Snap ring groove stress concentration factors 2

[mikebos]

Power transmission shafting on conveying equipment that was purchased from a sub-contractor is failing at a snap ring
groove. The snap ring grooves are used to position a drive
sprocket on the shaft.

I need to check our sub's shaft design but can't find a
source for snap ring groove stress concentration factors.

Does anyone know of a source?

 

[boo1]

Mechanical Engineering Design, Shigley and Mitchell, 4th Ed
PP844 Table A-26-15, Charts of theoretical Stress-Concentration Factor Kt, Brooved round bar in Torsion.

If you give the Dia, Groove Dia, groove radia i'll look it up for you.

 

[boo1]

Are the shafts subjected too combined torsional and bending loads or shock factors?

 

[mikebos]

The shaft is subjected to combined bending and fluctuating torsional load.

I don't believe the stress concentration factors for a grooved shaft that you cited apply. In those cases the inside radius of the groove is 1/2 the groove width.
In the case of the snap ring groove in question the groove width is 1.85mm and the inside radius of the groove is 0.2mm.

 

[arto]

Look in Petersen's "Stress Concentration Factors"

 

[boo1]

Peterson list Kt in Chart 2.52 pp133 for flat bottom grooves. Peterson's, Stress concentration Fastors 2nd ed. chart 2.47, list the same graph as Shigley. Additionally Peterson lists additional U-shaped chart 2.48 and 2.49.

Shaft diameters are found using
d = [ (5.1/ Smax )((KmM)² + (KsT)² )1/2]1/3

d = shaft diameter, in.
H.P. = horsepower
Km = shock factor for bending loads
Ks = shock factor for torsional loads
M = bending moment, In-lbs.
N = revolutions per minute (RPM)
S = shear stress, lbs/in²
Smax = maximum allowable shear stress, lbs/in²
T = torque, in-lbs.
Tmax = maximum allowable torque, In-lbs

SHOCK FACTORS VS. TYPE OF LOAD

Type of Load Km Ks
Gradually applied load 1.0 1.0
Minor shocks,sudden load 1.4—2.0 1.0—1.5
Heavy shocks,heavy loads 2.0—3.0 1.5—3.0

Consider the fatique strength and the Groove Stress Concentration Kt reduction in the Smax

 

[mikebos]

boo1 and arto, thanks for your input. Peterson's book is no longer in print but I've located a used copy on the web.

 

[boo1]

Correction
d = [ (5.1/ Smax )((KmM)² + (KsT)² )**1/2]**1/3

 

[arto]

There's a new & improved edition of "Peterson's Stress Concentration Factors" by Pilkey et al. , but it's big $$:

http://search.barnesandnoble.com/te...userid=2VVRX7DFPJ&isbn=0471538493&TXT=Y&itm=4

 

[boo1]

That the the same as my copy, that I referenced above.