Failure modes

Failure in mechanically fastened joints is a complex competition between different possible failure modes. We examined the major failure modes illustrated below and looked at which design variables are dominant in each failure mode.

Accompanying Failure Load Formulas

Net Section Failure:  𝐹_{𝑁 𝑆𝑇}=𝑡(𝑊−𝑛⋅𝑑)⋅𝜎_𝑡𝑢, with n the number of fasteners along net section, d the diameter of the fastener, and t the plate thickness of the section.

Bearing Failure: 𝐹_𝑏𝑟=𝑑⋅𝑡⋅𝜎_𝑏𝑟, with d the diameter of the bolt and t the thickness of the sheet

Shear Out Failure:  𝐹_𝑆𝑇𝑂=2⋅𝑏⋅𝑡⋅𝜏_𝑠𝑢, with b the distance to the edge and t the thickness of the sheet.

Fastener Shear Failure: 

,with d the diameter of the bolt and n the number of shear plains (n = 1 for 2 plates, n = 2 for 3 plates etc.)