scholarly journals SCARE: A Postprocessor Program to MSC/NASTRAN for Reliability Analysis of Structural Ceramic Components

1986 ◽  
Vol 108 (3) ◽  
pp. 540-546 ◽  
Author(s):  
J. P. Gyekenyesi
Keyword(s):  
Least Squares Method ◽  
Three Dimensional ◽  
Strain Energy Release ◽  
Maximum Tensile Stress ◽  
Strength Distribution ◽  
Modulus Of Rupture ◽  
Distribution Model ◽  
Mixed Mode Fracture ◽  
Ceramic Components ◽  
Fast Fracture

A computer program is developed for calculating the statistical fast fracture reliability and failure probability of ceramic components. The program includes the two-parameter Weibull material fracture strength distribution model, using the principle of independent action for polyaxial stress states and Batdorf’s shear-sensitive as well as shear-insensitive crack theories, all for volume distributed flaws in macroscopically isotropic solids. Both penny-shaped cracks and Griffith cracks are included in the Batdorf shear-sensitive crack response calculations, using Griffith’s maximum tensile stress or critical coplanar strain energy release rate criteria to predict mixed mode fracture. Weibull material parameters can also be calculated from modulus of rupture bar tests, using the least-squares method with known specimen geometry and fracture data. The reliability prediction analysis uses MSC/NASTRAN stress, temperature, and volume output, obtained from the use of three-dimensional, quadratic, isoparametric, or axisymmetric finite elements. The statistical fast fracture theories employed, along with selected input and output formats and options, are summarized. A sample problem to demonstrate various features of the program is included.

scholarly journals Surface Flaw Reliability Analysis of Ceramic Components With the SCARE Finite Element Postprocessor Program

1987 ◽  
Vol 109 (3) ◽  
pp. 274-281 ◽  
Author(s):  
J. P. Gyekenyesi ◽  
N. N. Nemeth
Keyword(s):  
Finite Element ◽  
Finite Elements ◽  
Reliability Analysis ◽  
Surface Flaw ◽  
Modulus Of Rupture ◽  
Distribution Model ◽  
External Boundary ◽  
Mixed Mode Fracture ◽  
Boundary Area ◽  
Fast Fracture

The SCARE (Structural Ceramics Analysis and Reliability Evaluation) computer program on statistical fast fracture reliability analysis with quadratic elements for volume-distributed imperfections is enhanced to include the use of linear finite elements and the capability of designing against concurrent surface flaw-induced ceramic component failure. The SCARE code is presently coupled as a postprocessor to the MSC/NASTRAN general purpose, finite element analysis program. The improved version now includes the Weibull and Batdorf statistical failure theories for both surface and volume flaw-based reliability analysis. The program uses the two-parameter Weibull fracture strength cumulative failure probability distribution model with the principle of independent action for polyaxial stress states, and Batdorf’s shear-sensitive as well as shear-insensitive statistical theories. The shear-sensitive surface crack configurations include the Griffith crack and Griffith notch geometries, using the total critical coplanar strain energy release rate criterion to predict mixed-mode fracture. Weibull material parameters based on both surface and volume flaw-induced fracture can also be calculated from modulus of rupture bar tests, using the least-squares method with known specimen geometry and grouped fracture data. The surface flaw reliability prediction uses MSC/NASTRAN stress, temperature, and external boundary area output, obtained from the use of linear or quadratic shell and three-dimensional isoparametric finite elements. The statistical fast fracture theories for surface flaw-induced failure, along with selected input and output formats and options, are summarized. A sample problem to demonstrate various features of the program is included.

Modeling of Threshold Strength in Cylindrical Ceramic Structures

2005 ◽  
Vol 72 (3) ◽  
pp. 381-388 ◽  
Author(s):  
Fjo´la Jo´nsdo´ttir ◽  
Glenn E. Beltz ◽  
Robert M. McMeeking
Keyword(s):  
Ceramic Body ◽  
Three Dimensional ◽  
Element Model ◽  
Ceramic Composites ◽  
Strength Distribution ◽  
Penny Shaped Crack ◽  
Ceramic Components ◽  
Threshold Strength ◽  
Shaped Crack ◽  
Residual Compression

Recently, three-dimensional structured ceramic composites with large threshold strengths (i.e., stress below which there is zero probability of failure) have been fabricated utilizing an architecture consisting of relatively stress-free, elongated prismatic domains, separated by thin compressive walls. We build upon prior work on laminate architectures, with the common feature that these structures are all susceptible to fracture. Typically, these three-dimensional structures consist of thin shells of mullite that surround alumina. Cracks, originating from large flaws within the ceramic body, are arrested by the surrounding compressive layers until a specific stress level is attained (i.e., the threshold strength), resulting in a truncation of the strength distribution in the flaw region. A preliminary stress intensity solution has shown that this arrest is caused by a reduction of the crack driving force by the residual compression in the compressive walls. This solution also predicts that the threshold strength is dependent not only on the magnitude of the residual compression in the walls but also on the dimensions of both phases. A finite element model is presented that utilizes a penny-shaped crack in the interior of such a structure or half-penny-shaped crack emanating from the edge of such a structure. Ongoing analytical and experimental work that is needed to more fully understand this arrest phenomenon and its application towards the development of reliable, damage-tolerant ceramic components are discussed.

Failure Prediction Using the Ring-on-Ring Test and the CARES/LIFE Integrated Design Program

1993 ◽  
Author(s):  
Lynn M. Powers ◽  
Jonathan A. Salem ◽  
Sung R. Choi
Keyword(s):  
Integrated Design ◽  
Strain Energy Release ◽  
Strength Distribution ◽  
Time Dependent ◽  
Cumulative Distribution ◽  
Ring Test ◽  
Soda Lime Glass ◽  
Element Analysis ◽  
Design Program ◽  
Fast Fracture

Abstract The integrated design program CARES/LIFE calculates the fast-fracture and time-dependent reliability of monolithic ceramic components subjected to thermomechanical loading. A summary of the program capability is included in the paper. This program is an extension of the CARES (Ceramics Analysis and Reliability Evaluation of Structures) computer program. The results from finite element analysis are used to evaluate component reliability due to inherent surface and/or volume flaws. The two-parameter Weibull cumulative distribution function is used to characterize the variation in component strength. The fast-fracture strength of sintered alpha silicon carbide tested in three- and four-point bend was used to predict the failure strength distribution of ring-on-ring tests. The specimens were tested in the annealed conditions. CARES/LIFE predicted the biaxial failure accurately when the noncoplanar strain energy release rate criterion was applied. For time-dependent life prediction, dynamic fatigue ring-on-ring test data on soda-lime glass is used to demonstrate the fatigue parameter estimation capability of CARES/LIFE.

scholarly journals Mesh size sensitivity analysis for interlaminar fracture of the fiber-reinforced laminated composites

2019 ◽  
Vol 14 ◽  
pp. 155892501988346 ◽  
Author(s):  
Fatih Daricik
Keyword(s):  
Crack Closure ◽  
Strain Energy ◽  
Three Dimensional ◽  
Laminated Composite ◽  
Mesh Size ◽  
Strain Energy Release ◽  
Virtual Crack Closure Technique ◽  
Closure Technique ◽  
Interlaminar Fracture ◽  
Element Size

The virtual crack closure technique is a well-known finite element–based numerical method used to simulate fractures and it suits well to both of two-dimensional and three-dimensional interlaminar fracture analysis. In particular, strain energy release rate during a three-dimensional interlaminar fracture of laminated composite materials can successfully be computed using the virtual crack closure technique. However, the element size of a numerical model is an important concern for the success of the computation. The virtual crack closure technique analysis with a finer mesh converges the numerical results to experimental ones although such a model may need excessive modeling and computing times. Since, the finer element size through a crack path causes oscillation of the stresses at the free ends of the model, the plies in the delaminated zone may overlap. To eliminate this problem, the element size for the virtual crack closure technique should be adjusted to ascertain converged yet not oscillating results with an admissible processing time. In this study, mesh size sensitivity of the virtual crack closure technique is widely investigated for mode I and mode II interlaminar fracture analyses of laminated composite material models by considering experimental force and displacement responses of the specimens. Optimum sizes of the finite elements are determined in terms of the force, the displacement, and the strain energy release rate distribution along the width of the model.

Crystal and molecular structure of heptacain hydrochloride

1986 ◽  
Vol 51 (2) ◽  
pp. 264-270 ◽  
Author(s):  
František Pavelčík ◽  
Milan Remko ◽  
Jozef Čižmárik ◽  
Jaroslav Majer
Keyword(s):  
Molecular Structure ◽  
Least Squares Method ◽  
Crystal And Molecular Structure ◽  
Three Dimensional ◽  
Chair Conformation ◽  
Piperidine Ring ◽  
Side Chain ◽  
Ring Plane ◽  
Benzene Ring Plane ◽  
Carbamate Group

The crystal and molecular structure of heptacain hydrochloride was determined from three-dimensional diffractometric data. The carbamate group was found to be rotated out of the benzene ring plane by 15.5°, whilst the piperidine ring is in a more stable chair conformation. The heptyloxy side chain is in a stable all-trans conformation. The structure was refined by the full matrix least-squares method to a final R value 0.1127 for the observed reflections.

Simulation of Three-Dimensional Stress Distribution in Compression Dies

2008 ◽  
Vol 575-578 ◽  
pp. 449-454
Author(s):  
Chu Yun Huang ◽  
Sai Yu Wang ◽  
Tao Yang ◽  
Xu Dong Yan
Keyword(s):  
Stress Distribution ◽  
Computer Aided Design ◽  
Three Dimensional ◽  
Distribution Model ◽  
Extrusion Dies ◽  
Maximum Value ◽  
Multiple Unit ◽  
Stress Freezing Method ◽  
Experimental Values ◽  
Aided Design

The stress fields of rectangular and T shape compression dies were simulated by three dimensional photo-elasticity of stress freezing method. The rules of stress distribution of σx, σy, σz on the surface of rectangular and T-shaped dies were discovered, and the rules were also found inside the dies. The results indicate that the stress distribution of rectangular die is similar to that of T shape die. Obvious stress concentration in corner of die hole was observed. σz rises from die hole to periphery until it achieves maximum value then it diminishes gradually, and σz between die hole and fix diameter zone is higher than it is in other position. At the same time, the equations of stress field of extrusion dies were obtained by curved surface fitting experimental values in every observed point with multiple-unit regression analysis method and orthogonal transforms. These works can provide stress distribution model for die computer aided design and make.

Shape and energies of a dynamically propagating crack under bending

2003 ◽  
Vol 18 (10) ◽  
pp. 2379-2386 ◽  
Author(s):  
Dov Sherman ◽  
Ilan Be'ery
Keyword(s):  
Crack Propagation ◽  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Crack Front ◽  
Three Dimensional ◽  
Strain Energy Release ◽  
Governing Parameter ◽  
Propagating Crack ◽  
Front Shape

We report on the exact shape of a propagating crack in a plate with a high width/thickness ratio and subjected to bending deformation. Fracture tests were carried out with brittle solids—single crystal, polycrystalline, and amorphous. The shape of the propagating crack was determined from direct temporal crack length measurements and from the surface perturbations generated during rapid crack propagation. The shape of the crack profile was shown to be quarter-elliptical with a straight, long tail; the governing parameter of the ellipse axes is the specimen's thickness at most length of crack propagation. Universality of the crack front shape is demonstrated. The continuum mechanics approach applicable to two-dimensional problems was used in this three-dimensional problem to calculate the quasistatic strain energy release rate of the propagating crack using the formulations of the dynamic energy release rate along the crack loci. Knowledge of the crack front shape in the current geometry and loading configuration is important for practical and scientific aspects.

THEORETICAL TRANSITION PROBABILITIES FOR THE $\tilde{A}^{2}A_{1} -\tilde{X}^{2}B_{1}$ SYSTEM OF H2O+ AND D2O+ AND RELATED FRANCK–CONDON FACTORS BASED ON GLOBAL POTENTIAL ENERGY SURFACES

2005 ◽  
Vol 04 (01) ◽  
pp. 225-245 ◽  
Author(s):  
IKUO TOKUE ◽  
KATSUYOSHI YAMASAKI ◽  
SATOSHI MINAMINO ◽  
SHINKOH NANBU
Keyword(s):  
Potential Energy ◽  
Photoelectron Spectroscopy ◽  
Potential Energy Surfaces ◽  
Least Squares Method ◽  
Transition Probabilities ◽  
Three Dimensional ◽  
Equilibrium Geometry ◽  
Condon Factors ◽  
Energy Surfaces ◽  
Franck Condon

To elucidate the ionization dynamics, in particular the vibrational distribution, of H 2 O +(Ã) produced by photoionization and the Penning ionization of H 2 O and D 2 O with He *(2 3S) atoms, Franck–Condon factors (FCFs) were given for the [Formula: see text] ionization, and the transition probabilities were presented for the [Formula: see text] emission. The FCFs were obtained by quantum vibrational calculations using the three-dimensional potential energy surfaces (PESs) of [Formula: see text] and [Formula: see text] electronic states. The global PESs were determined by the multi-reference configuration interaction calculations with the Davidson correction and the interpolant moving least squares method combined with the Shepard interpolation. The obtained FCFs exhibit that the [Formula: see text] state primarily populates the vibrational ground state, as its equilibrium geometry is almost equal to that of [Formula: see text], while the bending mode (ν2) is strongly enhanced for the H 2 O +(Ã) state; the maximums in the population of H 2 O + and D 2 O + are approximately v2 = 11–12 and 15–17, respectively. These results are consistent with the distributions observed by photoelectron spectroscopy. Transition probabilities for the [Formula: see text] system of H 2 O + and D 2 O + show that the bending progressions consist primarily of the [Formula: see text] emission, with combination bands from the (1, v′2 = 4–8, 0) level being next most important.

The Strength Evaluation and Reliability Analysis of Periodic Symmetric Struts Support

2011 ◽  
Vol 462-463 ◽  
pp. 1164-1169
Author(s):  
Jing Xiang Yang ◽  
Ya Xin Zhang ◽  
Mamtimin Gheni ◽  
Ping Ping Chang ◽  
Kai Yin Chen ◽  
...  
Keyword(s):  
Distribution Function ◽  
Probability Distribution ◽  
Stress Distribution ◽  
Least Squares ◽  
Reliability Analysis ◽  
Least Squares Method ◽  
Nonlinear Least Squares ◽  
Distribution Model ◽  
Different Types ◽  
Nonlinear Least Squares Method

In this paper, strength evaluations and reliability analysis are conducted for different types of PSSS(Periodically Symmetric Struts Supports) based on the FEA(Finite Element Analysis). The numerical models are established at first, and the PMA(Prestressed Modal Analysis) is conducted. The nodal stress value of all of the gauss points in elements are extracted out and the stress distributions are evaluated for each type of PSSS. Then using nonlinear least squares method, curve fitting is carried out, and the stress probability distribution function is obtained. The results show that although using different number of struts, the stress distribution function obeys the exponential distribution. By using nonlinear least squares method again for the distribution parameters a and b of different exponential functions, the relationship between number of struts and distribution function is obtained, and the mathematical models of the stress probability distribution functions for different supports are established. Finally, the new stress distribution model is introduced by considering the DSSI(Damaged Stress-Strength Interference), and the reliability evaluation for different types of periodically symmetric struts supports is carried out.

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