# Material required for shaft.

1. Sep 27, 2008

### shams alam

I want to find out suitable material with it physical properties, like allowible shear stress, which will be suitable for the shaft with following given data.
R.P.M = 40 rpm
Transmitting torque = 2100 kNm
Length of the shaft = 2740 mm
Smooth drive.
Neglecting the bending movement of the shaft.

2. Sep 27, 2008

### Q_Goest

Selecting the material requires knowledge of the stresses, and no one can know those stresses without doing the analysis on the particular shaft geometry. You need all the loads (not just torque) in addition to all the geometry.

3. Sep 28, 2008

### ank_gl

2100kNm & shaft length of over 2m, neglecting Bending Moment would be stupid.

Start finding all the stresses, eg, torsional stress & bending stress, calculate the maximum stress induced, assume an appropriate factor of safety depending upon the application, get the minimum strength required using FoS * Stress induced, select a material.

4. Sep 28, 2008

### Q_Goest

That's pretty good ank_gl, and it's not incorrect. But don't forget that a shaft is typically subject to fatigue, and it's typically the fatigue calculation that governs the final design.

5. Sep 28, 2008

### FredGarvin

Not necessarily. The OP hasn't mentioned anything about how the shaft is supported, i.e. the locations/spacing of the bearing surfaces. That is going to be the biggest factor in the real design in that the rotordynamics will dictate whether the bending moment argument is valid or not.

6. Sep 29, 2008

### ank_gl

yes right, but I meant that FoS should take care of all those things.

oops!! forgot that part altogether about BM

7. Sep 30, 2008

### mshinavar

and so is neglecting friction and aero drag in dynamics problems, but when you're a student you have to start somewhere. basically, im assuming the OP is a student, since the question has that school-ness ring to it