wire-reinforced composite is developed based on cohesive zone modeling to predict interfacial debonding between the SMA wire and the surrounding matrix. The interfacial debonding is also experimentally investigated by conducting a number of pull-out tests on steel as well as Nitinol wires embedded in an epoxy matrix. To evaluate the presented method, the developed finite element analysis is employed to simulate a single wire pull-out test for ordinary (e.g. steel) wires. In order to simulate SMA wire pull-out, a 3D SMA constitutive model is implemented into the commercial finite element software ABAQUS using a user material subroutine (UMAT). An acceptable agreement is shown to exist between the theoretical results and the experimental data, indicating the efficiency of the proposed approach to model interfacial debonding in SMA wire-reinforced composites.
NASA Astrophysics Data System (ADS)
Piotrowski, Boris; Zineb, Tarak Ben; Patoor, Etienne; Eberhardt, Andre
Ni47Ti44Nb9 Shape Memory Alloys (SMA) are widely considered for tightening applications. The most common one are shape memory rings whose diameter decreases during heating. The alloy is composed of a NiTi matrix containing niobium precipitates. A specific thermomechanical treatment increases by more than one hundred degrees the transformation temperature hysteresis, what increases the range of use and improves the tightening efficiency. Tightening pressures exhibited by Ni47Ti44Nb9 rings with two various thicknesses are experimentally investigated. The test bed is composed of an Inconel 718 pipe instrumented by strain gauges sensors. Measured strains lead to the tightening pressure thanks to the large elastic resistance of Inconel. Evolutions with temperature are recorded. A thermo-mechanical constitutive law, specific for Ni47Ti44Nb9, has been developed. It is based on the Mori-Tanaka scale transition technique by considering the precipitates as elastic-plastic inclusions embedded in the SMA matrix. Its behavior is described by the Chemisky, Duval et al. constitutive model. The elastic-plastic constitutive law for inclusion is a classical one proposed by Simo and Hughes. The resulting effective law is implemented, and validated in ABAQUS via UMAT subroutine. The developed approach is adopted for the simulation of the experimental tests on Ni47Ti44Nb9 rings, and comparisons are performed.
Soare, S.; Cazacu, O.; Yoon, J. W.
2007-05-17
With few exceptions, non-quadratic homogeneous polynomials have received little attention as possible candidates for yield functions. One reason might be that not every such polynomial is a convex function. In this paper we show that homogeneous polynomials can be used to develop powerful anisotropic yield criteria, and that imposing simple constraints on the identification process leads, aposteriori, to the desired convexity property. It is shown that combinations of such polynomials allow for modeling yielding properties of metallic materials with any crystal structure, i.e. both cubic and hexagonal which display strength differential effects. Extensions of the proposed criteria to 3D stress states are also presented. We apply these criteria to the description of the aluminum alloy AA2090T3. We prove that a sixth order orthotropic homogeneous polynomial is capable of a satisfactory description of this alloy. Next, applications to the deep drawing of a cylindrical cup are presented. The newly proposed criteria were implemented as UMAT subroutines into the commercial FE code ABAQUS. We were able to predict six ears on the AA2090T3 cup's profile. Finally, we show that a tension/compression asymmetry in yielding can have an important effect on the earing profile.
K.R. Rajagopal; I.J. Rao
2006-05-05
The demand for increased efficiency of gas turbines used in power generation and aircraft applications has fueled research into advanced materials for gas turbine blades that can withstand higher temperatures in that they have excellent resistance to creep. The term ''Superalloys'' describes a group of alloys developed for applications that require high performance at elevated temperatures. Superalloys have a load bearing capacity up to 0.9 times their melting temperature. The objective of the investigation was to develop a thermodynamic model that can be used to describe the response of single crystal superalloys that takes into account the microstructure of the alloy within the context of a continuum model. Having developed the model, its efficacy was to be tested by corroborating the predictions of the model with available experimental data. Such a model was developed and it is implemented in the finite element software ABAQUS/STANDARD through a user subroutine (UMAT) so that the model can be used in realistic geometries that correspond to turbine blades.
Hydrostatic Stress Effect on the Yield Behavior of Inconel 100
NASA Technical Reports Server (NTRS)
Allen, Phillip A.; Wilson, Christopher D.
2003-01-01
Classical metal plasticity theory assumes that hydrostatic stress has negligible effect on the yield and postyield behavior of metals. Recent reexaminations of classical theory have revealed a significant effect of hydrostatic stress on the yield behavior of various geometries. Fatigue tests and nonlinear finite element analyses (FEA) of Inconel 100 (IN100) equal-arm bend specimens and new monotonic tests and nonlinear finite element analyses of IN100 smooth tension, smooth compression, and double-edge notch tension (DENT) test specimens have revealed the effect of internal hydrostatic tensile stresses on yielding. Nonlinear FEA using the von Mises (yielding is independent of hydrostatic stress) and the Drucker-Prager (yielding is linearly dependent on hydrostatic stress) yield functions were performed. A new FEA constitutive model was developed that incorporates a pressure-dependent yield function with combined multilinear kinematic and multilinear isotropic hardening using the ABAQUS user subroutine (UMAT) utility. In all monotonic tensile test cases, the von Mises constitutive model, overestimated the load for a given displacement or strain. Considering the failure displacements or strains for the DENT specimen, the Drucker-Prager FEM s predicted loads that were approximately 3% lower than the von Mises values. For the failure loads, the Drucker Prager FEM s predicted strains that were up to 35% greater than the von Mises values. Both the Drucker-Prager model and the von Mises model performed equally-well in simulating the equal-arm bend fatigue test.
Numerical Simulation of Time-dependent Spring-back Behavior for Aluminum Alloy 6022-T4 Sheet
NASA Astrophysics Data System (ADS)
Park, Taejoon; Chung, Kwansoo; Ryou, Hansun; Lee, Myoung-Gyu; Wagoner, R. H.
2010-06-01
In order to analyze the time-dependent spring-back behavior of the aluminum alloy 6022-T4 sheet, the viscoelastic/plastic constitutive law was applied by utilizing a linear viscoelastic/plastic model previously developed. As for the plastic deformation, the combined isotropic-kinematic hardening law was used to represent the Bauschinger behavior and transient hardening, while a non-quadratic anisotropic yield function, Yld2000-2d, was applied to account for anisotropic yield behavior. The numerical formulation was developed based on the incremental deformation viscoelastic/plasticity theory and then, the constitutive law was implemented into the ABAQUS/Standard commercial finite element program using the user-defined material subroutine, UMAT. The viscoelastic behavior was characterized by the creep test above the initial yield stress level, while anisotropic yielding and hardening parameters were obtained by the uniaxial tensile test. The constitutive law and the formulation were successfully validated for time-dependent springback in the draw-bend test.
NASA Astrophysics Data System (ADS)
Li, Wangnan; Cai, Hongneng; Li, Chao
2014-11-01
This paper deals with the characterization of the strength of the constituents of carbon fiber reinforced plastic laminate (CFRP), and a prediction of the static compressive strength of open-hole structure of polymer composites. The approach combined with non-linear analysis in macro-level and a linear elastic micromechanical failure analysis in microlevel (non-linear MMF) is proposed to improve the prediction accuracy. A face-centered cubic micromechanics model is constructed to analyze the stresses in fiber and matrix in microlevel. Non-interactive failure criteria are proposed to characterize the strength of fiber and matrix. The non-linear shear behavior of the laminate is studied experimentally, and a novel approach of cubic spline interpolation is used to capture significant non-linear shear behavior of laminate. The user-defined material subroutine UMAT for the non-linear share behavior is developed and combined in the mechanics analysis in the macro-level using the Abaqus Python codes. The failure mechanism and static strength of open-hole compressive (OHC) structure of polymer composites is studied based on non-linear MMF. The UTS50/E51 CFRP is used to demonstrate the application of theory of non-linear MMF.
Nonlinear, finite deformation, finite element analysis
NASA Astrophysics Data System (ADS)
Nguyen, Nhung; Waas, Anthony M.
2016-06-01
The roles of the consistent Jacobian matrix and the material tangent moduli, which are used in nonlinear incremental finite deformation mechanics problems solved using the finite element method, are emphasized in this paper, and demonstrated using the commercial software ABAQUS standard. In doing so, the necessity for correctly employing user material subroutines to solve nonlinear problems involving large deformation and/or large rotation is clarified. Starting with the rate form of the principle of virtual work, the derivations of the material tangent moduli, the consistent Jacobian matrix, the stress/strain measures, and the objective stress rates are discussed and clarified. The difference between the consistent Jacobian matrix (which, in the ABAQUS UMAT user material subroutine is referred to as DDSDDE) and the material tangent moduli ( C e ) needed for the stress update is pointed out and emphasized in this paper. While the former is derived based on the Jaumann rate of the Kirchhoff stress, the latter is derived using the Jaumann rate of the Cauchy stress. Understanding the difference between these two objective stress rates is crucial for correctly implementing a constitutive model, especially a rate form constitutive relation, and for ensuring fast convergence. Specifically, the implementation requires the stresses to be updated correctly. For this, the strains must be computed directly from the deformation gradient and corresponding strain measure (for a total form model). Alternatively, the material tangent moduli derived from the corresponding Jaumann rate of the Cauchy stress of the constitutive relation (for a rate form model) should be used. Given that this requirement is satisfied, the consistent Jacobian matrix only influences the rate of convergence. Its derivation should be based on the Jaumann rate of the Kirchhoff stress to ensure fast convergence; however, the use of a different objective stress rate may also be possible. The error associated
Micromechanics and constitutive models for soft active materials with phase evolution
NASA Astrophysics Data System (ADS)
Wang, Binglian
Soft active materials, such as shape memory polymers, liquid crystal elastomers, soft tissues, gels etc., are materials that can deform largely in response to external stimuli. Micromechanics analysis of heterogeneous materials based on finite element method is a typically numerical way to study the thermal-mechanical behaviors of soft active materials with phase evolution. While the constitutive models that can precisely describe the stress and strain fields of materials in the process of phase evolution can not be found in the databases of some commercial finite element analysis (FEA) tools such as ANSYS or Abaqus, even the specific constitutive behavior for each individual phase either the new formed one or the original one has already been well-known. So developing a computationally efficient and general three dimensional (3D) thermal-mechanical constitutive model for soft active materials with phase evolution which can be implemented into FEA is eagerly demanded. This paper first solved this problem theoretically by recording the deformation history of each individual phase in the phase evolution process, and adopted the idea of effectiveness by regarding all the new formed phase as an effective phase with an effective deformation to make this theory computationally efficient. A user material subroutine (UMAT) code based on this theoretical constitutive model has been finished in this work which can be added into the material database in Abaqus or ANSYS and can be easily used for most soft active materials with phase evolution. Model validation also has been done through comparison between micromechanical FEA and experiments on a particular composite material, shape memory elastomeric composite (SMEC) which consisted of an elastomeric matrix and the crystallizable fibre. Results show that the micromechanics and the constitutive models developed in this paper for soft active materials with phase evolution are completely relied on.
Enhanced Schapery Theory Software Development for Modeling Failure of Fiber-Reinforced Laminates
NASA Technical Reports Server (NTRS)
Pineda, Evan J.; Waas, Anthony M.
2013-01-01
Progressive damage and failure analysis (PDFA) tools are needed to predict the nonlinear response of advanced fiber-reinforced composite structures. Predictive tools should incorporate the underlying physics of the damage and failure mechanisms observed in the composite, and should utilize as few input parameters as possible. The purpose of the Enhanced Schapery Theory (EST) was to create a PDFA tool that operates in conjunction with a commercially available finite element (FE) code (Abaqus). The tool captures the physics of the damage and failure mechanisms that result in the nonlinear behavior of the material, and the failure methodology employed yields numerical results that are relatively insensitive to changes in the FE mesh. The EST code is written in Fortran and compiled into a static library that is linked to Abaqus. A Fortran Abaqus UMAT material subroutine is used to facilitate the communication between Abaqus and EST. A clear distinction between damage and failure is imposed. Damage mechanisms result in pre-peak nonlinearity in the stress strain curve. Four internal state variables (ISVs) are utilized to control the damage and failure degradation. All damage is said to result from matrix microdamage, and a single ISV marks the micro-damage evolution as it is used to degrade the transverse and shear moduli of the lamina using a set of experimentally obtainable matrix microdamage functions. Three separate failure ISVs are used to incorporate failure due to fiber breakage, mode I matrix cracking, and mode II matrix cracking. Failure initiation is determined using a failure criterion, and the evolution of these ISVs is controlled by a set of traction-separation laws. The traction separation laws are postulated such that the area under the curves is equal to the fracture toughness of the material associated with the corresponding failure mechanism. A characteristic finite element length is used to transform the traction-separation laws into stress-strain laws
Energy Science and Technology Software Center (ESTSC)
2005-03-07
Sandia NLVEabq is a FORTRAN subroutine that defines a user supplied material model for the ABAQUS commercial finite element code. It must be compiled and linked with the ABAQUS libraries under the user supplied subroutine option of the ABAQUS executable script. The subroutine is an implementation of Sandia National Laboratories nonlinear viscoelastic material model that is used to analyze the thermomechanicat behavior of polymers. It is thermodynamically consistent, incorporates finite strains and is applicable tomore » isotropic materials. The model is capable of predicting such diverse phenomena as stress relaxation, yielding, physical aging, thermal straining and enthalpy relaxation under arbitrary thermal and mechanical loading histories. This subroutine enables the ABAQUS finite element code to be sued for analyzing the performance of samples and structures that are made from polymers,« less
Shear degradation in fiber reinforced laminates due to matrix damage
NASA Astrophysics Data System (ADS)
Salavatian, Mohammedmahdi
relation between matrix damage variables do not sufficiently describe shear response. Therefore, a modified damage model for matrix failure was developed and implemented in ABAQUS using a UMAT subroutine.
NASA Astrophysics Data System (ADS)
Figiel, Łukasz; Dunne, Fionn P. E.; Buckley, C. Paul
2010-01-01
Layered-silicate nanoparticles offer a cost-effective reinforcement for thermoplastics. Computational modelling has been employed to study large deformations in layered-silicate/poly(ethylene terephthalate) (PET) nanocomposites near the glass transition, as would be experienced during industrial forming processes such as thermoforming or injection stretch blow moulding. Non-linear numerical modelling was applied, to predict the macroscopic large deformation behaviour, with morphology evolution and deformation occurring at the microscopic level, using the representative volume element (RVE) approach. A physically based elasto-viscoplastic constitutive model, describing the behaviour of the PET matrix within the RVE, was numerically implemented into a finite element solver (ABAQUS) using an UMAT subroutine. The implementation was designed to be robust, for accommodating large rotations and stretches of the matrix local to, and between, the nanoparticles. The nanocomposite morphology was reconstructed at the RVE level using a Monte-Carlo-based algorithm that placed straight, high-aspect ratio particles according to the specified orientation and volume fraction, with the assumption of periodicity. Computational experiments using this methodology enabled prediction of the strain-stiffening behaviour of the nanocomposite, observed experimentally, as functions of strain, strain rate, temperature and particle volume fraction. These results revealed the probable origins of the enhanced strain stiffening observed: (a) evolution of the morphology (through particle re-orientation) and (b) early onset of stress-induced pre-crystallization (and hence lock-up of viscous flow), triggered by the presence of particles. The computational model enabled prediction of the effects of process parameters (strain rate, temperature) on evolution of the morphology, and hence on the end-use properties.
Green-Naghdi rate of the Kirchhoff stress and deformation rate: the elasticity tensor
NASA Astrophysics Data System (ADS)
Bellini, Chiara; Federico, Salvatore
2015-06-01
The elasticity tensor providing the power-conjugation of the Green-Naghdi rate of the Kirchhoff stress and the deformation rate is required, e.g. by the commercially available Finite Element package ABAQUS/Standard for the material user subroutine UMAT, used to input material behaviours other than those included in the libraries of the package. This elasticity tensor had been studied in the literature, but its symmetries have only been briefly discussed, and only its component form in Cartesian coordinates was known. In this work, we derived a covariant, component-free expression of this elasticity tensor and thoroughly studied its symmetries. We found that, although symmetry on both pair of feet (indices) has been deemed to be desirable in the literature, the expression of the tensor available to-date in fact possesses only symmetry on the first pair of feet (indices), whereas the second pair lacks symmetry, and therefore carries a skew-symmetric contribution. This contribution is unnecessary, as it is automatically filtered in the contraction of the elasticity tensor with the symmetric deformation rate tensor. In order to avoid carrying this unnecessary skew-symmetric contribution in the computations, we employ a tensor identity that naturally symmetrises the second pair of feet of the elasticity tensor. We demonstrated the validity and robustness of the implementation of the user-defined material based on this tensor representation by simulating a benchmark problem consisting in biaxial tests of porcine and human atrial tissue, with material properties taken from previously performed experiments. We compared the results obtained by means of our user-defined material and those obtained through an equivalent built-in material, and obtained identical results.
Developing new bacteria subroutines in the SWAT model
Technology Transfer Automated Retrieval System (TEKTRAN)
Fecal bacteria observations from four different sites in Korea and the US demonstrate seasonal variability, showing a significant relationship with temperature (Figure 1); fecal indicator bacteria (FIB) concentrations are relatively higher in summer and lower in winter , including Stillwater river (...
Function algorithms for MPP scientific subroutines, volume 1
NASA Technical Reports Server (NTRS)
Gouch, J. G.
1984-01-01
Design documentation and user documentation for function algorithms for the Massively Parallel Processor (MPP) are presented. The contract specifies development of MPP assembler instructions to perform the following functions: natural logarithm; exponential (e to the x power); square root; sine; cosine; and arctangent. To fulfill the requirements of the contract, parallel array and solar implementations for these functions were developed on the PDP11/34 Program Development and Management Unit (PDMU) that is resident at the MPP testbed installation located at the NASA Goddard facility.
A generic applications subroutine library for the MPP
NASA Technical Reports Server (NTRS)
Gough, Michael L.; Wildenhain, W. David
1987-01-01
A new methodology to increase the utility of the Massively Parallel Processor (MPP) was developed, and is presented as an addition to the current methods of using the MPP. This methodology provides for the development of an MPP side abstraction layer that is callable from any host side high level language. Routines in the abstraction layer have the option of using a powerful software tool for accessing the stager as virtual memory. An additional abstraction layer that allows for remote access to the MPP via DECnet is discussed. This integrated approach to programming the MPP is a valuable tool for the implementation of interactive user driver systems that require the computational capabilities of the MPP as well as a controlled user view. It is expected that this methodology will be used to integrate the MPP into many such systems, and thus promote greater use of the MPP by scientific researchers who are accustomed to user friendly environments.
SCANEXE- EXAMINING THE SUBROUTINE STRUCTURE OF A VAX IMAGE
NASA Technical Reports Server (NTRS)
Scott, P. J.
1994-01-01
SCANEXE is a command for the DEC VAX used to scan a VMS executable image and print information about the routines it uses. Optionally, SCANEXE lists each routine, with its entry point, and how many times it is called, if at all. Information on the progress of the program will be optionally printed as it analyzes the various executable components. SCANEXE relies on debug records that are included by default in .EXE files. However, if an image is linked with the /NOTRACEBACK option (as are all system programs), then it cannot provide the necessary information. SCANEXE will only count the number of times it finds a statement calling each routine, which is not necessarily the same as the number of times that the routine would be called if the program were run. SCANEXE is written in C, FORTRAN 77, and Assembler for batch execution on the DEC VAX under VMS 4.X. It has a central memory requirement of 61952 bytes. This program was released in 1988.
Two subroutines used in processing of arrayed data files
NASA Astrophysics Data System (ADS)
Wu, Guang-Jie
Arrayed data files are commonly used in astronomy. It may be a text file compiled by the software "EDIT" in common use, or a table compiled by Microsoft WORD, Excel, or a FITS format etc. In the database of CDS (Centre de Données astronomiques de Strasbourg), there are over thousands star catalogues. Sometimes you may get a star catalogue from a colleague or friend of you, which may be done by multivarious computer software and may have peculiarity of sorts. Especially, the star catalogue had been compiled several years ago. You may often need to deal with such listed multidimensional data files, and you may need to make new listed data files by yourself. This processing for reduce-dimension or add-dimension, if it was a kind of row treatment, is very easy to do with some famous software like "EDIT". However, maybe you are facing a column treatment. It may bring some trouble to you. In some cases, a character "Tab" may exist in the file. Different software, even different printers made by a certain company, may give dissimilar treatment to the character "Tab". The problem is that a Table-key can denote a single space-key, or can be up to eight space-keys. Sometimes, it may not be easy to find a ready-made program in your hands. If this data file could be opened by the software "EDIT", two programs in this paper can help you to understand what happened there, and help you to solve the problem conveniently and easily. It includes to convert all of the Table-keys to be corresponding space-keys, to pick-up, delete, add blanks, or link two data files as two columns in one file.
Substructure based modeling of nickel single crystals cycled at low plastic strain amplitudes
NASA Astrophysics Data System (ADS)
Zhou, Dong
subroutine DISP and URDFIL of ABAQUS, respectively, while constitutive formulations of the FEM model are coded and implemented in UMAT. The results of the simulations are compared to experiments. This model verified the validity of Winter's two-phase model and Taylor's uniform stress assumption, explored substructure evolution and "intrinsic" behavior in substructures and successfully simulated the process of PSB band formation and propagation.
NASA Astrophysics Data System (ADS)
Arshadi, Amir
Image-based simulation of complex materials is a very important tool for understanding their mechanical behavior and an effective tool for successful design of composite materials. In this thesis an image-based multi-scale finite element approach is developed to predict the mechanical properties of asphalt mixtures. In this approach the "up-scaling" and homogenization of each scale to the next is critically designed to improve accuracy. In addition to this multi-scale efficiency, this study introduces an approach for consideration of particle contacts at each of the scales in which mineral particles exist. One of the most important pavement distresses which seriously affects the pavement performance is fatigue cracking. As this cracking generally takes place in the binder phase of the asphalt mixture, the binder fatigue behavior is assumed to be one of the main factors influencing the overall pavement fatigue performance. It is also known that aggregate gradation, mixture volumetric properties, and filler type and concentration can affect damage initiation and progression in the asphalt mixtures. This study was conducted to develop a tool to characterize the damage properties of the asphalt mixtures at all scales. In the present study the Viscoelastic continuum damage model is implemented into the well-known finite element software ABAQUS via the user material subroutine (UMAT) in order to simulate the state of damage in the binder phase under the repeated uniaxial sinusoidal loading. The inputs are based on the experimentally derived measurements for the binder properties. For the scales of mastic and mortar, the artificially 2-Dimensional images of mastic and mortar scales were generated and used to characterize the properties of those scales. Finally, the 2D scanned images of asphalt mixtures are used to study the asphalt mixture fatigue behavior under loading. In order to validate the proposed model, the experimental test results and the simulation results were
ANACAP-U software configuration and installation verification on the SECC
Marlow, R.S.
1994-09-27
ANACAP-U is a preprocessor, postprocessor, and concrete material subroutine used for the analysis of concrete structures. ANACAP-U functions in concert with the ABAQUS general purpose finite-element code. This document describes the Quality Assurance process for ANACAP-U version 9-2.2.7 as installed on the SECC.
NASA Astrophysics Data System (ADS)
Liu, Jian
obstacles. The thermal strength is obtained as a function of the activation energy of the GB obstacles and the activation length. The athermal part includes the strength due to the grain size dependence and the strength due to the dislocation density. The model parameters for two ufg/nc materials are determined by comparing experimental results to the one dimensional (1D) flow stress model using a Taylor's factor. The new constitutive model is incorporated into three dimensional crystal plasticity and the crystal plasticity model is implemented into a UMAT subroutine of ABAQUS finite element program. The uniaxial deformation responses of two ufg/nc materials are simulated using the previously determined model parameters. CPFEM simulations give flow stress predictions that are very close to 1D model correlations/predictions. It is a clear verification of a correct implementation of the new constitutive models into crystal plasticity modeling. With such a verification, the dislocation mechanism-based crystal plasticity UMAT is ready for more advanced simulation studies.
A Comparison of Sheet Forming Methods for 5754-O Aluminum Alloy
NASA Astrophysics Data System (ADS)
Venkatesan, Senthilkumar; Pourboghrat, Farhang; Carsley, John E.
2011-08-01
The goal of this research was to verify, through experimentation and numerical modeling, that the sheet hydroforming process is a suitable alternative to conventional forming methods such as stamping for 5754-O aluminum alloy sheets. Numerical analyses included implementation of a temperature-dependent anisotropic yield function (YLD 2000-2d) and corresponding forming limit diagram (FLD) into the commercial FEM code LS-Dyna as a user material subroutine (UMAT). The temperature-dependent material model was used in a coupled thermo-mechanical finite element model to assess the accuracy of the UMAT's ability to predict both forming and failure behavior of AA5754-O under various forming conditions [4]. Numerical investigations proved that counteracting pressure used in sheet hydroforming drastically improves the draw depth, irons out wrinkles and delays the onset of failure when compared to conventional forming processes.
FEAMAC/CARES Stochastic-Strength-Based Damage Simulation Tool for Ceramic Matrix Composites
NASA Technical Reports Server (NTRS)
Nemeth, Noel; Bednarcyk, Brett; Pineda, Evan; Arnold, Steven; Mital, Subodh; Murthy, Pappu; Bhatt, Ramakrishna
2016-01-01
Reported here is a coupling of two NASA developed codes: CARES (Ceramics Analysis and Reliability Evaluation of Structures) with the MAC/GMC (Micromechanics Analysis Code/ Generalized Method of Cells) composite material analysis code. The resulting code is called FEAMAC/CARES and is constructed as an Abaqus finite element analysis UMAT (user defined material). Here we describe the FEAMAC/CARES code and an example problem (taken from the open literature) of a laminated CMC in off-axis loading is shown. FEAMAC/CARES performs stochastic-strength-based damage simulation response of a CMC under multiaxial loading using elastic stiffness reduction of the failed elements.
NASA Technical Reports Server (NTRS)
Nemeth, Noel N.; Bednarcyk, Brett A.; Pineda, Evan; Arnold, Steven; Mital, Subodh; Murthy, Pappu; Walton, Owen
2015-01-01
Reported here is a coupling of two NASA developed codes: CARES (Ceramics Analysis and Reliability Evaluation of Structures) with the MACGMC composite material analysis code. The resulting code is called FEAMACCARES and is constructed as an Abaqus finite element analysis UMAT (user defined material). Here we describe the FEAMACCARES code and an example problem (taken from the open literature) of a laminated CMC in off-axis loading is shown. FEAMACCARES performs stochastic-strength-based damage simulation response of a CMC under multiaxial loading using elastic stiffness reduction of the failed elements.
NASA Technical Reports Server (NTRS)
Bogert, Philip B.; Satyanarayana, Arunkumar; Chunchu, Prasad B.
2006-01-01
Splitting, ultimate failure load and the damage path in center notched composite specimens subjected to in-plane tension loading are predicted using progressive failure analysis methodology. A 2-D Hashin-Rotem failure criterion is used in determining intra-laminar fiber and matrix failures. This progressive failure methodology has been implemented in the Abaqus/Explicit and Abaqus/Standard finite element codes through user written subroutines "VUMAT" and "USDFLD" respectively. A 2-D finite element model is used for predicting the intra-laminar damages. Analysis results obtained from the Abaqus/Explicit and Abaqus/Standard code show good agreement with experimental results. The importance of modeling delamination in progressive failure analysis methodology is recognized for future studies. The use of an explicit integration dynamics code for simple specimen geometry and static loading establishes a foundation for future analyses where complex loading and nonlinear dynamic interactions of damage and structure will necessitate it.
Multiple IMU system test plan, volume 4. [subroutines for space shuttle requirements
NASA Technical Reports Server (NTRS)
Landey, M.; Vincent, K. T., Jr.; Whittredge, R. S.
1974-01-01
Operating procedures for this redundant system are described. A test plan is developed with two objectives. First, performance of the hardware and software delivered is demonstrated. Second, applicability of multiple IMU systems to the space shuttle mission is shown through detailed experiments with FDI algorithms and other multiple IMU software: gyrocompassing, calibration, and navigation. Gimbal flip is examined in light of its possible detrimental effects on FDI and navigation. For Vol. 3, see N74-10296.
Computer subroutine ISUDS accurately solves large system of simultaneous linear algebraic equations
NASA Technical Reports Server (NTRS)
Collier, G.
1967-01-01
Computer program, an Iterative Scheme Using a Direct Solution, obtains double precision accuracy using a single-precision coefficient matrix. ISUDS solves a system of equations written in matrix form as AX equals B, where A is a square non-singular coefficient matrix, X is a vector, and B is a vector.
Improving frost-simulation subroutines of the Water Erosion Prediction Project (WEPP) model
Technology Transfer Automated Retrieval System (TEKTRAN)
Erosion models play an important role in assessing the influence of human activities on the environment. For cold areas, adequate frost simulation is crucial for predicting surface runoff and water erosion. The Water Erosion Prediction Project (WEPP) model, physically-based erosion-prediction softwa...
LASPE: a subroutine for generating straggling distributions for positrons and electrons
NASA Astrophysics Data System (ADS)
Heddle, D. P.; Maximon, Leonard C.
1992-05-01
Computer codes used for analysis of data from high energy electron scattering experiments generally use the Rutherford cross-section based distribution derived by Landau to calculate the energy lost by electrons due to straggling. We have developed a FORTRAN program which evaluates straggling distributions incorporating Møller and Bhabha cross-sections. In e - scattering analysis, this program can be used to evaluate the precision of existing Rutherford-based distributions. In addition, the calculation of the e + straggling distribution is relevant to the analysis of experiments such as those investigating dispersive effects in nuclear electromagnetic processes by comparing results obtained from e - and e + scattering from identical nuclei. In addition to a full straggling distribution, the output includes the parameters which characterize the distribution as well as a table of integrals of the distribution.
NASA Technical Reports Server (NTRS)
Mall, G. H.
1983-01-01
Modifications to a multi-degree-of-freedom flexible aircraft take-off and landing analysis (FATOLA) computer program, including a provision for actively controlled landing gears to expand the programs simulation capabilities, are presented. Supplemental instructions for preparation of data and for use of the modified program are included.
FORTRAN subroutines for out-of-core solutions of large complex linear systems
NASA Technical Reports Server (NTRS)
Yip, E. L.
1979-01-01
The design and usage of two main subprograms using direct methods to solve large linear complex systems, of the form Ax = b, whose coeffficient matrices are too large to be stored in core are described. The first main subprogram is for systems whose coefficient matrices are of a particular sparse structure, namely, the matrix A can be written in the form B + D, where B is a block-banded system, and D has only a few columns of nonzeros. Key elements of the algorithms used in the subprograms include: the data structure, the strategy for preserving numerical stability, the adaptability of the algorithms for dense systems as well as for block-profile systems.
Calculation of stellar structure. IV. Results using a detailed energy generation subroutine.
NASA Astrophysics Data System (ADS)
Rouse, C. A.
1995-12-01
The results from two solar model calculations using the "energy.for" energy generation and neutrino flux code (Bahcall & Pinsonneault 1992) are presented. The models of the present Sun were generated using the program described in the first three papers of this series and using only the helium abundance profile from the Bahcall & Ulrich (1988) (BU) standard model in the present model structure calculations. One model is a simulation of the BU model and yields a ^37^Cl solar neutrino counting rate of 7.0SNU (compared to 7.9SNU for the BU model) and a ^71^Ga neutrino experiment counting rate between 112 and 137SNU (compared to 132SNU for the BU model). The second model has a postulated small high-Z core (Rouse 1983) and yields a ^37^Cl neutrino experiment counting rate of 2.45SNU that is within one sigma of the Homestake Collaboration observed rate of (2.55+/-0.25)SNU (see Parke 1995). It yields a ^71^Ga neutrino experiment counting rate between 89 and 103SNU that is within one sigma of the GALLEX Collaboration neutrino experiment observed rate of (79+/-12)SNU (see Parke 1995). The theoretical ^8^B solar neutrino flux and the observed Kamiokande ^8^B flux (Hirata et al. 1989) are discussed regarding the puzzle of explaining both the chlorine experiment results and the Kamiokande results. The modification of the energy.for code for use in the current Rouse program is described. Consistency of a high-Z core solar model with theories of star formation from pre-stellar nuclei (Krat 1952; Urey 1956; Huang 1957) is suggested.
CODAP: Programmer Notes for the Subroutine Library on the Univac 1108.
ERIC Educational Resources Information Center
Weissmuller, Johnny J.; And Others
The Comprehensive Occupational Data Analysis Programs (CODAP) package is a highly interactive and efficient system of computer routines for analyzing, organizing, and reporting occupational information. Since its inception in 1960, CODAP has grown in tandem with advances in job analysis methodology and is now capable of answering most of the wide…
Creep failure of a reactor pressure vessel lower head under severe accident conditions
Pilch, M.M.; Ludwigsen, J.S.; Chu, T.Y.; Rashid, Y.R.
1998-08-01
A severe accident in a nuclear power plant could result in the relocation of large quantities of molten core material onto the lower head of he reactor pressure vessel (RPV). In the absence of inherent cooling mechanisms, failure of the RPV ultimately becomes possible under the combined effects of system pressure and the thermal heat-up of the lower head. Sandia National Laboratories has performed seven experiments at 1:5th scale simulating creep failure of a RPV lower head. This paper describes a modeling program that complements the experimental program. Analyses have been performed using the general-purpose finite-element code ABAQUS-5.6. In order to make ABAQUS solve the specific problem at hand, a material constitutive model that utilizes temperature dependent properties has been developed and attached to ABAQUS-executable through its UMAT utility. Analyses of the LHF-1 experiment predict instability-type failure. Predicted strains are delayed relative to the observed strain histories. Parametric variations on either the yield stress, creep rate, or both (within the range of material property data) can bring predictions into agreement with experiment. The analysis indicates that it is necessary to conduct material property tests on the actual material used in the experimental program. The constitutive model employed in the present analyses is the subject of a separate publication.
Effects of Injected CO2 on Geomechanical Properties Due to Mineralogical Changes
NASA Astrophysics Data System (ADS)
Nguyen, B. N.; Hou, Z.; Bacon, D. H.; Murray, C. J.; White, J. A.
2013-12-01
Long-term injection and storage of CO2 in deep underground reservoirs may significantly modify the geomechanical behavior of rocks since CO2 can react with the constituent phases of reservoir rocks and modify their composition. This can lead to modifications of their geomechanical properties (i.e., elastic moduli, Biot's coefficients, and permeability). Modifications of rock geomechanical properties have important consequences as these directly control stress and strain distributions, affect conditions for fracture initiation and development and/or fault healing. This paper attempts to elucidate the geochemical effects of CO2 on geomechanical properties of typical reservoir rocks by means of numerical analyses using the STOMP-ABAQUS sequentially coupled simulator that includes the capability to handle geomechanics and the reactive transport of CO2 together with a module (EMTA) to compute the homogenized rock poroelastic properties as a function of composition changes. EMTA, a software module developed at PNNL, implements the standard and advanced Eshelby-Mori-Tanaka approaches to compute the thermoelastic properties of composite materials. In this work, EMTA will be implemented in the coupled STOMP-ABAQUS simulator as a user subroutine of ABAQUS and used to compute local elastic stiffness based on rock composition. Under the STOMP-ABAQUS approach, STOMP models are built to simulate aqueous and CO2 multiphase fluid flows, and relevant chemical reactions of pore fluids with minerals in the reservoirs. The ABAQUS models then read STOMP output data for cell center coordinates, gas pressures, aqueous pressures, temperatures, saturations, constituent volume fractions, as well as permeability and porosity that are affected by chemical reactions. These data are imported into ABAQUS meshes using a mapping procedure developed for the exchange of data between STOMP and ABAQUS. Constitutive models implemented in ABAQUS via user subroutines then compute stiffness, stresses
NASA Astrophysics Data System (ADS)
Deng, Bin; Shen, ZhiBin; Duan, JingBo; Tang, GuoJin
2014-05-01
This paper studies the damage-viscoelastic behavior of composite solid propellants of solid rocket motors (SRM). Based on viscoelastic theories and strain equivalent hypothesis in damage mechanics, a three-dimensional (3-D) nonlinear viscoelastic constitutive model incorporating with damage is developed. The resulting viscoelastic constitutive equations are numerically discretized by integration algorithm, and a stress-updating method is presented by solving nonlinear equations according to the Newton-Raphson method. A material subroutine of stress-updating is made up and embedded into commercial code of Abaqus. The material subroutine is validated through typical examples. Our results indicate that the finite element results are in good agreement with the analytical ones and have high accuracy, and the suggested method and designed subroutine are efficient and can be further applied to damage-coupling structural analysis of practical SRM grain.
Gan, Yixiang; Kamlah, Marc
2008-07-01
In this investigation, a thermo-mechanical model of pebble beds is adopted and developed based on experiments by Dr. Reimann at Forschungszentrum Karlsruhe (FZK). The framework of the present material model is composed of a non-linear elastic law, the Drucker-Prager-Cap theory, and a modified creep law. Furthermore, the volumetric inelastic strain dependent thermal conductivity of beryllium pebble beds is taken into account and full thermo-mechanical coupling is considered. Investigation showed that the Drucker-Prager-Cap model implemented in ABAQUS can not fulfill the requirements of both the prediction of large creep strains and the hardening behaviour caused by creep, which are of importance with respect to the application of pebble beds in fusion blankets. Therefore, UMAT (user defined material's mechanical behaviour) and UMATHT (user defined material's thermal behaviour) routines are used to re-implement the present thermo-mechanical model in ABAQUS. An elastic predictor radial return mapping algorithm is used to solve the non-associated plasticity iteratively, and a proper tangent stiffness matrix is obtained for cost-efficiency in the calculation. An explicit creep mechanism is adopted for the prediction of time-dependent behaviour in order to represent large creep strains in high temperature. Finally, the thermo-mechanical interactions are implemented in a UMATHT routine for the coupled analysis. The oedometric compression tests and creep tests of pebble beds at different temperatures are simulated with the help of the present UMAT and UMATHT routines, and the comparison between the simulation and the experiments is made. (authors)
Deformation and failure of bulk metallic glasses under different initial temperatures
NASA Astrophysics Data System (ADS)
Li, J. C.; Chen, X. W.; Huang, F. L.
2015-09-01
Based on the coupled thermo-mechanical model, a constitutive model for bulk metallic glasses (BMGs), which is generalized to the multi-axial stress state and considers the effects of free volume, heat and hydrostatic stress, has been modified in the present paper. Besides, a failure criterion of critical free volume concentration is introduced based on the coalescence mechanism of free volume. The constitutive model as well as the failure criterion is implemented into the LS-DYNA commercial software by user material subroutine (UMAT). Then FEM simulations for different initial material temperatures are conducted and the evolutions of material parameter as well as corresponding macroscopic mechanical behaviour of material are analyzed. Relative analysis shows that the initial material temperature significantly affects the deformation and failure of material.
Huang, Huixiang; Tang, Wencheng; Yan, Bin; Wu, Bin; Cao, Dan
2016-01-01
The V-W exponential hyperelastic model is adopted to describe the instantaneous elastic response of the periodontal ligament (PDL). The general theoretical framework of constitutive modeling is described based on nonlinear continuum mechanics, and the elasticity tensor used to develop UMAT subroutine is formulated. Nanoindentation experiment is performed to characterize mechanical properties of an adult pig PDL specimen. Then the experiment is simulated by using the finite element (FE) analysis. Meanwhile, the optimized material parameters are identified by the inverse FE method. The good agreement between the simulated results and experimental data demonstrates that the V-W model is capable of describing the mechanical behavior of the PDL. Therefore, the model and its implementation into FE code are validated. By using the model, we simulate the tooth movement under orthodontic loading to predict the mechanical responses of the PDL. The results show that local concentrations of stress and strain in the PDL are found. PMID:25648914
Warm Forming of Aluminum Alloys using a Coupled Thermo-Mechanical Anisotropic Material Model
Abedrabbo, Nader; Pourboghrat, Farhang; Carsley, John E.
2005-08-05
Temperature-dependant anisotropic material models for two types of automotive aluminum alloys (5754-O and 5182-O) were developed and implemented in LS-Dyna as a user material subroutine (UMAT) for coupled thermo-mechanical finite element analysis (FEA) of warm forming of aluminum alloys. The anisotropy coefficients of the Barlat YLD2000 plane stress yield function for both materials were calculated for the range of temperatures 25 deg. C-260 deg. C. Curve fitting was used to calculate the anisotropy coefficients of YLD2000 and the flow stress as a function of temperature. This temperature-dependent material model was successfully applied to the coupled thermo-mechanical analysis of stretching of aluminum sheets and results were compared with experiments.
Warm Forming of Aluminum Alloys using a Coupled Thermo-Mechanical Anisotropic Material Model
NASA Astrophysics Data System (ADS)
Abedrabbo, Nader; Pourboghrat, Farhang; Carsley, John E.
2005-08-01
Temperature-dependant anisotropic material models for two types of automotive aluminum alloys (5754-O and 5182-O) were developed and implemented in LS-Dyna as a user material subroutine (UMAT) for coupled thermo-mechanical finite element analysis (FEA) of warm forming of aluminum alloys. The anisotropy coefficients of the Barlat YLD2000 plane stress yield function for both materials were calculated for the range of temperatures 25°C-260°C. Curve fitting was used to calculate the anisotropy coefficients of YLD2000 and the flow stress as a function of temperature. This temperature-dependent material model was successfully applied to the coupled thermo-mechanical analysis of stretching of aluminum sheets and results were compared with experiments.
Salajegheh, Nima; Abedrabbo, Nader; Pourboghrat, Farhang
2005-08-05
An efficient integration algorithm for continuum damage based elastoplastic constitutive equations is implemented in LS-DYNA. The isotropic damage parameter is defined as the ratio of the damaged surface area over the total cross section area of the representative volume element. This parameter is incorporated into the integration algorithm as an internal variable. The developed damage model is then implemented in the FEM code LS-DYNA as user material subroutine (UMAT). Pure stretch experiments of a hemispherical punch are carried out for copper sheets and the results are compared against the predictions of the implemented damage model. Evaluation of damage parameters is carried out and the optimized values that correctly predicted the failure in the sheet are reported. Prediction of failure in the numerical analysis is performed through element deletion using the critical damage value. The set of failure parameters which accurately predict the failure behavior in copper sheets compared to experimental data is reported as well.
NASA Astrophysics Data System (ADS)
Salajegheh, Nima; Abedrabbo, Nader; Pourboghrat, Farhang
2005-08-01
An efficient integration algorithm for continuum damage based elastoplastic constitutive equations is implemented in LS-DYNA. The isotropic damage parameter is defined as the ratio of the damaged surface area over the total cross section area of the representative volume element. This parameter is incorporated into the integration algorithm as an internal variable. The developed damage model is then implemented in the FEM code LS-DYNA as user material subroutine (UMAT). Pure stretch experiments of a hemispherical punch are carried out for copper sheets and the results are compared against the predictions of the implemented damage model. Evaluation of damage parameters is carried out and the optimized values that correctly predicted the failure in the sheet are reported. Prediction of failure in the numerical analysis is performed through element deletion using the critical damage value. The set of failure parameters which accurately predict the failure behavior in copper sheets compared to experimental data is reported as well.
BOOK REVIEW: Introduction to Computational Plasticity
NASA Astrophysics Data System (ADS)
Hartley, P.
2006-04-01
Jaumann rate of stress. It is tempting here to suggest that a more complete description should be given together with other measures of strain and stress, of which there are several, but there would be a danger of changing the book from an `introduction' to a more comprehensive text, and examples of such exist already. Chapter four begins the process of developing the plasticity theories into a form suitable for inclusion in the finite-element method. The starting point is Hamilton's principle for equilibrium of a dynamic system. A very brief introduction to the finite-element method is then given, followed by the finite-element equilibrium equations and a description of how they are incorporated into Hamilton's principle. A useful clarification is provided by comparing tensor notation and the form normally used in finite-element expressions, i.e. Voigt notation. The chapter concludes with a brief overview of implicit integration methods, i.e. tangent stiffness, initial tangent stiffness and Newton Raphson. Chapter five deals with the more specialized topic of implicit and explicit integration of von Mises plasticity. One of the techniques described is the radial-return method which ensures that the stresses at the end of an increment of deformation always lie on the expanded yield surface. Although this method guarantees a solution it may not always be the most accurate for large deformation, this is one area where reference to alternative methods would have been a helpful addition. Chapter six continues with further detail of how the plasticity models may be incorporated into finite-element codes, with particular reference to the Abaqus package and the use of user-defined subroutines, introduced via a `UMAT' subroutine. This completes part I of the book. Part II focuses on plasticity models, each chapter dealing with a particular process or material model. For example, chapter seven deals with superplasticity, chapter eight with porous plasticity, chapter nine with
Advanced finite element analysis of L4-L5 implanted spine segment
NASA Astrophysics Data System (ADS)
Pawlikowski, Marek; Domański, Janusz; Suchocki, Cyprian
2015-09-01
In the paper finite element (FE) analysis of implanted lumbar spine segment is presented. The segment model consists of two lumbar vertebrae L4 and L5 and the prosthesis. The model of the intervertebral disc prosthesis consists of two metallic plates and a polyurethane core. Bone tissue is modelled as a linear viscoelastic material. The prosthesis core is made of a polyurethane nanocomposite. It is modelled as a non-linear viscoelastic material. The constitutive law of the core, derived in one of the previous papers, is implemented into the FE software Abaqus®. It was done by means of the User-supplied procedure UMAT. The metallic plates are elastic. The most important parts of the paper include: description of the prosthesis geometrical and numerical modelling, mathematical derivation of stiffness tensor and Kirchhoff stress and implementation of the constitutive model of the polyurethane core into Abaqus® software. Two load cases were considered, i.e. compression and stress relaxation under constant displacement. The goal of the paper is to numerically validate the constitutive law, which was previously formulated, and to perform advanced FE analyses of the implanted L4-L5 spine segment in which non-standard constitutive law for one of the model materials, i.e. the prosthesis core, is implemented.
Progressive Failure And Life Prediction of Ceramic and Textile Composites
NASA Technical Reports Server (NTRS)
Xue, David Y.; Shi, Yucheng; Katikala, Madhu; Johnston, William M., Jr.; Card, Michael F.
1998-01-01
An engineering approach to predict the fatigue life and progressive failure of multilayered composite and textile laminates is presented. Analytical models which account for matrix cracking, statistical fiber failures and nonlinear stress-strain behavior have been developed for both composites and textiles. The analysis method is based on a combined micromechanics, fracture mechanics and failure statistics analysis. Experimentally derived empirical coefficients are used to account for the interface of fiber and matrix, fiber strength, and fiber-matrix stiffness reductions. Similar approaches were applied to textiles using Repeating Unit Cells. In composite fatigue analysis, Walker's equation is applied for matrix fatigue cracking and Heywood's formulation is used for fiber strength fatigue degradation. The analysis has been compared with experiment with good agreement. Comparisons were made with Graphite-Epoxy, C/SiC and Nicalon/CAS composite materials. For textile materials, comparisons were made with triaxial braided and plain weave materials under biaxial or uniaxial tension. Fatigue predictions were compared with test data obtained from plain weave C/SiC materials tested at AS&M. Computer codes were developed to perform the analysis. Composite Progressive Failure Analysis for Laminates is contained in the code CPFail. Micromechanics Analysis for Textile Composites is contained in the code MicroTex. Both codes were adapted to run as subroutines for the finite element code ABAQUS and CPFail-ABAQUS and MicroTex-ABAQUS. Graphic user interface (GUI) was developed to connect CPFail and MicroTex with ABAQUS.
An explicit model of expanding cylindrical shells subjected to high explosive detonations
Martineau, R.L.; Prime, M.B.; Anderson, C.A.; Smith, F.W.
1999-04-01
A viscoplastic constitutive model was formulated to model the high strain-rate expansion of thin cylindrical shells subjected to internal explosive detonations. This model provides insight into the development of plastic instabilities, which occur on the surface of the shells prior to failure. The effects of shock heating and damage in the form of microvoid nucleation, growth, and coalescence were incorporated using the Johnson-Cook strength model with the Mie-Grueneisen equation of state and a modified Gurson yield surface. This model was implemented into ABAQUS/Explicit as a user material subroutine. A cylindrical copper shell was modeled using both axisymmetric and plane strain elements. The high explosive material inside of the cylinder was simulated using the high explosive burn model in ABAQUS/Explicit. Two experiments were conducted involving explosive-filled, copper cylinders and good agreement was obtained between the numerical results and experimental data.
NASA Technical Reports Server (NTRS)
Schneider, Steven J.
2015-01-01
Heat transfer correlations of data on flat plates are used to explore the parameters in the Coolit program used for calculating the quantity of cooling air for controlling turbine blade temperature. Correlations for both convection and film cooling are explored for their relevance to predicting blade temperature as a function of a total cooling flow which is split between external film and internal convection flows. Similar trends to those in Coolit are predicted as a function of the percent of the total cooling flow that is in the film. The exceptions are that no film or 100 percent convection is predicted to not be able to control blade temperature, while leaving less than 25 percent of the cooling flow in the convection path results in nearing a limit on convection cooling as predicted by a thermal effectiveness parameter not presently used in Coolit.
A 3D moisture-stress FEM analysis for time dependent problems in timber structures
NASA Astrophysics Data System (ADS)
Fortino, Stefania; Mirianon, Florian; Toratti, Tomi
2009-11-01
This paper presents a 3D moisture-stress numerical analysis for timber structures under variable humidity and load conditions. An orthotropic viscoelastic-mechanosorptive material model is specialized on the basis of previous models. Both the constitutive model and the equations needed to describe the moisture flow across the structure are implemented into user subroutines of the Abaqus finite element code and a coupled moisture-stress analysis is performed for several types of mechanical loads and moisture changes. The presented computational approach is validated by analyzing some wood tests described in the literature and comparing the computational results with the reported experimental data.
Ballistic impact behaviour of woven fabric composite: Finite element analysis and experiments
NASA Astrophysics Data System (ADS)
Phadnis, V. A.; Pandya, K. S.; Naik, N. K.; Roy, A.; Silberschmidt, V. V.
2013-07-01
A mechanical behaviour of plain-weave E-glass fabric/epoxy laminate composite plate exposed to ballistic impact is studied using a finite-element (FE) code Abaqus/Explicit. A ply-level FE model is developed, where a fabric-reinforced ply is modelled as a homogeneous orthotropic elastic material with potential to sustain progressive stiffness degradation due to fiber/matrix cracking, and plastic deformation under shear loading. The model is implemented as a VUMAT user subroutine. Ballistic experiments were carried out to validate the FE model. A parametric study for varying panel thickness is performed to compare impact resistance of the studied composite.
Numerical implementation of energy-based models in finite element analysis
NASA Astrophysics Data System (ADS)
Chattonjai, Piyachat
2016-06-01
Soil is one of the most complex materials including several characteristics which are not only effect on stress-strain relationship but also volume changed such as contraction and dilation. Those characteristics depend on so many factors such as stress history, drained condition, current effective stress state, stress paths as well as void ratio, etc. In finite element analysis, the relevant constitutive model which includes relevant factors as mentioned above is one of the main key that will provide the accurate predicting of strength and deformation characteristic of geotechnical structure. For modern finite element program, the user-defined material subroutines have been provided when the material models included in the material library could not accurately predict the rather complex behavior of material. The objective of this study is to implement the elasto-plastic work-hardening-softening constitutive model into ABAQUS via VUMAT subroutine. The simulated results were verified by the experimental results of Toyoura sand under plane strain condition.
Kammoun, S.; Brassart, L.; Doghri, I.; Delannay, L.; Robert, G.
2011-05-04
A micromechanical damage modeling approach is presented to predict the overall elasto-plastic behavior and damage evolution in short fiber reinforced composite materials. The practical use of the approach is for injection molded thermoplastic parts reinforced with short glass fibers. The modeling is proceeded as follows. The representative volume element is decomposed into a set of pseudograins, the damage of which affects progressively the overall stiffness and strength up to total failure. Each pseudograin is a two-phase composite with aligned inclusions having same aspect ratio. A two-step mean-field homogenization procedure is adopted. In the first step, the pseudograins are homogenized individually according to the Mori-Tanaka scheme. The second step consists in a self-consistent homogenization of homogenized pseudograins. An isotropic damage model is applied at the pseudograin level. The model is implemented as a UMAT in the finite element code ABAQUS. Model is shown to reproduce the strength and the anisotropy (Lankford coefficient) during uniaxial tensile tests on samples cut under different directions relative to the injection flow direction.
NASA Technical Reports Server (NTRS)
Utku, S.
1969-01-01
A general purpose digital computer program for the in-core solution of linear equilibrium problems of structural mechanics is documented. The program requires minimum input for the description of the problem. The solution is obtained by means of the displacement method and the finite element technique. Almost any geometry and structure may be handled because of the availability of linear, triangular, quadrilateral, tetrahedral, hexahedral, conical, triangular torus, and quadrilateral torus elements. The assumption of piecewise linear deflection distribution insures monotonic convergence of the deflections from the stiffer side with decreasing mesh size. The stresses are provided by the best-fit strain tensors in the least squares at the mesh points where the deflections are given. The selection of local coordinate systems whenever necessary is automatic. The core memory is used by means of dynamic memory allocation, an optional mesh-point relabelling scheme and imposition of the boundary conditions during the assembly time.
NASA Astrophysics Data System (ADS)
Izadbakhsh, Adel; Inal, Kaan; Mishra, Raja K.
2012-04-01
In this paper, the finite strain plastic deformation of AM30 magnesium alloy has been simulated using the crystal plasticity finite element method. The simulations have been carried out using a rate-dependent elastic-viscoplastic crystal plasticity constitutive model implemented in a user defined material subroutine (UMAT) in the commercial software LS-DYNA. The plastic deformation mechanisms accounted for in the model are the slip systems in the matrix (parent grain), extension twinning systems and the slip systems inside the extension twinned regions. The parameters of the constitutive model have been calibrated using the experimental data. The calibrated model has then been used to predict the deformation of AM30 magnesium alloy in bending and simple shear. For the bending strain path, the effects of texture on the strain accommodated by the deformation mechanisms and bending moment have been investigated. For simple shear, the effects of texture on the relative activity of deformation mechanisms, shear stress and texture evolution have been investigated. Also, the effect of twinning on shear stress and texture evolution has been studied. The numerical analyses predicted a more uniform strain distribution during bending and simple shear for rolled texture compared with extruded texture.
Damage Model and Progressive Failure Analyses for Filament Wound Composite Laminates
NASA Astrophysics Data System (ADS)
Ribeiro, Marcelo Leite; Vandepitte, Dirk; Tita, Volnei
2013-10-01
Recent improvements in manufacturing processes and materials properties associated with excellent mechanical characteristics and low weight have made composite materials very attractive for application on civil aircraft structures. However, even new designs are still very conservative, because the composite failure phenomenon is very complex. Several failure criteria and theories have been developed to describe the damage process and how it evolves, but the solution of the problem is still open. Moreover, modern filament winding techniques have been used to produce a wide variety of structural shapes not only cylindrical parts, but also “flat” laminates. Therefore, this work presents the development of a damage model and its application to simulate the progressive failure of flat composite laminates made using a filament winding process. The damage model was implemented as a UMAT (User Material Subroutine), in ABAQUSTM Finite Element (FE) framework. Progressive failure analyses were carried out using FE simulation in order to simulate the failure of flat filament wound composite structures under different loading conditions. In addition, experimental tests were performed in order to identify parameters related to the material model, as well as to evaluate both the potential and the limitations of the model. The difference between numerical and the average experimental results in a four point bending set-up is only 1.6 % at maximum load amplitude. Another important issue is that the model parameters are not so complicated to be identified. This characteristic makes this model very attractive to be applied in an industrial environment.
NASA Technical Reports Server (NTRS)
Goldberg, Robert K.; Carney, Kelly S.
2004-01-01
An analysis method based on a deformation (as opposed to damage) approach has been developed to model the strain rate dependent, nonlinear deformation of woven ceramic matrix composites with a plain weave fiber architecture. In the developed model, the differences in the tension and compression response have also been considered. State variable based viscoplastic equations originally developed for metals have been modified to analyze the ceramic matrix composites. To account for the tension/compression asymmetry in the material, the effective stress and effective inelastic strain definitions have been modified. The equations have also been modified to account for the fact that in an orthotropic composite the in-plane shear stiffness is independent of the stiffness in the normal directions. The developed equations have been implemented into a commercially available transient dynamic finite element code, LS-DYNA, through the use of user defined subroutines (UMATs). The tensile, compressive, and shear deformation of a representative plain weave woven ceramic matrix composite are computed and compared to experimental results. The computed values correlate well to the experimental data, demonstrating the ability of the model to accurately compute the deformation response of woven ceramic matrix composites.
NASA Technical Reports Server (NTRS)
Goldberg, Robert K.; Carney, Kelly S.
2004-01-01
An analysis method based on a deformation (as opposed to damage) approach has been developed to model the strain rate dependent, nonlinear deformation of woven ceramic matrix composites, such as the Reinforced Carbon Carbon (RCC) material used on the leading edges of the Space Shuttle. In the developed model, the differences in the tension and compression deformation behaviors have also been accounted for. State variable viscoplastic equations originally developed for metals have been modified to analyze the ceramic matrix composites. To account for the tension/compression asymmetry in the material, the effective stress and effective inelastic strain definitions have been modified. The equations have also been modified to account for the fact that in an orthotropic composite the in-plane shear response is independent of the stiffness in the normal directions. The developed equations have been implemented into LS-DYNA through the use of user defined subroutines (UMATs). Several sample qualitative calculations have been conducted, which demonstrate the ability of the model to qualitatively capture the features of the deformation response present in woven ceramic matrix composites.
NASA Astrophysics Data System (ADS)
Mazaheri, H.; Baghani, M.; Naghdabadi, R.; Sohrabpour, S.
2016-08-01
In this work, a model is developed to continuously predict homogeneous and inhomogeneous swelling behavior of pH/temperature sensitive PNIPAM hydrogels. Employing the model, homogeneous swelling of the pH/temperature sensitive hydrogel is investigated for free and biaxial constrained swelling cases. Comparing the model results with the experimental data available in the literature, the validity of the model is confirmed. The model is then employed to investigate inhomogeneous swelling of a spherical shell on a hard core both analytically and numerically for pH or temperature variations. In this regard, numerical tools are developed via preparing a user defined subroutine in ABAQUS software. Then, the complicated problem of contact between the hydrogel shell and a micro-channel with rigid walls is also investigated. Considering the results, we can say that the model is applicable for solving engineering boundary value problem of pH/temperature sensitive hydrogels.
NASA Astrophysics Data System (ADS)
Kim, Do-Hyoung; Joo, Sung-Jun; Kwak, Dong-Ok; Kim, Hak-Sung
2015-10-01
In this study, the warpage simulation of a multi-layer printed circuit board (PCB) was performed as a function of various copper (Cu) patterns/photoimageable solder resist (PSR) composite patterns and their anisotropic viscoelastic properties. The thermo-mechanical properties of Cu/PSR patterns were obtained from finite element analysis (virtual test) and homogenized with anisotropic composite shell models that considered the viscoelastic properties. The multi-layer PCB model was simplified based on the unit Cu/PSR patterns and the warpage simulation during the reflow process was performed by using ABAQUS combined with a user-defined subroutine. From these results, it was demonstrated that the proposed anisotropic viscoelastic composite shell simulation technique can be successfully used to predict warpage of multi-layer PCBs during the reflow process.
Damage evaluation of reinforced concrete frame based on a combined fiber beam model
NASA Astrophysics Data System (ADS)
Shang, Bing; Liu, ZhanLi; Zhuang, Zhuo
2014-04-01
In order to analyze and simulate the impact collapse or seismic response of the reinforced concrete (RC) structures, a combined fiber beam model is proposed by dividing the cross section of RC beam into concrete fiber and steel fiber. The stress-strain relationship of concrete fiber is based on a model proposed by concrete codes for concrete structures. The stress-strain behavior of steel fiber is based on a model suggested by others. These constitutive models are implemented into a general finite element program ABAQUS through the user defined subroutines to provide effective computational tools for the inelastic analysis of RC frame structures. The fiber model proposed in this paper is validated by comparing with experiment data of the RC column under cyclical lateral loading. The damage evolution of a three-dimension frame subjected to impact loading is also investigated.
NASA Astrophysics Data System (ADS)
Nie, Zhenguo; Wang, Gang; Lin, Yongliang; Rong, Yiming (Kevin)
2015-12-01
Distortion resulting from heat treatment may cause serious problems for precision parts. A precision component made from 30CrNi3Mo steel with internal threads distorts slightly after quenching-tempering treatment. Such a small distortion results in serious difficulties in the subsequent assembly process. The distortion of the internal thread was measured using semi-destructive testing with video measuring system. Periodic wavy distortions emerged in the internal threads after heat treatment. Then both XRD analysis and hardness testing were conducted. A numerical simulation of the complete quenching-tempering process was conducted by DANTE, which is a set of user subroutines that link into the ABAQUS/STD solver. The results from the simulations are in good agreement with the measurement in distortion, microstructure field, and hardness. The effects of the technological parameters including quenchant, immersion orientation, and grooves were discussed on the basis of the simulation results. Finally, strategies to significantly decrease distortion and residual stress are proposed.
Use of a hyperelastic constitutive law for dry woven forming simulations
Vidal-Salle, Emmanuelle; Boisse, Philippe; Aimene, Yamina
2011-05-04
The increasing use of composite materials in industry implies an increasing use of automatic processes between which LCM processes take a large place. The improvement of such processes needs an extensive use of numerical simulations for all the stages of the process. In particular, it is necessary to know how the dry reinforcement is shaped. This paper presents a hyperelastic constitutive model for textile composite reinforcement at large strain based on an additive potential representative to tension and in-plane shearing. The proposed potential is a function of the right Cauchy Green and structural tensor invariants whose choice corresponds to textile composite reinforcement mechanical behaviour. The model is implemented in a user subroutine of ABAQUS/Explicit. The accuracy of the model has been checked and some simulations are performed on deep drawing with hemispheric punch. A good agreement is obtained with experimental forming experiments.
Predicting Failure Progression and Failure Loads in Composite Open-Hole Tension Coupons
NASA Technical Reports Server (NTRS)
Arunkumar, Satyanarayana; Przekop, Adam
2010-01-01
Failure types and failure loads in carbon-epoxy [45n/90n/-45n/0n]ms laminate coupons with central circular holes subjected to tensile load are simulated using progressive failure analysis (PFA) methodology. The progressive failure methodology is implemented using VUMAT subroutine within the ABAQUS(TradeMark)/Explicit nonlinear finite element code. The degradation model adopted in the present PFA methodology uses an instantaneous complete stress reduction (COSTR) approach to simulate damage at a material point when failure occurs. In-plane modeling parameters such as element size and shape are held constant in the finite element models, irrespective of laminate thickness and hole size, to predict failure loads and failure progression. Comparison to published test data indicates that this methodology accurately simulates brittle, pull-out and delamination failure types. The sensitivity of the failure progression and the failure load to analytical loading rates and solvers precision is demonstrated.
NASA Astrophysics Data System (ADS)
Li, Jianbao; Wang, Yue-Sheng; Zhang, Chuanzeng
2010-05-01
In this paper, a finite element method based on the ABAQUS code and user subroutine is presented to evaluate the propagation of acoustic waves in the two-dimensional phononic crystals with Archimedean-like tilings. Two systems composed of cylinder scatters embedded in a host in Ladybug and Bathroom lattices are considered. Complete and accurate band structures and transmission spectra are obtained to identify the band gaps and eigenmodes. We found that Archimedean-like structures can have some advantages over the traditional square lattice regarding the completeness of the gap and its position and width. Also, due to the same square primitive unit cell and the first Brillouin zone, the two square-like lattices have similar acoustic response in lower bands. The results indicate that the finite element method is precise for the band structure computation of the complex phononic crystals with Archimedean tilings.
NASA Astrophysics Data System (ADS)
Labergere, C.; Saanouni, K.; Benafia, S.; Galmiche, J.; Sulaiman, H.
2013-05-01
This paper presents the modelling and adaptive numerical simulation of the fine blanking process. Thermodynamically-consistent constitutive equations, strongly coupled with ductile damage, together with specific boundary conditions (particular command of forces on blank holder and counterpunch) are presented. This model is implemented into ABAQUS/EXPLICIT using the Vumat user subroutine and connected with an adaptive 2D remeshing procedure. The different material parameters are identified for the steel S600MC using experimental tensile tests conducted until the final fracture. A parametric study aiming to examine the sensitivity of the process parameters (die radius, clearance die/punch) to the punch force and fracture surfaces topology (convex zone, sheared zone, fracture zone and the burr).
NASA Astrophysics Data System (ADS)
Jiang, Yunpeng
2016-05-01
In this article, a systematic numerical study was conducted to study the detailed shear banding evolution in bulk metallic glasses (BMGs) with various sample aspect ratios under uniaxial compression, and whereby the effect of the sample aspect ratio on the compressive ductility was elucidated. A finite strain viscoelastic model was employed to describe the shear banding nucleation, growth, and coalescence in BMG samples with the help of Anand and Su's theory, which was incorporated into the ABAQUS finite element method code as a user material subroutine VUMAT. The present numerical method was first verified by comparing with the corresponding experimental results, and then parameter analysis was performed to discuss the impact of microstructure parameters on the predicted results. The present modeling will shed some light on enhancing the toughness of BMG structures in the engineering applications.
Damage and Failure Analysis of AZ31 Alloy Sheet in Warm Stamping Processes
NASA Astrophysics Data System (ADS)
Zhao, P. J.; Chen, Z. H.; Dong, C. F.
2016-06-01
In this study, a combined experimental-numerical investigation on the failure of AZ31 Mg alloy sheet in the warm stamping process was carried out based on modified GTN damage model which integrated Yld2000 anisotropic yield criterion. The constitutive equations of material were implemented into a VUMAT subroutine for solver ABAQUS/Explicit and applied to the formability analysis of mobile phone shell. The morphology near the crack area was observed using SEM, and the anisotropic damage evolution at various temperatures was simulated. The distributions of plastic strain, damage evolution, thickness, and fracture initiation obtained from FE simulation were analyzed. The corresponding forming limit diagrams were worked out, and the comparison with the experimental data showed a good agreement.
NASA Astrophysics Data System (ADS)
García, Alberto J.; Órpez, Antonio J.; Cruz-Peragón, Fernando
2013-09-01
A novel FEM thermal model for photovoltaic (PV) and concentrated photovoltaics (CPV) technologies is presented in order to improve fluid-mechanic studies for heat-sink design and thermal behavior of components in solar industry, reducing lead time from design to results. This is achieved by implementing the finite element software ABAQUS through a user defined subroutine and taking into account all the environmental requirements, and through the all known fluid-dynamics magnitude relations, as semi empirical equations. This new approach is completely novel and means that it is not necessary to make a complex CFD at early stages of design, but a simplified uncoupled non-linear thermal FEM simulation, reducing a great amount of time and costs, as it is only necessary few time to change design and to reanalyze. The results have been compared with a thermal imaging camera in real operating conditions.
Damage and Failure Analysis of AZ31 Alloy Sheet in Warm Stamping Processes
NASA Astrophysics Data System (ADS)
Zhao, P. J.; Chen, Z. H.; Dong, C. F.
2016-07-01
In this study, a combined experimental-numerical investigation on the failure of AZ31 Mg alloy sheet in the warm stamping process was carried out based on modified GTN damage model which integrated Yld2000 anisotropic yield criterion. The constitutive equations of material were implemented into a VUMAT subroutine for solver ABAQUS/Explicit and applied to the formability analysis of mobile phone shell. The morphology near the crack area was observed using SEM, and the anisotropic damage evolution at various temperatures was simulated. The distributions of plastic strain, damage evolution, thickness, and fracture initiation obtained from FE simulation were analyzed. The corresponding forming limit diagrams were worked out, and the comparison with the experimental data showed a good agreement.
A SMALL-SCALE DAMAGE APPROACH TO PREDICT FATIGUE CRACK GROWTH IN CERAMIC MATERIALS
Nguyen, Ba Nghiep; Koeppel, Brian J.; Khaleel, Mohammad A.
2006-05-19
This paper proposes a small-scale damage modeling approach to predict fatigue crack growth in ceramic materials. A fatigue damage model is formulated that uses two variables. One variable is the scalar damage variable governing the reduction of stiffness, and the other is the number of cycles. The damage evolution law is obtained based on thermodynamics of continuous media and a damage criterion containing a damage threshold function that depends on the damage variable and the cyclic loading parameters. The model has been implemented into the ABAQUS finite element code via user-subroutines and has been used in a modified boundary layer (MBL) modeling approach to analyze fatigue crack growth in a small fracture process zone situated at an initial crack tip. The model application is illustrated through an analysis of fatigue crack growth in an yttria-stabilized tetragonal zirconia material.
Viscoelastic behaviour of pumpkin balloons
NASA Astrophysics Data System (ADS)
Gerngross, T.; Xu, Y.; Pellegrino, S.
2008-11-01
The lobes of the NASA ULDB pumpkin-shaped super-pressure balloons are made of a thin polymeric film that shows considerable time-dependent behaviour. A nonlinear viscoelastic model based on experimental measurements has been recently established for this film. This paper presents a simulation of the viscoelastic behaviour of ULDB balloons with the finite element software ABAQUS. First, the standard viscoelastic modelling capabilities available in ABAQUS are examined, but are found of limited accuracy even for the case of simple uniaxial creep tests on ULDB films. Then, a nonlinear viscoelastic constitutive model is implemented by means of a user-defined subroutine. This approach is verified by means of biaxial creep experiments on pressurized cylinders and is found to be accurate provided that the film anisotropy is also included in the model. A preliminary set of predictions for a single lobe of a ULDB is presented at the end of the paper. It indicates that time-dependent effects in a balloon structure can lead to significant stress redistribution and large increases in the transverse strains in the lobes.
Choi, Kyoo Sil; Pan, Jwo
2009-07-27
In this paper, a generalized anisotropic hardening rule based on the Mroz multi-yield-surface model is derived. The evolution equation for the active yield surface is obtained by considering the continuous expansion of the active yield surface during the unloading/reloading process. The incremental constitutive relation based on the associated flow rule is then derived for a general yield function. As a special case, detailed incremental constitutive relations are derived for the Mises yield function. The closed-form solutions for one-dimensional stress-plastic strain curves are also derived and plotted for the Mises materials under cyclic loading conditions. The stress-plastic strain curves show closed hysteresis loops under uniaxial cyclic loading conditions and the Masing hypothesis is applicable. A user material subroutine based on the Mises yield function, the anisotropic hardening rule and the constitutive relations was then written and implemented into ABAQUS. Computations were conducted for a simple plane strain finite element model under uniaxial monotonic and cyclic loading conditions based on the anisotropic hardening rule and the isotropic and nonlinear kinematic hardening rules of ABAQUS. The results indicate that the plastic response of the material follows the intended input stress-strain data for the anisotropic hardening rule whereas the plastic response depends upon the input strain ranges of the stress-strain data for the nonlinear kinematic hardening rule.
Comprehensively simulating the mixed-mode progressive delamination in composite laminates
NASA Astrophysics Data System (ADS)
Gao, Zhenyuan
Delamination, or interlaminar debonding, is a commonly observed failure mechanism in composite laminates. It is of great significance to comprehensively simulate the mixed-mode progressive delamination in composite structures because by doing this, people can save a lot of effort in evaluating the safe load which a composite structure can endure. The objective of this thesis is to develop a numerical approach to simulating double-cantilever beam (DCB) and mixed-mode bending (MMB) tests and also of specifying/validating various cohesive models. A finite element framework, which consists of properly selecting time integration scheme (explicit dynamic), viscosity, load rate and mass scaling, is developed to yield converged and accurate results. Two illustrative cohesive laws (linear and power-law) are programmed with a user- defined material subroutine for ABAQUS/Explicit, VUMAT, and implemented into the finite element framework. Parameters defined in cohesive laws are studied to evaluate their effects on the predicted load-displacement curves. The finite element model, together with the predetermined model parameters, is found to be capable of producing converged and accurate results. The finite element framework, embedded with the illustrative cohesive laws, is found to be capable of handling various interfacial models. The present approach is concluded to be useful in simulating delamination with more sophisticated material models. Together with the method for determining model parameters, it can be used by computer codes other than ABAQUS.
NASA Technical Reports Server (NTRS)
Satyanarayana, Arunkumar; Bogert, Philip B.; Chunchu, Prasad B.
2007-01-01
The influence of delamination on the progressing damage path and initial failure load in composite laminates is investigated. Results are presented from a numerical and an experimental study of center-notched tensile-loaded coupons. The numerical study includes two approaches. The first approach considers only intralaminar (fiber breakage and matrix cracking) damage modes in calculating the progression of the damage path. In the second approach, the model is extended to consider the effect of interlaminar (delamination) damage modes in addition to the intralaminar damage modes. The intralaminar damage is modeled using progressive damage analysis (PDA) methodology implemented with the VUMAT subroutine in the ABAQUS finite element code. The interlaminar damage mode has been simulated using cohesive elements in ABAQUS. In the experimental study, 2-3 specimens each of two different stacking sequences of center-notched laminates are tensile loaded. The numerical results from the two different modeling approaches are compared with each other and the experimentally observed results for both laminate types. The comparisons reveal that the second modeling approach, where the delamination damage mode is included together with the intralaminar damage modes, better simulates the experimentally observed damage modes and damage paths, which were characterized by splitting failures perpendicular to the notch tips in one or more layers. Additionally, the inclusion of the delamination mode resulted in a better prediction of the loads at which the failure took place, which were higher than those predicted by the first modeling approach which did not include delaminations.
A Nonlinear Viscoelastic Model for Ceramics at High Temperatures
NASA Technical Reports Server (NTRS)
Powers, Lynn M.; Panoskaltsis, Vassilis P.; Gasparini, Dario A.; Choi, Sung R.
2002-01-01
High-temperature creep behavior of ceramics is characterized by nonlinear time-dependent responses, asymmetric behavior in tension and compression, and nucleation and coalescence of voids leading to creep rupture. Moreover, creep rupture experiments show considerable scatter or randomness in fatigue lives of nominally equal specimens. To capture the nonlinear, asymmetric time-dependent behavior, the standard linear viscoelastic solid model is modified. Nonlinearity and asymmetry are introduced in the volumetric components by using a nonlinear function similar to a hyperbolic sine function but modified to model asymmetry. The nonlinear viscoelastic model is implemented in an ABAQUS user material subroutine. To model the random formation and coalescence of voids, each element is assigned a failure strain sampled from a lognormal distribution. An element is deleted when its volumetric strain exceeds its failure strain. Element deletion has been implemented within ABAQUS. Temporal increases in strains produce a sequential loss of elements (a model for void nucleation and growth), which in turn leads to failure. Nonlinear viscoelastic model parameters are determined from uniaxial tensile and compressive creep experiments on silicon nitride. The model is then used to predict the deformation of four-point bending and ball-on-ring specimens. Simulation is used to predict statistical moments of creep rupture lives. Numerical simulation results compare well with results of experiments of four-point bending specimens. The analytical model is intended to be used to predict the creep rupture lives of ceramic parts in arbitrary stress conditions.
Impact Damage of 3D Orthogonal Woven Composite Circular Plates
NASA Astrophysics Data System (ADS)
Ji, Changgan; Sun, Baozhong; Qiu, Yiping; Gu, Bohong
2007-11-01
The damages of 3D orthogonal woven composite circular plate under quasi-static indentation and transverse impact were tested with Materials Test System (MTS) and modified split Hopkinson bar (SHPB) apparatus. The load vs. displacement curves during quasi-static penetration and impact were obtained to study the energy absorption of the composite plate. The fluctuation of the impact stress waves has been unveiled. Differences of the load-displacement curves between the quasi-static and impact loading are discussed. This work also aims at establishing a unit-cell model to analyze the damage of composites. A user material subroutine which named VUMAT for characterizing the constitutive relationship of the 3-D orthogonal woven composite and the damage evolution is incorporated with a finite element code ABAQUS/Explicit to simulate the impact damage process of the composite plates. From the comparison of the load-displacement curves and energy absorption curves of the composite plate between experimental and FEM simulation, it is shown that the unit-cell model of the 3D woven composite and the VUMAT combined with the ABAQUS/Explicit can calculate the impact responses of the circular plate precisely. Furthermore, the model can also be extended to simulate the impact behavior of the 3D woven composite structures.
Simulation of ratcheting in straight pipes using ANSYS with an improved cyclic plasticity model
Hassan, T.; Zhu, Y.; Matzen, V.C.
1996-12-01
Ratcheting has been shown to be a contributing cause of failure in several seismic experiments on piping components and systems. Most commercial finite element codes have been unable to simulate the ratcheting in those tests accurately. The reason for this can be traced to inadequate plasticity constitutive models in the analysis codes. The authors have incorporated an improved cyclic plasticity model, based on an Armstrong-Frederick kinematic hardening rule in conjunction with the Drucker-Palgen plastic modulus equation, into an ANSYS user subroutine. This modified analysis code has been able to simulate quite accurately the ratcheting behavior of a tube subjected to a constant internal pressure and axially strain controlled cycling. This paper describes simulations obtained form this modified ANSYS code for two additional tests: (1) a tube subjected to constant axial stress and prescribed torsional cycling, and (2) a straight pipe subjected to constant internal pressure and quasi-static cyclic bending. The analysis results from the modified ANSYS code are compared to the experimental data, as well as results from ABAQUS and the original ANSYS code. The resulting correlation shows a significant improvement over the original ANSYS and the ABAQUS codes.
NASA Astrophysics Data System (ADS)
Park, Taejoon; Seok, Dong-Yoon; Lee, Chul-Hwan; Noma, Nobuyasu; Kuwabara, Toshihiko; Stoughton, Thomas B.; Chung, Kwansoo
2011-08-01
A two-surface isotropic-kinematic hardening law was developed based on a two-surface plasticity model previously proposed by Lee et al., (2007, Int. J. Plast. 23, 1189-1212). In order to properly represent the Bauschinger and transient behaviors as well as permanent softening during reverse loading with various pre-strains, both the inner yield surface and the outer bounding surface expand (isotropic hardening) and translate (kinematic hardening) in this two-surface model. As for the permanent softening, both the isotropic hardening and the kinematic hardening evolution of the outer bounding surface were modified by introducing softening parameters. The numerical formulation was also developed based on the incremental plasticity theory and the developed constitutive law was implemented into the commercial finite element program, ABAQUS/Explicit and ABAQUS/Standard using the user-defined material subroutines. In this work, a dual phase (DP) steel was considered as an advanced high strength steel sheet and uni-axial tension tests and uni-axial tension-compression-tension tests were performed for the characterization of the material property. For a validation purpose, the developed two-surface plasticity model was applied to the 2-D draw bending test proposed as a benchmark problem of the NUMISHEET 2011 conference and successfully validated with experiments.
Modeling fluid structure interaction with shape memory alloy actuated morphing aerostructures
NASA Astrophysics Data System (ADS)
Oehler, Stephen D.; Hartl, Darren J.; Turner, Travis L.; Lagoudas, Dimitris C.
2012-04-01
The development of efficient and accurate analysis techniques for morphing aerostructures incorporating shape memory alloys (SMAs) continues to garner attention. These active materials have a high actuation energy density, making them an ideal replacement for conventional actuation mechanisms in morphing structures. However, SMA components are often exposed to the same highly variable environments experienced by the aeroelastic assemblies into which they are incorporated. This is motivating design engineers to consider modeling fluidstructure interaction for prescribing dynamic, solution-dependent boundary conditions. This work presents a computational study of a particular morphing aerostructure with embedded, thermally actuating SMA ribbons and demonstrates the effective use of fluid-structure interaction modeling. A cosimulation analysis is utilized to determine the surface deflections and stress distributions of an example aerostructure with embedded SMA ribbons using the Abaqus Finite Element Analysis (FEA) software suite, combined with an Abaqus Computational Fluid Dynamics (CFD) processor. The global FEA solver utilizes a robust user-defined material subroutine which contains an accurate three-dimensional SMA constitutive model. Variations in the ambient fluid environment are computed using the CFD solver, and fluid pressure is mapped into surface distributed loads. Results from the analysis are qualitatively validated with independently obtained data from representative flow tests previously conducted on a physical prototype of the same aerostructure.
Crystallographic effects during micromachining — A finite-element model
NASA Astrophysics Data System (ADS)
Song, Shin-Hyung; Choi, Woo Chun
2015-07-01
Mechanical micromachining is a powerful and effective way for manufacturing small sized machine parts. Even though the micromachining process is similar to the traditional machining, the material behavior during the process is much different. In particular, many researchers report that the basic mechanics of the work material is affected by microstructures and their crystallographic orientations. For example, crystallographic orientations of the work material have significant influence on force response, chip formation and surface finish. In order to thoroughly understand the effect of crystallographic orientations on the micromachining process, finite-element model (FEM) simulating orthogonal cutting process of single crystallographic material was presented. For modeling the work material, rate sensitive single crystal plasticity of face-centered cubic (FCC) crystal was implemented. For the chip formation during the simulation, element deletion technique was used. The simulation model is developed using ABAQUS/explicit with user material subroutine via user material subroutine (VUMAT). Simulations showed that variation of the specific cutting energy at different crystallographic orientations of work material shows significant anisotropy. The developed FEM model can be a useful prediction tool of micromachining of crystalline materials.
Pierrat, B; Murphy, J G; MacManus, D B; Gilchrist, M D
2016-01-01
Modelling transversely isotropic materials in finite strain problems is a complex task in biomechanics, and is usually addressed by using finite element (FE) simulations. The standard method developed to account for the quasi-incompressible nature of soft tissues is to decompose the strain energy function (SEF) into volumetric and deviatoric parts. However, this decomposition is only valid for fully incompressible materials, and its use for slightly compressible materials yields an unphysical response during the simulation of hydrostatic tension/compression of a transversely isotropic material. This paper presents the FE implementation as subroutines of a new volumetric model solving this deficiency in two FE codes: Abaqus and FEBio. This model also has the specificity of restoring the compatibility with small strain theory. The stress and elasticity tensors are first derived for a general SEF. This is followed by a successful convergence check using a particular SEF and a suite of single-element tests showing that this new model does not only correct the hydrostatic deficiency but may also affect stresses during shear tests (Poynting effect) and lateral stretches during uniaxial tests (Poisson's effect). These FE subroutines have numerous applications including the modelling of tendons, ligaments, heart tissue, etc. The biomechanics community should be aware of specificities of the standard model, and the new model should be used when accurate FE results are desired in the case of compressible materials. PMID:26252069
NASA Astrophysics Data System (ADS)
Mirkhani, Hamidreza; Joshi, Shailendra P.
2014-08-01
Nanotwinned (nt) metals are an important subset of nanostructured materials because they exhibit impressive strength and ductility. Several recent investigations on nt face-centered-cubic (FCC) metals indicate that their macroscopic responses emerge from complex microscopic mechanisms that are dominated by dislocation-TB interactions. Under applied stimulus, nt microstructures evolve through migration of twin boundaries (TBs) that may have implications on the material strength and stability. This work focuses on modeling TB migration within finite element framework in an explicit manner and studying its effects on the micromechanics of twinned FCC metals under quasi-static loading conditions. The theoretical setting is developed using three-dimensional single crystal plasticity as a basis wherein the plastic slip on the {111}<1bar10> slip systems in an FCC crystal structure is modeled as visco-plastic behavior. Owing to their governing role, twins are modeled as discrete lamellas with full crystallographic anisotropy. To model TB migration, an additional visco-plastic slip-law for twinning partial systems ({111}<112bar>) based on the nucleation and motion of twin partial dislocations is introduced. This size-dependent constitutive law is presumed to prevail in the vicinity of the TB and naturally facilitates TB migration when combined with a twinning condition that is based on the accrual of the necessary shear strain. The constitutive development is implemented within a finite element framework through a User Material (UMAT) facility within ABAQUS/STANDARD®. Detailed micromechanics simulations on model microstructures involving single-grained and polycrystalline topologies are presented.
An incrementally non-linear model for clays with directional stiffness and a small strain emphasis
NASA Astrophysics Data System (ADS)
Tu, Xuxin
In response to construction activities and loads from permanent structures, soil generally is subjected to a variety of loading modes varying both in time and location. It also has been increasingly appreciated that the strains around well-designed foundations, excavations and tunnels are mostly small, with soil responses at this strain level generally being non-linear and anisotropic. To make accurate prediction of the performance of a geo-system, it is highly desirable to understand soil behavior at small strains along multiple loading directions, and accordingly to incorporate these responses in an appropriate constitutive model implemented in a finite element analysis. This dissertation presents a model based on a series of stress probe tests with small strain measurements performed on compressible Chicago glacial clays. The proposed model is formulated in an original constitutive framework, in which the tangent stiffness matrix is constructed in accordance with the mechanical nature of frictional materials and the tangent moduli therein are described explicitly. The stiffness description includes evolution relations with regard to length of stress path, and directionality relations in terms of stress path direction. The former relations provide distinctive definitions for small-strain and large-strain behaviors, and distinguish soil responses in shearing and compression. The latter relations make this model incrementally non-linear and thus capable of modeling inelastic behavior. A new algorithm based on a classical substepping scheme is developed to numerically integrate this model. A consistent tangent matrix is derived for the proposed model with the upgraded substepping scheme. The code is written in FORTRAN and implemented in FEM via UMAT of ABAQUS. The model is exercised in a variety of applications ranging from oedometer, triaxial and biaxial test simulations to a C-class prediction for a well-instrumented excavation. The computed results indicate that
Hambli, Ridha; Boughattas, Mohamed Hafedh; Daniel, Jean-Luc; Kourta, Azeddine
2016-07-01
Denosumab is a fully human monoclonal antibody that inhibits receptor activator of nuclearfactor-kappa B ligand (RANKL). This key mediator of osteoclast activities has been shown to inhibit osteoclast differentiation and hence, to increase bone mineral density (BMD) in treated patients. In the current study, we develop a computer model to simulate the effects of denosumab treatments (dose and duration) on the proximal femur bone remodeling process quantified by the variation in proximal femur BMD. The simulation model is based on a coupled pharmacokinetics model of denosumab with a pharmacodynamics model consisting of a mechanobiological finite element remodeling model which describes the activities of osteoclasts and osteoblasts. The mechanical behavior of bone is described by taking into account the bone material fatigue damage accumulation and mineralization. A coupled strain-damage stimulus function is proposed which controls the level of bone cell autocrine and paracrine factors. The cellular behavior is based on Komarova et al.׳s (2003) dynamic law which describes the autocrine and paracrine interactions between osteoblasts and osteoclasts and computes cell population dynamics and changes in bone mass at a discrete site of bone remodeling. Therefore, when an external mechanical stress is applied, bone formation and resorption is governed by cell dynamics rather than by adaptive elasticity approaches. The proposed finite element model was implemented in the finite element code Abaqus (UMAT routine). In order to perform a preliminary validation, in vivo human proximal femurs were selected and scanned at two different time intervals (at baseline and at a 36-month interval). Then, a 3D FE model was generated and the denosumab-remodeling algorithm was applied to the scans at t0 simulating daily walking activities for a duration of 36 months. The predicted results (density variation) were compared to existing published ones performed on a human cohort (FREEDOM
Hambli, Ridha
2014-01-01
Bone adaptation occurs as a response to external loadings and involves bone resorption by osteoclasts followed by the formation of new bone by osteoblasts. It is directly triggered by the transduction phase by osteocytes embedded within the bone matrix. The bone remodeling process is governed by the interactions between osteoblasts and osteoclasts through the expression of several autocrine and paracrine factors that control bone cell populations and their relative rate of differentiation and proliferation. A review of the literature shows that despite the progress in bone remodeling simulation using the finite element (FE) method, there is still a lack of predictive models that explicitly consider the interaction between osteoblasts and osteoclasts combined with the mechanical response of bone. The current study attempts to develop an FE model to describe the bone remodeling process, taking into consideration the activities of osteoclasts and osteoblasts. The mechanical behavior of bone is described by taking into account the bone material fatigue damage accumulation and mineralization. A coupled strain–damage stimulus function is proposed, which controls the level of autocrine and paracrine factors. The cellular behavior is based on Komarova et al.’s (2003) dynamic law, which describes the autocrine and paracrine interactions between osteoblasts and osteoclasts and computes cell population dynamics and changes in bone mass at a discrete site of bone remodeling. Therefore, when an external mechanical stress is applied, bone formation and resorption is governed by cells dynamic rather than adaptive elasticity approaches. The proposed FE model has been implemented in the FE code Abaqus (UMAT routine). An example of human proximal femur is investigated using the model developed. The model was able to predict final human proximal femur adaptation similar to the patterns observed in a human proximal femur. The results obtained reveal complex spatio-temporal bone
NASA Astrophysics Data System (ADS)
Fein, Jonathan
Woven fabric composite materials are widely used in the construction of aircraft engine fan containment systems, mostly due to their high strength to weight ratios and ease of implementation. The development of a predictive model for fan blade containment would provide great benefit to engine manufactures in shortened development cycle time, less risk in certification and fewer dollars lost to redesign/recertification cycles. A mechanistic user-defined material model subroutine has been developed at Arizona State University (ASU) that captures the behavioral response of these fabrics, namely Kevlar ® 49, under ballistic loading. Previously developed finite element models used to validate the consistency of this material model neglected the effects of the physical constraints imposed on the test setup during ballistic testing performed at NASA Glenn Research Center (NASA GRC). Part of this research was to explore the effects of these boundary conditions on the results of the numerical simulations. These effects were found to be negligible in most instances. Other material models for woven fabrics are available in the LS-DYNA finite element code. One of these models, MAT234: MAT_VISCOELASTIC_LOOSE_FABRIC (Ivanov & Tabiei, 2004) was studied and implemented in the finite element simulations of ballistic testing associated with the FAA ASU research. The results from these models are compared to results obtained from the ASU UMAT as part of this research. The results indicate an underestimation in the energy absorption characteristics of the Kevlar 49 fabric containment systems. More investigation needs to be performed in the implementation of MAT234 for Kevlar 49 fabric. Static penetrator testing of Kevlar® 49 fabric was performed at ASU in conjunction with this research. These experiments are designed to mimic the type of loading experienced during fan blade out events. The resulting experimental strains were measured using a non-contact optical strain measurement
Effects of cavern depth on surface subsidence and storage loss of oil-filled caverns
Hoffman, E L
1992-01-01
Finite element analyses of oil-filled caverns were performed to investigate the effects of cavern depth on surface subsidence and storage loss, a primary performance criteria of SPR caverns. The finite element model used for this study was axisymmetric, approximating an infinite array of caverns spaced at 750 ft. The stratigraphy and cavern size were held constant while the cavern depth was varied between 1500 ft and 3000 ft in 500 ft increments. Thirty year simulations, the design life of the typical SPR cavern, were performed with boundary conditions modeling the oil pressure head applied to the cavern lining. A depth dependent temperature gradient of 0.012{degrees}F/ft was also applied to the model. The calculations were performed using ABAQUS, a general purpose of finite element analysis code. The user-defined subroutine option in ABAQUS was used to enter an elastic secondary creep model which includes temperature dependence. The calculations demonstrated that surface subsidence and storage loss rates increase with increasing depth. At lower depths the difference between the lithostatic stress and the oil pressure is greater. Thus, the effective stresses are greater, resulting in higher creep rates. Furthermore, at greater depths the cavern temperatures are higher which also produce higher creep rates. Together, these factors result in faster closure of the cavern. At the end of the 30 year simulations, a 1500 ft-deep cavern exhibited 4 percent storage loss and 4 ft of subsidence while a 3000 ft-deep cavern exhibited 33 percent storage loss and 44 ft of subsidence. The calculations also demonstrated that surface subsidence is directly related to the amount of storage loss. Deeper caverns exhibit more subsidence because the caverns exhibit more storage loss. However, for a given amount of storage loss, nearly the same magnitude of surface subsidence was exhibited, independent of cavern depth.
A numerical study on intended and unintended failure mechanisms in blanking of sandwich plates
NASA Astrophysics Data System (ADS)
Chen, L.; Soyarslan, C.; Tekkaya, A. E.
2013-05-01
Metal-polymer-metal sandwich plates are widely used in the automotive and aerospace industry. As for different applications the sandwich plates can be divided into two types. They are sound-damping laminates with a polymer core much thinner than the metallic faces and low-density laminates with a core thickness of approximately 40-60% of the total thickness. One frequent process step in production of parts made of these plates is the blanking process whose hereditary effects draw the limits of further forming stages or service performance and life; e.g. the failure of the adhesive in the thermoplastic polymer interface affects the sound-damping efficiency intensively. With this motivation, we present FE simulation of an axi-symmetric blanking process of steel/polyethylene/steel sound-damping laminates. The mechanical behavior of the metallic layers was characterized by finite strain rate independent elasto-plasticity where progressive material deterioration and fracture are given account for using continuum damage mechanics (CDM). This material model is made accessible via implementations as VUMAT subroutines for ABAQUS/Explicit. Possible failure of the thermoplastic polymer which may lead to delamination of the metallic layers is modeled using ABAQUS built-in cohesive zone elements. The results show that existing intended and unintended failure modes, e.g. blanking of the metallic and thermoplastic polymer constituents as well as failure of polymer layer under shear and compression, can be effectively studied with the proposed framework for process enhancement. As a future work, a damage coupled nonlinear visco-elastic constitutive model will be devised for the simulation of the thermoplastic layer in low-density laminates.
Nonlinear mesomechanics of composites with periodic microstructure
NASA Technical Reports Server (NTRS)
Walker, Kevin P.; Jordan, Eric H.; Freed, Alan D.
1989-01-01
This work is concerned with modeling the mechanical deformation or constitutive behavior of composites comprised of a periodic microstructure under small displacement conditions at elevated temperature. A mesomechanics approach is adopted which relates the microimechanical behavior of the heterogeneous composite with its in-service macroscopic behavior. Two different methods, one based on a Fourier series approach and the other on a Green's function approach, are used in modeling the micromechanical behavior of the composite material. Although the constitutive formulations are based on a micromechanical approach, it should be stressed that the resulting equations are volume averaged to produce overall effective constitutive relations which relate the bulk, volume averaged, stress increment to the bulk, volume averaged, strain increment. As such, they are macromodels which can be used directly in nonlinear finite element programs such as MARC, ANSYS and ABAQUS or in boundary element programs such as BEST3D. In developing the volume averaged or efective macromodels from the micromechanical models, both approaches will require the evaluation of volume integrals containing the spatially varying strain distributions throughout the composite material. By assuming that the strain distributions are spatially constant within each constituent phase-or within a given subvolume within each constituent phase-of the composite material, the volume integrals can be obtained in closed form. This simplified micromodel can then be volume averaged to obtain an effective macromodel suitable for use in the MARC, ANSYS and ABAQUS nonlinear finite element programs via user constitutive subroutines such as HYPELA and CMUSER. This effective macromodel can be used in a nonlinear finite element structural analysis to obtain the strain-temperature history at those points in the structure where thermomechanical cracking and damage are expected to occur, the so called damage critical points of
Flight dynamics analysis and simulation of heavy lift airships. Volume 5: Programmer's manual
NASA Technical Reports Server (NTRS)
Ringland, R. F.; Tischler, M. B.; Jex, H. R.; Emmen, R. D.; Ashkenas, I. L.
1982-01-01
The Programmer's Manual contains explanations of the logic embodied in the various program modules, a dictionary of program variables, a subroutine listing, subroutine/common block/cross reference listing, and a calling/called subroutine cross reference listing.
NASA Astrophysics Data System (ADS)
Lee, C. H.; Yang, D. Y.; Lee, S. R.; Chang, I. G.; Lee, T. W.
2011-08-01
The shielded slot plate, which has a sheared corrugated trapezoidal pattern, is a component of the metallic bipolar plate for the molten carbonate fuel cell (MCFC). In order to increase the efficiency of the fuel cell, the unit cell of the shielded slot plate should have a relatively large upper area. Additionally, defects from the forming process should be minimized. In order to simulate the slitting process, whereby sheared corrugated patterns are formed, ductile fracture criteria based on the histories of stress and strain are employed. The user material subroutine VUMAT is employed for implementation of the material and ductile fracture criteria in the commercial FEM software ABAQUS. The variables of the ductile fracture criteria were determined by comparing the simulation results and the experimental results of the tension test and the shearing test. Parametric studies were conducted to determine the critical value of the ductile fracture criterion. Employing these ductile fracture criteria, the three dimensional forming process of the shielded slot plate was numerically simulated. The effects of the slitting process in the forming process of the shielded slot plate were analyzed through a FEM simulation and experimental studies. Finally, experiments involving microscopic and macroscopic observations were conducted to verify the numerical simulations of the 3-step forming process.
NASA Astrophysics Data System (ADS)
Yang, Dong-Yol; Lee, Chang-Whan; Kang, Dong-Woo; Chang, In-Gab; Lee, Tae-Won
2013-05-01
The shielded slot plate, a repeated structure of high sheared protrusions, is a major component of metallic bipolar plates for the molten carbonate fuel cell (MCFC). In order to increase the efficiency of the MCFC and long-term operation capability, the sheared protrusion should have a relatively large flat contact area. In addition, defects from the forming process such as local thinning should be minimized. In this work, the preform shape in the three-stage forming process that integrates the slitting process, the preforming process, and the final forming process was optimized to minimize the effective plastic strain. In the simulation of the forming process, the ductile fracture criterion was employed to the user material subroutine VUMAT in ABAQUS/Explicit. Steepest descent method was utilized in the design of the forming process to minimize equivalent plastic strain. High sheared protrusions were manufactured without defects from the three-stage forming process using the optimized preform shape. The minimum thickness of one sheared protrusion was increased by 25% over that of the two-stage forming process. The three-stage forming process using the optimized preform shape enables more uniformly distributed deformation and reduces localized deformation.
Investigation on low velocity impact resistance of SMA composite material
NASA Astrophysics Data System (ADS)
Hu, Dianyin; Zhang, Long; Wang, Rongqiao; Zhang, Xiaoyong
2016-04-01
A method to improve low velocity impact resistance of aeroengine composite casing using shape memory alloy's properties of shape memory(SM) and super-elasticity(SE) is proposed in this study. Firstly, a numerical modeling of SMA reinforced composite laminate under low velocity impact load with impact velocity of 10 m/s is established based on its constitutive model implemented by the VUMAT subroutine of commercial software ABAQUS. Secondly, the responses of SMA composite laminate including stress and deflection distributions were achieved through transient analysis under low velocity impact load. Numerical results show that both peak stress and deflection values of SMA composite laminate are less than that without SMA, which proves that embedding SMA into the composite structure can effectively improve the low velocity impact performance of composite structure. Finally, the influence of SM and SE on low velocity impact resistance is quantitatively investigated. The values of peak stress and deflection of SMA composite based on SM property decrease by 18.28% and 9.43% respectively, compared with those without SMA, instead of 12.87% and 5.19% based on SE. In conclusion, this proposed model described the impact damage of SMA composite structure and turned to be a more beneficial method to enhance the impact resistance by utilizing SM effect.
The finite element analysis of austenite decomposition during continuous cooling in 22MnB5 steel
NASA Astrophysics Data System (ADS)
Chen, Xiangjun; Xiao, Namin; Li, Dianzhong; Li, Guangyao; Sun, Guangyong
2014-09-01
The hot stamping process has been increasingly used in newly designed vehicles to improve crash worthiness and fuel efficiency. In this study, a finite element model based on a subroutine of the commercial software ABAQUS is developed to predict the interactive influence of temperature field and phase transformation on high-strength boron steel. JMAK-type equations with the incubation time and additivity hypothesis are adopted to describe the austenite decomposition into ferrite, pearlite and bainite, while the Koistinen and Marburger (K-M) model is used to describe the displacive transformation of matensite. The simulation results show that the introduction of incubation time into a JMAK equation can provide a more reasonable prediction of the transformation kinetics than if the equation is unmodified. A comparison between the simulation and the standard Jominy end-quenching test demonstrates the capability of the present model for the prediction of transformation kinetics, microstructure distribution and mechanical properties. Furthermore, the adoption of experimentally measured microhardness values for the individual phase constituent can produce improved accuracy of the hardness predictions compared to the empirical hardness equations.
Multiscale Concrete Modeling of Aging Degradation
Hammi, Yousseff; Gullett, Philipp; Horstemeyer, Mark F.
2015-07-31
In this work a numerical finite element framework is implemented to enable the integration of coupled multiscale and multiphysics transport processes. A User Element subroutine (UEL) in Abaqus is used to simultaneously solve stress equilibrium, heat conduction, and multiple diffusion equations for 2D and 3D linear and quadratic elements. Transport processes in concrete structures and their degradation mechanisms are presented along with the discretization of the governing equations. The multiphysics modeling framework is theoretically extended to the linear elastic fracture mechanics (LEFM) by introducing the eXtended Finite Element Method (XFEM) and based on the XFEM user element implementation of Giner et al. [2009]. A damage model that takes into account the damage contribution from the different degradation mechanisms is theoretically developed. The total contribution of damage is forwarded to a Multi-Stage Fatigue (MSF) model to enable the assessment of the fatigue life and the deterioration of reinforced concrete structures in a nuclear power plant. Finally, two examples are presented to illustrate the developed multiphysics user element implementation and the XFEM implementation of Giner et al. [2009].
Experimental and Numerical Analysis of Notched Composites Under Tension Loading
NASA Astrophysics Data System (ADS)
Aidi, Bilel; Case, Scott W.
2015-12-01
Experimental quasi-static tests were performed on center notched carbon fiber reinforced polymer (CFRP) composites having different stacking sequences made of G40-600/5245C prepreg. The three-dimensional Digital Image Correlation (DIC) technique was used during quasi-static tests conducted on quasi-isotropic notched samples to obtain the distribution of strains as a function of applied stress. A finite element model was built within Abaqus to predict the notched strength and the strain profiles for comparison with measured results. A user-material subroutine using the multi-continuum theory (MCT) as a failure initiation criterion and an energy-based damage evolution law as implemented by Autodesk Simulation Composite Analysis (ASCA) was used to conduct a quantitative comparison of strain components predicted by the analysis and obtained in the experiments. Good agreement between experimental data and numerical analyses results are observed. Modal analysis was carried out to investigate the effect of static damage on the dominant frequencies of the notched structure using the resulted degraded material elements. The first in-plane mode was found to be a good candidate for tracking the level of damage.
CREEP MODELING FOR INJECTION-MOLDED LONG-FIBER THERMOPLASTICS
Nguyen, Ba Nghiep; Kunc, Vlastimil; Bapanapalli, Satish K.
2008-06-30
This paper proposes a model to predict the creep response of injection-molded long-fiber thermoplastics (LFTs). The model accounts for elastic fibers embedded in a thermoplastic resin that exhibits the nonlinear viscoelastic behavior described by the Schapery’s model. It also accounts for fiber length and orientation distributions in the composite formed by the injection-molding process. Fiber length and orientation distributions were measured and used in the analysis that applies the Eshelby’s equivalent inclusion method, the Mori-Tanaka assumption (termed as the Eshelby-Mori-Tanaka approach) and the fiber orientation averaging technique to compute the overall strain increment resulting from an overall constant applied stress during a given time increment. The creep model for LFTs has been implemented in the ABAQUS finite element code via user-subroutines and has been validated against the experimental creep data obtained for long-glass-fiber/polypropylene specimens. The effects of fiber orientation and length distributions on the composite creep response are determined and discussed.
DAMAGE MODELING OF INJECTION-MOLDED SHORT- AND LONG-FIBER THERMOPLASTICS
Nguyen, Ba Nghiep; Kunc, Vlastimil; Bapanapalli, Satish K.; Phelps, Jay; Tucker III, Charles L.
2009-10-30
This article applies the recent anisotropic rotary diffusion – reduced strain closure (ARD-RSC) model for predicting fiber orientation and a new damage model for injection-molded long-fiber thermoplastics (LFTs) to analyze progressive damage leading to total failure of injection-molded long-glass-fiber/polypropylene (PP) specimens. The ARD-RSC model was implemented in a research version of the Autodesk Moldflow Plastics Insight (MPI) processing code, and it has been used to simulate injection-molding of a long-glass-fiber/PP plaque. The damage model combines micromechanical modeling with a continuum damage mechanics description to predict the nonlinear behavior due to plasticity coupled with damage in LFTs. This model has been implemented in the ABAQUS finite element code via user-subroutines and has been used in the damage analyses of tensile specimens removed from the injection-molded long-glass-fiber/PP plaques. Experimental characterization and mechanical testing were performed to provide input data to support and validate both process modeling and damage analyses. The predictions are in agreement with the experimental results.
Numerical and Experimental Study on Hydrodynamic Deep Drawing of Hemispherical Cups
NASA Astrophysics Data System (ADS)
Shamsi-Sarband, S.; Hosseimpour, S. J.; Bakhshi-Jooyban, M.
2011-01-01
In this research, the production of a hemispherical cup by hydrodynamic deep drawing was investigated by using finite element simulation and experimental works. The aim was to study the effect of the liquid pressure on the cup thickness distribution and dimensional accuracy. For this purpose, plain carbon steel sheet with 0.8mm thickness and 80mm diameter was used as a blank. The punch diameter was 40mm and motor oil SAE20w50 was used as a pressure medium. The finite element code ABAQUS/Explicit 6.8 was used to simulate the process. Due to symmetry, only quarter of the die and sheet were modeled. The liquid pressure was modeled by applying an extended load onthe blank. VDLOAD subroutine was used to control the pressure variation during the process. Moreover, the pressure path was studied mathematically. There was an acceptable agreement between the experimental results and finite element analysis. The results indicated that there is an optimum pressure which the thickness uniformity and the wall dimensional accuracy of the cup is improved.
A viscoelastic poromechanical model of the knee joint in large compression.
Kazemi, M; Li, L P
2014-08-01
The elastic response of the knee joint in various loading and pathological conditions has been investigated using anatomically accurate geometry. However, it is still challenging to predict the poromechanical response of the knee in realistic loading conditions. In the present study, a viscoelastic, poromechanical model of the knee joint was developed for soft tissues undergoing large deformation. Cartilages and menisci were modeled as fibril-reinforced porous materials and ligaments were considered as fibril-reinforced hyperelastic solids. Quasi-linear viscoelasticty was formulated for the collagen network of these tissues and nearly incompressible Neo-Hookean hyperelasticity was used for the non-fibrillar matrix. The constitutive model was coded with a user defined FORTRAN subroutine, in order to use ABAQUS for the finite element analysis. Creep and stress relaxation were investigated with large compression of the knee in full extension. The contact pressure distributions were found similar in creep and stress relaxation. However, the load transfer in the joint was completely different in these two loading scenarios. During creep, the contact pressure between cartilages decreased but the pressure between cartilage and meniscus increased with time. This led to a gradual transfer of some loading from the central part of cartilages to menisci. During stress relaxation, however, both contact pressures decreased monotonically. PMID:24933338
An efficient FE-SBFE coupled method for mesoscale cohesive fracture modelling of concrete
NASA Astrophysics Data System (ADS)
Huang, Y. J.; Yang, Z. J.; Liu, G. H.; Chen, X. W.
2016-07-01
This study develops a method coupling the finite element method (FEM) and the scaled boundary finite element method (SBFEM) for efficient meso-scale fracture modelling of concrete for the first time. In this method, the aggregates are modelled by SBFE polygons with boundaries discretised only, while the mortar matrix is modelled by conventional finite elements. The semi-analytical SBFEM is implemented in ABAQUS by a user-defined element subroutine for the first time. Nonlinear cohesive interface elements with normal and shear traction-separation constitutive laws are pre-inserted within the mortar and on the aggregate-mortar interfaces to simulate potential cracks. Various meso-structures generated from both random aggregates and X-ray computed tomography images are modelled. The results demonstrate that the coupled method leads to considerable reductions in degrees of freedom and computational time against the conventional FEM, and these reductions become more significant when the aggregate volume fraction increases. The modelled crack paths and load-carrying capacities of a three-point bending beam and an L-shaped panel are in excellent agreement with the experimental data.
Li, N.; Mohamed, M. S.; Cai, J.; Lin, J.; Balint, D.; Dean, T. A.
2011-05-04
Formability of steel and aluminium alloys in hot stamping and cold die quenching processes is studied in this research. Viscoplastic-damage constitutive equations are developed and determined from experimental data for the prediction of viscoplastic flow and ductility of the materials. The determined unified constitutive equations are then implemented into the commercial Finite Element code Abaqus/Explicit via a user defined subroutine, VUMAT. An FE process simulation model and numerical procedures are established for the modeling of hot stamping processes for a spherical part with a central hole. Different failure modes (failure takes place either near the central hole or in the mid span of the part) are obtained. To validate the simulation results, a test programme is developed, a test die set has been designed and manufactured, and tests have been carried out for the materials with different forming rates. It has been found that very close agreements between experimental and numerical process simulation results are obtained for the ranges of temperatures and forming rates carried out.
A Simulation for the Punchless Piercing Process using Lemaitre Damage Model
Lee, Sang Wook; Pourboghrat, Farhang
2005-08-05
The punchless piercing is a process that uses highly pressurized fluid instead of the conventional punch to make holes into the sheet metal. This process has many advantages over the conventional method for piercing various shaped holes into very thin strips of metal, composite, etc. An important cost advantage comes from not having to use a punch. Another important advantage comes from the top quality of pierced holes produced by punchless piercing, as no secondary finishing process will be needed for removing burrs typically found in conventional cutting processes. The ABAQUS/Explicit FEM code coupled with Lemaitre damage model has been used to more precisely characterize the punchless piercing process. The formulation adopted for this purpose focuses on the development of an efficient stress integration algorithm and development of a user material subroutine (VUMAT). For verification, the computed results have been compared with those of the experimental results in the literature and shown to be in good agreement with each other. The results obtained from this work are expected to be of significant interest to automotive and aerospace industries interested in using the punchless piercing process.
A second-order two-scale homogenization procedure using macrolevel discretization
NASA Astrophysics Data System (ADS)
Lesičar, Tomislav; Tonković, Zdenko; Sorić, Jurica
2014-08-01
The present study deals with a second-order two-scale computational homogenization procedure for modeling deformation responses of heterogeneous materials at small strains. The macro to micro transition and the application of generalized periodic boundary conditions on the representative volume element (RVE) at the microlevel are investigated. The structure at macroscale level is discretized by the two dimensional triangular finite elements, while the quadrilateral finite element is used for the discretization of the RVE. The finite element formulations and the new proposed multiscale scheme have been implemented into the finite element software ABAQUS using user subroutines derived. Due to the continuity transition, an additional integral condition on microlevel fluctuation field has to be imposed, as expected. The integration has been performed using various numerical integration techniques and the results obtained are compared in a few examples. It is concluded that only trapezoidal rule gives a physically based deformed shape of the RVE. Finally, the efficiency and accuracy of the proposed multiscale homogenization approach are demonstrated by the modeling of a shear layer problem, usually used as a benchmark in multiscale analyses.
Constitutive modeling of polycarbonate over a wide range of strain rates and temperatures
NASA Astrophysics Data System (ADS)
Wang, Haitao; Zhou, Huamin; Huang, Zhigao; Zhang, Yun; Zhao, Xiaoxuan
2016-06-01
The mechanical behavior of polycarbonate was experimentally investigated over a wide range of strain rates ( 10^{-4} to 5× 103 s^{-1}) and temperatures (293 to 353 K). Compression tests under these conditions were performed using a SHIMADZU universal testing machine and a split Hopkinson pressure bar. Falling weight impact testing was carried out on an Instron Dynatup 9200 drop tower system. The rate- and temperature-dependent deformation behavior of polycarbonate was discussed in detail. Dynamic mechanical analysis (DMA) tests were utilized to observe the glass ( α ) transition and the secondary ( β ) transition of polycarbonate. The DMA results indicate that the α and β transitions have a dramatic influence on the mechanical behavior of polycarbonate. The decompose/shift/reconstruct (DSR) method was utilized to decompose the storage modulus into the α and β components and extrapolate the entire modulus, the α-component modulus and the β-component modulus. Based on three previous models, namely, Mulliken-Boyce, G'Sell-Jonas and DSGZ, an adiabatic model is proposed to predict the mechanical behavior of polycarbonate. The model considers the contributions of both the α and β transitions to the mechanical behavior, and it has been implemented in ABAQUS/Explicit through a user material subroutine VUMAT. The model predictions are proven to essentially coincide with the experimental results during compression testing and falling weight impact testing.
Penalty-Based Interface Technology for Prediction of Delamination Growth in Laminated Structures
NASA Technical Reports Server (NTRS)
Averill, Ronald C.
2004-01-01
An effective interface element technology has been developed for connecting and simulating crack growth between independently modeled finite element subdomains (e.g., composite plies). This method has been developed using penalty constraints and allows coupling of finite element models whose nodes do not necessarily coincide along their common interface. Additionally, the present formulation leads to a computational approach that is very efficient and completely compatible with existing commercial software. The present interface element has been implemented in the commercial finite element code ABAQUS as a User Element Subroutine (UEL), making it easy to test the approach for a wide range of problems. The interface element technology has been formulated to simulate delamination growth in composite laminates. Thanks to its special features, the interface element approach makes it possible to release portions of the interface surface whose length is smaller than that of the finite elements. In addition, the penalty parameter can vary within the interface element, allowing the damage model to be applied to a desired fraction of the interface between the two meshes. Results for double cantilever beam DCB, end-loaded split (ELS) and fixed-ratio mixed mode (FRMM) specimens are presented. These results are compared to measured data to assess the ability of the present damage model to simulate crack growth.
Progressive Damage Modeling of Durable Bonded Joint Technology
NASA Technical Reports Server (NTRS)
Leone, Frank A.; Davila, Carlos G.; Lin, Shih-Yung; Smeltzer, Stan; Girolamo, Donato; Ghose, Sayata; Guzman, Juan C.; McCarville, Duglas A.
2013-01-01
The development of durable bonded joint technology for assembling composite structures for launch vehicles is being pursued for the U.S. Space Launch System. The present work is related to the development and application of progressive damage modeling techniques to bonded joint technology applicable to a wide range of sandwich structures for a Heavy Lift Launch Vehicle. The joint designs studied in this work include a conventional composite splice joint and a NASA-patented Durable Redundant Joint. Both designs involve a honeycomb sandwich with carbon/epoxy facesheets joined with adhesively bonded doublers. Progressive damage modeling allows for the prediction of the initiation and evolution of damage. For structures that include multiple materials, the number of potential failure mechanisms that must be considered increases the complexity of the analyses. Potential failure mechanisms include fiber fracture, matrix cracking, delamination, core crushing, adhesive failure, and their interactions. The joints were modeled using Abaqus parametric finite element models, in which damage was modeled with user-written subroutines. Each ply was meshed discretely, and layers of cohesive elements were used to account for delaminations and to model the adhesive layers. Good correlation with experimental results was achieved both in terms of load-displacement history and predicted failure mechanisms.
NASA Technical Reports Server (NTRS)
Wang, John T.; Pineda, Evan J.; Ranatunga, Vipul; Smeltzer, Stanley S.
2015-01-01
A simple continuum damage mechanics (CDM) based 3D progressive damage analysis (PDA) tool for laminated composites was developed and implemented as a user defined material subroutine to link with a commercially available explicit finite element code. This PDA tool uses linear lamina properties from standard tests, predicts damage initiation with an easy-to-implement Hashin-Rotem failure criteria, and in the damage evolution phase, evaluates the degradation of material properties based on the crack band theory and traction-separation cohesive laws. It follows Matzenmiller et al.'s formulation to incorporate the degrading material properties into the damaged stiffness matrix. Since nonlinear shear and matrix stress-strain relations are not implemented, correction factors are used for slowing the reduction of the damaged shear stiffness terms to reflect the effect of these nonlinearities on the laminate strength predictions. This CDM based PDA tool is implemented as a user defined material (VUMAT) to link with the Abaqus/Explicit code. Strength predictions obtained, using this VUMAT, are correlated with test data for a set of notched specimens under tension and compression loads.
NASA Technical Reports Server (NTRS)
Leone, Frank A., Jr.
2015-01-01
A method is presented to represent the large-deformation kinematics of intraply matrix cracks and delaminations in continuum damage mechanics (CDM) constitutive material models. The method involves the additive decomposition of the deformation gradient tensor into 'crack' and 'bulk material' components. The response of the intact bulk material is represented by a reduced deformation gradient tensor, and the opening of an embedded cohesive interface is represented by a normalized cohesive displacement-jump vector. The rotation of the embedded interface is tracked as the material deforms and as the crack opens. The distribution of the total local deformation between the bulk material and the cohesive interface components is determined by minimizing the difference between the cohesive stress and the bulk material stress projected onto the cohesive interface. The improvements to the accuracy of CDM models that incorporate the presented method over existing approaches are demonstrated for a single element subjected to simple shear deformation and for a finite element model of a unidirectional open-hole tension specimen. The material model is implemented as a VUMAT user subroutine for the Abaqus/Explicit finite element software. The presented deformation gradient decomposition method reduces the artificial load transfer across matrix cracks subjected to large shearing deformations, and avoids the spurious secondary failure modes that often occur in analyses based on conventional progressive damage models.
NASA Astrophysics Data System (ADS)
Bong, Hyuk Jong; Barlat, Frédéric; Lee, Myoung-Gyu
2016-08-01
Formability increase in non-conventional forming profiles programmed in the servo-press was investigated using finite element analysis. As an application, forming experiment on a 0.15-mm-thick ferritic stainless steel sheet for a bipolar plate, a primary component of a proton exchange membrane fuel cell, was conducted. Four different forming profiles were considered to investigate the effects of forming profiles on formability and shape accuracy. The four motions included conventional V motion, holding motion, W motion, and oscillating motion. Among the four motions, the holding motion, in which the slide was held for a certain period at the bottom dead point, led to the best formability. Finite element simulations were conducted to validate the experimental results and to probe the formability improvement in the non-conventional forming profiles. A creep model to address stress relaxation effect along with tool elastic recovery was implemented using a user-material subroutine, CREEP in ABAQUS finite element software. The stress relaxation and variable contact conditions during the holding and oscillating profiles were found to be the main mechanism of formability improvement.
NASA Astrophysics Data System (ADS)
Salahouelhadj, A.; Abed-Meraim, F.; Chalal, H.; Balan, T.
2011-05-01
In this contribution, the formulation of the SHB8PS continuum shell finite element is extended to anisotropic elastic-plastic behavior models with combined isotropic-kinematic hardening at large deformations. The resulting element is then implemented into the commercial implicit finite element code Abaqus/Standard via the UEL subroutine. The SHB8PS element is an eight-node, three-dimensional brick with displacements as the only degrees of freedom and a preferential direction called the thickness. A reduced integration scheme is adopted using an arbitrary number of integration points along the thickness direction and only one integration point in the other directions. The hourglass modes due to this reduced integration are controlled using a physical stabilization technique together with an assumed strain method for the elimination of locking. Therefore, the element can be used to model thin structures while providing an accurate description of the various through-thickness phenomena. Its performance is assessed through several applications involving different types of non-linearities: geometric, material and that induced by contact. Particular attention is given to springback prediction for a NUMISHEET benchmark problem.
Hosseinzadeh, M; Ghoreishi, M; Narooei, K
2016-06-01
In this study, the hyperelastic models of demineralized and deproteinized bovine cortical femur bone were investigated and appropriate models were developed. Using uniaxial compression test data, the strain energy versus stretch was calculated and the appropriate hyperelastic strain energy functions were fitted on data in order to calculate the material parameters. To obtain the mechanical behavior in other loading conditions, the hyperelastic strain energy equations were investigated for pure shear and equi-biaxial tension loadings. The results showed the Mooney-Rivlin and Ogden models cannot predict the mechanical response of demineralized and deproteinized bovine cortical femur bone accurately, while the general exponential-exponential and general exponential-power law models have a good agreement with the experimental results. To investigate the sensitivity of the hyperelastic models, a variation of 10% in material parameters was performed and the results indicated an acceptable stability for the general exponential-exponential and general exponential-power law models. Finally, the uniaxial tension and compression of cortical femur bone were studied using the finite element method in VUMAT user subroutine of ABAQUS software and the computed stress-stretch curves were shown a good agreement with the experimental data. PMID:26953961
NASA Astrophysics Data System (ADS)
Alsaleh, Mustafa I.; Voyiadjis, George Z.; Alshibli, Khalid A.
2006-12-01
It has been known that classical continuum mechanics laws fail to describe strain localization in granular materials due to the mathematical ill-posedness and mesh dependency. Therefore, a non-local theory with internal length scales is needed to overcome such problems. The micropolar and high-order gradient theories can be considered as good examples to characterize the strain localization in granular materials. The fact that internal length scales are needed requires micromechanical models or laws; however, the classical constitutive models can be enhanced through the stress invariants to incorporate the Micropolar effects. In this paper, Lade's single hardening model is enhanced to account for the couple stress and Cosserat rotation and the internal length scales are incorporated accordingly. The enhanced Lade's model and its material properties are discussed in detail; then the finite element formulations in the Updated Lagrangian Frame (UL) are used. The finite element formulations were implemented into a user element subroutine for ABAQUS (UEL) and the solution method is discussed in the companion paper. The model was found to predict the strain localization in granular materials with low dependency on the finite element mesh size. The shear band was found to reflect on a certain angle when it hit a rigid boundary. Applications for the model on plane strain specimens tested in the laboratory are discussed in the companion paper. Copyright
NASA Astrophysics Data System (ADS)
Bong, Hyuk Jong; Barlat, Frédéric; Lee, Myoung-Gyu
2016-05-01
Formability increase in non-conventional forming profiles programmed in the servo-press was investigated using finite element analysis. As an application, forming experiment on a 0.15-mm-thick ferritic stainless steel sheet for a bipolar plate, a primary component of a proton exchange membrane fuel cell, was conducted. Four different forming profiles were considered to investigate the effects of forming profiles on formability and shape accuracy. The four motions included conventional V motion, holding motion, W motion, and oscillating motion. Among the four motions, the holding motion, in which the slide was held for a certain period at the bottom dead point, led to the best formability. Finite element simulations were conducted to validate the experimental results and to probe the formability improvement in the non-conventional forming profiles. A creep model to address stress relaxation effect along with tool elastic recovery was implemented using a user-material subroutine, CREEP in ABAQUS finite element software. The stress relaxation and variable contact conditions during the holding and oscillating profiles were found to be the main mechanism of formability improvement.
Alemi-Ardakani, M.; Milani, A. S.; Yannacopoulos, S.
2014-01-01
Impact modeling of fiber reinforced polymer composites is a complex and challenging task, in particular for practitioners with less experience in advanced coding and user-defined subroutines. Different numerical algorithms have been developed over the past decades for impact modeling of composites, yet a considerable gap often exists between predicted and experimental observations. In this paper, after a review of reported sources of complexities in impact modeling of fiber reinforced polymer composites, two simplified approaches are presented for fast simulation of out-of-plane impact response of these materials considering four main effects: (a) strain rate dependency of the mechanical properties, (b) difference between tensile and flexural bending responses, (c) delamination, and (d) the geometry of fixture (clamping conditions). In the first approach, it is shown that by applying correction factors to the quasistatic material properties, which are often readily available from material datasheets, the role of these four sources in modeling impact response of a given composite may be accounted for. As a result a rough estimation of the dynamic force response of the composite can be attained. To show the application of the approach, a twill woven polypropylene/glass reinforced thermoplastic composite laminate has been tested under 200 J impact energy and was modeled in Abaqus/Explicit via the built-in Hashin damage criteria. X-ray microtomography was used to investigate the presence of delamination inside the impacted sample. Finally, as a second and much simpler modeling approach it is shown that applying only a single correction factor over all material properties at once can still yield a reasonable prediction. Both advantages and limitations of the simplified modeling framework are addressed in the performed case study. PMID:25431787
Alemi-Ardakani, M; Milani, A S; Yannacopoulos, S
2014-01-01
Impact modeling of fiber reinforced polymer composites is a complex and challenging task, in particular for practitioners with less experience in advanced coding and user-defined subroutines. Different numerical algorithms have been developed over the past decades for impact modeling of composites, yet a considerable gap often exists between predicted and experimental observations. In this paper, after a review of reported sources of complexities in impact modeling of fiber reinforced polymer composites, two simplified approaches are presented for fast simulation of out-of-plane impact response of these materials considering four main effects: (a) strain rate dependency of the mechanical properties, (b) difference between tensile and flexural bending responses, (c) delamination, and (d) the geometry of fixture (clamping conditions). In the first approach, it is shown that by applying correction factors to the quasistatic material properties, which are often readily available from material datasheets, the role of these four sources in modeling impact response of a given composite may be accounted for. As a result a rough estimation of the dynamic force response of the composite can be attained. To show the application of the approach, a twill woven polypropylene/glass reinforced thermoplastic composite laminate has been tested under 200 J impact energy and was modeled in Abaqus/Explicit via the built-in Hashin damage criteria. X-ray microtomography was used to investigate the presence of delamination inside the impacted sample. Finally, as a second and much simpler modeling approach it is shown that applying only a single correction factor over all material properties at once can still yield a reasonable prediction. Both advantages and limitations of the simplified modeling framework are addressed in the performed case study. PMID:25431787
Growth on demand: Reviewing the mechanobiology of stretched skin
Zöllner, Alexander M.; Holland, Maria A.; Honda, Kord S.; Gosain, Arun K.; Kuhl, Ellen
2013-01-01
Skin is a highly dynamic, autoregulated, living system that responds to mechanical stretch through a net gain in skin surface area. Tissue expansion uses the concept of controlled overstretch to grow extra skin for defect repair in situ. While the short-term mechanics of stretched skin have been studied intensely by testing explanted tissue samples ex vivo, we know very little about the long-term biomechanics and mechanobiology of living skin in vivo. redHere we explore the long-term effects of mechanical stretch on the characteristics of living skin using a mathematical model for skin growth. We review the molecular mechanisms by which skin responds to mechanical loading and model their effects collectively in a single scalar-valued internal variable, the surface area growth. redThis allows us to adopt a continuum model for growing skin based on the multiplicative decomposition of the deformation gradient into a reversible elastic and an irreversible growth part.redTo demonstrate the inherent modularity of this approach, we implement growth as a user-defined constitutive subroutine into the general purpose implicit finite element program Abaqus/Standard. To illustrate the features of the model, we simulate the controlled area growth of skin in response to tissue expansion with multiple filling points in time. Our results demonstrate that the field theories of continuum mechanics can reliably predict the manipulation of thin biological membranes through mechanical overstretch. Our model could serve as a valuable tool to rationalize clinical process parameters such as expander geometry, expander size, filling volume, filling pressure, and inflation timing to minimize tissue necrosis and maximize patient comfort in plastic and reconstructive surgery. While initially developed for growing skin, our model can easily be generalized to arbitrary biological structures to explore the physiology and pathology of stretch-induced growth of other living systems such as hearts
Influence of Finite Element Size in Residual Strength Prediction of Composite Structures
NASA Technical Reports Server (NTRS)
Satyanarayana, Arunkumar; Bogert, Philip B.; Karayev, Kazbek Z.; Nordman, Paul S.; Razi, Hamid
2012-01-01
The sensitivity of failure load to the element size used in a progressive failure analysis (PFA) of carbon composite center notched laminates is evaluated. The sensitivity study employs a PFA methodology previously developed by the authors consisting of Hashin-Rotem intra-laminar fiber and matrix failure criteria and a complete stress degradation scheme for damage simulation. The approach is implemented with a user defined subroutine in the ABAQUS/Explicit finite element package. The effect of element size near the notch tips on residual strength predictions was assessed for a brittle failure mode with a parametric study that included three laminates of varying material system, thickness and stacking sequence. The study resulted in the selection of an element size of 0.09 in. X 0.09 in., which was later used for predicting crack paths and failure loads in sandwich panels and monolithic laminated panels. Comparison of predicted crack paths and failure loads for these panels agreed well with experimental observations. Additionally, the element size vs. normalized failure load relationship, determined in the parametric study, was used to evaluate strength-scaling factors for three different element sizes. The failure loads predicted with all three element sizes provided converged failure loads with respect to that corresponding with the 0.09 in. X 0.09 in. element size. Though preliminary in nature, the strength-scaling concept has the potential to greatly reduce the computational time required for PFA and can enable the analysis of large scale structural components where failure is dominated by fiber failure in tension.
Failure behavior for composite single-bolted joints in double shear tension
NASA Astrophysics Data System (ADS)
Tang, Zhanwen; Liu, Hanyang; Yang, Zhiyong; Shi, Hanqiao; Sun, Baogang
2016-05-01
In order to improve the reliability and load carrying capacity of composite laminates structures which were lap jointed by bolt, in this paper, the failure strength and failure mode of laminated composite pinned-joints is investigated. To determine the effects of joint geometry and stacking sequence on the bearing strength and damage mode, the multi-scale numerical model combining with the Generalized Method of Cells (GMC) and considering the failure and the damage of constituent materials was created based on the ABAQUS and its user subroutine (USDFLD). A three-dimensional finite element technique was used for the stress analysis. Based on the three-dimensional state of stress of each element, different failure modes were detected by the failure theories of constituent materials, all of which are applied at the fiber, matrix and fiber-matrix interface constituent level. Numerical simulations have been carried out by which edge distance-to-hole diameter ratio, and plate width-to-hole diameter ratio are varied, The composite laminated plates are stacked with the following four different orientations: [+45/-45]2s, [90/+45/-45]s, and [0/90/0]s, the results show that failure mode and bearing strength are closely related to by stacking sequence of plates and geometrical parameters. Finally, the ultimate strength and failure modes of composite bolted joints in static tension double-shear loading conditions are predicted by using the progressive damage method established and the effects of layup and dimension of laminates on the properties of the connection structure were researched in this paper. An excellent agreement is found between data obtained from this study and the experiment.
NASA Astrophysics Data System (ADS)
Liu, Hanyang; Tang, Zhanwen; Pan, Lingying; Zhao, Weidong; Sun, Baogang; Jiang, Wenge
2016-05-01
Impact damage has been identified as a critical form of the defects that constantly threatened the reliability of composite structures, such as those used in the aerospace structures and systems. Low energy impacts can introduce barely visible damage and cause the degradation of structural stiffness, furthermore, the flaws caused by low-velocity impact are so dangerous that they can give rise to the further extended delaminations. In order to improve the reliability and load carrying capacity of composite laminates under low-velocity impact, in this paper, the numerical simulatings and experimental studies on the woven fiber-reinforced composite laminates under low-velocity impact with impact energy 16.7J were discussed. The low velocity impact experiment was carried out through drop-weight system as the reason of inertia effect. A numerical progressive damage model was provided, in which the damages of fiber, matrix and interlamina were considered by VUMT subroutine in ABAQUS, to determine the damage modes. The Hashin failure criteria were improved to cover the failure modes of fiber failure in the directions of warp/weft and delaminations. The results of Finite Element Analysis (FEA) were compared with the experimental results of nondestructive examination including the results of ultrasonic C-scan, cross-section stereomicroscope and contact force - time history curves. It is found that the response of laminates under low-velocity impact could be divided into stages with different damage. Before the max-deformation of the laminates occurring, the matrix cracking, fiber breakage and delaminations were simulated during the impactor dropping. During the releasing and rebounding period, matrix cracking and delaminations areas kept increasing in the laminates because of the stress releasing of laminates. Finally, the simulating results showed the good agreements with the results of experiment.
On the mechanics of growing thin biological membranes
Rausch, Manuel K.; Kuhl, Ellen
2013-01-01
Despite their seemingly delicate appearance, thin biological membranes fulfill various crucial roles in the human body and can sustain substantial mechanical loads. Unlike engineering structures, biological membranes are able to grow and adapt to changes in their mechanical environment. Finite element modeling of biological growth holds the potential to better understand the interplay of membrane form and function and to reliably predict the effects of disease or medical intervention. However, standard continuum elements typically fail to represent thin biological membranes efficiently, accurately, and robustly. Moreover, continuum models are typically cumbersome to generate from surface-based medical imaging data. Here we propose a computational model for finite membrane growth using a classical midsurface representation compatible with standard shell elements. By assuming elastic incompressibility and membrane-only growth, the model a priori satisfies the zero-normal stress condition. To demonstrate its modular nature, we implement the membrane growth model into the general-purpose non-linear finite element package Abaqus/Standard using the concept of user subroutines. To probe efficiently and robustness, we simulate selected benchmark examples of growing biological membranes under different loading conditions. To demonstrate the clinical potential, we simulate the functional adaptation of a heart valve leaflet in ischemic cardiomyopathy. We believe that our novel approach will be widely applicable to simulate the adaptive chronic growth of thin biological structures including skin membranes, mucous membranes, fetal membranes, tympanic membranes, corneoscleral membranes, and heart valve membranes. Ultimately, our model can be used to identify diseased states, predict disease evolution, and guide the design of interventional or pharmaceutic therapies to arrest or revert disease progression. PMID:24563551
A viscoplastic model of expanding cylindrical shells subjected to internal explosive detonations
Martineau, R.L.
1998-04-01
Magnetic flux compression generators rely on the expansion of thin ductile shells to generate magnetic fields. These thin shells are filled with high explosives, which when detonated, cause the shell to expand to over 200% strain at strain-rates on the order of 10{sup 4} s{sup {minus}1}. Experimental data indicate the development and growth of multiple plastic instabilities which appear in a quasi-periodic pattern on the surfaces of the shells. These quasi-periodic instabilities are connected by localized zones of intense shear that are oriented approximately 45{degree} from the outward radial direction. The quasi-periodic instabilities continue to develop and eventually become through-cracks, causing the shell to fragment. A viscoplastic constitutive model is formulated to model the high strain-rate expansion and provide insight into the development of plastic instabilities. The formulation of the viscoplastic constitutive model includes the effects of shock heating and damage in the form of microvoid nucleation, growth, and coalescence in the expanding shell. This model uses the Johnson-Cook strength model with the Mie-Grueneisen equation of state and a modified Gurson yield surface. The constitutive model includes the modifications proposed by Tvergaard and the plastic strain controlled nucleation introduced by Neeleman. The constitutive model is implemented as a user material subroutine into ABAQUS/Explicit, which is a commercially available nonlinear explicit dynamic finite element program. A cylindrical shell is modeled using both axisymmetric and plane strain elements. Two experiments were conducted involving plane wave detonated, explosively filled, copper cylinders. Instability, displacement, and velocity data were recorded using a fast framing camera and a Fabry-Perot interferometer. Good agreement is shown between the numerical results and experimental data. An additional explosively bulged cylinder experiment was also performed and a photomicrograph of
On the mechanics of growing thin biological membranes
NASA Astrophysics Data System (ADS)
Rausch, Manuel K.; Kuhl, Ellen
2014-02-01
Despite their seemingly delicate appearance, thin biological membranes fulfill various crucial roles in the human body and can sustain substantial mechanical loads. Unlike engineering structures, biological membranes are able to grow and adapt to changes in their mechanical environment. Finite element modeling of biological growth holds the potential to better understand the interplay of membrane form and function and to reliably predict the effects of disease or medical intervention. However, standard continuum elements typically fail to represent thin biological membranes efficiently, accurately, and robustly. Moreover, continuum models are typically cumbersome to generate from surface-based medical imaging data. Here we propose a computational model for finite membrane growth using a classical midsurface representation compatible with standard shell elements. By assuming elastic incompressibility and membrane-only growth, the model a priori satisfies the zero-normal stress condition. To demonstrate its modular nature, we implement the membrane growth model into the general-purpose non-linear finite element package Abaqus/Standard using the concept of user subroutines. To probe efficiently and robustness, we simulate selected benchmark examples of growing biological membranes under different loading conditions. To demonstrate the clinical potential, we simulate the functional adaptation of a heart valve leaflet in ischemic cardiomyopathy. We believe that our novel approach will be widely applicable to simulate the adaptive chronic growth of thin biological structures including skin membranes, mucous membranes, fetal membranes, tympanic membranes, corneoscleral membranes, and heart valve membranes. Ultimately, our model can be used to identify diseased states, predict disease evolution, and guide the design of interventional or pharmaceutic therapies to arrest or revert disease progression.
Modeling of viscoelasticity and damage in composite laminates by continuum thermodynamics
NASA Astrophysics Data System (ADS)
Ahci, Elif
Time dependent analysis of fiber reinforced polymer matrix composites is essential if these materials are used in applications involving the effect of severe environmental conditions such as high temperature and humidity in addition to mechanical loading. The present research is focused on understanding and modeling the overall nonlinear viscoelastic response of polymer matrix composites incorporating the effects of distributed damage. A constitutive framework incorporating the effect of high temperature and distributed damage is developed for polymer matrix composite laminates. The use of this framework for woven fabric composites is illustrated. The viscoelastic material response and the material properties under severe environmental conditions are studied both theoretically and experimentally. The approach uses continuum thermodynamics based formulation in which stress and temperature are allowed as independent variables along with the so-called hidden variables associated with viscous flow and internal variables representing damage. The damage variables incorporate time-dependent crack separation response as well crack surface orientation. The material coefficients in the polynomial expansion of the free energy are evaluated by a computational model. A user defined material subroutine is developed to include the nonlinear viscoelastic constitutive relations into ABAQUS finite element analysis package in computational study. A combined analytical and numerical procedure to determine the unknown constants in the theoretical model is also presented. The effect of damage on the residual viscoelastic response of the material is studied by experiments to get a satisfactory and complete model. The effect of high temperature on the damage initiation and evolution is studied by microscopic observations of the undamaged and damaged specimen edges, which are exposed to high temperature. A systematic experimental procedure is followed to determine the critical temperature
Axisymmetric whole pin life modelling of advanced gas-cooled reactor nuclear fuel
NASA Astrophysics Data System (ADS)
Mella, R.; Wenman, M. R.
2013-06-01
Thermo-mechanical contributions to pellet-clad interaction (PCI) in advanced gas-cooled reactors (AGRs) are modelled in the ABAQUS finite element (FE) code. User supplied sub-routines permit the modelling of the non-linear behaviour of AGR fuel through life. Through utilisation of ABAQUS's well-developed pre- and post-processing ability, the behaviour of the axially constrained steel clad fuel was modelled. The 2D axisymmetric model includes thermo-mechanical behaviour of the fuel with time and condition dependent material properties. Pellet cladding gap dynamics and thermal behaviour are also modelled. The model treats heat up as a fully coupled temperature-displacement study. Dwell time and direct power cycling was applied to model the impact of online refuelling, a key feature of the AGR. The model includes the visco-plastic behaviour of the fuel under the stress and irradiation conditions within an AGR core and a non-linear heat transfer model. A multiscale fission gas release model is applied to compute pin pressure; this model is coupled to the PCI gap model through an explicit fission gas inventory code. Whole pin, whole life, models are able to show the impact of the fuel on all segments of cladding including weld end caps and cladding pellet locking mechanisms (unique to AGR fuel). The development of this model in a commercial FE package shows that the development of a potentially verified and future-proof fuel performance code can be created and used. The usability of a FE based fuel performance code would be an enhancement over past codes. Pre- and post-processors have lowered the entry barrier for the development of a fuel performance model to permit the ability to model complicated systems. Typical runtimes for a 5 year axisymmetric model takes less than one hour on a single core workstation. The current model has implemented: Non-linear fuel thermal behaviour, including a complex description of heat flow in the fuel. Coupled with a variety of
NASA Astrophysics Data System (ADS)
Schulz, H.-W., , Dr.
2011-09-01
civil customers. These applications cover a wide spectrum from R&D programs for the military customer to special services for the civil customer. This paper focuses on the technical conversion of a commercially available VTOL-UAS to ESG's Unmanned Mission Avionics Test Helicopter (UMAT), its concept and operational capabilities. At the end of the paper, the current integration of a radar sensor is described as an example of the UMATs flexibility. The radar sensor is developed by the Fraunhofer Institute for High Frequency Physics and Radar Techniques (FHR). It is integrated by ESG together with the industrial partner SWISS UAV.
Process Training Derived from a Computer Simulation Theory
ERIC Educational Resources Information Center
Holzman, Thomas G.; And Others
1976-01-01
Discusses a study which investigated whether a computer simulation model could suggest subroutines that were instructable and whether instruction on these subroutines could facilitate subjects' solutions to the problem task. (JM)
CMAQ AEROSOL MODULE DEVELOPMENT RECENT ENHANCEMENTS & FUTURE PLANS
Recent enhancements to the CMAQ aerosol module will be reviewed briefly. These include revision of the secondary organic aerosol subroutine to improve numerical efficiency and control the growth of the accumulation mode standard deviation, revision of the nucleation subroutine t...
The Use of Lotus 1-2-3 Macros in Engineering Calculations.
ERIC Educational Resources Information Center
Rosen, Edward M.
1990-01-01
Described are the use of spreadsheet programs in chemical engineering calculations using Lotus 1-2-3 macros. Discusses the macro commands, subroutine operations, and solution of partial differential equation. Provides examples of the subroutine programs and spreadsheet solution. (YP)
Akterations/corrections to the BRASS Program
NASA Technical Reports Server (NTRS)
Brand, S. N.
1985-01-01
Corrections applied to statistical programs contained in two subroutines of the Bed Rest Analysis Software System (BRASS) are summarized. Two subroutines independently calculate significant values within the BRASS program.
NASA Technical Reports Server (NTRS)
Svalbonas, V.; Ogilvie, P.
1973-01-01
The engineering programming information for the digital computer program for analyzing shell structures is presented. The program is designed to permit small changes such as altering the geometry or a table size to fit the specific requirements. Each major subroutine is discussed and the following subjects are included: (1) subroutine description, (2) pertinent engineering symbols and the FORTRAN coded counterparts, (3) subroutine flow chart, and (4) subroutine FORTRAN listing.
NASA Technical Reports Server (NTRS)
Roth, D. J.; Hull, D. R.
1994-01-01
IMAGEP manipulates digital image data to effect various processing, analysis, and enhancement functions. It is keyboard-driven program organized into nine subroutines. Within subroutines are sub-subroutines also selected via keyboard. Algorithm has possible scientific, industrial, and biomedical applications in study of flows in materials, analysis of steels and ores, and pathology, respectively.
Software development guidelines
NASA Technical Reports Server (NTRS)
Kovalevsky, N.; Underwood, J. M.
1979-01-01
Analysis, modularization, flowcharting, existing programs and subroutines, compatibility, input and output data, adaptability to checkout, and general-purpose subroutines are summarized. Statement ordering and numbering, specification statements, variable names, arrays, arithemtical expressions and statements, control statements, input/output, and subroutines are outlined. Intermediate results, desk checking, checkout data, dumps, storage maps, diagnostics, and program timing are reviewed.
ERIC Educational Resources Information Center
Donohue, Nanette
2008-01-01
No other category of library materials has grown more quickly in the last several decades than audiovisual (AV), nor has any other category undergone so many changes in format. The transitions from vinyl records to 8-tracks to audiocassettes to CDs and from film reel to 3/4" U-Matic to VHS to DVD have impacted library services tremendously. The…
How Well Do Selection Tools Predict Performance Later in a Medical Programme?
ERIC Educational Resources Information Center
Shulruf, Boaz; Poole, Phillippa; Wang, Grace Ying; Rudland, Joy; Wilkinson, Tim
2012-01-01
The choice of tools with which to select medical students is complex and controversial. This study aimed to identify the extent to which scores on each of three admission tools (Admission GPA, UMAT and structured interview) predicted the outcomes of the first major clinical year (Y4) of a 6 year medical programme. Data from three student cohorts…
Shape Memory Alloy Modeling and Applications to Porous and Composite Structures
NASA Astrophysics Data System (ADS)
Zhu, Pingping
There has been a growing concern about an exciting class of advanced material -- shape memory alloys (SMAs) since their discovery several decades ago. SMAs exhibit large reversible stresses and strains owing to a thermoelastic phase transformation. They have been widely used in many engineering fields including aerospace, biomedical, and automotive engineering, especially as sensors, actuators, bone implants and deployable switches. The behavior of SMAs is very complex due to the coupling between thermal and mechanical effects. Theoretical and computational tools are used in this dissertation to investigate the mechanical behavior of SMA and its related structures for seeking better and wider application of this material. In the first part of this dissertation, we proposed an improved macroscopic phenomenological constitutive model of SMA that accounts for all major mechanical behaviors including elasticity, phase transformation, reorientation and plasticity. The model is based on some previous work developed in the Brinson group, and the current efforts are focused on plasticity, the application of a pre-defined strain, unification of notations, and other coding-related work. A user subroutine script VUMAT is developed to implement the constitutive model to the commercial finite element software Abaqus. Typical simulation results based on the model are presented, as well as verification with some experimental results. In the second part, we apply the developed constitutive model to a series of two-dimensional SMA plates with structured arrays of pores to investigate the structural response, especially the stress, strain, phase transformation, and plastic fields. Results are documented about the coupling of the elastic, transformation and plastic fields about the arrays of pores. Theoretical and experimental DIC results are also utilized to validate some simulation results. Conclusions are then drawn to provide understanding in the effect of pores and the
Thermal-mechanical modeling of laser ablation hybrid machining
NASA Astrophysics Data System (ADS)
Matin, Mohammad Kaiser
2001-08-01
materials and contact between workpiece and tool. The theoretical formulation associated with LAHM for solving the thermal-mechanical problem using the finite element method is presented. The thermal formulation is incorporated in the user defined subroutines called by ABAQUS/Standard. The mechanical portion is modeled using ABAQUS/Explicit's general capabilities of modeling interactions involving contact and separation. The results obtained from the FEA simulations showed that the cutting force decrease considerably in both LAEM Surface Absorption (LARM-SA) and LAHM volume absorption (LAHM-VA) models relative to LAM model. It was observed that the HAZ can be expanded or narrowed depending on the laser speed and power. The cutting force is minimal at the last extent of the HAZ. In both the models the laser ablates material thus reducing material stiffness as well as relaxing the thermal stress. The stress values obtained showed compressive yield stress just below the ablated surface and chip. The failure occurs by conventional cutting where tensile stress exceeds the tensile strength of the material at that temperature. In this hybrid machining process the advantages of both the individual machining processes were realized.
Finite Element Models for Electron Beam Freeform Fabrication Process
NASA Technical Reports Server (NTRS)
Chandra, Umesh
2012-01-01
Electron beam freeform fabrication (EBF3) is a member of an emerging class of direct manufacturing processes known as solid freeform fabrication (SFF); another member of the class is the laser deposition process. Successful application of the EBF3 process requires precise control of a number of process parameters such as the EB power, speed, and metal feed rate in order to ensure thermal management; good fusion between the substrate and the first layer and between successive layers; minimize part distortion and residual stresses; and control the microstructure of the finished product. This is the only effort thus far that has addressed computer simulation of the EBF3 process. The models developed in this effort can assist in reducing the number of trials in the laboratory or on the shop floor while making high-quality parts. With some modifications, their use can be further extended to the simulation of laser, TIG (tungsten inert gas), and other deposition processes. A solid mechanics-based finite element code, ABAQUS, was chosen as the primary engine in developing these models whereas a computational fluid dynamics (CFD) code, Fluent, was used in a support role. Several innovative concepts were developed, some of which are highlighted below. These concepts were implemented in a number of new computer models either in the form of stand-alone programs or as user subroutines for ABAQUS and Fluent codes. A database of thermo-physical, mechanical, fluid, and metallurgical properties of stainless steel 304 was developed. Computing models for Gaussian and raster modes of the electron beam heat input were developed. Also, new schemes were devised to account for the heat sink effect during the deposition process. These innovations, and others, lead to improved models for thermal management and prediction of transient/residual stresses and distortions. Two approaches for the prediction of microstructure were pursued. The first was an empirical approach involving the
Nguyen, Ba Nghiep; Wang, Jin
2012-12-01
Under the Predictive Engineering effort, PNNL developed linear and nonlinear property prediction models for long-fiber thermoplastics (LFTs). These models were implemented in PNNL’s EMTA and EMTA-NLA codes. While EMTA is a standalone software for the computation of the composites thermoelastic properties, EMTA-NLA presents a series of nonlinear models implemented in ABAQUS® via user subroutines for structural analyses. In all these models, it is assumed that the fibers are linear elastic while the matrix material can exhibit a linear or typical nonlinear behavior depending on the loading prescribed to the composite. The key idea is to model the constitutive behavior of the matrix material and then to use an Eshelby-Mori-Tanaka approach (EMTA) combined with numerical techniques for fiber length and orientation distributions to determine the behavior of the as-formed composite. The basic property prediction models of EMTA and EMTA-NLA have been subject for implementation in the Autodesk® Moldflow® software packages. These models are the elastic stiffness model accounting for fiber length and orientation distributions, the fiber/matrix interface debonding model, and the elastic-plastic models. The PNNL elastic-plastic models for LFTs describes the composite nonlinear stress-strain response up to failure by an elastic-plastic formulation associated with either a micromechanical criterion to predict failure or a continuum damage mechanics formulation coupling damage to plasticity. All the models account for fiber length and orientation distributions as well as fiber/matrix debonding that can occur at any stage of loading. In an effort to transfer the technologies developed under the Predictive Engineering project to the American automotive and plastics industries, PNNL has obtained the approval of the DOE Office of Vehicle Technologies to provide Autodesk, Inc. with the technical support for the implementation of the basic property prediction models of EMTA and
Computational microstructure modeling of asphalt mixtures subjected to rate-dependent fracture
NASA Astrophysics Data System (ADS)
Aragao, Francisco Thiago Sacramento
2011-12-01
incorporated into the mainframe of ABAQUS in the form of a customized user element (UEL) subroutine. The applicability of the rate-dependent microstructure fracture model is demonstrated and a parametric analysis is performed to evaluate the effects of different mixture parameters on the mechanical behavior of virtually generated hot-mix asphalt (HMA) microstructures. The results presented in this research demonstrate that computational microstructure models, such as the one developed in this study, have a great potential to become efficient design tools for asphalt mixtures and pavement structures.
Behavior of grid-stiffened composite structures under transverse loading
NASA Astrophysics Data System (ADS)
Gan, Changsheng
The energy absorption characteristics and failure modes of grid-stiffened composite plates under transverse load were studied in detail. Several laboratory scale composite grid plates were fabricated by using co-mingled E-glass fiber/polypropylene matrix and carbon/nylon composites in a thermoplastic stamping process. Both experimental and finite element approaches were used to evaluate and understand the role of major failure modes on the performance of damaged grid-stiffened composite plates under transverse load. The load-deflection responses of grid-stiffened composite plates were determined and compared with those of sandwich composite plates of the same size. The failure modes of grid-stiffened composite plates under different load conditions were investigated and used as the basis for FEA models. The intrinsic strength properties of constituent composite materials were measured by using either three point bending or tensile test and were used as input data to the FEA models. Several FEA models including the major failure modes based on the experimental results were built to simulate the damage processes of grid-stiffened composite plates under transverse load. A FORTRAN subroutine was implemented within the ABAQUS code to incorporate the material failure models. Effects of damage on the modal frequencies and loss factors of grid-stiffened composite plates were also investigated experimentally. Experimental and simulation results showed that sandwich composite specimens failed catastrophically with the load dropping sharply at the displacement corresponding to initial and final failure. However, grid-stiffened composite specimens failed in a more gradual and forgiving way in a sequence of relatively small load drops. No catastrophic load drops were observed in the grid structures over the range of displacements investigated here. The SEA values of the grid composite specimens are typically higher than those of the sandwich specimens with the same boundary
Towards an improved understanding of strength and anisotropy of cold compacted powder
NASA Astrophysics Data System (ADS)
Wang, Wenhai
The strength of powder compacts after cold compaction is known to be anisotropic, which comes from the directionality of microstructure resulting from initial particle morphology and/or from particle deformation during compaction. Current work focuses on multi-scale numerical analysis of powder compaction with emphasis on the role of interparticle cohesion on post-compaction mechanical properties. At macroscopic level, we applied phenomenological model to describe the mechanical behavior of powder, in which the material is considered to be continuum medium. A user subroutine (VUMAT) was successfully developed for ABAQUS/Explicit analysis, in which one of the popular phenomenological models for powder compaction---Drucker Prager/Cap model---is implemented. By studying of pharmaceutical powder die compaction and subsequent diametrical compression test via finite element analysis, the capabilities and limitations of current constitutive models are evaluated on predicting such as density, stress and tool force evolution, as well as the strength and fracture tendency. Our results illustrate that current model has good predictive capability of powder densification (e.g. density evolution) but can not predict post-compaction strength well. The following studies focus on evaluating the physics and mechanics occurring at particle level. The compaction of granular media was explored by using MPFEM approach. In the new model, individual particles discretized with a finite element mesh allow for a full description of contact mechanics and local and global particle kinematics. The introduction of a layer of degrading material on the surface of each particle provides the means of introducing variable cohesion and its effect on the final strength of compacts. The simulations show that the unloading creates tensile stresses at the root of the contact necks, which may cause partial or full separation of contact interface when the cohesion developed during loading is not strong
NASA Astrophysics Data System (ADS)
Zampaloni, Michael A.
This work focuses on the development of a constitutive relationship for the modeling of a multi-preferred fiber orientation sheet that has several different primary fiber orientations, none of which are necessarily mutually perpendicular prior to, or during, deformation. One of the goals was to develop the constitutive relationship for the deformation behavior of the fiber mat reinforced thermoplastics with a random orientation, a material that is starting to gain in popularity but has not been extensively investigated. Two different types of mat fiber reinforced material were investigated; one a continuous fiber mat and one a chopped fiber mat, both with a polypropylene matrix. Both materials were characterized through a series of squeeze flow and uniaxial tensile tests to determine the preferred fiber orientations as well as the material properties. The constitutive model was implemented through a user-subroutine into the commercial finite element analysis code ABAQUS/Explicit and the numerical results were validated against experimental stamping results. Overall, the multi-preferred fiber orientation constitutive relationship was able to accurately capture the material instabilities that occurred during the stamping process. Since the mat fiber reinforced materials have not been extensively investigated this research creates one of the building blocks that can be used to develop more accurate models in the future. With the addition of a constitutive relationship for the interaction between the layers, this single layer model could be expanded into a constitutive relationship for the full sheet. In addition to the constitutive modeling aspect of this work there is also an experimental portion that deals with the development, design, build and verification of a new processing method for the shaping and forming of fiber reinforced thermoplastic materials, stamp thermo-hydroforming. Experimentation demonstrated that the process provides a 7--10 percent increase in
Testing and simulation of composite laminates under impact loading
NASA Astrophysics Data System (ADS)
Dang, Xinglai
than improving assembling stiffness in raising perforation resistance. As a first step to simulate composite response to impact loading, LS-DYNA3D was used for numerical analysis. However, due to its inability to describe interlaminar stresses, no delamination simulation could be achieved. As delamination played a very important role in damage process, a computational scheme capable of identifying interlaminar stresses and considering both numerical accuracy and computational efficiency was required for impact simulation. Accounting for interlaminar shear stress continuity and having degrees of freedom independent of layer number, a laminate theory named Generalized Zigzag Theory was formulated into a finite element subroutine and integrated into ABAQUS code. The computational scheme was able to present reasonable interlaminar shear stresses via an updated Lagragian algorithm. Combining the calculated interlaminar stresses with a delamination failure criterion, the computer program was able to predict the response of composite laminates up to the onset of delamination. Further computational simulation involving all damage modes should be considered in future studies.
Generalized continuum modeling of scale-dependent crystalline plasticity
NASA Astrophysics Data System (ADS)
Mayeur, Jason R.
Chapter 2 from a unified dislocation-based perspective. The discussion of the continuum crystal plasticity theories is prefaced by a brief review of discrete dislocation plasticity, which facilitates the comparison of certain model aspects and also serves as a reference for latter segments of the research which make connection to this constitutive description. Chapter 2 has utility not only as a literature review, but also as a synthesis and analysis of competing and alternative nonlocal crystal plasticity modeling strategies from a common viewpoint. The micropolar theory of single crystal plasticity is presented in Chapter 3. Two different types of flow criteria are considered - the so-called single and multicriterion theories, and several variations of the dislocation-based strength models appropriate for each theory are presented and discussed. The numerical implementation of the two-dimensional version of the constitutive theory is given in Chapter 4. A user element subroutine for the implicit commercial finite element code Abaqus/Standard is developed and validated through the solution of initial-boundary value problems with closed-form solutions. Convergent behavior of the subroutine is also demonstrated for an initial-boundary value problem exhibiting strain localization. In Chapter 5, the models are employed to solve several standard initial-boundary value problems for heterogeneously deforming single crystals including simple shearing of a semi-infinite constrained thin film, pure bending of thin films, and simple shearing of a metal matrix composite with elastic inclusions. The simulation results are compared to those obtained from the solution of equivalent boundary value problems using discrete dislocation dynamics and alternative generalized crystal plasticity theories. Comparison and calibration with respect to the former provides guidance in the specification of non-traditional material parameters that arise in the model formulation and demonstrates its
Bracken, Robert E.
2004-01-01
A subroutine (FFTDC2) coded in Fortran 77 is described, which performs a Fast Fourier Transform or Discrete Fourier Transform together with necessary conditioning steps of trend removal, extension, and windowing. The source code for the entire library of required subroutines is provided with the digital release of this report. But, there is only one required entry point, the subroutine call to FFTDC2; all the other subroutines are operationally transparent to the user. Complete instructions for use of FFTDC2.F (as well as for all the other subroutines) and some practical theoretical discussions are included as comments at the beginning of the source code. This subroutine is intended to be an efficient tool for the programmer in a variety of production-level signal-processing applications.
PLOT300: A Tektronics PLOT10 emulator for HP 9000 series 200/300 computers
NASA Technical Reports Server (NTRS)
Kjelgaard, Scott O.
1988-01-01
A software package which emulates the Tektronics PLOT10 Graphics package on Hewlett-Packard 9000 Series 200/300 computers is described. The Software is written in HP Rocky Mountain BASIC and can be run under BASIC revisions 3.0 and 4.0. Although this subroutine library emulates a subset of PLOT10, several subroutines have been added which enhance basic plot generation. Example codes using PLOT300 and descriptions of the subroutines are included in the text.
NASA Technical Reports Server (NTRS)
Labudde, R. A.
1972-01-01
An attempt has been made to keep the programs as subroutine oriented as possible. Usually only the main programs are directly concerned with the problem of total cross sections. In particular the subroutines POLFIT, BILINR, GASS59/MAXLIK, SYMOR, MATIN, STUDNT, DNTERP, DIFTAB, FORDIF, EPSALG, REGFAL and ADSIMP are completely general, and are concerned only with the problems of numerical analysis and statistics. Each subroutine is independently documented.
Computer program for natural gas flow through nozzles
NASA Technical Reports Server (NTRS)
Johnson, R. C.
1972-01-01
Subroutines, FORTRAN 4 type, were developed for calculating isentropic natural gas mass flow rate through nozzle. Thermodynamic functions covering compressibility, entropy, enthalpy, and specific heat are included.