Investigations on formability of NiTi complicated shape memory alloy structures using laser forming techniques

Abstract

Laser forming is an advanced manufacturing which is widely used in automotive and manufacturing industry by deforming metallic and non-metallic sheets. In this process, a continuous fiber laser is irradiated over Ni-Ti sheet. As the laser beam imbibed over the sheet, a step temperature thermal gradient got induced across the thickness of the sheet. The bending moments due to uneven thermal stresses leads to the deformation of the sheet without using any external forces. Shape memory alloy (SMA) is a class of smart material which is known for two distinct properties such as super elasticity (SE) and thermal shape memory effect (SME). SMAs have the ability to achieve high deformation and return to a certain predefined shape upon unloading or after heating above a certain temperature. SME refers to the phenomena where the SMA will automatically come to its original position after heating and SE is the effect where SMAs may undergo huge non-linear deformation and comes back to its original shape upon unloading. Due to these amusing properties SMAs have found various applications in the region of industrial sector such as for making fasteners, coupling, actuators,etc. This Thesis shows the experiments performed on Ni-Ti sheets of dimension 50mm×200mm with a maximum power of 35W. The process parameters which were varied are Power (25W to 35W), Scan Speed (40 to 75) to get the required profile with a uniform spot diameter of 2mm. The study between variations of the bending angle with process parameters is done. After this the characterization of the samples was done using differential scanning calorimeter (DSC), XRD, SEM for the changes in phase transformation of Ni-Ti SMA with respect to change in power and Scan Speed isstudied.