SEED Guides Shaft-loads < >

7. Choose Material & Material Properties
Material choice is constrained by many considerations involving performance, manufacturing and commercial factors. In practice, the apparently wide choice is limited (for shafts) to only a few.

Fatigue data is not always quoted and may have to be assumed. In this case, calculate Fatigue Ratio using the following relationships:

f e' = 0.5f u (for steels) f e' = 0.4 f u (for cast irons)

Quoted fatigue data may be restricted to 'rotating-bending' tests.

In the absence of validated data for other stress types use the following relationships:

f e'(t) = 0.85 f e' (for tensile/compressive loads) f e'(T) = 0.6 f e' (for torsion loads)

Consult the the standard references or the British Standards for other material properties.

The table shows mechanical properties (particularly fatigue related data) for some typical shaft materials.

MATERIAL BS 970
SPECn. 		TREATMENT FATIGUE
STRENGTH
MN/m2 (107) 		ULTIMATE
STRENGTH
MN/m2 		YIELD
STRENGTH
MN/m2 		FATIGUE
RATIO
fe'/fu
CARBON
STEEL 		070M20
070M26
080M30
080M40 		N
N
N
H&T 		193
201
232
278 		400/430
430/500
460/500
620/780 		200/230
220/250
230/250
390/460 		0.45/0.48
0.40/o.47
0.46/0.50
0.37/0.45
LOW ALLOY
STEEL 		En22
722M24
653M31
976M33 		H&T
H&T
H&T
H&T 		525
293
432
486 		772/850
850/1080
770/1000
950/1050 		590/680
650/760
590/680
770/820 		0.61/0.68
0.27/o.35
0.43/0.56
0.46/0.54
CARBON
STEEL 		070M20
070M26
080M30
080M40 		N
N
N
H&T 		193
201
232
278 		400/430
430/500
460/500
620/780 		200/230
220/250
230/250
390/460 		0.45/0.48
0.40/o.47
0.46/0.50
0.37/0.45