What is shot peening?
Shot peening is a method used to increase the strength of the metal. Shot peening involves counteracting the internal stress in a piece of metal with compression forces from a unique device. Shot peening produces modified and enhanced qualities in the metal. It also reduces the stress corrosion failures to improve metal’s performance and service life cycle.
Shot peening works by applying compressive stress, making it the most economical and effective way to extend a car’s, aircraft’s, or structure’s parts and fatigue life.
Shot peening is an industrial application used to increase the toughness and stability in aviation, manufacturing, and energy plants.
How shot peening works
Highly specialized technician work should do shot peening. Shot peening is a highly controlled process where technicians control the tools, materials, and intensity depending on the project being handled. The spherical media is known as a shot.
During shot peening, tiny metal particles blast around at great force. As the shot hits the metal surface, it creates an indentation. The target surface attempts to resist, but substrate material offers resistance.
Therefore, use protective eye protection glasses during the process. Shot peening is similar to shot blasting sandblasting. However, the latter two are significantly abrasive to clean a metal’s surface. On the other hand, shot peening uses a high-pressure impact on modifying and enhancing the metal’s properties and life cycle. Shot peening can also be used for ceramic and glassware.
Each tension release is referred to as a stress riser. The impact on the recipient surface surrounding the stress risers and the pressurized material compresses the metal to strengthen the bond in their elements. The strengthening pressure prevents separation and segmentation within the metal.
Therefore, shot peening reduces internal stress and prevents the formation of fissures. This is because shot peening creates opposite tension.
However, shot peening does not remove or reduce the intensity of existing cracks; instead, it covers them. It is critical for the technician to inspect the metal for possible weakness before shot peening. Inspection before shot peening ensures undamaged parts and produces a finished whole metal part. Shot peening is effective for:
- Metal fatigue
- Corrosion due to cracking
- Wear and tear
- Inter-granular corrosion
Common parts ideal for the shot peening process
Particular parts suitable for the shot peening include:
- Aircraft frame and components
- Gear wheels
- Turbine blades
- Coil springs
- Connecting rods
- Suspension springs
Considerations for shot peening process
Shot peening application is ideal for metal strengthening and durability. The following considerations should be put to mind when working on the shot peening process:
- manufacturing method
- geo-metrical composition
- strain sensitivity level
- the base material
- loading conditions
- in-service environment
- turnaround time
What next after these considerations
Once the above eight considerations are put in place, the following quality parameters can also be established:
- Choice and size of the spherical media
- Determination of the compressive layer depth
- The intensity of the shot pressure
- The scope of coverage
These parameters are used to calculate the surface stress and then tested before application. If any repeat peening is necessary, the technician should follow the initial specification and other subsequent peening services.
Many shot peening service providers use robotic equipment to enhance precision and consistent performance.
The intensity in shot peening process
Intensity is an essential element in the shot peening process. The intensity of the shot peening blast is measured by the amount of bending or deformation at the Almen gauge.
The intensity during the shot peening process is determined by shot size, hardness, density, and velocity adjustments. The more these factors are increased, the greater the intensity of the peening process.
Coverage in the shot peening process
Coverage is another critical parameter in the shot peening process. Coverage refers to the percentage surface area of the target metal part dimpled by the shot peening process or the media. Adequate coverage in the shot peening process should be 100%.
Shot peening equipment
Shot peening equipment includes machinery, components, and systems for projecting peening media against the target metal surface. Some of the peening equipment includes:
Commercial shot peening machines
- Flat peeners
- Peening machines
- Peen formers
- Laser ablation also, known as laser peeners
- Shot peeners
- Micro-dimpling peeners
- Micro shot peeners
- Ultrasonic needle peening equipment
- Wheel shot peening device
- Airless shot peener
- Shot peening cabinets
- Portable shot peeners
Other applications that use controlled shot peening services
- Shot peening forming
The shot peening forming process uses compressive pressure to alter magnitude, stress pattern, and depth. Ultimately, the shot peening process can be used to transform a component’s shape. For instance, it can form the curvature in aircraft wings to increase resistance and enhance speed. Increased resistance also improves flexural bending pressure, varies curvature requirements, cut-outs, and pre-existing distortion.
- Corrects distortion
During manufacturing , metals can have a defective distortion, such as rolling, forging, casting and heat treatment. A minor distortion can cause a repetitive stress pattern and alter its function. It can also increase stress corrosion rate, cracking, and fatigue.
Typical applications for shot peening for distortion include large connecting rods, rocket structures, transmissions, and crankshafts.
- Isotropic superfinishing
Isotropic surface finishing is also known as isotropic superfinishing. It is developed as a metal surface treatment that provides excellent bending features to metal parts.
Valleys are essential for effective lubrication. When combined with an appropriate chemical process, a shot peening produces a top-notch finish. Lubrication is a necessary part movement for gears, pistons, and transmissions.
- Surface texturing
Shot peening can be used for surface texturing, an ideal option for decorative functions. Texturing offers protection for architectural works such as signage, nameplates, welded structures, and cladding.
The controlled shot peening process forms an essential element in the manufacturing process for improving tear and wear and corrosion resistance. It also prevents premature fatigue mishaps.
The shot peening process is a comprehensive process that projects shot peening media against a metal surface to modify the engineered components. Shot peening requires specialized tools, equipment, and machinery to achieve a modified metal surface. The shot peening media can be separated, reused, reclaimed, and recycled.