Supported by

NSTX Centerstack Upgrade Project Meeting

P. Titus October 5 2011

Rib and Tab Weld Fracture Mechanics

Gap Elements (52 Point to Point)

Tab Models are reflected - Both sides mirror images of the other - Welded only on top and Bottom with gaps/contact elements between the tab and rib

30 degree Cyclic Sym – OOP Loads from HanMultiplied by 12/10

Rib Tab Weld Evaluation forWorst Case Power Supply

Loads

Actual Weld Detail

Assume bevel backed by a fillet is like a full penetration. Tab weld Stresses all appear less than 96 MPa

Tensile Side73MPa away from the weldOr 10.5 ksi

Compressive Side

Crack is Closed on the Tensile Side

An Experimental Investigation of Fatigue Crack Growth of Stainless Steel 304LS. Kalnaus,F.Fan, Y Jiang, A.K. VasudevanUniversity of Nevada and Office of Naval Research , International Journal of Fatigue, Volume 31, Issue 5, May 2009 [14]

[15]

The root of the weld isassumed to be a crack geometry and the SIF is computed in ANSYS.

**** CALCULATE MIXED-MODE STRESS INTENSITY FACTORS ****

ASSUME PLANE STRESS CONDITIONS

ASSUME A FULL-CRACK MODEL (USE 5 NODES)

EXTRAPOLATION PATH IS DEFINED BY NODES: 10661 10649 10663 10681 10693 WITH NODE 10661 AS THE CRACK-TIP NODE

USE MATERIAL PROPERTIES FOR MATERIAL NUMBER 1 EX = 0.29000E+08 NUXY = 0.30000 AT TEMP = 0.0000

**** KI = 12979. , KII = 5075.6 , KIII = 1860.8 ****

.088 in Crack DepthNo Lateral Fixity at top of Tab

.088 in Crack Depth Lateral Fixity at top of Tab Added

**** CALCULATE MIXED-MODE STRESS INTENSITY FACTORS ****

ASSUME PLANE STRESS CONDITIONS

ASSUME A FULL-CRACK MODEL (USE 5 NODES)

EXTRAPOLATION PATH IS DEFINED BY NODES: 10661 10681 10693 10649 10663 WITH NODE 10661 AS THE CRACK-TIP NODE

USE MATERIAL PROPERTIES FOR MATERIAL NUMBER 1 EX = 0.29000E+08 NUXY = 0.30000 AT TEMP = 0.0000

**** KI = 7305.0 , KII = 4191.5 , KIII = 1589.9 ****

**** CALCULATE MIXED-MODE STRESS INTENSITY FACTORS ****

ASSUME PLANE STRESS CONDITIONS

ASSUME A FULL-CRACK MODEL (USE 5 NODES)

EXTRAPOLATION PATH IS DEFINED BY NODES: 10661 10681 10693 10649 10663 WITH NODE 10661 AS THE CRACK-TIP NODE

USE MATERIAL PROPERTIES FOR MATERIAL NUMBER 1 EX = 0.29000E+08 NUXY = 0.30000 AT TEMP = 0.0000

**** KI = 7936.9 , KII = 4341.6 , KIII = 1687.4 ****

.088 in Crack Depth

.125 in Crack Depth Lateral Fixity at top of Tab Added

! Simple da/dn integral for 304 Stainless Steellet t=.5*.707/39.37let ainit=.125/39.37let m=2.95let c=5.43e-12let fractTough=100let deltak= 7305*6895/1e6/39.37^.5let a=ainitlet abreak=ainit+tlet counter = 0!for i= 1 to 10000do!deltak is linear in crack lengthlet delk=deltak/ainit*a!assume the delta k scales with the orig thick/remaining thicknesslet delk=delk*(t+ainit)/(t+ainit-a)let i=i+1let counter=counter+1let dadn=c*delK^mlet a=a+dadnif counter = 100 thenprint i;",";delk;","; alet counter = 0end ifif a>abreak or delk>fractTough then exit do!next iloopprint "Cracked Through"end

Crack Size in meters vs. Cycles

Delta K in Mpa root m vs. Cycles