Failure Modeling and Sensitivity Analysis of Ceramics Under Impact

2021 ◽  
Vol 88 (5) ◽  
Author(s):  
Amartya Bhattacharjee ◽  
Anindya Bhaduri ◽  
Ryan C. Hurley ◽  
Lori Graham-Brady
Keyword(s):  
Boron Carbide ◽  
Granular Flow ◽  
Integrative Model ◽  
Model Parameters ◽  
Physical Mechanisms ◽  
Failure Modeling ◽  
Materials By Design ◽  
Model Predictions ◽  
Physics Model ◽  
Impact Experiments

Abstract A micromechanical multi-physics model for ceramics has been recalibrated and used to simulate impact experiments with boron carbide in abaqus. The dominant physical mechanisms in boron carbide have been identified and simulated in the framework of an integrated constitutive model that combines crack growth, amorphization, and granular flow. The integrative model is able to accurately reproduce some of the key cracking patterns of Sphere Indentation experiments and Edge On Impact experiments. Based on this integrative model, linear regression has been used to study the sensitivity of sphere indentation model predictions to the input parameters. The sensitivities are connected to physical mechanisms, and trends in model outputs have been intuitively explored. These results help suggest material modifications that might improve material performance, prioritize calibration experiments for materials-by-design iterations, and identify model parameters that require more in-depth understanding.

scholarly journals Noninteractive Macroscopic Reliability Model for Ceramic Matrix Composites With Orthotropic Material Symmetry

1990 ◽  
Vol 112 (4) ◽  
pp. 507-511 ◽  
Author(s):  
S. F. Duffy ◽  
J. M. Manderscheid
Keyword(s):  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Experimental Program ◽  
Type Model ◽  
Model Parameters ◽  
Reliability Model ◽  
Matrix Composites ◽  
Physical Mechanisms ◽  
Weakest Link ◽  
Monolithic Ceramics

A macroscopic noninteractive reliability model for ceramic matrix composites is presented. The model is multiaxial and applicable to composites that can be characterized as orthotropic. Tensorial invariant theory is used to create an integrity basis with invariants that correspond to physical mechanisms related to fracture. This integrity basis is then used to construct a failure function per unit volume (or area) of material. It is assumed that the overall strength of the composite is governed by weakest link theory. This leads to a Weibull-type model similar in nature to the principle of independent action (PIA) model for isotropic monolithic ceramics. An experimental program to obtain model parameters is briefly discussed. In addition, qualitative features of the model are illustrated by presenting reliability surfaces for various model parameters.

Multivariate probabilistic rock physics models using Kumaraswamy distributions

Geophysics ◽  
2021 ◽  
pp. 1-43
Author(s):  
Dario Grana
Keyword(s):  
Probability Density Function ◽  
Probability Density ◽  
Density Function ◽  
Random Variables ◽  
Rock Physics ◽  
Petrophysical Properties ◽  
Kumaraswamy Distribution ◽  
Model Predictions ◽  
Physics Model ◽  
Rock Physics Model

Rock physics models are physical equations that map petrophysical properties into geophysical variables, such as elastic properties and density. These equations are generally used in quantitative log and seismic interpretation to estimate the properties of interest from measured well logs and seismic data. Such models are generally calibrated using core samples and well log data and result in accurate predictions of the unknown properties. Because the input data are often affected by measurement errors, the model predictions are often uncertain. Instead of applying rock physics models to deterministic measurements, I propose to apply the models to the probability density function of the measurements. This approach has been previously adopted in literature using Gaussian distributions, but for petrophysical properties of porous rocks, such as volumetric fractions of solid and fluid components, the standard probabilistic formulation based on Gaussian assumptions is not applicable due to the bounded nature of the properties, the multimodality, and the non-symmetric behavior. The proposed approach is based on the Kumaraswamy probability density function for continuous random variables, which allows modeling double bounded non-symmetric distributions and is analytically tractable, unlike the Beta or Dirichtlet distributions. I present a probabilistic rock physics model applied to double bounded continuous random variables distributed according to a Kumaraswamy distribution and derive the analytical solution of the posterior distribution of the rock physics model predictions. The method is illustrated for three rock physics models: Raymer’s equation, Dvorkin’s stiff sand model, and Kuster-Toksoz inclusion model.

Experiences with computer simulation at two large wastewater treatment plants in northern Poland

2002 ◽  
Vol 45 (6) ◽  
pp. 209-218 ◽  
Author(s):  
J. Makinia ◽  
M. Swinarski ◽  
E. Dobiegala
Keyword(s):  
Computer Simulation ◽  
Wastewater Treatment ◽  
Nutrient Removal ◽  
Wastewater Treatment Plants ◽  
Biological Nutrient Removal ◽  
Model Parameters ◽  
Total N ◽  
Northern Poland ◽  
Model Predictions ◽  
Steady State Simulation

Mathematical modelling and computer simulation have became a useful tool in evaluating the operation of wastewater treatment plants (WWTPs) in terms of nutrient removal capability. In this study, steady-state simulation results for two large biological nutrient removal WWTPs are presented. The plants are located in two neighbouring cities Gdansk and Gdynia in northern Poland. Simulations were performed using a pre-compiled model and layouts (MUCT and Johannesburg processes) implemented in the GPS-X simulation package. The monthly average values of conventional parameters, such as COD, Total Suspended Solids, total N, N-NH4+, P-PO4− were used as input data. The measured effluent concentrations of COD, N-NH4+, N-NO3− and P-PO4− as well as reactor MLSS were compared with model predictions. During calibration, performed from the process engineering perspective, default values of only five model parameters were changed. The opportunities for further applications of such models in municipal WWTPs are discussed.

scholarly journals The Magnetized Disk-Halo Transition Region of M51

2018 ◽  
Vol 14 (A30) ◽  
pp. 319-322 ◽  
Author(s):  
M. Kierdorf ◽  
S. A. Mao ◽  
A. Fletcher ◽  
R. Beck ◽  
M. Haverkorn ◽  
...  
Keyword(s):  
Transition Region ◽  
Large Scale ◽  
Model Parameters ◽  
Very Large Array ◽  
X Band ◽  
Model Predictions ◽  
The Galaxy ◽  
Linearly Polarized ◽  
Grand Design ◽  
Different Depths

AbstractAn excellent laboratory for studying large scale magnetic fields is the grand design face-on spiral galaxy M51. Due to wavelength-dependent Faraday depolarization, linearly polarized synchrotron emission at different radio frequencies gives a picture of the galaxy at different depths: Observations at L-band (1 – 2 GHz) probe the halo region while at C- and X-band (4 – 8 GHz) the linearly polarized emission probe the disk region of M51. We present new observations of M51 using the Karl G. Jansky Very Large Array (VLA) at S-band (2 – 4 GHz), where previously no polarization observations existed, to shed new light on the transition region between the disk and the halo. We discuss a model of the depolarization of synchrotron radiation in a multilayer magneto-ionic medium and compare the model predictions to the multi-frequency polarization data of M51 between 1 – 8 GHz. The new S-band data are essential to distinguish between different models. Our study shows that the initial model parameters, i.e. the total regular and turbulent magnetic field strengths in the disk and halo of M51, need to be adjusted to successfully fit the models to the data.

scholarly journals A Toolkit tot Study Sensitivity of the Geant4 Predictions to the Variations of the Physics Model Parameters

2017 ◽  
Author(s):  
K. L. Genser ◽  
◽  
R. Hatcher ◽  
G. Perdue ◽  
H. Wenzel ◽  
...  
Keyword(s):  
Model Parameters ◽  
Physics Model

Viscoelastic behavior of an epoxy resin during cure below the glass transition temperature: Characterization and modeling

2018 ◽  
Vol 53 (2) ◽  
pp. 155-171 ◽  
Author(s):  
Alice Courtois ◽  
Martin Hirsekorn ◽  
Maria Benavente ◽  
Agathe Jaillon ◽  
Lionel Marcin ◽  
...  
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Epoxy Resin ◽  
Viscoelastic Behavior ◽  
Mechanical Analysis ◽  
Strain History ◽  
Model Parameters ◽  
Degree Of Cure ◽  
Model Predictions

This paper presents a viscoelastic temperature- and degree-of-cure-dependent constitutive model for an epoxy resin. Multi-temperature relaxation tests on fully and partially cured rectangular epoxy specimens were conducted in a dynamic mechanical analysis apparatus with a three-point bending clamp. Master curves were constructed from the relaxation test results based on the time–temperature superposition hypothesis. The influence of the degree of cure was included through the cure-dependent glass transition temperature which was used as reference temperature for the shift factors. The model parameters were optimized by minimization of the differences between the model predictions and the experimental data. The model predictions were successfully validated against an independent creep-like strain history over which the temperature varied.

scholarly journals On acceleration of <1 MeV/n He ions in the corotating compression regions near 1 AU: STEREO observations

2009 ◽  
Vol 27 (9) ◽  
pp. 3677-3690 ◽  
Author(s):  
R. Bučík ◽  
U. Mall ◽  
A. Korth ◽  
G. M. Mason
Keyword(s):  
Solar Wind ◽  
Total Pressure ◽  
Solar Wind Speed ◽  
Shock Acceleration ◽  
Model Parameters ◽  
Corotating Interaction Region ◽  
Reverse Shock ◽  
Compression Region ◽  
Model Predictions

Abstract. Observations of multi-MeV corotating interaction region (CIR) ions are in general consistent with models of CIR shock acceleration and transport. The presence of suprathermal particles near 1 AU in unshocked compression regions is not adequately explained. Nonetheless, more recent works demonstrate that unshocked compression regions associated with CIRs near 1 AU could energize particles. In the energy range from ~0.1 to ~1 MeV/n we investigate CIR events observed in 2007–2008 by the STEREO A and B spacecraft. We treat the predictions of compression acceleration by comparing the observed ion intensities with the model parameters. These observations show that the ion intensity in CIR events with in-situ reverse shock is well organized by the parameters which characterize the compression region itself, like compression width, solar wind speed gradients and the total pressure. In turn, for CIR events with the absence of the shocks the model predictions are not fulfilled.

scholarly journals Comparison of three Models of Avalanche Dynamics

1989 ◽  
Vol 13 ◽  
pp. 82-89 ◽  
Author(s):  
H. Gubler
Keyword(s):  
Differential Equation ◽  
Granular Flow ◽  
Flow Model ◽  
Model Parameters ◽  
Field Observations ◽  
Segmentation Method ◽  
Avalanche Dynamics ◽  
Flow Speeds ◽  
Avalanche Flow ◽  
Longitudinal Profiles

Results and characteristics of three models for estimating avalanche flow speeds, flow heights, and run-out distances are compared: (1) Voellmy–Salm equation used with the traditional release, track, and run-out segmentation method; (2) Voellmy–Salm differential equation solved numerically along longitudinal profiles of avalanche paths, combined with modified assumptions for the flow in the run-out zone; (3) a granular-flow model introduced by Salm and Gubler. Within the limits of the accuracy of the field observations, all models are able to predict run-out distances correctly, at least for large avalanches, but the Voellmy–Salm type models significantly underestimate flow speeds. Modelling different flow regimes (sliding and partial fluidization) increases the range of avalanche sizes for which correct run-out modelling is possible without recalibration of model parameters.

scholarly journals Comparison of three Models of Avalanche Dynamics

1989 ◽  
Vol 13 ◽  
pp. 82-89 ◽  
Author(s):  
H. Gubler
Keyword(s):  
Differential Equation ◽  
Granular Flow ◽  
Flow Model ◽  
Model Parameters ◽  
Field Observations ◽  
Segmentation Method ◽  
Avalanche Dynamics ◽  
Flow Speeds ◽  
Avalanche Flow ◽  
Longitudinal Profiles

Results and characteristics of three models for estimating avalanche flow speeds, flow heights, and run-out distances are compared: (1) Voellmy–Salm equation used with the traditional release, track, and run-out segmentation method; (2) Voellmy–Salm differential equation solved numerically along longitudinal profiles of avalanche paths, combined with modified assumptions for the flow in the run-out zone; (3) a granular-flow model introduced by Salm and Gubler. Within the limits of the accuracy of the field observations, all models are able to predict run-out distances correctly, at least for large avalanches, but the Voellmy–Salm type models significantly underestimate flow speeds. Modelling different flow regimes (sliding and partial fluidization) increases the range of avalanche sizes for which correct run-out modelling is possible without recalibration of model parameters.

Modification of a Predictive Model To Include the Influence of Fat Content on Salmonella Inactivation in Low-Water-Activity Foods

2020 ◽  
Vol 83 (5) ◽  
pp. 801-815
Author(s):  
LISA M. TRIMBLE ◽  
JOSEPH F. FRANK ◽  
DONALD W. SCHAFFNER
Keyword(s):  
Water Activity ◽  
Survival Data ◽  
Peanut Butter ◽  
Weibull Model ◽  
Fat Content ◽  
Mitigation Strategies ◽  
Model Parameters ◽  
Least Squares Regression ◽  
Salmonella Spp ◽  
Model Predictions

ABSTRACT Low-water-activity (aw) foods (including those containing fat) are often implicated in outbreaks of Salmonella spp. The influence of fat content on survival in foods such as peanut butter remains unclear. Certain Salmonella serovars can survive for long periods in harsh temperatures and low moisture conditions. The objective of this study was to determine the influence of fat content on the survival of Salmonella in low-aw foods and expand an existing secondary inactivation model previously validated for lower-fat foods. Whey protein powder supplemented with peanut oil was equilibrated to five target aw values (aw &lt; 0.60), inoculated with a dried four-strain cocktail of Salmonella, vacuum sealed, and stored at 22, 37, 50, 60, 70, and 80°C for 48 h, 28 days, or 168 days. Survival data were fitted to Weibull, Biphasic-linear, Double Weibull, and Geeraerd-tail models. The Weibull model was chosen for secondary modeling due to its ability to satisfactorily describe the data over most of the conditions under study. The influence of temperature, fat content, and aw on the Weibull model parameters was evaluated using nonlinear least squares regression, and a revised secondary model was developed based on parameter significance. Peanut butter, chia seed powder, toasted oat cereal, and animal crackers within the aw range of the model were used to validate the modified model within its temperature range. Fat content influenced survival in samples held at temperatures ≥50°C, whereas aw influenced survival at 37 and 70°C. The model predictions demonstrated improved % bias and % discrepancy compared with the previous model. Weibull model predictions were accurate and fail-safe in 38 and 58%, respectively, of the food and environmental conditions under study. Predictions were less reliable for peanut butter held at 80°C. This study provides data and a model that can aid in the development of risk mitigation strategies for low-aw foods containing fat. HIGHLIGHTS

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