Application of Response Surface Methodology to Predict Ovality of AA6082 Flow Formed Tubes

Application of Response Surface Methodology to Predict Ovality of AA6082 Flow Formed Tubes

M. Srinivasulu (Faculty in Mech. Engg., Department of Technical Education, A.P.,and Part-Time Research Scholar, JNTUH, Hyderabad, India), M. Komaraiah (Sreenidhi Institute of Science and Technology, Hyderabad, A.P., India) and C.S. Krishna Prasada Rao (Bharat Dynamics Limited, Hyderabad, A.P., India)
DOI: 10.4018/ijmmme.2013010104
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Flow-forming is eco-friendly, chipless manufacturing process employed in the manufacture of thin walled seamless tubes. Ovality, the out of roundness is one of basic form of errors encountered in the tubular components. In the present research, a response surface model has been developed to predict ovality of AA6082 alloy pre-forms using Design of Experiments. The experiments are performed on a flow forming machine with a single roller. The process parameters selected for the present investigation are axial feed of the roller, the speed of the mandrel, and roller radius. Box-Behnken Design, a standard response surface methodology has been used to conduct the experimental runs. The developed response surface model successfully predicts the ovality of AA6082 flow formed tube within the range of selected process parameters. It has been found that, roller feed is the most important process parameter influencing the ovality of AA6082 flow formed tube.
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1. Introduction

Flow-forming is modern, chipless metal forming process which employs an incremental rotary point deformation technique. In flow-forming the length of pre-form is elongated at the reduction in wall thickness without changing the internal diameter. Flow-forming is used in the production of seamless tubes, cylinders, axi-symmetric sheet metal parts for high strength-to-weight ratio flanged components used in automobile, ship building, aerospace and defense applications etc. The roundness error (Ovality) is one of the most important for error encountered in the production of thin walled tubes for aerospace, defense, missile, transportation and other applications. Various process parameters namely roller feed, mandrel speed, roller radius, thickness reduction, roller attack angle influence the ovality of flow formed tube.

Rajanish and Singhal (1995) employed spinning technology to manufacture smaller diameter, thin walled long tubes. They studied effect of roller feed, roller profile and thickness reduction on the surface roughness on forming of AISI-304. Chang et al. (1998) investigated the tube spinnability of AA2024 and 7075 alloys at full-annealed and solution-treated condition. Yao Jianguo et al. (2002) studied the effect of roller feed on spinning force, thickness strain and accuracy on spinning of Aluminum tube (AA1050). Rajan et al. (2002) conducted experiments to know the effect of heat treatment of perform on the mechanical properties of flow formed AISI 4130 steel tubes. Lee and Lu (2001) investigated the effect of deformation ratio and friction on the drawing force during flow forming of lead cylindrical tubes. Padmanabhan et al. (2007) conducted experiments to determine the influence of input parameters on the deep drawing of stainless steel. Lakshman Rao et al. (2009) studied the influence of roller attack angle on the surface finish and ovality of flow formed Copper tubes. Joseph Davidson et al. (2008) used Taguchi approach o optimize the process parameters for maximum deformation on flow forming of AA6061 tubes. Srinivasulu et al. (2011) investigated the influence of process parameters on surface roughness of AA 6082 flow formed tubes by Taguchi method.

But, very little work has been reported on flow forming of AA6082 tubes. The ovality is one of the important characteristic of flow formed tube. Error free flow formed tubes combined with minimum ovality are desired for critical aerospace, missile, automobile and other applications.

Gunaraj and Murugan (1999) predicted weld bead quality in submerged arc welding of carbon steel pipes using response surface methodology. Dhavlikar et al. (2003) applied Taguchi and dual response methods to determine optimal combination of parameters to minimize the roundness error in centerless grinding process Noordin et al. (2004) employed response surface methodology to describe the performance of coated carbide tools in turning operation of AISI 1045 steel. Jac-soeb Kwak (2005) used combined Taguchi and response surface methodology to predict geometric error in surface grinding process. Joseph Davidson et al. (2008) developed regression model based on response surface methodology to predict surface roughness of AA6061 flow formed tubes.

From the literature review it is revealed that, no work has been reported on response surface model for ovality of AA6082 thin walled tubes by flow forming process.

The aim of present work is to generate the response surface model to predict the ovality of AA6082 thin walled tubes manufactured by flow forming process. The input process parameters chosen are axial feed of the roller, speed of the mandrel and roller radius.

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