Contact stress under flat woven web sling
Contact stress under flat woven web sling
(OP)
Hi
Does anybody know of an equation/reference for the contact stress distribution found between a flat strap web lifting sling around a circular section, (contacting half the circumference). I need to calculate the contact stress for the material is very delicate and don't wish to crush when loading
Many thanks for any help
George
Does anybody know of an equation/reference for the contact stress distribution found between a flat strap web lifting sling around a circular section, (contacting half the circumference). I need to calculate the contact stress for the material is very delicate and don't wish to crush when loading
Many thanks for any help
George






RE: Contact stress under flat woven web sling
My suggested approach would be to consider a 45 degree radial, centered on the bottom of the circular section. This will give you an average contact stress over the length of the sling from 22.5 degrees, either side of the bottom center, times the sling width.
Otherwise you could resolve each angle from 90 degrees either side and see how the contact stress transitions to shear-friction as you approach 45 degrees either side of the bottom center.
RE: Contact stress under flat woven web sling
BA
RE: Contact stress under flat woven web sling
BAretired - I think 2T/wD would be the projected stress as an average across the diameter? The peak stress would be in the center diminishing to 0, perhaps a circular function, or parabolic I would imagine?
Ron, yes this seems a good assumption, so essentially put an average stress across projected onto the middle third of the diameter?
I was hoping there was a tidy equation that described it, perhaps frictionless if that was more straightforward.
A belt on a pulley was another analogy, but there seems to be little description anywhere?
Thanks
George
RE: Contact stress under flat woven web sling
2T/wD looks good to me as an average max bearing stress, assuming no geometric irregularities and the like. Consider some fairly soft padding (medium durometer) btwn. the sling and the vessel which will compress and distribute any high stresses at irregularities. While max. contact (bearing) stress is certainly of interest when lifting your product, and selecting the proper sling, etc.; the bigger question might be how does the total circumferential loading affect your product given its shape, delicacy, etc.? How has this product been supported during production, and how will it be supported in its final installed location; they may be more significant and concentrated loadings. And finally, how is it going to be supported in transit and under those rougher handling conditions.
RE: Contact stress under flat woven web sling
RE: Contact stress under flat woven web sling
BA
RE: Contact stress under flat woven web sling
That's a fantastic description. To dhengr, funnily enough the material was never in transit until its final installation, as its a tree supporting a temporary treehouse for an art exhibition and the rigging is a suspension point from a branch, at the union.
The predominant failure mechanism will be bearing stress via truss action to the support (stem) as within a distance of D to it. The shear capacity is inordinately high and no bending stress.
Does that seem a fair assumption? We have an arborist who checks health and we are load testing to check for latent defects.
Thanks