Rivet Tool
Process Improvement at Product Insight 2025
Background
At Product Insight, I designed a lot of systems with blind set rivets as the joint for sheet metal designs. I had validated my design decisions using hand calculations, but I wanted to streamline the calculations, centralize our company's riveted joint assumptions, and build a tool for other engineers to use effectively and efficiently.
I created a Riveted Joint Tool that took the joint inputs and automatically calculated joint characteristics:
Inputs:
-
Shear and Tensile Loads
-
Max, min, and assembly temperature
-
Rivet Size, material, and type
-
Hole Size
-
Joint material thicknesses and type
-
Number of rivets
Outputs:
-
Shear and Tensile FOS at different temperatures
-
Force to separate the joint
-
Tensile stress in the Rivet and the Joint at each material interface
-
Slip resistance FOS
-
Combined load FOS
Tool Screenshot
Image output will change with joint inputs, represents the size and frustum cone of the joint
Global inputs drive the joint temperature and external loads to the system
These numbers automatically update, but walk a user where the calculations are occuring
Additional tabs in the Excel document contain values like:
-
Rivet standards
-
Material thermal properties and strengths
-
Constants used for bolted joint calculations
Outputs are summarized in one 'screenshottable' location for output into Design Reviews or other presentations
Joint can be 2-3 parts thick
Assumptions and Calculations
The largest assumption that I had to make to calculate the joint Factors of Safety (FOS), was that when a blind set rivet is installed, there is a preload applied in the system. I estimated that a certain percentage of the mandrel break force (the force the riveter applies to the mandrel to snap it off and permanently deform the rivet) gets translated to the joint. This preload prevents slip, compresses the materials in the joint, and allows us to use bolt calculations in a riveted joint. Mandrel break force is a reproted number that is standard across installations and allows the simplification of a tool rather than testing each rivet joint for failure.
I left Product Insight before I was able to physically test this assumption, but included in the assumptions slides is a test plan to use pressure paper between the material layers to calculate stress, area, and therefore clamp force at those sections.
