Integrated Fracture Modeling and Integrated Fracture Modeling and Testing ApproachTesting Approach

University of Illinois Research UpdateUniversity of Illinois Research Update

E1 E5

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(c) Field Data and Performance

(d) Lab Testing(a) Fracture Behavior

(b) Bulk Material Response

Computer Simulation

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Bill Buttlar, Glaucio Paulino, Eshan Dave, and Sofie LeonNovember 18, 2009 – Mn/ROAD Maplewood Lab

Review: Task-4Review: Task-4

Develop and validate mixture specification for low-temperature cracking:– Level-I: Mixture fracture test– Level-II: Mixture tests + Modeling

Fracture + Creep + CTE

Task-4:– An executable code that can either be run

standalone or in conjunction with the MEPDG– User-friendly interfaces for data input and

presentation of results– User’s guide with numerical examples that can be

used to verify that the program is working properly

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Level-I, Example (Phase-I)Level-I, Example (Phase-I)

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Mn/ROAD Section-35

TCModel vs. New TCModelTCModel vs. New TCModel

Stress Intensity Factor Model

Fracture Model: Paris Law

Crack Amount Model– Amount of cracking is a function of the

probability that the crack depth is equal to or greater the thickness of the surface layer

Finite Element Based Thermal Cracking Prediction Model with Cohesive Zone Modeling

TCModel New TCModel

Stress Intensity FactorFar-field stress at depth of crack

Current crack length

)99.145.0( 56.00CK

Change in crack depth

Change in stress intensity factorFracture parameters

nKAC )(

Bilinear cohesive zone model

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New TCModel FeaturesNew TCModel Features

Multiple HMA lifts

Viscoelastic bulk material behavior

– IDT creep properties

Cohesive zone fracture model

– Recommended model from the phase-I results

– Uses fracture test results

Finite element analysis engine

– Includes mesh generator

– Non-linear solver

Similar climatic model as MEPDG

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New TCModel StatusNew TCModel Status Completed Tasks

– Finite element analysis code (testing is underway)

– Mesh generator

Tasks underway

– Viscoelastic analysis code (formulations are developed, implementation underway)

– Temperature boundary condition selection

Future Tasks

– Testing of code with all components

– Verification and calibration

– Integration with User Interface (Visual LTC*)

*Developed under NexTrans supplementary study by Sofie Leon

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Visual LTC Analysis ToolVisual LTC Analysis ToolDeveloped on NexTrans Supplementary Developed on NexTrans Supplementary

ProjectProject User-friendly graphical user interface (GUI) to

capture low temperature cracking characteristics of asphalt concrete

Allows for quick yet sophisticated analysis for practical applications

Currently, it is utilizing TCModel (MEPDG) New TCModel will be linked as soon as

implementation and testing is complete

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Visual LTC User TypesVisual LTC User Types

– Practitioners

– Access to all existing mixes

– Default mix properties can be viewed but not changed

– Researchers/Developers

– Access to all existing mixes

– Default mix properties can be viewed and changed

– Modify existing mixes and add new mixes

Standard User Advanced User

Similar to existing MEPDG layout

User can easily switch between user types

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Visual LTCVisual LTC

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Visual LTC ResultsVisual LTC Results

Crack depth with time Amount of cracking with time

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Questions?Questions?

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A

B

t

A

B

Cohesive Zone