Shot Peening

If you are looking forward to knowing more about this incredible revolution in the Blasting Industry that improves resistance to fatigue, read our blog below.

What is Shot Peening?

Shot Peening is a process that is specifically aimed at reducing fatigue of components that are subject to high alternating stress. Surface treatment procedures like grinding, milling, bending or heat treatment procedures cause Tensile Residual Stress. This Tensile Residual Stress leads to low life cycles of the parts.

Shot Peening converts Tensile Residual Stress into Compressive Residual Stress which leads to significant increases in the life cycle of parts and their maximum load capacities.

Shot peening will lengthen the fatigue life of any part, that is subject to bending or twisting stress or 2 wheeler motor bike like Honda, bajaj, Suzuki, TVS and 4 wheelers car manufacturers like maruti, Honda, tata, fiat, M&M, BMW, Volvo and others uses shot peening process on their components to increase fatigue life of parts.

Shot peening is a process specially developed to improve the properties of components which are exposed to changing strains. For safety reasons, shot peening is also now absolutely necessary in the aviation and space industries. And shot peening is essential in all industries requiring long lives for components. This includes the automotive sector as well as many other industries.

The requirements for the shot peening method are becoming increasingly more comprehensive.

Different Peening Processes

Shot Peening

• Used to induce residual compressive stress in the surface of components that are prone to cyclic and repetitive loads, the process also reduces stress corrosion cracking.

Shot Peen Forming

• This process compresses and extends the superficial layer of the component causing it to bow. Typical applications include the formation of skins, wing flaps, access panels, and sections of fuselage.

Correction Of Distortion

• (The reverse of shot peen forming) Shot peening is used to stretch and compress a localized area to achieve perfect flatness after a part has been distorted by heat or machining. Complex structural parts, ribs and spars typically undergo this process.

Mechanics of Shot Peening

Shot peening is a cold working process used to produce a compressive residual stress layer and modify the mechanical properties of metals. It entails impacting a surface with a shot (round metallic, glass, or ceramic particles) with a force sufficient to create plastic deformation.

Peening a surface spreads it plastically, causing changes in the mechanical properties of the surface.

The main benefit of shot peening is the delay or prevention of cracks in highly tensile stressed alloy components. We can alter these undesirable manufacturing and operational tensile stresses to life enhancing residual compressive stresses therefore extending component life.

The process works by introducing the residual compressive stress in the surface of the component. The compressive stress helps to prevent crack initiation as cracks cannot propagate in the compressive environment generated by peening.

Compressive stresses are generated when the impact of each particle of shot on the component produces a small indentation. It follows that if the surface has been dented, then the material beneath the dent has been compressed. Peening generates not just one dent but many thousands over the surface. Eventually the component becomes encased in a compressively strained layer.

Shot peening is performed by accelerating spherical media toward the surface of a part. When the media hits the part, a small dent is formed, stretching the surface of the part. The material surrounding that dent resists this, and creates an area of compressive stress. When the surface of the part has these small dents all over the surface, there is a continuous layer of compressive stress on the surface of the part. This replaces the tensile stress on the surface with a compressive layer. The compressive layer stops the fatigue cracks and stress corrosion that typically start at the surface of the part.

Shot peening improves the fatigue strength or working life for many components, including:

• transmission gears, axles, universal joints, and drive shafts
• connecting rods and crankshafts
• pistons, cylinder heads and blocks
• turbine engine disks, blades and shafts
• aircraft wing skins, stringers and chords
• landing gears
• filets
• wheels
• valves
• springs