http://nopr.niscpr.res.in/handle/123456789/44439 2026-10-10T22:12:33Z http://nopr.niscpr.res.in/handle/123456789/44451 Title: Structural study and phase transformation of Cu-Al-Ni shape memory alloy produced by severe plastic deformation Authors: Gurau, Carmela; Gurau, Gheorghe; Sampath, V Abstract: Martensitic transformation and mechanical behavior are investigated on extremely brittle Cu-13Al-4Ni shape memory alloy subjected to severe plastic deformation (SPD) by high speed high pressure torsion (HSHPT). The HSHPT process involves high pressure coupled with torsional deformation of the alloy, at which large rotation speed (1795 rpm) of the upper punch generates heat by friction. The experiments are carried out in a Bridgman cell right from room temperature. The disc-shaped Cu-Al-Ni samples produced by this technique have diameter between 20 and 29 mm and thickness until 0.16 mm, depending on the extent of deformation. Microstructural analyses are performed on the alloy that had undergone processing by optical, scanning electron as well as transmission electron microscopy. The microstructural investigations show that increasing the degree of deformation leads to gradual grain refinement. The microstructural changes are correlated with the Vickers hardness of the alloy. The alloy processed by HSHPT shows reversible martensitic transformation without the necessity for post-deformation annealing and phase transformation stability after 10 thermal cycles, too. Page(s): 5-10 2018-02-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/44450 Title: Effect of process parameters on the mechanical performance of resistance spot welded joints of AISI 409M ferritic stainless steel Authors: Subrammanian, A; Senthiil, P V; Jabaraj, D B; Jayaprakash, J Abstract: In this study, the effect of process parameters on mechanical performance of the resistance spot welded joints of AISI 409M ferritic stainless steel sheets is investigated. Mechanical performance of the spot weld is evaluated in terms of output quality characteristics, such as load carrying capacity and energy absorption capacity. Important process variables, such as current, time, electrode force and holding time were varied separately and corresponding output parameters, which decide the mechanical performance of the spot welded joint have been analysed. Weld nugget geometrical parameters such as nugget size and surface indentation have also been analysed with respect to various process variables. It has been found that peak load and energy absorption capacity are in direct relationship with welding current as well as welding time, in expulsion free welds. Surface indentation increases with increase in current and welding time. It has also been observed that increasing electrode force results in slight reduction of both tensile shear strength and energy absorption capacity. The effect of holding time on mechanical performance of the resistance spot welded joint is found to be almost insignificant. Regression-based relations are developed to correlate the mechanical performance of the spot welds with nugget size. Page(s): 11-18 2018-02-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/44449 Title: Loading effect on friction behavior of ordered/disordered graphite in ambient and inert condition Authors: Das, Pankaj Kumar; Kumar, N; Chakraborti, Prasun Abstract: Load dependent friction behavior of structurally ordered and disordered graphite is measured in ambient and nitrogen gas atmosphere. Friction coefficient is significantly less in graphite in order as compared to disorder in ambient atmosphere. This behavior is attributed to structural defects in graphite lattice. However, under nitrogen gas, friction coefficient graphite is significantly high irrespective of structural order or disorder of graphite. This typical behavior is mainly attributed by chemical reactivity of graphite surface which is high in nitrogen gas and not much influenced by structural ordering/disordering. In both types of graphite, steep increase in friction coefficient is observed at high load. This is explained by reasonable increase in contact area and followed by the Johnson−Kendall−Roberts (JKR) model. Page(s): 19-25 2018-02-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/44448 Title: Microstructural and mechanical properties of friction stir welded pure lead Authors: Günen, A; Kanca, E; Demir, M; Çavdar, F; Mistikoğlu, S; Çam, G Abstract: The present study focuses on the applicability of friction stir welding to pure Pb plates. The joint performances are evaluated by optical microscopy, microhardness measurements, notch impact tests and three point bending tests. The effects of the tool rotational speed (1500, 2000 and 2500 rev/min) and welding speed (72, 100 and 125 mm/min) on the joint performance are determined. The results indicate that the welded joints exhibit similar or higher mechanical properties than those of the base material. Optimal joint performance was achieved with a rotational speed of 1500 rev/min and welding speed of 100 mm/min. Page(s): 26-32 2018-02-01T00:00:00Z