T S Srivatsan
Articles written in Sadhana
Volume 33 Issue 3 June 2008 pp 175-179
Volume 33 Issue 3 June 2008 pp 235-250
In this technical paper, the microstructure, hardness, tensile deformation and ﬁnal fracture behaviour of an emerging titanium alloy for performance-critical applications are presented and discussed. Both longitudinal and transverse test specimens were prepared from the as-provided sheet stock of the alloy and deformed in uniaxial tension. The yield strength and tensile strength of the alloy sheet in the transverse orientation was higher than the longitudinal orientation. The ductility of the test specimens, quantiﬁed in terms of reduction-in-cross-sectional area, was higher for the transverse specimen when compared to the longitudinal counterpart. The elongation-to-failure of the test specimens was identical in the two orientations of the sheet stock. The tensile fracture behaviour of the alloy was quantiﬁed by careful examination of the fracture surfaces in a scanning electron microscope. The intrinsic fracture features on the tensile fracture surface were discussed taking into consideration the nature of loading and contribution from intrinsic microstructural features.
Volume 33 Issue 3 June 2008 pp 251-259
This paper highlights the interfacial structure of tin-silver (Sn-3·5Ag) solder on nickel-coated copper pads during aging performance studies at a temperature of 150°C for up to 96 h. Experimental results revealed the as-solidiﬁed solder bump made from using the lead-free solder (Sn-3·5Ag) exhibited or showed a thin layer of the tin–nickel–copper intermetallic compound (IMC) at the solder/substrate interface. This includes a sub-layer having a planar structure immediately adjacent to the Ni-coating and a blocky structure on the inside of the solder. Aging performance studies revealed the thickness of both the IMC layer and the sub-layer, having a planar structure, to increase with an increase in aging time. The observed increase was essentially non-linear. Fine microscopic cracks were observed to occur at the interfaces of the planar sub-layer and the block sub-layer.
Volume 33 Issue 3 June 2008 pp 261-272
The intrinsic advantages of strengthening the steel-based structures by the use of ﬁbre reinforced plastic (FRP) material have not yet been fully exploited. In this paper, a succinct overview of recent studies made to enhance the strength of steel beams using FRP laminates is presented. The results presented and discussed in this paper were obtained by closely studying the behaviour of steel beams strengthened with carbon FRP material. An attempt is made to succinctly summarise the ﬁndings for two different types of strengthening of the steel beams using carbon FRP laminates. The ﬁrst type of beams focuses on enhancing the strength of steel in ﬂexure while the second focuses on increasing the shear strength of the beams. Three beams were designed so as to cause them to fail in ﬂexure. Of the beams studied, two were strengthened using carbon FRP strips attached to the tension ﬂange. One of the beams was tested to facilitate comparison of their behaviour to the two beams which are strengthened in ﬂexure. Three other beams were designed such that they failed predominantly in shear. Of these three, two were strengthened with carbon FRP strips attached to the webs while the third beam was used as a control beam for the purpose of drawing comparisons. Preliminary results revealed a noticeable increase in the strength for both the ﬂexure strengthened beams and the beams strengthened in shear. The observed increase in shear strength of the beams was 26% while the increase in strength for the beams tested in ﬂexure was 15%. This study convincingly shows that it is possible to strengthen steel beams using carbon FRP laminates in both ﬂexure and in shear.