U nified M A terials R esponse C O de (UMARCO) update & Thermal Response of Dendrites
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Transcript of U nified M A terials R esponse C O de (UMARCO) update & Thermal Response of Dendrites
UUnified MAMAterials RResponse CCOde (UMARCO) update& Thermal Response of DendritesQiyang Hu (UCLA)
Aaron Oyama (UCLA)Shahram Sharafat (UCLA)Jake Blanchard (Wisc) Nasr Ghoniem (UCLA)
19th HAPL MeetingUniversity of Wisconsin, Madison
Oct. 22-23, 2008
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Unified Simulation Unified Model would
Avoid inconsistencies Simplify modeling of wide variety of situations
New tool will model: Heating profile (x-rays and ions) Transient temperatures, stresses, strains Fracture mechanics Ion deposition profile, diffusion, and clustering
UMACROHAPL pellet
spectrum Material: SRIM Material: Mech Prop.
Ion Implant. Profile Vol. Heating Rate
Temperature CoupledCoupled
Transient stress strain field Module
Constitutive Lawelastic, plastic
Fracture Module ImprovedImproved
Stress Waves CoupledCoupled
Diffusion Module:Ion, Helium,
Bubbles, Carbon
Fortran’90 C++
1
2
4
Modeling of Surface Cracking
0
2
4
6
8
10
12
0 25 50 75 100 125 150
ChamberIon Beam
Sre
ss In
tens
ity (M
Pa-
m1/
2 )
Crack depth (m)
•Stress intensity factor decreases as cracks grow further from surface
•Crack growth will arrest
•Crack arrest will be more shallow for short pulse experiments (like RHEPP)
UW
Crack Arrays What if we have
an array of cracks?
This will tend to relieve the stresses
TOFE 20085
h
Results for Crack Arrays
1E-4 1E-3 0.01
0
1000
2000
3000
4000
5000
6000
7000
h/b=8 (new)h/b=12 (new)
h/b=108 (nied)
h/b=2 (nied)
h/b=4 (nied)
h/b=2 (new)
h/b=4 (new)
h/b=20 (new)Single Crack
K
I (MP
a x m
1/2 )
Time (sec)
by Different G(s)
KIC 7 MPa·m1/2
for recrystal W(A.V. Babak, 1981)
Reproducing HEROS User defined f(t,y)
f(t,y) = react + diff + drift reaction + drift term:
13(18) variables: Alhajji-Sharafat-Ghoniem 13+2 (temperature & carbon)
Test Results: Single shot case:
UNC, UWM, ITER: OK! Diffusion behavior is more obvious.
Multiple shot case: 2 shots of “const temperature” HAPL case: OK!
Non-const temperature: Linear from 400 C to 2000 C: OK!
Solving thermal stress wave problem Thermal wave stress governing equations:
System specifications:
Stress-free& adiabatic
10 m 3mm
20 ~ 200 Grids Stress-free& temperature const.
Q’’’
Numerical considerations 3 ODE equations:
A proper cvode option tested by bubble diffusion: Solver: Krylov solver SPGMR Precondition: CVBANDPRE module Activate stability limit detection
Spatial finite-difference scheme:
Heating Rate (Q’’’) in HAPL
Depth (m)Vo
lHea
tRat
eQ
'''(J
/m3 /s
ec)
2 4 6 8 10 120
2E+15
4E+15
6E+15
8E+15
1E+16
Time = 0.8224E-06 sec
• Ion implantation: ~0.1sec per step
The most severe case:
Quasi-static Decomposition Stress wave propagation time:
Thermal diffusion time scale:
Decomposition
Fast (high frequency) Slow (quasi-static)
Low Frequency Thermo-elastic Wave
High-Frequency Thermo-elastic Waves forSelected Heating Step (duration 0.11sec)
Stress Magnitudes from Elastic Waves
Time (sec)
Stre
ssM
agni
tude
(GPa
)
0 3E-08 6E-08 9E-08 1.2E-07 1.5E-070
0.05
0.1
0.15
0.2
0.25
Max StressStd Stress
Roughening or Dendrite
Roughening aims at minimizing energies (surface strain & stress) Ultimately results in NANO- or MICRO-CASTELLATION
Why not start with a micro-castellated surface, similar to the UW-Madison Coral structure
Or simply start with Dendrites: No surface stress or strains on dendrite surface
Tungsten Dendrite Structures
Dendrite Thermal Response to HAPL ThreatHAPL Threat for 10.5 m radius chamber:
Source Arrival Time (ns)
Pulse Width (ns)
Avg Heating Rate (W/m3)
Photons 0 0.5 4.27E+18Neutrons (tungsten) 280 35 4.23E+14Burn ions 200 800 9.04E+15Debris ions 800 3263 1.52E+16
Tip Radius: 1.5 m
Dendrite Thermal Response to HAPL Threat
95.71 m
D
D=0
D=95.71
Max Tip Temperature = 3836 °Cat 4063 ns (end of shot)
Max Base Temperature = 1308 °C at 120 μs after shot
Effect of Tip Radius on Temperature Transient Profile
95.71 m
r=1 m
r=3 m
r=5 m
Summary & Conclusions UMARCO (C++) framework completed Fatigue of Interface Between W/Fe is a Concern. Tungsten dendrite structure can be fabricated
with various aspect ratios and tip radii A tip radius of 5 mm will prevent tip melting Mechanical modeling to be done, however
stress and strains should remain fairly low because of dendrite geometry
Sputtering modeling including re-deposition shows minimal overall loss of material (see Tim Knowles’s poster).
Extra Slides
Surface temperature comparison
UMARCO
Sputtering & Redeposition For Dense Needle Configuration Carbon velvet carpets have been used in
space applications for ion thruster wall, with encouraging sputtering results after years of operation
Sputtering plus Redeposition modeling shows little loss of geometry (see next viewgraph).
From Tim Knowles Poster
Using CVODESUite of Nonlinear and DIfferential/Algebraic equation Solvers
by Alan C. Hindmarsh and Radu Serban
Direct:
Krylov:
Scaled Preconditioned
Generalized Minimal Residual method
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Crack Depth Measurements in RHEPP