Korea Advanced Institute of Science and Technology

Peipei Liu

Hoon Sohn

Ikgeun Jeon

Hyung Jin Lim

Jinho Jang

Su Young Yang

Disclosed are a method of inspecting a printing quality of a 3D printing object using a femtosecond laser beam during a 3D printing process, and an apparatus and a 3D printing system for the same. A laser beam is irradiated from a femtosecond laser source disposed coaxially with a 3D printing laser source to inspect a state of the printing object. The laser beam generated by the femtosecond laser source is separated into a pump laser beam and a probe laser beam. The printing laser beam irradiated from a 3D printing laser source or the pump laser beam is irradiated onto a printing object to generate ultrasonic waves. To measure the ultrasonic waves, a probe laser beam is irradiated onto the printing object. The probe laser beam reflected by the printing object is detected. The quality of the printing object is inspected by analyzing the reflected probe laser beam.

Method of inspecting printing quality of 3D printing object using femtosecond laser beam during 3D printing process, and apparatus and 3D printing system for the same

Disclosed are a femtosecond laser-based ultrasonic measuring apparatus for a 3D printing process, and a 3D printing system including the apparatus. The apparatus includes a femtosecond laser source for generating a femtosecond laser beam irradiated to inspect a state of a printing object formed by melting a base material by a printing laser beam irradiated from the laser source for 3D printing, a beam splitter for separating the femtosecond laser beam generated by the femtosecond laser source into a pump laser beam and a probe laser beam, an electric/acoustic optical modulator for modulating the pump laser beam, a time delay unit for delaying the probe laser beam, a photo detector for detecting the probe laser beam reflected by the printing object, and a lock-in amplifier for detect an amplitude and a phase of the output signal from the photo detector. The femtosecond laser source is disposed coaxially with a laser source for 3D printing.

Femtosecond laser-based ultrasonic measuring apparatus for 3D printing process and 3D printing system having the same

A method of feedback controlling a 3D printing process in real time, and a system therefor are disclosed. The method includes collecting big data, generated through 3D printing experiments, related to process variables of 3D printing, measurement signals, and 3D printing quality of the 3D printing object; building an artificial neural network model by performing machine-learning based on the collected big data; evaluating whether or not a 3D printing quality of the 3D printing object is abnormal in real time based on an actual measurement signal of the 3D printing object and the artificial neural network model; and feedback controlling printing quality of the 3D printing object in real time based on the evaluation result of whether or not the 3D printing quality of the 3D printing object is abnormal.

Method of feedback controlling 3D printing process in real-time and 3D printing system for the same

In a method of inspecting a structure, a first ultrasonic signal generated from a target structure by a first laser beam is received. The first ultrasonic signal is generated by providing the first laser beam generated from a first excitation unit to the target structure. A second ultrasonic signal generated from the target structure by a second laser beam different from the first laser beam is received. The second ultrasonic signal is generated by providing the second laser beam generated from a second excitation unit to the target structure. A third ultrasonic signal generated from the target structure by the first and second laser beams is received. The third ultrasonic signal is generated by simultaneously providing the first and second laser beams to the target structure. It is determined whether the target structure is damaged based on first, second and third ultrasonic frequency spectra that are obtained by converting the first, second and third ultrasonic signals, respectively.

Method of inspecting structure and inspection system

The present invention relates to a safety diagnosis method for a structure using a nonlinear ultrasonic wave modulation technique. The safety diagnosis method includes: making the structure vibrate by applying signals of different ultrasonic frequencies; converting the responses of the structure generated by the vibration into digital signals; extracting first modulation signals by subtracting the harmonic responses and the linear responses of the signals of different ultrasonic frequencies from the digital signals and synchronously demodulating the digital signals; constructing a first sideband spectrogram by combining the first modulation signals generated by continuously changing at least frequency among the signals of different ultrasonic frequencies; and deciding whether the structure is cracked based on the first sideband spectrogram. Even though the power of the ultrasonic wave applied to the structure is very small as compared with the related art, whether there is the damage is precisely decided, and thus power consumption may be reduced.

Growing community of inventors

Daejeon, South Korea

Peipei Liu