Selection of Optimal Hot Extrusion Process Parameters for AA6061-Fly Ash Composites: Using Simulation

Selection of Optimal Hot Extrusion Process Parameters for AA6061-Fly Ash Composites: Using Simulation

Sarojini Jajimoggala (GITAM University, Visakhapatnam, India)
DOI: 10.4018/IJMFMP.2018010104
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Abstract

The simulation of hot extrusion process is a challenging problem in process modeling because of very large deformations, strain rates and temperature changes during the process. The process development in industrial extrusion is to a maximum extent based on trial and error and often involves full size experiments. Numerical simulations can replace most of these experiments, which are often both time consuming and expensive. Hence in the present work, attempt has been made to simulate hot extrusion process. AA6061-flyash Metal Matrix Composite(MMC) as billet, H13 tool steel as the die, 400oC as billet temperature and extrusion ratio of 25:4 are used as simulation parameters. Simulation is performed using software DEFORM 3D by varying ram speed, Cone Half Angle (CHA) and friction coefficient with extrusion load. The effects of change of process parameters were observed and optimal process parameters were selected.
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1. Introduction

The importance of modelling and simulation in the metal-forming industry has increased heavily during the last few decades. Process simulation is now accepted as an important tool for product and process development. Unfortunately, the introduction of computer simulation in extrusion technology has not been as fast as in other parts of the manufacturing industry. This is mainly due to particular difficulties in these simulations. Extrusion processes are associated with large deformations, high strain rates and complex contact conditions. Today, the process development in industrial extrusion is to a great extent based on trial and error and often involves full size experiments. Numerical simulations can most likely replace many of these experiments, which are often both expensive and time consuming. Computer simulations can be used to get a better understanding of the mechanisms involved in the extrusion process and improve the quality of the extruded product. The principal use of analytical study of metalworking process is for determining the forces required to produce a given deformation for a certain geometry prescribed by the process and is the ability to make an accurate prediction of the stress, strain, and velocity at every point in the deformed region of the work piece. Since the calculation are useful for selecting or designing the equipment to do a particular job.

Halvorsen et al. (2006) used Lagrangian FEM software, MSC Super Form to study the buckling of extruded flat sections. Lof et al. (2002) proposed a simulation method for the extrusion of complex profiles. They modeled bearing area with an equivalent bearing model to describe the resistance in the bearing without using a more number of elements. Gang et al. (2008) performed 3D computer simulations to determine the effects of ram speed and billet temperature on and peak extrusion pressure and temperature, thereby provided guidelines for the process optimization and minimization of the number of trial extrusion runs needed for the process optimization. Chanda et al. (2001) investigated the effect of process parameters iso-speed and step wise ram speed on extrusion pressure, the thermal response of the work piece and stress state of round bar using computer simulation. Chanda et al. (2000) performed 3D FEM simulation for the aluminium extrusion and determined stress, strain and the temperature of the alloy going through square and round dies. Bouzakis et al. (2008) simulated the flow of wet ground clay ram extrusion device and by a FEM-based model, considering the von Mises criterion for the flow stress, the associative flow rule and the rigid–viscoplastic constitutive equation. Peng et al. (2004) used FORGE3, FEM code to study the effect of number and the distribution of die holes on extrusion parameters. Duana et al. (2004) explored the complicated interactions between die design, forming parameters and the extrudate shape, surface condition and microstructure by the use of FEM. The various models have been integrated into the commercial codes, FORGE2 and FORGE3, through user routines. They found that the use of an expansion chamber can significantly reduce the degree of non-uniformity in terms of the extruded product shape and properties. The character of the complex material flow is also identifiable, which is very useful to help improve die design. Lee et al. (2002) studied the effect of bearing lengths for the control of material flow in the die in hot extrusion. Laue et al. (n.d.) investigated considerable differences in flow behavior during the process by varying method of extrusion, material and lubrication.

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