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In orthogonal turning of a cylindrical tube of wall thickness 5 mm, the axial and the tangential cutting forces were measured at 1259 N and 1601 N, respectively. The measured chip thickness after machining was found to be 0.3 mm. The rake angle was 10° and the axial feed was 100 mm/min. The rotational speed of the spindle was 1000 rpm. Assuming the material to be perfectly plastic and merchant’s first solution, the shear strength of the martial is closest to
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- 875 MPa
- 200 MPa
- 722 MPa
- 920 MPa
- 875 MPa
Correct Option: C
For, orthogonal turning,
λ = 90° , Fc = 1601 N
Chip thickness ‘tc ’ = 0.3, Ft = 1259 N
N = 1000 rpm, α = 10 m
| f = 100 mm / min = | mm / rev | |
| 1000 |
| f = 0.1 | = t | |
| rev |
| r = | = | = | ||||
| tc | 0.3 | 3 |
| Fa = τs × | ||
| sinφ |
| ⇒ τs = | ||
| 6 × t |
| tanφ = | ||
| 1 - rsinα |
⇒ φ = 19.19°
Fs = Fccosφ - Ftsinφ
Fs = 1601 × cos19.19° - 1259 × sin19.19° = 1098.20 N
| τs = | = 721.96 ≈ 722 MPa | |
| 5 × 0.1 |
