Prediction and control of residual stress-based distortions in the machining of aerospace parts: A review

Distortion of machined parts is a big concern for the aerospace industry. Every year huge amount of capital is lost due to distortions related scrap of components. Prediction and proper control of distortion is thus imperative to avoid huge losses in terms of money and time. Residual-stresses are known as a leading cause of the distortion of aerospace parts. Due to the inherent complex dynamics of the machining process and lack of control of bulk material manufacturing processes, control of these distortions is a challenging task. Several studies have been carried out on the subject however complete control of the process could not be achieved. In this research, previous studies on the issue were reviewed to find out the state of the art and highlight the current limitations of the field. Residual-stress based mechanisms leading to part distortion were identified and state of the art was discussed. It was found that both bulk residual stresses and machining induced residual stresses significantly affect distortions of aerospace parts. These mechanisms act in conjunction to affect the distortion of the parts. For thick parts during roughing operation, redistribution of bulk stresses was found to be the leading cause whereas, machining induced stresses were dominant at finishing stages especially for thin-walled parts. To get complete control of distortions, each of these mechanisms has to be considered at the process planning stage for taking suitable countermeasures. Optimization of toolpath and location of part inside the blank based on bulk residual stresses, optimization of process parameters to control cutting loads and hence machining stresses and, use of adaptive fixtures were identified as the promising control measures for machined part distortions in this review. However, certain challenges have to be overcome before proper application of these measures.