Jinsong Zhang

A New Self-Piercing Riveting Process and Strength Evaluation

Self-piercing riveting (SPR) has become an important alternative joining technique for the automotive applications of aluminum sheets. Most existing SPR machines use electrical motors to drive a rivet into the sheets. A significant amount of research has been conducted to improve an SPR joints strength by increasing the mechanical interlock. In this paper, a new process is presented using gunpowder to drive the riveting process. A joint formed using the new process has different geometric characteristics from one created using a conventional system. The tensile-shear; cross-tension, fatigue, and impact performances of self-piercing riveted joints using the new device are compared to those of spot-welded joints on aluminum sheets. The experiment has proven that the new SPR joints have provided a similar or higher strength than resistance spot welds.

Numerical predictions for radar absorbing silicon carbide foams using a finite integration technique with a perfect boundary approximation

Modeling and prediction of electromagnetic wave absorbing properties of SiC foams as novel stealth materials in the X-band range of 8.2-12.4 GHz are presented. Appropriate material parameters, including the conductivity, volume fraction, cell size, thickness, and surface modified foam structure, are determined through optimization calculations, where the impedance difference between the SiC foam and free space is minimized. The minimum reflection coefficient, reaching -8 dB, is obtained when the SiC conductivity is about 2.27 S m(-1), the volume fraction is 28%, and the thickness is 20 mm in the case of SiC foam. For surface modified foam, the reflection can be less than -10 dB throughout the entire band investigated.

A Novel SiC Foam Valve Tray for Distillation Columns

The novel SiC foam valve tray was made of thin slices of SiC foam material with a high specific surface area. Hydrodynamic performances of the novel SiC foam valve tray were studied with air-water system at atmospheric pressure. These performance parameters included pressure drop, entrainment, weeping and clear liquid height. The mass transfer efficiency of the SiC foam valve tray was measured in laboratory plate column. Compared with the F1 float valve tray, the dry pressure drop was decreased about 25%, the entrainment rate was about 70% lower at high gas load, the weeping was much better, and the mass transfer efficiency was far higher. Thus, the overall performance of the novel SiC foam valve tray was better than that of F1 float valve tray.