Geeta Agnihotri

Optimization of Cutting Conditions in Milling Process to Minimize Tool Wear Using Selected Soft Computing Techniques: A Comparative Study

The life of a tool is very significant in metal cutting because production time is a waste whenever a tool is replaced or reset. Because of prolonged use, cutting tools blunt and their effectiveness decreases over time. It is necessary to replace, index or resharpen, and reset the tool after certain time. Tool life is a measure of the length of time a tool will cut effectively. The life of a cutting tool is mostly affected by many factors, such as, the tool wear, material removal rate, microstructure of the material being cut, setup rigidity, and cutting fluid quality. In this paper, up-milling and down-milling are compared with respect to different input parameters mainly cutting speed, feed, and number of teeth, rake angle, and helix angle. A relationship between tool wear and these input parameters is established by using regression analysis and soft computing techniques are applied to minimize the tool wear. Five selected soft computing techniques viz. (i) Genetic Algorithm (GA), (ii) Simulated Annealing (SA), (iii) Hybrid GA with Pattern Search (PS), (iv) Particle Swarm Optimization (PSO), and (v) Threshold Acceptance Algorithm (TAA), are used for optimization of tool wear. The results obtained from each of them are also analyzed. The effect of input parameters on tool wear, the way it is different for up-milling and down-milling is addressed for each case with the help of five selected soft computing techniques. The results indicate that the tool wear is least in case of down-milling when compared to up-milling and hybrid GA gave the best results.

Circumvention of Friction-Induced Stick-Slip Vibration by Modeling and Simulation

Present works deal with the insight into the friction-induced stick-slip vibration which takes place by virtue of the difference in the values of static and kinetic friction between the rubbing surfaces, which causes decrease in friction force with velocity. The produced intermittent motion is objectionable as it is the cause of serious nuisance, power loss, quadrant glitch, limit cycle, inaccuracy in control, etc. A comprehensive description of this phenomenon by capturing the effect of influencing parameter has become challenging research task for system dynamics especially for control. In present work, the motion of mass on rough surface, being dragged at constant velocity, is studied by stiction model. In this research work, it has been tried to capture the effect of influencing parameters to define the acceptable and optimum criteria of selecting them to ensure motion without stick slip. The study is performed by varying relevant parameters like coefficient of friction, viscous damping, driving velocity, ratio of static friction to kinetic friction. The outcome of this study is the range of these parameters and their combinations, for which friction-induced disturbances are the minimum. The results obtained in this work may be used as a generalized guide line for reducing and avoiding these disturbances.

Modeling and Simulation of the Dynamic Response of a Generic Mechanical Linkage for Control Application Under the Consideration of Nonlinearities Imposed by Friction

The present work deals with the dynamics of a generic mechanical linkage that is an integral part of many mechanical systems which require manual or automated control. It is necessary to include the dynamics of the control linkage in the model while modeling a system with such control for obtaining realistic dynamic behavior of the overall system. A typical application of the control linkages is to move an inertia element in a controlled manner, while keeping the motion as smooth as possible. Presence of inertia and elasticity in the form of a spring makes such system a second-order system, with a tendency to undergo oscillatory motion during such controlled motion. Presence of friction further introduces irregularities and nonlinearities in the motion of the target inertia element. Under these conditions, the trajectory of the controlling force has to be optimized to achieve smooth controlled motion. The present paper deals with these issues, by using a pedal-operated lever arrangement used in applications requiring controlled release or controlled engagement in mechanical systems. The computer tool used for simulation is MATLAB. The dynamic behavior of the system is assessed on the basis of total settling time of the target mass, computation time, time period of oscillation of the target mass, maximum amplitude, and amplitude decay. The present study can be useful in design of actuators and mechatronic systems involving similar dynamics.

Development and Characterization of the Midrib ofCoconut Palm Leaf Reinforced Polyester Composite

In this paper, midrib of coconut palm leaves (MCL) was investigated for the purpose of development of natural fiber reinforced polymer matrix composites. A new natural fiber composite as MCL/polyester is developed by the hand lay-up method, and the material and mechanical properties of the fiber, matrix and composite materials were evaluated. The effect of fiber content on the tensile, flexural, impact, compressive strength and heat distortion temperature (HDT) was investigated. It was found that the MCL fiber had the maximum tensile strength, tensile modulus flexural strength, flexural modulus and Izod impact strength of 177.5MPa, 14.85GPa, 316.04MPa and 23.54GPa, 8.23KJ/m2 respectively. Reinforcement of MCL enhanced the mechanical properties of pure polyester, including that of tensile strength (by 26%), tensile modulus (by 356%), flexural strength (by 41.81%), flexural modulus (by 169%) and Izod impact strength (by 23 times), but the compressive strength was adversely affected. HDT decreased due to fiber loading, but increased with weight fraction of fiber content. Moreover, the experimental results were compared with theoretical model (Rule of mixture) and other natural fiber /polyester composites.