Dr. Ajith Ramesh

Abstract: In the presented work, Numerical modeling of cold rolling process and Multi objective optimization of rolling parameters were performed. Average rolling force, Average rolling torque, Load carrying capacity and Max. compressive residual stress were considered as response parameters. Roller dia., Roller Speed and Percentage reduction were considered as design parameters. The developed numerical model was validated using the experimental results obtained from the previously published literature S. Ghosh et al. Novel methods were used to measure Load carrying capacity and Maximum compressive residual stress. Analysis of Variance (ANOVA) was performed for all the response parameters. The optimum values of the design parameters are found using Response Surface Methodology (RSM). It was found that, the percentage reduction has significant influence on all response parameters.

Wind energy being one of the renewable energy sources, having potential to substitute power generation from fossil fuels, has always drawn the spot light of research society. Non-straight bladed vertical axis wind turbine (VAWT) has proven to be one among the better options among small scale turbines. The presented work investigates the effect of wind speed on the performance of a Troposkien blade VAWT using 3D CFD simulations. The transitional SST K-w model is used for modeling turbulence. Simulations are conducted for varying wind velocities (6 m/s - 14 m/s) and varying tip speed ratios (TSR) (1.6 - 2.1). Based on the swept area of the turbine, the mean radius of the turbine is calculated which serves as the basis for the calculation of TSR. The results obtained indicate that the turbine performance is significantly affected at lower TSR at varying wind speeds, and the percentage of change is much lower at higher TSR values. Peak performance of the turbine is noted at the same TSR value for all wind velocities, and the magnitude of coefficient of performance is found to be almost the same.

There is a requirement to find accurate parameters to accomplish precise dimensional accuracy, excellent surface integrity and maximum MRR. This work studies the influence of various cutting parameters on output parameters like Cutting force, Surface roughness, Flatness, and Material removal rate while face milling. A detailed finite element model was developed to simulate the face milling process. The material constitutive behavior is described by Johnson-Cook material model and the damage criteria is established by Johnson-Cook damage model. The result indicate significant effects of all three cutting parameters on MRR and both feed rate and depth of cut have significant effect on cutting force. Also, feed rate has significant effect on PEEQ and none of the parameters have effect on flatness. © 2019 by the authors.

Flow forming is an incremental forming process used for making long, thin-walled seamless tubes with high strength and dimensional accuracy. This is carried out by compressing the pre-formed tube using one or more rollers, leading to the plastic flow of material in the radial, axial, and tangential directions. This ultimately results in reduction in thickness and elongation of the tube. In order to achieve the required accuracy and to reduce the shop floor costs, a better understanding of the influence of process parameters on part geometry, deformation mechanism, and stress-strain patterns will be required. This paper describes the development of a detailed finite element model, using Abaqus/Explicit, to accurately simulate the flow forming process for AISI-1045 MC-Steel, and attempts to predict the influence of process parameters like axial stagger, feed ratio, and percentage reduction, on output parameters like ovality, diametral growth, and spring back. The effect of multi-pass on surface finish is also investigated.

A FEM simulation study was carried out to investigate the influence of the rolling parameters on the rolling process. Using commercial FEM software, ABAQUS, a number of cases were studied. In this paper, a two-dimensional Elastic-plastic finite element model to simulate the cold rolling of thick strip with different roll angular velocity and roll diameter models is described. The angular velocity of the rigid rolls ranged from 30 to 480 revolutions per minute (r.p.m.) and the rigid roll diameter ranged from 100 to 300 mm. The initial feeding speed of the plate and friction was kept constant, thus causing a slip between the plate and the roll surfaces. The main interest of this study is to see whether the speed of the rolls and the diameter of the rolls have any influence on the contact pressure and the residual stress in cold rolling process. The roll speed is an easily controlled operational parameter which may be used to enhance the process and the quality of the final products by changing the roller diameter and see the effect of stress and contact pressure on the thick plates strip is new one.

In this paper, finite element simulations of spherical indentation of Nickel thin film on Steel-4340 are studied for single and multiple cycle of indentation as well. The objective was to understand the mechanics of coated systems, from load-displacement (P-h) curves, stress distribution in the film and the effect of substrate yield strength on the indentation response. The loading portion of P-h curve showed displacement bursts and the reason for this is investigated. A transition in the deformation behavior of the film from Hertz-type to flexure was observed for a normalized indentation depth of h/tf≈0.2. The influence of coating-substrate properties on P-h curve is also investigated for different h/tf ratios and yield strains. Attempts are also made to explore the possibility of understanding the creep-fatigue behavior of coated specimen subjected to cyclic indentation at room temperature from Indentation depth v/s time, Indentation depth v/s number of cycles and Plastic dissipation energy v/s number of cycles curve.

Hydroforming is a manufacturing process that is used to form complex geometries by applying fluid pressure. The punchless hydroforming process is the most popular in the race, considering the absence of any punch that helps in reducing the tooling costs. Based on the part geometries formed, the punchless process can be classified into three categories, namely sheet hydroforming, shell hydroforming and tube hydroforming. Sheet metal hydroforming is a hydroforming process that uses hydrostatic fluid pressure for deforming the blank into a die cavity of the desired shape. Owing to the inert advantages, like lower tooling costs, reduced processing steps, remarkable precision, waste reduction and weight reduction, this process finds extensive use in applications requiring a high strength-to-weight ratio, as in complex automobile parts. The presented work involves the development of a nonlinear 2D finite element model for the sheet hydroforming process of AA5182 (aluminium alloy) using the FE package Abaqus/Explicit and validation of the numerical results using the available literature (Daryl in Logan: a first course in the finite element method. Cengage Learning Products, Canada 2007 [2]). The model is first validated by reproducing the research work carried out by Bharatkumar Modi et al., considering the input parameters, like blank holding force (BHF), sheet thickness and internal pressure, and the corresponding output parameters, like material thickness reduction and die corner radius. The research is further extended by replacing the current blank material AA5182 using cryo-rolled AA5083. The effect of varying BHF, at varying annealing temperature of blank considering varying frictional coefficients, is also studied. This work also investigates the optimisation of the process using a well-established design of experiments (DOE) technique–-response surface methodology (RSM).

In this paper, finite element simulations of spherical indentation of Nickel thin film on Steel-4340 are studied for single and multiple cycle of indentation as well. The objective was to understand the mechanics of coated systems, from load-displacement (P-h) curves, stress distribution in the film and the effect of substrate yield strength on the indentation response. The loading portion of P-h curve showed displacement bursts and the reason for this is investigated. A transition in the deformation behavior of the film from Hertz-type to flexure was observed for a normalized indentation depth of h/tf ≈0.2. The influence of coating–substrate properties on P-h curve is also investigated for different h/tf ratios and yield strains. Attempts are also made to explore the possibility of understanding the creep-fatigue behavior of coated specimen subjected to cyclic indentation at room temperature from Indentation depth v/s time, Indentation depth v/s number of cycles and Plastic dissipation energy v/s number of cycles curve.

This dissertation presents a detailed model of the ‘overall’ behavior of Torsional springs. Torsional springs (also called ‘Clock’ springs) are a kind of spiral springs which are supposed to provide a certain torque when wound-up to a certain rotation. However, it is observed that the moments that are developed relax when the springs are kept loaded over long periods of time. The research presented here is an attempt to investigate this behavior by identifying the role played by the various influencing parameters.

The dissertation focuses on the development of a detailed component-level finite element model to investigate the instantaneous moment-rotation response as well as the long-term (time-dependant) structural response of a torsional spring. Torsional springs belong to a class of planar spiral springs that are commonly made out of Elgiloy - an alloy of Cobalt, Chromium, Nickel, and Iron. Elgiloy has very high yield strength, and is commonly used as a spring material in analog clocks. In addition, the research also aims at developing a better understanding of the dependence of the response of the spring on the different design parameters that define its geometry and material properties. Frictional contact, large deformations, and nonlinear material behavior (plasticity and creep) are among the major challenges that need to be resolved in order to obtain a thorough understanding of the problem. The modeling effort also focuses on understanding the experimentally-observed hysteresis associated with a cyclic moment versus rotation response, as well as the development of simple analytical models which can approximately describe the structural response of a typical torsional spring.