Luo Zhongbing

Focal law design for phased array ultrasonic testing of CFRP based on finite element modeling

The focal law of linear phased array ultrasonic testing of carbon fiber reinforced plastic (CFRP) laminates was studied based on finite element modeling. Two stacking sequences, [0]40 and [45/90/-45/0]10, were considered and the focusing results were compared based on the calculation of transient acoustic field. It was found that the actual focal point was ahead of the preset location when the focal law was calculated with a constant velocity of 2980 m/s, and the focal depth of [0]40 laminate was much smaller than that of [45/90/−45/0]10. To realize the focal law design, the time delay from each element to the preset focal point was acquired based on the finite element simulation and the focusing was obviously improved. The results were also verified by experiments. The differences were comprehensively discussed based on the wave propagation behavior in the elastic anisotropy and laminar structure.

Tensile Behavior of Sn-0.7Cu with Zn addition at Various Deformation Temperatures

The tensile behavior of Sn-0.7Cu and Sn-0.7Cu-1Zn was compared at various deformation temperatures. Refined microstructure and γ-CuZn particles were discovered with Zn addition. The strengths of Zn-containing solder were higher than that of Sn-0.7Cu at room and subzero temperatures. With the elevation of deformation temperature, they both decreased and they were nearly the same at 80 ◦C. The works of fracture exhibited the similar evolution law. For Sn-0.7Cu solder, the elongation after fracture was smaller and the reduction of area was bigger than those of Sn-0.7Cu-1Zn. This shows that Zn addition improved the deformation stability, which is attributed to the modification of the microstructure. Dimples in fracture surface became smaller and shallower with the decreasing temperature. Ductile fracture was discovered in all the samples.