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This paper presents a methodology for designing prismatic springs of non-circular coil shape and non-prismatic springs of circular coil shape using analytical and numerical methods. To start with, simple analytical formulations for obtaining the axial deformation of the springs under axial load have been demonstrated. Next, the processes of obtaining CAD models of the springs and their subsequent finite element analysis (FEA) in commercial softwares have been outlined. In the third part, the different springs have been compared with a common cylindrical spring and their merits compared to a common spring have been demonstrated. Next, a fairly accurate analytical formulation (with maximum error of ∼7–8%) for obtaining the value and location of maximum shear stress for all the springs has been demonstrated. Next, two aspects of non-prismatic springs under dynamic loads, viz. damping introduced in a vibrating system and contribution of the spring to the equivalent mass in a one dimensional vibrating spring mass system due to shape of the spring have been discussed. The last part involves an analytical formulation for the linear elastic buckling of two springs with circular coil shapes. For the majority of the work, emphasis has been on obtaining and using closed form analytical expressions for different quantities while numerical techniques such as FEA have been used for validation of the same. Highlights Analytical formulations of axial deflection different springs under axial load. CAD modeling and FEA of prismatic and non prismatic springs of different coil shapes. Comparison of stress and deflection in mass-equivalent springs of different geometry. Approx. analytical formulation for the location and value of max. stress in springs. Effects of spring shape on damping, vibrational properties in 1D systems and buckling.

Tribo-mechanical properties of pure thermoplastic polyurethane and functionalized monolayer graphene-reinforced thermoplastic polyurethane polymer nanocomposites are investigated by molecular dynamics simulations. Initially, the mechanical properties of the thermoplastic polyurethane and functionalized monolayer graphene-reinforced thermoplastic polyurethane nanocomposites are measured by applying constant stain method. Subsequently, interfacial layer models are developed to apply confined shear on the iron layers to find out the coefficient of friction and the abrasion rate of pure thermoplastic polyurethane and functionalized monolayer graphene-reinforced thermoplastic polyurethane nanocomposites. The results imply that by the incorporation of 0.5 wt.% functionalized monolayer, graphene shows the increase of 20% in Young’s modulus, 15% in shear modulus and 6.66% in bulk modulus of pure thermoplastic polyurethane, respectively, which are in good agreement with the previous experimental studies. Maximum enhancement of mechanical properties can be obtained up to 3 wt.% addition of functionalized monolayer graphene addition in thermoplastic polyurethane matrix. Further, it is observed that 3 wt.% of functionalized monolayer graphene-reinforced thermoplastic polyurethane nanocomposite results in minimum coefficient of friction (0.42) and abrasion rate (19%) under constant normal load (5 kcal/mol/Å) and maximum sliding velocity (11 m/s). However, further reduction in minimum values of coefficient of friction and abrasion rate at 3 wt.% of functionalized monolayer graphene-reinforced thermoplastic polyurethane nanocomposites is seen under the minimum sliding velocity (1 m/s) considered with the same normal load condition. Finally, the inherent mechanisms for enhancement of tribo-mechanical properties in functionalized monolayer graphene-reinforced thermoplastic polyurethane nanocomposites are analysed by the atomic density profile, free volume and Connolly surface at the atomic level.

Immersion type ultrasonic C-scan has been performed on Twaron-epoxy (T-E) and Twaron-polypropylene (T-PP) composite laminates impacted by 7.62 mm armor piercing (AP) projectile with different striking velocities to assess the bullet inflicted damage area. Square zones of size 72 mm by 72 mm around each impact area are subjected ultrasonic C-scan in pulse echo mode. Ultrasonic features are extracted and processed to estimate the damage area in the laminates due to each impact. The variation in internal damage area is correlated with ballistic properties of composite laminates. It is observed that in the similar range of impact velocity, the damage area is invariably higher in composites made from thermoplastic polypropylene (PP) resin compared to the thermoset epoxy resin. The internal damage area of impacted panel is found to decrease with increase in impact velocity for both the types of resin matrix which corroborated the trend in experimental ballistic curve. The internal damage area, however, increases substantially when shot lodging takes place inside the laminate below ballistic limit or upon excessive yawing.