Modeling of Part Distortion in Components Machined From Plates and Forgings

Machined monolithic components provide the foundation for modern aircraft structures requiring high performance designs in terms of weight, strength and fatigue properties. Part distortion and warpage arising from bulk material and machining-induced stresses frustrates manufacturing and assembly processes and necessitates expensive trial-and-error methods, shot peening and heat treating to minimize distortion. Strict weight requirements are exacerbated by thicker component section designs as a distortion control mechanism.

We present a physics-based model that takes into account the pre-machined bulk stress state and machining-induced stresses for monolithic parts. Sources of stresses include heat treatment, quenching, forging, cold working and machining operations. A customized solid model representation of the initial workpiece geometry is developed, and bulk stresses are mapped onto the solid model. Computer numerical control (CNC) toolpath programs, along with corresponding tooling geometry, are read and analyzed. Bulk stresses are removed from the component as material is machined away, while machining-induced stresses are applied to the final surfaces. The final workpiece geometry is meshed automatically with finite elements and equilibrium solutions calculated. Minimum distortion configurations and strategies are analyzed. Distortion prediction, measurement and validation are presented for a number of monolithic, thin-walled components. Challenges and approaches for accurate and timely simulation are discussed.