Punching Shear Behavior of RC Flat Slabs Strengthened with Steel Shear Bolts

This paper aims to determine the efficiency of using steel Shear Bolts to strengthen RC slabs in punching shear at interior columns. The Shear Bolts used in this study consists of a vertical rod and anchored from both ends using a washer and nut system. Shear Bolts are installed in holes, drilled in concentric perimeters around column, after casting and just before testing. In this Work, an experimental research program was described in which seven halfscale models representing interior slab column connections were tested. Seven square specimens (2000 x 2000 x 150 mm) were divided into two groups. The first group deals with three specimens with square column 150 x 150 mm; one specimen without strengthening as a control specimen and the other two specimens strengthened with shear bolts with different strengthened length around the column. The second group deals with four specimens with rectangular column 150 x 300 mm; one Specimen without strengthening and the other three specimens strengthened with Shear Bolts with different strengthened length and arrangements around the column. All Specimens were loaded until failure. The ultimate load, deformation, punching perimeter, strain in flexural reinforcing bars, strains in Shear Bolts, and the failure mechanisms of each specimen were generated and analyzed. The load-deflection curves are presented which show how Shear Bolts increases punching shear capacity and post failure ductility of slab-column connections

Solder Joint Ductility

Solder joint arrays were tested under tensile loading to determine the strain-to-failure (ductility) under a wide range of conditions. The trends in ductility with alloy, joint size, pad metallization, and test conditions were quantified and discussed. 63Sn37Pb solder joints showed a significant increase in ductility as applied stress is reduced below 40MPa. Lead free alloy ductility was much less sensitive to applied stress level. Hence, at low stress levels, eutectic SnPb has greater ductility than the lead free alloys. Larger joints showed greater ductility in a constant crosshead rate test compared to smaller joints. This is believed to be a function of the load train stiffness. Such a discrepancy was not observed in the constant load test method.

Paradox of Strength and Ductility in Metals Processed Bysevere Plastic Deformation

It is well known that plastic deformation induced by conventional forming methodssuch as rolling, drawing or extrusion can significantly increase the strength of metalsHowever, this increase is usually accompanied by a loss of ductility. For example, Fig.1 shows that with increasing plastic deformation, the yield strength of Cu and Almonotonically increases while their elongation to failure (ductility) decreases. Thesame trend is also true for other metals and alloys. Here we report an extraordinarycombination of high strength and high ductility produced in metals subject to severeplastic deformation (SPD). We believe that this unusual mechanical behavior is causedby the unique nanostructures generated by SPD processing. The combination ofultrafine grain size and high-density dislocations appears to enable deformation by newmechanisms. This work demonstrates the possibility of tailoring the microstructures ofmetals and alloys by SPD to obtain both high strength and high ductility. Materialswith such desirable mechanical properties are very attractive for advanced structuralapplications.