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Shot Peen Forming

Shot Peen Forming uses the compressive stress induced by controlled shot peening to deliberately create a change in the component shape. Gentle curves within the elastic range of the material are regularly formed to consistent tolerances.

Varying curvature requirements, material thickness, cut outs, reinforcements and pre-existing distortion can all be processed with Shot Peen Forming. When peen formed parts are processed on one side only, the result causes both sides to have compressive stress offering enhanced fatigue protection on the whole component.

Process

Curtiss-Wright Surface Technologies’ shot peen forming is a dieless process performed at room temperature. Every piece of shot acts as a tiny peening hammer producing elastic stretching of the upper surface and local plastic deformation that manifests itself as a residual compressive stress. The combination of elastic stretching and compressive stress causes the material to develop a convex curvature on the peened side.

Laser peening is an alternative technique for thick component section peen forming. With much deeper compressive stress over conventional shot peeing, thicker cross sections can be formed or a tighter radius of curvature can be achieved.

Shot Peen forming
CWST can take the formed wing model and guide the shape of the flat pattern

Applications & Benefits for Shot Peen Forming

This process is ideal for forming large panel shapes where the bend radii are reasonably large and without abrupt changes in contour. Hence it is best suited for curvatures where radii are within the metal’s elastic range. Although no dies are required for shot peen forming, for severe forming applications, stress peen fixtures are sometimes used. This process is effective on all metals, even honeycomb skins and ISO grid panels.

Also, it is often more effective in developing curvatures than rolling, stretching or twisting of metal. Saddle-back shapes also are achievable. Because it is a dieless process, it reduces material allowance from trimming and eliminates costly development and manufacturing time to fabricate hard dies. The shot peen forming process also is flexible to design changes, which may occur after initial design.

Shot peening of parts that have been cold formed by other processes overcomes the harmful surface tensile stresses from these other forming processes.

Application

Benefits

  • Wingskins 
  • Airframe components
  • Transmissions
  • Large connecting rods
  • Crankshafts
  • Shafts (generally)
  • Rocket structure
  • Resistance to flexural bending fatigue and stress corrosion cracking 
  • No forming dies are required 
  • Performed at room temperature
  • Peen forming can be performed with or without an external load applied on the component
  • Corrects distortion caused by manufacturing processes

Correction of Distortion

A potential method of correcting distortion caused during manufacturing through casting, rolling, forging and heat treatment, is using controlled shot peening to stretch the material on one side of the distorted component to bring the component back to within tolerance.

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