Presentation 5 Phase B - Fatigue & Fracture Studies S. J. Jung 1

Objective To improve the pavement design, a simple and dependable testing and validating procedure is needed to enhance the material design and prediction of pavement life. 2

Method comparison Number of loading is common variables Work with Cyclic loading Estimate fatigue information Work with energy concept 3

Schematic diagram of pseudo-strain energy density functions(H.J. Lee 2002) 4

Dynamic function Monotonic function 5

Energy Comparison Dynamic Approach Failure Energy (lb.in) 0.21 for actual 0.38 for duplication 0.58 for under curve Static Approach Notch Failure Energy (in) (lb.in) *** Difference caused the following reasons; sample, peak load, deformation, loading condition (Hz, temperature, etc) **Calculation 6

Upgraded MTS system Testing the system and study the testing parameter with MTS 7

Modifying cooling unit 8

Half circle Specimen About 436 specimen has been prepared and about 50% of specimen were cut the notch. 9

Potential study variables Temperature (°C)Strain rate (10 -6 units/s) Frequency (Hz) MonotonicCyclic (Daniel 2002)5, 205, 12, 2010, 30, 500, 15001, 10 (R. Lundstrom 2003)0,10,20100, 200, 400, (T.O. Medani 2000)5, 15, 20, 25, 30 for n10-50 (H. J. Lee 2002)255 Testing plan: plan to test 36 samples for each mix type to understand function of each variable 10

Numerical modeling: Particle Flow Code (PFC) is based on the Distinct Element Method (DEM), The model study of PFC2D (discrete element program) is continuously investigated with proposed test parameters to obtain acceptable outcome which will be compared with specimen test results. As shown below, PFC 2D model needs to be improved to obtain an acceptable outcome. 11

DEM simulation study parameter Mass properties Normal and shear Stiffness Strength Density Young’s modulus Friction Force Cycle 12