Sambit Kumar Parida

This paper presents Three-Dimensional (3-D) non-linear Finite Element (FE) analyses to assess the structural behaviour of curved laminated Fibre Reinforced Plastic (FRP) composite panel-based Single Lap Joints (SLJs) with Functionally Graded Adhesive (FGA) featuring pre-embedded adhesion failure. The principle of the fracture mechanics concept is used to investigate the behaviour of interfacial stresses (peel and shear stresses) along the adhesion failure fronts at critical locations. Corresponding three modes of Strain Energy Release Rates (SERRs) are considered as the damage growth parameters and are evaluated using Linear Elastic Fracture Mechanics (LEFM) based Virtual Crack Closure Technique (VCCT). Based on the stress analyses, it has been observed that the adhesion failure in the SLJ structure triggers at the interface between the adhesive and the lap adherend. Depending on the SERR magnitudes, it has been observed that interfacial damage propagates under mixed-mode conditions. As a result, the controlling parameter for damage propagation is total SERR (GT). Furthermore, instead of using a homogenous adhesive substance, FGA has been used to slow down the rate of damage progression. One of the most significant benefits of FGAs over homogeneous adhesives is that the material properties change continuously in the desired direction from point to point, although these materials are microscopically inhomogeneous. FGA bonded joints have a continuous change in the adhesive properties throughout the bonded region, allowing for the homogeneity of stress distribution and load transmission to increase the load-carrying capacity. Series of numerical simulations have been performed using different kinds of FGAs, like unidirectional (1D) and bidirectional (2D), with appropriate function profile in order to achieve significant minimization interfacial stresses and SERRs. Material gradation of adhesive indicates significant interfacial stresses and SERRs reduction at the incipient stage of failure, which necessitates the use of FGA for SLJ and prolongs the service life of the structure.

Titanium metal matrix composite (Ti6Al4V+ZrO2+B4C) coatings are fabricated with varying contents of B4C on Ti6Al4V plate by laser cladding. The effect of B4C contents on the microstructure and wear behaviour of the claddings were investigated. Results indicate that the crack-free coating is possible with strong bonding with the substrate material. The in-situ synthesised hard phases, such as TiB2, TiC, ZrB2­, etc., are developed in the cladding. Microstructure of the claddings changes with the change of contents of wt.% of B4C in the composite. A black willow-shaped structure (TiB2) is observed in sample BM3 (30 wt.% of B4C) dispersed uniformly in a grey cellular dendrites (TiC) matrix. In addition, ZrB2 formation is also increased with an increase in the wt.% of B4C. It is found that the average microhardness (1383.075 HV300) and coefficient of friction (0.15-0.25) of the claddings increase with the increase of B4C contents, whereas the weight loss of the cladding samples in dry sliding wear decreases with increasing the B4C content. The claddings show good erosion resistance at ambient and at 750 oC. The addition of B4C in the titanium MMC increases the hardness and wear resistance of the cladding by the in-situ development of hard compounds.

The aim of this research is to design and to develop a computer controlled low-cost underwater welding setup for shielded metal arc welding (SMAW) process to work in dry as well as in wet welding conditions. Investigations of the microstructure and mechanical properties of the welded joints made from AISI 1010 steel plates using this setup, in air, tap water, and saltwater working environment, respectively, have been carried out. Weld bead geometry, microstructure, ultimate tensile strength (UTS), ductility, impact strength and Vickers microhardness of air and wet welded joints have been characterized and compared. The general weld bead size is quite dissimilar for air, tap water and salt water welded joints. The tap water and salt water welds seem to be wider with a slightly higher weld penetration with lower reinforcement. The maximum value of the the average UTS of the welded sample as per ASTM was 485.74 MPa. The experiments showed that the maximum percentage of elongation of samples welded in different conditions is 8.06 % and the maximum value of the average impact strength of 25.64 J was found in case of air welds. The microhardness value of fusion zone (FZ) was greater than base metal (BM) in all the welded samples. It was noted maximum up to 310.8 HV10 at coarse grain heat affected zone (CGHAZ) of tap water welds. The mechanical properties of the salt water welds deteriorated due to porosity, slag inclusion, undercut, increase in hydrogen and oxygen content in the welds.