Sn 3.0 Ag 3.0 Bi 3.0 In (SABI333) solder is easy to form solder joints with different crystal structures during solidification. Solder joints with different crystal structures can exhibit different failure behaviors during creep. Five kinds of SABI333 solder joints with different crystal structures were selected to study the effect of grain boundary on the failure behavior of creep. The scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD) were utilized to characterize the surface morphologies and crystal orientations of solder joints. When there were only low angle grain boundaries or twin boundaries in the solder joints, it was not easy to generate cracks inside the solder joints during creep but easy to generate cracks at the interfaces between the copper bars and solder matrices. However, when there were high angle grain boundaries greater than 70° in the solder joints, the cracks would propagate along such grain boundaries during creep. This phenomenon depends on the difference of grain boundary energy and the difference of deformation degrees of grains on both sides of grain boundaries during creep. The grain boundary energy of the high angle grain boundaries is relatively high and the deformation degrees of grains on both sides of high angle grain boundaries are quite different during creep. This research is conducive to further understand the creep failure behavior of SABI333 solder joints under the service environment.

This study aims to clarify the flow characteristics and wake structure of convertible vehicles. Numerical simulations are performed to obtain a preliminary visualization, and the potential vortical motion characteristics are investigated by examining the Q-criterion across multiple cross-sections. Comparisons between numerical and experimental results validate the reasonableness of our numerical model. The predominant wake topology of a two-seat convertible is obtained in terms of the location, shape, and spin direction of the vortices. We observe a "nook" vortex that is triggered by the flow acceleration induced by the pressure gradient near the windshield step, provoking undesirable aeroacoustic noise and degrading the cabin comfort. Complicated A-pillar vortex dynamics are revealed, with small vortices that are shed into the cabin and impinge the seats, eventually forming a long tail structure above the back of the vehicle. Moreover, periodic fluctuations of the windshield vortex are induced by the Kelvin-Helmholtz instability, significant impacting the streamwise wake. Ultimately, the combined motion characteristics of the A-pillar and windshield vortices exert undesirable effects on the aeroacoustic noise and drag, suggesting fundamental mechanisms for achieving optimal energy-saving and acoustic convertibles in the future. Based on the wake topology and the vortical generating mechanism, approaches are proposed to reduce the drag and aeroacoustic noise by impeding the flow over the door into the cabin and modifying the shape of windshield step, and lengthening the windshield in stream direction.

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