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CASE STUDY – Combined Loading

CASE STUDY – Combined Loading. Drill bit isolators for underground mining – all metal components and elastomer must be safe! Design requirement: 8,000 lb thrust load and 300 lb-ft (3,600 lb-in) torque – these are basically the cutting forces.

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CASE STUDY – Combined Loading

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  1. CASE STUDY – Combined Loading • Drill bit isolators for underground mining – all metal components and elastomer must be safe! • Design requirement: 8,000 lb thrust load and 300 lb-ft (3,600 lb-in) torque – these are basically the cutting forces. • Detailed FE analysis but ALWAYS verify with hand calculations!!

  2. Bit Isolator Drill Depth up to 48” Chuck Isolator 2010 SME Annual Meeting & Exhibit Phoenix, Arizona

  3. 35 mm (1 3/8 in) Isolator Load Requirements: Drill Bit Drill Bit Isolator ( Thrust Load = 8,000 to 10,000 lb Bending Load= 125 lbs)= K*d Drill Rod Torsion Load= 300 lb-ft Chuck Isolator HOT SPOT! 2010 SME Annual Meeting & Exhibit Phoenix, Arizona

  4. Results showed that in combination, the bit isolator and the drill chuck isolator provided a 7 dB(A) reduction in sound pressure level at the operator position. 2010 SME Annual Meeting & Exhibit Phoenix, Arizona

  5. 110 105 100 95 90 A-weighted Sound Level (dB) 85 80 75 70 65 60 250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000 6300 8000 10000 Overall 1/3-Octave-Band Center Frequency (Hz) A-weighted Sound Level Spectrum 108.9 dB(A) Baseline: T2 - 45 NR BISO, 45 NR CISO: 104.4 dB(A) T5 - 55 NR BISO, 55 NR CISO: 102.7 dB(A) 104.4 dB(A) T7 - 70 NR BISO, 70 NR CISO: 2010 SME Annual Meeting & Exhibit Phoenix, Arizona

  6. 1 3/8” Drill Bit Isolator – Design Review: Drill Bit isolator: Chuck isolator: 2010 SME Annual Meeting & Exhibit Phoenix, Arizona 1 3/8" DBI, R. Michael, PE

  7. Critical Area!! Look at metal components: Where would you expect max stress to occur? 1 3/8" DBI, R. Michael, PE

  8. Critical component – inner member, thin wall, stress concentration!

  9. Results: FE Analysis 1 3/8” DBI All cases, thurst load = 8,000 lb, torque = 300 lb-ft (3,600 lb-in) HOT SPOT! 1 3/8" DBI, R. Michael, PE

  10. Max Principal, s1 Min Principal, s1

  11. Max shear stress, tmax VERIFY FEA RESULTS WITH HAND CALCS!!!!

  12. Verify Principal Stresses with Hand Calculations or Mohr’s Circle!! Thrust Load = 8,000 to 10,000 lb Torsion Load= 300 lb-ft HOT SPOT! y x

  13. HAND CALCS: From Axial Load (Compression) From Torque

  14. HAND CALCS Cont’d: Principal Stresses: =-11.95 +/- 35.8 ksi How do these values compare with FEA results? Next: use Mohr’s circle to resolve

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