Mesoscale Material Strength Characterization for Use in Fracture Modeling

2018 ◽  
Author(s):  
Katherine Acton ◽  
Bahador Bahmani ◽  
Reza Abedi
Keyword(s):  
Material Property ◽  
Effective Properties ◽  
Probability Distributions ◽  
Voronoi Tessellation ◽  
Strength Properties ◽  
Small Scale ◽  
Material Strength ◽  
Fracture Modeling ◽  
Strength Characterization ◽  
Proportional Limit Stress

To accurately simulate fracture, it is necessary to account for small-scale randomness in the properties of a material. Apparent properties of Statistical Volume Elements (SVE), can be characterized below the scale of a Representative Volume Element (RVE). Apparent properties cannot be defined uniquely for an SVE, in the manner that unique effective properties can be defined for an RVE. Both constitutive behavior and material strength properties in SVE must be statistically characterized. The geometrical partitioning method can be critically important in affecting the probability distributions of mesoscale material property parameters. Here, a Voronoi tessellation based partitioning scheme is applied to generate SVE. Resulting material property distributions are compared with those from SVE generated by square partitioning. The proportional limit stress of the SVE is used to approximate SVE strength. Superposition of elastic results is used to obtain failure strength distributions from boundary conditions at variable angles of loading.

Effect of Volume Element Geometry on Convergence to a Representative Volume

2019 ◽  
Vol 5 (3) ◽  
Author(s):  
Katherine Acton ◽  
Connor Sherod ◽  
Bahador Bahmani ◽  
Reza Abedi
Keyword(s):  
Material Property ◽  
Effective Properties ◽  
Probability Distributions ◽  
Voronoi Tessellation ◽  
Strength Properties ◽  
Volume Element ◽  
Small Scale ◽  
Material Strength ◽  
Representative Volume ◽  
Proportional Limit Stress

To accurately simulate fracture, it is necessary to account for small-scale randomness in the properties of a material. Apparent properties of statistical volume element (SVE) can be characterized below the scale of a representative volume element (RVE). Apparent properties cannot be defined uniquely for an SVE, in the manner that unique effective properties can be defined for an RVE. Both constitutive behavior and material strength properties in SVE must be statistically characterized. The geometrical partitioning method can be critically important in affecting the probability distributions of mesoscale material property parameters. Here, a Voronoi tessellation-based partitioning scheme is applied to generate SVE. Resulting material property distributions are compared with those from SVE generated by square partitioning. The proportional limit stress of the SVE is used to approximate SVE strength. Superposition of elastic results is used to obtain failure strength distributions from boundary conditions at variable angles of loading.

Applying Information Economics and Imprecise Probabilities to Data Collection in Design

2005 ◽  
Author(s):  
Jason Matthew Aughenbaugh ◽  
Jay Ling ◽  
Christian J. J. Paredis
Keyword(s):  
Probability Distributions ◽  
Information Economics ◽  
Cost Benefit ◽  
Information Collection ◽  
Material Strength ◽  
Imprecise Probabilities ◽  
Current State ◽  
Trade Offs ◽  
Strength Characterization ◽  
Collection Phase

One important aspect of the engineering design process is the sequence of design decisions, each consisting of a formulation phase and a solution phase. As part of the decision formulation, engineers must decide what information to use to support the decision. Since information comes at a cost, a cost-benefit trade-off must be made. Previous work has considered these trade-offs in cases in which all relevant probability distributions were precisely known. However, engineers frequently must estimate these distributions by gathering sample data during the information collection phase of the decision process. In this paper, we introduce principles of information economics to guide decisions on information collection. We present a method that enables designers to bound the value of information in the case of unknown distributions by using imprecise probabilities to characterize the current state of information. We illustrate this method with an example material strength characterization for a pressure vessel design problem, in which we explore the basic performance, subtleties, and limitations of the method.

scholarly journals Investigation on Alamparai Fort by Utilization of Organic Materials for Improvement of Stability of Heritage Structure

2021 ◽  
Author(s):  
Kotteeswaran Santhanam ◽  
Ravi Ramadoss
Keyword(s):  
Seismic Analysis ◽  
Strength Properties ◽  
Small Scale ◽  
Strength Analysis ◽  
Material Strength ◽  
Existing Structures ◽  
Seismic Modelling ◽  
Punch Test ◽  
Mortar Strength ◽  
The Stability

Abstract Heritage structures are valuable monuments to describe the culture and traditions of the country. These heritage structures get deformed in today's scenario by natural or artificial disasters. Hence, to preserve these heritage structures, restoration was introduced to restore the ancient building with new binding agents. Rehabilitation can take place only by analysing the properties of existing structures. Based on the existing structure properties, the alternative binding agent selected; can regain the same strength and shape of the heritage structures. Based on these, the restoration of Alamparai fort was performed by analysing the fort materials using mortar strength analysis by core-drilling, double punch test, and small-scale masonry test. The arch properties are also analysed by performing seismic analysis based on the mortar strength properties. The stability analysis of the organic and existing materials shows that Gur and haritaki is the best agent for restoring the fort. Hence, the mortar strength and seismic analysis of these materials performed using diagonal shear test and seismic modelling of the fort. The proposed material strength tests results indicate that the Gur and Haritaki is the best agent to restore the fort. The fort was restored with these materials; it survived in Nivar cyclone crossed on 26th November 2020.

Mesoscale Models Characterizing Material Property Fields Used As a Basis for Predicting Fracture Patterns in Quasi-Brittle Materials

2017 ◽  
Author(s):  
Katherine A. Acton ◽  
Sarah C. Baxter ◽  
Bahador Bahmani ◽  
Philip L. Clarke ◽  
Reza Abedi
Keyword(s):  
Crack Propagation ◽  
Material Property ◽  
Mesoscale Model ◽  
Voronoi Tessellation ◽  
Brittle Materials ◽  
Material Behavior ◽  
Small Scale ◽  
Element Analysis ◽  
Stress Criterion ◽  
Fracture Patterns

To accurately predict fracture patterns in quasi-brittle materials, it is necessary to accurately characterize heterogeneity in the properties of a material microstructure. This heterogeneity influences crack propagation at weaker points. Also, inherent randomness in localized material properties creates variability in crack propagation in a population of nominally identical material samples. In order to account for heterogeneity in the strength properties of a material at a small scale (or “microscale”), a mesoscale model is developed at an intermediate scale, smaller than the size of the overall structure. A central challenge of characterizing material behavior at a scale below the representative volume element (RVE), is that the stress/strain relationship is dependent upon boundary conditions imposed. To mitigate error associated with boundary condition effects, statistical volume elements (SVE) are characterized using a Voronoi tessellation based partitioning method. A moving window approach is used in which partitioned Voronoi SVE are analysed using finite element analysis (FEA) to determine a limiting stress criterion for each window. Results are obtained for hydrostatic, pure and simple shear uniform strain conditions. A method is developed to use superposition of results obtained to approximate SVE behavior under other loading conditions. These results are used to determine a set of strength parameters for mesoscale material property fields. These random fields are then used as a basis for input in to a fracture model to predict fracture patterns in quasi-brittle materials.

Generative Textiles for Non-Rotary Power Production From Wind

2012 ◽  
Author(s):  
Scott Lux ◽  
Christopher Foster ◽  
Meredith Sellers ◽  
Andrew Friedl ◽  
Carl Feickert ◽  
...  
Keyword(s):  
Probability Distributions ◽  
Human Locomotion ◽  
Small Scale ◽  
Engineering Research ◽  
Design And Optimization ◽  
Wind Energy Generation ◽  
Harvesting Systems ◽  
Practical Engineering ◽  
Wind Simulation ◽  
Operational Envelope

The U.S. Army Engineer Research and Development Center, Construction Engineering Research Laboratory (ERDC-CERL) is developing a new class of flexible, generative textile as a novel means of sustainable wind energy generation. Flexible, generative carbon nanotube (CNT)-based textiles may have excellent potential for electrical capacitive storage and reuse in conjunction with small-scale energy-harvesting systems, both from wind for fixed applications and from human locomotion. This paper describes the design and optimization of a three-layer generative textile composed of discrete layers for generation, distribution, and storage. Initial results suggest that improvement in the generation layer will provide the highest increase in overall performance. The output of the electromagnetic tests shows a power density of 0.17 mW/cm3. However, the efficiency can be significantly improved through increasing the voltage output of the generation layer from 20 mV to around 1V. In an analysis of the operational envelope, wind data collected locally at ERDC-CERL and at other sites around the world reveal close similarity in the probability distributions, which could allow for a practical engineering approach capable of harvesting the steady “ram” component in addition to a variable energy component of the wind. To further study the textile-wind interactions, a wind simulation environment is being developed and has been able to obtain reproducible wind speed data thus far.

Non-Gaussian probability distributions of solar wind fluctuations

1994 ◽  
Vol 12 (12) ◽  
pp. 1127-1138 ◽  
Author(s):  
E. Marsch ◽  
C. Y. Tu
Keyword(s):  
Solar Wind ◽  
Probability Distributions ◽  
Time Lag ◽  
Small Scale ◽  
Time Lags ◽  
Mhd Turbulence ◽  
Theoretical Concepts ◽  
Fluid Turbulence ◽  
Long Time ◽  
Non Gaussian

Abstract. The probability distributions of field differences ∆x(τ)=x(t+τ)-x(t), where the variable x(t) may denote any solar wind scalar field or vector field component at time t, have been calculated from time series of Helios data obtained in 1976 at heliocentric distances near 0.3 AU. It is found that for comparatively long time lag τ, ranging from a few hours to 1 day, the differences are normally distributed according to a Gaussian. For shorter time lags, of less than ten minutes, significant changes in shape are observed. The distributions are often spikier and narrower than the equivalent Gaussian distribution with the same standard deviation, and they are enhanced for large, reduced for intermediate and enhanced for very small values of ∆x. This result is in accordance with fluid observations and numerical simulations. Hence statistical properties are dominated at small scale τ by large fluctuation amplitudes that are sparsely distributed, which is direct evidence for spatial intermittency of the fluctuations. This is in agreement with results from earlier analyses of the structure functions of ∆x. The non-Gaussian features are differently developed for the various types of fluctuations. The relevance of these observations to the interpretation and understanding of the nature of solar wind magnetohydrodynamic (MHD) turbulence is pointed out, and contact is made with existing theoretical concepts of intermittency in fluid turbulence.

scholarly journals Ansys code applied to investigate the dynamics of composite sandwich beams

2021 ◽  
Vol 25 (1) ◽  
pp. 62-71
Author(s):  
Agnieszka Chudzik
Keyword(s):  
Sandwich Beam ◽  
Strength Properties ◽  
Effect Of Temperature ◽  
Material Strength ◽  
Beam Model ◽  
The Finite Element Method ◽  
Ansys Software ◽  
Composite Sandwich ◽  
Viscoelastic Core ◽  
Influence Of Temperature On

Abstract A numerical analysis of the effect of temperature on the dynamics of the sandwich beam model with a viscoelastic core is presented. The beam under analysis was described with a standard rheological model. This solution allows one to study the effect of temperature on material strength properties. Calculations were performed with the Finite Element Method in the ANSYS software. The analysis of the results of the numerical calculations showed a significant influence of temperature on the strength properties of the model under test. The analysis confirmed damping properties of viscoelastic materials.

Experience With Large Heavy-Duty Gas Turbine Rotors

1981 ◽  
Author(s):  
O. R. Schmoch ◽  
B. Deblon
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Turbine Rotor ◽  
Strength Properties ◽  
Operating Conditions ◽  
Material Strength ◽  
Heavy Duty ◽  
Turbine Rotors ◽  
Heavy Duty Gas Turbine ◽  
Response To Temperature

The peripheral speeds of the rotors of large heavy-duty gas turbines have reached levels which place extremely high demands on material strength properties. The particular requirements of gas turbine rotors, as a result of the cycle, operating conditions and the ensuing overall concepts, have led different gas turbine manufacturers to produce special structural designs to resolve these problems. In this connection, a report is given here on a gas turbine rotor consisting of separate discs which are held together by a center bolt and mutually centered by radial serrations in a manner permitting expansion and contraction in response to temperature changges. In particular, the experience gained in the manufacture, operation and servicing are discussed.

STUDENTS’ INFORMAL HYPOTHESIS TESTING IN A PROBABILITY CONTEXT WITH CONCRETE RANDOM GENERATORS

2020 ◽  
Vol 19 (3) ◽  
Author(s):  
PER NILSSON
Keyword(s):  
Hypothesis Testing ◽  
Teaching And Learning ◽  
Formal Education ◽  
Statistics Education ◽  
Probability Distributions ◽  
Teaching Experiment ◽  
Small Scale ◽  
Uniform Probability ◽  
Data Production

This study examines informal hypothesis testing in the context of drawing inferences of underlying probability distributions. Through a small-scale teaching experiment of three lessons, the study explores how fifth-grade students distinguish a non-uniform probability distribution from uniform probability distributions in a data-rich learning environment, and what role processes of data production play in their investigations. The study outlines aspects of students’ informal understanding of hypothesis testing. It shows how students with no formal education can follow the logic that a small difference in samples can be the effect of randomness, while a large difference implies a real difference in the underlying process. The students distinguish the mode and the size of differences in frequencies as signals in data and used these signals to give data-based reasons in processes of informal hypothesis testing. The study also highlights the role of data production and points to a need for further research on the role of data production in an informal approach to the teaching and learning of statistical inference. First published December 2020 at Statistics Education Research Journal: Archives

Full-Scale Reeling Tests of HFI Welded Line Pipe for Offshore Reel-Laying Installation

2014 ◽  
Author(s):  
Karl Christoph Meiwes ◽  
Susanne Höhler ◽  
Marion Erdelen-Peppler ◽  
Holger Brauer
Keyword(s):  
Mechanical Testing ◽  
Mechanical Test ◽  
Strength Properties ◽  
Full Scale ◽  
Bending Test ◽  
Small Scale ◽  
Pipe Material ◽  
Deformation Capacity ◽  
Line Pipe ◽  
Tension And Compression

During reel-laying repeated plastic strains are introduced into a pipeline which may affect strength properties and deformation capacity of the line pipe material. Conventionally the effect on the material is simulated by small-scale reeling simulation tests. For these, coupons are extracted from pipes that are loaded in tension and compression and thermally aged, if required. Afterwards, specimens for mechanical testing are machined from these coupons and tested according to the corresponding standards. Today customers often demand additional full-scale reeling simulation tests to assure that the structural pipe behavior meets the strain demands as well. Realistic deformations have to be introduced into a full-size pipe, followed by aging, sampling and mechanical testing comparable to small-scale reeling. In this report the fitness for use of a four-point-bending test rig for full-scale reeling simulation tests is demonstrated. Two high-frequency-induction (HFI) welded pipes of grade X65M (OD = 323.9 mm, WT = 15.9 mm) from Salzgitter Mannesmann Line Pipe GmbH (MLP) are bent with alternate loading. To investigate the influences of thermal aging from polymer-coating process one test pipe had been heat treated beforehand, in the same manner as if being PE-coated. After the tests mechanical test samples were machined out of the plastically strained pipes. A comparison of results from mechanical testing of material exposed to small- and full-scale reeling simulation is given. The results allow an evaluation of the pipe behavior as regards reeling ability and plastic deformation capacity.

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