Generic Almen Fixtures for Intensity Measurement in Shot Peening

摘要

With the introduction of new materials, more complex shapes and stringent requirements in aerospace components, it is obvious that intensity measurements techniques have to be adapted to the new generations of CNC/Robotic shot peening equipment. Those new machines have greater control on the process oriented variables and are moving from non-precise and poorly controlled machines to precision oriented equipment when the proper programming techniques are used. The implementation of offline programming allows greater consistency on the application of the shot stream, which should allow us to step away from simulative Almen fixtures as long as the limitations mentioned before are considered. The next step is to verify if the machine can keep all intensity influent parameters constant in the work envelope. This step is being developed in a validation plan which will be aimed at verifying the influence of the motion and position of the blast gun (which changes the blast hose radiuses, position and vertical length) on media flow and air pressure. To follow the aerospace industrys highly developed technology, the generic Almen fixture is only one of the steps that have to be made toward the replacement of the Almen technique by shot velocity sensors or other measurement devices. This could lead to development and acceptance of closed loop intensity control systems implemented in shot peening equipment. CNC/robotic machines have many advantages in application of shot peening, especially in aerospace applications. The only downside of the new generations of shot peening machines is that the actual specifications are not yet fully adapted to a high level or process control, by requiring testing and validation to be performed according to old technology and poorly controlled techniques. The use of generic Almen fixture is one of the ways that can lead to a more efficient use of CNC/robotic shot peening equipment while still complying to the main specifications requirements. As more testing is performed, the concept will be refined to enhance efficiency and quality of results during production and process settings.