We can assume that, in this state, the stress has not formed yet and can take this state as a stress-free state.
In the actual manufacturing process, the shape of the state B is contracting to state A due to the cooling of the melt pool.
The results show that there is no obvious shape change after solidification.
The shape of the melt pool and its solid state is similar.
This method has broad applications for the repairing, cladding and manufacturing of engineering components and artistic pieces.
However, due to the complicated thermal history of laser-based AM processes, uneven thermal contraction and expansion occur, which generate a massive amount of residual stress inside the solidified material.Based on computer vision and FEM analysis, this method can make a quick prediction of the stress generated during the laser deposition process. B is the shape of the molten pool when it just forms.At this time, the material is in a liquid state; although it contains certain forces and stresses in it, such properties are negligible compared to those of the solid state.To filter out the light of plasma and 532 nm laser, a 650 nm filter is mounted in front of camera 2.Both cameras are Micro-Mac ® 8SG, 60 fps, and the shutter in camera 1 was set to 1/500 seconds.Currently, the most common methods are simulation and postmortem stress examination.The numerical simulation begins with pure temperature calculation, through 2D to 3D models added solidification phase changes to the model to make the result more closely resemble the experimental data. Moat uses X-ray diffraction to measure the residual stress in Co-based laser clad layers.However, this method cannot directly reflect the real condition inside the deposition layer. Biegler applied digital image correlation (DIC) technology to measure the distortion on the substrate.This method must spray a cover layer on the target area, which makes it easier to detect the distortion.Due to the stress superposition principle, the stress in state A can be expressed as: According to the hypothesis, σ (B) is 0 and σ (A) ≈ σ (C).Based on our hypotheses, the stress development can be calculated through the difference between the surface of the melt pool and the solidified material. The melt pool height is recorded by a camera that is set perpendicular to the manufacturing laser.