I have been asked to recheck the calc's. on a spline which has failed. I have the notes from the designer, who is no longer with the company, but the sources for some of the calc's. have not been noted. I've been searching our library but available info on splines is very low. Can someone point me in the right direction?
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Spline stress analysis question 1
- Thread starter bsmet95
- Start date
Two references that I use for splines:
Machine elements : life and design / Boris M. Klebanov, David M. Barlam, Frederic E. Nystrom, CRC Press, 2008
Chapter 5 Shaft-to-Hub Connections
Machinery's Handbook, 26th edition
Splines and Serrations, p2126-260
Machine elements : life and design / Boris M. Klebanov, David M. Barlam, Frederic E. Nystrom, CRC Press, 2008
Chapter 5 Shaft-to-Hub Connections
Machinery's Handbook, 26th edition
Splines and Serrations, p2126-260
mfgenggear
Aerospace
- Thread starter
- #4
gearcutter
Industrial
What sort of failure have the parts encountered?
Wear, tooth bending or shaft bending/rotating failure?
Ron Volmershausen
Brunkerville Engineering
Newcastle Australia
Wear, tooth bending or shaft bending/rotating failure?
Ron Volmershausen
Brunkerville Engineering
Newcastle Australia
In addition to gearcutter's questions about the type of failure the spline experienced, can you also provide some description of the spline dimensions, materials, manufacturing process used, and operating environment it was subject to (loads, cycles, lubrication, etc.).
Analyzing a spline joint, especially one that is highly loaded or is expected to extract maximum performance at minimum cost, is not a simple matter. To get the design right, it either requires someone with lots of experience, or it requires use of very conservative design factors. If you provide some more details, we can give some recommendations on how to best approach the analysis of your spline joint.
Regards,
Terry
Analyzing a spline joint, especially one that is highly loaded or is expected to extract maximum performance at minimum cost, is not a simple matter. To get the design right, it either requires someone with lots of experience, or it requires use of very conservative design factors. If you provide some more details, we can give some recommendations on how to best approach the analysis of your spline joint.
Regards,
Terry
I agree with tbuelna, spline analysis is no simple matter. It seems to be a very misunderstood concept.
Tbuelna, I would like to run some questions on the subject by you and get your thoughts. I don't want to hijack this thread, so I will make a new one.
-Chris
Tbuelna, I would like to run some questions on the subject by you and get your thoughts. I don't want to hijack this thread, so I will make a new one.
-Chris
- Thread starter
- #8
Attached are photos of the damaged internal and external splines, and dimensional data. The spline shaft material is 1144 ASTM A311 Class B cold drawn, the hub material is HRS 8620.
This is for a hoisting application. The max torque applied is 22,800 in-lb, but according to hoist duty spec's. we can use 65% of that, or approx. 15,000 in-lb. This hoist makes 15 lifts per hour, at 25 RPM, approx. 8 rev's. each time. All previous stress calc's. were based on full torque, however.
This is for a hoisting application. The max torque applied is 22,800 in-lb, but according to hoist duty spec's. we can use 65% of that, or approx. 15,000 in-lb. This hoist makes 15 lifts per hour, at 25 RPM, approx. 8 rev's. each time. All previous stress calc's. were based on full torque, however.
- Thread starter
- #9
gearcutter
Industrial
Wow!
Given the application; you've a very series problem.
I see no evidence of overload in those images.
Given the amount of fine debris; looks to me like you have a wear issue.
That could be material, mounting or alignment issues.
Is the hub axially fixed to the shaft or is it allowed to float freely?
How are the hub and shaft aligned?
Can you give us the hardness values of the materials used?
Ron Volmershausen
Brunkerville Engineering
Newcastle Australia
Given the application; you've a very series problem.
I see no evidence of overload in those images.
Given the amount of fine debris; looks to me like you have a wear issue.
That could be material, mounting or alignment issues.
Is the hub axially fixed to the shaft or is it allowed to float freely?
How are the hub and shaft aligned?
Can you give us the hardness values of the materials used?
Ron Volmershausen
Brunkerville Engineering
Newcastle Australia
- Thread starter
- #11
bsmet95,
Looking at the first set of photos of the failed parts it appears that you have a fretting problem. The fundamental tooth shear stresses and flank contact stresses are quite modest for the applied torque, and even with the relatively low strength steel materials being used for the shaft and hub, it would likely not present a wear problem if the spline joint had some form of grease or oil lubrication present.
The only other potential problem I can see is using the contacts of the external spline tips to the internal spline roots to carry the radial load on that half of the spool. Major diameter fit splines work well for providing accurate radial location of the mating parts, but they are not suitable for transferring large radial forces.
Looking at the first set of photos of the failed parts it appears that you have a fretting problem. The fundamental tooth shear stresses and flank contact stresses are quite modest for the applied torque, and even with the relatively low strength steel materials being used for the shaft and hub, it would likely not present a wear problem if the spline joint had some form of grease or oil lubrication present.
The only other potential problem I can see is using the contacts of the external spline tips to the internal spline roots to carry the radial load on that half of the spool. Major diameter fit splines work well for providing accurate radial location of the mating parts, but they are not suitable for transferring large radial forces.
- Thread starter
- #13
Thanks, tbuelna.
I wondered about this application, in which the spline acts as part of the beam and will have a radial load applied. The previous design had the spline shaft as part of the spool. Both ends of the spool were supported by bearings, and the spline transmitted torque only.
I wondered about this application, in which the spline acts as part of the beam and will have a radial load applied. The previous design had the spline shaft as part of the spool. Both ends of the spool were supported by bearings, and the spline transmitted torque only.
gearcutter
Industrial
Based on the set-up; it appears that the spline interface is being used as a flexible coupling.
Using a parallel spline for such a purpose will ultimately result in the sort of failure seen in this example........even if the spline is a major diameter fit.
A great deal of care needs to be taken when setting up these components to help ensure that mating parts are correctly aligned, as any misalignment will initiate wear.
Ron Volmershausen
Brunkerville Engineering
Newcastle Australia
Using a parallel spline for such a purpose will ultimately result in the sort of failure seen in this example........even if the spline is a major diameter fit.
A great deal of care needs to be taken when setting up these components to help ensure that mating parts are correctly aligned, as any misalignment will initiate wear.
Ron Volmershausen
Brunkerville Engineering
Newcastle Australia
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1
- #15
When in the past 20 years did the design change from supporting both ends of the drum with bearings to supporting one end with the spline?
What chamfer or radius is called for at junction of the major diameters and spline faces?
Does the spool carry cable? What is the diameter?
15,000 in-lbs is about 1250 ft-lbs. If the drum has a 6 inch radius that is 2500 lbs tangential force from a single strand lying on the drum face with a similar radial load. It might be applied anywhere along the drum face depending on how the cable lays.
With 0.001" to 0.004" diametral clearance of the major diameter I'd expect that much radial motion as the drum rotates while subjected to a one directional load. The spline faces are consantly sliding radially past each other. The root and tip chamfers/radiuses at the major diameters may interfere with each other as well.
I think fancy EP assembly paste lubrication and a Forsheda V-ring would be my only friends in that circumstance.
Or, return to the design with the radial load at that end supported by a real bearing.
What chamfer or radius is called for at junction of the major diameters and spline faces?
Does the spool carry cable? What is the diameter?
15,000 in-lbs is about 1250 ft-lbs. If the drum has a 6 inch radius that is 2500 lbs tangential force from a single strand lying on the drum face with a similar radial load. It might be applied anywhere along the drum face depending on how the cable lays.
With 0.001" to 0.004" diametral clearance of the major diameter I'd expect that much radial motion as the drum rotates while subjected to a one directional load. The spline faces are consantly sliding radially past each other. The root and tip chamfers/radiuses at the major diameters may interfere with each other as well.
I think fancy EP assembly paste lubrication and a Forsheda V-ring would be my only friends in that circumstance.
Or, return to the design with the radial load at that end supported by a real bearing.
I am Looking for some Help with determining the Effective Length of a Involute Side Fit Spline but can not find a calculation anywhere. I have the Machinist Handbook Spline section and it has a chart but I seems like there should be a calculation for this.
This is considered a Flexible Spline in the machinist handbook.
Ultimately I am trying to calculate the torque capacity of this spline shaft.
This is the data on the Spline:
Internal Involute Spline Data:
Flat Root Side Fit:
Number of Teeth: 16
Module: 2
Pressure Angle: 30°
Base Diameter: 27.7128mm
Pitch Diameter: 32.00mm
Major Diameter: 35.2800mm
Form Diameter: 34.40mm
Minor Diameter: 30.29mm
Circular Space Width:
Max Actual: 3.142mm
Min Effective: 3.183mm
Tolerance Class: 4H
Spline Callout: INT 16Z x 2m x 30P x 4H ANSI B92.2M-1980
External Involute Spline Data:
Flat Root Side Fit:
Number of Teeth: 16
Module: 2
Pressure Angle: 30°
Base Diameter: 27.7128mm
Pitch Diameter: 32.00mm
Major Diameter: 34.0000mm
Form Diameter: 29.89mm
Minor Diameter: 28.72mm
Circular Tooth Thickness:
Max Effective: 3.142mm
Min Actual: 3.076mm
Tolerance Class: 5h
Spline Callout: EXT 16Z x 2m x 30P x 5h ANSI B92.2M-1980
Shear Stress under roots of External Teeth:
Allowable Shear Stress (Table 11): SS: 40,000PSI
Spline Application Factor (Table 7):Ka: [/indent]1.2
Fatigue-Life Factors (Table 9): Kf: 0.5
Minor diameter, external spline root: Dre: 1.1925 in =30.29mm
Solid Shaft Stress: Ss: 10,511 PSI 3.81 Service Factor
Shaft stress with Fatigue and Life Factors: 25,226PSI = 1.59 Service Factor
Max Transmitable torque: T: 5,550 in-lbs = 1.59 Service Factor
Shear Stress at Pitch Diameter of teeth:
Allowable Shear Stress (Table 11): SS: 40,000 PSI
Spline Application Factor (Table 7): Ka: 1.2
Fatigue-Life Factors (Table 9): Kf: 0.5
Load Distribution factor (Table 8): Km: 2.5
Maximum effective Length (Fig. 4): Le:1.200 This is what I would like to calculate.
Pitch Diameter: D: 1.2598 in = 32.00mm
Number of Teeth: N: 16
Circular Tooth Thickness: Max Effective: t: 3.142
Actual Transmitted torque: T: 3,500 in-lbs
Calculated Shear Stress: 1,105 PSI = 36.19 Service Factor:
Compressive Stresses on the Sides of the Spline Teeth:
Allowable Compressive Stress (Table 11): SS: 3,000 PSI
Spline Application Factor (Table 7): Ka: 1.2
Fatigue-Life Factors (Table 9): Kf: 0.5
Load Distribution factor (Table 8): Km: 2.5
Maximum effective Length (Fig. 4): Le: 1.2
Pitch Diameter: D: 1.2598 in = 32.00mm
Number of Teeth: N: 16
Circular Tooth Thickness: Max Effective: t: 3.142
Actual Transmitted torque: T: 3,500 in-lbs
Wear-Life Factors (Table 10): Kw: 0.7
Circular Pitch: P: 12.7
Depth of engagement of teeth: h: 0.070866142
Compressive stress: Sc: 17,501 PSI = 0.17 Service Factor This is low and want to confirm the length.
Thanks in advance
This is considered a Flexible Spline in the machinist handbook.
Ultimately I am trying to calculate the torque capacity of this spline shaft.
This is the data on the Spline:
Internal Involute Spline Data:
Flat Root Side Fit:
Number of Teeth: 16
Module: 2
Pressure Angle: 30°
Base Diameter: 27.7128mm
Pitch Diameter: 32.00mm
Major Diameter: 35.2800mm
Form Diameter: 34.40mm
Minor Diameter: 30.29mm
Circular Space Width:
Max Actual: 3.142mm
Min Effective: 3.183mm
Tolerance Class: 4H
Spline Callout: INT 16Z x 2m x 30P x 4H ANSI B92.2M-1980
External Involute Spline Data:
Flat Root Side Fit:
Number of Teeth: 16
Module: 2
Pressure Angle: 30°
Base Diameter: 27.7128mm
Pitch Diameter: 32.00mm
Major Diameter: 34.0000mm
Form Diameter: 29.89mm
Minor Diameter: 28.72mm
Circular Tooth Thickness:
Max Effective: 3.142mm
Min Actual: 3.076mm
Tolerance Class: 5h
Spline Callout: EXT 16Z x 2m x 30P x 5h ANSI B92.2M-1980
Shear Stress under roots of External Teeth:
Allowable Shear Stress (Table 11): SS: 40,000PSI
Spline Application Factor (Table 7):Ka: [/indent]1.2
Fatigue-Life Factors (Table 9): Kf: 0.5
Minor diameter, external spline root: Dre: 1.1925 in =30.29mm
Solid Shaft Stress: Ss: 10,511 PSI 3.81 Service Factor
Shaft stress with Fatigue and Life Factors: 25,226PSI = 1.59 Service Factor
Max Transmitable torque: T: 5,550 in-lbs = 1.59 Service Factor
Shear Stress at Pitch Diameter of teeth:
Allowable Shear Stress (Table 11): SS: 40,000 PSI
Spline Application Factor (Table 7): Ka: 1.2
Fatigue-Life Factors (Table 9): Kf: 0.5
Load Distribution factor (Table 8): Km: 2.5
Maximum effective Length (Fig. 4): Le:1.200 This is what I would like to calculate.
Pitch Diameter: D: 1.2598 in = 32.00mm
Number of Teeth: N: 16
Circular Tooth Thickness: Max Effective: t: 3.142
Actual Transmitted torque: T: 3,500 in-lbs
Calculated Shear Stress: 1,105 PSI = 36.19 Service Factor:
Compressive Stresses on the Sides of the Spline Teeth:
Allowable Compressive Stress (Table 11): SS: 3,000 PSI
Spline Application Factor (Table 7): Ka: 1.2
Fatigue-Life Factors (Table 9): Kf: 0.5
Load Distribution factor (Table 8): Km: 2.5
Maximum effective Length (Fig. 4): Le: 1.2
Pitch Diameter: D: 1.2598 in = 32.00mm
Number of Teeth: N: 16
Circular Tooth Thickness: Max Effective: t: 3.142
Actual Transmitted torque: T: 3,500 in-lbs
Wear-Life Factors (Table 10): Kw: 0.7
Circular Pitch: P: 12.7
Depth of engagement of teeth: h: 0.070866142
Compressive stress: Sc: 17,501 PSI = 0.17 Service Factor This is low and want to confirm the length.
Thanks in advance
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