1994 FIN – Huck Uses Personal Computers in Designing Blind Fasteners
FASTENER HISTORY
1994 FIN – Huck Uses Personal Computers in Designing Blind Fasteners
November 28, 1994 FIN – Huck International engineers have modeled the deformation of a metal fastener using a personal computer, yielding improved design for blind fasteners on airplanes.
The finite-element analysis (FEA) package Inertia from Indianapolis, Indiana-based Modern Computer Aided Engineering automatically rebuilds the model and updates load increments and shields users from non-linear problems.
“Huck’s analysis showed two design variables that could be changed to more effectively position the clamping portion of the blind fastener, making it better able to join metal panels of varying thickness.” Huck product engineer Dave Hazelman told FIN.
“Solid rivets in airplanes require access to the back of a hole,” Hazelman said. “Someone must take a bucking bar and pound the back side of the rivet so that it collapses and squeezes the pieces of metal together.”
Where there is no access, blind fastener replace conventional rivets. An installation gun pulls a pin against a metal sleeve with an annealed area designed to collapse. The pin head bears against the blind end of the sleeve until it collapses to form a bulb similar to the back of a solid rivet. Then the pin breaks off leaving a countersunk fastener.
Huck makes blind rivets, bolts and the Huck clinch primarily for aerospace uses.
The clinch is a less expensive rivet to clamp the outside sheet metal together.
Huck first used FEA to improve performance of blind bolts made of titanium where the bolt had to have a wide grip range and precise collapse area positioning.
“Huck could control the manufacturing process for the bolt, but the collapse of the sleeve was due entirely to the plastic deformation characteristics of the titanium, which they could not control until they understood it,” Hazelman said.
That required non-linear analysis, he added.
The results taught engineers that there was some bending in the sleeve at the beginning of the collapse that they had not been aware of. The analysis pointed out unexpected distortions.
The computer program allowed engineers to investigate redesign options quickly. ©1994/2010 Fastener Industry News
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