Connectors for joining aluminum plates

Project ID:  D2018-49

Background

Joining aluminum and other metal sheets using conventional processes can be problematic. Resistance spot welding (RSW) can expel molten metal, introduce voids/cracks and gas pockets, cause distortion, residual stresses and overall reduced fatigue strength. Friction stir welding (FSW) leaves an exit hole, requires heavy clamping due to significant downward and traversing forces, and is not ideal for thin sheets, curved joints, or sheets of dissimilar thickness. Friction stir spot welding (FSSW) offers only medium shear capacity and low peel resistance. Self‑piercing riveting requires significant clamping and dedicated dies.

Invention Description

Researchers at The University of Toledo have developed a family of steel connector plates that join aluminum or other metal sheets by forming robust mechanical interlocks without fusion welding.

• Self‑driven screw arrays—two‑sided screws mounted in a bracket within a plate, with opposing thread directions and optionally variable pitch along the shank; when clamped between sheets, applied torque drives the screws into both sheets to form the joint.
• Punched arrow‑head protrusions—arrow‑shaped projections and matching openings created by punching the plate; their overhanging side points interlock with the sheet when compressed.
• Forged semispherical‑head projections—rivet‑like domed heads on necks that penetrate the sheets and lock under compression.
• Forged cross‑head projections—cross‑shaped heads with four overhangs around a circular neck that bite into the sheets.

These connectors can be placed between two sheets or on one side, then compressed to drive projections into the material and create multi‑point interlocks. Finite‑element analyses show lowered stress concentration in joints using these distributed protrusion arrays.

Applications

• Joining aluminum/aluminum sheet or plate sections where welding is undesirable (heat‑sensitive assemblies, coated sheets).
• One‑sided or two‑sided field assembly of sheet structures using simple presses or clamps.
• Curved or irregular joints and joints spanning dissimilar sheet thicknesses.
• Retrofitting or reinforcing existing joints without adding heat.

Advantages

• No complex fixtures, tool alignment, dies, or specialized welding equipment; no harmful gases or fumes.
• Connector geometry (projection shape/size/spacing) can be tailored to the joint; plates can follow part curvature.
• Creates strong, service‑stable mechanical interlocks; self‑driven screw arrays are loosening‑resistant and suited to thick plates.
• Lower stress concentration and increased joint strength demonstrated via simulation.
• Enables joining from one side or between sheets; accommodates aluminum and other metals.

Lead Inventor: Hongyan Zhang

IP Status: US 11,313,395 B2

Keywords:                  

aluminum sheet joining, mechanical interlock connector, self‑driven screw array, arrow‑head protrusion, semispherical head projection, cross‑head projection, stainless steel connector plate