New directions for inline inspection of automobile laser welds using non-destructive testing

An innovative pilot installation and eddy current testing (ECT) inspection system for laser-brazed joints is presented. The proposed system detects both surface and sub-surface welding defects operating autonomously and integrated with a robotized arm. Customized eddy current probes were designed and experimentally validated detecting pore defects with 0.13 mm diameter and sub-surface defects buried 1 mm deep. The integration of the system and the manufacturing process towards an Industry 4.0 quality control paradigm is also discussed.

Investigation of the Wear Behavior of Surface Welding AZ91 and AZ91+Gd Alloys under Variable Loading Conditions

Adding rare earth elements to magnesium alloys is an effective way to improve their wear resistance. However, the effect achieved is closely related to the friction condition. In this paper, two different types of welding wires, AZ91 magnesium alloy and AZ91 + gadolinium (Gd), were used for surface welding. Dry sliding friction and wear experiments were performed on the surfacing alloys using the pin-on-disc test. The effects of Gd addition on the wear resistance and wear mechanism of the alloy were systematically studied under low to high loads. The results show that as the load increases, the friction coefficient of the surfacing AZ91 alloy gradually decreases as the wear rate increases. A mild–severe wear transition occurred at 100 N. The addition of Gd only slightly increased the wear rate under a load of 15 N. The wear rate was significantly decreased with loads in the range of 30 to 100 N and mild–severe wear transition was avoided. The influence of both Gd addition and load on the wear mechanism were considered. The overall wear resistance of the surfacing magnesium alloy was determined.

An Example of Reparatory Surface Welding of the Mining Machine Vital Part

Mining machines' components, or the whole structure, are prone to frequent premature damages and fractures what is explained either by inadequate design and construction or by insufficient knowledge of the material's and welded joints' properties and oversights in manufacturing. Here is considered the bucket-wheel excavator, i.e. the fracture of the tooth of the girth gear, which enables the circular motion of the excavator's upper structure (which was in operation for 5000 hours). The gear was made of the cast steel GS 40 MnCrSi3 V. The reparatory hard-facing (HF) technology of the fractured tooth required specification of numerous operations including the preparation works. The reparation realized the two-fold savings, in time and money - the new girth gear costs over 500 000 € and its manufacturing lasts 6 to 9 months, while the safety and quality of the repaired tooth was guaranteed.

On the Surface Welding of Pearlitic Rails: The Control of Dilution and Microstructure

This work studies the surface welding parameters for a practical repair for pearlitic rail grades: R260 and R350HT. A filler metal containing low carbon (0.15 %), high silicon (0.5 %) and nickel (2.5 %), self-shielded flux-core welding electrode (FCAW-S) is the candidate in order to ensure the preferable carbide-free bainite. The film-like morphology of the retained austenite is reported to promote the wear resistance and is ensured by silicon and nickel. The effect of preheat temperature and dilution on the microstructure and resulting hardness can be concluded. Too high dilution, as a result of high current and travel speed, and the reheating during the welding of the second layer can result in martensite formation and too high hardness. Proper control of the dilution ensures satisfactorily hardness and avoids martensite formation.

Analysis of typical working conditions and experimental research of friction stir welding robot for aerospace applications

In an attempt to address the limitations of single function and the poor process flexibility of existing friction stir welding equipment, a new friction stir welding robot has been developed to address practical problems in three-dimensional surface welding. Based on an analysis of the components of the robotic system, a kinematics model was established, and the forward and backward kinematics solutions were derived for the robot. An iterative nearest point algorithm, iterative closest point based on point cloud matching, was used to plan the welding trajectory for the most complex petal welding conditions, and an experimental study was conducted. The results show that the kinematic and dynamic test results were consistent with the acquired simulation curves for specific sizes of the rocket cap flaps under appropriate welding conditions. The normal error of the weld was less than 85 µm, the average tensile strength was 359 MPa, and the elongation was 7.20%, 78.0%, and 72.0% of 2A14-T6 aluminum alloy. The friction stir welding robot exhibited robust performance, and the proposed trajectory planning method is practical and effective. The appearance, geometric dimension, and mechanical properties of the weld achieved the expected criteria, and high-precision welding of large complex thin-walled surfaces is possible.