No abstract

No abstract

No abstract

In this paper, the micro-damage mechanisms of 5A06 Al alloy weld joints have been studied under the condition of constant load and cyclic thermal load. The mechanical performance variation of the base material and its weld joint are analyzed and compared. Microstructure analysis reveals that the main damage mechanism in weld joints is the interior voids nucleation and growth. The voids distribution and evolution govern the damage process. Test results also show most fractures occur at HAZ near the welding fusion line. The development of these voids results in the performance deterioration of the weld joints under thermal cycling condition.

The ambiguity problem of determining whether the detected particle is in the front or rear of the focal plane has long been an important issue that hinders the development of the single-camera three-dimensional defocus particle tracking velocimetry (PTV). This study proposes a method to obtain the true position based on the feature of the defocus image’s asymmetry with respect to the focal plane. Specifically, two ambiguity positions with the same width of point spread function (PSF) are distinguished by introducing the parameter calculated from the maximum gradient of image gray. The math expression of half wide (χ) in PSF considering aberration used for this method is derived. The reliability of this method is evaluated by applying a calibration technique, and the result shows that 11 events obtain correct results in the 12 experiment conditions. The accuracy of this method is tested by measuring 3D velocity of an airflow jet with 3D-PTV compared with the computational fluid dynamics (CFD) result, which has the maximum error of 3.1%. Finally, the 3D-PTV is applied to a real spray as a measurement example, the 3D vector map and velocity cumulative distribution of the measured area are obtained.