Peter Titus – Fracture Mechanics Analysis

• Based on code developed for ITER TF case analysis by Jun Feng, used 2 to 3.5 mm initial flaw size
• Peter and Jun will run different Y factors to better simulate Len's stress situation.
• Dick will send Peter and Jun 316 weld data to run.
• Ran code for NCSX case, using constants from NIST for annealed 316 at 77K (provided by Jun) and ITER cast case sections at 7K.  (Dick Reid: Data differences not related to different temperatures, but ITER data may not be conservative)  ITER indicated it was a grain size effect that made the casting data better. 
• Two stress levels, life set to end when crack propagated through 0.75 inches
• Jun’s program calculates fast fracture, and simulation ends when it goes 0.75 inches or when fast fracture occurs
• Ran 262 and 131 MPa
• Need factor of 4 on life, or 520,000 cycles
• Model assumes plate width is infinite, crack depth to width = 0.3 initially, different crack depths assumed.
• What is failure criteria?  electrical failure of winding, deflection beyond allowable for good magnetic surfaces
• What did ITER use as flaw size? < 1mm
• X-rays will not detect cracks, add ultrasonic testing in critical areas

Action: Phil sets up meeting with inspection guys from Metaltek and Waukesha to discuss what techniques are needed to find cracks

 

Cable tests – underway again, no news to report yet

 

Beam tests: Torsion, bending, shear testing

• Jim C. to make new straight beams
• W7-AS used full cross section , did not resolve into copper, epoxy, etc.
• Beam fixtures need to be modified at ORNL to provide torsion

 

Action: Len to use his model to figure out combination of bending/torsion in worst loaded conditions – will make model of beam with tee and smeared winding pack, at some point change to detailed winding pack

 

Action: Len come up with another set of properties that we need and do not have yet

(shear modulus in conductor and insulation, interlaminar shear strength turn-to-turn, etc.)

 

Action: Come up with new set of test specimens to establish needed properties