Measurement of micro weld joint position based on magneto-optical imaging

Abstract

In a laser butt joint welding process, it is required that the laser beam focus should be controlled to follow the weld joint path accurately. Small focus wandering off the weld joint may result in insufficient penetration or unacceptable welds. Recognition of joint position offset, which describes the deviation between the laser beam focus and the weld joint, is important for adjusting the laser beam focus and obtaining high quality welds. A new method based on the magneto-optical (MO) imaging is applied to measure the micro weld joint whose gap is less than 0.2 mm. The weldments are excited by an external magnetic field, and an MO sensor based on principle of Faraday magneto effect is used to capture the weld joint images. A sequence of MO images which are tested under different magnetic field intensities and different weld joint widths are acquired. By analyzing the MO image characteristics and extracting the weld joint features, the influence of magnetic field intensity and weld joint width on the MO images and detection of weld joint position is observed and summarized.

Novel inspection of welded joint microstructure using magneto-optical imaging technology

“…According to Eqs. ( 1), ( 7), (9), and (11), θ is proportional to B r , hence θ a > θ b > θ c . Also, according to Eqs.…”

“…[7,8] In this article, a novel magneto-optical (MO) imaging detection method of analysis by Faraday MO effect is proposed and experimented. [9,10] The Faraday MO effect is a phenomenon in which polarization of incident light is rotated to an angle θ under the effect of an external magnetic field. [11,12] The angle θ can be described as…”

Modeling for detecting micro-gap weld based on magneto-optical imaging

“…It also has been certified that MO imaging technology could be used in identifying detection and tracking micro gap weld [13][14][15]. Researches on weld detection show that the centerline of MO transitional zone is the midline of the welding gap, without giving the detailed descriptions.…”