Ogden Air Logistics Center Applications of advanced fracture mechanics utilizing StressCheck and AFGROW Joshua Hodges T-38 Structural Integrity and Analysis Group 11-11-22_GH_035 BE AMERICA’S BEST
What happens when you intertwine AFGROW ‘s Plug-in capabilities with StressCheck? O G D E N A I R L O G I S T I C S C E N T E R BAMF Broad Application for Modeling Failure BE AMERICA’S BEST
What does BAMF do for you? O G D E N A I R L O G I S T I C S C E N T E R =K/ σ Far field stress from StressCheck Extract Stress Intensities BE AMERICA’S BEST
What does BAMF do for you? O G D E N A I R L O G I S T I C S C E N T E R da/dN (inch/cycle) Δ K= Δσ New Crack Lengths Where Δσ is the AFGROW spectrum stress 1 10 100 Δ K (ksi √in ) Extract Stress Intensities BE AMERICA’S BEST
Flavors of BAMF O G D E N A I R L O G I S T I C S C E N T E R Single Elliptical Crack (a/c variable-elliptical thru crack) BAMF Single Elliptical Crack (a/c constant-strait thru crack) BAMF Double Elliptical Crack (a/c variable-elliptical thru crack) BAMF Double Elliptical Crack (a/c constant-strait thru crack) BAMF Multi-Elliptical Crack (in progress; Identified a need for future BAMF AFGROW capability) Multi-Point Crack Growth (utilizes StressCheck splines to create BAMF unique crack fronts)
Features of BAMF O G D E N A I R L O G I S T I C S C E N T E R Benefits of BAMF Elliptical crack shape • Removes conservatisms • Continuing damage models • Multi-site damage • Flat plate assumptions • Reduced engineering judgment • Reduced engineering time • Reduced risk 1.70 in BE AMERICA’S BEST
Features of BAMF O G D E N A I R L O G I S T I C S C E N T E R Benefits of BAMF • Removes conservatisms Elliptical crack shape • Continuing damage models • Multi-site damage • Flat plate assumptions • Reduced engineering judgment • Reduced engineering time • Reduced risk Benefits of Mulit-point BAMF • Reduction of stress intensities at the bore (compared to elliptical crack assumption) • More realistic crack shapes (compared to elliptical crack assumption) • Increased load carrying capability (compared to elliptical crack assumption) • P-shape and other unique crack shapes BE AMERICA’S BEST
Building of Code O G D E N A I R L O G I S T I C S C E N T E R Code built in VB2008 Express using AFGROWBetaPlugin BAMF (ref Brent Lancaster, AFGROW users workshop; 2011) Development of first plug-in took approximately 6 BAMF months (Learning curve for AFGROW/SC commands) Code developed to grow and analyze a crack in any BAMF geometry in practice while minimizing user inputs. BE AMERICA’S BEST
BAMF’n Cracks O G D E N A I R L O G I S T I C S C E N T E R Test data obtained by SwRI: Cronenberger, J. (2011). Mathematical Modeling and Validation of Stress- Intensity Factor Solution for Cracks Emanating from Countersunk Holes, Masters Thesis, University of Texas – San Antonio, San Antonio, TX, USA BE AMERICA’S BEST
BAMF’n Cracks in Countersinks O G D E N A I R L O G I S T I C S C E N T E R Test data obtained by SwRI: Cronenberger, J. (2011). Mathematical Modeling and Validation of Stress-Intensity Factor Solution for Cracks Emanating from Countersunk Holes, Masters Thesis, University of Texas – San Antonio, San Antonio, TX, USA BE AMERICA’S BEST
BAMF’n Cracks in Countersinks O G D E N A I R L O G I S T I C S C E N T E R BE AMERICA’S BEST
BAMF’n 2 Cracks O G D E N A I R L O G I S T I C S C E N T E R BE AMERICA’S BEST
BAMF’n Multi-Point O G D E N A I R L O G I S T I C S C E N T E R • Points may need to be • Initially the 1 st point created that lay outside will grow only in the the body. This will ensure y-direction until that that the crack can grow in point is no longer on complex geometries. the face of the part • Each stress intensity is • The cracks will grow calculated from a 3 point a value of da, average of points on the perpendicular to the extracted stress intensity line created by its curve. adjacent points. • The stress intensity at an • If a point is outside end point is calculated the body it will grow from 2 points inboard of based on the stress the extracted stress intensity just intensities beneath its closest surface. BE AMERICA’S BEST
BAMF’n Multi-Point O G D E N A I R L O G I S T I C S C E N T E R • Once the 1 st point leaves the surface it will then grow perpendicular to the line created between itself and its adjacent point. • Large crack growth increments will harm crack growth shape. • The larger the crack grows the less accurate its predicted shape becomes. BE AMERICA’S BEST
BAMF’n Multi-Point O G D E N A I R L O G I S T I C S C E N T E R BE AMERICA’S BEST
BAMF’n Multi-Point O G D E N A I R L O G I S T I C S C E N T E R BE AMERICA’S BEST
Discussion of things to be worked on O G D E N A I R L O G I S T I C S C E N T E R AFGROW ISSUES Dealing with small crack lengths <0.05 in • AFGROW call to “Calculate Beta” subroutine Multiple point crack growth rate BAMF ISSUES Through thickness failure Failure/Fracture criteria (No current failure criteria) STRESSCHECK ISSUES Mesh refinement tools (local curve refinement) Multiple points going out of the surface • Possible proposed method-redistributing points as the crack grows. BE AMERICA’S BEST
Questions/Comments/Concerns O G D E N A I R L O G I S T I C S C E N T E R BE AMERICA’S BEST
Building a BAMF Model in StressCheck O G D E N A I R L O G I S T I C S C E N T E R Sets, Sets, Sets CRACKFACE; CRACKFRONT; AUTOMESH; NUCLEATION; Boundary Conditions Parameters Thickness-Thickness of crack at transition Stress- Far field stress of the model with given BC’s Multi-point • Number of Points-Number of points on crack face • Point Locations (Px0, Py0, Px1, Py1…) View and plot profiles saved as “Stress” Saved with No Mesh BE AMERICA’S BEST
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