Wheelabrator presents state-of-the-art peening technologies to prepare, peen and finish an extensive range of components across all industry sectors.
Shot peening is used widely to enhance the fatigue resistance of highly stressed metallic components. This in turn, will improve the performance of safety-critical components. Any metallic component that is subjected to cyclic stresses within its elastic limit will benefit from the shot peening process.
Peening is achieved by propelling a stream of media (precisely manufactured round steel shot, glass or ceramic beads) at components, at high velocity under fully controlled conditions, utilising a compressed air stream or, centrifugally, by means of a vaned wheel. Components that benefit from this technology include aero engine fan blades, aircraft structural parts and automotive transmission systems.
Peening is different from cleaning various functions such as media velocity, media size, shape to name a few. The table below summarises the differences:
Measuring effectiveness with Almen strip The efficacy of the process is important to ensure the correct intensity of stress is being created. This is achieved with the aid of an Almen strip. This strip is manufactured from spring steel for strict tolerance of hardness, size and flatness, and is peened on only one side. The effect of the induced compressive stress on the strip results in bowing or curving and the extent of the curve is proportional to the energy imparted by the shot, measured on an Almen gauge. This shows the amount of energy imparted by the stream of shot and absorbed by the strip, thus measuring the effectiveness of the process.
X-Ray diffraction techniques also provide an accurate method of measuring the actual stresses within the component and quantifying the actual effect of the peening process. Results are achieved by measuring the angle of reflection in relation to the angle of incidence that varies depending on material composition and residual stresses.
Advantages In addition to enhancing performance, there are other important benefits from the process.
Compressive stress helps prevent crack formation: The compressive stress helps to prevent crack initiation, as cracks cannot propagate in the compressive environment generated by peening.
Reduced friction: Components which are moving in relation to each other, examples being bolting, riveted assemblies, sliding or rolling members, can wear out and fail as a result of microscopic transfer of material from one surface to the other. The surface finish produced by the peening process provides pockets for lubricant retention; it also reduces the surface area in contact under rolling or sliding conditions, thus reducing friction.
Wear- resistant: Peening also has a surface hardening effect and helps the 'skin' of the material to resist wear. These characteristics when combined provide excellent anti-galling properties, making the components more resistant, work better and provide increased efficiency.
Less corrosion: Inter-granular and stress corrosion cracking can be inhibited by shot peening which modifies the properties of the metal at a metallurgical level. The process advantageously alters the granular structure at and near the surface, producing a condition less prone to corrosion.
An important and complex aspect is the selection of correct equipment and process parameters. Component variables such as size, shape, material, hardness, application and operating environment all have to be considered. The topography of the component is also important. For instance, if a radius is smaller than that of the shot, then it will result in a non-peened area. Sharp edges, blind holes or hidden areas also need special attention to ensure good coverage.
Independent of the type of media propulsion, shot peening requires monitoring and closed loop feedback for critical process parameters such as media velocity and flow. The science of peening rests in all such parameters and close adherence will result in a final product that performs at par or above expectations.
Offerings for surface preparation and treatment In January 2013, during the IFEX, Wheelabrator announced the rebranding of shot blasting and peening products from India. Having proven solutions in all applications is the biggest advantage of this rebranding. The company ensures optimal project costs and continues to bring value- added solutions on a technology transfer mode for its India operations. To date, six products are available for Indian market. Here is a brief on each:
Solutions for the automotive industry The automotive manufacturing and subcontracting sector represents one of the largest users of the shot peening process. Since safety and speed are important aspects in this industry, manufacturers are constantly upgrading their processes and adapting international norms.
To achieve the perfect solutions for the automotive industry, Wheelabrator peening machines incorporates programmable controls and automated component handling systems. These operate in line with pre-set programmes to ensure the precise repeatability of the peening effect, which is essential for volume production.
Wheelabrator is introducing a new product in the market: a multi-table wheel shot peening machine, the DRT. The machine is installed with Roto-jet wheels for standard applications and Saturn HD wheels for heavy- duty applications. The wheel drives are fitted with variable frequency drive (VFD) to ensure that the wheel rotates at a set RPM, controlling the shot impinging velocity of the components. The number of independent rotary tables has to be between six and twelve. The drive used for the table indexing is mounted on top of the machine and the indexing time can be as low as three seconds for 30o rotation. Normally for shot peening, conditioned cut wire shots are preferred. The size of the shots is selected based on the component size, shape and profile that need to be peened. The machine shot recirculation system is fitted with a multi-deck gyro screen for the classification of the shots, allowing only the chosen size of shots for the shot peening needs. The screen normally used is offline and continuously in operation.
The application, engineering and services, play an important role in the peening solution implementation. Hence, the Wheelabrator team has been well trained (including MFA training) for ensuring perfect installation. The machine is always assembled and tested in the Hosakote plant before dispatch.