shear capacity of dowels
shear capacity of dowels
(OP)
Is there any data published on shear capacity of plain dowel pins eg BS 1804 or EN ISO 8734? These standards give hardness values but no indication of shear strengths or load capacities. I have estimated a shear capacity using a formula for hardness vs tensile strength but am not sure how accurate this is?





RE: shear capacity of dowels
RE: shear capacity of dowels
RE: shear capacity of dowels
I think what is going in here is that the bolts, when torqued to the proper spec, will see the load before the dowels ever would. If the two parts were assembled without any bolts and only dowels then the dowel would see load, but the bolts are preventing the assembly from moving and therefore carrying any side load.
RE: shear capacity of dowels
τ = F/A
where
τ = shear stress acting on dowel
F = applied force
A = dowel cross-sectional area
If dowel yielding is the allowable failure mode, then:
τ < τY
where
τY = dowel material shear yield strength
τY = 0.577 σY
where
σY = dowel material tensile yield strength
If dowel fracture is the allowable failure mode, then:
τ < τU
where
τU = dowel material ultimate shear strength
τU ~ 0.6 σU
where
σU = dowel material ultimate tensile strength
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: shear capacity of dowels
But surely your design typically carries the shear as friction between the two surfaces generated via bolt tension, rather than direct shear in the dowels?
Cheers
Greg Locock
RE: shear capacity of dowels
The tighter the tolerance on the dowels the harder it makes any interchangeability of the pump parts. The interchange of the pump housing components requires that the dowels be enlarged and the shaft bores be bused and reground.
We have a number of smaller gear pumps that have 2 dowels and they are designed to carry a shear load imposed by very high pressure differential across the gears. As these dowels are not being used for location the tolerances of the dowel pins are looser. We have almost complete interchange of parts on these pumps.
It really depends on what you need the pins to do. The best way is to determine what you need strength wise and work backwards. Keep with 2 pins if possible. Watch pins near the edge. Watch the pin interference also if near a an edge or hole.
RE: shear capacity of dowels
Good question. I was trying to speak from the most general perspective. I define a dowel pin as an interference fit cylinder that is used to transfer shear forces. Most bolted joints do not contain these, but those that do use the dowel to resist shear forces and screws (if any) to resist tension forces. Bolted joints usually have three varieties: tension, shear-bearing, and shear-friction. Most joints are shear-friction - screws are used with oversized holes and shear force resistance is provided by the friction force developed by the fastener preload. Shear-bearing has the fastener in a close fit hole so that the fastener takes shear forces by the hole edge bearing against the screw shank. Lastly, tension joints have screws in oversized holes with essentially no shear forces, so the only forces are tension/compression.
Perhaps others refer to locating pins as dowels. These pins are loose fit and provide no force resistance. Then, the joint is one of the three above, usually shear-friction.
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: shear capacity of dowels
10,000 psi for Al.
25,000 psi for Cu.
35,000 psi for bronze
35,000 psi for hot rolled .1% steel
45,000 psi for cold rolled .1% steel
60,000 psi for Stainless steel
65,000 psi for silicon steel
RE: shear capacity of dowels
Cheers
RE: shear capacity of dowels
Assuming you have standard material composition and processing, your formula ought to be correct within ~10%. If you need more accuracy, you can perform simple testing to obtain the shear strength of the pin.
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: shear capacity of dowels
RE: shear capacity of dowels
RE: shear capacity of dowels
The formula that SPS cites is shear strength (based on conversion from hardness) x pi x D^2 / 4
RE: shear capacity of dowels
Cheers
Rattler