Laser Ultrasonic Micro-Weld Spot Quality Detection for Complex Parts

The patent replaces the mechanical contact-based metallographic detection system with a laser-based non-contact detection system. The laser ultrasonic wave generation and laser Doppler vibrometer enable quality assessment without physical contact or sample destruction, thereby maintaining measurement precision while dramatically improving productivity through non-destructive and online detection capabilities.

The patent introduces laser ultrasonic waves as an intermediary to indirectly assess welding quality. Instead of directly observing the welding spot morphology through destructive sectioning, the system uses laser-generated ultrasonic waves that propagate through the welded joint, and the resulting vibrations are measured by the laser Doppler vibrometer to infer quality parameters non-destructively.

The patent replaces the contact-based ultrasonic detection system that requires coupling fluid with a fully non-contact laser-based system. The laser generates ultrasonic waves on the surface and the laser Doppler vibrometer detects vibrations optically, eliminating the need for coupling fluid and enabling operation in harsh environments such as high temperatures, vacuum, or where contamination must be avoided.

The patent uses laser beams as intermediaries to transfer energy and information without physical contact. The first laser beam generates ultrasonic waves through photoacoustic effect or thermal expansion, and the second laser beam (detected by laser Doppler vibrometer) measures surface vibrations through Doppler shift, serving as intermediaries that bridge the gap between the detection system and the workpiece without requiring coupling media.

The patent transitions from a static single-axis scanning system to a dynamic multi-axis scanning system. The scanning system incorporates multiple degrees of freedom with independent rotation and translation, allowing the laser beam to dynamically adjust its scanning path in real-time. This enables efficient inspection of complex three-dimensional structures by adapting the scanning trajectory to the workpiece geometry, thereby improving productivity without excessive complexity increase.

The patent extends the scanning system from one-dimensional linear scanning to multi-dimensional scanning by adding rotation and translation axes. This allows the laser beam to access and scan surfaces in three-dimensional space, including complex geometries that cannot be reached by single-axis scanning, thereby significantly improving scanning efficiency and coverage for complex structural components.