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Abstract

A system and method for monitoring and controlling in real-time the development of residual stress accumulation in a product during its fabrication by a laser-aided, computer-controlled, direct material deposition process. The system includes a laser source, a laser controller and a numerical controller. The material is deposited on a substrate which is equipped with strain gages on its back surface, i.e. the surface opposite to the surface on which material is deposited. The strain gages measure real-time changes in chosen locations and directions, typically in two orthogonal directions along and across the deposition direction. Acoustic and optical sensors are also mounted on locations appropriate for measurement. The strain gage, acoustic sensor and optical sensor measurements are sent to a computer with a stress analysis software package, which uses the strain data as an input to calculate the stress accumulation. The computer is programmed to determine whether critical conditions, such as a pre-determined fraction of the yield strength are reached at any location. Based on this information, the computer sounds a warning signal, or directs a command to the laser controller to adjust the parameters of the laser beam or the laser process, or directs the laser numerical controller to discontinue the process.

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First Claim