CASE STUDY – Combined Loading

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.

2. Bit Isolator Drill Depth up to 48” Chuck Isolator

3. 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. Ref: Noise controls for roof bolting machines, P. Kovalchik, A. Smith, R. Matetic and J. Peterson

5. FULLY BONDED: 1 3/8”” 1 3/8” Drill Bit Isolator – Design Review: Drill Bit isolator: Chuck isolator: 1 3/8" DBI, R. Michael, PE

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

7. 1 3/8" DBI, R. Michael, PE

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

9. Max Principal, s1 Min Principal, s1

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

11. HAND CALCS: From Axial Load From Torque Principal Stresses: =11.95 +/- 35.8 ksi How do these values compare with FEA results? Next: use Mohr’s circle to resolve