Understanding Failure in Helical Gears: The Role of Rolling and Sliding Contact

[Nahahahah]

Hi everyone.
I'm a college student, and I need help of experts with gears.

What I know is that there are two dynamics in gear : rolling and sliding.
And I heard that the main cause of failure (wear) of spur gear is rolling.

Then... how about the cause of failure in the case of helical gear??
I felt that the sliding works as more important role in helical gear than spur gear because of their geometry.
But I can't find any literature that comparing effect of rolling and sliding on the surface of helical gear teeth (especially for failure).

And what is a difference between failure by rolling and sliding on the gear teeth??

I hope I could get an answer...
Thank you!

 

[Baluncore]

Then... how about the cause of failure in the case of helical gear??

Think of the helical gear as a stack of very thin spur gears with a one tooth twist in the stack. You will then see that helical and spur gears should be identical in wear characteristics. The advantage of helical is that there is no instant of tooth meshing contact, so the gears run quieter. The disadvantage is the end thrust.

And I heard that the main cause of failure (wear) of spur gear is rolling.

Where did you hear that? Do you have a reference?

 

[Dr.D]

And I heard that the main cause of failure (wear) of spur gear is rolling.

In it not clear just what this statement means. In a spur gear, there is sliding contact at all points of engagement other than momentarily at the pitch point. Nothing actually rolls. What exactly did you have in mind here?