Maximum Contact Stress To Prevent Clamp Marks
Maximum Contact Stress To Prevent Clamp Marks
(OP)
Hi,
I need to clamp AISI 1018 Steel, cold drawn, round bar between a pair of v-blocks, which will most likely be made from A2 tool steel. The round bar needs to be clamped while the end of the bar is chamfered and end faced. However, the round bar can not have any marks on it. I can calculate the hertzian contact stress between the round bar and the v-blocks. I need to minimize the length of the v-blocks. At what contact stress or shear stress will I begin to see clamp marks on the round bar?
Thanks
I need to clamp AISI 1018 Steel, cold drawn, round bar between a pair of v-blocks, which will most likely be made from A2 tool steel. The round bar needs to be clamped while the end of the bar is chamfered and end faced. However, the round bar can not have any marks on it. I can calculate the hertzian contact stress between the round bar and the v-blocks. I need to minimize the length of the v-blocks. At what contact stress or shear stress will I begin to see clamp marks on the round bar?
Thanks





RE: Maximum Contact Stress To Prevent Clamp Marks
Regards,
Lcubed
RE: Maximum Contact Stress To Prevent Clamp Marks
RE: Maximum Contact Stress To Prevent Clamp Marks
Take a look at this for Hertzian Stress calculate
http://www.tribology-abc.com/default.htm
Kevin Hammond
Mechanical Design Engineer
Derbyshire, UK
RE: Maximum Contact Stress To Prevent Clamp Marks
This for tube,but you should find clamp info. here.
RE: Maximum Contact Stress To Prevent Clamp Marks
Why not just add a soft copper shim between the round bar and the v-block? The copper will deflect and the round bar will look great. And it will compensate for any overtightening caused by the operator.
RE: Maximum Contact Stress To Prevent Clamp Marks
RE: Maximum Contact Stress To Prevent Clamp Marks
That is correct. Reference Nadai and Wahl, PLASTICITY. Theoretically, permanent indentation occurs at 1.81 x Fty. Setting your maximum clamping pressure so as to hold maximum Hertzian stress to 1.8 x Fty should keep you out of trouble; less would be even better.
Regards,
Lcubed