MmNi 5 hydrogen storage alloy has been ballmilled with transition metal Co/Ni/Mn/Fe, one at a time in small amount of 0.5, 1.0, 2.0 and 5.0 wt%. Optimum hydrogenation behaviour has been observed for the sample containing 2.0 wt% of transition metal. Maximum hydrogen storage capacities of the MmNi 5 alloy have been obtained as 1.68, 1.64, 1.56 and 1.52 wt%. Time taken for the maximum hydrogen absorption was recorded as 3.0, 4.0, 4.0 and 4.5 min and desorption took 1.9, 3.0, 3.5 and 4.0 min. Short-term cyclic performance has been improved as 98, 98, 97 and 96 % storage capacity retention after 20 cycles upon ball-milling with Co, Ni, Mn and Fe, respectively. The improvement in hydrogenation behaviour due to addition of transition metal has been obtained as Co [ Ni [ Mn [ Fe. Structural and microstructural characterizations have been carried out by XRD and SEM techniques. Several factors have been discussed which affect catalytic action of transition metals in ball-milled MmNi 5 alloy. Keywords MmNi 5 alloy Á ball-milling Á 3d-transition metal Á Catalyst Á XRD Á SEM
In the present work finite element method has been employed to study the interaction of multiple cracks in a finite rectangular plate of unit thickness with cracks on the same side under uniaxial loading conditions. The variation of the stress intensity factor and stress distribution around the crack tip with crack offset distance has been studied. Due to the presence of a neighbouring crack, two types of interactions viz. intensification and shielding effect have been observed. The interaction between the cracks is seen to be dependent on the crack offset distance. It is seen that the presence of a neighbouring crack results in the appearance of mode II stress intensity factor which was otherwise absent for a single edge crack. It can be said that the proximity of cracks is non-desirable for structural integrity. The von-Mises stress for different crack orientations has been computed. Linear elastic analysis of state of stress around the crack tip has also been done.
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