Method of online stress measurement residual during laser additive manufacturing

A real-time FEM model building method comprising:

• dividing a CCD recorded video into a plurality of frames;
• dividing a cladded layer into the same number of sections as the plurality of frames;
• assuming the shape of each section as a half circle;
• forming a meshed rectangular area on ⅓ of the radius of the half circle at a core area of the section;
• dividing the half circle into m segments with an equal angle such that there is m+1 points along the half circle, each point on the half circle has a corresponding point on the edge of the meshed rectangular area;
• forming m+1 lines between the points to create nodes along these lines in clockwise, connect nodes in each section and create elements of a clad layer;
• and
• creating the FEM model of the substrate according to a random edge of the clad layer to guarantee a convergent calculation by dividing into five parts including a bottom, a front, a back, a left, and a right.

A real time stress calculation method comprising:

• initially completing the following steps:
• determining a length of clad layer according to a position of a line laser by calculating when the line laser have traveled a certain distance and building a shape of the clad layer according to a height of a molten pool;
• defining the height of the molten pool as an original state and a height of solidified material as an energy released state;
• calculating a displacement of the surface of the molten pool and the surface of the solidified material;
• applying the displacement of the surface into a model and calculating the stress generate during deformation;
• and
• repeating the above steps and comparing a second calculated stress to the first calculated stress of the previous iteration of steps.

A real time monitoring device comprising:

• a first CCD camera mounted on the hollow shaft stepping motor;
• a second CCD camera mounted on the hollow shaft stepping motor;
• a neutral density filter and a light filter mounted to at least one of the first CCD camera and the second CCD camera
• a hollow shaft stepping motor;
• a line laser mounted on the hollow shaft stepping motor and in line with the first CCD camera;
• and
• at least one of the first CCD camera and the second CCD camera being perpendicular to the line laser,
• wherein the hollow shaft stepping motor is configured to continually adjust the position of the line laser, the first CCD camera, and the second CCD camera to keep the line laser and at least one of the first CCD camera and the second CCD camera parallel to a laser scan direction.